Testing of GSM network

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Testing of GSM network
Katja.Koivu_at_omnitele.fi
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Contents

• GSM network quality audit
• Network quality benchmarking
• Optimisation
• Statistics / Operation Maintenance measurements
• Field measurements
• GPRS measurements
• Testing of special features

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• GSM
• Radio Network Quality Audit
• and Optimisation

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Background

• On what basis does the customer rate GSM
  operators quality ?
• Prices
• Coverage area
• Call blocking/dropping
• Speech quality
• Customer service
• Else?
• The user experienced service quality in GSM links
  directly to the performance of the radio network
• Differentiation from competitors

Radio network quality related!
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Optimisation outcome ?

• Network optimisation is a tradeoff between
  quality,
• traffic/revenues and investments.
• Without fine-tuned network the customer
  complaints are increased,
• work load is increased and marketing becomes
  inefficient
• Do you know how your network is performing ?

GSM network indicators of European
operator customer
Direct impact on customer satisfaction !
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Network quality benchmarking

• How does your networks quality match against the
  competitors ?
• and against the world standard ?

Example benchmarking statistics
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Field measurements

• Benchmarking
• Troubleshooting
• statistics, customer complaints
• Base station start-up
• Testing equipment
• Testing software e.g. TEMS Ericsson in a laptop
• Test mobile phones (one or more)
• Indoor/outdoor antenna
• Cables battery chargers

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Field measurements

• Testing route
• Roads, train
• Hot spot, pedestrian
• Urban, suburban, rural
• Test setup
• Idle mode
• Continuous call
• Call sequence (90s calls / 15s idle)
• Tested frequencies 900/900E/1800

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Example Call Success Rate
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Example SQI
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Network quality benchmarking

• Could there be an indicator that shows your
  network is underperforming ?
• Independent benchmark needed
• What kind of action should be taken to improve
  the situation ?
• Correctly targeted network optimisation

Example benchmarking statistics
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Network optimisation process
INPUTS
Customer Feedback
MANAGEMENT
MARKETING
Benchmarking
NETWORK PLANNING
Field measurements and performance evaluations
CUSTOMER SERVICE
Postprocessing
Operation Maintenance Measurements
Continuous process!
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Optimisation targets
Effective and economic use of network !
Satisfied customers Maximum utilisation of
hardware
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Troubleshooting
Omniteles engineers are experienced to encounter
all the major issues effecting the quality of
GSM networks

• Handover problems
• Quality problems
• Coverage problems New site location
  identification
• Network layers fine-tuning
• Capacity problematics
• LAC optimisation
• New feature implementation (software and
  hardware)
• Micro cells introduction
• Indoor coverage fine-tuning
• BSS parameter fine-tuning

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Dual Band considerations
Utilisation

• Traffic steering between
• 900/1800 layers
• Parameter optimisation
• Coverage/capacity
• GPRS strategy

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Frequency planning interference analysis

• Interference analysis
• Used by turns with the allocation in order to
  validate (and optimize, if necessary) the
  frequency (reuse) plan

• Frequency planning objectives
• QoS objectives
• Overall C/Ic and C/Ia requirements
• Cell-to-cell C/I requirements

• Interference check per channel
• Evaluation of the significance of the residual
  interference
• HO/Cell selection margin should be included in
  the analysis
• C/Ic (and C/Ia ) statistics per channel
• Interference per network
• On the dominance area
• C/Ic (and C/Ia ) statistics
• Shows the overall interference picture

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Interference reduction means

• Optimising is done frequency by frequency

• Antenna redirection
• the most predictable
• coverage is in danger
• Antenna tilting
• ideally very useful steepens the slope
• in practice difficult to predict
• should be always measured
• useful for large clearence angles
• Power reduction
• UL/DL interference power balance is lost
• coverage is lost
• not recommended

• All interference reduction means
• may generate problems in other frequencies

Reducing interference Improves network quality!
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Optimising adjacencies LAC

• Missing neighbours very often result in
  unnecessary dropped calls and bad quality
• Correct neighbour relations can be determined by
  analysing measurement results

Unnecessary LAC updates can easily increase the
singalling load significantly Increased
signalling reduces the room for payload !
Are your adjacencies and LACs optimised ?
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Optimising parameters
study theoretically the impact of the intended
change
select the set of performance parameters and
test cells
new conclusions
change the cell parameters under optimisation
measure with a test MS
-
happy with the results ?

measure the performance and compare to the ref.
performance
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happy with the results ?

apply the changes permanently in the
network/service area
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OM based performance parameters

• QOS as well as RF and capacity planning
  parameters assessed per cell, per BSC and per
  network

• RF planning parameters
• Number of calls
• TCH RF loss rate
• SDCCH RF loss rate
• TCH mean holding time
• Handovers per call
• Cumulative UL/DL level statistics
• Idle channel UL interference
• Power balance

