Radio Access Network Planning Guidelines v2

RADIO NETWORK PLANNING GUIDELINESDocument No. VEL/PLANNING/01/2009 Rev.2.0

VersionDateName/Dept.Created byReviewed byApproved by

1.013.03.2007Access NetworkSitapathy ChavaliNaresh Gupta

2..005.02.2009 Access NetworkRitesh Agrawal Murali ChitturiSitapathy ChavaliNaresh Gupta

Version HistoryINDEX

1RADIO NETWORK PLANNING GUIDELINES

51Introduction

62Spectrum & frequency planning

62.1Channel allocation

62.2Carrier separation

72.3Carrier planning

72.3.1Multi-site towns

82.3.2Single site towns

92.4Spectrum Utilization Efficiency (SUE)

103Carrier dimensioning

144Coverage levels

144.1Link Budgets

154.1.1900 MHz band (for reference)

164.1.21800 MHz band (for reference)

164.2Roaming sensitive locations

175Antenna & Feeder cables

175.1Antennas

185.2Feeder cables

196Dual Band (900/1800) planning

227BTS

227.1Site types

227.1.1Outdoor/Indoor

227.1.2Macro/Micro

227.1.3Tower top BTS

227.1.4Street pole BTS

237.2BTS Capacity Optimization

247.3Handover and Power Control

247.3.1Handover Types

257.3.2Handover Criteria

257.3.3Adjacencies

267.4Data network configuration

267.4.1Timeslot configuration

267.4.2DAP Pool capacity

277.4.3PCU capacity

277.4.4Gb Link capacity

288BSC

288.1Location

298.2BSC Capacity

308.2.1Trigger points for BSC enhancement

318.3BSC Capacity optimization

318.4Location Area Design

328.4.1Paging vs. Location Updating Traffic

338.4.2LAC size and border

358.5BSS Parameters

369Transcoder

369.1Location

369.2Capacity

389.3Pool configurations

389.3.1Trigger points for enhancement

3910Site Planning

3910.1Radio planning

4110.2Transmission network planning

4110.3Pre - planning

4210.4Nominal Planning

4210.4.1Pre-Survey / SARF

4310.4.2Site Survey

4310.4.3Site Acquisition Report

4310.4.4Site Pre-Validation

4410.4.5Technical Site Survey Report

4410.4.6Site Validation & Deviation

4510.5Detailed Network Planning

4510.5.1Radio Planning

4610.5.2Transmission Planning

4710.5.3Co-site Planning

4710.6Site Implementation Data

4810.6.1Site Implementation Report

4810.6.2Site Integration Data

4810.6.3Site Verification

4910.7Site passive infrastructure sharing (with other operator)

5011Capacity planning

5011.1Capacity Requirements

5111.2Capacity rollout tracking

5212Network enhancement features

5212.1Coverage enhancement solutions

5212.1.1ICE (Intelligent Coverage Enhancement)

5212.1.2SRC (Smart Radio Concept)

5412.1.3Two (2) Port Antenna Combiner By-pass

5512.1.4Four (4) Port Antenna Combiner By-pass

5612.1.5High Gain Antenna [20dBi, 65]

5712.1.6TMA

5712.1.7TMB

5712.1.8Tower Top BTS

5712.1.9Repeaters

5912.2Abis Compression solution

6112.3VSAT Abis connectivity

6212.4Mobile BTS station

6413Energy Saving Guidelines

6413.1ULTRA EDGE BTS

6413.1.1Shiner Frisco Trx

6613.1.2LTCD (Low Traffic Controlled Disconnect)

6813.1.3Hybrid Solution (Ultra 2/2/2 to Flexi 4/4/4)

6913.1.4Co-Siting Solution (Ultra 4/4/4 to Flexi 6/6/6)

7013.2FLEXI EDGE BTS

7214Network Optimisation

7214.1Key Performance Indicators

7514.2Performance Evaluation

8614.3Interference Reduction

9014.3.1Antenna tilting /reorientation /beamwidth reduction

9014.3.2Discontinuous transmission/reception (DTX)

9114.3.3Frequency hopping (FH)

9214.3.4Power control (PC)

9314.3.5Adaptive antennas

9414.3.6Dynamic channel allocation algorithms

9514.3.7Antenna Hopping

9814.3.8Bi-Sector Antennas - TenXc

10214.3.9SAIC (Single Antenna Interference Cancellation)

10414.3.10STIRC (Space Time Interference Rejection Combining)

1 IntroductionThis document lists out various radio network guidelines in planning, performance enhancement, optimization, efficiencies (capax & opex.) to be adhered to all VF-IN circles with NSN BSS equipment. Any deviation from these guidelines would require specific approvals.

2 Spectrum & frequency planning

2.1 Channel allocation

Channel allocation for GSM system given in table below

BANDGSM 900GSM1800E-GSM 900

Uplink890 9151710 1785880 - 890

Downlink935 9601805 1880925 - 935

Channel1 - 124512 - 885975 - 1023

2.2 Carrier separation

Guidelines for minimum separation between carriers:

BCCH carriers

1) Separation between BCCH carriers within same site : 600 KHz

2) Separation in BCCH carriers between different sites in same cluster : 400 KHz3) co-channel C/I : 12 dB4) adjacent channel C/A : -9 dB

TCH carriers1) Synthesized Frequency Hopping (SFH) with 1/1 frequency reuse pattern to be used to increase the network capacity. 1/1 frequency planning means that all hopping TCH frequencies are used in all cells.2) Frequency plan for hopping layer should be generated based on actual C/I field measurements data captured from OSS over a period of 7 days. Frequency plan should include new sites and/or new TRX planned over next 1 month. Appropriate advanced frequency planning tools capable of carrying out non-uniform frequency plans to be used.

3) MA List (Mobile Allocation List): To be allocated per cell & decided locally depending on frequency planning tool used and & no of TCH channels available.

4) HSN (Hopping Sequence Number): To be allocated per site from the GSM standards.

2.3 Carrier planning2.3.1 Multi-site towns

Since BCCH (Broadcast Channel) is required to be continuously available, no frequency hopping can be deployed on this channel. 4/12 reuse is recommended for optimum performance. This means a cluster of 12 cells (4 sites) will have a set of BCCH frequencies to be used within that cluster and the same plan is replicated in all such clusters of 12 cells each. Frequency loading

In frequency hopping, each frequency is used by a fraction of the time. This fraction of time is dependent on number of hopping frequencies. Frequency load indicates the fraction of time a frequency is being transmitted by a cell.

The frequency load is defined as:FRload = Average (Erlangcell) / (8 x #Hopping Frequencies)

BCCH traffic should be excluded for calculation. BCCH is always radiating & therefore there is 100% frequency load on BCCH.

Following table gives maximum configuration & corresponding frequency load per cell:Spectrum (MHZ)Total carriersNo of BCCH carriersNo of carriers for guard bandNo of carriers left for TCHBTS configuration (max)Total Erlang per site (FR)Designed frequency load (%)

4.42212193/3/238.0010.8%

6.231122174/4/463.1212.2%

7.236122225/5/477.5411.8%

8.241122276/6/597.6113.1%

9.246122327/6/6111.4813.1%

10.251123367/7/7126.3613.3%

11.256123418/8/8146.1014.0%

12.261123469/9/8161.2413.8%

13.2661235110/10/9182.1514.3%

14.2711235611/10/10196.4914.2%

15.0751236011/11/11211.8314.3%

BCCH carriers for micro/Ibs can be use for macro BCCH plan if required. Circles may have variations due to use of more carriers for micro, Ibs and/or guard band. All such variations can be considered for frequency planning.

All networks to make sure that loading as per the above guidelines is achieved before new capacity only sites are planned in the network.

It is not technically feasible to load all sites in a town with max possible configuration indicated above. Doing such will result in high interference and hence degrade the network quality. Therefore typical traffic loading should be 84% of maximum capacity & the frequency load for a cluster should not more than 10% to 12%2.3.2 Single site towns

For single site towns, there is no cluster for frequency re-use & therefore it is possible to have higher site loading. Frequency hopping is not required. The following figure gives the carrier planning for single site town.

Spectrum (MHZ)Total ARFCNBCCH carriers (Nos.)No of carriers for guard bandTCH carriers (Nos.)TRX configuration (max.)) Erlang per site (FR)

3.4173593/3/344.67

4.02035123/3/450.81

4.42235144/3/456.95

6.23135235/5/691.18

7.23635286/6/6104.04

8.24135337/7/7126.36

9.24635388/7/8139.52

2.4 Spectrum Utilization Efficiency (SUE)

As a measure to monitor how efficiently the spectrum is used and loaded in a network, following formula provides an objective method of calculating the same:

SUE = Offered erlang / (Spectrum in MHz x Area in Sq. Km)

SUE is measured in terms of erlang / MHz / Sq KmThis value is to be calculated for top-5 towns of a circle under following categories

Peak spectrum utilization efficiency

One square Km polygon of dense part of the town is to be considered. Offered FR capacity of all cells (macro/micro/IBS etc) within that 1 sq km to be taken.

Average spectrum utilization efficiency

Eight square Km. polygon of the town having maximum traffic is to be considered and offered FR capacity of all cells (macro/micro/IBS etc) within that polygon area to be considered.

Town nameParameterNos. of sitesOffered capacity (FR)SUE

(Erl/MHz/Sq Km)

Town-1Peak SUEWithin 1 Sq Km

Average SUEWithin 8 Sq Km

Town-2Peak SUEWithin 1 Sq Km

Average SUEWithin 8 Sq Km

These values will be benchmark against global standards

3 Carrier dimensioningSDCCH dimensioning:

SDCCH capacity of every cell should be planned is such a way that maximum SDCCH blocking should not exceed 1% GoS.

