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S-72.3270 Radio Network planning

Lecturer: Prof. Riku JänttiAssistant: M.Sc. Mika Husso

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Tentative schedule & contents

Introduction to the assignmentNo lecture9

Frequency planning6. Network planning and optimization tools8

Coverage planning5. Frequency planning: Channel allocation methods7

Capacity planning

4. Frequency planning: Frequency resuse, reusepartitioning6

No exercise3. Coverage planning: Linkbudget, coverage probability5

No exercise2. Capacity planning: Trafficmodeling, blocking and dropping4

No exercise1. Introduction: Radio networkplanning process3

ExerciseLectureWeek

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Lecture 1.• Cellular radio systems• Objectives of radio network planning• Radio network planning process

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Cellular radio system• Bandwidth is a scarce resource which needs to

be divide among the users• In practice all multiple access schemes

introduce co-channel interference which limits the spatial reuse of the resources.

• Cellular radio concept (Bell Labs, 1943)– Service area of single base station is denoted as a

cellSame frequency can be reused inspatially separates cellsFDMA/TDMA

NMT, GSM, TETRA,…

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CDMA Revolution (Qualcomm, 1979)

• In CDMA, all cells use the same frequency. (Universal reuse)

Andrew J. Viterbi, ”Spread Spectrum Communications: Myths and Realities,” IEEE Communications Magazine May 1979, Volume 17, Number 3

IS-95, IMT2000, WCDMA,…

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OFDM Systems• OFDM allows flexible utilization of recourses:

partial reuse, reuse partitioning, dynamic channel assignment

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FlashOFDM, WiMAX, LTE,…

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Objectives of radio network planning1)To obtain sufficient coverage over the entire

service area to ensure that high quality voice services and data services with low error rates can be offered to the subscribers.

2)To offer the subscriber traffic network capacitywith sufficiently low blocking and call droppingrate.

3)To enable an economical network implementation when the service is established and a controlled network expansion during the life cycle of the network

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Impact of user environment (mobility)• Vehicular

– Efficient antennas and larger transmitter powers available in car mounted mobile stations

– Frequent handovers due to fast mobility– Fast fading cannot be tracked by radio resource

control (RRC) schemes• Pedestrian

– Antenna shadowed by the head– Battery life imposes power constraints– Fast handovers in e.g. indoor – outdoor movements– Fast fading can be tracked by RRC

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Impact of user environment (traffic)• Low to moderate traffic

– Large cells– Stretched cells along roads – Coverage planning based on subscribers

• Build coverage only to dense populated areas• Sparse networks: Build coverage incrementally based on

subscribers

• Heavy traffic– Small cells– Multilayer networks

Cell size

Traffic

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Impact of user environment (traffic)Background class

Interactive class

Streaming class

Conversational class

Traffic class

Download, Emails

web browsingStreaming video

VoiceExample of the application

-Destination is not expecting the data within a certain time

-Preserve payload content

- Request response pattern

-Preserve payload content

- Preserve time relation(variation) between information entities of the stream

- Preserve time relation(variation) between information entities of the stream- Conversational pattern (stringent and low delay )

Fundamental characteristics

Non-real-time,Best effort

Real-timeTiming

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Impact of user environment (traffic)• Traditionally cell planning has only been done

for voice traffic• Traffic classes have different requirements for

grade of service (GoS) and thus need to be considered separately in the planning.– Voice traffic typically requires high coverage

probability and low call dropping probability while background data traffic could be designed to have smaller coverage and higher drop rates.

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Impact of user environment• Remote areas such as wilderness and sea

areas– Low carrier frequency => large coverage area– High base station masts– Efficient antennas in the mobiles– Satellite systems*

*) Out of the scope of this course

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Planning approaches• Planning according to final network capacity

– all base stations are immediately built– transceivers (channels) are added when traffic

increases– Investment cost of the network is high– Unless the expected traffic is very high, the time to

break even is going to be long

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Planning approaches• Gradual improvement:

– In the staring phase of a network • traffic is small and cell size is mainly determined by the

propagation conditions, available power and receiver sensitivity (link budget).

