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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
c
Primary Optimization
c
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