The below table comprises the recommended SDCCH configuration per cellTRX per cell (Nos.)Number of SDCCHSDCCH configurationNumber of SDCCH sub channelsSDCCH capacity@1%GoS [Erl.]

10Combined30.45

21Non-combined72.50

31Non-combined72.50

42Non-combined158.11









One signalling sub-channel is taken account for cell broadcast service (CBCH)Note:

1) For cells on LAC borders, additional SDCCH capacity may be configure on need basis.2) Dynamic SDCCH allocation feature should be enabled

3) Above indicated signalling capacity (SDCCH) is assuming a max of 20% HR traffic carried. However, networks having > 20% HR traffic may require higher SDCCH capacity.

TCH dimensioning:

The TCH capacity of every cell should planned in such a way that within the TCH busy hour the TCH blocking does not exceed 2% GoS.The below table comprises the recommended TCH capacity per cell at different dedicated time slots for data:

TRX per cell (Nos.)Number of SDCCHTCH capacity@2%Gos [Erl.]

0 Data TS1 Data TS2 Data TSL

102.932.271.65

218.27.46.61

3114.8914.0413.18

4221.0320.1519.26

5228.2527.3426.43

6334.6833.7532.83

7342.1241.1840.25

8448.747.7546.81

9456.2755.3254.37

10562.9461.9861.03

11570.0669.6468.68

12677.3476.3775.41

Half rate configuration20% capacity gain due to half rate should be considered.Total capacity = Capacity (FR) + HR gain

The voice capacity of a cell should plan in such a way that within the TCH busy hour, TCH traffic should not exceed 40% half rate.

Example: Consider two TRX cell with one dedicated data TSConfiguration without HR

BCSDTTTTTT

TTTTTTTDD

Offered FR capacity (excluding Data)

= 7.40 Erlang

Offered FR + HR capacity (excluding Data)= 7.40 x 1.2 = 8.88 Erlang TCH requirement (8.88@2%GoS) ~15Configuration with HR (20% extra HR-capacity)

BCSDTTTTTT

TTTTTDRDRDD

BC: BCCH

SD: SDCCH

T : TCH FR

DD: Dedicated data

DR: TCH Dual rate

FR: Full rateHR: Half RateBy making 2 FR timeslots as Dual Rate in this example, it is possible to get 20% half rate capacity gain. However HR trigger thresholds (FRU & FRL in case of Nokia) need to be suitably optimized. In the above example, setting FRU = 80% is enough to achieve 20% soft capacity. Similar implementation to be done for higher cell configurations

In Abis interface as a normal practice, 16 Kbps LAPD signalling is sufficient in case of any TRX having upto 18 channels (SD + TCH). However in case any TRX exceeds this limit of 18 channels, 32 Kbps LAPD needs to be configured.

In TCSM AMR pool to be suitably configured to support all of AMR traffic.Recommendation:

BTS expansions:

Delta erlang capacity calculation for enhancement of existing BTS configurations be taken as differential of higher and existing configuration.

Example: To calculate erlang added due to expansion of BTS from 3/3/3 to 4/4/4:

3/3/3 capacity = 44.7 erlang; 4/4/4 capacity = 63.12 erlangAdditional capacity obtained due to expansion = 18.42 erlang

Some typical expansion configurations are:Current BTSExpanded BTSDelta additionErl/TRX achieved

configurationErlang capacity (V+D)configurationErlang capacity (V+D)TRXErlang (V+D)

1/1/18.822/2/224.60315.785.26

2/2/224.603/3/344.70320.16.70

3/3/344.704/4/463.12318.426.14

4/4/463.125/5/584.75321.637.21

5/5/584.756/6/6104.04319.296.43

6/6/6104.047/7/7126.36322.327.44

For all other expansions not listed above, similar method of delta erlang calculation to be follow based on erlang table.

4 Coverage levels

Signal levels (on road) recommended for various clutters is as below:

Clutter typeOn road RSSI^Probability

900 band1800 bandVoiceData

Dense Urban*-65 dBm-62 dBm95%90%

Urban-70 dBm-68 dBm95%90%

Industrial-75 dBm-72 dBm95%90%

Suburban-75 dBm-75 dBm95%90%

Rural / open-85 dBm-85 dBm95%90%

* includes CBD, high-rise buildings and old city areas with narrow roads and thick building walls.

^ Receive Signal Strength Indicator

4.1 Link Budgets

Typical radio link budgets to be used for 900 & 1800 MHz networks are as below. Any variations from these need prior approval.

4.1.1 900 MHz band (for reference)

4.1.2 1800 MHz band (for reference)

4.2 Roaming sensitive locations

For locations like airports, railway stations, highway entry points, hotels etc, where roaming traffic is high, following guidelines are to be adhered to:

a. Receive signal strength in idle mode must be always better than -85 dBm at all the sensitive location.

b. Number of BCCH carriers should be equal or more than any other competitive network in that area.

c. BSS parameter (RXP) on min signal strength of access should be set to -110 dBm.

It is required that periodic comparative network testing is carried out at all roaming critical locations to ascertain adherence to the above norms. Some of the techniques by which more BCCH carriers can be added into a particular area are:

a. Adding new sites (macro or IBS)

b. Adding additional sectors within same sites (upto 6 sectors possible)

c. By splitting a sector (which is non-serving the roaming area) to provide coverage.

d. Changing antennas to high gain for sectors of neighbouring cells having lower BCCH levels.

5 Antenna & Feeder cables

5.1 Antennas

Antenna is a very critical part of the overall radio network design and hence proper selection of antennas is important to meet the planning objectives. Following antenna models are recommended for use in various clutter / coverage conditions described:

Note:

a. The above guidelines are indicative only for the type of application. However, specific antenna models not listed above can be used after prior approval.

b. All antennas to be used are of Electrical down tilt (continuously variable) only.

c. Detailed antenna models and vendors are as per Hutch approval process.

5.2 Feeder cables

Following feeder types are recommended for various feeder lengths at sites in both 900 & 1800 bands. This calculation is based on requirement of max 3.0 dB insertion loss of the feeder system,

GUIDELINES IN SELECTING FEEDER TYPE FOR DIFFERENT LENGTHS

Sr. No.Length Of the FeederCable Loss (dB/100 Mtr.)Connectorization and Jumper losses(dB)Feeder typeBand

1Up to 20 Mtr.11.60.5 dB*1/2" Super flexible Foam Dielectric900 MHz

220 Mtr. to 35 Mtr.7.120.5 dB*1/2" Foam Dielectric900 MHz

335 Mtr. to 50 Mtr.4.021 dB7/8" Foam Dielectric900 MHz

450 Mtr. to 70 Mtr.2.871 dB1 1/4" Foam Dielectric900 MHz

570 Mtr. to 90 Mtr.2.381 dB1 5/8" Foam Dielectric900 MHz

6Beyond 90 Mtr.2.061 dB2 1/4" Foam Dielectric900 MHz

7Up to 15 Mtr.16.60.5 dB*1/2" Super flexible Foam Dielectric1800 MHz

815 Mtr. to 25 Mtr.10.10.5 dB*1/2" Foam Dielectric1800 MHz

925 Mtr. to 35 Mtr.5.751 dB7/8" Foam Dielectric1800 MHz

1035 Mtr.to 50 Mtr.4.151 dB1 1/4" Foam Dielectric1800 MHz

1150 Mtr. to 70 Mr.3.451 dB1 5/8" Foam Dielectric1800 MHz

12Beyond 70 Mtr.3.051 dB2 1/4" Foam Dielectric1800 MHz

* no jumpers recommended

6 Dual Band (900/1800) planning

Dual Band:

Circles having licenses in two frequency bands are able to support the use of multi band mobile stations in both bands with use of the Dual Band feature. This is required especially when frequencies of one single band are limited.

Common BCCH Control:

The Common BCCH Control feature allows the integration of resources from different frequency bands into one cell. TRX of different frequency bands can be configure in the same cell by letting them share a common BCCH allocated from one of the frequency band used in the cell and resources across all bands are co-located and synchronized.

Segmentation:

Common BCCH Control & Dual Band utilizes the segment architecture, which introduces a segment radio network object (SEG). A segment may consist of one or more BTS objects. A BTS in a segment is a group of similar TRX in one frequency band only

The operator sees common BCCH segment as single cell even though parameterization and management has been partly separated between the BTSs of the segment. The MS also sees the segment as one BCCH frequency band cell because it has no knowledge of the other frequency bands in a segment due to the fact that these bands have no BCCH. The BSC allows up to 36 TRX and 32 BTS objects in a segment.

The band where the BCCH carrier is in the common BCCH controlled segments must be the same throughout the whole network. This ensures that the support for single band mobile stations remains in at least one of the frequency bands of operation. It is also possible that there are single band cells, in the network simultaneously with the multi-band common BCCH segments and the service to mobile stations is offered via these single band cells as well.

In a multi-band Common BCCH segment the Initial SDCCH channel for a call set-up is always allocated in the frequency band where also the segments BCCH is.

The multi-band MS and the multi-band network shall support Frequency Hopping within each band of operation. Frequency Hopping between the bands of operation is not supported.

The introduction of Common BCCH Control feature has not affected the basic structure of statistics. The measurements are still collected per BTS in the segment environment. The possibility to have frequency band-specific statistics and segment-specific statistics based on the BTS-specific measurements is offered by network service and OSS system.

Introducing the segment concept and the possibility to have several BTS objects in one cell causes changes in the data collection of some cell level activities and in the BTS-specific counter interpretation in the segment environment. The feature introduces some new counters for the supervision of intra-segment

TCH handover based on load, intra-segment TCH handover based on signal level, intra-segment handover between frequency bands and for the supervision of inter-segment handovers that are also handovers between separate frequency bands. These are implemented in the handover measurement and the BSC level clear code (PM) measurement.