• coverage is often build first on densely populated areas and along the highways. In the latter case highly directional antennas can be utilized.

– When the traffic increases more capacity can be obtained by using cell splitting, cell sectorization(directive antennas) and by decreasing cell size

– Investment costs increase gradually as the traffic increases

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Increasing the capacity• Sectored cells: Use directed instead of isotropic

antennas (Requires three antennas per cell site)

Sector 3

Sector 1

Sector 2

Node B Radiation patternof the antenna

Ideally, there is no interferencebetween the sectors.

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Isotropic antennas

Interference sources

extI

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Sectored cells

Interference sources affectingsector 3

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Sectored cells180 deg. sectors

120 deg. sectors

90 deg. sectors

60 deg. sectors

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Sectored cells• Capacity per sector (120 degree sectors)

– Theoretical capacity is three times larger compared to the isotropic antenna case

– In practice, the antennas leak power to neighbouring sectors as well, which decreases the capacity gain.

– All sectors require their own pilot signals => Signalling takes more power

– If all the sectors have a common power amplifier, only 1/3 of the maximum power is available per cell => Capacity increase is small

– If all the sectors have their own power amplifier, the capacity increase is notable 3

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Cell splitting

CELL SPLITTING 1:4 FINAL CELL LAYOUT

ORIGINAL CELL LAYOUT SPLITTING 1:3

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Hierarchical design• Macrocell:

– Large coverage area– Low bit rates (144 kbit/s)– High transmit power– Cell radius up to several

kilometers– Rural areas, suburban, city-wide

coverage• Microcell:

– Moderate coverage area– Moderate bit rates (384 kb/s)– Moderate transmit power– Cell radius up to a few kilometers– Urban area

• Picocells:– Small coverage area – High bit rates (up to 2 Mbit/s) – Small transmit power– Cell radius hundreds of meters– Hot spots / indoor

Macrocell Microcell

Picocell

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Hierarchical design• In metropolitan areas microcells and picocells

may be employed leaving the macrocells as umbrella cells. A geographical area may be covered simultaneously by all these cell types creating a multilayer network.

• Micro, macro, and picocells use different frequency bands even in CDMA systems to avoid frequent handovers, pilot pollution and near-far problems.

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Novel network planning approaches• New high data rate services impose new

network planning challenges.• High data rate services require small cells • Providing any-time-anywhere broadband

services (i.e. almost full coverage) would require lots of base stations and thus be very expensive

QPSK, 1/2QPSK, 3/416QAM, 1/216QAM, 3/4

Anders Furuskär, Radio Resource Sharing and Bearer Service Allocation for Multi-Bearer Service, Multi-Access Wireless Networks, PhD Thesis, TRITA-S3-RST-0302, Radio Communication Systems, Dept of S3, KTH, April 2003.

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Hotspots• Coverage limited, hot spot services

– High capacity is provided only in areas where the traffic intensity is high.

– Outside the hotspots, only low data rates are supported

– ABC: Always best connected paradigm: Service is provided using multiple radio interfaces. E.g. by using wireless local area networks (WLANs) in the hotspots and traditional cellular neteworks to support mobility and wide area coverage.

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Wireless relays• Range extension using wireless relays and

mesh networking– Wireless relay or router forwards information between

user equipment and base station.– There is no direct connection from the relay to the

core network.

R32

Same high data rate coverage

relay

relayrelay

relay

relayrelay

BS/AP

BS/AP

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Wireless relays– (Non-cooperative) Relaying operation consumes

radio resources so the relay network has significantly less capacity than the same amount of base stations would have.

– Wireless relays do not require connectivity to the core network which saves in cabling costs.

– The complexity of the relay can vary from simple amplify and forward repeater to wireless router implementing most (if not all) the base station functionalities.

– Cell sites for wireless relays could be e.g. lamp posts, rooftops etc. (where ever power supply can be easily arranged).

