Drive Test & Analysis

Rahul Rode

NPD GTL

Contents

INTRODUCTION NETWORK PROBLEM IDENTIFICATION REQUIREMENT FOR DRIVE TESTING DRIVE TEST PROCESS DRIVE TEST OUTPUTS MEASUREMENT METRICS DRIVE TEST ANALYSIS

INTRODUCTION Every alive Network needs to be under continues control to maintain/improve The performance. Drive test is basically the only way to keep track of the n/wBy looking deep into collecting & analyzing drive test data. Drive testing is the most common and maybe the best way to analyze NetworkPerformance by means of coverage evaluation, system availability, Networks Capacity, networks retainability and call quality. Although it gives idea only on Downlink side of the process.

The drive testing is basically collecting measurement data with a TEMS phone,But the main concern is the analysis and evaluation part that is done after Completion of the test.

Remember that you are always asked to perform a drive test for not only showingThe problem, but also explaining them and providing useful recommendations to Correct them.

Network Problem Identification

Drive Test

OMC Statistics

Customer feedback

Requirement for Drive testing

Test the network from the subscribers’ point of view

Test the complete system, end-to-end (mobile-to-land)

Benchmark performance against competitor networks

Test specific important routes and areas

Test in-building coverage for specific buildings (walk test)

Problem Drive Testing Problems reported by statistical analysis, routine drive testing,

customer care centre , etc

List of problematic cells identified and drive tested thoroughly to analyze the problem

Data collection and analysis done simultaneously

Drive Test Process

Drive Test Equipment Data collected to find and analyze problems in the network

Equipment necessary for Drive testing

Vehicle Drive test mobile phone External vehicle mounted GPS Laptop with drive test software and GPS connection capability

TEMS INVESTIGATION Hardware Configuration Minimum Hardware Configuration for laptop to cope with connected

one mobile station and one GPS to standard interface connected to com ports.

PC : Pentium III 500MHz , 256 MB Ram Ports : Serial Port, USB Port, and PCMCIA Card will be helpful. Graphics with min. 16 bit High Color Sound Card and Speaker for audio indications. For more mobile connections min. 512 MB Ram and better

processor. OS : Windows 2000, Windows XP Software : Min. Internet Explorer 5.0 or more for report generator

and online help.

Drive Test Setup

General Considerations

• Routes chosen to be representative of the part of the network under study

• If applicable ,collect GSM speech and GPRS drive test data together

• Drive test to be carried out preferably during peak traffic hours

• Calls to be made preferably mobile to a fixed number

• Call duration to be equal to the average call duration for the network

• For a typical metro city, at least 1000 calls required for good statistical confidence

 

Drive Test Types

Routine Voice call drive test, short call & long Call. Data Drive. MMS , SMS Drive test. Comparative Drive. Problem specific drive test Cell coverage analysis drive test. Walk test.

Routine Drive Test Network is monitored on a regular basis

Drive test routes to include all the major roads, important locations, etc

Routes regularly drive tested and problems further analyzed and solved

May require removing interfering carrier, Power Change to

BTS, Frequency Plan change, Neighbor addition , etc.

Problem Drive Testing Problems reported by statistical analysis, routine drive testing,

customer care centre , etc

List of problematic cells identified and drive tested thoroughly to analyze the problem

Data collection and analysis done simultaneously

Cell Coverage Analysis Drive Test Usually carried out for new planned sites in the network

New cells to come on air are thoroughly drive tested to determine their server and coverage areas

Optimisation to be carried out for any major deviation from the initially planned design

Optional Features

Walk test support

On line map display of the route

Scan feature

Drive Test Outputs

Display…..Status InformationStatus Information

• General Information: Includes Latitude & longitude, server cell name, date, time , log file name etc

• Serving cell: Includes Cell Identity, BSIC, ARFCN ,MCC, MNC, LAC

• Serving + Neighbor cell data: Includes CI, BSIC, ARFCN, Rxlev

• Dedicated channel:Includes Channel number, Timeslot number, Channel type, hopping information

• Radio Environment: Includes serving cell, Rx_Lev, Rx_Qual, TA, DTX and RL Timeout counter information

GSM Drive Test Metrics Route Plots

RxLev FullRxLev SubRxQual FullRxQual SubC/IBCCH

EventsCall DropsSetup FailuresHO FailuresHO Success

Drive Test Analysis

Analysis Types Coverage Analysis: Level Analysis

Quality Analysis

Interference Analysis: Co-channel and adjacent channel interference

Handover Analysis: Intra cell & inter cell Handover

Neighbour Analysis: Missing neighbors

Call Analysis: Call Setup time, Call hold time etc.