Following are some NSN Major Parameters required to take care along with Dual Band, Common BCCH & Segment Feature to make Dual Functionality properly. Same parameters can be optimized to take full advantage of additional spectrum.

ParametersRangeNSN DefaultRecommended

multiBandCell (DBC)NoYes

earlySendingIndicationNoYes

multiBandCellReporting11

nonBcchLayerOffset40 to +40 dBm0 dBm

BTSLoadInSEG0...100 (%)70%

MsTxPwrMaxGsmFor GSM 800 and GSM 900: 5..39 dBm33

MsTxPwrMaxGsm1x00For GSM 1800 0...36 dBm with 2 dBm step30

nonBCCHLayerAccessThreshold90 dBm

nonBCCHLayerExitThreshold95 dBm

nonBCCHLayerExitThresholdPx2

nonBCCHLayerExitThresholdNx5...39 dBm with 2 dBm step333

intraSegSdcchGuard0 - 255 (s)255

Example:

Additional Capacity Gain due to availability of GSM 1800 spectrumSpectrumBandwidthNo. of ChannelsBCCH LayerSite ConfigurationMax. Site Configuration

GSM 9008.2 MHz41Yes6/5/57/7/7

GSM 18002.0 MHz10No1/2/2

Note: However to achieve better voice quality, some networks may limit number of TRX loaded on 900 band to 5/5/5 & increase 1800 band loading.

7 BTS

7.1 Site types

7.1.1 Outdoor/Indoor

Following aspects should be taken into consideration before choosing indoor / outdoor BTS models:

Availability of adequate space for shelter

Environment of use.

Shared sites

Far off / rural / highway sites

If that site is a transmission hub site OR a BSC location, shelter is required to be set up.

Outdoor BTS on tower top for better coverage.

Capacity considerations

Indoor BTS with 1 level of combiner shall be planned in areas wherein the capacity shall go beyond 12 TRX in any site within 1 Year or is part of DU, Urban and SU areas.

Outdoor BTS without any Combiner shall be planned in all new towns , HW , Rail Routes and also sites that will be less than or equal to 12 TRX /site in 2 Years.

7.1.2 Macro/Micro

Macro BTS: In areas of high traffic. ( ~12 TRX)

Micro BTS: Used for (a) small coverage footprint to offload macro sites, (b) In areas of low traffic (1 TRX ; Decision for IBS sites to be taken on case-to-case basis

DR in use (DR)"YES"

Trunk Reservation Used (TR)"No"

Call Reestablishment Allowed (RE)"YES"

Allow IMSI attach/detach (ATT)"YES"

DTX mode (DTX)"SHALL"

RxLev Access Min (RXP) a) -110 dBm for roaming entry cells & b) -105 dBm for all remaining cells

Radio Link Timeout (RTL) Recommended value is 20 SACCH frames. However depending on specific cell requirement and congestion levels in that cell, it can be set lower upto 12 SACCH Frames. Note: T 3109 timer should be greater than radioLinkTimeOut x 0.48 (in seconds).

Number of Blocks for AGCH (AG) a) 1 AG Block for cells with Combined mode (BCCH+3*CCCH+SDCCH/4) & b) 2 AG Blocks for cells with Non Combined (BCCH+9*CCCH)

MS TxPower Max GSM (PMAX1) 33 dBm

MS TxPower Max GSM 1800/1900 (PMAX2) 30 dBm

MS TxPower Min (PMIN) a) for 900 network : 5 dBm & b) for 1800 networks : 0 dBm

Max Number of Repetition (NY1) 5

Max Number of Retransmission (RET) 4

Number of Multiframes (MFR) 4

Timer for Periodic MS LUP (PER) Between 4 and 8 Hours depending on No. of LACs, size of each LAC, Subscribers per LAC, No. of Pages per LAC & MSC Proc. Load.

GPRS enabled (GENA) "YES" (depends on requirement)

Any variations from the above need to be pre-approved.

9 Transcoder

9.1 Location

Transcoders are usually collocated with the MSC to minimize the need for additional transmission media cost. In cases where the transcoders are utilized to 100%, the transmission media from the MSC can be extended to a remote Transcoder to relieve temporary congestion across the interfaces.

This chapter does not address TCSM capacity in case it is part of R4 MGW. That is addressed in Core network planning.

9.2 Capacity

Transcoder is to be dimensioned for the busy hour (BH) traffic on the radio interface with following considerations:

Total carried traffic should include FR + HR calls.

90% of Transcoder resources utilization to be considered.

GoS on A interface at 0.1%.

Any variations needed to these dimensioning guidelines need to be discussed and mutually agreed.

Following TCSM, models are available:

TCSM modelChannelsE1 towards MSCE1 towards BSCCapacity step

TCSM2i960328120 Ch

BSC3i combined with TCSM3i11,35838496960 Ch

TCSM3i11,52038496960 Ch

Product Specific Information.

Example of TCSM capacity calculation

No of E1 towards Abis

: 8

No of E1 towards A

: 32

Total circuits

: 960

Total voice circuits available: 896 excluding signalling overheads.

Transcoder to be dimensioned for 90% capacity utilization of circuits. Hence, one TCSM is planned to support upto 806 circuits or 742 Erlang at 0.1% GoS, which translates to 23.2 Erlangs/E1 towards MSC.

However it must be borne in mind that Transcoder can handle traffic upto 100% capacity.

AMR circuit pool needs to utilize 100% as any overflow calls get directed to EFR/ FR pool.

Example: For a network requiring additional 100 BTS (2/2/2) of radio capacity, following should be the Transcoder dimensioning:

Total radio voice capacity of the network = 22,200 Erlang Assuming 20% additional capacity due to HR, total offered radio capacity is equal to 26,640 Erlang.

Assuming 70% utilization of Radio capacity in BH, traffic = 18,648 ErlangTranscoder should be catered for supporting 18,648 Erlang of traffic. Transcoder utilization. Taking 742 Erlang/TCSM, no of TCSM required is 25 nos of 32E1 capacity

9.3 Pool configurations

At present following pools are being used in the network

CIRCUIT POOL NO 7

FR speech version 1

FR speech version 2

FR data (12, 6, 3.6 kbit/s)

HR speech version 1

HR data (6, 3.6 kbit/s)

CIRCUIT POOL NO 23

FR speech version 3

HR speech version 3

9.3.1 Trigger points for enhancement

When AMR pool reaches 100% utilization, additional capacity to be added into AMR pool from EFR.

When EFR pool is 90% utilized, then additional TCU or new TCSM is to be planned.

Note: Transcoder are not required for NSN circles with R4 deployment. NSN circles with core in R4 deployed, above transcoder guidelines will not be applicable

10 Site Planning

10.1 Radio planning

Radio coverage is frequently perceived to be the most important measurement for network quality. Radio coverage planning plays a major role in GSM network planning, because it decides extent of coverage area, speech quality, mobility and customer satisfaction. Various forms of inputs and limitations from the customer in terms of spectrum availability, network dimensions, frequency planning, network growth, local wireless regulations and finally the RF environment itself plays an important role in coverage planning. The approach for the coverage plan needs to be well defined since, it requires to accommodate various phases of network growth across time without any compromise on service quality goal. Some of the major steps involved in the cell planning are shown in figure below.

Site Planning Consists of Three stages:

Pre - Planning

Oriented at support from Customer Account Team.

Involves BoQ finalization

Nominal Planning

Decide Planning Strategy & Set Criteria for Planning

Prepare Nominal Coverage Plans

Detailed Planning

Site Surveys

Finalize Site Locations & Physical Parameters

Finalize Cell Configuration & Capacity

Prepare final Coverage Plots

Prepare Frequency Plans & Set Parameters

Perform Pre-launch Optimization Site Implementation Data

Site Implementation Report

Site Integration Data

Site Verification Report

10.2 Transmission network planning

Consists of Three stages:

Pre - Planning

Oriented at support Customer Account Team.

Involves BoQ finalization Nominal Planning

Decide Planning Strategy & Set Criteria for Planning

Prepare Nominal Transmission Plans (Network Topology)

Finalize BSC Locations

Detailed Planning

Site Surveys

Finalize Site Locations & Physical Parameters

Finalize Link Configuration & Capacity

Prepare final PCM Plans

Prepare Frequency Plans & Set Parameters

10.3 Pre - planning

Contains Network Dimensioning & System Configuration

BoQ is Finalised based on the inputs from the customer

Subscriber Forecast

Total Erlang to be built in the year

Traffic / User during Busy Hour (mErl)

VLR / HLR Ratio

BBH / NBH Ratio

Utilization Factor

Half Rate Usage Guidelines

New Towns to be covered

Subscribers forecast for the new towns

GPRS Data

Traffic in Hot Spots

Coverage Requirements

Frequency Spectrum

Network Availability for designing Transmission Network

Availability of leased lines if any

Blocking Probabilities

10.4 Nominal Planning

Performance of existing network is analyzed methods to rectify critical issues are identified

Nominal Coverage Plot is generated

Antenna System & Site Configurations are defined

Tentative Transmission Network Topology is drawn

MSC & BSC locations are defined

Nominal Plan is generated based on the Following Inputs

No. of BTS to be deployed

TRX Configurations

Coverage requirements as defined in Pre-planning

Frequency Planning Strategy

Network Performance Data

Inputs on use of Special Features

Inputs on Use of Ancillary Equipment (TMA, TMB, etc)

Repeaters must avoided as far as possible

Results of Nominal Planning

Nominal Coverage Plan Nominal Co-ordinate in UTM format

Site Code

Physical Parameters of the Site (Antenna Ht, Orientation, Tilt, etc)

Transmission Network Diagram

Media Selection

Capacity Requirement

2 Mb/s Plan & TS Plan

10.4.1 Pre-Survey / SARF

Tentative site locations & search rings are given.

