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GSM AND RF PLANNING AND MEASUREMENT OF RF COVERAGE AREA USING DRIVE TOOL

D.JEEVANKUMAR CH.SAHAS REDDY

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INTRODUCTION

Telecom network GSM Subsystems

ChallengesBandwidth Management

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BANDWIDTH MANAGEMENTFDMA. TDMA. Cellular Technology (Freq Reuse).

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TDMA in FDMAup link 25 Mhzdownlink 25 Mhz

890

915

935

960

890.6C0 C1 C2

Mhz890.2

890.4 FDMA TDMA

200 Khz

C2 8 timeslots/carr

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Cellular technology(frequency reuse)

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Network ArchitectureOSSHLR

PSTN ISDNSS#7

B T S B T S

SS#7

BSC

SS#7

MSC VLRSS#7

Data Networks

B T S

Air interface

MSC VLR

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GSM ARCHITECTUREIt consists of three modules Mobile Station (MS). o Mobile Equipment (ME). o Subscriber Identity Module (SIM). Base Station Subsystem (BSS). o Base Transceiver Station (BTS). o Base Station Controller (BSC). Network Switching Subsystem(NSS). o Mobile Switching Center (MSC). o Home Location Register (HLR). o Visitor Location Register (VLR). o Authentication Center (AUC). o Equipment Identity Register (EIR).

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ARCHITECTURE OF MOBILE STATION (MS)The Mobile Station Is Made Up Of Two Entities: Mobile Equipment (ME) Subscriber Identity Module (SIM)

Portable IMEI Power level Voice and data tranmission 160 character long SMS

Contains IMSI Key Ki,Kc &A3,A5,A8 algorithms Protected by password or PIN

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BASE STATION SUBSYSTEM (BSS)BTSEncodes,encrypts,multip lexes&modulates Frequency hopping Consists transcoder

BSCControls BTS operation Controls power level Timing advance

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Network Switching Subsystem(NSS)Mobile Switching Center (MSC) Call Setup Function Call Routing Billing Information And Collection Mobility Management - Registration - Location Updating MSC Does Gateway Function While Its Customer Roams To Other Network By Using HLR/VLR.

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Network Switching Subsystem(NSS)-2 HLR AND VLR

Home Location Registers (HLR): Permanent Database Database Contains IMSI,MSISDN,PREPAID/POSTPAID,ROA MING RESTRICTIONSVisitor Location Registers (VLR): Temporary Database Which Updates Whenever New Ms Enters Its Area, By HLR Database. Database Contains IMSI,TMSI,MSISDN,MSRN,LOCATION AREA,AUTHENTICATION KEY.

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Network Switching Subsystem(NSS)-3 AUC AND EIR

Authentication Center (AUC) . Protects Against Intruders In Air Interface. Provides Security Using Algorithms. Generally Associated With HLR. Equipment Identity Register (EIR). Made Up Of Three Subclasses: The White List, The Black List And The Gray List. Only One EIR Per PLMN.

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GSM SPECIFICATIONSGSM 900

Mobile To BTS (Uplink): 890-915 MHZ BTS To Mobile(downlink):935-960 MHZ Carrier Separation : 200 KHZ Duplex Distance : 45 MHZ No. Of RF Carriers : 124 Access Method : TDMA/FDMA Modulation Method : GMSK/PCM Modulation Data Rate : 270.833 Kbps

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GSM OPERATIONSpeech Speech

SPEECH CODING

SPEECH DECODING

CHANNEL CODINGINTERLEAVING

Channel DecodingDE-INTERLEAVING

Burst FormattingCIPHERINGMODULATION Radio Interface270.83 Kbps

Burst FormattingDE-CIPHERING

DEMODULATION

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INTERFACES

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LOGICAL CHANNELSSpeech TRAFFIC

Half rate 11.4kbps Full rate 22.8kbps

DataLOGICAL CHANNELS BCH (Broadcast)

2.4 kbps 4.8 kbps 9.6 kbps BCCH (Broadcast Control) FCCH(Frequency correction)

CCH (Common Control) Control (Signaling) DCCH (Dedicated Control)

SCH(Synchronization)PCH(Paging) RACH(Random Access) AGCH(Access Grant) SACCH(Slow-associated) FACCH(Fast-associated) SDCCH(Stand Alone)

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CALL MANAGEMENT

MOBILE TO LAND CALL. LAND TO MOBILE CALL SCENARIO MOBILE TO MOBILE CALL SCENARIO.

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Mobile Land call ScenarioMSChannel Request RACH SDCH Assignment AGCH Service Request SDCCH IMEI Request SDCCH IMEI Response SDCCH Check IMEI

BSS

MSC/VLRREQUEST FOR SERVICE

EIR

EQUIPMENT VALIDATION

IMEI Check Results Call Setup Request( Dialed Digits) SDCCH CALL Proceeding SDCCH

CALL SETUP PHASE WITH MS

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MS

BSS

MSC/VLRAssign Trunk & Radio

PSTN

Assign TCH SDCCH Radio Assignment Complete SDCCH Trunk & Radio Assignment Complete Network Setup Network Alerting

VOICE ESTABLISHMENT PATH

AlertingFACCH Ring TONE

Ring TONE Connect (ANSWER) (HELLO) CALL SETUPLANDLINE

START BILLINGConnect FACCHConnect Acknowledge FACCH

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MS

BSSDisconnect (STOP BILLING) FACCH Release FACCH Release Complete FACCH Clear Complete Clear Release

MSC/VLRN/W Release

PSTN

RELEASE PHASE

FACCH

Clear Complete

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MOBILITY MANAGEMENT

Modes Of Mobile Station

Switch Off Switch On(ideal Mode) Dedicated Mode

N/W Attachment Process Locating a MS. Location Update Process.