Current Channel

Definitions:

1. Time: It is system time of computer.

2. Cell name: It displays the name of the sector which is serving according to the cellfile that is loaded in TEMS.

3. CGI : It stands for the Cell Global Identity which is unique for every sector of the site. It consists of MCC,MNC,LAC,CI.

MCC: Mobile Country Code 0 – 999 (e.g. 404), MNC: Mobile Network Code 0 – 99 (e.g. 98) LAC : Location Area Code 0 -65535 (e.g. 5101) CI: Cell Identity 0 – 65535 (e.g. 11001)

Current Channel

Cell GPRS Support: Tells sector is having GPRS or not. Values are Yes or No .

Band : It tells in which Freq. Band mobile is operating e.g. GSM 900/ 1800.

BCCH ARFCN: It tells by which BCCH is the mobile station getting served.

TCH ARFCN: On which Traffic Freq. call is going on.

BSIC (Base Station Identity Code) : It is combination of Network Color Code (NCC) (0 – 7) & Base Station Color Code (BCC) (0 – 7). e.g. 62. It is decoded by mobile on every Sync. Channel Message.

Mode: It is shows in which state is mobile operating, Idle, Dedicated & Packet.

Time slot: On which time slot of current TCH call is going on. Viz. time slot no. of TRX.

Current Channel

Channel Type: Type of channel mobile is getting now. Like BCCH / SDCCH/8 + SACCH/C8 or CBCH / TCH/F +FACCH/F +SACCH/F.

Channel Mode : Shows mode of coding like Speech Full Rate of Half Rate.

Speech Codec: It shows FR for Full Rate, HR for Half Rate & EFR for Enhanced Full Rate.

Ciphering Algorithm : It shows ciphering algorithm used by the system to protect data for privacy. E.g. Cipher by A5/2.

Sub Channel Number: It is displayed at a time when mobile is on dedicated mode at time of call setup when it is getting SDCCH at that time it shows which SDCCH it is getting out of 8 available. E.g. 2.

Current Channel

Hopping Channel : It shows that current sector is having hopping feature or not. Values are Yes or No.

Hopping Frequencies : It displays no. of freq. on which mobile is allowed to hop. viz. MA List for hopping of that sector.

Mobile Allocation Index Offset (MAIO): It is the number which tells from which freq. from given MA list for sector hopping has to be started. E.g. 0 means sector will start from first freq. to hop.

Hopping Sequence Number (HSN) : Indicates sequence in which frequencies are allowed to hop from the MA List. 0- 63. 0 for Cyclic Hopping, 1 – 63 random hopping sequences.

Radio Parameters

RxLev : Receiving level in terms of dBm that mobile is receiving from the site. Range of -30 dBm to -110dBm.

RxQual : Quality of voice which is measured on basis of BER. Range of RxQual 0 -7.

FER : Frame Erasure Rate it represents the percentage of frames being dropped due to high number of non-corrected bit errors in the frame. It is indication of voice quality in network.

BER Actual : Ratio of the number of bit errors to the total number of bits transmitted in a given time interval. BER is a measure for the voice quality in network.. Depending on BER RxQual is measured. E,g, BER 0 to 0.2 % corresponds to RxQual 0. Max. BER countable and useful is up to 12.8 % which corresponds to RxQual of max. 7.

Radio Parameters

SQI : SQI is a more sophisticated measure which is dedicated to reflecting the quality of the speech (as opposed to radio environment conditions). This means that when optimizing the speech quality in your network, SQI is the best criterion to use. SQI is updated at 0.5 s intervals. It is computed on basis of BER and FER. For EFR 30, FR – 21 & HR – 17 are respectively ideal values.

C/I : The carrier-over-interference ratio is the ratio between the signal strength of the current serving cell and the signal strength of undesired (interfering) signal components. It should be atleast > 9 .

MS Power Control Level : Displays range of power control from 0 to 8 depending upon network design. E.g. 0 means no power control and 1 means level that is defined by operator viz. 2 dBm less acc. To airtel.

Radio Parameters

DTX : Discontinuous transmission (DTX) is a mechanism allowing the radio transmitter to be switched off during speech pauses. This feature reduces the power consumption of the transmitter, which is important for MSs, and decreases the overall interference level on the radio channels affecting the capacity of the network..

TA : Value that the base station calculates from access bursts and sends to the mobile station (MS) enabling the MS to advance the timing of its transmissions to the BS so as to compensate for propagation delay. Value of 0 means MS in radius of 550mt. From BS.

Radio Parameters

DTX : Discontinuous transmission (DTX) is a mechanism allowing the radio transmitter to be switched off during speech pauses. This feature reduces the power consumption of the transmitter, which is important for MSs, and decreases the overall interference level on the radio channels affecting the capacity of the network.

