huawei 2g coverage planning.pdf

Coverage Planning

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www.huawei.com

Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.

Coverage Planning Principle

Coverage Planning


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Page2Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.

Contents

1. Planning Basis

2. Coverage Planning

3. Advance Planning

4. Advance Technology for improving coverage

Coverage Planning


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Radio Propagation Environment

� Multi-path propagation� Shadowing� Terrain � Building� Reflection� Interference

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Reflections

direct signalstrong reflected signal

equalizer window 16 µs

amplitude

delay time

long echoes, out of equalizer window:self-interference

� Strong echoes can cause excessive transmission delay� No impact If the delay falls in the equalizer window � Cause self-interference if the delay falls out of the equalizer

window

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FadingTransmission

Receiving

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Fading

� Slow fading (Lognormal Fading)

� Shadowing due to large obstacles on propagation direction

� Fast fading (Rayleigh fading)

� Serious interference from multi-path signals

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Fading

time

power

2 sec 4 sec 6 sec

+20 dB

mean value

- 20 dB

lognormal fading

Rayleighfading

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Land Types during Planning

� Urban small cells

� Forest heavy absorption; differs with seasons

� Open, farmland easy, smooth propagation conditions

� Water propagates very easily ==> dangerous !

� Mountain surface strong reflection, long echoes

� Hilltops can be used as barriers between cells,

do not use as antenna or site location

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Contents

1. Planning Basis


3. Advance Planning


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Cell Coverage RangeThe purpose of coverage planning is using the less BTS to perform

more coverage. Achievable cell coverage depend on:

1. Get the coverage requirement and parameters: such as Minimum

required signal level, Operator requirement of coverage

probability

2. The max allowed path loss according link budget

3. The cell coverage radius depend on max allowed path loss and

propagation model

4. Calculate the BTS coverage and the BTS number

� Difference band coverage area will be difference. Normally some others situation also will influence

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Link Budgetreceivemsbtscablecombinerbts MinGLGLLP ≥+−+−−

receivecablebtsdiversitymsms MinLGGLGP ≥−++−+

� GSM has two frequency bands: 900 MHz and 1800 MHz. Each band hasdifferent transmission characteristics. Long wavelength comes with little diffraction loss and short wavelength comes with little building penetration loss. Indoor wave component is the superimposition of penetration component and diffraction component. Diffraction component constitutes most of the wave component, and therefore, the indoor and outdoor level difference of 1800 MHz is greater than that of 900 MHz. Because of the issues such as complex transmission environment and the direction of incident waves, quantify indoor and outdoor level difference is not very practical. The best way is to carry out level difference test in special environment for planning optimization.

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Min. Receiving Level

�On Down Link

�On Uplink

npenetratioinm

inminminmmsreceive

LFastFading

ngshadowfadingSlowlyFadiISMin

++

++=

arg

argargarg )(

npenetratio

inminminminmbtsreceive

L

FastFadingngShadowFadingSlowlyFadiISMin

+

+++= argargargarg )(

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Equipment-related Parameters

� BTS receiver sensitivity

� -112.5dBm

� The sensitivity is also related with vendor and environment

� MS receiver sensitivity

� -102dBm

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Interference Margin

� Interference margin: sometimes also named noise

correction, which is protection margin for interference.

� Normally interference margin is 2dB.

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Link Budget

� Fast fading margin

� In the link balance calculation, fast fading margin should be

considered

011111Fast fading margin

(dB)

Sea Road Rural

area

townUrban Density urban

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Coverage Probability

area coverage probability: Within a coverage area, the percentage

of area in which receive signal strength (RxLev) is always higher than RxLev threshold

edge coverage probability: In coverage board area, the percentage time when the receive signal strength (RxLev) is always larger than

the of RxLev threshold

� Sometimes during the planning, coverage probability also have to consider. And for high coverage probability, high shadow fading margin reserved. Normally, there are two types coverage probabilities: area coverage probability and edge coverage probability.

� According to the standard deviation of the shadow fading and the requirements for the border coverage probability (determined by the operator), we can calculate the edge coverage probability by formula.