• QOS parameters
• Dropped call rate
• Dropped call rate due to radio
• Cumulative UL/DL quality statistics
• TCH BH blocking rate
• SDCCH BH blocking rate
• (Call setup success rate)
• (Handover success rate)

• Capacity planning parameters
• TCH BH traffic (e.g. weekly and average of daily
  BH traffics)
• BH activity per subscriber (segment)
• Total TCH time (per subscriber)
• SDCCH weekly BH traffic
• BH paging load

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Example BH traffic

• 20 June 290 000 subs ? 17 mErl/subscriber
• Mean holding time ? -gt BHCA/subscriber

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Conclusion

• The GSM network optimisation process consists of
  complex technical measurements and analysis
• Every network is individually planned and thus
  have individual problems which decrease the
  quality
• Professionally performed optimisation will
  increase customer satisfaction

GSM network indicators of European
operator customer
How to increase the quality and capacity with
minimum investments ?
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How can Omnitele assist you?Radio network
quality audit and optimisation
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Performing the quality audit
To observe and follow the quality of the network
Why?
Where?
Predefined areas
Regularly, e.g. once a year
How often?
With measurements By comparing
How?
Who?
Independent from the operator and vendor

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Network quality audit -- Objectives --
Complete analysis of the quality perceived by
subscribers
Location of interference, inadequate signal
strength and quality, congestion
Proposal for corrective actions in both short and
long term
Comparison to the competitors and world class
standard
On-the-job training for Operators own staff

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Network quality audit -- Area definition --
The most important cities, roads, suburbs
Areas representing different kind of coverage,
different subscriber density etc.
Same basic area every time, expanded with
possible new coverage areas
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Measurement route definition

• ca. 1/3 of the of cells in the area
• 30 min. of driving for each
• covering the whole sub-service area
• distinction of areas with different required
  coverage probabilities
• following the foreseen traffic distribution
• all HO pairs tested
• closing loops major highways
• marketing should be consulted

• emphasis on
• the city
• the most important roads
• the most important suburbs
• the areas with foreseen difficulties

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Network quality audit -- Regularity --
Once a year if the network is quite stable
More often if the network is still under
construction
In addition to complete quality audit weekly
measurements are recommended
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Network quality audit --The auditor --
Should be independent from the Operators
Technical Department and the Vendor
Should have experience from other networks
Because, then ...
The comparison will be objective
The Operator gets the information what is the
performance level of the network compared
with the other networks
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Quality audit -- Comparison --
Predefined criteria the network should fulfill
Quality Index (measured indicators)
Comparison with competitors
Comparison with previous quality audits
By Quality Index

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Why Omnitele ?

• Long and extensive experience on radio network
  planning
• Dimensioning and nominal planning
• Site planning
• Parameter planning
• Network tuning and optimisation
• Experience from several equipment suppliers
• Projects
• GSM planning in Finland
• Radiolinja project (worlds first GSM network)
• GSM1800 city networks
• Ongoing Finnish 2G project (3rd Finnish operator)
• GSM planning abroad
• Italy Czech republic
• Netherlands Brazil

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Why Omnitele ?

• GSM network dimensioning/nominal planning for
  start-up operators
• Tanzania
• Jordan
• Pakistan
• Network audits and optimisation projects
• Finland
• Radiolinja
• City networks
• Finnish 2G
• Abroad
• Greece Ivory Coast Kuwait
• Togo Jersey Czech Republic
• Guernsey Faroe Islands Cyprus
• Andorra Bahrain

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GPRS Optimisation in general
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Optimisation Process

• Output
• Optimal parameter settings
• Dedicated/dynamic radio capacity allocation
• Traffic steering between the radio layers
• Coding scheme adaptation
• Different timers
• Optimal hardware configuration
• Protocol optimisation
• Key performance indicator definition and
  measurements
• Future plan winner strategy

• Input
• The business strategy for GPRS
• Existing and desired quality of the network
  (field measurements OMC studies)
• Congestion
• QoS of the existing network
• Interference
• Different vendor solutions
• Required services and expected usage

Best quality with minimum investment
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Measurement System Set-up
End
-
to
-
End data performance
End
-
to
-
End data performance
Data at
Data at
Data at
Data at
application layer
application layer
application layer
application layer
GPRS layer data performance
GPRS layer data performance
Data at
Data at
Data at
Data at
RLC/LLC layer
RLC/LLC layer
RLC/LLC layer
RLC/LLC layer
RF performance
RF performance
Air
-
interface
Air
-
interface
Air
-
interface
Air
-
interface
Server
GPRS Mobile
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Monitored Key Performance Indicators (KPI)

• C/I of the measured channels
• Average RLC throughput (kbit/s)
• Average LLC throughput (kbit/s)
• Average number of timeslots used by a single user
• CS usage ( of time in the CS1/CS2 )
• Average cell reselect time
• Network response time (RTT)
• RLC bit error rate
• ) Available only in networks with dynamic CS
  adaptation

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GPRS Parameter Planning (1)

• Goals
• To handle GPRS in cells with high CS (speech)
  traffic
• To steer the GPRS traffic to wanted cells
• Adequate definition of GPRS timers
• Radio interface capacity division between CS/PS
• Optimise the performance of specific service

Optimised end-user experience !
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GPRS Parameter Planning (2)

• Omnitele has profound hands-on experience with
• Alcatel GPRS parameters
• Ericsson GPRS parameters
• Nokia GPRS parameters

Troubleshooting
Daily planning Optimising
Drive tests
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Measuring GPRS network performance

• Data flow behaviour
• Re-transmissions
• Cell re-selections, RA updates etc.

