geographic sharing in c-band

Geographic Sharing in C-band

Final Report

Transfinite Systems Ltd Tel: +44 (0) 20 8240 6648 6C Rathbone Square Fax: +44 (0) 20 8240 4440 24 Tanfield Road Email: [email protected] Croydon CR0 1BT Web: www.transfinite.com


Documentation Control

Project: Geographic Sharing in C-band

Reference: MC/339

Authors: Transfinite Systems Ltd

Date: 31st May 2015

Status Final

Version: 1.6

Version History:

1.2 First release

1.3 Updated with editorial changes

1.4

1.5

Updated with editorial changes

Updated with editorial changes

1.6 Updated with editorial changes

This report was commissioned by Ofcom to provide an independent view into geographic sharing in C-band (3.6 to 4.2 GHz). The assumptions, conclusions and recommendations expressed in this report are entirely those of the consultants and should not be attributed to Ofcom.

The International System of Units is used throughout unless otherwise specified and all maps are orientated with north towards the top.


Brief Table of Contents

1 Executive Summary ..........................................................................................................6

2 Introduction and Background ........................................................................................15

3 Assignment Data and Modelling Parameters ................................................................17

4 Summary Of UK Spectrum Availability .........................................................................23

5 Interference Zone Analysis ............................................................................................39

6 Adjacent Channel Interference Issues ...........................................................................49

7 Summary Of High Resolution Detailed Analysis ..........................................................55

8 Mitigations ......................................................................................................................66

9 Conclusions and Recommendations ..............................................................................77

10 Annex: Fixed Links Interference Zone Analysis ..........................................................85

11 Annex: NFD and Spectrum Masks ................................................................................87

12 Annex: High Resolution Analysis ..................................................................................89

13 Annex: National Maps – Full Set of Data ...................................................................134

14 Annex: Acronyms and Abbreviations ..........................................................................177

15 Input Data .....................................................................................................................178


Full Table of Contents

1 Executive Summary ..........................................................................................................6

1.1 Work Undertaken .....................................................................................................6

1.2 Key Findings ..............................................................................................................7

1.3 Recommendations for Additional Study ...............................................................13

1.4 Document Structure ................................................................................................14

2 Introduction and Background ........................................................................................15

2.1 Purpose and Scope ..................................................................................................15

2.2 International Background ......................................................................................16

3 Assignment Data and Modelling Parameters ................................................................17

3.1 Protection Criteria ..................................................................................................17

3.2 Baseline IMT Parameters .......................................................................................19

3.3 Satellite Earth Station Data ...................................................................................21

3.4 Fixed Link Data .......................................................................................................21

3.5 Geotype Data ...........................................................................................................21

4 Summary Of UK Spectrum Availability .........................................................................23

4.1 Methodology ............................................................................................................23

4.2 Available Spectrum .................................................................................................26

4.3 Separate Analysis of Satellite Earth Stations and Fixed Links ...........................37

4.4 Conclusions ..............................................................................................................38

5 Interference Zone Analysis ............................................................................................39

5.1 Satellite Earth Station Interference Zone Analysis ..............................................39

5.2 Fixed Links Interference Zone Analysis ...............................................................45

6 Adjacent Channel Interference Issues ...........................................................................49

6.1 Adjacent Channel Interference into Fixed Links .................................................49

6.2 NFD Calculations for Satellite Earth Station and IMT Interference .................53

6.3 Notes and Conclusions on NFD and ACI ..............................................................54

7 Summary Of High Resolution Detailed Analysis ..........................................................55

7.1 Overview ..................................................................................................................55

7.2 Factors Specific to the High Resolution Analysis .................................................55

7.3 Earth Station Test Case ..........................................................................................59

7.4 BT Tower Test Case ................................................................................................62

7.5 Power and Traffic ...................................................................................................64


7.6 Conclusions from High Resolution Detailed Analysis .........................................65

8 Mitigations ......................................................................................................................66

8.1 Mobile Network Based Mitigation .........................................................................66

8.2 Earth Station Mitigation ........................................................................................71

8.3 Fixed Link Based Mitigation ..................................................................................72

8.4 Interference Constraints in Mobile Licence .........................................................73

8.5 Frequency or Geographic Migration ....................................................................73

9 Conclusions and Recommendations ..............................................................................77

9.1 Conclusions ..............................................................................................................77

9.2 Recommendations ...................................................................................................81

10 Annex: Fixed Links Interference Zone Analysis ..........................................................85

10.1 Single-Entry Interference .......................................................................................85

10.2 Transmitter Power ..................................................................................................85

10.3 Receiver Interference Threshold ...........................................................................85

10.4 Antennas ..................................................................................................................86

11 Annex: NFD and Spectrum Masks ................................................................................87

11.1 Net Filter Discrimination ........................................................................................87

11.2 Spectrum Masks ......................................................................................................87

12 Annex: High Resolution Analysis ..................................................................................89

12.1 Overview ..................................................................................................................89

12.2 Propagation and Surface Data ...............................................................................89

12.3 Earth Station VSAT Test Case ..............................................................................96

12.4 BT Tower Test Case ..............................................................................................114

12.5 Power and Traffic .................................................................................................128

12.6 Conclusions ............................................................................................................132

13 Annex: National Maps – Full Set of Data ...................................................................134

13.1 Sharing with Satellite Earth Stations and Fixed Links Combined ...................134

13.2 Sharing with Satellite Earth Stations only ..........................................................150

13.3 Sharing with Fixed Links Only ............................................................................161

14 Annex: Acronyms and Abbreviations ..........................................................................177

15 Input Data .....................................................................................................................178


1 EXECUTIVE SUMMARY This is the Final Report of a study by Transfinite Systems into geographic sharing in C-band (3.6 GHz to 4.2 GHz).

The study aimed to give an assessment of the potential to share spectrum at C-band between incumbent users (fixed links and satellite Earth stations) and new mobile services, in particular IMT-A.

1.1 Work Undertaken

The following bullets outline the work undertaken.

We reviewed studies within the ITU-R JTG 4-5-6-7 to select suitable parameters to use in sharing analysis.

We analysed licensing data provided by Ofcom for point to point fixed links and satellite Earth stations.

Licensing data were imported into our standard Visualyse simulation tool and into an optimised version customised to handle the production of UK-wide maps of available spectrum.

A calculation methodology for assessing whether a specific location is suitable for sharing between mobile networks and incumbent services was defined.

We undertook three levels of analysis:

o Spectrum Availability Analysis, maps and statistics of UK wide availability of spectrum categorised by geo-type, using a 5 MHz channel raster and 1 square kilometre pixelation. This is based on the total spectrum available net of the allocation to UK Broadband – a total of 430 MHz. This analysis is described and summarised in Section 4 and the full set of results given in Section 13.

o Interference Zone Analysis, which used terrain and land use databases to identify the area around selected fixed links and satellite Earth stations where deployment of mobile networks could cause interference. This analysis is described in Section 5.

o High Resolution Analysis, which used a high-resolution surface database to examine, in detail, a scenario in which fixed links or satellite Earth stations were located in the types of dense urban areas likely to be the key locations for mobile small cell deployment. This analysis is described in Section 7.

We investigated options for mitigation including accounting for network traffic variabililty, selecting locations to deploy mobile network base stations, use of larger dish antenna by the fixed links or satellite Earth stations and directional antennas at base stations. A combination of mitigation techniques would provide extra margin in the I/N calculations. There are multiple possible combinations, and these run variations are set out in Section 4.1.1.The potential impact of these mitigations on sharing scenarios was assessed in a general way as discussed in Section 4.2.4.


The analysis concentrates on the scenario where the IMT-A system in these bands is used for capacity enhancement in areas of higher population density. This in turn means we have modelled indoor and outdoor small cells and, where results are related to population numbers, these have been deployed in urban, dense urban and hotspot areas (see Section 3.5 for discussion of this).

Other variants of IMT-A deployments have different parameters and could be deployed in rural areas. The potential for sharing for this type of system has not be addressed in this report.

1.2 Key Findings

The principal conclusion is that there is scope for sharing spectrum in this band. The reason we believe this is that, as Figure 1-1 shows, even in the baseline case, 80% of the 3.6 - 4.2 GHz spectrum band is available to 50% of the urban+ population (urban+ means areas that are classified as urban, dense urban or hotspot as discussed in Section 3.5) . This represents a massive potential economic value.

Half the existing spectrum is available to 65% of the urban+ population, and this increases to around 90% if 20 dB of mitigation is applied.

On the other hand, even on the application of 20 dB of mitigation, potential interference cannot be ruled out in some populous areas.

Whether 20 dB mitigation is possible in all cases is not clear, but our simulations indicate that improved modelling based on higher resolution surface data could, in most cases, result in an additional 10 dB (see Section 12.2.3 and 12.2.4.). The additional loss due to more accurate modelling depends on the details of the local environment, 10 dB is a conservative figure for the cases we have studied and for a built-up environment.

The implication is that a managed approach to shared access of the band based on geographic sharing has great merit. Spectrum is available but the possibility of interference remains in some locations under all assumptions.

We find little difference between the whole frequency range and a separate analysis of 3.6 - 3.8 GHz and 3.8 - 4.2 GHz.

The constraint on operation of mobile in C-band is dominated by the need to protect fixed links. Protection of satellite Earth stations is much less constraining. Fixed links in general present a more difficult geometry (See Figure 1-4) and, in addition, some fixed links are deployed across urban areas. In particular, we see that the fixed links across central London cover large, densely populated areas, hence potential deny use of the spectrum to a large number of mobile users. Some Earth stations may also experience interference from large areas, but, generally speaking, these Earth stations are in less populated areas, and the impact is consequentially lower.

1.2.1 Baseline Spectrum Available

The primary numerical result is the amount of spectrum available in areas of high population density, for example in hotspots, urban and dense urban areas (accounting for 17.41 million people in our model). We have concentrated on areas of high population density where small cells are more likely to be deployed. The definition of population geotypes is discussed in Section 4.1.2.


Figure 1-1 shows a cumulative distribution function (CDF) of the availability of spectrum across the UK by percentage of population in urban, dense urban and hotspot areas.

Figure 1-2 shows a colour coded representation of the availability of spectrum across the UK as a whole.

Figure 1-1: Availability of Spectrum in MHz by Percentage of Urban+ Population under

Baseline Assumptions


Figure 1-2: Colour Coded Map of Spectrum Available in Sharing with Satellite

Earth Stations and Fixed Links in 3.6 - 4.2 GHz

1.2.2 Effect of Mitigation

Detailed analysis presented in Section 7 shows that various mitigations can be applied in many cases. There are lots of combinations of mitigation that


could be applied, and for each mitigation technique the additional margin that results is variable (dependent on assumptions and detailed modelling).

One way to assess the affects of mitigation is to relax the I/N threshold by a fixed value and look at the effect on spectrum availability. In our analysis we have looked at 5, 10 and 20 dB relaxations, Figure 1-3 shows the spectrum available when 5, 10 and 20 dB of mitigation is applied to the baseline case.

Figure 1-3: Availability of Spectrum in MHz by Percentage of urban+ Population under

Baseline Assumptions and with 5, 10 and 20 dB Mitigations Applied

An overview of the effect of mitigation can be seen in Figure 1-4 below.

The interpretation of colour-coded maps is discussed in detail in Section 4.1.2. In the case shown below, areas coloured blue-green have over 50% of the spectrum in the band available. The picture improves significantly from the baseline case to the case where 20 dB mitigation is applied, 80% of the population have access to around 295 MHz of spectrum compared to 60 MHz. Even so, sharing does not become a trivial issue, 10% of the population would have access to less than 50% of the spectrum and sharing would still need to be managed.


Baseline Case 5 dB Relaxation

10 dB Relaxation 20 dB Relaxation

Figure 1-4: The Available Spectrum in London area in the Baseline Case and with 5, 10

and 20 dB of Mitigation, in 3.6 - 4.2 GHz Sharing with all Satellite Earth Stations and

Fixed Link Carriers

More detail on the available spectrum is given in Section 4 and the full background findings are in Section 13.

1.2.3 Other Findings

Other key findings of the project are:


Sharing with fixed links is harder than with satellite Earth stations because of the geometry involved, as shown in Figure 1-5.

Figure 1-5: Comparison of Earth Station vs. Fixed Link Geometry

The operation of mobile network base stations in channels adjacent to fixed link and Earth station receivers is possible with minimal constraints as there is significant net filter discrimination (NFD). However, the potential for adjacent channel interference cannot be wholly ignored in exploring the potential to share the spectrum.

The spectrum availability maps produced in this study are likely to be conservative. High-resolution analysis suggests that there is the potential to operate mobile services within the interference zones – with some realistic constraints on deployment and taking into account the local built environment.

Mitigations available include the use of directional antennas at the mobile network base station and pointing away from the fixed link or Earth station receiver. This reduces interference relative to the omni-directional antenna assumed for ITU-R JTG Studies.

The methodology used to calculate the average EIRP of the mobile network base station was identified as being conservative. It did not take account of the variation in traffic levels during the day. This could reduce interference by 2.3 dB.

The methodology used by the ITU-R JTG to assess clutter loss using the model in Recommendation ITU-R P.452 produces conservative results compared to using a surface database and diffraction. This is particularly important given that mobile network base stations are likely to be deployed in dense urban+ areas below building height.

Earth Station

Base Station

Higher diffraction +

increased relative gain

Lower diffraction

and decreased

relative gain

Earth Station

Elevation > 0

Fixed Link

Elevation < 0

Fixed Link

Receiver


In addition, with mobile network base stations deployed below building height there could be significant antenna discrimination for a radio path heading over buildings at high elevation angles. (see Figure 7-3, for an illustration of the direct path vs the radio path in urban environments)

The size of the interference zone could be reduced by employing mitigations at the Earth station such as using a larger antenna or site shielding. It was in general harder to use such mitigations for fixed link receivers.

Even with the use of mitigations, there would be some geometries where it would not be feasible to deploy mobile network base stations. In particular, it would be problematic to deploy on streets orientated along azimuths that point directly at fixed link receiver or Earth station receivers, as there would be no clutter loss in that direction.

1.3 Recommendations for Additional Study

This project has highlighted areas that could potentially improve the situation further and would benefit from further study, including:

Short Term Thresholds: The analyses were run using the long-term interference criteria used by Ofcom in their frequency assignment/coordination procedures. For small cells, lower power base stations resulting in relatively small separation distances mean this is a good measure. However, for macro cells with higher power levels and greater antenna heights, larger separation distance will become more important. As a result anomalous propagation mechanisms will become significant. It would be beneficial to consider the short-term interference threshold in future analysis.

Analysis: For the UK-wide maps, it would be useful to extend the detailed analysis for more scenarios and use smaller pixels for a more detailed assessment. We have seen that this can give a different picture and that better data usually leads to improved decision making

Propagation modelling: Significant differences were noted between the local clutter loss model in P.452 and the same calculation using diffraction over local buildings. There would be significant benefits in further study, potentially including measurement of diffraction loss in dense urban areas.

Net Filter Discrimination: the NFD for the satellite Earth station case was low due to conservative assumptions about the receiver filter characteristic in the absence of real data. On the other hand using standardised spectrum masks for fixed links showed that adjacent channel interference should not be neglected. There would be benefits in studying this further.

International support: It would be useful to build international support for a more detailed approach that takes into account actual assignments and high-resolution surface databases.


Pricing: The study raised issues regarding the pricing of licences and recognised spectrum access (RSA) for assignments in this band. Given that this frequency band could be used for mobile applications, the area denied and area type (urban / dense urban) could be the basis of a revised pricing policy.

Regulatory options: One option would be to incorporate in mobile spectrum licences the need to protect existing assignments to a given I/N threshold. The implications of this could be analysed further with feedback from the operators on the operational constraints involved.

Mitigations: A number of possible mitigations were identified that would require changes to Earth station and fixed link receivers. These could be analysed further with feedback from the licence holders as to feasibility and cost.

1.4 Document Structure

This document is structured as follows:

Section 2: Introduces the project, covering its objectives, purposes and scope. There is a description of the background, in particular the ITU-R JTG 4-5-6-7 and the work undertaken is described.

Section 3: This describes assignment data and modelling parameters used in the project, including, most importantly, the protection criteria. It also describes the licensing data provided by Ofcom.

Section 4: This describes the UK-wide maps of spectrum availability including statistics by land use code and population, by band and existing licence type (fixed link or satellite Earth station).

Section 5: This section summarises the Interference Zone Analysis undertaken around selected fixed link and Earth station locations.

Section 6: Discusses technical issues relating to non co-frequency operation and how this impacts the results from Section 5.

Section 7: High Resolution Analysis, in which a 3m resolution surface database to examine in detail deployment of mobile networks, is summarised.

Section 8: This discusses possible mitigations to reduce the size of the excluded areas and hence increase the spectrum available.

Section 9: This sets out project conclusions and recommendations.

Sections 10 to 14: These annexes give the technical details of the analysis undertaken and its outputs.


2 INTRODUCTION AND BACKGROUND

2.1 Purpose and Scope

The study aimed to develop an assessment of the potential for spectrum sharing at C-band (3.6 GHz to 4.2 GHz) between incumbent users and mobile services. In the UK the frequencies are used for satellite downlinks, fixed links and 2 x 84 MHz is licensed to UK Broadband. The frequencies licensed to UK Broadband; 3605 to 3689 MHz and 3925 to 4009 MHz, were not considered in this study. The mobile services considered are those generally labelled IMT-A.

Within this range, the 3.6 - 3.8 GHz portion is considered separately from the 3.8 - 4.2 GHz portion. There is a European Decision supporting harmonised use of 3.6 - 3.8 GHz for mobile applications, and there is support within the European Conference of Postal and Telecommunications Administrations (CEPT) for a primary mobile service allocation and identification of this band for IMT.

This is in contrast to the 3.8 – 4.2 GHz band, where there is active opposition to a co-primary allocation to mobile and the band is not harmonised for mobile use.

IMT-A is a broad definition and the two main candidate implementations are capable of deploying networks with different topologies, physical characteristics and radiofrequency parameters. For sharing studies, this range of possibilities has been codified by ITU-R WP 5D into a limited set of options covering macro-cell in urban and suburban environments and small-cell indoor and outdoor deployments.

In this study, we have focussed on small cells because the C-band is considered ideal for providing additional, high capacity service to multiple users in hotspot areas and areas of dense population. (see Section 3.5 for definitions and discussion)

Small cells support this type of use in a number of ways, including deployment below building level, which means the local environment aids frequency re-use and enhances capacity.

The analysis undertaken in this study was driven by three important considerations:

It was based on a real world and practicable perspective

It was focussed on protecting incumbent users in a live band, based on UK national planning criteria

It was required to explore ways to maximise the spectrum available for mobile broadband.

Recognising also that harmonised use of spectrum brings many benefits, the study keeps in mind that the outputs are also intended to feed into discussions in Europe. With this in mind, the next section discusses the international background and summarises the current situation.


2.2 International Background

The ITU-R has studied the issue of additional spectrum for IMT services for many years. Studies have been focussed on the protection of incumbents and, although conducted using a range of inputs and assumptions, they have aimed to deliver definitive separation distances required to protect satellite Earth stations.

In general, the inputs to these studies are defined by experts associated with the incumbent services and there is little scope to challenge these. Hence, the studies are weighted in favour of the incumbents and, despite the wide range of outputs available, the ITU does not provide practical guidance to those administrations with a progressive approach to the study work and seeking opportunities for spectrum sharing.

The studies presented here address the fact that there is a large grey area and no definitive answers. Sharing is possible in some situation but not others and more data helps in informed decision making.


3 ASSIGNMENT DATA AND MODELLING PARAMETERS This section describes:

A derivation of the interference criteria we have used in the project

The parameters used by JTG studies

3.1 Protection Criteria

This study was focused on planning at a UK-wide level with an emphasis on understanding the constraints on sharing spectrum.

The protection criteria discussed here was taken from the frequency assignment and coordination procedures used by Ofcom when running:

Frequency assignment requests for microwave fixed links;

Frequency coordination procedures for satellite Earth stations.

Practical decisions have been made by Ofcom in the past that mean satellite Earth stations and fixed links are treated on equal terms in these procedures. That is, the intra-service frequency assignment criteria designed to protect a microwave fixed link receiver from excess interference sourced from another microwave link is also used to protect the receiver from excess interference sourced from an Earth station. Our use of the criteria follows this precedent and is applied to the spectrum sharing problem considered in this study.

For both Earth stations and fixed links, the protection criteria used in this study is expressed as the ratio of interfering signal power to noise denoted by I/N expressed in decibels and illustrated in Figure 3-1.

Figure 3-1: Application of Protection Criterion

The study has considered long-term interference tests only. The protection criteria used in the simulation work for both satellite Earth stations and fixed links are summarised in Table 3-1.

Service Test

Earth Station dBNI 10/ , 20% time

Fixed Link dBNI 2.12/ , 50% time

Table 3-1: Protection Criteria

Here I represents the single-entry interferer. In the Ofcom criteria, this is defined as a source of interference from one radio station on one frequency. However, in this sharing study we define single-entry interference to be the interference sourced from a single location (pixel) where the entire bandwidth of the victim receiver is populated with interferers.

N (dBW)

I (dBW)

I/N (dB)


3.1.1 Earth Stations

For the long-term interference test considered in these studies, I/N = -10 dB; here we model the interfering signal I exceeded for 20% of time. N is a calculated value using kTB (dBW) where k = -228.6 dBW/Hz/K is Boltzmann’s Constant, T is noise temperature specified by the satellite Earth station operator (source: Ofcom data) expressed in Kelvin and B is the bandwidth of the victim receiver. N varies across the Ofcom data set used in this study.

3.1.2 Fixed Links

Frequency assignment procedures for microwave fixed links are specified in Ofcom’s OfW446 Technical Frequency Assignment Criteria for Fixed Point-to-Point Radio Services with Digital Modulation1. This document sets out the Wanted-to-Unwanted ratios, denoted by W/U and used by Ofcom in its frequency assignment procedures. W/U are derived for individual radio systems. For the long-term interference test, the wanted signal is modelled fully faded (receiver sensitivity) and the unwanted signal at its median level (exceeded for 50% of time).

Figure 3-2 shows the noise-interference budget used to derive W/U for the long-term test. Here Rmed is the receiver’s median signal level, M is the fade

margin, Rref is receiver sensitivity, C/(N+I) is the carrier to noise plus

aggregate interference ratio, MI is the interference margin, N is total noise, I is the aggregate interference threshold, L + NF are fixed system losses and noise figure, I is the single entry interference threshold and kTB is the inescapable thermal noise level in the receiver’s bandwidth.

Figure 3-2: Noise-interference Budget

1 http://stakeholders.ofcom.org.uk/binaries/spectrum/spectrum-policy-area/spectrum-

management/research-guidelines-tech-info/tfac/ofw446.pdf

http://stakeholders.ofcom.org.uk/binaries/spectrum/spectrum-policy-area/spectrum-management/research-guidelines-tech-info/tfac/ofw446.pdf

http://stakeholders.ofcom.org.uk/binaries/spectrum/spectrum-policy-area/spectrum-management/research-guidelines-tech-info/tfac/ofw446.pdf


In this study, we map W/U to an I/N value on the following basis. Ofcom, employ a 1 dB interference margin in this frequency band which means that for the long-term interference test, the aggregate interference threshold is 5.9 dB below noise and, assuming four equal single-entry interferers contributing to aggregate interference, the single-entry interference threshold is 6 dB below the aggregate threshold, giving an I/N = -11.9 dB. However, we should note that the W/U are integers, rounded with a non-conservative bias and, in order to remain consistent with this practical approach, we obtain I/N = -12.2 dB for the fixed link radio system considered in this study.