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Area coverage probability to edge coverage probability

edge coverage probability

100%90%86%79%72%66%64%51%50%32%14%6%High way

100%93%90%85%80%76%73%63%54%46%27%17%village

100%94%91%86%81%77%75%66%57%49%30%20%Rural area

100%94%91%86%81%77%75%66%57%49%30%20%urban

100%94%91%86%81%77%75%66%57%49%30%20%Dense urban

100%98%97%95%93%91%90%85%80%75%60%50%area coverage probability

� Check this table, we can know the relationship of area coverage probability and edge coverage probability.

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Margin

� To ensure a certain edge coverage probability , it is

necessary to reserve some power margin, i.e. the shadow

fading margin, also call it slowly fading.

� Due to the shadow fading, the actual path loss fluctuates

around this value. It is subjected to the logarithmic normal

distribution as the location and time varies.

� Note : the 75% edge coverage probability is corresponding to the 90% area coverage probability.

� Concept of communication probability: Success call rate of MS on the radio coverage border or in the cell

� Category of communication probability: location probability and time probability

� In general, the time change has little impact on the communication probability, so it can be neglected.

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Area coverage probability to expected shadow fading margin

50% 60% 75% 80% 90% 92% 93% 95% 97% 98% 99% 100%�� -6.7 -4.2 -0.1 1.4 5.5 6.5 7.2 8.6 10.7 12.2 14.6 21.3�� -6.7 -4.2 -0.1 1.4 5.5 6.5 7.2 8.6 10.7 12.2 14.6 21.3�� -6.7 -4.2 -0.1 1.4 5.5 6.5 7.2 8.6 10.7 12.2 14.6 21.3�� -6.6 -4.3 -0.6 0.8 4.3 5.4 5.9 7.2 9.1 10.4 12.3 19.2�� -6.1 -4.4 -1.8 0 1.4 2 2.4 3.2 4.3 5.1 6.5 10.4

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Penetration LossSignal loss for penetration varies between different building materials, e.g.:

2 dBwindow glass

6 dBwood or plaster wall

8 dBarmed glass

9 dBbrick wall

10 dBconcrete wall within building

30 dBconcrete wall, no windows

17 dBreinforced concrete wall, windows

MeanMaterials

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Min. Receive Level

Sms=-102dBmFast Fading Margin=1dBSlowly Fading Margin=5dBInterference margin=2dB

? dBmOutdoor

Sms=-102dBmFast Fading Margin=1dBSlowly Fading Margin=5dBInterference margin=2dBPenetration Loss=10

? dBmResident area, indoor


? dBmDensity urban, indoor

GivenMin. Receiving LevelApplication Environment

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Min. Receive Level

Sms=-102dBmFast Fading Margin=3dBSlowly Fading Margin=5dBInterference margin=4dB

-90dBmOutdoor


-80dBmResident area, indoor


-70dBmDensity urban, indoor

GivenMin. Receiving LevelApplication Environment

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Link Budget Model

receivemsbtscablecombinerbts MinGLGLLP ≥+−+−−

receivecablebtsdiversitymsms MinLGGLGP ≥−++−+

On downlink

On uplink

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Equipment-related Parameters� BTS Tx power

� Maximum BS Tx power.

� Maximum power of the antenna Ptrx-Lcdu

� Maximum MS Tx power

� 900:2W

� 1800:1W

� BS antenna gain

� Typical value: Omni directional antenna: 11dBi or 13dBi; directional antenna: 15 to 18dBi.

� MS antenna gain

� Generally, MS antenna and the connection loss are considered to be 0dB.

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No Combining

TCOM

TRX0TRX0

TX

TRX1TRX1

TX

TX1

IN1

IN2

TX2

RXM1

RXD1

RXM2

RXD2

combinercombiner

� For the cell which just has one or two TRX, the TRX will not be connected to the combiner and directly connected to DDPU (Dual Duplexer Unit for DTRU BTS). So it is combiner loss will be 0---1 dB.