Planning Team & Sales agree on the Coverage requirement and sign on the area map

Hot Spots to be covered

Area to be covered

Preliminary checks are done in the planning tool to identify possible LoS

10.4.2 Site Survey

Enables the planners to familiarize themselves with actual clutter / terrain

At least three preferred candidates to be identified

Obstructions to be check in all directions.

Panoramic photographs of the LoS is a must

Line of site to be check for all radio links

Preferred tower/pole locations to be identified & sketched Make changes to proposed Nominal plan if necessary

10.4.3 Site Acquisition Report

Provided by the Site Acquisition coordinator to the Planning Team based on the SARF & contains

Site Code

Correct Site Address

Building Height

SARF map indicating the site

Sketch of Roof area

Access to roof Photos

SAR is rejected / redone if information is incomplete

If all candidates are rejected, another option is found. This means

Changing the search ring if required

Revisiting the area

Redoing certain adjacent sites along with the revised SARF

GPS Co-ordinates, Addresses and Photos are a must for all options

10.4.4 Site Pre-Validation

Site candidates from SAR are prioritized and acceptance / rejection is given accordingly

Can also be done based on SARF Pre-visiting of sites needs to be done

Planners are recommended to visit the site before this report is generated

Desktop Pre-validation is allowed only if the planner is extremely familiar with the area

Following information is checked while selecting the candidates Clutter type / Terrain

Coverage requirements in the area

Capacity requirements in the area

Map studies to confirm LoS

Surrounding Area

Site Location in itself

Antenna Locations

Cable Lengths

Obstructions in the main lobe of the antenna

10.4.5 Technical Site Survey Report

Run for all active candidates in descending order of priority for the given site

Representatives from all departments should be present during this exercise

Planners would perform all required verification / tests

Check / review LoS

Antenna Height & Orientations

Radio Propagation Measurements (if needed)

Structural stability of the candidate

Capture information about other operators details in the same site if any Co-siting

Photographs are a must (every 30deg starting from 0deg and obstructions if any)

10.4.6 Site Validation & Deviation Done together with all relevant departments

Antenna System configuration is frozen

All site drawing are prepared

In case the site falls outside the search ring of RF Planner or does not meet the design criteria, the planners prepare a site deviation form and get it signed by the concerned parties responsible the deviation along with all other members of the TSSR

10.5 Detailed Network Planning

Starts as and when a site is acquired

Objective is to fix various Radio & TRS related parameters with the following

- Site locations

- Type of equipment

- Configurations

- Use of special features

Final Coverage plan is generated

Final Capacity is also generated

Frequency Plan is finalized Interference analysis are performed & Interference plots are generated

Parameters are planned

Transmission plan is frozen

2 Mb/s plan is finalized Transmission network Capacity & Topology plans are generated

10.5.1 Radio Planning

Coverage Plan

Contracted Site Locations

Antenna Directions

Cable Losses

Antenna Types

Antenna Heights

Indoor Coverage Plan

Outdoor Coverage Plan

Special BSS Features used Capacity Plan

Contracted Site Locations

Dynamic Hot Spots

Verified Hot Spots

Additional Fill-in sites if required

Frequency Plan

Allocated Spectrum

Frequency Hopping

Band for different layers

Plan for different layers

Reuse Pattern

Measurements

Location Areas

BSIC Planning

Special BSS Features used Interference Analysis

Adjacencies

Spectrum distribution

Hopping Frequencies

Guard Bands Parameter Planning

Default set of parameters are defined

Emphasis on creating the correct parameters given by the planner to avoid frequent optimisation later

Includes the following parameters

BSC, BTS, Cell, TRX Identification parameters

a) LAC

b) Cell Selection / Re-selection parameters

c) Handover parameters

d) Power Control parameters

e) Adjacent Cell parameters

f) Control of advanced system failures

Traffic distribution between layers to get optimal results

Handovers to be minimised to reduce load10.5.2 Transmission Planning (detailed guidelines to be issued by VF corporate Transmission team) Microwave Link Planning Performance calculations are made

Path Profile analysis is done

Frequency planning

Required Repeater locations are identified

LoS surveys are performed both on maps & on actual links

Results of this would include

a) Antenna heights and sizes

b) Antenna directions

c) Power levels (Tx / Rx)

d) Hop lengths

e) Performance calculations

2 Mb/s Planning

Traffic Routing across various nodes is done

Defines the traffic route through base stations / access network on a 2 Mb/s level


a) Transmission Network diagram on a 2 Mb/s levelb) Time slot & Cross-connect Planning

c) Time Slot usage is defined at the transport link

d) Needed branching and Cross-connections are planned

e) Time Slot allocation of transmission links

f) Branching & Cross-connection tables for the equipment with cross-connect functionality

Synchronisation Network Planning

Synchronisation plan is prepared based on the following inputs

Network infrastructure

Network architecture

National Clock distribution information


Timing sources & hierarchy level definitions

Network timing distribution definitions

Management Network Planning

Knowledge on management regions, existing infrastructure & detailed transmission network implementation plan are the input. Results would include network management diagram including

Information on management buses

Addressing of Managed Equipment

10.5.3 Co-site Planning

Extra care to be taken by the planner in this situation

Possible interference from other carriers to be analysed

Antenna heights & locations should be proposed in such a way that they do not obstruct each other

Site visit along with Radio Planner is a must

10.6 Site Implementation Data

Upon completion of detailed planning, planning team provides the implementation data to the following personnel

Logistics coordinator

Implementation Engineer

BSC Engineer

Planning team should ensure that data on the same site is being given to the various departments

10.6.1 Site Implementation Report

Submitted to the planning team by the implementation teams so that they can verify if the site has been implemented in accordance with the plan

Care should be taken to implement the site in strict accordance with the plan to avoid frequent optimisation and network degradation

Drive test teams are deputed based on this form

If changes are made to the original plan between the time implementation data was released and actual implementation, latest information to be shared with all the teams

10.6.2 Site Integration Data

During Site Implementation phase or immediately afterwards, Planning & BSC teams will create the site in the BSC database correctly

Planning team provides the Site Integration Data to the BSC / OSS team. It contains of

RF parameters

Neighbour relations

Necessary PCM information

10.6.3 Site Verification

After site integration, drive test teams perform drive tests and check the following

Coverage of the planned site

Call set-up & Call hold

HO Performance

Interference in the neighbourhood

Drive test teams should carry a coverage plot of the area and it is mandatory that a rigger must accompany the team.

Physical optimisation if any should be done before the site is put on air

Physical optimisation of neighbouring cells should also necessarily be performed before the site is put on air

The Planner also checks the dump from the BSC / OSS to ensure that the site has been created with the correct parameter settings

Any anomalies found should be immediately reported by the planner and he gets it rectified

10.7 Site passive infrastructure sharing (with other operator)

GSM Antenna: 900 MHz and 1800 MHz antenna shall be placed at least 0.3m distance.

GSM Antenna and CDMA Antenna: Vertical Antenna Separation of 3m is recommended.

BTS Equipments inside the Shelter can be placed next to each other.

Feeder Cable laying shall be done in such a way that no Sharp bends are observed. No compromise on this aspect is allowed.

Future Capacity Enhancement requirement shall be considered while sharing the sites. Space for at least one additional cabinet for our Own BTS be available after sharing.

Sharing Partners Future expansion plan shall be considering before accepting Technical Feasibility.

11 Capacity planning

11.1 Capacity Requirements

mErl/sub Calculations

Offered radio erlang capacity per subscriber to be calculated taking into consideration following parameters.

BBH / NBH Ratio

VLR (Active) / Marketing subscribers

NBH Erlang traffic / VLR (Active)

% NBH Radio capacity utilisation

% Half Rate traffic in NBH

Data network capacity (dedicated only)

Following formula to be used for offered Erlang capacity calculations

Definitions of various parameters used in the formula:

NBH Traffic: Maximum value of radio traffic in 1 hour across 24 Hrs a day. The hour to be considered will be same across all BSCs in that network.

In each hour of the day, radio traffic recorded from each BSC will be aggregated across the network. The hour (out of 24 Hrs) in which this aggregated radio traffic value is highest will be the NBH traffic value.

BBH Traffic: This is the aggregation of maximum radio traffic carried by each cell in the network in its busy 1 hour of the day.

VLR (Active): It is equal to VLR (Attached- own) + In roamers into the network. It is to be taken at the NBH time period of the day. Reported Subs: It is the number of subscribers reported by marketing. Data Configuration: It is percentage dedicated data capacity defined across the network. Recommended value for this parameter is 8%.

Radio NBH Utilization %: It is the radio capacity utilization (FR) calculated in the NBH time of the date. It varies from 50% - 75% across circles. Recommended value is 70%.Example:

Assumptions:

NBH Traffic

: 40,000 ErlangBBH Traffic

: 51,000 ErlangVLR (Active)

: 1,400,100 subs

Reported Subs

: 1,800,500 subs

Data config %

: 6%

Radio NBH Util %

: 70%

Ratios calculated are:

BBH/NBH Ratio

: 1.275

NBH/VLR (Active)

: 28.57 mEr/sub

VLR (Active)/Mktg Subs

: 0.78

mErl/sub (offered) = 28.57 x 0.78 x 1.275 x 1.08 ----------------------------------------------- = 43.83 mErl/sub

0.7

11.2 Capacity rollout tracking

Monthly tracking of capacity forecasted / budgeted & actual rolled out is to be followed. Attached is the template for the same.