FULL VS SUB Values

In GSM, there are two types of values presented for RX QUAL, namely RXQUAL FULL and RXQUAL SUB, RX LEVEL, the parameter representing the signal strength also has similar FULL and SUB values.

The FULL values are based upon all frames on the SACCH multiframe.

If DTX DL is used in the network, the SUB set must be used, and if not, the FULL values are preferred due to their higher confidence.

Need for DTX

To increase battery life To reduce the average interference level DTX is done by DTX handlers

System Info message Types

Eight types of system information messages. System info message type 2 and 5 have 2 sub types i.e.

2bis, 2ter & 5bis, 5ter. System info messages can be logically grouped into two

type, Idle mode and active mode. In Idle mode the system info messages are transmitted

on BCCH while in active mode the system info messages are transmitted on downlink SACCH.

SYSTEM INFORMATION

Type 1: Cell channel description, RACH control (Only used during Frequency hopping).

Type 2: Neighbor Cell description, NCC permitted, RACH control. 2 bis: Neighbor cell description (extension), RACH control, 2 ter: Additional multiband information, Neighbor cell description (other band).

Type 3: Location area identity, Cell identity, Cell options, Cell selection, RACH control.

Type 4: Location area identity, Cell selection, RACH control, CBCH control & description.

Type 5: Neighbor Cell description. 5 bis: Neighbor cell description (extension). 5 ter: Additional multiband information, Neighbor cell description (other band).

Type 6: Location area identity, Cell identity, Cell options, NCC permitted. Type 7: System info 7 rest octets have the same format as the sys-info 4. Type 8: System info 8 rest octets have the same format as the sys-info 4.

Serving Neighbor

Cell Name : Name that describes the neighboring cell as per the cellfile. ARFCN : Channel number mobile receives as neighbor. BSIC : BSIC of the neighboring cell. RxLev : Receiving Level in dBm of neighboring cell. C1 & C2 : These are the cell path loss criterion and cell reselection criteria. Valid during idle mode of mobile

station. C31 & C32 : GPRS signal strength threshold criterion C31 and GPRS cell ranking criterion C32. Valid both

in packet idle and packet dedicated mode.

Example showing every window

TYPES OF SWAP

1. PARTIAL SWAP.2. SECTOR SWAP.

In Partial swap TX RX cable Swap, and in sector swap total sector

Found in another direction means planned orientation is 1st 70, 2nd 170, 3rd 340,

we found 1st 170, 2nd 70, 3rd 240, in sector swap also we found cyclic swap, in

That reverse of planned orientation.

Find out swap by drive in Idle.

Remove the swap by tracing cable.

Planned orientation Found orientation

1st Sector

2nd Sector

3rd Sector 2nd Sector

1st Sector

3rd Sector

Multi coupler

Duplexer

Combiner

TRX

BTS CONNECTION

CONNECTION FROM ANTENNA TO BTS

Antenna Tilt

Goals of Antenna Tilt 1.Reduction of Overshoot 2.Removal of insular Coverage 3.Lowering the Interference 4.Coverage Improvement of near area 5.Adjustment of Handover

Antenna Tilt can be Given in 2 Ways 1. Mechanical Tilt 2. Electrical tilt

Mechanical Tilt

A. Advantages 1.Adjustment of Vertical Tilt Possible 2.Cost Effective 3.Fast adjustment Possible and easy to Change

B. Drawbacks 1.Sidelobes are less tilted 2.Accurate adjustment is difficult

Electrical Tilt

Advantages 1.Same Tilt for Both Main and Side Lobes 2.no adjustment error

Drawbacks 1.Adjustment of electrical tilt mostly not possible

HOW TO MAKE DT PLOT REPORT

ORIENTATIONS :-

80, 170, 290

Antenna Addition in 1ST Sector.

SI – 808 WALUJMIDC_IDU BSC93WLJ

SI – 808 WALUJMIDC_IDU BSC93WLJ RX LEVEL GRID = 200 M

Site is Down

AGRI

LANDAGRI

LAND

Narrow Roads

SI – 808 WALUJMIDC_IDU BSC93WLJ RX QUALT. GRID = 200 M

ANTEENA

CLUTTER

SI – 808 WALUJMIDC_IDU 1ST SECTOR ORIENTATION 80O

ANTEENA

CLUTTER

SI – 808 WALUJMIDC_IDU 2ND SECTOR ORIENTATION 170O

ANTEENA

CLUTTER

SI – 808 WALUJMIDC_IDU 3RD SECTOR ORIENTATION 290O

SI – MG3528 CANPACK_IDF BTS