� The DDPU is for sending multi RF signals from the transceiver in the DTRU to the antenna through the duplexer

� Sending signals from the antenna after amplifying and quartering them to the transceiver in the DTRU

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Wide Band Combining

TRX0TRX0

TX

TRX1TRX1

TX

TX1

IN1

TCOM

IN2

TX2

combinercombiner

� If for the cell which has more than two TRX, TRX0 and TRX1 will be connected to the combiner first and then connected to DDPU. It’s combiner

� loss will be 3.3+1=4.3dB� The DDPU is intermixed with the DCOM (Combining Unit for DTRU BTS in the

DAFU subrack of the forepart of RF subsystem. It is indispensable. Generally, the number of DDPU is one at least and three at most. Without the DCOM, there can be at most six DDPUs

� Sending multi RF signals from the transceiver in the DTRU to the antenna through the duplexer

� Sending signals from the antenna after amplifying and quartering them to the transceiver in the DTRU

� The DCOM is optional and there are a maximum three DCOMs. The DTRU combines two carriers into one channel. The DCOM is required when the DTRUs are insufficent

� The DCOM combines the 2-route DTRU transmission signals and outputs them to the DDPU

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Feeder and Jumper

feeder connector

Feeder

Antenna Adjustable Support

GSM/CDMAPanel Antenna

BTS

Wall

jumper

� In a wireless telecommunication system, the antenna provides the interface between base transceiver station (BTS) and outside propagation mediums. One set of antenna can both radiate and receive radio waves. When radiating radio waves, it converts high frequency current into electromagnetic wave; when receiving radio waves, it converts the electromagnetic wave into high frequency current.

� During network planning, the right antenna is selected according to the radio environment of the BTS. The parameters, such as antenna height, antenna azimuth angle, tilt angle, are decided based on the selected antenna.

� Antenna is directly related to uplink and downlink converges, so are the radio frequency (RF) components, such as feeder cable, combiner, and duplexer.

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Antenna Feeder System—Feeder�Feeder:

Frequently-used specification:

7/8 ", 5/4 "

The curvature of the feeders shall not be

too large, and the conductor surface is

required to well connected with the ground

<=80meters

>80 meters

900MHZ

<=50meters7/8 "

>50 meters5/4 “

1800MHZ

5dB/100m

3dB/100m

900MHZ

6dB/100m7/8 "

4dB/100m5/4 “

1800MHZ

How to choose a feeder Feeder loss

11dB/100m1/2 jumper length (m)

� Loss of frequently-used feeders

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Example

30MS max. transmitting power(dBm)

-102MS sensitivity (dBm)

?Effective Radiated Power EIRP(dBm)

17BTS antenna gain (dBi)

?BTS combiner, jumper, feeder and connector

loss (dB)

0.5feeder connector loss (dB)

11dB/100m51/2 jumper length (m)

4dB/100m457/8 feeder length (m)

1BTS combiner loss (dB)

46BTS max. transmitting power (dBm)

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Example

?dBexpected shadow fading margin (dB)

2Noise correction (dB) (interference margin)

5dBclutter loss (dB) (slow fading margin)

3dBFast fading margin

1dBMS antenna gain

?allowed DL Max Propagation loss in Um interface(dB)

4Body loss (penetration loss)

91%corresponding edge coverage probability

97%expected area coverage probability

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Coverage Radius

� According the max allowed path loss, BTS antenna height

and propagation model, can calculate the cell coverage

radius.

� Depend on cell coverage radius, can get the cell coverage

area and BTS number.

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Objective of Propagation Model

� The propagation model is used to estimate the path loss

during radio wave propagation caused by the terrain and

artificial environments

� The propagation model is the foundation of the coverage

planning. A good model mean more precise planning.

� The propagation model depends on the working frequency

of the system. Different propagation models have different

working frequencies ranges.

�Through surveying radio propagation environments, you can get familiar with the overall landforms, estimate the rough antenna height, and select the proper radio propagation model, among which the radio propagation model helps you estimate the number of base station when predicting the coverage. If necessary, you must adjust the propagation model.�Moreover, indoor propagation model differs from the out door propagation model