An analysis of the fixed link data allows for a mapping of each fixed link in the data to the radio system 140/155 in 30 (Mbit/s in MHz). From Ofw446, this system has Rref = -97 dBW, N = 121.8 dBW and W/U = 37 dB. Therefore, Equation 3-1 is used to obtain an I/N consistent with the Ofcom criterion:

.)/(/ UWRNNI med

Equation 3-1: Calculating Protection Criterion

3.2 Baseline IMT Parameters

Our baseline parameters for the IMT base stations are given in Table 3-2, extracted from document JTG 4567- 07152 – which is the basis for a Draft New ITU-R Report.

2 See Annex 17 from the Chairman’s report of the final meeting, dated 19 August 2014 of

http://www.itu.int/en/ITU-R/study-groups/jtg4-5-6-7/Pages/default.aspx.

http://www.itu.int/en/ITU-R/study-groups/jtg4-5-6-7/Pages/default.aspx


Base station

characteristics / Cell

structure

Small cell outdoor Small cell indoor

Cell radius / Deployment

density

1-3 per urban macro cell

(<1 per suburban macro

site)

depending on indoor

coverage/capacity

demand

Antenna height 6 m 3 m

Sectorization single sector single sector

Downtilt N/A N/A

Frequency reuse 1 1

Antenna pattern Recommendation ITU-R F.1336

omni

Antenna polarization linear linear

Indoor base station

deployment

N/A 100%

Indoor base station

penetration loss

N/A 20 dB

Below rooftop base station

antenna deployment

100% N/A

Maximum base station

output power (5/10/20

MHz)

24 dBm 24 dBm


antenna gain

5 dBi 0 dBi


output power/sector

(EIRP)

29 dBm 24 dBm

Average base station

activity

50% 50%

Average base station

power/sector taking into

account activity factor

26 dBm 21 dBm

Table 3-2: Deployment Related Parameters for IMT-Advanced Systems between

3 and 6 GHz Bands

One point to note is that the maximum output power per base station is not dependent on the bandwidth. Our baseline results relate to a 10 MHz channel.

We take the reference to Recommendation ITU-R F.1336 Omni to mean equations 11a et seq. in that Recommendation. The antenna pattern is illustrated in Figure 3-3.


Figure 3-3: IMT Base Station Antenna Pattern

A simple omnidirectional antenna was deployed for the indoor Base Station runs.

3.3 Satellite Earth Station Data

A comprehensive set of satellite Earth station data, operating in the 3.6 - 4.2 GHz band, was provided by Ofcom for the purposes of this study.

3.4 Fixed Link Data

A comprehensive set of fixed link data, operating in the 3.6 - 4.2 GHz band, was provided by Ofcom for the purposes of this study.

3.5 Geotype Data

For the purpose of this study, we have considered five geotypes which are defined by population density thresholds following the Plum report for Huawei on The Economic Benefits of the use of C-band for Mobile Broadband in the UK3.

The geotypes are:

Hotspots (13,910 or more persons per sq. km)

Dense urban (between 10,910 and 13,910 persons per sq. km)

Urban (between 4,290 and 10,910 persons per sq. km)

Suburban (between 202 and 4,290 persons per sq. km)

Rural (between 0 and 202 persons per sq. km)

Our analysis of the pixelated population data gives the following figures in Table 4-1.

3 www.huawei.com/ilink/en/download/HW_391118 - accessed 5th March 2015

http://www.huawei.com/ilink/en/download/HW_391118


Geotype Area sq. km Population

Rural 214070 3,732,733

Suburban 28309 37,647,678

Urban 2790 15,886,506

Dense Urban 90 1,118,787

Hotspot 26 404,820

Table 3-3: Area and Population of each Geotype


4 SUMMARY OF UK SPECTRUM AVAILABILITY In this Section, we report the key points of the calculation of the amount of spectrum available across the UK for hotspot, dense urban and urban geotypes. Data is presented as maps and tables and where appropriate, cumulative distribution functions (CDFs).

The full data set is in Section 13.

4.1 Methodology

The methodology is based on performing an I/N calculation against all carriers in the satellite Earth station and fixed link databases on a grid of points covering the UK.

For each grid point the calculation is performed every 5 MHz from the low end of the band (3.6 GHz) to the high end (4.2 GHz), excluding the UK Broadband licensed frequencies (a total of 168 MHz in 2 x 84 MHz pairs within this band). Therefore, the results presented in this report are for the total spectrum available to the human population to a resolution of 5 MHz rather than contiguous spectrum. If the calculation at a point in a given 5 MHz is below the threshold for all carriers in the database then that 5 MHz is considered usable at that location.

A count of the number of available 5 MHz slots (N) is kept for each point. Therefore 5*N is considered to be the spectrum available at that location in MHz.

The calculation is performed for the whole 3.6 - 4.2 GHz range and separately for the 3.6 – 3.8 GHz and 3.8 – 4.2 GHz bands. The calculation is performed considering sharing with satellite Earth stations and fixed links together and each separately.

The output data grid is calculated using, as input, the results of the interference calculation which create the matrix:

𝜇(𝑖, 𝑗)

Where:

0 ≤ 𝑖 ≤ 𝑁𝑝 is the pixel index

0 ≤ 𝑗 ≤ 𝑁𝑐 is the channel index

And:

𝜇(𝑖, 𝑗) = 1 if the channel is available at that pixel

𝜇(𝑖, 𝑗) = 0 if the channel is not available at that pixel

The channel would be available at a pixel if the worst single entry I/N was below the threshold for all potential victim systems for that channel:

𝑇 (𝐼

𝑁) >

𝐼

𝑁(𝑅𝑋𝑙)

Furthermore, each pixel would have a geotype code identified by:

𝜆(𝑖)

The number of pixels having a particular geotype k would be N(k).


The number of channels available at each pixel would then be:

𝑁𝑎(𝑖) = ∑ 𝜇(𝑖, 𝑗)

𝑗=𝑁𝑐

𝑗=1

Then the percentage of pixels of a particular geotype code k having N channels available would be:

𝑃(𝑘, 𝑁) =100

𝑁𝜆(𝑘)∑ 𝜂(𝑖)

𝑖=𝑁𝑝

𝑖=1

And:

𝜂(𝑖) = 1 𝑖𝑓 𝜆(𝑖) = 𝑘 𝑎𝑛𝑑 𝑁 = 𝑁𝑎(𝑖)

𝜂(𝑖) = 0 𝑜𝑡ℎ𝑒𝑟𝑤𝑖𝑠𝑒

Once this grid of data has been generated, it can be processed in several ways – plotted on a map, analysed against pixel geotype, related to population covered etc.

4.1.1 Run Variations

In our detailed analysis, we have found a number of mitigation and calculation options that could effectively reduce the interference levels.

For example, additional losses due to accurate local clutter modelling, large antenna elevations and indoor losses could all be legitimately added.

These can all be modelled as single values in the interference zone simulations – and there are many possible values and combinations.

Rather than explicitly model each possible combination, the approach we have taken is to reproduce the spectrum availability grid based on relaxing the threshold by 5, 10 and 20 dB. This is an established practice in satellite Earth station coordination, where the generation of ‘auxiliary contours’ is common.

4.1.2 Interpretation of the Maps, Tables and Statistical Distribution

The data in this section is presented as colour-coded UK-wide maps, as tables of spectrum bandwidth available vs population and as cumulative distribution of bandwidth available vs population.

The colour-coded maps each have a key that looks like the following figure:

The map is divided into pixels that reflect the key – from the example above, red pixels have 0 MHz of available spectrum, the darkest blue between 155 - 225 MHz etc.


It is important to note that this scale of spectrum available may vary from map to map based on the size of the spectrum band being considered, for example if we are considering the 3.6 - 3.8 GHz band, the scale will not be the same as for the 3.6 - 4.2 GHz band.

The tables have a simple interpretation. An example for the 3.6 - 3.8 GHz band is given below:

Spectrum

Available (MHz)

Population Population

Percentage

5 438610 2.52

10 3208276 18.43

15 21721 0.12

20 45150 0.26

25 20091 0.12

35 361002 2.07

40 951509 5.47

45 56161 0.32

50 117888 0.68

65 833259 4.79

70 282223 1.62

80 1362817 7.83

100 683218 3.92

115 9028190 51.86

In this example, a total population of 17.41 million has been considered (this is the sum of urban, dense urban and hotspot areas). Of that relevant population, it is possible to see how many have X MHz of bandwidth available. In the example around 951,509 have access to 40 MHz, 9.028 million have access to 115 MHz, which is the full band in this case.

The cumulative distribution function curves are presented as ‘at least Y MHz of spectrum available’ vs. percentage of relevant population. In all the cases below, the relevant population is the 17.41 million people in the urban, dense urban and hotspot areas.

An example CDF is shown in Figure 4-1 below:


Figure 4-1: Example Cumulative Distribution Function

Each CDF allows for the comparison of different scenarios on the same picture and most of the plots show four cases as described in 4.1.1 above. To understand the information in the curves consider the following interpretation:

For a point on the X-axis (X %) read up to the curve and across the Y axis (Y MHz). This means X % of the population have access to at least Y MHz of spectrum.

The power in the graphical presentation is in the comparison of the different assumptions – corresponding to the four coloured curves. Blue is the baseline case and the others are the progressive improvements by 5, 10 and 20 dB.

Suppose the economic viability of the band for mobile use requires a minimum amount of spectrum to be available. You can read this number on the Y-axis across to each curve in turn and down to X axis to see what percent of the relevant population is denied access to this amount under the different assumptions.

The rest of this section gives a summary of the main results and a commentary on the implications of these.

4.2 Available Spectrum

Any mobile network will be constrained by the necessity to co-exist with both Earth stations and fixed links. Therefore, the most important results are those that include both services as potential victims in the calculation and these are the results we concentrate on here.


The results are presented for the whole range 3.6 - 4.2 GHz and for 3.6 - 3.8 GHz and 3.8 - 4.2 GHz separately. In all cases the UK Broadband licensed frequencies are excluded.

The complete set of results are given in Section 13.

4.2.1 Analysis of 3.6 - 4.2 GHz

The total amount of spectrum available in the whole C-band, excluding the UK Broadband licensed frequencies, is 430 MHz. The maps below show how much of this is available across the UK – all geotypes are displayed on the maps (i.e. urban, suburban and rural).

Red pixels are absent from the maps – showing there are no areas where all spectrum is denied.

Figure 4-2: Baseline Spectrum Availability: Frequency Range is 3.6 - 4.2 GHz, Sharing

with Satellite Earth Stations and Fixed Links

Large parts of the populated areas of the south east UK, particularly London and areas to the east and west of London, have between 5 - 75 MHz of spectrum available. This is a useful amount of spectrum but means over 80% of the total available spectrum is denied at these locations.


Figure 4-3 and Figure 4-4 shows that in other parts of the country 300+ MHz of spectrum is generally available, except in the north east of Scotland, where fixed links connecting the islands mean there is less than 300 MHz in some locations.

As discussed above the maps relate to the whole of the UK and all pixels have been considered, independent of geotype. It is also useful to consider how the spectrum available relates to populations in the most populated parts of the country. Figure 4-5 below shows this.

Figure 4-5: Availability of Spectrum in MHz, in the Range 3.6 - 4.2 GHz by Percentage

of Urban+ Population under Baseline Assumptions

Keeping in mind that the spectrum available is counted in 5 MHz chunks, we can see the following from the figure:

For 60% of the urban, dense urban and hotspot population there is just under 300 MHz of spectrum available.

For 80% this falls to 65 MHz.

Analysis of the underlying numbers shows that the amount of spectrum available falls rapidly for 97%+ of the urban+ population. 97% having access to 40 MHz but 98% having access to less than 10 MHz.

4.2.2 Analysis of 3.6 - 3.8 GHz

The pattern of available spectrum is broadly repeated in the 3.6 - 3.8 GHz range as shown in the figures below. We see some difference in the overall picture but in the most populous areas the underlying numbers are similar.


Note that the range in the colour scale is different here, because there is only 115 MHz of spectrum available. However, the colours represent approximately the same percentage of spectrum as in the previous section.








The maps relate to the whole of the UK across all geotypes. It is useful to consider how the spectrum available relates to populations in the most populated parts of the country. The CDF at Figure 4-9 below shows this.


Figure 4-9: Availability of Spectrum in MHz, in the Range 3.6 – 3.8 GHz by Percentage



For 60% of the urban, dense urban and hotspot population there is around 85 MHz of spectrum available in this part of the band.

This falls rapidly between 75-80%, 76% having access to 40 MHz but 79% having access to 15 MHz.

4.2.3 Analysis of 3.8 - 4.2 MHz

The pattern of available spectrum is broadly repeated in the 3.8 – 4.2 GHz range as shown in the figures below. We see some difference in the overall picture but in the most populous areas the underlying numbers are similar.

Note that the colour scale is different here, because there is only 315 MHz of spectrum available. However, the colours represent approximately the same percentage of spectrum as in the previous section.




One thing to note in this plot is that there are areas with red pixels – close to satellite Earth stations. Recall that the red pixel means 0 MHz of spectrum available in the 3.8 - 4.2 MHz band.






The maps relate to the whole of the UK across all geotypes. It is useful to consider how the spectrum available relates to populations in the most populated parts of the country. The CDF at Figure 4-13 below shows this.


Figure 4-13: Availability of Spectrum in MHz in the Range 3.8 - 4.2 GHz by Percentage



For 60% of the urban, dense urban and hotspot population there is around 205 MHz of spectrum available in this part of the band.

At 80% of the urban+ population this has fallen to 60 MHz.

This falls rapidly above 97%. 97% having access to 35 MHz but 98% having access to only 5 MHz in this part of the band.

4.2.4 Impact of Mitigations

Various mitigation techniques have been identified in this study. Whilst many of these are site specific, it is still useful to see the effect that a generally applied improvement would bring.

We have modelled this by changing the I/N threshold in the simulation methodology by 5 dB, 10 dB and 20 dB.

Graphically we can see this in Figure 4-14 below:




Figure 4-14: The Available Spectrum in London area, in the Baseline Case and with 5,

10 and 20 dB of mitigation, in 3.6 - 4.2 GHz Sharing will all Satellite Earth Station and

Fixed Link Carriers

The pink pixels have less than 75 MHz of spectrum available.

Light blue pixels represent areas that have more than 230 MHz available (more than half the available spectrum). Green pixels have access to the entire spectrum.


A key feature of this graph is that even with 20 dB of mitigation there are areas in a relatively narrow band that are pink. This reflects the impact of the fixed links, as discussed in Section 12.4.1, which provide low latency, high data rate connections across London.

The CDF at Figure 4-15 below summarise the statistics of spectrum availability under baseline assumptions and relaxations by 5, 10 and 20 dB, showing the impact of mitigations on the spectrum available per head of urban+ population.

Figure 4-15: Availability of Spectrum in MHz, in the range 3.6 - 4.2 GHz by Percentage

of Urban+ Population under Baseline Assumptions, 5, 10 and 20 dB Relaxations

4.3 Separate Analysis of Satellite Earth Stations and Fixed Links

Section 13 contains full details of the spectrum that would be available if sharing with only the satellite Earth stations or fixed links. The analysis shows that sharing with fixed links results in the largest constraints on the spectrum.

It is apparent that, whilst a satellite Earth station may experience interference from a large area this has a much smaller impact on practical spectrum availability than the fixed links we have modelled.

This is partly because the fixed link receivers tend to be higher up, with low elevation main beams. Another factor is that the fixed links are in the densely populated areas where the small cell mobile networks are most likely to be deployed.

The dominant role of the fixed links masks the fact that the satellite Earth station use of the band is only a minor constraint on mobile usage in urban areas.


4.4 Conclusions

The following table summarises the spectrum available.

The principal conclusion is that there is scope for sharing spectrum in this band. The reason we believe this is that, as the table shows, even in the baseline case, 80% of the 3.6 - 4.2 GHz spectrum band is available to >50% of the urban+ population – which represents a massive potential economic value.

Half the existing spectrum is available to 65% of the urban+ population, and this increases to 88% if 20 dB of mitigation is applied.

However, even on the application of 20 dB of mitigation, potential interference cannot be ruled out for all frequencies and all geographic locations.

The implication, therefore, is that a managed approach to shared access of the band on a geographic basis has great merit, and should be able help facilitate spectrum sharing.

Percent of

total

spectrum in

3.6 - 4.2 GHz

(430 MHz)

% of urban+ population this is available to

Baseline

case

5 dB

relaxation

10 dB

relaxation

20 dB

relaxation

20% 79% 83% 91% 99%

50% 65% 68% 75% 88%

80% 52% 55% 60% 75%

100% 45% 48% 52% 64%

Table 4-1: Breakdown of Percentage of Urban+ Population that has access to X% of

Spectrum

The results show that the fixed links are a much larger constraint on the use of C-band for mobile than the satellite Earth stations are.

Even under the baseline case, useful amounts of spectrum could still be used by large percentages of the urban+ population. The minimum useful amount of spectrum for IMT-A is considered to be 5 MHz,and in many populated areas there is significantly more spectrum available.

Applying mitigations up to 20 dB improves the situation, but areas of significant constraint on the mobile network remain – our study shows a band across central London where 50% or more of the available spectrum is denied. This reflects the presence of low latency links on high towers across the most populous area of the South East.

The same 20 dB improvement would mean sharing of mobile services with satellite Earth stations also appears possible, though the same constraints in London would apply.

No major difference between 3.6 - 3.8 GHz and 3.8 - 4.2 GHz ranges is seen in the analysis.


5 INTERFERENCE ZONE ANALYSIS This section is a description of the work done looking at specific satellite Earth station and fixed link sites.

In this section, we look at interference zones around selected satellite Earth station and fixed link sites. We explore how these zones are affected by different assumptions and potential mitigations.

5.1 Satellite Earth Station Interference Zone Analysis

This part of the study considered Area Analyses for two carriers at the Chalfont Grove site and looked at the area south-east of the site, which includes greater London.

The Chalfont site has a number of antennas – including some operating at low elevation angle towards satellites in the east. The site has licensed carriers across a large part of the C-band.

The area analysis splits a large area into small pixels and performs the interference calculation at each pixel. When the I/N threshold is exceeded, the pixel is considered to be part of the interference zone. The output is as a colour code map overlay that indicates that I/N would be exceeded, under stated assumptions.

This type of analysis is commonly seen internationally in JTG and prior to that in Report 2109. As such, it provides us with a test bed for comparing JTG methods with our baseline and with the variations to the baseline that are supported by the detailed analysis in Section 6.

5.1.1 Baseline System Parameters

The IMT parameters are described in Section 3.2.

The licensing data for the site at Chalfont Grove contains 58 licensed carriers with differing parameters that will affect the calculation of the interference zone. Parameters that influence the I/N calculation are:

1. Antenna azimuth and elevation. Low elevation operation in the direction of a proposed IMT network will generate the worst case. If we are considering London then low elevations to the southeast will be the most representative case.

2. Antenna height above the local terrain. Generally, this is important because height provides clearance from local shielding. All antennas in the Chalfont Data are at the same height.

3. Antenna gain and sidelobe performance. In practice, the sidelobe gain is important. Even for the lowest elevation angles and for the smallest dishes the interferer will not impact the main lobe. All the Chalfont antennas are specified as per REC-580. Recommendation ITU-R S 580-6 gives a sidelobe gain performance that is independent of peak gain.

4. Link noise. Lower noise means that there is a higher I/N for a given value of I. The lowest elevation links have a temperature of 79K and the next lowest are 60K.


We would add a further assumption that the calculation is essentially independent of bandwidth and frequency. Based on these considerations we propose to model two sets of parameters for Chalfont as in Table 5-1 below:

Parameter Carrier 1 Carrier 2

Antenna Elevation 8,0033 10.9055

Antenna Azimuth 112.13 116.47

Antenna Height 10m 10m

Peak Gain 55 55

Sidelobe Performance Rec 580 Rec 580

Link Temperature 79 K 60 K

Table 5-1: Modelling Parameters for Chalfont Earth Station

The area analyses are configured such that ITU-R P.452-15 is used to model losses on the interference path and predict the interfering signal power of the median interferer incident to the fixed link receiver. The Ofcom terrain and clutter database are deployed.

The baseline case uses 50m terrain data and a complementary clutter database.

5.1.2 Simulations

The simulations aim to show the size of the interference zone under a number of assumptions. These can be categorised as improvements on the baseline and degradations from the baseline as discussed here:

Section 7 presents detailed analysis using very high fidelity modelling of the local environment, looks at aggregation and suggests that our baseline area analysis modelling could justifiably be modified.

Our baseline uses detailed data that are not always available, for example to other administrations. So JTG has presented a variety of other analyses and defines a ‘generic’ case. It is very useful to compare this to our results.

Baseline runs have been made for the small cell indoor and outdoor cases, run variations concentrate on outdoor cases only.

So we have performed simulations (Table 5-2) ranging from the non-site-specific to baseline case and to baseline modified to account for dense urban geometries, power management and traffic levels.


Case 1 JTG ‘non site specific case’- no terrain data, no clutter losses

Case 2 Terrain but no clutter loss

Case 3 Our baseline case

Case 4 Our baseline adjusted to reflect extra losses from dense urban

cells and aggregation

Table 7-1: Diffraction vs. Clutter Loss gives a baseline additional

loss of 17.3 dB but Section 7 indicates that aggregation from

dense small cells could be at least 10.9 dB. This gives a net

advantage of 6.4 dB.

Case 5 Case 4 with additional reductions when considering power,

polarisation and traffic.

Section 7.5 suggests an additional 3.8 dB advantage

Table 5-2: Five cases studied

The modification we introduce in Case 4 reflects the average values found in Section 7.

5.1.3 Outdoor Small Cells

Figure 5-1 below shows comparative results obtained around the Chalfont site, which is marked with the black star.

Case 1 - smooth earth case (shown by the black contour). All points inside the contour are above the interference threshold and hence spectrum cannot be used by IMT. All points outside the contour are below the threshold

Case 2 - with terrain database but no local clutter loss (shown as red pixels). All red pixels are above the interference threshold.

Case 3 - with terrain and local clutter (baseline case shown as blue pixels). All blue pixels are above the interference threshold.

It should be noted that there are many red pixels covered by blue pixels close the Chalfont site.


Figure 5-1: Comparison Interference Zones of the Baseline Case, Case with

Clutter Loss Removed and JTG Non Site-Specific Case i.e. Smooth Earth.

Table 5-3 shows the largest separation distance and the area of denied pixels for the three cases.