12 Network enhancement features 12.1 Coverage enhancement solutions

With a view to get the maximum coverage out of current sites before a new site is planned, especially in suburban/rural areas, following are some of the main features to be considered for capex savings into budget as per their applicability:

12.1.1 ICE (Intelligent Coverage Enhancement)

This feature helps in maintaining same coverage footprint even when BTS site capacity is enhanced from 2/2/2 upto 4/4/4. Useful for rural areas where coverage shrinks due to 3rd TRX addition.

12.1.2 SRC (Smart Radio Concept)

This uses 2 TRX units in single density mode and provides coverage extension on highways/rural areas by upto 3 Kms depending on terrain. Hence a 4/4/4 site can be configured as a 2/2/2 site with higher coverage levels with a TMA in the uplink. But this solution should be restricted to areas where capacity requirements are less than 2/2/2 for at least 6 months. For capacities more than 2/2/2, this solution is not commercially viable.

12.1.3 Two (2) Port Antenna Combiner By-pass

Description

2 Port regular antennas can be used in combiner by-pass mode to gain 3dB power in the Link Budget. Coverage footprint increased with this implementation. Solution can be used in rural area, towns with single site and up to 2 TRXs per sector.

Implementation

By-pass the combiner of 2 TRXs & provide direct Tx/Rx inputs to Antenna Port

Dependencies

Regular 2 Port antenna required

Advantages

Gain of 3dB in Link Budget

Enhanced coverage footprint for Rural Single site towns

Recommendations

Use of 2 Port Regular Antennas for Sector up to 2 Trx in Combiner Bypass mode.

Use 4 Port Antenna for More than 2 Trx Sector to keep the Trx in Uncombined mode

2 Port Antenna (Combiner Bypass)

12.1.4 Four (4) Port Antenna Combiner By-passDescription

4 Port antennas can be used in combiner by-pass mode to gain 3dB power in the Link Budget. Coverage footprint increased with this implementation. Solution can be used in rural area, sites with 3 and 4 TRXs per sector.

Implmentation

By-pass the combiner of 3-4 TRXs & provide direct Tx/Rx inputs to Antenna Port

Dependencies

4 Port antenna requiredAdvantages

Gain of 3dB in Link Budget

Enhanced Coverage footprint for Rural single Site towns

Savings on pole mount with use of 4 Port Antenna

No loss of coverage moving from uncombined 2/2/2 configuration to Higher configuration of 4/4/4

Recommendations

Use of 4 Port Antenna for sector having more than 2 Trx up to 4 Trx in Combiner Bypass mode

4 Port Antenna (Combiner Bypass)

12.1.5 High Gain Antenna [20dBi, 65]

Description

20dBi, 65 High Gain antennas can be used to increase coverage footprint in rural and Highway/Railway sites. High Gain antennas can provide up to 6dB gain in link budget with combiner by-pass mode.

Implmentation

Implement 20dBi High Gain antenna in either Combine mode or Combiner By-pass Mode

Dependencies

20dBi High Gain Antenna RequiredAdvantages

Up to 6dB Gain in Link Budget

Enhanced coverage footprint for Rural Single site towns

Recommendations

Use of 20dBi High Gain Antenna

with combiner bypass for 2 TRX sector

20dBi High Gain Antenna

12.1.6 TMA

TMA to be used on for sites in suburban/rural areas where BTS downlink power is enhanced using special techniques as discussed in section 7 above. Typically link budget is balanced within 5 dB with default configuration deployment. Dual Duplexed TMA units only to be used.

12.1.7 TMB

TMB provides Gain I both directions (uplink & downlink) and hence is to be used only when there is a requirement to increase coverage footprint while maintaining the link budget balance. It is mostly used in in- building solutions where micro BTS is used for coverage.

It is not recommended for macrosites in view of higher cost involved.

12.1.8 Tower Top BTSIn a macrosite link budget, typically a 3dB feeder loss is considered. However in locations where coverage enhancement is critical like in highway locations, BTS equipment can be installed on top of tower to avoid 3 dB feeder loss. This will result in coverage enhancement and also capex saving on account of feeder. However due to higher tower loading involved, such solutions are recommended to use micro BTS solutions like Metrosite & mini-Ultra models.

12.1.9 Repeaters

GSM Repeater systems are typically used in following

To extend coverage beyond BTS footprint

To improve in-building coverage in urban areas.

To create a dominant channel in an area to improve C/I and hence quality

Repeater types (based on power)

Low power repeaters (upto + 16 dBm output)

Medium power repeaters ( upto + 27 dBm output)

High power repeaters ( more than +27 dBm output)

Repeater types (based on application)

Pico repeaters (for home applications)

Multi band repeaters

Frequency shift repeaters

Channel selective repeaters (do not support freq hopping)

Band selective repeaters

OFC fed repeaters (with separate central & remote heads)

Recommended vendors for various repeater models are as per Hutch recommendations. However Frequency shift repeaters are not recommended in view of disadvantaged cost model w.r.t micro BTS solutions.

12.2 Abis Compression solution

Detailed field evaluation of Abis compression solutions offered by various vendors is carried out. Salient features of the solution are:

Maximum 2:1 compression is obtained (in view of Abis links already compressed by 4:1)

Upto 100 Erlangs traffic per compressed link possible. 24 TRXs or more can be mapped onto 1 E1, depending on total carried traffic.

Data calls supported (GPRS & EDGE)

AMR & HR supported.

No perceivable MOS deterioration observed at peak traffic on the compressed link.

Solution is BSS vendor specific, in view of proprietary Abis configuration. Testing completed on Nokia and Ericsson Abis only.

NMS available

Considering the current TRAI guidelines on leased bandwidth charges and also prevailing discounts offered by various NLD providers, use of this solution is recommended for following cases:

Where additional E1 capacity for either new sites or existing capacity enhancements is not available from any BW vendor.

Where minimum of 2E1 links are required / used currently.

Where chargeable distance is at least 100 Kms.

However this solution is not to be used for links with 6 or more E1s currently used or required within 1 year in view of lower bandwidth charges for higher E1 links.

12.3 VSAT Abis connectivity

This solution for Abis connectivity is recommended only if all of the following conditions are met:

BTS configuration shall not exceed 4/4/4 (including all chained sites to parent VSAT site)

At least two or more microwave repeater stations needed to connect BTS from the nearest Hutch site.

No leased bandwidth available from any vendor at least for next 1 year.

Data traffic not required. (VSAT cannot support data calls in current software version). However, SMS is supported.

Space for installation of 2.4 Mts diameter VSAT antenna with clear sky visibility at site.

Recommendation:

Based on the current cost structure of VSAT system for GSM Abis, at least 15 VSAT remote sites per central Hub in a circle network are required to make this system cost effective, both in terms of Capex & Opex.

In current regulatory environment for VSAT approvals, a lead time of at least 6 months to be considered for commercial launch from the date of PO.

12.4 Mobile BTS station

Following pros and cons of this system are to be considered:

Pros:

Provide short term coverage and capacity in hot spots like convention centers, exhibition grounds and sports complexes where a permanent site is not required / possible due to various reasons.

Provide short term capacity & coverage in areas where new site implementations are delayed due to various reasons.

To study subscriber response in a suburban/rural area before committing a new BTS site. >

Can be used as testing Lab for new BTS products or features before implementing network wide.

Cons:

Need sufficient parking space to install the system and also require advance coordination with local agencies.

They are prone to accidents if not properly handled and installed.

Require LOS to nearest cell site. Difficult in CBD areas with high rise buildings.

GSM Frequency plan changes required at short notice in neighboring sites to bring up the mobile BTS.

Require to arrange a vehicle to pull the trolley to the parking slot.

Sufficient planning required on route taken to move the trolley. Narrow and temporary roads with low height over bridges cannot be used.

SACFA approval for temporary siting and height clearance required.

Site may add localized microwave interference due to short term addition of new hop into the network.

Need sufficient training for BSS team to install the tower

May not be used throughout the year, leading to a non-performing asset in the network.

Recommendation:

To take a decision based on above considerations.

13 Energy Saving Guidelines

13.1 ULTRA EDGE BTS

13.1.1 Shiner Frisco Trx

Description

Re arrange Shiner TRX as BCCH and Frisco TRX as non BCCH e.g. TRX 1,5,9 in 4/4/4 Ultra can be Shiners and rest all can be Frisco. These TRX can be configured as "preferred BCCH TRX" in the BSC. BCCH TRX always radiates at full power. The reduction in power consumption comes from Frisco TRX in which the PA is shut down in idle time

Implementation Simple implementation with re-arranging the Shiner & Frisco Trxs. Identification of Shiner & Frisco TRX Log into the BTS Manager

Pickup HW version data for the BTS as Shown in Text A

Seek the Version numbers of the Trx in Use

FRISCO TRX : Version 209 and above

SHINER TRX: Version up to 208

Dependencies

Shiner/Frisco TRXs required

Advantages

Frisco consumes less power than shiner TRXs

Utilizes Idle time PA shutdown in Frisco Trx

Lowers power consumption of the BTS

Savings of up to 30 w per TrxRecommendation

Rearrange Shiner TRX as BCCH & Frisco in TCH in Ultra Site to lower the power consumption of BTS.

13.1.2 LTCD (Low Traffic Controlled Disconnect)

Description

In large installations where more than 1 cabinet is used to form a cell it is often the case that at times of low traffic a single cabinet offers sufficient capacity. The 2nd cabinet is hence surplus to requirements and can be turned off in order to save power from the mains supply. A solution has been devised which utilizes a modified LVLD switch which is placed in the 48V supply line to the BTS cabinet and the Calendar SW tool in the BSC to switch of a 2nd auxiliary or slave cabinet under the control of the Master cabinet.