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Propagation Mode

900 MHz and1800MHz macro cellK – Mode (U-net)

900 MHz and 1800 MHz indoorKeenan-Motley

900 MHz and 1800 MHz micro CellCost231 Walfish-Ikegami

1500-2000 MHz macro cellCost231-Hata

150-1000 MHz macro cellOkumura-Hata

ApplicationName

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Okumura-Hata Model� Frequency: f:1505~2000MHz� BTS antenna height: Hb:30~200m� Mobile station height: Hm:1~10m� Distance: d:1~20km

mhbbp AdhhfL −−+−+= log)log55.69.44(log82.13log16.2655.69

Lp fd

mhA: Path loss (dB)

: MS correction factor (dB)

: Carrier frequency (MHz)

: Distance of BS and MS (Km)

)8.0log56.1()7.0log1.1( −−−= fhfA mhm

97.4)75.11(log2.3 2 −= mh hAm

Middle or small cities:

Big cities:

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Cost231-Hata� Frequency range f:1505~2000MHz� BTS antenna height Hb:30~200m� Mobile station height Hm:1~10m� Distance d:1~20km

mhbbp CAdhhfLm

+−−+−+= log)log55.69.44(log82.13log9.333.46

mCmC 0dB Large-size cities

3dB Big cities

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Site Coverage Radius: RSite distance: D=1.5RCoverage Area=1.949R2

Site Coverage Radius: RSite distance: D=1.732RCoverage Area=2.598R2

3 – Sectors site Omni site

Distance and Coverage Area

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Example

Omni

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Link Balance Tool

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Contents

1. Planning Basis


3. Advance Planning


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Why Indoors� Indoor coverage become the main competition between operators

� Subscribers expect continuous coverage and better quality

� Outdoor cell can’t provide sufficient indoor coverage

INDOOR SOLUTION

Good Quality!

� With the rapid development of economy, hotels, commercial centers, large-scale flats, underground railways, and underground parking areasare arising by batch. As a result, mobile stations are more frequently used in indoor environment. Thus, they require better indoor mobile communication services.

� Generally, the following problems are present in indoor mobile communication systems:

� From the perspective of coverage, the complex indoor structure and the shielding and absorbing effect of the buildings cause great radio wave transmission loss. As a result, the signals in some areas may be weak, especially the signals in the first and second floors in the underground are quite weak, or even there are dead zones. In this case, mobile stations cannot necessarily access the network, there is no paging response, or subscribers are not in service areas.

� From the perspective of network quality, the factors interfering radio frequencies are probably present in upper floors of high buildings. In this case, the signals in service areas are not stable, so “ping pong effect”may occur and conversation quality cannot be ensured.

� From the perspective of network capacity, if mobile stations are frequently used in buildings, such as large-scale shopping centers, conference halls, some areas in the network cannot meet the requirements of subscribers. In this case, congestion may occur on radio channels.

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Building Penetration Loss

rear side :-18 ...-30 dB

Pref = 0 dB

Pindoor = -3 ...-15 dB

Pindoor = -7 ...-18 dB

-15 ...-25 dB no coverage

signal level increases with floor number :~1.5 dB/floor (for 1st ..10th floor)

� Signal level in building is estimated by using a building penetration loss margin

� Big differences between rooms with window and without window(10~15 dB)

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Building Penetration Loss

� Signal loss for penetration varies between different building materials, e.g.:

mean value

reinforced concrete wall, windows 17 dB

concrete wall, no windows 30 dB

concrete wall within building 10 dB

brick wall 9 dB

armed glass 8 dB

wood or plaster wall 6 dB

window glass 2 dB

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In-Building Path Loss

� Simple path loss model for in-building environment

� Outdoor loss: Okumura‘s formula

� Wall loss

Lwall = f (material; angle)

� Indoor loss: linear model

For Pico-Cells

Lin = L0 +(loss per meter)*d

building type loss application example

old house 0,7 dB/m (urban l)

commercial type 0,5 dB/m (modern offices)

open room, atrium 0,2 dB/m (museum, train station)

Lout

Lwall

Lin

� The mean building penetration loss is a function of the height of the building. According to record, the gradient of loss line is -1.9 dB/floor. The mean building penetration loss of the first floor is about 18 dB in urban area and 13 dB in rural area. Tests show that the indoor loss has the characteristics of loss waveguide with attenuation. For example, when the wave transmits along the corridor direction vertical to outdoor window, the loss is about 0.4dB/m.