Case Largest separation

distance km

Area of denied pixels4

km2

Case 1 25 823

Case 2 73 775

Case 3 (baseline) 70 215

Table 5-3: Separation Distance and Area of Denied Pixels for Cases 1, 2 and 3

Some interesting points to note are:

1. The JTG generic case is not necessarily the worst case. When terrain is added, the effect of higher ground can be clearly seen.

2. Inclusion of a clutter database does not have a great effect on the maximum separation distance, but greatly reduces the total area of denied pixels.

4 Note this calculated area is presented for comparative purposes only. It is a function of the size of the

Area Analysis which is arbitrary.


Figure 5-2 shows the additional impact of Case 4 (shown in yellow) and Case 5 (shown in red), which take a simplified account of the findings of our detailed analysis. Note that there are yellow pixels beneath all the red pixels, due to the additional improvement introduced in Case 5

Figure 5-2: Additional Impact of Case 4 and Case 5.

Case Largest separation

distance km

Area of denied pixels5

km2

Case 3 (baseline) 70 215

Case 4 25 84

Case 5 24 55

Table 5-4: Separation Distance and Area of Denied Pixels) for Cases 3, 4 and 5

Note that when the additional advantages of cases 4 and 5 are taken into account both the largest separation distance and the area of denied pixels decreases.

5.1.4 Indoor Small Cells

Our baseline indoor parameters introduce 25 dB of extra advantage due to the lower power operation and a 20 dB indoor/outdoor loss. Lower antenna height assumptions also have a small effect.

5 Note this area is presented for comparative purposes only. It is a function of the size of the Area

Analysis which is arbitrary.


When we simulate this against the two carriers at Chalfont Grove we find a separation distance of 3 km but very few affected pixels.

Even the local area is essentially unaffected as can be seen from Figure 5-3 – the interference zone around Chalfont Grove, for baseline indoor small cell case. The Blue pixels show the affected areas, around the Chalfont site and a further affected point around 3 km to the south east.

Figure 5-3 –Interference Zone around Chalfont Grove for Baseline Indoor

Small Cell Case.

5.1.5 Conclusions from Satellite Earth Station Interference Zones

The interference zone analysis provides a quick way to get an overview of a local situation that may be useful in coordinating a specific site or just as a way to get a high level feel for the problem.

It is also a good tool for testing variations in parameters and mitigations.

We have found the following to be the case:

The non-site specific or generic case used in many JTG studies is not always the worst case. In some sense, this is the furthest from a generic study that we could get – as almost no locations can be accurately modelled as smooth Earth. The value of generic studies to the UK context is very limited.

In the international context studies that use no terrain, or use terrain without a clutter database, or studies that result in a recommended ‘minimum separation distance’ are also of limited value. We find that whilst the use of clutter data does not reduce the maximum required separation very much, it does dramatically reduce the area of the interference zone.

When taking into account in a simple way the results from our detailed analysis in Section 7, the interference zone shrinks dramatically.


For indoor small cells, under the baseline assumptions, the interference zone around Chalfont is very small – the maximum separation required is 3km, although there are plenty of locations closer to the site that show no problems.

5.2 Fixed Links Interference Zone Analysis

This study considered Area Analyses for a sub-set of the fixed links data. Sixteen receivers were selected in the London area. Each receiver was considered in isolation and subject to two simulations where it was exposed to interference from outdoor and indoor small cell base stations.

Each pixel of 0.25 km2 in the area analysis is considered to be a potential location for base stations, therefore each pixel is modelled as an interference source and the interfering signal power incident to the fixed link receiver is calculated. The entire bandwidth of the 30 MHz fixed link receiver is populated with 10 MHz IMT interferers. Hence, in these analyses, single-entry interference is defined as multiple interfering signals sourced from a single location.

5.2.1 Simulations

Table 5-5 shows the schedule of simulation runs for fixed links.


Station name Request Runs

BT Tower 0979750/1 Outdoor base station,

Indoor base station

BT Tower 0979755/1

Outdoor base station,

Indoor base station

Hillingdon 0979631/1


Indoor base station

Hillingdon 0980503/1 Outdoor base station,

Indoor base station

Hillingdon 0908534/1 Outdoor base station,

Indoor base station

Hillingdon 0980547/1


Indoor base station

LSE 0979731/1 Outdoor base station,

Indoor base station

LSE 0979745/1 Outdoor base station,

Indoor base station

LSE 0979750/1


Indoor base station

Royal Free 0979647/1 Outdoor base station,

Indoor base station


Indoor base station

Royal Free 0980503/1


Indoor base station


Indoor base station

Wanstead 0979647/1 Outdoor base station,

Indoor base station

Wanstead 0979650/1


Indoor base station

Wanstead 0980565/1 Outdoor base station,

Indoor base station

Table 5-5: Run Schedule: Fixed Links Area Analyses

The area analyses were configured such that ITU-R P.452-15 was used to model losses on the interference path and predict the interfering signal power of the median interferer incident to the fixed link receiver. The Ofcom terrain and clutter database were deployed.

5.2.2 Example Simulation: Outdoor Base Station

Figure 5-4 shows the results of an area analysis for request 0979750/1 (BT Tower) considering interference from an outdoor IMT Base Station.

For the outdoor Base Station run, the area where denied pixels (red) are present corresponds to a representation of the fixed link antenna pattern. If we


switch off the terrain and clutter database as shown in Figure 5-5 the pattern is more comprehensive, suggesting a frequency coordination zone reminiscent of the classical keyhole coordination procedures. This is also a useful illustration of the impact of terrain and clutter data on the modelling and on frequency coordination in general.

Figure 5-4: Area Analysis for Request 0979750/1 (BT Tower, London): Outdoor

Base Station (Denied Area = 511 km2)

Figure 5-5: Area Analysis for Request 0979750/1 (BT Tower, London): Outdoor Base

Station, Smooth Earth (Denied Area = 751.75 km2)

With terrain and clutter included in the analysis, 2044 pixels of 0.25 km2 and a total area of 511 km2 are denied to the IMT base station; that is, interfering signal power exceeds the protection criterion for the fixed link receiver when the base station is located in one of these pixels. With terrain and clutter switched off, 3007 pixels and a total area of 751.75 km2 are denied.

For this example, the area populated by the denied pixels extends around 50 km east from the fixed link antenna and the widest dimension of the denied area is around 32 km using terrain plus clutter and around 27 km with these features switched off. Although, in general, the use of terrain and clutter will


reduce the count of denied pixels, use of this data will sometimes result in a more potent model of the radio interference path.

5.2.3 Example Simulation: Indoor Base Station

Figure 5-6 shows the results of an area analysis for request 0979750/1 (BT Tower, London) considering the indoor IMT Base Station. In this case, the interference is attenuated by 20 dB to account for building loss (indoor-outdoor).

Figure 5-6: Area Analysis for Request 0979750/1 (BT Tower, London):

Indoor Base Station (Denied Area = 27.5 km2)

Here, the denied area is reduced to 27.5 km2 when the IMT Base Station is indoors with 110 denied pixels located in the main beam of the fixed link antenna i.e. at locations where the interfering signal is subject to the maximum antenna gain available from the fixed link.

5.2.4 Set of Visualyse Simulations

The area analyses are a useful preliminary investigation into the sharing problem. The results are very similar for all of the fixed link receivers investigated and they all show, very clearly, that there are very significant constraints on sharing between fixed links and mobile base stations when the two services are operating co-frequency. These constraints are greatly reduced but still significant when the mobile base station is located indoors and a reasonable assumption made with regard to building loss.

The entire set of fixed link area analyses simulation files are designated as a project deliverable.


6 ADJACENT CHANNEL INTERFERENCE ISSUES This section reports on our investigations into adjacent channel interference. Some supplementary technical information on net filter discrimination calculations and Out-of-Band spectrum masks is provided in Section 11.

6.1 Adjacent Channel Interference into Fixed Links

Net Filter Discrimination (NFD) can be defined as the advantage obtained on the radio interference path when the interferer is offset in frequency from the victim receiver, relative to a scenario where victim and interferer are co-frequency. NFD is expressed in dB and can be subtracted from the interferer’s power at a suitable point on the radio interference path.

The calculation of NFD requires spectrum masks for the transmitter and the receiver. ETSI TR 101 854 sets out a well-established method for calculating NFD where spectrum masks are convolved in frequency; this method is used by Ofcom in its frequency assignment and frequency coordination work.

Spectrum masks for fixed links are easily available (although the technical standards can be complex and difficult to interpret) and a basic IMT mask can be modelled based on discussions in international fora. Spectrum masks for satellite Earth station receivers are much harder to acquire.

Simple default masks are used in professional practice including by Ofcom. We have derived the results of some NFD calculations using a Gaussian curve to represent the satellite Earth station receiver mask.

6.1.1 NFD Calculations

Convolving the Out-Of-Band (OOB) spectrum masks and exercising Equation 11-1 at each discrete frequency offset between carrier frequencies, we obtain a graph of the NFD available; this is shown in Figure 6-1.

Figure 6-1: Net Filter Discrimination

We consider a specific interference scenario where two IMT interferers, operating in 10 MHz bandwidth, are tuned such that they operate in the first 10 MHz channel adjacent to the fixed link receiver bandwidth, one either side of the fixed link’s 30 MHz receiver channel.


This scenario results in a 20 MHz frequency offset between the fixed link carrier and each of the IMT carriers. Using the method described here, we obtain 23.48 dB of NFD.

The NFD can be applied at a convenient point on our model of the radio interference path and in these calculations, we make adjustments at the source of interference by reducing the IMT transmitter (TX) power. Table 6-1 illustrates calculations for aggregate transmitter power from the two IMT adjacent channel interferers in 1 MHz of bandwidth.

Description Value Unit

TX power in 10 MHz 24 dBm

NFD for 20 MHz frequency offset 23.48 dB

TX power in 1 MHz -14.25 dBm

Activity Factor 3 dB

Adjusted TX power in 1 MHz -17.25 dBm

Adjusted TX power in 1 MHz -47.25 dBW

Two adjacent channel interferers -44.25 dBW

Table 6-1: NFD and Adjusted Transmitter Power

Using the value -44.25 dBW/MHz, we revisit some area analyses to assess whether adjacent channel interference exceeds the protection criterion at the fixed link receiver.

6.1.2 Analyses: Outdoor Base Stations

Figure 6-2 shows an area analysis for request 0979750/1 (BT Tower, London) where the fixed link receiver is exposed to adjacent channel interference only. 164 pixels and a total area of 41 km2 are denied to the IMT Base Station.


Figure 6-2: Area Analysis for Request 0979750/1 (BT Tower, London): Outdoor Base

Station Operating in Adjacent Channels (Denied Area = 41 km2)

A further example is given in Figure 6-3 where we expose request 0980547-1 (Hillingdon, London) to adjacent channel interference. Here, 96 pixels and a total area of 24 km 2 are denied.

Figure 6-3: Area analysis for Request 0980547-1 (Hillingdon, London): Outdoor Base


Both of these requests were considered again, modelling adjacent channel interference from IMT base stations located indoors. Figure 6-4 and Figure 6-5 show the results of the area analyses.


Figure 6-4: Area Analysis for Request 0979750-1 (BT Tower, London): Indoor Base


Figure 6-5: Area Analysis for Request 0980547-1 (Hillingdon, London): Indoor Base

Station Operating in Adjacent Channels (Denied Area = 0.25 km2)

For request 0979750-1 (BT Tower, London), no pixels are denied and for 0908547-1 (Hillingdon, London), one pixel is and a total area of 0.25 km2 are denied.

We can see from these investigations that adjacent channel interference cannot be neglected and that there is potential for harmful interference incident to the fixed link receivers from the outdoor base station. Clearly, the results for the indoor base station is far more optimistic and, depending on the exact sharing objectives, some further study may be appropriate including consideration of alternative interference scenarios over a larger set of receivers.


6.2 NFD Calculations for Satellite Earth Station and IMT Interference

This section has focused on a case study where NFD is applied to a scenario where the victim fixed link is exposed to adjacent channel interference (ACI) from IMT. Here we report on some calculations for NFD when a satellite Earth station receiver is victim to a 10 MHz IMT interferer.

Spectrum masks for permanent earth station receivers are not easily available and it is common practice to use default spectrum masks. Here, we model a Gaussian curve extending two times the transponder bandwidth and attenuating to -30 dB at the lower and upper bounds of the curve. Figure 6-6 shows a graph of this default permanent earth station mask.

Figure 6-6: Default Gaussian Spectrum Mask for Earth Station

Using the default satellite Earth station mask in Figure 6-6 and the IMT mask shown in Figure 11-2, we calculate NFD over a range of frequency offsets. The results are presented in Figure 6-7.

Here we see NFD calculated up to the point where the masks are overlapping by 1 MHz in the frequency domain; at this point around 95 dB of NFD is available.

-35

-30

-25

-20

-15

-10

-5

0

-72 -52 -32 -12 8 28 48 68

Attenuation (dB)

Frequency offset from carrier frequency (MHz)


Figure 6-7: NFD: 72 MHz Satellite Earth Station and 10 MHz IMT

These results can be used to consider the adjacent channel interference problem. If we consider a similar scenario to that modelled for the fixed link case, where 10 MHz bandwidth mobile interferers are located in the first 10 MHz channel either side of the satellite Earth station bandwidth, then the frequency separation between satellite Earth station and mobile carriers is 41 MHz and 9.51 dB of NFD is obtained.

Use of a Gaussian default mask is likely to be conservative relative to a mask based on measurements or even one defined in the manufacturing standards. Returning to the fixed link case study, if we replace the ETSI OOB mask with a Gaussian curve then the NFD obtained for the specific scenario investigated is reduced to 11.79 dB (from 23.48 dB). Clearly, the NFD calculations are highly dependent on the inputs; that is, the spectrum masks.

6.3 Notes and Conclusions on NFD and ACI

The case study examined here shows that adjacent channel interference cannot be neglected. A significant number of locations are denied when the IMT Base Station is outdoors. The indoor case appears to be favourable but a more comprehensive investigation could be considered.

NFD calculations are dependent on the spectrum masks and when default masks are utilised, these tend to be conservative, leading to spectrum denial when spectrum access is possible. The Gaussian curve is a typical example of a convenient default spectrum mask. This is used by Ofcom in its frequency assignment and frequency coordination procedures to model the satellite Earth station emissions. However, it may be very difficult in practice to replace these with masks based on the real or standardised performance of the radios.

In general, modern frequency assignment/coordination procedures will model adjacent channel interference in order that a candidate transmitter satisfies protection criteria at potential victim receivers that are co-frequency and in adjacent frequencies.


7 SUMMARY OF HIGH RESOLUTION DETAILED ANALYSIS

7.1 Overview

One of the key challenges in undertaking interference analysis is to balance the need to protect incumbent services without being over conservative by taking a series of worst-case assumptions. One way to facilitate sharing is to use models that are more detailed. This can reduce the number of assumptions and generalisations that are required.

The following approaches to modelling propagation paths can be considered improvements due to the increasing level of detail:

1. Smooth Earth, no terrain or clutter

2. Use of a terrain database

3. Use of terrain and land use database

4. Use of a surface database

The majority of the study was undertaken with the third of these, as this was the most detailed level information available on a UK-wide basis. However, for central London a higher resolution 3m surface database was used.

This surface database allowed us to analyse a small number of cases in high-resolution, considering the impact of the need to protect existing fixed links or satellite Earth stations on the ability of a mobile network operator to deploy small cell base stations in a dense urban environment.

Further information on the high resolution analysis is given in Section 12.

7.2 Factors Specific to the High Resolution Analysis

The basis of the high-resolution study was a selective qualitative analysis using a 3m resolution surface database within central London. We consider this representative of the type of high-density urban areas where mobile networks are likely to be deployed.

From the assignment database provided by Ofcom the following were selected for high-resolution analysis:

Earth station (ES): a very small aperture terminal (VSAT) in central London.

Fixed links: BT Tower, with link connecting to the LSE.

The analysis methodology in each case was as follows:

Deployment:

Calculate the number of small cell base stations within a circle centred on the Earth station or fixed link receive station, taking into account the ratio of small cells to macro cells [1, 2, 3].

Position each base station at random within the circle.

Where necessary (e.g. random location results in base station on top of a building), move base station to nearest street.


Make limited adjustments for location (e.g. avoid very low separation distances between base station and relocate some of the base stations that were deployed within parks).

For the directional case, orientate antenna to point along the street.

Analysis:

1. Calculate aggregate I/N at Earth station or fixed link receive station from all base stations.

2. If the aggregate I/N > T[I/N] dB then:

a. Identify the worst single entry case

b. Remove that base station from the group of interfering base stations

c. Continue at Step 1

3. Output final base station deployment

7.2.1 Databases

The analysis was based upon terrain and surface databases for the areas where satellite Earth stations are located. The following databases were available:

Ofcom’s standard 50 m terrain and 50 m land use code database

High resolution 3 m surface database of central London

The following figures show central London in 50 m terrain (Figure 7-1) and 3 m surface resolution (Figure 7-2). Even from these small pictures, it is clear that the 3 m data captures much more about the central London environment than the 50 m data. Streets and individual buildings are clearly visible and can be explicitly modelled.


Figure 7-1: 50m Terrain Data of Central London

Figure 7-2: 3m Surface Database of Central London


7.2.2 Propagation Models

The databases described in the previous section were used as inputs into the propagation models, in particular Recommendation ITU-R P.452.

This model includes a number of propagation modes that are selected based on an analysis of the path profile created from the terrain or surface database. The relevant terms are then calculated and merged mathematically to generate a path loss.

A terrain database, as the name implies, represents the height of the terrain underlying the stations, built environment and vegetation that we are trying to simulate. If we use a terrain database, the model can then be extended to include clutter loss based on local clutter types. This requires a database, such as the 50 m data, which maps on to the clutter codes of the Recommendation as described in Section 12.2.2.

A surface database, on the other hand, represents the height of the terrain plus anything substantial that sits on top of the terrain. As mentioned above, a surface data of sufficiently high resolution will represent buildings and streets.

If a surface database is used then it is not necessary to include the clutter loss as an extra term, it will be accounted for by P.452 path loss using the diffraction model applied to the local environment as additional ‘obstacles’ on the path.

While the two approaches (diffraction and local clutter loss) are based upon common concepts, they are implemented differently and this leads to significantly different results as can be seen in Table 7-1.

Obstruction Close Baseline Far

Frequency (GHz) 3.8 3.8 3.8

Transmit antenna height (m) 6 6 6

Obstruction height (m) 20 20 20

Distance to obstruction (m) 2 20 500

Distance from obstruction to

receiver (m) 1000 1000 1000

Clutter loss (dB) 19.7 19.4 11.9

Diffraction loss (dB) 46.9 36.9 24.6

Table 7-1: Diffraction vs. Clutter Loss

In particular, the clutter loss is capped at around 20 dB while the diffraction loss can be much greater in the right hand column for the case where the transmitter is closer to the obstruction.

As the land use database does not know the actual case involved, it must use simplifying assumptions and generate a typical value that might not be applicable for most actual deployments.

Analysis presented in detail in Section 12.3.4 suggests that the interference can become either:

An aggregate of multiple interferers all significantly attenuated due to large diffraction losses


Dominated by a single interferer that has significantly lower diffraction loss (e.g. due to street being aligned with the victim)

7.2.3 Antenna Gains

Another factor that will have a significant impact on the interference calculation is the gain at the transmit antenna, and this will vary depending upon the terrain or surface database used.

If a terrain database is used then it is likely that for short paths the direct path is used to calculate the transmit gain, but if a surface database is used the radio path can be very different and hence the gain calculated also differs, as in Figure 7-3.

Figure 7-3: Radio Path vs. Direct Path

This would lead to large differences in the calculated aggregate interference level, particularly if the base station is modelled using measured data from a directional antenna.

One output from the detailed analysis in Section 12 is the combined effect of using diffraction in place of clutter and of accounting for the elevation dependence of the base station.

7.2.4 Summary

Two mechanisms were identified by which the aggregate interference calculated using a high-resolution surface database could be significantly different from that derived using terrain and land use codes:

1. The clutter loss calculation uses fixed parameters and is capped at around 20 dB.

2. The transmit gain calculated using a terrain database is likely to use an inaccurate direct path.

This suggests that the lower aggregate interference levels calculated using a surface database are based upon real phenomena and can be accepted for use in further analysis.

7.3 Earth Station Test Case

7.3.1 Elements of the Analysis of the VSAT case

The previous section identified benefits in analysing sharing between mobile network base stations and incumbent systems using a high resolution surface database. This section considers the impact on satellite Earth stations using a specific VSAT station on a roof in central London.


The density of small cell outdoor base stations was derived from:

Small cell outdoor: 2 per urban macro cell

Urban macro cell every 0.6 km

50 small cell outdoor base stations were deployed over an area calculated from the above to be a circle of radius 1.69 km based upon the victim Earth station as shown in Table 7-2.

Macro base station separation distance (km) 0.6

Number of Small Cell / Macro base station 2

Area / Macro base station (km2) 0.36

Area / Small Cell (km2) 0.18

Number of Small Cell in simulation 50

Area of Simulation (km2) 9

Radius of deployment zone (km) 1.69

Table 7-2 : Deployment Density for IMT-Advanced Small Cell Outdoor Systems

As described in Section 12 two mobile scenarios were modelled – one using omni-directional antennas and one using measured base station performance.

Locations of the 50 small cell base station were randomised within a circle of radius 1.69 km around the Earth station. They were then moved to the nearest street. For the measured base station data the antenna was pointed along the street.

No attempt was made to analyse interference between base station or the coverage / service provided. The resulting initial deployment locations are shown in Figure 7-4.


Figure 7-4: 50 Small Cell Base Stations Located within 1.69 km of Victim Earth Station

in Central London

A full description of the simulations and the analysis is given in Section 12 including:

1. How interfering base stations were identified and removed to give a final deployment consistent with the I/N threshold

2. Single entry and aggregate interference

3. Analysis with 1,2 or 3 small cells per macro cell

4. Operation in adjacent channel

5. Mitigation options and their effectiveness

7.3.2 Summary Results

The analysis suggests that the exclusion zone around an Earth station where a mobile small cell base station would not be permitted could be small, possibly in the range 0.56 – 3.3 km2 without mitigation.


The small size of exclusion zone is due to the mobile network base stations operating on lower power below the clutter in a dense urban environment where there will be significant off-axis gain and diffraction loss.

The zone can be reduced using various mitigation methods and could be as small as 0.02 km2.

One possible approach to facilitate shared use of this band by mobile networks would be to include in the licence terms and conditions the necessity of protecting a list of existing satellite Earth station. A suitable threshold would be either:

Single entry I/N suitably adjusted for aggregation

Aggregate I/N threshold

The mobile operator could also offer to the Earth station operator:

Site shielding around the Earth station;

A larger replacement antenna with higher gain and/or lower far-off-axis gain values.

Either of these methods would significantly reduce the average area excluded.

Aggregation interference was observed to be between 9 - 11 dB higher than single entry levels.

The analysis was undertaken for 1, 2 and 3 small cell base stations per macro cell. Similar behaviour was observed in each case, though the omni antenna deployment appeared to be reaching an interference driven limit in the number of base stations that could be deployed.

