Drive Testing in Mobile Networks

Presentation by:

Naveen Jakhar, ITS

& Chetan Sharma, ITS

What is Drive Testing:

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• Drive Testing is a method of measuring and assessing the coverage, capacity

and Quality of Service (QoS) of a mobile radio network.

• Drive testing is principally applied in both the planning and optimization

stage of network development.

• Drive tests are the most common measurement tool used by operators, to

probe the quality status and solve network problems.

Why Drive Testing?

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• To check deployment of new network sites in order to meet coverage,

capacity and quality requirements

• Optimization of the network

• Benchmarking of performance

• Trouble shooting

• To verify the performance after an upgrade or reconfiguration of the

network

Drive Testing:

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• It is conducted for checking the coverage criteria of the cell site with the RF

drive test tool.

• The data collected by drive test tool in form of Log files are assessed to

evaluate the various RF parameters of the network.

• The technique consists of using a motor vehicle containing mobile radio

network air interface measurement equipment that can detect and record a

wide variety of the physical and virtual parameters of mobile cellular service

in a given geographical area.

Data Acquired from Drive Test:

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The dataset collected during drive testing field measurements can include information such as

• Signal intensity

• Signal quality

• Interference

• Dropped calls

• Blocked calls

Data Acquired from Drive Test…

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• Call statistics

• Service level statistics

• QoS information

• Handover information

• Neighbouring cell information

• GPS location co-ordinates

Types of Drive Testing:

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1. Network Benchmarking

2. Optimization & Troubleshooting

3. Service Quality Monitoring

The results produced by drive testing for each of these purposes is different.

Network Benchmarking:

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• Sophisticated multi-channel tools are used to measure several network

technologies and service types simultaneously to very high accuracy and

collect accurate competitive data on the true level of their own and their

competitors technical performance and quality levels

Optimization and Troubleshooting:

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• Optimization and troubleshooting information is more typically used to aid

in finding specific problems during the rollout phases of new networks or to

observe specific problems reported by consumers during the operational

phase of the network lifecycle.

Service Quality Monitoring:

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• Service quality monitoring typically involves making test calls across the

network to a fixed test unit to assess the relative quality of various services

using Mean opinion score (MOS).

• Service quality monitoring is typically carried out in an automated fashion.

Equipment used in drive test:

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• A laptop computer - or other similar device;

• Data collecting software installed on the laptop;

• A Security Key - Dongle - common to these types of software;

• One mobile phone for each mobile network that is being tested;

and

• One GPS antenna.

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Test Methods:

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Test Methods Purpose

Idle It is used to record the network condition at idle state and

the level and C/I on BCCH

Dedicated _Short Call

(120 sec)

It is mainly used for testing the accessibility and mobility of

network. Also used for checking successful completion of

call

Dedicated _Long Call

(entire duration of drive

test)

It is mainly used to test the retainability and sustainability.

e.g. Call drop rate, Handover Success rate, etc.

Analysis of Drive Test Data:

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• The drive test data is collected through data collecting software like TEMS.

• TEMS investigation 14.x and above.

• Test Mobile System(TEMS) is a technology used by telecom operators to measure, analyse and optimise their mobile networks. It is considered as basic tool to perform wireless network drive testing, benchmarking and analysis.

Key Performance Indicators:

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• Accessibility (Call set-up success rate) (%)

• Retainability (Dropped calls) (%)

• Mobility (Handover success rate) (%)

• RF Coverage (%)

• Rx Quality (%)

• Carrier over Interference (%)

Accessibility:

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Accessibility is the ability of a service to be obtained within

specific tolerances and other given conditions, when requested by

the user. In other words, the ability of a user to obtain the

requested service from the system. Accessibility is monitored by

measuring Call Setup Success Rate (CSSR) which is defined as the

ratio of Established Calls to Call Attempts.

Retainability:

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Retainability is “The ability of a service, once obtained, to

continue to be provided under given conditions for a requested

duration.” For determining the Retainabilty the regulation

prescribes three important parameters namely Call drop rate

(CDR), Worst affected Cells having more than 3% TCH drop and

Connection with good voice quality.

Mobility:

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In a cellular system a base station has only a limited coverage

area. Hence it is possible for a moving subscriber to be out of

range of a base station while making a call. The process by which

a mobile telephone call is transferred from one base station to

another as the subscriber passes the boundary of a cell is called a

handover. The Handover success rate (HOSR) more than 95% is

considered to be good.

RF Coverage:

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RF Coverage relates to the geographical footprint within the

system that has sufficient RF signal strength to provide for a

call/data session. The Coverage rate of an operator is calculated

basis of %age of samples in which the receive level (Rx) is better

than -85 dbm at street level.

Rx Quality:

• For measuring voice quality, Rx Quality samples on a scale from 0 to 7 for

GSM operators are measured. As per the TRAI QoS norms, Rx Quality

between 0- 5 for GSM operators is considered to be good, whereas Rx

Quality beyond this benchmark is considered to be poor. TRAI has set down

the QoS norm requiring connections with good voice quality to be >95%.

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Carrier over Interference (C/I):

• The carrier-over-interference ratio seeks to test the level of optimization of

the signal strength of a network. It is the ratio between the levels of the

signal strength of the current serving cell to that of the signal strength of

undesired or interfering signal components. The measurement range extends

from 0 dB to 30 dB. A C/I below 4 dB would normally result in a dropped

call. The C/I values between 9 and 15 is acceptable; while values between 15

and 30 are considered good.

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QoS Parameters – Reporting by TSPSN Name of parameter

Bench

mark

Averaged over a

period

A Network Service Quality Parameters:

(i) Network Availability

BTSs Accumulated downtime (not available service) ≤ 2% One Month

Worst affected BTSs due to down time ≤ 2% One Month

(ii) Connection Establishment (Accessibility)

Call Set - up Success Rate (with in licensee's own

network)≥ 95% One Month

SDCCH/Paging Channel Congestion ≤ 1% One Month

TCH Congestion ≤ 2% One Month

(iii) Connection Maintenance (Retainability)

(a) Call Drop Rate ≤ 2% One Month

(b) Worst affected cells having more than 3% TCH drop

(call drop) rate≤ 3% One Month

(c) connections with good voice quality (Rx Quality) ≥ 95% One Month

(iv) Hand Over Success Rate(HOSR) (Mobility) ≥ 95% One Month

(v) Carrier-over-interference ratio (C/I) >= 9dB One Month

Analysis:

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Drive Test Route (Mumbai)

Accessibility (%):

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Retainability (%):

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Mobility (%):

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RF Coverage (%):

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Rx Quality (%):

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Carrier over Interference (C/I) (%):

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Overall Operator Analysis

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Analysis of the RF drive report

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