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Coverage Model in Door�“f” indicates frequency (MHz)

�“d” indicates distance (m)

�“Lf” indicates penetration loss factors between floors (dB)

�“n” indicates the number of floors lying between the mobile station

and antenna.

� “N” indicates distance loss factor

28)(lglg20 −++= nLfDNfL

� This model is recommended by ITU, it is for indoor coverage.

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Typical N Value

2232281800-2000

203330900

Shopping mallofficehousefrequency MHz

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Typical Lf Value

6 + 3 * n-115 + 4 * n-14 * n1800-2000

-9 1 floor19 2 floor24 3 floor

-900

Shopping mallofficehousefrequency MHz

� “n” indicates the number of floors lying between the mobile station and antenna.

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Indoor Coverage Solutions

� Small BTS

� Mini BTS

� Repeater

� Active

� Passive

� Optical

� Antennas

� Distribute antenna

� Leaky cable

� Signal distribution

� Power splitter

� Optical fiber

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Indoor Planning

Example2:1.2 MHz allocation50 mErl/subscriber , GOS=2%reuse per two floor, separate frequencies within one floor:a) three floors

52.12 Erl => 842subsb) ten floors

140 Erl => 2808 subs

Example1:1.2 MHz allocation50 mErl/subscriber, GOS=2%no frequency reuse:

a) three floors34.68 Erl=> 694 subscribers

b) ten floors34.68 Erl => 694 subscribers

Single cell approach Multi-Cell approach

t

f5f6f5

f1f2f1

f3f4f3f1..f6

f1..f6f1..f6

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Indoor Coverage Examples

� With Repeater

� Relay outdoor signal into target building

� Need donor cell, add coverage but not capacity

� With indoor BTS and distributed antenna

� Heavy loss bring by power splitting and cable

1:1

50m

50m

1:1

50m

50m

1:1

50m

50m

1:1

50m

50m

1:1

50m

50m

1:1

1:1:1

1:1

4th floor

3rd floor

2nd floor

1st floor

ground floor

Outdoor AntennaGain: 18 dBi

Indoor AntennaGain: 9dBi

Target Indoor Coverage Building

7/8'' Cable Loss: 4dB / 50mCable length : 25m

-50 dBm

4th Floor

3rd Floor

1st Floor

Ground Floor

2nd Floor

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Repeater� Application examples

� Coverage for low traffic area

� Remote valley

� Tunnel

� Underground coverage

needsdecoupling > amplification

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Wave Propagation in Tunnels� The tunnel types include railway tunnel (or metro tunnel), highway

tunnel.

� Highway tunnel is wide, select the antennas with a larger size to

obtain a higher gain, coverage distance is larger.

� Railway tunnel is narrow, the antenna size and gain are greatly

restricted. Especially the radio propagation is greatly affected by

passing train.

� The tunnel types include railway tunnel, highroad tunnel, and underground railway tunnel. Each tunnel has its characteristics, and they are specified as follows.

� For the highroad tunnel, it is wide. The coverage in the highroad tunnels is relatively stable. When there are vehicles passing by, you can select the antennas with a larger size to obtain a higher gain, so the coverage distance is larger.

� For the railway tunnel, it is narrow, especially when there is a train passing by; only a little room is left in the tunnel, so the radio propagation is greatly affected. Moreover, the train has great effect on radio signals. Since the antenna installation room is quite limited, the antenna size and gain are greatly restricted. In addition, because general cars cannot be driven to such tunnels, the tunnel coverage is hard to be tested. Therefore, the planning for highroad coverage is different from that of the railway coverage.

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Short and Middle Tunnels Coverage

� Generally, the tunnels shorter than 100m are defined as short

tunnels. l the antenna can be installed at the tunnel entrance so as

to ensure coverage.

� For the tunnels shorter than 500m, can use the combination of a

micro base station and a single antenna (or a repeater) for the

tunnel coverage, and install the antenna in the middle of the

tunnel.

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Long Tunnels Coverage

� For the tunnels longer than 500m, you need to use the distributed

antenna system or the leaky cable for the coverage.

� For the coverage of still longer tunnels, use amplifiers to amplify

signals. That is, you can use either the distributed antenna system

or the leaky cable for the coverage solution. In terms of technical

indexes and installation space, coverage solution based on leaky

cable is recommended.