Dimension (HxWxD in mm)300x230x110 mm

Weight (Kgs)2 Kgs

Volume (Ltr)7.6 Ltr

LTCD Hardware Specification

Implementation

LTCD box to be installed between power system and the two Ultra Site cabinets

Dependencies

The solution can only be used when more than 1 cabinet is used, the cabinet which is turned off to save power will not usable and should not carry any traffic which cannot be turned off. It is expected that all BCCHs and traffic while moved onto the Master cabinet before the 2nd cabinet is turned off.

It is important to note that the cabinet which has been turned off will have none of its environmental control systems running during the period it has no power applied to it. In outdoor applications particularly in areas of high humidity there is a risk that the inside of the cabinet may go past the dew point as it cools and water droplets may form inside the cabinet. If this is likely to be the case then the extreme conditions gasket kit (469996A - D-CONNECTOR ENHANCEMENT KIT) should be added to the cabinet.

The BSC command calendar executes events based on the system time. If the BTS is not operational when the calendar is due to either turn on or turn off the 2nd cabinet then the event will not occur until 24 hours later. It is important that if the master cabinet is being reset or is off line when the event is due (particularly the turn on command) that the command is manually activated by the engineer who has been working on the master cabinet.

Advantages

Power savings based on the expansion cabinet Trx Loading

For a 8/8/8 site with LTCD, 50% savings in power consumption during Traffic Lean Hrs

Recommendation

Identify Low Traffic Periods at Night

Implement an External Switch connecting Expansion Cabinet to Main Cabinet

Run a Script for the BTS to switch off in the Lean Traffic Window set in the Script.

Ensure The Cabinet switches on at the end of the Time Window specified

13.1.3 Hybrid Solution (Ultra 2/2/2 to Flexi 4/4/4)

Description

Expand existing 2/2/2 Ultra BTS to 4/4/4 with 2/2/2 Flexi in the lower half of the same cabinet. The Flexi dTRXs can be shut down in low traffic hours.

Implementation

Trained BTS engineer needed on site insert the expansion kit and rearrange the TRXs

Dependencies

The configuration needs to be standardized and tested in all future releases

Complex Cabling & O&M activity Hardware Kit Required to install flexi BTS

Advantages

120 w Savings in power consumption with respect to 4/4/4 Ultra Site consumption

Ease of Implementation within the same cabinet

Recommendation

Use of up to 2/2/2 Flexi for Expansion of 2/2/2 Ultra Site

Flexi Expansion Module placement within unused space in the Ultra Site Itself

Most Suitable for Expansion from 2/2/2 to up to 4/4/4 saving both Space and power.

13.1.4 Co-Siting Solution (Ultra 4/4/4 to Flexi 6/6/6)

Description

Flexi EDGE can serve as an extension for Ultra Site cabinet. TRXs from both the BCFs can be combined in same sector or the TRXs can be re arranged so that all Flexi EDGE TRXs are in the same sector.

Implementation

It would be just like Multi BCF with 2 Ultra Site cabinets.

Dependencies

Enables modernization with the latest product. All latest Flexi EDGE features can be used in the Flexi BCF.

Advantages

120W Savings in power consumption with respect to 4/4/4 Ultra Site

Use of single Synchronization cable between cabinets

Recommendation

Use of up to 2/2/2 Flexi for Expansion of 4/4/4 Ultra Site

Flexi Expansion Module(2/2/2) co-sited with Ultra site(4/4/4)

Most Suitable for Expansion from 4/4/4 to up to 6/6/6 saving power.

.

13.2 FLEXI EDGE BTS

1. Script Based TRX Shutdown

Description

Flexi EDGE dTRU cab be switched off during low traffic period. The Time window should be identified for low traffic hours and script needs to be activated in OSS to shutdown the dTRU. Approx 295 to 335 W power saving observed per dTRU shutdown.

Implementation

Time Window needs to identify based on traffic pattern and Script should be activated in OSS.

Dependencies

Script based TRX Shutdown and Antenna Hopping feature can work together after following modification only.

Configuration at BSC

TRX 1 is the BCCH TRX

BTS 2 is locked prior to locking DTRX 2 (TRX 3 and 4) using a script *due of antenna hopping in use*

TRX 1 and TRX 2 continue to be working on separate antennas with antenna hopping see next slide

Reconfiguration for TX cabling on site

TX 1 and TX 3 on Antenna 1

TX 2 and TX 4 on antenna 2

DTRX 2 (TRX 3 and 4) to be powered off during low traffic hours

DTRX 1 will supply power to DDU

TRX 1 will be on Antenna 1 and TRX 2 will be on antenna 2 -> antenna hopping can still be used

Advantages

Approx 10% Savings in power consumption with script based Trx shutdown.Recommendation

Use of Script to force calls onto BCCH Trx from TCH Trx

On TCH getting freed, switches off P.A of TCH Trx

Identify Lean traffic period for Flexi BTS

Activate script for the BTS in BSS with time window set.

Switch off & switch on of dTRU based on timings set in Time window.14 Network Optimisation

The network optimization process consists of the network performance evaluation and the subsequent actions to improve them. The main tools used for network optimization belong to three classes:

planning tools

radio measurements tools (drive test and propagation)

OMC data analysis 14.1 Key Performance Indicators

XE "key performance indicators, KPI" To evaluate the performance of a network it is necessary to define some reference values, the so-called KPIs (Key Performance Indicators). KPIs are calculated after a post processing of NMS data or drive test measurement data. Usually one short-term target and one long-term target are defined for each KPI.

Every network produces periodically a report with the KPIs status to check the network evolution and which targets are achieved and which not, this leads to the definition of new action points to improve the poorest indicators. KPIs calculated with NMS data, represent the network performance from the system side. KPIs from drive test figure out the performance on the subscribers side. Usually network quality is evaluated according to some predefined KPIs figures like drop call rate and average downlink quality.

The most reliable KPIs to evaluate the network performance with NMS are:

Drop call rate [%], which is the percentage of call ended without a subscriber request

SDCCH and TCH congestion time, which is the sum of the partial time when all the resources of a cell are busy in the reference period (1 hour usually).

Call set-up success rate, which is the percentage of call attempts that leads to a TCH seizure.

Handover failure and/or success rate [%], which is the percentage of handover failure or handover success in the reference period.

Average quality DL and UL, which is the mean value of all the quality samples uplink and downlink.

Blocking percentage [%], which is the percentage of call attempts failure due to lack of capacity resource

All these figures can be collected on different network element basis (TRX, Cell, BTS, BSC, PLMN).

Drive Test Measurements Drive test measurements and their analysis is a powerful means to evaluate network performance from the subscriber point of view. It is possible to collect some KPIs information like DL quality, call success rate, handover success rate, DL signal level from the drive test results, but the results are not statistically as reliable as NMS information. The real adding value of drive test measurement compared to NMS data analysis is the following information:

find out the geographical position of problems like bad DL quality to look for a possible interference source in the area

compare the performance of different networks

display the signal level on the digital maps to individuate areas with lack of coverage and eventually improve the propagation model

verify the neighbour list parameter plan.

There are no strict processes for optimization because the activity is driven by the network evolution.

Optimization Targets

In a new town launch area, the primary target is normally the coverage. In this phase, usually there is a massive use of drive test measurement both to check the signal and the performance of the network

In a capacity driven network the primary targets are quality indicators like drop call rate, average quality, handover failures. In this phase, it is very important use the information from NMS because they give a general view of the network performance. Drive test measurements are still used but not in a massive way, they are performed in areas where new sites are on air, or where interference and similar problems are pointed out by NMS data analysis.The targets value, measurement time and measurement period for our network is shown below:KPIMeasurement TimeMeasurement PeriodTarget

Top CitiesRest of NWTop CitiesRest of NW

Switch KPI

Successful Call Rate (NBH)Network Busy HourDaily>=99%

Paging Success Rate per MSC (NBH)Network Busy HourDaily>=92%

Network Availability (Switch)24 HoursDaily>=99.99%

Network Availability (IN)24 HoursDaily>=99.99%

SS7 Signaling Load (NBH)Network Busy HourDaily=98.8%

TCH Completion Rate (NBH)Network Busy HourDaily>=98.5%

Handover Success Rate (NBH)Network Busy HourDaily>=97%

SDCCH Assignment Success (NBH)Network Busy HourDaily>=99.5%

TCH Assignment Success (NBH)Network Busy HourDaily>=98%

RX Quality DL (0-5) (NBH)Network Busy HourDaily>=97%

Radio Network Availability24 HoursDaily>=99.95%>=99.5%

Cell Level KPI (% of cells meeting KPI)

SDCCH Completion Rate (BBH) >98%SDCCH Completion Rate (BBH) >98%Bouncing Busy hourDaily>=95%>=90%

TCH Completion Rate (BBH) >=98%TCH Completion Rate (BBH) >=97.5%Bouncing Busy hourDaily>=95%>=90%

Handover Success Rate (BBH) >= 95%Handover Success Rate (BBH) >= 95%Bouncing Busy hourDaily>=95%>=90%

SDCCH Assignment Success (BBH) >=99%SDCCH Assignment Success (BBH) >=99%Bouncing Busy hourDaily>=95%>=90%

TCH Assignment Success (BBH) >= 97%TCH Assignment Success (BBH) >= 97%Bouncing Busy hourDaily>=95%>=90%

RX Quality DL (0-5) (BBH) >=96%RX Quality DL (0-5) (BBH) >=94%Bouncing Busy hourDaily>=95%>=90%

Random Access Success Rate (BBH) >=95%Random Access Success Rate (BBH) >=95%Bouncing Busy hourDaily>=95%>=90%

EDHE / GPRS KPI

EDGE DL Average Throughput per TBF (DBH)Data Busy HourDaily>=90 Kbps>=45 Kbps

GPRS DL Average Throughput per TBF (DBH)Data Busy HourDaily>=27 Kbps

TBF Success Rate (DBH)Data Busy HourDaily>=93%

DL Multislot Assignment Success (DBH)Data Busy HourDaily>=95%

14.2 Performance Evaluation Network Quality test for new coverage site / new town launch

Drive test is conducted before launching the network commercially for new towns. At this stage, the default parameter set should be used for all sites. In addition to that, the network planner gives the neighbor definitions for the site. The frequencies, BSIC, LACs and BCC are also defined.

