Drive Test Well Explained

8/8/2019 Drive Test Well Explained

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DrivetestDrivetest


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Tools

Mobile TEMS Pocket W600i

GPS

Compass

Inverter input 12V, Output 220 V ac, 400 W

TEMS Software 7.1.1 Data Collection

TEMS Software 7.1.1 Route Analisys

Map Info


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Work Process

Collect

OMC Parameter

Database

RF NetworkDesign

Cell File (TEMS)And

Dot Tab Site (mapinfo)

Drive Test

Measurements

Analysis Programs

Coverage

Dropped Calls

Call Setup Success

HandoverPerf.

Speech Quality

General Check

Verification of

RF NetworkDesign

Site Check


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Test Mobile Measurements

Collect RxLev measurements together with GPS co-ordinates Analyse on planning tool

Reasons for poor coverage:

serving cell not best server

handover problems

best server signal low

check site / network design

Analyse in terms of relevant

thresholds:

indoor level in-car level

outdoor level


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Test Types

Continuous drive test setup a test call and drive over an area for detecting lack of

coverage, missing handovers, interferences etc.

Spot test

detail measurement to be taken at dedicated problem spots for

detail analyzing of specific problem


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Collect / Analyse Drive Test Measurements

Test measurement (TEMS etc. together with a GPS)

Signal Strength

Co-channel and adjacent interference

Handover relations

Test types

Continuos drive test (Trace mode)

Spot test

Network performance test (Statistical mode)

Test Measurement

Collect MS measurement report data (Downlink only!!)


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Coverage: Analysis for Fulfilment of Coverage

Requirements (Urban, rural ...

areas, outdoor, in-car, indoor)

Dropped Call: Analysis for Dropped Calls due to

Interference, SW/HW failures,Transmission Network Failures

Call Setup: Analysis for Blocking and Capacity

Limitations, Analysis for Resource

Allocation Procedures

Handover: Analysis for Efficient HandoverPerformance

Speech Quality: Analysis for Interference

Analysis Programs


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Dropped Call Analysis

How to measure drive tests

repeated call setups (preferred)

continuous calls

OMC measurements

Reasons for dropped calls

lack of coverage

interference problems

handover problems

lack of synchronisation in network problems with other parts of the network


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Call Setup Analysis

Reasons for failed call setups lack of coverage

database problems

database inconsistencies

parameter settings, e.g.

RXLEV_ACCESS_MIN, RACHBT,

RACH_MAX_RETRANS

cell reselection related parameters

network congestion


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Handover Parameters

Fine-tuning of handover parameters Moving cell boundaries in order to

Enhance success rate for critical handovers

Minimise local interference at the cell edge

Traffic load sharing between cells

Compared to other opimisation measures improvement potentialis limited

Affected by

Measurement averaging

Power control parametersPS! Neighbours

should in general

be mutual


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Speech Quality Analysis

Parameters RxQual

Frame ErasureRate (FER)

Speech Quality Index (SQI)

Measurements

Drivetest

preferably continuous

call

OMC statistics

Causeforpoorquality

lowsignal strength

(coveragerelated

interference

lowsignal strength and

interference

Causes ofinterference co-channel interference

adjacentchannel

interference

intermodulation

mainly on one link only

multipathinterference


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Location Area Codes

Purpose identify location area

in incoming call is paged to all BTSs within LA

Large location area

advantage: less location updates (reduced SDCCH load)

disadvantage: more paging traffic

Boundaries should not cross high traffic areas

Cell reselection across LA boundaries

Parameter Cell_Reselect_Hysteresis (typ. 4 dB) used to avoid

unnecessary signalling due to ping-pong cell reselections


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Reporting (example)


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Advantages over test drives

Less labor intensive and time consuming

More comprehensive, based on large number of users

not limited to time of test drive

Uplink and Downlink analysis possible

Subscriber behavior mix of outdoor, indoor, incar use


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FINEFINE

TUNINGTUNING


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Digital Tilt Meter

GPS

Compass

Spanner

Screw Driver Set Safety Belt

Adjustable Wrench

Cutting Pliers

Mesuring Tape

Safety Shoe Map Info

Map Source

Google Earth

Tools


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Antenna Configuration

General points to check antenna type, e.g.

omni

directional 60, 90 or 120 degrees

electrical downtilt

cross-polarised

antenna azimuth angle (for directional antennae)

coverage targets

antenna tilt angle

electrical + mechanical diversity & isolation

e.g. space diversity,

polarisation diversity


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Site Check

Verify thatsiteisimplemented accordingto plan

Checkinstallatione.g.

antenna spacing (diversity, isolation)

antennaein onesectorareinstalledinthesame plane

antennae alignment

omni antenna installation

cableinstallation

k

a

Vertical spacing

d

Horisontal spacing

Rx

Tx

Rx Tx

a

5

ntennas mountedindifferent planes

a

a=

d d d

lignment ofantennas

T

d

k

Rx

Tx

Rxd

k2 k2

Omni


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Antenna Fine Tuning

Horizontal Plane:

Possible coverage weakness between sectors

Interference reduction

Traffic load distribution

Vertical Plane: Interference reduction

Possible coverage weakness in the short to medium distance

range

Traffic load distribution


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Omni vs. Sectorised

OMNI cells - more difficult to optimise

Electrical downtilt possible, however

same for entire cell

Parameters same for entire cell

Directional antennae narrower beam easier to control interference

tilting less efficient with wider beams

Sectorised cell site with differentdowntilt angles


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Tilting

Antenna downtilt often used to minimise interference Minimum: Vertical mail lobe pointing at cell edge

BSh

Maximum: First null angle pointing at cell edge


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0 0

Electrical Mechanical

Advantages:

Better back lobe characteristics

Better lower side lobe characteristics

Disadvantages:

Antennas are more expensive

Tilting

Electrical vs. Mechanical downtilt

A combination of

mechanical / electrical

downtilt may be used


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Reporting (example)


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thanksthanks

Documents

Drive Test Well Explained