7.4 BT Tower Test Case

This section describes analysis interference into a fixed link receiver from small cell mobile network base stations in a dense urban environment to identify the degree to which the deployment would be constrained by its presence. The objective was to gain an understanding of a single specific sharing scenario located where high-resolution surface data was available by modelling it in detail.

A critical case was considered to be the BT Tower as:

1. It is located at the centre of a dense urban area (central London).

2. The receiver height is large, increasing the difficulty of sharing.

The receive antenna at the BT Tower was therefore used as the basis of the analysis.

7.4.1 Elements of the Analysis of the BT Tower Case

The mobile deployment was specified using 100 small cell outdoor base stations deployed over an area calculated in Section 12.3.1 to be a circle of radius 2.39 km around the BT Tower as shown in Table 7-3.



Number of Small Cells / Macro base station 2


Area / Small Cells (km2) 0.18

Number of Small Cells in simulation 100



Table 7-3 Deployment Density for IMT-Advanced Small Cell Outdoor Systems

Locations of the 100 small cell base station were randomised within a circle of radius 2.39 km around the BT Tower. They were then moved to the nearest street and for the measured base station data case their antenna was pointed along the street. No attempt was made to analyse interference between base station or the coverage / service provided. The resulting initial deployment locations are shown in Figure 7-5 with terrain colour coded so that lighter shades are higher.

Figure 7-5: 100 Small Cell Base Station Located Within 2.39 km of Victim Fixed Link

Station in Central London


The same 3 m resolution surface database was used as for the central London VSAT site analysis. In this case an adjustment was made to the surface database to remove the BT Tower which would be interpreted (incorrectly) as an obstruction by P.452.

Note that the propagation model was configured with a percentage of time = 50% to be consistent with the fixed link receiver threshold.

Section 12 give a full description of the analysis and includes:

1. Details of the fixed link parameters

2. Consideration of appropriate threshold and interference apportionment in this specific case

3. Identifying interfering base stations to develop a deployment consistent with the I/N threshold

4. Analysis of average values of gain + diffraction losses

5. Concept of an average excluded zone base on smooth Earth propagation plus the average value of gain and diffraction.

6. Potential mitigations and their impact.

7.4.2 Summary Results and Conclusions BT Tower Case

The interference zone around the fixed link receiver on the BT Tower was found to be on average 18.2 – 77.5 km2 in size.

This zone was calculated using average gain + diffraction plus smooth Earth losses. The zone can be reduced using a number of mitigation techniques, discussed in detail in Section 12.3.7

However, the average interference zone contained many locations where a base station could be located due to higher diffraction losses.

This could facilitate operation very close to the fixed link station: indeed for the deployment of 100 base stations considered, between 94% and 96% were found to be located in positions that had sufficient diffraction to protect the fixed link receiver. In particular, a key factor was the fixed link antenna receive gain, and hence in locations not in its main beam there was high likelihood of ability to deploy small cell base stations.

It is also noted that for the omni antenna case the aggregate I/N = -0.3 while for the directional case it was -2.3 dB. With an adjacent band discrimination or NFD of 23.5 dB, this means that all of the base station locations considered could operate without causing harmful interference when transmitting non-co-frequency.

7.5 Power and Traffic

This section describes results from using Monte Carlo analysis to convolve:

Variations in base station transmit power due to possible traffic variation over the whole day

Use of P.2001 propagation model using full percentage of time range [0, 100]

Polarization loss with range [0, 3] dB


The results, as presented in detail in Section 12.5, suggest that the mean power that could be used with P.452 and a percentage of time = 20% would be lower at 6.1 dBm / MHz or -23.9 dBW / MHz.

Alternatively, the power could be reduced by a further 2.3 dB to take account of the time of day variation using the alternative traffic profile. When combined with average polarization loss of 1.5 dB this would give a total reduction of 3.8 dB.

Note that this reduction in power relates to traffic variation and the power per user would not necessarily be affected.

7.6 Conclusions from High Resolution Detailed Analysis

The spectrum availability maps we have developed in this analysis are likely to be conservative in dense urban areas. This is despite the fact that our method already improves on the one commonly used internationally in JTG 4-5-6-7.

There is significant potential to deploy low power low height base stations very close to satellite VSAT type Earth stations. The fixed link case is harder but operation is still possible close to point to point fixed link receivers located in dense urban areas. The key is to ensure there isn’t line of sight between interferer and victim stations, and preferably a significant degree of diffraction loss due to buildings.

This would impose constraints on where the mobile operator could deploy their base station, requiring them to (for example), choose the side of the street with the greatest radio “shadow”. However there would be significant benefits in terms of the number of locations that could be served.

There are likely to be some geometries for which this approach would not be viable, in particular streets that point directly at receiver stations.

Monte Carlo analysis was also undertaken that suggested that the average power used in studies could be reduced further to take account of time of day variation of traffic.


8 MITIGATIONS This section describes mitigations that could be employed to facilitate operation of mobile network base stations within parts of C-band.

Mitigation is discussed in the context of:

Changes required to mobile networks

Changes required to satellite Earth stations

Changes required to fixed links

Regulatory approach to mobile licensing

Frequency or geographic migration

8.1 Mobile Network Based Mitigation

The following mitigations were considered during this study:

Traffic management, including time of day profiles, indoor operation and deployment density

base station antenna performance

base station deployment

These are discussed in the following sub-sections.

8.1.1 Traffic / Coverage Management

During the high resolution analysis consideration was made of the impact of the time of day variation of traffic carried by a mobile network.

It was noted that the EIRP levels used in the ITU-R JTG 4-5-6-7 studies were based upon the busy hour only. However, the interference threshold is averaged over the whole year.

Therefore the average EIRP should take account of low traffic times of the day, such as early morning. An example traffic model was identified that would reduce the average EIRP by 2.3 dB (see Section 7.5). Other diurnal models may be available, but it is certainly clear that JTG have over-estimated the EIRP level to be used.

There is also significant location variation in traffic carried by mobile networks.

One of the key assumptions was that this band would be used for small cell deployment, primarily aimed at urban and dense urban locations. This in itself brought significant advantages in all three of the analysis phases in that the base station was below the clutter line and hence in most cases the interfering signal was reduced by either clutter or diffraction.

Consideration was also made in the high-resolution analysis of the ratio of small cells to macro cells. Interference constraints made it increasingly difficult to deploy additional base station within the area around the test satellite Earth station, as shown in Table 8-1 below.


Scenario 1 small cells per

macro cell

2 small cells per

macro cell

3 small cells per

macro cell

Omni Antenna 20 out of 25

80 %

37 out of 50

74 %

50 out of 75

66.7 %

Directional Antenna 24 out of 25

96.0 %

45 out of 50

90 %

67 out of 75

89.3%

Table 8-1: Active Base Stations that can be Operating while Meeting Satellite Earth

Station I/N Threshold

As the density increases, the ratio of the worst single entry interferer to aggregate interference increases. It reaches 11 dB for the omni antenna case and 8.9 dB for the directional antenna. This means a larger exclusion zone is required around the Earth station.

Another deployment option is suggested by the fact that a significant reduction in interference would occur if the band were used solely for indoor base stations. This is a less attractive option for the mobile operator as it would involve significant constraints on the service.

Reducing the traffic carried by C-band mobile network base stations would decrease interference but would similarly reduce the value of the band to mobile operators. However, analysis undertaken in this study suggests that a package of mitigations (such as the base station deployment option discussed below) would allow 3 small cells per macro cells to operate with a small exclusion zone.

8.1.2 Antenna Performance

There are a number of options to modify base station antenna performance to support interference mitigation including:

Antenna downtilt

MIMO / beam forming

Use of multiple sectors, sector planning and sector disabling

MIMO antennas, beam forming and sector disabling are all examples of how detailed design can be used to concentrate radiated energy towards the intended users. Theoretically this should improve sharing significantly in some cases, but relies on specific detail of the deployment. In particular, these techniques are more applicable for macro base stations than small cells which typically use a single sector.

The high resolution analysis considered two antennas, the baseline omni antenna and a directional antenna using manufacturer’s measured data.

The measured directional antenna could be used to point along a street or at a traffic hot spot such as stadium. It is small enough to be deployed on street furniture. The benefit for sharing is that it can be pointed away from a specific victim in both azimuth and elevation (i.e. downtilt). The increased directivity also meant that the far off axis gain was lower than the omni case, decreasing the gain towards the victim.


In the satellite Earth station case, detailed analysis showed only a sub-set of base stations within the deployment zone need be switched off to reduce the exclusion zone from 3.28 km2 to 0.91 km2. This could be improved further by combining the pointing selection with deployment, as discussed further in the mitigation option below.

There was a similar improvement for the fixed link case, with only a handful of base station in the excluded locations where they would have to be switched off, shown in figure 8-1 below. There was a similar reduction in the exclusion zone size, from 77.5 km2 to 18.2 km2.

Figure 8-1: Excluded Base Station Locations – Directional Antenna

8.1.3 Base Station Deployment

The majority of this study was undertaken using a 50m terrain and land use database that made assumptions about clutter loss in the direction of the victim. In the high resolution analysis in Section 7, use was made of a surface database that could identify the impact of deploying base station at specific locations. The analysis focussed on urban and dense urban locations where


small cell base stations were likely to be deployed where there was also likely to be significant building diffraction loss.

It was found that even within the interference zones identified in Section 4 there was significant potential to deploy base stations if the locations were selected to ensure there was a high diffraction loss in the direction of the victim satellite Earth station or fixed link.

For example, the area around the central London VSAT Earth station was analysed under the assumptions in Table 8-2 and locations where deployment of mobile network small cell base stations would not be feasible were calculated, as shown in Figure 8-2.

The analysis also considered the reduction in the interference zone to include in the analysis two potential mitigations: time of day variation and average polarisation discrimination totalling 3.8 dB.

Average transmit power of small cell base stations -19 dBW / MHz

Antenna pattern of small cell base stations Omni

Peak gain of small cell base stations 5 dBi

Threshold I/N at Earth station -10 dB

Aggregation factor 10 dB

Adjusted threshold I/N -20 dB

Table 8-2: Parameters for Deployment Exclusion Zone Analysis

Figure 8-2: Deployment Exclusion Zones for VSAT / Permanent Earth Station Case

Key:

Red: locations where I/N would exceed threshold even with use of mitigations


Yellow: locations where I/N would be less than threshold taking into account 3.8 dB of mitigation

Similar analysis was undertaken for the BT Tower fixed link case as shown in Figure 8-3.

Figure 8-3: Deployment Exclusion Zones for Fixed Link Case

It was observed that in both cases:

Deployment was difficult very close to the satellite Earth station or fixed link receiver (under a kilometre) or in open spaces such as parks (e.g. Kensington Gardens/Hyde Park for the central London VSAT case).

Deployment was extremely difficult in streets pointing directly at the satellite Earth station or fixed link receive station (e.g. the A400 or Hampstead Road which points directly at the BT Tower).

In most other cases there were locations available that could be used to deploy small cell base stations (e.g. roads on the map not shaded in red).

Even though the locations in Figures 8-2 and 8-3 would be identified as unavailable if using terrain data and larger pixels, high-resolution analysis such as this suggests that small cell base stations could be deployed at 80 – 90% of positions. This included indoor locations. Further work would be required to identify the breakdown solely for outdoors.

This could be considered a constraint, in that in many cases, deployment could only occur if the base station was located on certain sides of streets but not others. However, it can also be considered a mitigation, as using this technique it was possible to operate small cell base stations very close to the victim station without causing harmful interference.


8.2 Earth Station Mitigation

The following mitigations were considered during this study:

Introduce site shielding around the Earth station

Increase the size of the antenna

Under existing licensing arrangements, both of these would most likely require agreement from the permanent Earth station operator and involve additional costs. They were assessed in terms of the technical impact on the exclusion area around the Earth station.

8.2.1 Site Shielding

Recommendation ITU-R SF.1486 suggests values of site shielding in the range 2 - 33 dB considering a combination of natural and artificial shielding and by judicious choice of a ground location. In Section 12.3.7 we have considered a value of 15 dB additional shielding (close to the median suggested by Rec. SF. 1486) and calculated the average excluded area.

Table 8-3 shows the excluded area in square kilometres, when considering omni directional IMT base stations. Results are given for the cases where there are 1, 2 and 3 small cells per macro cell.

Scenario 1 small cell per

macro cell

2 small cells per

macro cell

3 small cells per

macro cell

No site shielding 1.19 2.67 3.28

15 dB additional site

shielding 0.04 0.09 0.11

Table 8-3: Average Area Excluded with 15 dB Site Shielding (km2)

If such a shielding isolation is taken into account, up to the 33 dB suggested by Rec. SF. 1486, then the required separation distance to protect satellite Earth station receivers from IMT transmitters can be reduced even further.

However, the required distance separation between IMT transmitter and a receiving Earth station using site shielding has to be evaluated on a site-by-site basis and is dependent on characteristics and location of each site. The possibility of applying site shielding is not guaranteed for all sites.

8.2.2 Earth Station Antenna Upgrades

It is always possible to improve a sharing scenario by upgrading antenna performance for any directional links in the scenario. In the case of the Earth station analysis a larger dish improves the margin in the satellite link and this extra margin can be in theory be allocated to additional interference from IMT.

Though we might expect a larger dish to result in a smaller link temperature and hence a more sensitive link, manufacturers data indicate that this is a minimal effect at 10, 20 and 40 degree reference elevations.6

6 http://www.antesky.com/products/9m-earth-station-antenna.html

http://www.antesky.com/products/9m-earth-station-antenna.html


The high-resolution analysis in Section 12 shows the impact of replacing a 2.4m dish with a 3 m dish – a scenario relevant, for example, to VSATs in urban areas. The results are summarised in Table 8-4 below.

The table shows the excluded area in square kilometres, when considering omni directional IMT base stations. Results are given for the cases where there are 1, 2 and 3 small cells per macro cell.

Scenario 1 small cell per

macro cell

2 small cells per

macro cell

3 small cells per

macro cell

2.4 m satellite Earth

station dish (current size) 1.19 2.67 3.28

3.6 m satellite Earth

station dish (upgrade) 0.17 0.31 0.47

Table 8-4: Comparison of Area (km2) Excluded around the VSAT Site when using a

2.4m Dish Compared to a 3.6m Dish

8.3 Fixed Link Based Mitigation

The geometry involved makes it harder to employ interference mitigation techniques for the fixed link case because:

It is less practicable or beneficial to add site shielding to sites such as the BT Tower. In the direction in which the antenna points there must be a clear line of sight in order to provide the wanted service. In other directions there will be attenuation of interference due to the gain pattern without the need for site shielding.

Using a larger antenna would improve the wanted signal but also the interfering signal. There would be some benefit due to relative reduction in the noise, but the benefit would be less than for the Earth station case.

The geometry involved is shown in Figure 8-4.

Figure 8-4: Difficulty of Mitigation for Fixed Link Receiver

Earth Station

Base Station

No potential for site

shielding

Larger Earth station

antenna increases

wanted signal but not

interference

Larger fixed link antenna

increases both wanted and

interfering signals

Fixed Link

Receiver

Site Shielding


Relocation of some fixed link receivers is also a potential mitigation, discussed as an important option below in Section 8.5.

8.4 Interference Constraints in Mobile Licence

It was noted that for deployments of fixed links and satellite Earth stations in urban areas it is still feasible to locate small cell base stations close by as long as there is shielding in the form of a building to provide diffraction loss. This means that it could be difficult to define an exclusion zone simply via a distance.

One option could be to define a coordination contour based upon analysis using for example, terrain plus land use data. However, this could lead to a regulatory burden on the mobile operator given the number of base stations that will need to be deployed.

An alternative would be to specify in the mobile operator’s licence that they must ensure that the aggregate I/N at a specified number of fixed link and Earth stations is within a defined threshold. The mobile operator would then have the flexibility to:

Deploy base stations

Relocate base stations

Balance density with how close to the victim station deployment is feasible

Identify the best combination of locations to provide their customers’ service

With this framework the mobile operator would be incentivised to undertake the additional work to identify those locations where there is sufficient diffraction that the fixed link or satellite Earth station would be protected.

The mobile operator would also have access to high-resolution databases identifying buildings etc. in urban areas plus know what traffic hot-spots they wish to serve. The methodology in this study could be the basis of a sharing algorithm which could be published and agreed in the same way that the 3G and 4G coverage obligations were documented.

8.5 Frequency or Geographic Migration

Another mitigation method would be to re-locate the satellite Earth station or fixed link to either an alternative geographic location or different frequency band, as discussed below. This could be encouraged by use of a pricing mechanism as discussed in Section 8.5.3 or be part of a band segmentation regime as discussed in Section 8.5.4.

8.5.1 Earth Station Migration

The principle market for mobile networks in this band is likely to be dense urban locations, and geographic separation can be increased by ensuring satellite Earth station are sited in remote rural areas. In some circumstances, this could require re-location, the difficulty of which would depend upon the user type. For example:


The VSATs in central London can be assumed to be fixed locations with no opportunity to be moved.

The Chalfont Grove site involves a large number of satellite Earth station antenna, representing a significant investment. For example, in the data provided by Ofcom, 8 antenna at this site were identified as operating at C-band.

It is technically feasible that even a large teleport such as Chalfont Grove could be relocated, though this would also involve associated infrastructure being moved (e.g. connecting fibre, control stations etc.). Industry sources have suggested a cost of £15m, which would need to be compared with the value of the spectrum released.

There is also the potential in some circumstances to move to alternative, higher frequencies, though again there could be limitations. For example:

If the band is being used for telemetry, tracking, and command (TT&C) for existing satellites it will not be feasible to move to alternative bands – as TT&C systems on the satellite cannot be re-tuned. However in these cases it could be feasible to move operation geographically to more remote sites.

There could be constraints at the satellite dictating the bands it can use to provide services. For example it is possible that the uplink is at a location where C-band is required and the satellite used requires the downlink also to be in C-band, in particular for international services.

If very high availability is required then this generally implies use of lower frequencies such as C-band where the rain fade is lower. In particular, if the target satellite is at a very low elevation angle, then the rain fade can become excessively large at higher frequencies bands, e.g. Ka band. This can also be driven by fade on the uplink which may be outside of the UK.

However, migration in frequency of some satellite communication services should be feasible if there is sufficient time to identify technical solutions including transponder availability, though there are likely to be cost implications.

8.5.2 Fixed Link Migration

The fixed links were found to create greater constraints on the deployment of mobile network small cells base stations than Earth stations due to their larger interference potential and the number located in dense urban areas. In theory, there is the possibility for migration of these links to higher frequency bands using one of two methods:

In dense urban areas there is high availability of optic fibres, which could be used to provide the required connectivity.

In other locations it could be feasible to create the same connections by moving to higher frequencies where hop lengths would be shorter but using additional hops.

In practice, there could be resistance from existing licensees to this migration due to their requirement for low latency links. The original motivation for them


selecting C-band for these point to point links was that the path length was long, reducing the need for additional hops that could increase delay. In addition, wireless services were selected over wired due to the need for low latency. If this requirement continues, then alternative low latency spectrum outside C-band would need to be found to incentivise migration.

The other category of fixed link was to provide connectivity to the Scottish islands. Here the key requirement is path length, which can exceed 80 km for the more remote islands such as the Shetlands. In this case it would not be feasible to move to higher frequencies, but this is unlikely to constrain development of mobile networks in this band due to the lower traffic levels in these locations.

8.5.3 Pricing Mechanisms

Migration could be encouraged via a spectrum pricing mechanism. Spectrum regulators have the job of balancing conflicting requirements from multiple stakeholders, and one solution is to define a framework that aims to optimise economic spectrum efficiency. One of the key tools in this framework is price, which applies to fees set for:

Licences, for example for fixed links or transmit satellite Earth station.

Recognised Spectrum Access (RSA), for example for receive satellite Earth station.

Factors that can be included in pricing strategies are the demand for spectrum, density of deployment and alternative uses. In particular, pricing can take account of the spectrum opportunity cost of one service denying access to another. This cost can be quantified by considering the net benefit that would be gained by a service for it having access to additional spectrum7.

For mobile services, the benefit of access to spectrum can be very large, and so bands that could be used for mobile services have high valuations. In particular, valuations for mobile spectrum typically are significantly higher than that for bands used by satellite applications or most fixed links. Therefore, it could be argued that the opportunity cost of C-band should be taken into account when determining the prices of site licences for satellite Earth station and fixed links. This approach could be used to encourage migration of incumbent services (location or frequency), as discussed above.

A pricing mechanism would likely have to reflect the differing value of spectrum in urban and dense urban areas compared to other locations. The economic spectrum opportunity cost of a fixed link in central London will be greater than that of the equivalent link in the Highlands and Islands of Scotland. It may also need to consider the type of use of the service, as some fixed link uses may be higher value than others (e.g. low latency trading links in London and across the south coast).

However, it is noted that the motivation for migrating the incumbent is largely based on wider social economic arguments i.e. that the new service adds more value to the UK economy. Hence spectrum pricing would allow a balanced approach which is able to take account of these considerations:

7 We note that Ofcom published its approach to spectrum pricing in 2010.


For fixed links: if the economic benefits due to low latency links exceed the benefit of mobile applications, then the licensees will continue to operate in this band. If not they will be motivated to move to other frequencies or technologies (such as fibre).

For satellite earth stations: similarly, if the economic value of using existing satellites and infrastructure exceeds the cost of migrating (either to a new site location or frequency band) then they would be prepared to pay the additional costs.

If there were a price structure that takes account of location, e.g. charging greater amounts for urban and dense urban locations, then this could incentivise site migration to other locations. The area denied to mobile services calculated using the methodologies described in this report could be used to derive the true spectrum opportunity cost to other services.

The fixed link and satellite Earth station licensee have the option to trade their licence to the mobile operator, which would effectively remove that constraint.

8.5.4 Band Segmentation

Frequency or geographic migration could be employed as part of a band segmentation policy. Band segmentation as a mitigation technique would rely on:

1. Neither sharing service requiring use of the full band for operation

2. Feasibility of operation with a small frequency separation.

This study did not investigate the spectrum requirements for satellite Earth stations or fixed links.

However, we have shown in Section 6 that net filter discrimination can give 23.5 dB advantage in sharing with fixed links and 9.5 dB when sharing with satellite Earth stations. The analysis in Section 6.3 suggests that this should be sufficient to permit operation in adjacent bands with minor constraints very close to an Earth station.


9 CONCLUSIONS AND RECOMMENDATIONS

9.1 Conclusions

The aim of this study was to develop and assess the potential for sharing in C-band between incumbent users such as fixed links and satellite Earth stations and mobile services, in particular IMT-A.

9.1.1 Results of Analysis

As part of this project, Transfinite undertook three levels of analysis:

Spectrum Availability Analysis

Interference Zone Analysis

High Resolution Analysis

These are discussed in the following sections.

9.1.1.1 Spectrum Availability Analysis

The principal conclusion is that there is scope for sharing spectrum in this band. The reason we believe this is that, even in the baseline case, 80% of the spectrum is available to 50% of the urban population – which represents a massive potential economic value.

Half the existing spectrum is available to 65% of the urban population, and this increases to around 90% if 20 dB of mitigation is applied.