The purpose of the measurements is to verify that the basic parameters have been given correctly and everything is functioning properly. This means that the frequencies and handovers to all neighbors need to be checked. For this, radial measurement routes into the neighbor cell areas have to be defined. In addition to that the coverage range of the cell should be checked and compared with the predicted one.

Performance / Drive TestPerformance tests represent the subscriber's view of the network. These measurements are conducted in a live network on regular basis. During the measurements, calls are generated e.g. every 2 minutes. The number of calls should be high enough to be statistically reliable. A random route should be defined once and used repeatedly for the measurements. This enables the comparison of the measurement data and hence the development of the network can be traced. The handover success rate, call set-up success rate and call completion success rate can be obtained as a result from these measurements. This information is secondary to the OMC information for the KPIs. However, performance measurements give geographical information about the problem areas and hence give additional information to the OMC data.

Optimization Process

An optimization process should not start without a previous Network Audit, in order to state the starting point, that is, how is performing now the network that must be optimized.

The Network Optimization itself could be divided in many ways, depending on the criteria used. One extended criteria separates three main tasks: these are the Parameters and Configurations Consistency Checks, the Performance Monitoring and Reporting and the Performance Analysis and Troubleshooting. In a first phase, this must be also the order or the three steps, but after a first iteration, all of them must run in parallel and in a recurrent way.

As the output result of each round, the solutions found for the identified problems and the improvements suggested must be put in form of Change Request for its implementation in the network.

Parameters & Configurations Checks

The consistency of the network must be checked initially, before any monitoring or analysis, and periodically during the whole duration of the project, so that it matches the planned hardware configuration and parameter set. The checking list follows in the paragraphs below. Obviously, some points have no sense in a project other than a replacement; it is the case of the first one.

Hardware configuration vs plan:

Sector configuration: number of TRXs and output power. The OMC engineer should check this

Antenna configuration: azimuth and tilt. To check by drive tests.

Software configuration vs. plan, and consistency of values:

Frequency plan. To check by drive tests and by consistency checks running in Network Doctor

Adjacency plan. To check in the same way.

Parameter set. To check in the same way.

Alarm status: check that there are no critical and performance-affecting alarms in any network element. The OMC engineer should check this using Network Doctor (menu 1 Fault Management).

Parameter correctness, not in relation to the plan, but according to the different strategies, using for example Network Doctor

Handover control and adjacencies strategy.

Power control strategy.

Dimensioning strategy (regarding signaling or GPRS capacity).

Active features correct implementation.

Traffic management strategy (between different layers, bands or cell types).

Performance Monitoring

Statistics monitoring, using any of the reporting tools mentioned before:

Collecting the selected target KPIs at region level, in order to identify the generic problems, and to follow up the project objectives and for reporting purposes.

Making worst cells lists, in order to detect the ones to focus the optimization in.

Collecting a wider range of performance reports and Performance Indicators at cell level, for troubleshooting purposes.

Performance Analysis & Troubleshooting

Searching for specific problems and for ways to fix them is a continuous must, both at area level and at specific cell level. The other permanent issue is trying to find ways to improve crucial aspects of the network performance, namely the overall Drop Call Rate or Blocking Rate, by means of, for example, activating some feature or optimizing some parameter or dimensioning rule. A list of mandatory steps follows below:

Finding generic area problems, by means of statistical analysis. For example:

Wrong setting in handover thresholds.

Feature not working due to wrong parameter set.

Analysis of worst cells in the most critical indicators: using the Network Doctor reports can identify them.

Dropped Call Rate.

Handover Failure Rate.

TCH/SDCCH Blocking Rate.

Identifying coverage problems, meaning both areas with bad coverage and cells covering less or more than wanted: to check from drive tests.

Finding interference and bad quality: to check from drive tests for geographical approach and from Network Doctor reports for cell specific approach.

Detecting adjacency problems: to check from detailed analysis of drive tests and running Consistency Checks.

Missing neighbors.

Unnecessary or unwanted neighbors.

Incorrectly defined adjacencies.

Finding hardware problems: the effects can be detected from statistics, and some from drive test analysis. Further checking on-site by the implementation engineers is necessary.

Crossed sectors.

Mixed antenna lines.

Faulty units (TRXs, BBUs, etc).

Imbalance problems (e.g., due to ROE in cables or jumpers).

The last step of the performance analysis, and only in case it is included in the scope of the project, is the traffic analysis and balance. The objective is to avoid blocking situations and to get a homogeneous distribution of the traffic among cells, or a traffic distribution according to the pre-defined traffic strategy between layers or/and between frequency bands.

Analysis of worst cells: TCH/SDCCH Congestion Time.

Cells with less traffic.

Detection of strong imbalances between sectors of same site and between neighbor cells.

Unsatisfactory behavior of the different strategies of traffic distribution:

Macro layer micro layer umbrella layer.

Overlay layer underlay layer (if IUO is used).

GSM band DCS band.

Slow moving / fast moving MSs distribution.

Optimization Process Outputs

The whole optimization process must produce continuous and/or periodic results, with a double objective: a number of Change Requests, for operational purposes, and a periodic Performance Report, for follow-up purposes.

Change Requests

Right after producing a solution for a found problem a Performance engineer must produce a Change Request for every change he wants to introduce in the network in order to fix the mentioned problem. The possible changes requested can be:

Software changes:

Changing a frequency.

Changing a parameter.

Adding/deleting/correcting an adjacency definition.

Activating/deactivating a feature.

Hardware changes:

Modifying an antenna direction or tilt.

Checking and fixing a detected hardware problem.

CRF Format

The full process from the CR form is produced until the changed is implemented must be perfectly clear, as mentioned before. An example of procedure is shown in the figure below.

After making any major changes the network elements are to be kept under observation for some time for any deteriorate in the network KPI.

Performance Reports

Performance Engineer has to produce a periodic Performance Report, in addition to the final Performance Report. The periodic report, focused in the follow up and the work in progress, could be weekly and should include most of the following items:

Resume of the main KPIs, at circle Network level, for the reported period and evolution from the beginning of the project. List of worst cells for few critical KPIs, usually Drop Ratios and Block Ratios.

Graphs from the Drive Tests done (RxLev, RxQual, events), if agreed.

Resume of status of most critical active alarms.

Detected problems during the period.

Solutions: troubleshooting made.

The Final Performance Report will be more focused in summarizing the achievements of the established target KPI values. It could also include a resume of the main troubleshooting works, grouped by type.

ND reports In the Nokia OSS ND reports can be generated to get the specific information about network health. It provides ready-made textual reports for analyzing the performance of the network. Reports are based on the collected from different areas, such as configuration, performance and fault management with a special focus on the needs of network planning and O&M. Reports support the network operations scope from BSS level down to cell level The list of major ND reports and its description is given Below

ReportDescription

Report 020 Report 020: Alarm statistics 221

Report 023 Report 023: Alarm-specific statistics for each BTS 222

Report 024 Report 024: Active BCCH missing alarms 223

Report 025 Report 025: BTS alarm sum time by cells 224

Report 027 Report 027: BTS outage breakdown over 10 days 159

Report 030 Report 030: BSC alarm breakdown 158

Report 034 Report 034: Alarm types and counts 218

Report 035 Report 035: Alarm types and counts for BSC 219

Report 036 Report 036: Number of alarms per object 221

Report 041 Report 041: All base station sites per maintenance region 225

Report 042 Report 042: All radio network sorted out by BSC, BCF, BTS 70

Report 043 Report 043: All cells with LAC and CI 226

Report 044 Report 044: Find BS sites having the given character string in the name 227

Report 045 Report 045: Find cells having the given CI and LAC 227

Report 046 Report 046: Find cells having an adjacent cell with the given CI and LAC 227

Report 047 Report 047: Find cells having the given frequency 215

Report 050 Report 050: Find locked BCFs, BTSs, TRXs and channels 103

Report 051 Report 051: Find cells having GPRS enabled TRXs 266

Report 053 Report 053: AMR parameters 288

Report 054 Report 054: Segment configuration 210

Report 055 Report 055: EGPRS parameters 270

Report 060 Report 060: Adjacency discrepancies 76

Report 061 Report 061: Non-symmetrical adjacencies 78

Report 062 Report 062: Frequency check of adjacent cells 78

Report 063 Report 063: BTS audit 93

Report 065 Report 065: Adjacencies to non-existing or foreign cells 74

Report 066 Report 066: Non-unique CI and LAC 82

Report 067 Report 067: Handover synchronization 80

Report 068 Report 068: BTS parameter survey 85

Report 069 Report 069: Adjacent cell double frequencies 81

Report 070 Report 070: BTSs with maximum number of adjacencies 94

Report 071 Report 071: Cells with minimum number of adjacencies 94

Report 072 Report 072: Defined, undefined and used adjacencies of a cell 98

Report 073 Report 073: Undefined adjacent cells 99

Report 074 Report 074: Adjacencies of cells 94

Report 075 Report 075: BTSs with maximum number of adjacencies between LAs 100

Report 076 Report 076: Adjacent cells having the same NCC, BCC and BCCH frequency 82

