MobileComm Technologies India Pvt. Ltd.

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Drive Test Process

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Copyright 2010 MobileComm Technologies India Pvt. Ltd. All rights reserved MobileComm is committed to providing our customers with quality instructor ledTelecommunications Training.This documentation is protected by copyright. No part of the contents of thisdocumentation may be reproduced in any form, or by any means, without the prior written consent of MobileComm Technologies .Document Number: RK/CT/3/2010This manual prepared by: MobileComm Technologies

MobileComm Technologies(India)Pvt. Ltd.424, First Floor, Udyog Vihar Phase -4, Gurgaon-122002 Headquarter:MobileComm Professionals Inc.1255 West 15th Street, Suite 440Plano, TX, 75075Tel: (972) 633-5100Fax: (972) 633-5106www.mcpsinc.com

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UMTS Call Flow

3

4

Soft/SofterHandover/Clear

Call to a MS

Paging

Call from a MS

RRC Connection

RABAssignment

Supervision

on PICH/SCCPCH

on FACH/ SCCPCH Predefined Signaling

RAB Selected

on FACH/SCCPCH

on DPDCH

Assignment of DPDCH

on RACH

ActivateAlgorithms

Power Ctrl.

Code Ctrl.

Admission Ctrl.

RAB Selection

MEASUREMENTS

•Directed Retry

•Load Sharing

Soft Handover•Inter cell/BSC•Intra cell/BSC•OL/UL•Bad Quality•Urgency•HCS

Inne

r Loo

p/Ou

ter L

oop

Powe

r Con

trol

(RRC Connect. Perform.)

(Random Access)

(RAB Establish. Fail.)

(Traffic Erlangs)

(Call Quality)

(Handover Perf.)

(Dropped Calls)

(Available TCH)

(Paging Perf.)

UMTS Call Flow

Open LoopPower Control

(Throughput)

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5

UMTS Call Flow

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• TEMS Investigation for WCDMA (Software)• TEMS Scanner (Software + HW)• External GPS• User Equipment (UE)• TEMS DeskCat for post processing• MCOM3g/Mapinfo• MS Access/Excel based tools

Tools For Tuning/Optimization & Data Post ProcessingActive measurement needed due to lack of statistics

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WINDOWS USED IN WCDMA DRIVE TEST

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RADIO PARAMETERS WCDMA BAR CHARTS

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CURRENT CHANNEL

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SERVING/ACTIVE + NEIGHBOURS WCDMA

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AMR CODEC USAGE IN WCDMA

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Notes on quantities denoting signal power

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USB2 USB1

Com 1

scanner

Short call Long Call

USB1

CS64

GPS

USB1

PS

Drive Test Equipments for Voice, CS64 & PS call

Drive test tools configuration

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Drive Test Routes

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The basic measurements of scanner are • CPICH_RSCP (received signal code power)• CPICH_Ec/No (received energy per chip divided by the power density

in the band)• RSSI (received signal strength indicator)What can you achieve with scanner?• Crossed feeder issues (DL) • Coverage verification• Interference problems (overshooting cell, pilot pollution)• Missing neighbours

PILOT TUNING

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COVERAGE VERIFICATION - Primary Common Pilot Channel

Verify P-CPICH detection to minimize coverage holes

• P-CPICH RSCP• P-CPICH Ec/No

Coverage level RSCP [dBm] Ec/N0 [dB]

Sufficient RSCP 100 Ec/N0 14

Poor 115 RSCP <100 16 Ec/N0 < 14

No coverage RSCP < 115 Ec/N0 <16

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• Yellow is good• Blue can

generate problems

• Grey is bad

Best Server Signal Strength (RSCP)

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• Green is good• Blue can

generate problems

• Orange is bad

Pilot Ec/No Measurements

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INTERFERNECE

-100

-90

-80

-70

-60

-50

-40

-30

-25 -20 -15 -10 -5 0 5

Ec/Io [dB]

RSC

P [d

Bm

]

High interference

By correlating low Ec/No with high RSCP, areas with high interference can be detected

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INTERFERENCE (RSCP > -90 dBm AND Ec/No < -9 dB)

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Primary Common Pilot Channel (P-CPICH) – OVERSHOOTING

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OVERSHOOTING Change Proposal: Site-D, Sector-1, Antenna Down-tilt 8 Degrees

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Primary Common Pilot Channel (P-CPICH) – PILOT POLLUTION

• P-CPICH RSCP• P-CPICH Ec/No

High CPICH reception levels from manyCells, (more than MAX_ACTIVE_SET)

sizeserving

cc ASthresholdNE

NEcountPilot )(

00

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PILOT POLLUTION

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PILOT POLLUTION

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PILOT POLLUTIONChange Proposals

Site Name

Sector Number

SC of Pilot

Height of Antenna (meters)

