DrivetestDrivetest

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

Work Process

CollectOMC Parameter

DatabaseRF Network Design

Cell File (TEMS)And

Dot Tab Site (mapinfo)

Drive Test Measurements

Analysis Programs

Coverage

Dropped Calls

Call Setup Success

Handover Perf.

Speech Quality

General Check

Verification of RF Network Design

Site Check

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

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

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!!)

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 CapacityLimitations, Analysis for Resource Allocation Procedures

Handover: Analysis for Efficient HandoverPerformance

Speech Quality: Analysis for Interference

Analysis Programs

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

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

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 potential is limited

– Affected by• Measurement averaging• Power control parameters

PS! Neighbours should in generalbe mutual

Speech Quality Analysis

• Parameters– RxQual– Frame Erasure Rate (FER)– Speech Quality Index (SQI)

• Measurements– Drive test

• preferably continuous call

– OMC statistics• Cause for poor quality

– low signal strength (coverage related

– interference– low signal strength and

interference

• Causes of interference

– co-channel interference

– adjacent channel interference

– intermodulation

• mainly on one link only

– multipath interference

Location Area Codes

• Purpose– identify location area– in incoming call is paged to all BTS’s 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

No serviceNo coverageNo System Availability

Network Element FailuresTransmission Network Failures

Low call setup success rateRF Network

No coverageInterferenceBlocking

Fixed Network BSS, SSSBlockingOverloadOther

High call drop rateRF Network

No coverageInterferenceHandover failure

Fixed Network BSS, SSSNetwork Element FailureTransmission FailuresOther networks

Mobile terminal

Poor speech qualityRF Network

No coverageInterferencePoor handover performance

Fixed Network BSS, SSSNetwork element failureTransmission network failureOther networks

Mobile Phone

Problem Symptoms

Reporting (example)

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

FINE TUNINGFINE TUNING

• 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

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

Site Check

• Verify that site is implemented according to plan• Check installation e.g.

– antenna spacing (diversity, isolation)– antennae in one sector are installed in the same plane– antennae alignment– omni antenna installation– cable installation

k

a

Vertical spacing

d

Horisontal spacing

Rx

Tx

Rx Tx

max 15 °

Antennas mounted in different planes

a

a=

d d d

Alignment of antennas

Rx Tx Rxd

k1

Rx

Tx

Rxd

k2 k2

Omni

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

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 different downtilt angles

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

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 ofmechanical / electricaldowntilt may be used

Reporting (example)

thanksthanks