Report 077 Report 077: BSC parameter survey 91

Report 078 Report 078: BTS state conflict between BSC and MSC 104

ReportDescription

Report 080 Report 080: Number of named parameter sets 229

Report 081 Report 081: Named sets used 230

Report 082 Report 082: Allocation of a named set 231

Report 089 Report 089: BSC option statistics 207

Report 090 Report 090: Network configuration summary 68

Report 090 Report 090: Network configuration summary 205

Report 091 Report 091: Maintenance regions 207

Report 092 Report 092: BSCs 208

Report 093 Report 093: MSCs 208

Report 094 Report 094: HLRs 208

Report 095 Report 095: Base station sites of a maintenance region 209

Report 096 Report 096: Location areas 209

Report 097 Report 097: PLMNs 210

Report 099 Report 099: BCF software and hardware type statistics 212

Report 103 Report 103: Routing areas 266

Report 110 Report 110: Occurrence of frequencies 213

Report 111 Report 111: Frequency plan 101

Report 121 Report 121: First and last measurement record times for each BSC 56

Report 122 Report 122: Records for a measurement type, over BTS area 62

Report 124 Report 124: TCH and SDCCH observation records 63

Report 126 Report 126: Records for a measurement type, over BSC 55

Report 127 Report 127: Last BSS measurement record times 54

Report 130 Report 130: Cells having SDCCH congestion 133

Report 131 Report 131: Unavailability classification per BSC 177

Report 132 Report 132: Cells having SMS establishment failures 327

Report 134 Report 134: Cells having RACH rejections 326

Report 135 Report 135: Cells having TCH congestion 136

Report 138 Report 138: Cells having high TCH raw blocking 138

Report 139 Report 139: Cells having unavailable radio time slots 179

Report 150 Report 150: Cells having high HO failure ratio 122

Report 151 Report 151: Common BCCH, Multi-BCF HO 313

Report 153 Report 153: Adjacencies having high HO failure ratio 123

Report 154 Report 154: HO attempt cause distribution by cells 318

Report 155 Report 155: TRHO handovers (AMH) 124

Report 155 Report 155: TRHO handovers 307

Report 156 Report 156: DADLB handovers 125

Report 157 Report 157: Cells having high HO attempts/call ratio 326

Report 158 Report 158:Intra BSS HO observation statistics 309

Report 159 Report 159: WCDMA adjacencies having high HO failure ratio 310

Report 160 Report 160: TCH drop call statistics by days across area 111

Report 162 Report 162: TCH drop call statistics per day in each BSC 112

Report 163 Report 163: Cells having high TCH drop call ratio 114

Report 164 Report 164: Transcoder failures 324

ReportDescription

Report 166 Report 166: SDCCH drop ratio per cell 108

Report 167 Report 167: Cells having high drop call count in handovers 327

Report 180 Report 180: TCH traffic ( Erlang) per hour for each BSC or MR 141

Report 181 Report 181: Daily TCH traffic profile for a BTS 147

Report 182 Report 182: Busy hour traffic for all cells 139

Report 183 Report 183: Low traffic cell check-up 324

Report 184 Report 184: BSC unit load for each BSC 148

Report 185 Report 185: Cells having maximum TCH traffic 144

Report 186 Report 186: Cells having maximum paging traffic 149

Report 187 Report 187: Cell location updates 149

Report 188 Report 188: Cells having peak RACH load 150

Report 189 Report 189: Cells sorted out by SDCCH or TCH holding time 150

Report 190 Report 190: Cells having UL interference, 24-hour/10-day breakdowns 187

Report 191 Report 191: Cells having bad link balance 302

Report 196 Report 196: UL and DL quality and UL interference per TRX, 24-hour/10- day breakdowns 295

Report 197 Report 197: UL and DL quality per TRX 296

Report 198 Report 198: Cells by dominant link balance range 305

Report 199 Report 199: Link balance of an area 301

Report 200 Report 200: Daily sums of traffic in report 200, Performance statistics (benchmark) 141

Report 202 Report 202: Cells having most delete indications and PImm. Ass.NACK 151

Report 203 Report 203: Location update success ratio per BSC 129

Report 205 Report 205: BTS GSM KPI/PI table, dynamic object and time aggregation 340

Report 206 Report 206: TRX level GSM KPI/PI table, dynamic time aggregation 341

Report 208 Report 208: Link balance per cell 304

Report 213 Report 213: Performance statistics 268

Report 215 Report 215: Availability per BSC unit 181

Report 217 Report 217: SDCCH, TCH and BSC out HO observation statistics 116

Report 220 Report 220: Clear code statistics 322

Report 221 Report 221: Base station site check 345

Report 222 Report 222: Call distribution per LA 142

Report 225 Report 225: Drop call trace 118

Report 226 Report 226: (E)GPRS KPIs 245

Report 228 Report 228: Cells by multislot requests and allocations 250

Report 229 Report 229: GPRS KPIs 241

Report 231 Report 231: Cells by dominant distance range 314

Report 232 Report 232: Distance range distribution per cell 315

Report 233 Report 233: Cells by M 306

Report 235 Report 235: GPRS counters 262

Report 236 Report 236: Cells having max. HTCH traffic 233

ReportDescription

Report 237 Report 237: UL PS traffic 246

Report 238 Report 238: DL PS Traffic 247

Report 239 Report 239: Territory upgrade, downgrade 248

Report 240 Report 240: Frame relay, detailed 254

Report 241 Report 241: HSCSD counters 330

Report 242 Report 242: HSCSD KPIS 331

Report 243 Report 243: Frame relay, short 256

Report 244 Report 244: Distribution of call samples by codecs and quality classes, S10 (BER) 278

Report 245 Report 245: Distribution of call samples by codecs and quality classes, S10 (FER) 281

Report 246 Report 246: AMR call time and quality, dynamic time and object aggregation 282

Report 247 Report 247: Transcoder failure ratio 283

Report 248 Report 248: Codec set modification failure ratio 284

Report 249 Report 249: AMR counters summary 287

Report 250 Report 250: Cells by call success ratio 155

Report 251 Report 251: Call success profiles of a cell 156

Report 254 Report 254: TBF PI 252

Report 255 Report 255: PBCCH availability 272

Report 257 Report 257: Sleeping GPRS BTSs 276

Report 260 Report 260: Position Based Services (PBS) 290

Report 270 Report 270: Quality of service 273

Report 275 Report 275: EGPRS RLC statistics 267

Report 278 Report 278: WPS PI 333

Report 280 Report 280: Dynamic Abis 269

Report 400 Report 400: IUO counters of a cell 200

Report 401 Report 401: Cells by average traffic absorption to super TRXs 191

Report 402 Report 402: Cells by busy hour traffic absorption to super TRXs 192

Report 403 Report 403: KPI statistics for IUO cells 201

Report 404 Report 404: IUO measurement data per BTS 201

Report 405 Report 405: Adjacent cells with the same or adjacent frequency, IUO super TRX excluded 202

Report 407 Report 407: C/I statistics 202

Report 512 Report 512: Log statistics 39

Report 513 Report 513: Network Doctor use statistics 40

Report 515 Report 515: DMR profile 164

Report 516 Report 516: DN2 profile 164

Report 517 Report 517: TRU profile 165

Report 518 Report 518: Transmission statistics 163

Report 522 Report 522: BSC ET profile 171

Report 523 Report 523: BSC TCSM profile 174

Report 525 Report 525: TRE profile 175

Report 526 Report 526: TRE-SEL profile 175

Report 700 Report 700: Cell related SGSN counters 264

Report 800 Report 800: Quality survey 292

14.3 Interference ReductionInterference is the sum of all signal contributions that are neither noise nor the wanted signal.

XE "carrier-to-interference ratio, C/I" Carrier-to-Interference Concept: Signal quality is largely determined by the ratio of carrier-to-interference (C/I). GSM specifies a minimum C/I of 9 dB to ensure nominal bit error rates under static propagation conditions.

Figure 1.Carrier to interference

Interference causes degradation of signal quality. This introduces bit errors in the received signal. Bit errors are partly recoverable by means of channel coding and error correction mechanisms. There are also irreducible bit errors caused by phase distortions of the radio signal (random FM noise).

The interference situation is as opposed to field strength not reciprocal in uplink and downlink direction. Mobile station and base station are exposed to very different interference situations. The ratio of Carrier-to-Interference (C/I) is a key figure for assessing the quality of a radio signal.

Signal quality classification in GSM is based on detected bit error rates before all channel coding and error correction takes place. GSM-specified parameter RXQUAL ranges from 0 (excellent) to 7 (bad) in logarithmic steps.

Figure 2.GSM quality classes

Sources of Interference

The main source of interference is the re-use of own frequencies. Other contributions to interference come from multipath components of the very same signal, i.e. long delayed echoes that are outside the equaliser window of 16 microseconds. External interference is caused by spurious emissions from other frequency bands.

A network will practically always be limited in its performance by interference rather than by coverage. Interference is unavoidable due to re-use of frequencies. However, the radio planners goal will always be to push the interference limits as far out as possible.

Co-Channel Interference

Co-channel interference comes from the re-use of own (limited) frequency resources. It is therefore unavoidable in a network and the major contribution to total interference. Dense re-use of frequencies provides high capacity and also high interference levels. Scarce frequency re-use provides excellent interference-free networks but with very low capacity. So, once again, it is the planners task to find the compromise.

The optimum layout of cell patterns, providing the best compromise between introduced interference and achieved capacity, has been studied in depth in literature. For illustration reasons often regular hexagonal cell patterns are used as a simplified case. Applicability of a model that greatly simplified is, however, doubtful.

Figure 3.Co-channel interference

where the carrier is R-( and the interferers 6*(D-( ).

There is a trade-off between C/I, frequency efficiency and network capacity. While ana

Radio Access Network Planning Guidelines v2

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