On the other hand, even on the application of 20 dB of mitigation, potential interference cannot be ruled out in some populous areas at all frequencies.

Whether 20 dB mitigation is possible in all cases is not clear, but our simulations indicate that improved modelling based on higher resolution surface data could easily find an extra10 dB.

The implication is that a managed approach to shared access of the band based on geographic sharing has great merit. Spectrum is available but the possibility of interference remains in some locations.

It was also important to quantify the effects of mitigations. These included, for example, the additional losses due to accurate local clutter modelling, large antenna elevations in urban areas and building penetration losses.

To generate flexible outputs and avoid having to explicitly model each possible combination of multiple mitigation techniques, our approach was look at relaxing the I/N threshold 5, 10 and 20 dB. This is an established practice in satellite Earth station coordination, where the generation of ‘auxiliary contours’ is common.

The primary numerical result of the study is the amount of spectrum available in areas of high population density, under the different assumptions.

The figure below shows a CDF of the availability of spectrum across the UK by percentage of population in urban, dense urban and hotspot areas.


Figure 9-1: Availability of Spectrum in 3.6 – 4.2 GHz band in MHz by Percentage of

Urban+ Population under Baseline Assumptions

Detailed analysis presented in summary in Section 7 and in full in Section 12 shows that various mitigations can be applied in many cases. To see some idea of the potential impact, Figure 9-2 shows the spectrum available when 5, 10 and 20 dB of mitigation is applied to the baseline case. Further informamation on the impact of mitigation can be seen in Figure 9-3 below.


Figure 9-2: Availability of Spectrum in 3.6 – 4.2 GHz Band in MHz by Percentage of

Urban Population under Baseline Assumptions and with 5, 10 and 20 dB Mitigations

applied

9.1.1.2 Interference Zone Analysis

In the analysis phase of the project, interference zones around specific Earth station and fixed link receivers were developed to gain an understanding of the issues involved. It also allowed rapid analysis of what-if cases and to cross-check the outputs of the spectrum availability analysis.

The satellite Earth station analysis was based around the Chalfont Grove site. A range of scenarios were modelled including the JTG generic case, inclusion of terrain, addition of clutter loss via local clutter codes and mitigations that are derived from the detailed analysis.

The fixed link analysis was based around several sites in the South East and a similar range of analysis was performed.

The analysis also considered the effect of operating non-co-frequency via use of the net filter discrimination and multiple carriers.

It was noted that:

The area excluded due to the fixed link was greater than that required to protect the Earth station.


The fixed link interference zones also tend to cover more populated areas than the satellite Earth station – greatly increasing their impact on spectrum availability per head of population.

Assuming 20 dB of mitigation removed most of the interference zone around the Chalfont Grove site.

The net filter discrimination for the satellite Earth station case was significantly less than that for the fixed link receiver, leading to greater potential for interference in the non-co-frequency case. However, even for the fixed link, the out of band interference cannot be neglected.

9.1.1.3 High-Resolution Analysis

The basis of the high-resolution analysis was a selective qualitative analysis using a 3m resolution surface database within central London. We consider this representative of the type of high density urban areas where mobile networks are likely to be deployed.

From the assignment database provided by Ofcom the following were selected for high-resolution analysis:

Earth station: VSAT based in central London

Fixed link: BT Tower, connected to the LSE

The number of base stations that could be deployed for the Earth station case is given in Table 9-1.


macro cell

2 small cells per

macro cell

3 small cells per

macro cell


80 %

37 out of 50

74 %

50 out of 75

66.7 %


96.0 %

45 out of 50

90 %

67 out of 75

89.3%

Table 9-1: Active Base Stations that meet Earth Station I/N Threshold

It was noted that:

It became increasingly hard to deploy small cell base stations as the density increased due to interference aggregation effects.

Sharing was facilitated via use of a directional antenna that could have higher discrimination towards the Earth station / fixed link receiver.

It was in general harder to share with the fixed link than the Earth station due to the geometry involved, as shown in Figure 1-4.

A number of possible mitigations were considered, including:

Analysis of traffic profiles and polarisation in Section 7.5 suggested an average attenuation of interference of 3.8 dB could be used.

Use of a larger dish antenna or site shielding were found to be effective ways of facilitating sharing with the satellite Earth station, as discussed in Section 12.3.7. It was in general harder to use these mitigations for the fixed link.


There was in general a significant attenuation of interference due to the combined diffraction over buildings and the relative gain of the small cell base stations antenna of around 50 dB.

With a dense deployment of small cell base stations close to the fixed link or Earth station receiver, there could be significant aggregation effects, with 10 dB observed.

However, the net effect was sufficient in many cases to permit operation of small cell base stations close to the receivers.

A key factor was the site chosen for each small cell base stations and in particular the geometry of the path to the Earth station or fixed link receiver. Locations where there was line of sight so that there was no significant diffraction, would not be usable sites for small cell base stations. These locations were identified for the two tests cases described in Section 7 and shown in Figure 8-2 (for the Earth station) and in Figure 8-3 (for the fixed link).

It was noted that in both cases unless very close to the base station there was usually the option to deploy a base station if its location could be selected, in particular:

Not on streets pointing towards the victim receiver;

On the side of streets closer towards the victim receiver to maximise diffraction loss.

9.2 Recommendations

This project has extended, in various dimensions, the work undertaken and methodologies used at international forums such as the ITU-R by taking into account actual assignments and a high-resolution analysis of dense urban deployments. This more detailed approach generated results that suggests that there is a greater potential for use of this band by mobile networks than would be identified using generic low-resolution studies.

The work, however, also raised issues that would benefit from further study, including those described below.

9.2.1 Thresholds

The analysis was undertaken as agreed with Ofcom using the long-term threshold. However, work within JTG 4-5-6-7 suggested that short-term threshold could be more sensitive, leading to some very large minimum separation distances.

It would be beneficial to consider further the short-term interference threshold, noting that there are differences between the study approach described here and that within the JTG. In particular:

The JTG analysis was mostly based upon use of macro-cells (higher power and above the clutter line) rather than small cells (lower power and below the clutter line).

Our analysis is therefore concentrated on relatively short separation distances and short interference paths.

For short paths some propagation modes of Recommendation P.452, such as ducting and troposcatter are negligible. Whereas on longer


paths there is potential for atmospheric ducting to greatly enhance the interfering signal.

9.2.2 Scope and Limitations of Analysis

The analysis covered a range of scenarios. It concentrated on the most likely mobile deployment options and focussed on long term sharing criteria.

We identified a number of mitigation techniques and related these to a general relaxation in the I/N thresholds.

The results give a good characterisation of the sharing issues and a large amount of background data is available to inform strategic planning for this band.

However, there are a number of ways in which the analysis could be extended and improved:

Detailed modelling of alternative deployments, for example macro cells in the mobile network.

Examination of additional power and traffic models.

Production of more accurate maps using smaller pixels in the spectrum availability analysis.

Running the spectrum availability analysis with specific mitigations derived from the high-resolution analysis rather than generic attenuations of {5, 10, 20} dB.

Extending the high-resolution analysis to assess more locations and fixed link / Earth station receivers.

9.2.3 Propagation Modelling

Significant differences were noted between the clutter loss model in P.452 and undertaking the same calculation using diffraction for a specific location. There would be significant benefits in further study, potentially including measurement of diffraction loss in dense urban areas.

This could be done by using the fixed link as a reference signal and measuring the attenuation in various stages of shadow behind buildings.

The high-resolution analysis could be extended to generate statistics that could be used in other studies.

9.2.4 NFD

The NFD for the satellite Earth station case was low due to assumptions about the receive filter. There would be benefits in studying this further to identify if this was a conservative assumption, for example using alternative filters or using measured data.

9.2.5 International Support

It would be useful to build international support for a more detailed approach that takes into account actual assignments and high-resolution surface databases.


This could be done by developing the work in this study into a series of papers that could be forwarded to international meetings including CEPT / ECC or ITU-R as appropriate.

9.2.6 Pricing

Given that the band could be used for mobile applications, the area denied and area type (urban / dense urban) could be the basis of revised pricing.

Issues regarding the pricing of licences and recognised spectrum access (RSA) for assignments in this band are worthy of further study. The methods and results of the analysis presented here would be useful inputs to this study. Unavailable locations for mobile services due to continued operation of fixed link and satellite Earth station licences, would be an important factor in a pricing strategy.

9.2.7 Regulatory Options

The study suggested that one option would be to incorporate in mobile spectrum licences the need to protect existing assignments to a given I/N threshold. The implications of this could be analysed further with feedback from the operators on the operational constraint this would involve.

A key question would be whether the operator could maintain coverage at the required level while meeting the deployment constraint to avoid harmful interference into the fixed link or Earth station receiver. It would also be worth considering this constraint in the context of availability of suitable sites in dense urban areas.

9.2.8 The Impact of Mitigations

The study identified a number of possible mitigations which would require changes to Earth station and fixed link receivers. These could be analysed further with feedback from the licence holders as to feasibility and cost.

Other mitigations are site specific and/or IMT deployment specific so it is not easy to define an optimum set of mitigations that can be generally applied. However, to see the potential effect of applying mitigations we can refer to the Figures (maps and CDFs) in Section 4.

Figure 9-3 below is a close up view of the effect on spectrum availability in the London area in the baseline case and the cases where 5, 10 and 20 dB of mitigation are applied.




Figure 9-3: The Available Spectrum in London in the Baseline Case and with 5, 10 and

20 dB of Mitigation, in 3.6 - 4.2 GHz Sharing will all Satellite Earth Station and Fixed

Link Carriers


10 ANNEX: FIXED LINKS INTERFERENCE ZONE ANALYSIS This section sets out some supplementary technical information related to the Interference Zone analyses for fixed links described in Section 5.

10.1 Single-Entry Interference

Figure 10-1 illustrates the single-entry interference modelled at each pixel. Here, the entire bandwidth of the 30 MHz fixed link receiver is populated with 10 MHz IMT interferers. Hence, in these analyses, single-entry interference is defined as multiple interfering signals sourced from a single location.

Figure 10-1: Interference from IMT

In the simulations, we have considered interference sourced from, and incident to, any 1 MHz of bandwidth where the IMT interferer and the fixed link receiver are co-frequency.

10.2 Transmitter Power

Table 10-1 illustrates the derivation of IMT transmitter output power in 1 MHz of bandwidth.


tx power in 10 MHz 24 dBm

tx power in 1 MHz 14 dBm

Activity Factor 3 dB

adjusted tx power in 1 MHz 11 dBm

adjusted tx power in 1 MHz -19 dBW

Table 10-1: Transmitter Power

Here we take the IMT transmitter operating in 10 MHz bandwidth as a reference point and adjust the power for 1 MHz of bandwidth taking account of the activity factor.

10.3 Receiver Interference Threshold

The fixed link protection criterion of -12.2 dB is discussed in section 3 of this report. Applying this ratio to the total noise threshold N = -121.8 dBW specified in Ofw446 delivers the single-entry interference threshold I = -134 dBW used by Ofcom in its frequency assignment procedures. Table 10-2 shows the adjustments made for a receiver operating in 1 MHz of bandwidth.

Three 10 MHz IMT interferers

30 MHz fixed link receiver



Total noise threshold in 30 MHz -121.8 dBW

Total noise threshold in 1 MHz -136.57 dBW

NI / -12.2 dB

Single -entry threshold in 1 MHz -148.77 dBW

Table 10-2: Single-Entry Threshold

The single-entry interference threshold of -148.77 dBW/MHz is used to define the results of the fixed link area analyses. An IMT Base Station is positioned in each pixel covered by the analysis and interference calculations performed. If the interfering signal power incident to the fixed link receiver exceeds -148.77 dBW, the pixel is coloured red, otherwise the pixel is not coloured.

10.4 Antennas

As discussed in section 3, for the outdoor Base Station runs, a typical Base Station antenna was sourced for the IMT interferer with a peak gain of 5 dBi.

A simple omnidirectional antenna was deployed for the indoor Base Station runs.

The fixed link antenna pattern used in these area analyses was sourced from Ofcom data. All of the fixed links identified in the minimum run schedule are equipped with antenna A/04/H/00/016/AA with a peak gain of 35.1 dBi. The antenna pattern is illustrated in Figure 10-2.

Figure 10-2: Fixed Link Antenna Pattern


11 ANNEX: NFD AND SPECTRUM MASKS In this section of the report, we set out some supplementary technical material on net filter discrimination (NFD) and spectrum masks.

11.1 Net Filter Discrimination

The ETSI Technical Report ETSI TR 101 854 sets out a well-established method for calculating NFD where spectrum masks associated with the victim receiver and interfering transmitter are convoluted in frequency; this method is used by Ofcom in its frequency assignment and frequency coordination work.

The method samples spectrum masks associated with the victim receiver and interfering transmitter co-frequency and the samples are summed. The process is then repeated with the interfering transmitter tuned to the desired frequency offset. Then the ratio of these two sums is obtained and expressed in decibels. Equation 3-1 captures the method:

)(

10

10

log101

0

10/)(

1

0

10/)(

)(

dBNFDni

i

RT

ni

i

RT

ioffseti

ii

Equation 11-1: Net Filter Discrimination

Where Ti and Ri are the i-th samples from the co-frequency transmitter and receiver masks respectively and Ti(offset) is the ith sample from a transmitter mask offset in frequency from the victim receiver.

11.2 Spectrum Masks

ETSI specifies spectrum masks for fixed link transmitters and, although receiver masks are not standardised, there is a well-defined method set out in ETSI TR 101 854 for deriving these from the transmitter mask.

Figure 11-1 shows the fixed link spectrum mask associated with the radio system considered in our analyses. In general, the masks extend five times the channel bandwidth of the radio system; 2.5 times channel bandwidth either side of the carrier centre frequency.

The IMT transmit spectrum mask was sourced from Section 3.1, Annex 17 of the JTG Chairman’s Report which specifies the adjacent channel leakage ratio (ACLR) associated with these radio systems. The mask was constructed such that the out of band (OOB) domain was consistent with the Ofcom methodology. Figure 11-2 shows the resulting IMT spectrum mask.


Figure 11-1: Fixed Link Spectrum Mask

Figure 11-2: IMT Spectrum Mask


12 ANNEX: HIGH RESOLUTION ANALYSIS

12.1 Overview

One of the key challenges in undertaking interference analysis is to balance the need to protected incumbent services without being over conservative by taking a series of worst-case assumptions. One way to facilitate sharing is to use more detailed models as this can reduce the number of assumptions that are required.

The following approaches to modelling propagation paths can be considered to be increasing in detail:

1. Smooth Earth, no terrain or clutter

2. Use of a terrain database

3. Use of terrain and land use database

4. Use of a surface database

The majority of the study was undertaken with the third of these approaches, as this was the most detailed level information available on a UK-wide basis. However for central London the project team had access to a higher resolution 3m surface database, as described in Section 12.2.

This surface database was used to analyse a small number of cases in high-resolution, considering the impact of needing to protect existing fixed link or Earth station receivers on the ability of an mobile networks operator to deploy small cell base stations in a dense urban environment.

12.2 Propagation and Surface Data

12.2.1 Databases

As far as possible, our analysis for this study took into account the actual sharing environment, including UK specific terrain and clutter. Therefore, rather than making worst case assumptions such as smooth Earth, the analysis was based upon terrain and surface databases for the areas where satellite Earth stations are located. The following databases were available:

Ofcom’s standard 50 m terrain and land use code database

High-resolution 3 m surface database of central London

The following figures show central London in each of these databases where the height scale for the terrain and surface data is as in Figure 12-1.


Figure 12-1: Height Scale Used with Terrain and Surface Data

Figure 12-2: 50 m Terrain Data of Central London


Figure 12-3: 3 m Surface Database of Central London

Figure 12-4: 50 m Land Use Data of Central London


12.2.2 Propagation Models

These databases were used as inputs into the propagation models, in particular Recommendation ITU-R P.452: “Prediction procedure for the evaluation of interference between stations on the surface of the Earth at frequencies above about 0.1 GHz”.

This model, to which the UK has contributed both theoretical models and measurement data, is well established and used both UK-wide and internationally. It includes a number of modes within the core model, such as:

Line of sight

Diffraction

Surface ducting

Tropospheric scatter

Elevated layer reflection and refraction

These various components are selected based upon a check on whether the path is line of sight or not, using a path profile created from a terrain or surface database. The relevant terms are then merged mathematically to generate a path loss.

The model then defines how the path loss can be adjusted to include a height gain variation due to clutter. This requires an additional land use database to be available and for there to be a mapping from each land use code to the parameters required by P.452’s clutter model. For the Ofcom land use database these are as given in Table 12-1.

If a surface database is used then it is not necessary to include the clutter loss as that will be calculated in the P.452 path loss using the diffraction model.

Note that the core propagation model in P.452 has been extended:

Into the point-to-area model P.1812 by including a location variability term (typically log-normal with standard deviation e.g. 5.5 dB). A specific variation on P.452 is that P.1812 includes the clutter height on top of the terrain height when deriving the path profile.

Into a generic wide ranging propagation model applicable for Monte Carlo analysis in P.2001 by including fading terms.


Clutter type Nominal height, ha (m) Nominal distance, dk (km)

Undefined 0 0

Open Fields 4 0.1

Main Road 0 0

Buildings 4 0.1

Urban 20 0.02

Suburban 9 0.025

Village 5 0.07

Sea 0 0

Lake 0 0

River 0 0

Coniferous 20 0.05

Deciduous 15 0.05

Mud flats 0 0

Orchard 4 0.1

Mixed trees 15 0.05

Dense Urban 25 0.02

Table 12-1: Land Use Codes and P.452 Nominal Heights and Distances

12.2.3 Clutter and Diffraction Loss

While diffraction and clutter loss models are based upon common concepts, they are implemented differently and this leads to significantly different results. JTG 4-5-6-7 Document 715 Annex 2 relating to IMT parameters stated the following relating to below rooftop base station antenna deployment:

“When conducting sharing studies it is also important to account for how the antennas are deployed in relation to the surrounding environment, including the clutter. If the antennas are deployed below the rooftop level it might be necessary to use a different propagation model compared to the scenario when the antennas are installed above the roof top level. An alternative approach could be to add clutter loss to propagation loss calculations”

The propagation model in P.452 uses the diffraction loss model from Recommendation ITU-R P.526. For a knife edge diffraction of height h at distance d1 from the transmitter and d2 from the receiver, the loss can be calculated using:

𝐿𝑑 = 6.9 + 20𝑙𝑜𝑔 (√(𝑣 − 0.1)2 + 1 + 𝑣 − 0.1)

where, using to denote wavelength:


𝑣 = ℎ√2

𝜆(

1

𝑑1+

1

𝑑2) .

However the clutter loss in P.452 is

𝐴ℎ = 10.25𝐹𝑓𝑐𝑒−𝑑𝑘 {1 − 𝑡𝑎𝑛ℎ [6 (ℎ

ℎ𝑎− 0.625)]} − 0.33

where:

𝐹𝑓𝑐 = 0.25 + 0.375{1 + 𝑡𝑎𝑛ℎ[7.5(𝑓𝐺𝐻𝑧 − 0.5)]}.

These lead to significant different values, as can be seen in Table 12-2.

Obstruction Close Baseline Far

Frequency (GHz) 3.8 3.8 3.8

Transmit antenna height (m) 6 6 6

Obstruction height (m) 20 20 20

Distance to obstruction (m) 2 20 500

Distance from obstruction to receiver (m) 1000 1000 1000

Clutter loss (dB) 19.7 19.4 11.9

Diffraction loss (dB) 46.9 36.9 24.6

Table 12-2: Diffraction vs. Clutter Loss

In particular, the clutter loss is capped at around 20 dB while the diffraction loss can be significantly greater in the right hand column for the case where the transmitter is much closer to the obstruction.

This highlights another difference between using a land use database and surface database: the land use database will always use the same values of distance to obstruction and obstruction height but with the surface database these values will vary depending upon geometry. As the land use database does not know the actual case involved, it must use simplifying assumptions and generate a typical value that might not be applicable for most actual deployments.

In particular, small cell base stations deployed in dense urban areas are likely to use street furniture that are located close to one side or other of a street, as shown in the figure below, leading to cases where diffraction loss will be greater than that predicted by the clutter model.


Figure 12-5: Higher Diffraction than Clutter Model Predictions

Analysis in Section 12.3.4 suggested that the interference can become either:

An aggregate of multiple interferers all significantly attenuated due to large diffraction losses

Dominated by a single interferer that has significantly lower diffraction loss (e.g. due to street being aligned with the victim)

12.2.4 Antenna Gains

Another factor that will have a significant impact on the interference calculation is the gain at the transmit antenna, and this will vary depending upon the terrain or surface database used.

If a terrain database is used then it is likely that for short paths the direct path is used to calculate the transmit gain, but if a surface database is used the radio path can be very different and hence the gain calculated also, as in Figure 12-6.

Figure 12-6: Radio Path vs. Direct Path

This would lead to large differences in the calculated aggregate interference level, particularly if the base station is modelled using measured data from a directional antenna.

12.2.5 Summary

Two mechanisms were identified by which the aggregate interference calculated using a high-resolution surface database could be significantly different from that derived using terrain and land use codes:

Base Station


1. The clutter loss calculation uses fixed parameters and is capped at around 20 dB

2. The transmit gain calculated using a terrain database is likely to use an inaccurate direct path

This suggests that the lower aggregate interference levels calculated using a surface database are based upon real phenomena and can be accepted for use in further analysis.

12.3 Earth Station VSAT Test Case

The previous section identified benefits in analysing sharing between mobile network base stations and incumbent systems using a high-resolution surface database. This section considers the impact on satellite Earth stations, starting with identification of system parameters.

12.3.1 System Parameters

12.3.1.1 IMT Parameters

The study used IMT-A parameters that were agreed for use in sharing studies in JTG 4-5-6-7. As we were concentrating on small cell deployments in urban areas Table 12-3 was extracted from document JTG 4-5-6-7/715 Annex 17 from the Chairman’s report of the final JTG meeting. This Annex is dated 18th August 2014 and is the basis for a Draft New ITU-R Report.

The analysis was undertaken with a reference bandwidth of 1 MHz on the basis that the entire victim Earth station bandwidth would be used for IMT/LTE deployment. The power density of 24 dBm across 10 MHz was a median value averaging across 5, 10 and 20 MHz.

The density of small cell outdoor base stations was derived from:

Small cell outdoor: 2 per urban macro cell

Urban macro cell every 0.6 km

50 small cell outdoor base station were deployed over an area calculated from the above to be a circle of radius 1.69 km based upon the victim Earth station as shown in Table 12-4.