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RF PLANNING

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COMPARATIVE ANALYSISThe Planning should include :For an existing operator All problems encountered in the customers network All areas where the customer has no service and a competitor does Recommendations for solving any coverage and quality problems For a new operator

Strengths and weaknesses in the competitors network Problem encountered in the competitors network

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RADIO NETWORK PLANNING PROCESS

Network capacity, quality Pre-planning coverage ,capacity plan Site survey &site selection C/I analysis & frequency plan Parameter planning

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Signal Propagation Effects and ParametersMultipath and reflections Free space loss Interference Building and vehicle penetration Fading of the signal

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RF Network Design Inputs

Available spectrum and frequency usage restriction, if any List of available, existing and/or friendly sites that should be included in the RF design Limitation of the quantity of sites and radios, if any

Quality of Network (C/I values)Related network features (FH, DTX, etc.)

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RF optimization

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RF OPTIMIZATION

Why Optimization ? - Deviations between plan and reality Inaccuracy of radio planning - Statistical variations in the path loss characteristics - Finite terrain database resolution Implementation - Antenna radiation pattern and effective radiated power - Antenna pattern deviation

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What is Optimization ?

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Optimization PhasesInitial OptimizationProper Parameters use Verify Neighbors list Reviewing Frequency Plan

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Primary Optimization

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Verify existing coverage, site design objectives Analysis & Identification of Problem areas/cells from PMS & drive test statistics, customer complaints Prioritization of problems Identify Solution and Implement Retest the problem areas Consistency Check of the OMC database Fine-tuning of parameters

Maintenance Optimization

On going process, weekly optimization Database maintenance and consistency audits

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MECHANICAL DOWNTILTING

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Power ControlSignal Quality Range (in BER)

0 1 2 3 4 5 6 7

BER < 0.2 0.2 < BER < 0.4 0.4 < BER < 0.8 0.8 < BER < 1.6 1.6 < BER < 3.2 3.2 < BER < 6.4 6.4 < BER < 12.8 BER > 12.8

SIGNAL QUALITY LEVELS

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BSS Optimization ParametersPerformance Determinants -Coverage -Interference -Handover Behaviour -Traffic DistributionOptimization Solutions -Enable/Disable GSM features -BSS parameters -Neighbour cell lists -Antenna tilt, height & azimuth -Frequency changes Discontinuous Transmission -Decreases interference level -Saves battery power (uplink) Frequency Hopping -Decrease interference -Rayleigh Fading

Power Control -Saves battery power -Decrease interference level

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DRIVE TEST

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Pre Requirements for Drive TestVisit BTS site & Collect the following info :

1. Height of Antenna2. Antenna Azimuth Orientation 3. Antenna tilt 4. Checking of RF connectorization 5. Verification of serving area by existing Antenna orientations 6. VSWR & TX Power of DRX B. Data from OMC-R :

7. BCCH frequency8. Hopping Frequency 9. MAIO & HSN 10. Neighbour List

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DRIVE TEST1. Tool may be setup for two mobiles One for Continuous call and another for short call (2minutes).

2. In the route map following are to be enabled for Analysis.1. Rx Level 2. RX Quality 3. Survey Markers (like H/O)

4. Cell site Database.3. Conduct the Drive Test covering all sectors by observing the following parameters. 1. Rx Level

2. Rx Quality3. Interference on BCCH & Hopping Frequencies. 4. Handovers & Drop Calls 5. Observe whether the nearest sector is serving or not.

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TRAI Bench Marks for QOS ParametersCall Setup Success Rate > 98%

Drop Call Rate TCH Blocking Rate SDCCH Blocking Rate

< 3% < 2% < 1%

Rx.Quality(0-5)

> 95%

Handover Success Rate > 98% Call Setup Success Rate > 98%

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Cell site antenna High way

Rx level

Rx quality

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Analysis of Drive Test Results

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Analysis of Drive Test Results :Cause 1. Not defining proper neighbor Solution Defining the proper neighbors.

Observation

Handover Failure

2. Improper Neighbors Parameter values 3. Due to TCH congn. 1. Not defining proper neighbors 2. Low Rx level 3. Intereference

Check the neghbour parametersAugmentation of DRIs Defining the proper neighbors. Check the DRX power & connectors Check the BCCH & MAIO frequencies

Reduction of Antenna height, Orientation & TiltCheck the neighbour list & definitions

Call Drop 4. H/O failure

Check the neghbour parameters5. Assignment Failure Ratio Check DRX & Check VSWR & RF cable connectivity

6. Hard Ware Problem

DRX problem

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Thank you

GSM