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Tunnels CoverageIf outside tunnel and within the tunnel belong to the difference cell,

handover problem will occur. To solve this problem, can consider

adopting the following methods:

� Adopt the bi-directional antenna for the tunnel coverage, because

it can provide enough overlapping area for handover.

� Enable special handover algorithms, such as fast level fall

handover algorithm. In this case, a mobile station can hand over

to another cell when the signal level falls fast.

� Select the directional antenna with small front-to-back ratio.

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Contents

1. Planning Basis


3. Advance Planning

4. Advance Technology for improving

Coverage Planning


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Transmitting diversity

TDMA Frame

Delayed

TDMA Frame

TDMA Frame

1~2 Symbols

TRXB

TRXA

�

� The two downlink path transmitter signal have some time delay even if we use double polarization antenna, the MS also can combined the two signal in the equalizer.

� Improve the downlink BCCH TRX downlink performance

� Improve the downlink TCH TRX downlink performance in RF hopping or No RF hopping

� Especial for stationary and slowly moving MS

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� Two TRXs transmit the same signal with 7.4us time delay.

� Improving downlink coverage based on mutual exchange theory.

� Generally 3dB downlink gain from transmitting diversity.

Transmitting diversityTRXA

TRXB

� Two TRX transmit the same signal with 7.4us delay between. Generally 3dB downlink gain out of transmitting diversity

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� After dividing, the signal of carrier 0 will be sent to TRX1 and TRX2.

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Coverage Planning


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PBT(Power Booster Technology)

� Adopt the in-phase synthesizing technology.

� Generally PBT can generate 2dB downlink gain.

PA

RF

PA

Synthesizer

DU

PLE

X

RF

BB

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Dynamic PBT

� This technology is based on timeslots, allows a calling subscriber

to use a timeslot in other TRX.

� When the receive level is lower , channels corresponding to

identical timeslots in adjacent carriers stop delivering services

temporarily.

� At this time, the RF channel in the service timeslot and the

auxiliary channel in the adjacent carrier transmit identical signals,

whose phase is also the same. The combined signals are stronger,

thus improving the receiving quality for the subscriber.

� This technology is based on timeslots, allows a calling subscriber to use a timeslot in other TRX. A measuring report is used to monitor this subscriber’s downlink receive level. When the receive level is lower than the preset threshold, Channels corresponding to identical timeslots in adjacent carriers stop delivering services temporarily. The related RF channel provides PBT as an auxiliary channel. At this time, the RF channel in the service timeslot and the auxiliary channel in the adjacent carrier transmit identical signals, whose phase is also the same. The combined signals are stronger, thus improving the receiving quality for the subscriber.

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PBT(Power Booster Technology)

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4-way receiving diversity

Compared with 2-way receiving diversity, 4-way receiving diversity gets more 3~5dB uplink gain.

RF1

RF2

RF3

RF4

BB

>120%R

2WRD

4WRD

R

�

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TCH/AHS4.75

TCH/AHS5.15

TCH/AHS5.9

TCH/AHS6.7

TCH/AHS7.4

TCH/AHS7.95

AMR-HR

Experiment 1b - Test Results

1.0

2.0

3.0

4.0

5.0

Conditions

M OS

Sel. Requir.AMR-HREFRFRHR

Sel. Requir. 3.99 3.99 3.99 3.14 2.74 1.50

AMR-HR 4.11 4.04 3.96 3.72 3.38 3.10 2.00

EFR 4.21 4.21 3.74 3.34 1.58

FR 3.50 3.50 3.14 2.74 1.50

HR 3.35 3.24 2.80 1.92

No Errors C/I=19 dB C/I=16 dB C/I=13 dB C/I=10 dB C/I= 7 dB C/I= 4 dB

AMR

� High voice quality than HR and good customer experience.

� Low C/I requirement and easy to network planning.

� More robust than HR and stronger anti-interference.

� Increase 80%~140% network capacity and decrease CAPEX of network.