Small cell outdoor JTG Baseline Measured base station

data

Cell radius / Deployment density 1-3 per urban macro cell


site)

1-3 per urban macro cell


site)

Antenna height above terrain 6 m 6 m

Sectorization single sector single sector

Downtilt N/A 5°

Frequency reuse 1 1

Antenna pattern Recommendation ITU-R

F.1336

Omni k = 0.5

Measured data

Antenna polarization linear linear

Below rooftop base station

antenna deployment

100% 100%

Maximum base station output

power in 10 MHz

24 dBm 24 dBm

Maximum base station antenna

gain

5 dBi 9.32 dBi

Average base station activity 50% 50%

Average base station power/ 10

MHz taking into account activity

factor

21 dBm 21 dBm

Maximum base station output

power/sector (e.i.r.p.) in 10 MHz

26 dBm 30.32 dBm

Average base station power / 1

MHz taking into account activity

factor

11 dBm = -19 dBW 11 dBm = -19 dBW

Table 12-3: Parameters for IMT-Advanced Small Cell Outdoor Systems

Macro base station separation distance

(km) 0.6

Number of Small Cell / Macro base

station 2


Area / Small Cell (km2) 0.18

Number of Small Cell in simulation 50



Table 12-4: Deployment Density for IMT-Advanced Small Cell Outdoor Systems

Locations of the 50 small cell base station were randomised within a circle of radius 1.69 km around the Earth station. They were then moved to the nearest


street and for the measured base station data case their antenna was pointed along the street. No attempt was made to analyse interference between base station or the coverage / service provided. The resulting initial deployment locations are shown in Figure 12-7.

Figure 12-7: 50 Small Cell Base Station Located within 1.69 km of Victim Earth Station

The gain pattern for Rec. F.1336 for peak gain of 5 dBi in omni k=0.5 case is shown in Figure 12-8.


Figure 12-8: Rec. F.1336 Gain Pattern Peak Gain = 5 dBi k = 0.5

For comparison, the antenna pattern of a real base station was used. The one selected was:

CommScope CMAX-DM60-CPUSEi53: Cell-Max™ Directional High Capacity Venue MIMO Antenna, 698–960 MHz and 1710–2700 MHz.

It was selected as:

It was small enough to be mounted on a lamp post (30 cm x 30 cm).

The upper frequency band was close to 3 GHz.

The target applications included high density locations requiring some directivity, such as stadiums and traffic hot spots.

The gain pattern was downloaded for 2.7 GHz where the peak gain was 7.18 dBd = 9.32 dBi with patterns as in Figure 12-9 and Figure 12-10. The azimuth and elevation slices were merged together using the smoothing parameter:

𝜆𝐸𝑙 =|𝐸𝑙|

90

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90

Gai

n (

dB

i)

Elevation angle (deg)


Figure 12-9: Measured Azimuth Gain Pattern

Figure 12-10: Measured Elevation Gain Pattern

-40

-30

-20

-10

0

10

20

0 30 60 90 120 150 180 210 240 270 300 330 360

Gai

n (

dB

i)

Azimuth (degrees)

-50

-40

-30

-20

-10

0

10

20

0 30 60 90 120 150 180 210 240 270 300 330 360

Gai

n (

dB

i)

Elevation (degrees)


12.3.1.2 Earth Station Parameters

The parameters for the Earth station (ES) were taken from the data provided by Ofcom. The selection criteria was:

In central London

Operating in the bands targeted for use by mobile networks

Believed to be active and unlikely for its status to change in the medium term

The result was the ES or very small aperture terminal (VSAT) was modelled with parameters in the table below:

FREQUENCY 3.925000 GHz

CHANNEL SPACING 36.000000 MHz

NAME RX STATION LONDON

COORD_LONG 000W1126.674 51N3025.079

EMISSION DESIGNATION 150KG7W

ANTENNA POLARIZATION CR

AZIMUTH 196

ANTENNA ELEVATION 29.5

T/I 10

TRANS. ANTENNA GAIN 36.00

ANTENNA BEAMWIDTH 2.6

VERTICAL BEAMWIDTH 2.6

Table 12-5: Parameters of Victim Earth Station

From these parameters and the project methodology the following simulation and derived values were developed:

Dish size 2.06 m

Height of antenna above building 3 m

Receive temperature 100 K

Polarization Circular

Target GSO satellite longitude -13.5°

Gain pattern Rec. S.580 (ITU-R APL version)

Aggregate I/N Threshold -10 dB

Percentage of time 20%

Table 12-6: Additional Earth Station Parameters

12.3.2 Propagation Modelling

The objective was to analyse in detailing a real sharing scenario to identify how the constraint of protecting a satellite Earth station would restrict a mobile


operator’s ability to deploy base stations. This therefore used a surface database with resolution of 3m, which was sufficient to identify individual buildings and locate base station on streets. The propagation model used was P.452 with an associated percentage of time = 20%.

For these short paths the principle mechanism is diffraction rather than troposcatter, ducting and layer refraction. It is also necessary to consider multi-path effects and reflections, though geometry suggests the likelihood would be low of there being a surface that would reflect energy towards the Earth station:

Figure 12-11: Geometry of Base Station below Clutter Line

A value of 3 dB enhancement was used on-top of the P.452 prediction. It could be worth running measurements to compare predictions using a high-resolution surface database with the P.452 propagation model against actual radiowave behaviour.

Note also that the angle at the base station towards the diffraction point is typically a high elevation angle. This means there is likely to be some antenna discrimination, particularly if the antenna is using some downtilt.

12.3.3 Identify Interfering Base Stations

12.3.3.1 Methodology

The approach taken was to calculate the aggregate I/N at the Earth station. If the I/N was above the required threshold of aggregate I/N = -10 dB then the highest single entry base station would be identified and removed from the list of interferers. This process was repeated until the I/N threshold was just met. In some cases it was observed that minor modifications to the deployment would facilitate sharing, such that:

Two base stations were located on elevated roads (the Westway), and were consequently moved to ground level;

Two base stations were located on streets that pointed at the Earth station and were moved to nearby sites with additional protection;

Five other base stations were moved to increase shielding to nearby locations.

The critical output was then:

Earth Station Base Station

Reflections

Diffraction


The locations of the base stations that would not be feasible (i.e. an interference zone);

The locations of the base stations that would be feasible.

The resulting deployment was then assessed for impact in terms of constraints on the mobile operator’s deployment.

The process was repeated for the two sub-cases:

Omni antenna base stations.

Directional Antenna base stations.

12.3.3.2 Omni Antenna Case

Of the 50 base stations in the initial deployment, 11 had to be switched off to meet the required I/N = -10 dB threshold. However, 39 could continue to operate within the deployment zone, as can be seen in Figure 12-12.

Figure 12-12: Omni Antenna Exclusion Zone

The figure shows a red polygon that contained all the base stations that had to be switched off and the circle of radius 1.69 km within which the 50 base stations (shown as white dots) were deployed.


12.3.3.3 Directional Antenna Case

Of the 50 base stations in the initial deployment, 3 had to be switched off to meet the required I/N = -10 dB threshold. However, 47 could continue to operate within the deployment zone, as can be seen in Figure 12-13, which also shows the red polygon enclosing those base stations (white dots) that had to be switched off.

Figure 12-13: Directional Antenna Exclusion Zone

12.3.4 Analyse Single and Aggregate Interference

12.3.4.1 Methodology

Having identified the set of base stations that would lead to the aggregate I/N = -10 dB threshold being just met, the data was analysed further to derive:

The average in absolute [Grel + Diffraction loss] for each scenario taking into account all 50 possible base stations.

The ratio of worst single entry interference to aggregate interference in the case that the aggregate threshold is just met.

An area analysis showing the exclusion zone taking into account the average in absolute [Grel + Diffraction loss] plus aggregation factor.


From the exclusion zone, the average area that would be inaccessible to mobile network base stations.

This was undertaken for both the omni and directional cases described earlier.

12.3.4.2 Omni Antenna Case

For the omni antenna case the values calculated were as shown below

Average [Grel + Diffraction] 51.7

Single entry to aggregate I/N ratio 10.9

3 dB factor for multi-path enhancements -3

Total adjustment to free space propagation loss 37.7

Table 12-7: Omni Case Adjustments to Single Entry Free Space

The adjustment factor of 37.7 dB was then used to create an average exclusion zone around the satellite Earth station as in Figure 12-14 which also shows the circle around the ES radius 1.69 km within which the base stations were deployed.

Figure 12-14: Average Exclusion Zone for Omni Antenna Case


The exclusion zone was calculated to be an area = 2.93 km2. The exclusion zone is seen to have the classic “key hole” shape pointing in the direction of the Earth station’s satellite (i.e. towards the south-south-west).

12.3.4.3 Directional Antenna Case

For the directional antenna case the values calculated were as shown below:

Average [Grel + Diffraction] (*) 56.6

Single entry to aggregate I/N ratio 7.3

3 dB factor for multi-path enhancements -3.0

Total adjustment to free space propagation loss 46.2

Table 12-8: Directional Antenna Case Adjustments to Single Entry Free Space

(*) For consistency with the omni case, all values of Average [Grel Diffraction] are compared to the case of an isotropic antenna with peak gain of 5 dBi.

The adjustment factor was then used to create an exclusion zone around the satellite Earth station as in Figure 12-15 which also shows the circle around the ES radius 1.69 km within which the base stations were deployed.

Figure 12-15: Average Exclusion Zone for Directional Antenna Case


The exclusion zone was calculated to be an area = 0.41 km2.

12.3.5 Analysis with Variable Base Station Density

The analysis was repeated using an assumption of 1 or 3 small cell base stations per macro cell rather than 2. Initially the analysis considered the higher density case with 75 (corresponding to 3 small cells per macro cell) rather than 50 base stations (corresponding to 2 small cells per macro cell) within the same area of interest as in Figure 12-16.

Figure 12-16: Base Station Locations for Higher Density Scenario

The same process was used as for the 2 small cell base stations per macro cell namely:

Deployment:

Position base station at random within circle.

Move to nearest street.

Make limited adjustments for location (e.g. avoid very low separation distances between base station and relocate some base station within parks).

For the directional case, orientate antenna to point along the street.


Analysis:

1. Calculate aggregate I/N at Earth station from all base stations.

2. If the aggregate I/N > -10 dB then:

a. Identify the worst single entry case

b. Remove that base station from the group of interfering base station

c. Continue at Step 1

3. Output final base station deployment

The link budgets for each of the 75 base stations were then exported to Excel where the data was post-processed to analyse the lower density case. In addition the baseline case of 2 small cells per macro cell was repeated to:

Ensure there was consistency in the deployment between the three densities;

Provide an opportunity to analyse the sensitivity of the initial deployment.

The number of active base stations that meet the Earth station I/N criteria are shown in the table below for the 1, 2 or 3 small cell base stations per macro cell cases.


macro cell

2 small cells per

macro cell

3 small cells per

macro cell


80 %

37 out of 50

74 %

50 out of 75

66.7 %


96.0 %

45 out of 50

90 %

67 out of 75

89.3%

Table 12-9: Active Base Stations that meet Earth Station I/N Threshold

It can be seen that as the number of small cells per macro cell increased, the omni case had difficulty in deploying additional base stations, suggesting it was approaching an interference driven limit. However, there was greater success (89.3 % against 66.7%) in deploying the directional antenna case due to the better antenna discrimination. In addition, there were a couple of cases for the directional antenna where interference could have been avoided by changing its azimuth angle.

The locations of the active and switched off base station for the 3 small cells per macro cell case are shown in Figure 12-17 and Figure 12-18 where:

Base stations that could remain active are shown as white dots

Locations where base stations had to be switched off are shown as blue circles.

Note use of the terrain / surface colour scheme shown in Figure 12-1.


Figure 12-17: Locations of Active and Switched Off base stations for Omni Antenna

Scenario with 3 Small Cells per Macro Cell


Figure 12-18: Locations of Active and Switched Off base stations for Directional

Antenna Scenario with 3 Small Cells per Macro Cell

The degree to which the average [gain + diffraction loss] calculated using this methodology varied by number of small cells per macro cell is shown in Table 12.10 and Table 12-11.

Number of Small Cells per Macro Cell 1 2 3

Average [Grel + Diffraction] 50.6 50.9 51.2

Single entry to aggregate I/N ratio 6.1 9.8 11.0

3 dB factor for multi-path enhancements -3.0 -3.0 -3.0

Total adjustment to free space propagation loss 41.6 38.1 37.2

Table 12-10: Omni Case Adjustments to Single Entry Free Space


Number of Small Cells per Macro Cell 1 2 3

Average [Grel + Diffraction] 53.0 53.4 54.6

Single entry to aggregate I/N ratio 5.1 6.1 8.9

3 dB factor for multi-path enhancements -3.0 -3.0 -3.0

Total adjustment to free space propagation loss 44.9 44.3 42.8

Table 12-11: Directional Case Adjustments to Single Entry Free Space

It was observed that:

There was good agreement in the average [Grel + Diffraction] figure, though it was noted that the same deployment was used in all cases.

The single entry to aggregate I/N ratio gradually increased, reaching around 9 - 11 dB for the 75 base station deployment scenario.

The area excluded using the average values were calculated and observed to increase with the number of small cells per macros cell as in Table 12-12. This is the expected result: the higher the density of base stations the greater the aggregation effect and hence the larger the area that must be excluded to protect the ES.


macro cell

2 small cells per

macro cell

3 small cells per

macro cell

Omni Antenna 1.19 2.67 3.28

Directional Antenna 0.56 0.64 0.91

Table 12-12: Average Area Excluded

12.3.6 Adjacent Band Analysis

In Section 6, analysis was made of the mobile networks transmit mask and receive satellite Earth station filter discrimination. It was noted that if there was no overlap between the wanted carriers of these two systems but minimal frequency separation (i.e. operating in the adjacent channel) then the discrimination available (calculated by integrating the TX and RX spectrum masks) was 9.5 dB. With a co-frequency threshold of I/N = -10 dB this would be adjusted to an adjacent band threshold = -0.5 dB.

In the most demanding case of the 3 small cells per macro cell using the omni antenna, the deployment probability was raised to 72 / 75 or 96%, while for the directional antenna case only a single deployment was infeasible (i.e. 98.7% of deployments feasible).

Given the analysis was based upon a conservative assumption of a Gaussian filter at the Earth station, this suggests that for the scenarios considered there would be no significant constraints in mobile network small cell base stations operating in bands adjacent to satellite Earth station in dense urban environments.

12.3.7 Options for Mitigation

Two mitigations were considered to facilitate sharing:


Changing the satellite Earth station antenna for a larger antenna.

Including site shielding around the satellite Earth station

For the former the impact of increasing the dish size from 2.4 m to 3.6 m was analysed. Assuming the gain pattern in Rec. S.580, the side lobe is defined by the equation:

𝐺 = 29 − 25𝑙𝑜𝑔10𝜗

This is therefore independent of the dish size and hence the interference would not change by increasing the dish size. What such a change would do, however, is improve the wanted signal that would result in an increased interference margin. The principles of the link design and impact of increasing the wanted signal are shown in Figure 12-19.

Figure 12-19: Link Design and Impact of Increasing Wanted Signal

A typical link design is:

Identify the receiver noise based upon kTB.

Include 1 dB of interference margin.

Calculate the target receive signal level based upon the total noise + interference, the C/(N+I) needed to achieve the BER objectives and any other margins.

RSL

N + I(agg)

N=kTB

Aggregate I

Single entry I

Interference margin = 1 dB

I(Agg)/N

Apportionment Rules

Target C/(N+I) + Possibly other margins

C

Increase in wanted signal

Target C/(N+I) + Possibly other margins

N + I(agg)

Aggregate I

N=kTB

Single entry I

Apportionment RulesIncreased

interference margin


From the interference margin the ratio of the aggregate interference to noise can be calculated.

Using apportionment rules, the single entry (service and system) interference levels are calculated.

If the power from the satellite is unchanged but the ES dish size is increased (for example, from 2.4 m to 3.6 m), then the wanted signal will be stronger due to the larger peak gain. If the noise level remains unchanged then this would provide an opportunity to increase the link interference margin while continuing to meet the BER objectives, as shown in the table below.

Dish size (m) 2.4 3.6

Peak gain (dBi) 37.4 40.9

Interference margin (dB) 1 4.5

Iagg/N (dB) -5.9 2.6

Table 12-13: Impact on Iagg/N of Increasing Earth Station Dish Size

It can be seen that increasing the dish size from 2.4 m to 3.6 m suggests that aggregate interference could be increased by 8.5 dB. If it is assumed that the same proportion of the aggregate interference can be used by the mobile networks, that implies there would be the potential to increase the interference threshold from Iagg/N = -10 dB to -1.5 dB. The impact on the average excluded area is shown below.


macro cell

2 small cells per

macro cell

3 small cells per

macro cell



Table 12-14: Average Area Excluded with Additional 8.5 dB Interference Margin

The impact of there being 15 dB of site shielding was also considered and it resulted in significantly lower average excluded areas as shown below.


macro cell

2 small cells per

macro cell

3 small cells per

macro cell



Table 12-15: Average Area Excluded with 15 dB Site Shielding

For the directional antenna 3 small cells per macro cell case, if both mitigations were used the excluded area reduced to 0.0043 km2 allowing average base station deployment to within 100m of the Earth station.

These mitigations would have to be agreed between the Earth station and mobile networks operators but would provide significant potential opportunities to reduce the area excluded.


12.3.8 Summary

The analysis suggests that the exclusion zone around an Earth station where IMT/LTE small cell base station would not be permitted could be small, possibly in the range 0.56 – 3.3 km2 without mitigation.

The small size of exclusion zone is due to the mobile network base stations operating on lower power below the clutter in a dense urban environment where there will be significant off-axis gain and diffraction loss. The zone can be reduced using mitigation methods such as:

Directional antennas at the base station

Reducing the base station height above terrain

Pointing the base station antenna away from the satellite Earth station

Locating the base station in deep clutter maximising diffraction loss

The analysis used the standard ITU-R diffraction model and a high-resolution surface database to generate predicted propagation loss: there would be benefit in measurements to verify this. One limitation in the use of the surface database is that it identifies trees as solid objects to be diffracted over rather than as an attenuating factor.

One possible approach to facilitate sharing of this band by mobile networks would be to include in the licence terms and conditions the necessity of protecting a list of existing satellite Earth station. A suitable threshold would be either:

Single entry I/N suitably adjusted for aggregation

Aggregate I/N threshold

The mobile operator could also offer to the earth station operator:

Site shielding around the earth station;

A larger replacement antenna with higher gain and/or lower far-off-axis gain values

Either of these methods would significantly reduce the average area excluded.

Aggregation interference was observed to be between 9 - 11 dB higher than single entry levels.

The analysis was undertaken for 1, 2 and 3 small cell base stations per macro cell. Similar behaviour was observed in each case, though the omni antenna deployment appeared to be reaching an interference driven limit in the number of base stations that could be deployed.

12.4 BT Tower Test Case

This section describes analysis interference into a fixed link receiver from small cell mobile network base stations in a dense urban environment to identify the degree to which the deployment would be constrained by its presence. The objective was to gain an understanding of a single specific sharing scenario located where high-resolution surface data was available by modelling it in detail.


12.4.1 Fixed Links and Locations

The assignment data provided by Ofcom was converted into a Visualyse Professional simulation file to check the data was complete and identify station locations. The resulting simulation file is shown in Figure 12-20.

Figure 12-20: Distribution of UK C-band Fixed Links

It was noted that the deployment was dominated by two markets:

Links connecting the Scottish islands: these benefit from the lower rain fade in C band (though there can be significant multi-path fading) and so can operate longer distances such as across the Minch.

Low latency links, connecting data centres in and around London with international financial markets such as Brussels and to transatlantic cables along the south coast.

There is likely to be low overlap between locations for which LTE / IMT deployment is required and the Scottish islands, and so attention focussed on areas identified in the land use database as:

Buildings


Urban

Dense Urban

These locations are identified in grey in:

Figure 12-21, which also shows links around for London and the South East as lines, connecting fixed link stations between Slough in the west to Basildon in the east, with a spur heading south-east towards the Channel ports.

Figure 12-22 for locations near Manchester and Liverpool, which also shows three stations located between those two cities.

Figure 12-21: Overlap of Fixed Link Locations with Likely London and South East

IMT/LTE Deployment Zones

Figure 12-22: Overlap of Fixed Link Locations with Likely Manchester and Liverpool

IMT/LTE Deployment Zones


In particular, three stations (Royal Free Hospital (to the north), the BT Tower and LSE) were located in central London as shown together with the surface database Figure 12-23. Note that all links in this zone were licensed to a single organisation, namely Optiver Holding B.V. and the colour scheme used for the terrain / surface data is given in Figure 12-1.

Figure 12-23: C Band Fixed Link Stations in Central London

The critical case was considered to be the BT Tower as:

1. It is located at the centre of a dense urban area that would represent a key mobile network market.

2. It is very tall, increasing the difficulty of sharing.

The receive antenna at the BT Tower was therefore used as the basis of the analysis.

12.4.2 System Parameters

12.4.2.1 IMT Parameters

This analysis used the same parameters as given in Section 3 apart from the deployment, which was specified using 100 small cell outdoor base station deployed over an area calculated from the above to be a circle of radius 2.39 km based upon the BT Tower as shown in Table 12-16.


Number of Small Cells / Macro base station 2


Area / Small Cells (km2) 0.18

Number of Small Cells in simulation 100



Table 12-16 Deployment Density for IMT-Advanced Small Cell Outdoor Systems


Locations of the 100 small cell base station were randomised within a circle of radius 2.39 km around the BT Tower. They were then moved to the nearest street and for the measured base station data case their antenna was pointed along the street. No attempt was made to analyse interference between base station or the coverage / service provided. The resulting initial deployment locations are shown in Figure 12-24 as small white dots within the circle of radius 2.39 km around the BT Tower.

Figure 12-24: 100 Small Cell base station Located within 2.39 km of Victim Fixed Link

Station

The small cell characteristics were calculated within a bandwidth of 1 MHz and then scaled to the fixed link receiver’s bandwidth of 30 MHz. This is equivalent to modelling the sharing environment as either:

1. At each location the entire fixed link bandwidth was used to provide mobile networks services. This could be because (for example) the site is a managed resource used by multiple operators or a single operator with access to the full 30 MHz.

2. Each location used just 10 MHz but there were an equivalent set of two x 100 base stations for the other 30 MHz which would average to be the same as for case 1.


12.4.2.2 Fixed Link Parameters

The fixed link parameters were as shown below.

Reference 0979750/1

Licence holder Optiver Holding B.V.

Frequency (GHz) 3.8

Bandwidth (MHz) 30

Transmit station name LSE

Tx longitude (deg) -0.082554722

TX latitude (deg) 51.52032361

Tx height (m) 50

Receive station name BT Tower

Rx longitude( deg) -0.137005278

Rx latitude (deg) 51.52088028

Rx height (m) 50

TX power (dBW) -40.36

TX peak gain (dBi) 35.10

TX beamwidth (deg) 3.0

RX peak gain (dBi) 35.10

RX beamwidth (deg) 3.0

RX feed loss (dB) 1

Polarization H

RX Temperature (K) 1595.9

RX Noise (dBW/MHz) -136.6

Table 12-17: BT Tower Link Parameters

The receive temperature T was converted into noise in the wanted bandwidth = BWHz using:

𝑁 = 10𝑙𝑜𝑔10(𝑇) + 10𝑙𝑜𝑔10(𝐵𝑊𝐻𝑧) − 228.6

This ensured consistency with Ofcom’s planning process defined in TFAC OFW 446.

The baseline runs for the project were agreed with Ofcom to be based upon the standard long-term threshold. However this section considers in detail a specific sharing scenario and examines all assumptions, including issues such as interference apportionment and aggregation issues.