• Number of time slots used per mobile
• Coding scheme usage

RLC and LLC Throughput
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GPRS Network performance benchmarking
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Why benchmark the network performance ?

• Performance of the GPRS networks vary
  significantly
• between the operators
• The QoS status of operators GPRS network is
  best
• determined by benchmarking the network
  performance
• against competitors performance and/or world
  class operators
• operating in different markets

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Benchmarking Results Examples

• Example country
• Three nation-wide GPRS operators
• Same drive routes in the benchmarking
• Significant differences in KPIs of the three
  operators

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Improving the Performance of Your Network

• After benchmarking the GPRS performance, the
  problem areas will be identified
• Recommendations for improvements are given
• Service optimisation plan will be made

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BSC Measurements

• In addition to end-to-end field measurements, BSC
  measurements can be performed from the BSC of the
  benchmarked operator
• Better overall picture of the problem cells
  Suggestions to improvements
• Some of the key issues that can be identified
  from BSC are
• Overall GPRS traffic
• Blocking of GPRS calls
• Retransmissions
• PCU loading
• Note The BSC measurements can only be
  benchmarked against Omnitele archive since there
  is no access to competitors BSC

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How can Omnitele assist you ?
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Example of Omnitele s GPRS Projects Network
acceptance and optimisation
1 Introduction   2 Description of field
measurements   2.1 GPRS measurement
model 2.1.1 Application layer performance
measurements 2.1.2 GPRS layer performance
measurements 2.1.3 RF performance
measurements 2.2 Monitored Key Performance
Indicators 2.2.1 Carrier to Interference ratio
for the measured channels (dB) 2.2.2 Coding
scheme usage () 2.2.3 RLC/LLC throughput
(kbit/s) 2.2.4 Cell reselection time
(s) 2.2.5 Routing area update time
(s) 2.2.6 Network response time
(s)   3 Findings during the Installation 3.1 Alc
atel acceptance tests 3.1.1 MFS acceptance
tests 3.1.2 Core acceptance tests 3.2 Detected
problems 3.2.1 MFS 3.2.2 Core   4 Integration
testing 4.1 Carrier to Interference
ratio 4.2 Coding scheme usage 4.3 Throughput 4.
3.1 Normal cell load throughput
measurements 4.3.2 High cell load throughput
measurements 4.4 Cell reselection 4.5 routing
area update time 4.6 Network response
time 4.6.1 Pinging with Windows Command
prompt 4.6.2 Pinging with different intervals
between the pings  
5 GPRS Parameter fine-tuning 5.1 Further routing
area update testing 5.2 Optimisation of the
coding scheme usage 5.2.1 CS_Lev
parameter 5.2.2 CS_Qual_1_2 / CS_Qual_2_1 5.2.3
TBF_CS_Period1 / TBF_CS_Period2 5.3 Congestion
control 5.4 network response time
optimisation 5.5 Other investigated
issues 5.5.1 Frequency scans in the east
coast 5.5.2 Missing adjacencies   6 Comparison
of finnish GPRS operators network
Performance indicators 6.1 Throughput
6.2 Cell Reselection time (s) 7 comparison of
different vendors GPRS features 7.1 Automatic
Link adaptation (ALA) 7.2 Congestion
control 7.3 Multiplexing users into the
Timeslots 7.4 TRX preference 8 suggestions for
GPRS network development 8.1 Alcatel GPRS core
rel2 and BSS software B7 8.2 Traffic
monitoring 8.3 Air-Interface compression
software 9 Conclusion
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How Can Omnitele Assist You?

• Contract negotiations
• Assistance in definition of the technical
  framework to the system specifications How
  should the GPRS system perform?
• Hands-on experience Alcatel, Ericsson and Nokia
  GPRS systems
• Implementation
• Verification of the system performance
  Specification of the operator acceptance tests
  and system integration tests
• Parameter planning, parameter fine-tuning and
  optimisation of the GPRS network
• Service optimisation
• WAPWeb Parameterstimers
• Content optimisation Performance Enhancement
  Proxy selection process
• MMS Radio capacity optimisation
• GPRS performance benchmarking
• Comparison of your GPRS networks performance to
  your competitors

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Please visit our web site www.omnitele.fi for
more information