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Gain of Advance Technology

3~5dB(uplink)4-way receiving diversity

5dB(when EFR lower than

5%,compare with FR)

AMR

2dBPBT

3dBTransmitting diversity

Gain

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The Function of Extended Cell� In the GSM specifications, the cell coverage is restricted within 35km(63

TA) . Thus, the coverage radius of the cell cannot exceed 35km. In wide

and open area where the subscribers are dispersedly distributed, the

traffic is low, and the infrastructure such as transmission and power

supply facilities is hard to construct or cannot reach, the cell with a radius

larger than 35km must be provided.

� If the extended cell technology is adopted, the cell coverage radius can

reach 120km in an ideal condition. Operators can adopt this technology to

reduce the number of sites and build their own GSM networks quickly

with smaller investment. In this way, they can attract mobile subscribers

in special areas and thus increase the operation revenue.

Coverage Planning


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��

��

��

��

��

Timing Advance (TA)

� Transmission delay is unavoidable in the radio interface. If the mobile station moves away from the base station during a call, the further distance the more delay. The uplink is as the same.� If the delay is too high, the timeslots of the signal from a certain mobile station and that of the next signal from another mobile station received by the base station will overlap each other, thus causing inter-code interference. To avoid this, during a call, the measurement report sent from the mobile station to the base station carries a delay value. Moreover, the base station should monitor the time when the call arrives and send an instruction to the mobile station via the downlink channel every 480ms so as to inform the mobile station the time of advance transmission. This time is the TA (timing advance), which ranges between 0~63 (0~233�s ). The TA value is limited by the timing advance code 0~63bit of the GSM system. Therefore, the maximum coverage distance of the GSM is 35km. Its calculation is as follows:� 1/2*3.7 �s /bit*63bit*c=35km� {In the formula, 3.7�s /bit is the duration per bit (156/577); 63bit is the maximum bit number of the time adjustment; c is the light speed (transmission speed of the signal); and ½ indicates that the go and return trip of the signal.}� According to the above description, the distance corresponding to 1bit period is 554m. Influenced by the multi-path propagation and MS synchronization precision, the TA error may reach up to about 3bit (1.6km).

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Dual Timeslot Extended CellDelay<=63

After TA adjustment

After TA adjustment

Timeslot0

Timeslot0

Timeslot1

Timeslot1

Timeslot2

Timeslot2

UL data

Delay >63

Modulation range

Normal cell

Dual timeslot extended cell

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Dual Timeslot Extended Cell

� To support MS signals with a delay exceeding 63bit, the 2-

timeslot cell can bind the even and odd timeslots, as if a

TDMA frame in the extended cell only has four channels:

0/1, 2/3, 4/5, and 6/7. Only channel 0, 2, 4, and 6 can be

assigned for the MS.

B0 B2 B3B1 B4 B5 B6 B7

0/1 2/3 4/5 6/7

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Dual Timeslot Extended Cell� The dual-timeslot function is based on the concentric cell. The carrier in

the underlay cell is configured as the 2-timeslot carrier. The carrier on the overlay cell is configured as a common cell. When the cell is configured as a 2-timeslot cell, the concentric cell attribute of this cell is automatically set to the concentric cell.

� If all carriers in the cell must be configured as 2-timeslot carrier, such solution is called the cell-level 2-timeslot solution. In this case, all carriers are configured in the overlay cell.

� If some carriers in the cell are configured as common carriers and others as 2-timeslot carriers, the BCCH is located on the 2-timeslot carriers, such solution is called carrier-level 2-timeslot solution. In this case, the 2-timeslot carriers are configured in the underlaid cell and the common carriers are configured in the overlaid cell.

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Question

� What is the max value of extended cell’s TA?

Max TA?Max TA?

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Assignment of Extended Cell

UnderlaidIn-coming BSC HO

UnderlaidIntra-BSC HO

Depend on “assign optimum layer”Assignment

UnderlaidImm-assignment

Assignment StrategyType

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Configuration

� Modify the cell as double timeslot extended cell.

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Configuration

� Configure the TRX as overlaid or underlaid.

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Summary

� In this course, we have learned:

� Propagation and planning basis

� Coverage planning method

� Indoor and tunnel planning

� Planning procedure and site location

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Thank youwww.huawei.com

huawei 2g coverage planning.pdf

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