The single entry (single location) threshold was the long term I/N = -12.2 dB not to be exceeded for more than 50% of the time. Most UK fixed links have a receiver sensitivity level (RSL) associated with an interference margin of 1 dB, as is standard industry practice. The interference margin can be converted to an aggregate I/N or DT/T using:


𝐼𝑎𝑔𝑔

𝑁= 10𝑙𝑜𝑔10(10𝐼𝑀/10 − 1)

𝐷𝑇𝑎𝑔𝑔

𝑇= 100. 10(𝐼𝑎𝑔𝑔/𝑁)/10

This implies there is a total of DT/T = 25.9% (here rounded to 26%) to be apportioned to various sources of interference, including:

Other stations of the same service (e.g. other fixed links).

Other existing co-primary services (e.g. satellite downlinks, constrained via the RR Article 21 PFD limits).

Secondary services and those operating in other bands (out of band emissions).

The single entry limit for other fixed links is I/N = -12.2 dB which equates to a DT/T = 6%. Hence, two single entry systems meeting this limit would take 12% of the total 26% available. With 1% each for secondary, OOB and 2% for other contributions, that leaves an aggregate I/N = -10 dB for mobile networks which corresponds to a DT/T = 10%.

Hence, a possible interference apportionment that includes the new service could be as shown below.

Two other fixed links 12 %

Aggregate from mobile networks 10 %

Secondary services 1%

Out of band services 1%

Other 2%

Total 26%

Table 12-18: Interference Apportionment

It should be noted that one method to facilitate sharing is to increase the interference margin to be above the industry standard 1 dB. For example, increasing this to 2 dB would result in a total interference allowance of 58.5%: with the same apportionment to other services this would make the mobile networks aggregate threshold an I/N = -3.7 dB, 6.3 dB higher. Conventionally, this approach would require a corresponding increase in the transmit power of 1 dB in order to ensure the C/(N+I) remains above the threshold for the availability requested. However, that could introduce other burdens, as an increased transmit power would cause an increase in interference into other systems.

An initial assessment was made of the interference environment by calculating the long term aggregate I/N at each of the fixed links from all the others. Links that used dual polarization were excluded due to modelling complexity, and the results on the remaining links are shown below:


Total links 192

I/N not calculated 27

Remaining links 165

Aggregate I/N over -6 dB 15

Aggregate I/N over -12.2 dB 36

Table 12-19: Intra-Service Aggregate I/N

It can be seen that a significant number of links are already accepting higher levels of interference, which could lead to lower availabilities.

Further analysis identified that this was the result of the initial modelling assuming all links were co-polar and hence not including any polarization discrimination. A subset of links were examined in detail and, when the effects of antenna polarization discrimination were included, all of these three had aggregate interference below the threshold:

0979911/1

0980509/2

0980534/2

Therefore, all the links examined were consistent with the Ofcom assignment criteria.

The first of these three cases is shown in Figure 12-25 where it can be seen that there is almost direct alignment between the victim and interfering links, both aiming at the same station.

Figure 12-25: Link 0979911/1 and Worst Interferer Geometry

The antenna code was identified as A/04/H/00/016/AA with gain pattern as in Figure 12-26.


Figure 12-26: Fixed Link Receive Antenna Gain Pattern

12.4.2.3 Propagation Modelling

The same 3m resolution surface database was used as for earlier analysis together with the propagation model in P.452. In this case an adjustment was made to the surface database to remove the BT Tower which would be interpreted (incorrectly) as an obstruction by P.452.

Note that the propagation model was configured with a percentage of time = 50% to be consistent with the fixed link receiver threshold rather than 20% as for the Earth station case. Consistent with the Earth station case, the propagation loss predicted by P.452 was decreased by 3 dB to include multi-path enhancements.

12.4.3 Mobile Networks Omni Antenna

12.4.3.1 Identify Interfering Base Stations

The aggregate I/N at the fixed link receiver was calculated taking into account the 100 small cell base station deployment, and compared against the single service aggregate stations interference threshold of I/N = -10 dB. Initially this threshold was exceeded and so base stations were effectively switched off until the threshold was met. It was required to switch off 6 of the 100 so that 94 remained active. The locations of the excluded base stations are highlighted in Figure 12-27 using the terrain / surface colour scheme given in Figure 12-1.

It was noted that:

One base station was on a street in direct alignment with the BT Tower (Hampstead Road).

-30

-20

-10

0

10

20

30

40

0 20 40 60 80 100 120 140 160 180

Gai

n (

dB

i)

Offaxis angle (deg)

Co-polar pattern Cross-polar pattern


Several of the base station were close to the BT Tower.

All of the remaining excluded base station were to the east of the BT Tower, the direction the fixed link antenna was pointing.

Figure 12-27: Excluded Base Station Locations – Omni Antenna

12.4.3.2 Average Gain and Diffraction Loss

The case in which the small base station is on a street directly aligned with the victim receiver was treated as a special case, and so the average gain plus diffraction loss was calculated for the remaining 99 base stations.

It was determined that the average (in absolute i.e. power terms) was 41.0 dB. This was less than the equivalent for the Earth station case due to the lower path loss to the high fixed link receiver antenna.

The aggregation factor from worst single entry to aggregate I/N was calculated to be 9.1 dB.


12.4.4 Mobile Networks Directional Antenna

12.4.4.1 Identify Interfering Base Stations

The aggregate I/N at the fixed link receiver was calculated taking into account the 100 small cell base station deployment, and compared against the single interference threshold of I/N = -10 dB. Initially this threshold was exceeded and so base stations were effectively switched off until the threshold was met. It was required to switch off 4 of the 100 so that 96 remained active. The locations of the excluded base stations are highlighted as blue circles in Figure 12-28.

It was noted that there were similar characteristics of the excluded base station locations as for the omni case.

Figure 12-28: Excluded Base Station Locations – Directional Antenna


12.4.4.2 Average Gain and Diffraction Loss

The case in which the small cell base station was on a street directly aligned with the victim receiver was treated as a special case, and so the average gain plus diffraction loss was calculated for the remaining 99 base stations.

It was determined that the average was 46.7 dB, where the averaging was undertaken in absolute rather than dB terms. This was less than the equivalent for the Earth station case due to the lower path loss to the high fixed link receiver antenna.

The aggregation factor from worst single entry to aggregate I/N was calculated to be 5.0 dB.

12.4.5 Average Excluded Zone Areas

The average in absolute [gain + diffraction loss] was used to calculate average excluded areas using the parameters below.

Antenna Omni Andrews

Average [Grel + Diffraction] 41.0 46.7

Single entry to aggregate I/N ratio 9.9 5.0

3 dB factor for multi-path enhancements -3.0 -3.0

Total adjustment to free space

propagation loss 28.1 38.7

Exclusion zone size (km2) 77.5 18.2

Table 12-20: Average Exclusion Zone Parameters

The excluded zone area was the typical keyhole shape for the directional antenna case as can be seen in Figure 12-29.

Note this shows terrain in order to identify locations and scale: it was not used in the analysis which was based on adjusted free space path loss. The contour shows the aggregate threshold, i.e. I/N = -10 dB as the adjustment included a factor to convert between single entry and aggregate I/N. Hence under these assumptions the single entry I/N threshold would be somewhere in the range -15 dB to -19.9 dB.


Figure 12-29: Example Average Excluded Area Zone

These were noted to be significantly larger than for the Earth station average excluded area which were in the range 0.4 – 2.9 km2. Whereas the single-entry to aggregated ratios were similar, there were large differences between the average [Grel + Diffraction] between the two scenarios.

The main reason for the difference was the geometry as shown in Figure 12-29:

The Earth station has higher diffraction, being located close to the clutter line, and greater antenna discrimination due to it using a positive elevation angle.

The fixed link has lower diffraction, being located significantly above the clutter line, and lesser antenna discrimination due to it using a low, possibly negative, elevation angle.


Figure 12-30: Comparison of Earth Station vs. Fixed Link Geometry

12.4.6 Summary

The interference zone around the fixed link receiver on the BT Tower was found to be on average 18.2 – 77.5 km2 in size. This zone was calculated using average gain + diffraction excluding any terrain effects. The zone can be reduced using mitigation methods such as:

Directional antennas at the base station

Reducing the base station height above terrain

Pointing the base station antenna away from the fixed link station

Locating the base station in deep clutter maximising diffraction loss

It could also be useful to analyse the impact of traffic models, fading of the interfering signal and polarisation effects.

However, the average interference zone contained many locations where a base station could be located due to higher diffraction losses. This could facilitate operation very close to the fixed link station: indeed for the deployment of 100 base stations considered, between 94% and 96% were found to be located in positions that had sufficient diffraction to protect the fixed link receiver. In particular, a key factor was the fixed link antenna receive gain, and hence in locations not in its main beam there was high likelihood of ability to deploy small cell base stations.

It is also noted that for the omni antenna case the aggregate I/N = -0.3 while for the directional case it was -2.3 dB. With an adjacent band discrimination or NFD of 23.5 dB, this means that all of the base station locations considered could operate without causing harmful interference when transmitting non-co-frequency.

Earth Station

Base Station

Higher diffraction +

increased relative gain

Lower diffraction

and decreased

relative gain

Earth Station

Elevation > 0

Fixed Link

Elevation < 0

Fixed Link

Receiver


12.5 Power and Traffic

This section describes analysis of using Monte Carlo analysis to convolve the effects of:

Variation in traffic levels, typically over a day

Variation in propagation, typically over a year

Random polarisation loss

12.5.1 Traffic and Power

The parameters below were used in the JTG 4-5-6-7 analysis for small cell base stations.

Maximum power (dBm) 24

Bandwidth (MHz) 10

Average power (dBm) 21

Table 12-21: JTG 4-5-6-7 Small Cell Power Parameters

It is worth re-addressing whether these are valid, in particular to assess the time period over which the power is to be averaged.

The power level is used in interference analysis with propagation models such as P.452 which has an associated percentage of time. The resulting I/N values are then compared against long term thresholds, such as 20% of the time. A key question is: what does “20% of the time” mean?

Propagation models such as P.452 generate statistics that are valid over very long sample times taking samples at regular intervals. All times of day are sampled equally to generate models that are valid over a year, and hence the power average should also be considered over a year. In particular, 20% of the time does not mean 20% of the mobile networks busy hour during the working week.

However JTG 4-5-6-7 Document 715 Annex 2 on LTE parameters specified “typical average activity of a base station and corresponding average output powers during busy hour” as being 50% of maximum load.

It is accepted that small cells have extremely low levels of traffic for significant periods of the day, in particular night-time. There has been research recently8 into the power savings that mobile operators can achieve by completely switching off the small cell base stations for these periods, as the macro cells:

a) Have to be active anyhow to handle vehicular traffic;

b) Have sufficient capacity in quiet times to also handle pedestrians even in locations that are daytime traffic hot spots.

It is worth considering whether the average power is taking into account this period of potentially negligible activity.

8 For example, see the paper “Multiple Daily Base Station Switch-Offs in Cellular Networks” by Marco

Ajmone Marsan, Luca Chiaraviglio, Delia Ciullo and Michela Meo.


Traffic is by nature stochastic and will be sized by expected peaks. This means the cell would only approach maximum power during local busy hour(s). This is compounded by the motivation for opening up the C-band, namely to relieve congestion and reduce the likelihood of users being unable to access mobile broadband services due to an overloaded network. Traffic is also often highly bursty and there will be other constraints (handset performance, user interactions and wider web factors including latency) that would mean that even during busy hour power is likely to reach maximum for only short periods of time.

Furthermore, as noted by Report M.2241, “transmitting 100% time in 100% of frequency resources (in the case of OFDMA) means saturation of the cell and service failure for many of the users”.

A key question is how many much of the day the traffic level is close to that of the busy hour, and conservative assumptions are that this could be either 8 or 4 hours. Two traffic profiles considered in the analysis are shown in Table 12-22 and Figure 12-31. These profiles were assumed to be averages and hence could be applied over all days of the week over the complete year.

Hours per day Traffic Model 1 Traffic Model 2

4 0 dB to -3 dB 0 dB to -6 dB

4 -3 dB to -6 dB -6 dB to -6 dB

4 -6 dB to -10 dB -6 dB to -10 dB

4 -10 dB -10 dB to – 20 dB

8 -20 dB -20 dB

Table 12-22: Proposed Traffic Models

Figure 12-31: Proposed Traffic Models

-25

-20

-15

-10

-5

0

0 4 8 12 16 20 24

Pow

er w

rt p

eak

exce

eded

fo

r gi

ven

ho

urs

Hours of day

Model 1 Model 2


12.5.2 Propagation and Polarization

Study of the C-band scenario in the JTG has been undertaken using P.452 as the propagation model. This is a well-established propagation model for interference analysis but is not suitable for Monte Carlo analysis due to having an upper limit percentage of time of 50%.

For this reason Ofcom has in recent years undertaken significant research into developing the concepts within P.452 further so that the full range of percentages of time can be modelled, namely [0, 100%]. This resulted in propagation model Recommendation ITU-R P.2001 and a recent revision.

The benefit of using this model is it can take account of the cases where the small cell base station would be at maximum power but the signal is faded due to (for example) rain fade.

It should be noted that for the short paths considered for small cell base stations there is not a great variation between short percentages of time and long time. For example Figure 12-32 shows the variation for a 10 km path at 3.8 GHz, and the difference between p=20% and p=0.01% of time is 6.9 dB.

Figure 12-32: Variation in P.452 Propagation Loss for Short Path

When undertaking Monte Carlo analysis it is also worth considering other factors that could vary. An example would be polarization which is different between satellite services (typically circular polarization) and terrestrial (typically linear). Even between two linear polarized services there will be a degree of de-polarization that will lead to the interference detected being reduced compared to a fully co-polar scenario. This could (for example) lead to decrease in interference of between 0 dB and 3 dB.

126

128

130

132

134

136

138

140

0.01 0.1 1 10

P.4

52

pat

h lo

ss f

or

asso

ciat

ed p

erce

nta

ge o

f ti

me

Percentage of time (%)


12.5.3 Monte Carlo Analysis

Monte Carlo analysis was undertaken using the parameters in Table 12-23. Below.

Traffic Models As per Table 12-22

Propagation Model P.2001

Polarization Variation Uniform [0, 3] dB

Maximum Power 14 dBm / MHz

i.e. -16 dBW / MHz

Base station Height 6m

Separation Distance 10 km

Earth Station Height 3m

Earth Station Antenna 2.4 m Rec. S.580

Earth Station Elevation 10°

Earth Station Pointing At base station

Earth Model Smooth + 11.9 Clutter Loss

Table 12-23: Monte Carlo Analysis Parameters

The resulting I/N CDF is shown in Figure 12-33 below:

Figure 12-33: Monte Carlo I/N Analysis

The results are shown in the following table, which also shows the transmit power that would generate the I/N (20%) assuming static analysis using P.452.

0.001

0.01

0.1

1

10

100

-30 -25 -20 -15 -10 -5 0 5 10 15 20

Perc

enta

ge o

f ti

me

I/N

exc

eed

ed

I/N (dB)

Traffic 1 Traffic 2


Traffic Model 1 Model 2

Percentage of time I/N = -10 dB 46.7 % 44.4 %

I/N exceeded for 20% of the time -4.6 dB -6.4 dB

Equivalent power for P.452 (20%) -22.1 dBW/MHz -23.9 dBW/MHz

Reduction compared to peak power -6.1 dB -7.9 dB

Table 12-24: Monte Carlo Run Results

This was less variation that might have been predicted with a large (20 dB) difference between maximum and minimum power. However, with a relatively small variation in the propagation loss, the power levels for percentages of time around 20% become more important. With these traffic models the 20% of time power were just 3.6 dB (Model 1) or 6 dB (Model 2) down from peak.

12.5.4 Summary

Monte Carlo analysis was undertaken that convolved:

Variation in base station transmit power due to possible traffic variation over the whole day

Use of P.2001 propagation model using full percentage of time range [0, 100]

Polarization loss with range [0, 3] dB

This suggests that between 6.1 and 7.9 dB of interference mitigation could in theory be achieved compared to assuming peak power by considering variations in traffic, propagation and polarization effects.

12.6 Conclusions

The core work of this project was the development of maps and statistics relating to availability of spectrum for mobile networks derived using UK wide terrain and land use databases. This section describes work analysing in detail central London using a high-resolution surface database, which suggested that these main maps are likely to be conservative in dense urban areas as the propagation loss is likely to be higher, as described in Section 12.2.3.

There is significant potential to deploy low power low height base stations very close to satellite Earth station and reasonably close to point to point fixed link receivers located in dense urban areas. The key is to ensure there isn’t line of sight between interferer and victim stations, and preferably a significant degree of diffraction loss due to buildings.

This would impose constraints on where the mobile operator could deploy their base station, requiring them to (for example) choose the side of the street with the greatest radio “shadow”. However there would be significant benefits in terms of the number of locations that could be served.

There are likely to be some geometries for which this approach would be unavailable, in particular streets that point directly at receiver stations. Furthermore, it was found to be harder to share with fixed link receivers than satellite Earth station due to their antenna height and pointing direction.


Monte Carlo analysis was also undertaken that suggested that the average power used in studies could be reduced further to take account of time of day variation of traffic.

Mitigation options were considered including increasing dish sizes and for the Earth station case including site shielding. Both could significantly reduce the area excluded but would require the cooperation of the victim licensee.


13 ANNEX: NATIONAL MAPS – FULL SET OF DATA

13.1 Sharing with Satellite Earth Stations and Fixed Links Combined

13.1.1 National Maps






13.1.2 Spectrum Available by Population Tables

The following tables refer to the spectrum available by population in urban, dense urban and hot spot areas only (accounting for 17.41 million people in our model).


13.1.2.1 The 3.6 - 3.8 GHz Spectrum Band

Spectrum

Available (MHz)


Percentage

5 438610 2.52

10 3208276 18.43

15 21721 0.12

20 45150 0.26

25 20091 0.12

35 361002 2.07

40 951509 5.47

45 56161 0.32

50 117888 0.68

65 833259 4.79

70 282223 1.62

80 1362817 7.83

100 683218 3.92

115 9028190 51.86

Table 13-1: Spectrum Available by Population: Sharing with both Satellite Earth

Stations and Fixed Links in 3.6 - 3.8 GHz ( Baseline Case)

Spectrum

Available (MHz)


Percentage

5 109181 0.63

10 2723198 15.64

15 15108 0.09

20 47212 0.27

35 499958 2.87

40 1118174 6.42

45 60216 0.35

50 225208 1.29

65 686384 3.94

70 340232 1.95

80 1321486 7.59

100 754415 4.33

115 9509342 54.62


Stations and Fixed Links in 3.6 - 3.8 GHz (5 dB Relaxation)


Spectrum

Available (MHz)


Percentage

5 26916 0.15

10 1727118 9.92

15 10420 0.06

20 135119 0.78

35 398229 2.29

40 1170538 6.72

45 155520 0.89

50 453896 2.61

65 626577 3.60

70 298702 1.72

80 1319593 7.58

100 830292 4.77

115 10257192 58.92



Spectrum

Available (MHz)


Percentage

10 149173 0.86

20 120087 0.69

35 171092 0.98

40 781458 4.49

45 295177 1.70

50 301245 1.73

65 151483 0.87

70 502109 2.88

80 1571530 9.03

100 836194 4.80

115 12530566 71.97




Spectrum

Available (MHz)


Percentage

0 393154 2.26

5 84198 0.48

10 4767 0.03

15 11357 0.07

20 15896 0.09

35 2120534 12.18

55 1701944 9.78

65 101355 0.58

70 90253 0.52

75 9683 0.06

80 92901 0.53

85 604126 3.47

90 19441 0.11

95 41316 0.24

100 17628 0.10

105 11578 0.07

110 275695 1.58


115 125702 0.72

120 5369 0.03

125 41339 0.24

130 28899 0.17

135 10329 0.06

140 144939 0.83

145 99593 0.57

150 4304 0.02

155 110949 0.64

160 69592 0.40

165 44600 0.26

170 240977 1.38

175 51936 0.30

180 9955 0.06

185 29257 0.17

190 150465 0.86

195 5112 0.03

200 90064 0.52

205 342044 1.96

210 4479 0.03

215 675301 3.88

220 109450 0.63

230 40987 0.24

235 110314 0.63

240 28659 0.16

245 54176 0.31

250 132407 0.76

255 86038 0.49

265 90628 0.52

270 41265 0.24

280 105456 0.61

285 698915 4.01

300 29563 0.17

315 8001223 45.96


Stations and Fixed Links in 3.8 - 4.2 GHz (Baseline Case)

Spectrum

Available (MHz)


Percentage

0 87958 0.51

5 17988 0.10

15 6594 0.04

20 22587 0.13

35 1371127 7.88

55 2098946 12.06

60 6142 0.04

65 29397 0.17

70 89481 0.51

80 196123 1.13

85 479105 2.75

95 71640 0.41

100 30366 0.17

105 9998 0.06

110 298421 1.71

115 314894 1.81


120 23237 0.13

125 40875 0.23

130 24442 0.14

135 25698 0.15

140 171814 0.99

145 100483 0.58

150 5440 0.03

155 110413 0.63

160 25619 0.15

165 74804 0.43

170 243388 1.40

175 78768 0.45

180 43547 0.25

185 75310 0.43

190 155342 0.89

195 12364 0.07

200 118015 0.68

205 184999 1.06

210 11166 0.06

215 614005 3.53

220 161920 0.93

230 49924 0.29

235 42972 0.25

240 18464 0.11

245 71525 0.41

250 175973 1.01

255 70366 0.40

265 78923 0.45

270 94611 0.54

280 243852 1.40

285 599970 3.45

300 84179 0.48

315 8446939 48.52


Stations and Fixed Links in 3.8-4.2 GHz (5 dB Relaxation)

Spectrum

Available

(MHz)


Percentage

0 10314 0.06

5 9104 0.05

20 10420 0.06

35 656864 3.77

55 1830403 10.51

60 16274 0.09

65 7039 0.04

70 200280 1.15

80 143351 0.82

85 517036 2.97

95 122012 0.70

100 40835 0.23

105 11514 0.07

110 92136 0.53

115 201259 1.16

120 32181 0.18


125 106209 0.61

130 40391 0.23

135 41565 0.24

140 112535 0.65

145 111098 0.64

150 30172 0.17

155 97070 0.56

160 132112 0.76

165 167407 0.96

170 112768 0.65

175 85847 0.49

180 47859 0.27

185 115541 0.66

190 225568 1.30

195 92424 0.53

200 263275 1.51

205 102580 0.59

210 24552 0.14

215 458402 2.63

220 125452 0.72

230 63656 0.37

235 175201 1.01

240 21657 0.12

245 148097 0.85

250 287714 1.65

255 147451 0.85

260 5444 0.03

265 122154 0.70

270 62009 0.36

280 393117 2.26

285 424610 2.44

300 33458 0.19

315 9131698 52.45



Spectrum

Available

(MHz)