Antenna Tilts

(degree)

Proposed Antenna

Tilts (degree)

A 1 173 38 2 5

A 2 76 38 2 4

D 1 485 47.3 2 8

C 2 24 39.2 3 5

B 3 79 27 2 3

27

0

5

10

15

20

25

30

35

Numbers of Samples

173 76 485 79 24

SC of Pilots

0

5

10

15

20

25

30

35

40

Number of Samples

173 76 79 24

SC of Pilots

PILOT POLLUTION

Initial Drive Test (before tuning)

Verification Drive Test (after tuning)

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UE TUNING

• Voice /Video/PS calls– Long calls– short calls

• Identify problem areas– Blocked calls– Dropped calls– Delay/Throughput

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Short Calls Analysis

Set-up a call and maintain it for a pre-defined time duration(for 15-60 s)

Call set-up failure and drops during short calls can be mainlyused to analysis Accessibility failure due to: • UE Failure• Unsuitable Parameters Setting• Coverage Problem• Interference• Others

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Long Calls Analysis

Drops during long call can be used to identify:• Missing Neighbor Relation• Coverage Problem• UE Problems• Network Characteristics• Best Parameter Setting• Others

Set-up a call and maintain it until it is drop (used for the analysis of Retainability performace)

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KEY PERFORMANCE INDICATORS

Accessability (Call set-up success rate)

Retainability (Dropped calls)

Mobility (Handover success rate)

Integrity (BLER and throughput)

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Case 1: Drop due to missing neighbor

Problem: Detected Nighbor (DN)• UE sends a Measurement Report that contains an event1a means

adding a new RL (cell) to Active Set• If the reported cell is not in the current neighbor cell list and the

reported Ec/No is better than the best serving cell Ec/No in AS by some dBs (set by a RNC parameter)

• If for any reason the new cell can not be added to AS, call will be released

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Case 1: Drop due to missing neighbor

“DN” cell better than the serving cell

DL BLER gets worse

“DN” cell better than the serving cell

DL BLER gets worse

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Case 2: Drop due to Poor Coverage (low RSCP)

Problem: Poor DL coverageWhen UE gets to an area with low RSCP ( < -105 dBm)regardless Ec/No values there is high risk for drop.UE will likely ramp up the transmitted power and reach its max power. The DL BLER will probably increase and SIR target cannot maintain anymore, finally the call drops.

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Case 2: Drop due to DL Poor Coverage

Very bad RSCP

UE max Tx powerandhigh DL BLERVery bad RSCP

UE max Tx powerandhigh DL BLER

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Case 3:PS: Session Error due to Poor DL CoverageUE enters a very low coverage area (RSCP < – 105 dBm).The packet connection is carried on a 64/64 DCH Channel as consequence of the low coverage conditions. The UE will likely ramp up its power to the maximum, goes to Idle Mode and the Application and RLC throughputs go to zero. At this point the RAS application will start the Session Timeout timer, if the throughput is not resumed the Session Error event is triggered with cause “session timeout”.

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PS: Session Error due to Poor DL Coverage

App throughput ~64kbps

Very low RSCP

App throughput ~64kbps

Very low RSCP

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FINAL WORDS

• For network tuning, we need to relay on field measurements which require extensive drive tests

• Finding the best possible configuration for antenna heights, tilts, azimuths and parameter setting for all the present cells/sectors in the network and also for any new sites that might be needed to improve coverage

• Power adjustment can also be used for network tuning but can become complicated and result in poor network performance

• Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antenna

• Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference reduction). Keep neighbour list upto 20.

• Automated tools are needed that could suggest the best possible neighbour relations, antenna heights and tilts by using both the field measurements and the propagation models & simulations

• Skilled people, right methods and advanced tools are needed to perform 3G tuning and optimisation

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Comparison of Mechanical and Electrical Down-tilts

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MOC

MTC

MOC/MTC Call Flow timing

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RRC messages information

Voice and Video are bothConversational Call

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RRC messages information

DL SRB

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RRC messages information

UE in DUAL MODE

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RRC messages information

Voice AMR

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RRC messages information

CS call, 64Kbps,Transparent

Video Call

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RRC messages information

Video CS 64:DL SF 32UL SF 16Voice AMR:DL SF 128UL SF 64

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NEW SLIDES

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WCDMA Coverage – Implications

• High Pilot Signal Strength ¹ Guaranteed Coverage.

• Coverage defined by Ec/I0.

• Ec = RSCP – Received Signal Strength of own Pilot. Constant.

• I0 = Interference from all other users , own cell + other cells.

• Interference increses when traffic increases.

• Cell coverage smaller when traffic increases.

• Cell Breathes.

• Target Ec/I0 = - 16 dB.

• Ec/I0 below –16 dB => No channel estimation, No Coverage.