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Wireless relays– Usefulness of the relaying concept depends on the

cost ratio between base station and relay.

H. Yanikomeroglu 2006

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Network planning approaches• Gradual capacity improvement using mesh

networks– To save in wiring cost, the initial deployment in low

traffic network could be based on a mesh network where only a subset of the nodes are connected to the core network.

– To provide more capacity, the wireless routers can be turned to base stations by providing them access to the core network (e.g. by using high capacity optical network or high capacity microwave link)

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Network planning• Starting points for the planning procedure

– Desired grade (quality) of service• Capacity, coverage, call dropping rate, call blocking rate,…

– System specification• Utilized bandwidth, carrier spacing, modulation and coding

schemes, multiple access method, signaling methods,…

– Equipment specification• Radiation patterns of the antennas, number of supported

channels, available power

– Available frequency band• Depends on licenses provided by the regulatory authority

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Network planning– Topography and morphography of the service area

• Terrain height varations, nature of the ground cover (woods, open area, built-up area) building heights and density,… [anything that affects radio propagation]

– Traffic distribution and forecast• Geographic distribution of traffic and its expected growth.

Some areas such as shopping malls, airports etc. are natural hotspots with high traffic intensity while some areas like woods have very little traffic.

– Existing infrastructure• Existing antenna masts, equipment shelters, electric lines,

and roads should be utilizes as efficiently as possibly

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System specifications• frequency bands• carrier spacing• duplex spacing• access method• service types and rates• modulation and coding• sensitivity levels for given transmission performance in different

environments• protection ratios for given transmission performance in different

environments• network tuning parameters for radio resource control (e.g. power

control and handover)• …

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System specifications

CDMA

TDMA

FDMA

single ratecircuit switchedsymmetric links

multi-ratepacket switchedasymmetric links

hard capacityhard handover

soft capacitysoft handover

capacity andcoverage ratherindependent

capacity andcoverage inter-related

RNMP_intro.dsf

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Grade of Service (GoS) parameters• Coverage efficiency: Average base station coverage km2/number of

base stations• Area location probability/coverage probability

Probability that a randomly positioned UE can be served with certain QoS level (usually stated in term of Signal-to-interferece+noise ratio SINR)

• Received power (noise rise, load factor) [important in CDMA systems]

• Capacity kbs/Hz/cell• Throughput kbs• Outage probability

Probability that a user can not achieve its QoS target (usually stated in terms of SINR)

• Blocking probabilityProbability that a new user is denied access to the network

• Dropping probabilityProbability that a on-going call is terminated due to overloading.

• …

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Phases of the planning procedure1. Capacity planning based on the actual network

specification, traffic information, available bandwidth,and GoS (blocking and dropping). The output of this phase is the preliminary capacity plan giving cell sizes and number of channels in each cell.

2. Coverage planning based on the results of the preliminary capacity plan, equipment specifications,system specification, especially the required receiver sensitivity. The output of the coverage plan are e.g. equipment parameters needed to obtain a specified coverage percentage or the coverage prediction with given equipment parameters.

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Phases of the planning procedure• Frequency planning based on the results from the

capacity and coverage planning. In addition, protection ratios for co-channel and adjacent channel interference,usually given in the system specification, are needed. With same methods as in the coverage planning the frequency reuse distance is determined. This information, together with rules for the use of adjacent carriers, is used to make channel allocation to the base stations.

In CDMA-networks very little frequency planning is needed (only for hierarchical cell layouts). Instead a code reuse planning is neded.

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Network planning processDimensioning•Coverage plan(Link budget)•Capacity plan (Erlang capacity)•Frequency plan

Operators GoSrequirements

Area typePropagationconditions

Network planning•Simulation•Visulisation•Optimisation

•Rough number of base stations•Rough estimate of Base station

sites and their configuration

•Site selection•Base station configurations•Parameters for RRM algorithms•Capacity and coverage estimate•QoS

Measurements of networkperformance

Tuning of RRMparameters

Network optimization

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