Percentage

35 67219 0.39

55 352704 2.03

60 10680 0.06

65 8713 0.05

70 271002 1.56

80 50781 0.29

85 283692 1.63

95 99932 0.57

100 43693 0.25

105 6142 0.04

110 296249 1.70

115 210597 1.21

120 69864 0.40

125 20527 0.12

130 31912 0.18

140 79493 0.46


145 129684 0.74

150 33997 0.20

155 150994 0.87

160 36638 0.21

165 113782 0.65

170 102496 0.59

175 50661 0.29

180 53049 0.30

185 239310 1.37

190 123573 0.71

195 70778 0.41

200 99135 0.57

205 75302 0.43

210 34565 0.20

215 407626 2.34

220 268621 1.54

230 99697 0.57

235 131555 0.76

240 14283 0.08

245 133081 0.76

250 308472 1.77

255 98435 0.57

265 262434 1.51

270 20407 0.12

280 780768 4.48

285 381273 2.19

300 52086 0.30

315 11234209 64.53



13.1.2.3 Combined results for the 3.6 - 4.2 GHz Spectrum Band

Spectrum

Available

(MHz)


Percentage

5 349900 2.01

10 81294 0.47

15 42505 0.24

25 10378 0.06

30 8419 0.05

35 22497 0.13

40 1935074 11.11

55 25587 0.15

60 1043985 6.00

65 38549 0.22

70 135716 0.78

80 5345 0.03

85 199762 1.15

90 454010 2.61

100 6135 0.04

105 7203 0.04

110 47007 0.27

115 136612 0.78

120 350865 2.02


125 6785 0.04

135 12536 0.07

140 147715 0.85

145 147343 0.85

150 134887 0.77

155 36722 0.21

165 16800 0.10

170 110471 0.63

175 117503 0.67

180 92124 0.53

185 5369 0.03

190 9683 0.06

195 84694 0.49

200 80653 0.46

205 95758 0.55

210 44919 0.26

220 10693 0.06

225 128724 0.74

230 111718 0.64

235 71199 0.41

240 65214 0.37

255 67328 0.39

260 161466 0.93

265 137223 0.79

270 102739 0.59

275 9897 0.06

285 125091 0.72

290 725685 4.17

295 68540 0.39

300 98416 0.57

305 26703 0.15

310 5112 0.03

315 9018 0.05

320 4821 0.03

325 159042 0.91

330 125204 0.72

335 13464 0.08

355 4926 0.03

360 452718 2.60

365 102948 0.59

380 4366 0.03

390 4405 0.03

395 683285 3.92

430 7885362 45.29


Stations and Fixed Links in 3.6 - 4.2 GHz (Baseline Case)

Spectrum

Available

(MHz)


Percentage

5 87958 0.51

15 17988 0.10

25 14073 0.08

35 28852 0.17

40 1170279 6.72


60 1370089 7.87

65 79920 0.46

70 107958 0.62

85 219805 1.26

90 539272 3.10

95 10413 0.06

110 121085 0.70

115 107815 0.62

120 277765 1.60

135 8067 0.05

140 149686 0.86

145 192516 1.11

150 164860 0.95

155 21116 0.12

160 13241 0.08

170 105424 0.61

175 159030 0.91

180 182324 1.05

185 9996 0.06

190 5239 0.03

195 56453 0.32

200 150315 0.86

205 95197 0.55

210 60326 0.35

215 5265 0.03

220 35918 0.21

225 156826 0.90

230 178315 1.02

235 30353 0.17

240 54563 0.31

255 76789 0.44

260 74920 0.43

265 124188 0.71

270 91579 0.53

275 4453 0.03

285 68521 0.39

290 669981 3.85

295 38185 0.22

300 121070 0.70

305 25055 0.14

310 5444 0.03

315 14176 0.08

325 317329 1.82

330 158203 0.91

335 19398 0.11

360 434307 2.49

365 78592 0.45

395 783336 4.50

430 8316284 47.77




Spectrum

Available

(MHz)


Percentage

5 10314 0.06

10 9104 0.05

35 10420 0.06

40 496264 2.85

60 943493 5.42

65 60413 0.35

70 94112 0.54

85 321360 1.85

90 769474 4.42

95 13636 0.08

100 25066 0.14

105 6620 0.04

110 160385 0.92

115 122518 0.70

120 270524 1.55

125 15954 0.09

135 42607 0.24

140 78799 0.45

145 86567 0.50

150 121080 0.70

155 7039 0.04

165 13287 0.08

170 93073 0.53

175 89087 0.51

180 111701 0.64

190 13717 0.08

195 32176 0.18

200 97452 0.56

205 180823 1.04

210 70774 0.41

220 30367 0.17

225 60065 0.34

230 169871 0.98

235 92124 0.53

240 69205 0.40

255 313887 1.80

260 166480 0.96

265 125242 0.72

270 83182 0.48

285 12894 0.07

290 669594 3.85

295 70580 0.41

300 176127 1.01

305 44891 0.26

315 9683 0.06

325 347927 2.00

330 180269 1.04

335 20076 0.12

340 5444 0.03

355 18680 0.11

360 705480 4.05

365 71285 0.41


395 590355 3.39

430 9008568 51.74



Spectrum

Available

(MHz)


Percentage

40 46028 0.26

60 82516 0.47

65 7418 0.04

70 4402 0.03

85 169862 0.98

90 163537 0.94

95 9372 0.05

110 188619 1.08

115 33372 0.19

120 251859 1.45

125 10680 0.06

135 60306 0.35

140 17261 0.10

145 261759 1.50

150 133048 0.76

155 8713 0.05

160 34801 0.20

165 4569 0.03

170 56862 0.33

175 193260 1.11

180 127011 0.73

195 68379 0.39

200 73056 0.42

205 47787 0.27

210 52708 0.30

215 10532 0.06

220 24582 0.14

225 16595 0.10

230 152343 0.88

235 111168 0.64

240 34182 0.20

255 132312 0.76

260 225419 1.29

265 80834 0.46

270 59979 0.34

290 434158 2.49

295 223087 1.28

300 93254 0.54

305 15147 0.09

325 438480 2.52

330 158006 0.91

335 22239 0.13

355 7595 0.04

360 1088934 6.25

365 119234 0.68

395 748643 4.30

430 11106205 63.79




13.1.3 Spectrum Available by Population CDFs

13.1.3.1 The 3.6 – 3.8 GHz Spectrum Band

Figure 13-4 below shows the available spectrum by population for the baseline case and auxiliary variations for the 3.6 – 3.8 GHz band.

Examination of the underlying data shows, for baseline assumptions, of the 17,410,114 people in the highest density geotype pixels, 9,028,190 have access to the entire spectrum available in this part of the band (115 MHz). This represents 51.86% of the population.

If the interference level is reduced by 5, 10 and 20 dB the number increases and is 71.97% when 20 dB extra advantage is introduced.

Figure 13-4: Spectrum Available per Population Count in 3.6 - 3.8 GHz: Sharing







Figure 13-5: Spectrum Available per Population Count in 3.8 - 4.2 GHz: Sharing







Figure 13-6: Spectrum Available per Population Count in 3.6 - 4.2 GHz: Sharing with

Satellite Earth Stations and Fixed Links


13.2 Sharing with Satellite Earth Stations only


Figure 13-7: Colour Coded Map of Spectrum Available in Sharing with Satellite Earth

Stations in 3.6 - 3.8 GHz



Spectrum

Available (MHz)


Percentage

5 13190 0.08

10 22765 0.13

15 418081 2.40

25 11197 0.06

55 37988 0.22

70 55312 0.32

80 15440 0.09

100 15042 0.09

115 16821099 96.62

Table 13-13: Spectrum Available by Population: Sharing with Satellite Earth Stations in

3.6 - 3.8 GHz (Baseline Case)

Spectrum

Available (MHz)


Percentage

15 139785 0.80

70 19932 0.11

80 15440 0.09

90 6142 0.04

100 5239 0.03

115 17223575 98.93

Table 13-14: Spectrum Available by Population: Sharing with Satellite Earth Stations

3.6 - 3.8 GHz (5 dB Relaxation)

Spectrum

Available (MHz)


Percentage

15 28232 0.16

55 9104 0.05

80 10071 0.06

100 6620 0.04

115 17356086 99.69



Spectrum

Available (MHz)


Percentage

115 17410114 100.00





Spectrum

Available (MHz)


Percentage

0 46197 0.27

5 324373 1.86

20 11300 0.06

40 5706 0.03

65 5345 0.03

70 50333 0.29

75 9683 0.06

80 4767 0.03

85 21151 0.12

125 5368 0.03

145 9996 0.06

160 4445 0.03

180 11192 0.06

190 9266 0.05

195 19718 0.11

200 19395 0.11

210 5129 0.03

250 30397 0.17

260 5444 0.03

265 7166 0.04

275 4926 0.03

280 23661 0.14

295 2231358 12.82

305 134317 0.77

315 14409479 82.76


3.8 – 4.2 GHz (Baseline Case)

Spectrum

Available (MHz)


Percentage

5 78169 0.45

20 15108 0.09

85 22314 0.13

145 9996 0.06

150 5217 0.03

190 4649 0.03

195 6594 0.04

200 19441 0.11

210 8122 0.05

225 6142 0.04

230 13744 0.08

250 19783 0.11

265 5444 0.03

280 34296 0.20

295 1392916 8.00

305 68521 0.39

315 15699660 90.18


3.8 – 4.2 GHz (5 dB Relaxation)


Spectrum

Available (MHz)


Percentage

20 10420 0.06

85 10314 0.06

155 4627 0.03

195 9104 0.05

200 9683 0.06

210 5369 0.03

250 7498 0.04

280 48277 0.28

295 740331 4.25

305 31574 0.18

315 16532916 94.96



Spectrum

Available (MHz)


Percentage

280 6978 0.04

295 97145 0.56

305 7595 0.04

315 17298397 99.36




13.2.2.3 Combined Results for the 3.6 – 4.2 GHz Spectrum Band

Spectrum

Available (MHz)


Percentage

5 8746 0.05

10 17420 0.10

15 20031 0.12

20 5550 0.03

25 318823 1.83

35 11300 0.06

60 5706 0.03

80 5345 0.03

95 4767 0.03

105 21151 0.12

135 28003 0.16

145 5368 0.03

150 22331 0.13

165 4445 0.03

190 9683 0.06

200 11192 0.06

210 9266 0.05

230 9996 0.06

260 5575 0.03

265 4926 0.03

275 14143 0.08

315 19395 0.11

320 11197 0.06

325 5129 0.03

340 12610 0.07

365 25470 0.15

370 4410 0.03

385 11672 0.07

390 4926 0.03

395 23661 0.14

410 2220161 12.75

415 15042 0.09

425 134317 0.77

430 14378356 82.59


3.6 – 4.2 GHz (Baseline Case)


Spectrum

Available (MHz)


Percentage

25 78169 0.45

35 15108 0.09

105 22314 0.13

210 4649 0.03

230 15213 0.09

245 13744 0.08

265 5802 0.03

275 6594 0.04

290 8122 0.05

310 6142 0.04

315 19441 0.11

345 5444 0.03

365 13981 0.08

395 34296 0.20

410 1392916 8.00

415 5239 0.03

425 68521 0.39

430 15694421 90.15



Spectrum

Available (MHz)


Percentage

35 10420 0.06

105 10314 0.06

240 4627 0.03

260 9104 0.05

265 7498 0.04

315 9683 0.06

325 5369 0.03

375 5444 0.03

395 48277 0.28

410 734887 4.22

415 6620 0.04

425 31574 0.18

430 16526296 94.92



Spectrum

Available (MHz)


Percentage

395 6978 0.04

410 97145 0.56

425 7595 0.04

430 17298397 99.36

Table 13-24 – Spectrum Available by Population: Sharing with Satellite Earth station in





Figure 13-10 below shows the available spectrum by population for the baseline case and auxiliary variations for the 3.6 – 3.8 GHz band (noting that the auxiliary case where the relaxation is 20 dB does not produce any interference).


If the interference level is reduced by 5, 10 and 20 dB the number increases and is 100% before 20 dB extra advantage is introduced.


Satellite Earth Stations


Figure 13-11 below shows the available spectrum by population for the baseline case and auxiliary variations for the 3.8 – 4.2 GHz band (noting that the auxiliary case where the relaxation is 20 dB produces a small amount of interference).



If the interference level is reduced by 5, 10 and 20 dB the number increases and is 99.36% when 20 dB of extra advantage is introduced.




Figure 13-12 below shows the available spectrum by population for the baseline case and auxiliary variations for the 3.6 – 4.2 GHz band (noting that the auxiliary case where the relaxation is 20 dB produces a small amount of interference).


If the interference level is reduced by 5, 10 and 20 dB the number increases and is 99.36% when 20 dB of extra advantage is introduced.


13.3 Sharing with Fixed Links Only


Figure 13-13: Colour Coded Map of Spectrum Available in Sharing with Fixed Links in

3.6 - 3.8 GHz



3.8 - 4.2 GHz



Spectrum

Available (MHz)


Percentage

10 3550269 20.39

20 45150 0.26

35 395294 2.27

40 957310 5.50

45 87693 0.50

50 123463 0.71

65 822468 4.72

70 282223 1.62

80 1367862 7.86

100 705570 4.05

115 9072812 52.11

Table 13-25: Spectrum Available by Population: Sharing with Fixed Links in 3.6 - 3.8

GHz (Baseline Case)

Spectrum

Available (MHz)


Percentage

10 2780144 15.97

20 47212 0.27

35 516851 2.97

40 1118737 6.43

45 80432 0.46

50 225208 1.29

65 681256 3.91

70 340232 1.95

80 1325736 7.61

100 764411 4.39

115 9529893 54.74


GHz (5 dB Relaxation)

Spectrum

Available (MHz)


Percentage

10 1736222 9.97

20 135119 0.78

35 398229 2.29

40 1163918 6.69

45 179952 1.03

50 453896 2.61

65 626577 3.60

70 298702 1.72

80 1309522 7.52

100 830292 4.77

115 10277683 59.03

Table 13-27 – Spectrum Available by Population: Sharing with Fixed Links in 3.6 - 3.8



Spectrum

Available (MHz)


Percentage

10 149173 0.86

20 120087 0.69

35 171092 0.98

40 781458 4.49

45 295177 1.70

50 301245 1.73

65 151483 0.87

70 502109 2.88

80 1571530 9.03

100 836194 4.80

115 12530566 71.97





Spectrum

Available (MHz)


Percentage

55 4206185 24.16

70 90253 0.52

80 112829 0.65

85 717380 4.12

95 48795 0.28

100 17938 0.10

105 11578 0.07

110 295105 1.70

115 125702 0.72

125 41339 0.24

130 47566 0.27

135 10329 0.06

140 144939 0.83

145 99593 0.57

150 4304 0.02

155 110949 0.64

160 70533 0.41

165 44600 0.26

170 240977 1.38

175 63214 0.36

180 4826 0.03

185 34522 0.20

190 150465 0.86

200 81046 0.47

205 216953 1.25

210 4479 0.03

215 794948 4.57

220 95986 0.55

230 40987 0.24

235 114941 0.66

240 18911 0.11

245 30515 0.18

250 130333 0.75

255 91083 0.52

265 101441 0.58

270 36860 0.21

280 157042 0.90

285 698915 4.01

300 29563 0.17

315 8072187 46.36


GHz (Baseline Case)


Spectrum

Available (MHz)


Percentage

55 3551558 20.40

70 94130 0.54

80 202265 1.16

85 514919 2.96

95 65504 0.38

100 30366 0.17

105 9998 0.06

110 298421 1.71

115 328474 1.89

120 13241 0.08

125 40875 0.23

130 31940 0.18

135 25698 0.15

140 166549 0.96

145 100483 0.58

150 5440 0.03

155 117892 0.68

160 25619 0.15

165 74804 0.43

170 243388 1.40

175 78768 0.45

180 43547 0.25

185 75310 0.43

190 155342 0.89

195 12364 0.07

200 103839 0.60

205 116478 0.67

210 11166 0.06

215 682526 3.92

220 153069 0.88

230 44480 0.26

235 42972 0.25

240 18464 0.11

245 53848 0.31

250 170844 0.98

255 80677 0.46

265 88920 0.51

270 94611 0.54

280 259205 1.49

285 599970 3.45

300 84179 0.48

315 8497971 48.81




Spectrum

Available (MHz)


Percentage

55 2496371 14.34

70 205527 1.18

80 159624 0.92

85 524075 3.01

95 89705 0.52

100 45902 0.26

105 11514 0.07

110 92136 0.53

115 233565 1.34

120 23494 0.13

125 92492 0.53

130 40391 0.23

135 41565 0.24

140 113724 0.65

145 120187 0.69

150 30172 0.17

155 104568 0.60

160 132112 0.76

165 167407 0.96

170 112768 0.65

175 85847 0.49

180 47859 0.27

185 115541 0.66

190 225568 1.30

195 92424 0.53

200 253592 1.46

205 89686 0.52

210 19183 0.11

215 471295 2.71

220 125452 0.72

230 63656 0.37

235 175201 1.01

240 21657 0.12

245 126896 0.73

250 287714 1.65

255 147451 0.85

265 122154 0.70

270 43329 0.25

280 415993 2.39

285 424610 2.44

300 33458 0.19

315 9184247 52.75




Spectrum

Available (MHz)


Percentage

55 419923 2.41

70 271002 1.56

80 61462 0.35

85 292406 1.68

95 99932 0.57

100 43693 0.25

105 6142 0.04

110 296249 1.70

115 210597 1.21

120 69864 0.40

125 20527 0.12

130 31912 0.18

140 79493 0.46

145 129684 0.74

150 23465 0.13

155 150994 0.87

160 36638 0.21

165 113782 0.65

170 113028 0.65

175 50661 0.29

180 53049 0.30

185 239310 1.37

190 123573 0.71

195 70778 0.41

200 99135 0.57

205 75302 0.43

210 34565 0.20

215 407626 2.34

220 268621 1.54

230 99697 0.57

235 131555 0.76

240 14283 0.08

245 133081 0.76

250 308472 1.77

255 98435 0.57

265 262434 1.51

270 12812 0.07

280 781385 4.49

285 381273 2.19

300 52086 0.30

315 11241187 64.57




13.3.2.3 Combined Results for the 3.6 – 4.2 GHz Spectrum Band

Spectrum

Available (MHz)


Percentage

60 3364791 19.33

85 276969 1.59

90 592583 3.40

110 62327 0.36

115 145305 0.83

120 314541 1.81

135 23574 0.14

140 194772 1.12

145 164172 0.94

150 134887 0.77

165 12355 0.07

170 129138 0.74

175 144333 0.83

180 92124 0.53

195 84694 0.49

200 86039 0.49

205 95758 0.55

210 44919 0.26

220 10693 0.06

225 128724 0.74

230 111718 0.64

235 71199 0.41

240 65214 0.37

255 67328 0.39

260 166732 0.96

265 137223 0.79

270 114018 0.65

275 4453 0.03

290 850776 4.89

295 63410 0.36

300 98416 0.57

305 26703 0.15

325 163863 0.94

330 134877 0.77

360 439869 2.53

365 96053 0.55

395 739237 4.25

430 7956326 45.70


GHz (Baseline Case)


Spectrum

Available (MHz)


Percentage

60 2612903 15.01

85 316619 1.82

90 659625 3.79

110 121085 0.70

115 113183 0.65

120 276928 1.59

135 8067 0.05

140 157967 0.91

145 202034 1.16

150 158724 0.91

160 13241 0.08

170 119058 0.68

175 180147 1.03

180 182324 1.05

195 69171 0.40

200 150315 0.86

205 95197 0.55

210 60326 0.35

220 35918 0.21

225 156826 0.90

230 178315 1.02

235 30353 0.17

240 54563 0.31

255 76789 0.44

260 74920 0.43

265 124188 0.71

270 91579 0.53

275 4453 0.03

290 738502 4.24

295 38185 0.22

300 121070 0.70

305 25055 0.14

325 317329 1.82

330 168514 0.97

335 10547 0.06

360 426626 2.45

365 73463 0.42

395 798689 4.59

430 8367317 48.06




Spectrum

Available (MHz)


Percentage

60 1448862 8.32

85 381772 2.19

90 863586 4.96

110 172252 0.99

115 136154 0.78

120 295590 1.70

135 42607 0.24

140 76368 0.44

145 102521 0.59

150 121080 0.70

165 13287 0.08

170 93073 0.53

175 96127 0.55

180 111701 0.64

195 39674 0.23

200 97452 0.56

205 180823 1.04

210 75804 0.44

220 30367 0.17

225 60065 0.34

230 173930 1.00

235 92124 0.53

240 69205 0.40

255 313887 1.80

260 166480 0.96

265 125242 0.72

270 83182 0.48

290 682488 3.92

295 70580 0.41

300 176127 1.01

305 44891 0.26

325 342558 1.97

330 180269 1.04

335 20076 0.12

360 702959 4.04

365 71285 0.41

395 594551 3.41

430 9061116 52.05




Spectrum

Available (MHz)


Percentage

60 128544 0.74

85 177280 1.02

90 167939 0.96

110 188619 1.08

115 42743 0.25

120 251859 1.45

135 60306 0.35

140 17261 0.10

145 272440 1.56

150 133048 0.76

160 34801 0.20

165 4569 0.03

170 56862 0.33

175 201973 1.16

180 127011 0.73

195 68379 0.39

200 73056 0.42

205 47787 0.27

210 52708 0.30

220 24582 0.14

225 16595 0.10

230 152343 0.88

235 121699 0.70

240 34182 0.20

255 132312 0.76

260 225419 1.29

265 80834 0.46

270 59979 0.34

290 434158 2.49

295 223087 1.28

300 93254 0.54

305 15147 0.09

325 438480 2.52

330 158006 0.91

335 22239 0.13

360 1096529 6.30

365 119234 0.68

395 741665 4.26

430 11113182 63.83










Fixed Links











Fixed Links

#


14 ANNEX: ACRONYMS AND ABBREVIATIONS ACI Adjacent Channel Interference

ACLR Adjacent Channel Leakage Ratio

APL Antenna Pattern Library

BER Bit Error Rate

CEPT European Conference of Postal and Telecommunications Administrations

ECC Electronic Communications Committee

EIRP Equivalent Isotropic Radiative Power

ETSI European Telecommunications Standards Institute

IMT International Mobile Telecommunications

ITU International Telecommunications Union

JTG Joint Task Group

LTE Long Term Evolution

MIMO Multiple Input Multiple Output

NFD Net Filter Discrimination

OOB Out Of Band

PES Permanent Earth Station

PT Project Team

RSA Recognised Spectrum Access

RX Receive

SC Small Cell

TX Transmit

Urban+ Those areas that are classified as urban, dense urban or hotspot areas

VSAT Very Small Aperture Terminal

WP Working Party

WRC World Radiocommunications Conference


15 INPUT DATA The data relating to the fixed links and permanent earth stations were provided by Ofcom. The data are in the attached files.

The file Link_List.xls contains the fixed links data. The file UK PES_sites.xls contain the permanent earth station files.

UK PES_sites.xls

Link_List.xls

geographic sharing in c-band

Technology

geographic sharing

cband page

cband reference

editorial changes

executive summary

high resolution analysis

c rathbone square fax

set of data