Drive Test
Drive Test
Drive Test
OMC statistics provide an efficient means of evaluating performance of the entire network. However in addition to this it is extremely valuable to conduct drive test performance measurements for the following reasons: 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) AIRCOM International can conduct drive test data collection and analysis using the NEPTUNE drive test tool, and can provide comprehensive reports supporting all of the above requirements. This includes detailed competitor analysis and benchmarking supported by the PROBE benchmarking tool.
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Drive testing involves driving in a vehicle and collecting network data by making a lot of calls. The data collected includes data for serving cell as well as the neighbors. This data collected helps us to find and analyze the problems in the network. Equipment Necessary for Drivetesting. Vehicle Drive test mobile phone (e.g.Ericcson TEMS) External vehicle mounted GPS Laptop with drive test software and GPS connection capability.
Routine drive test forms a integral part of this process. Drive test routes are decided by the Network operator and these routes are
regularly drive tested and any problems found are reported.
These problems are then further analyzed and solved. Hence it is important that these drive test routes are selected carefully. Drive test routes should include all the major road, important location,
airports etc.
Also they should be able to cover most of the cells. Each drive test route should be typically 2 - 3 hours long.
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The drive test routes must be decided by the operator and a priority set on
the routes for testing.
The drive test routes are usually 2 - 3 hours in duration in order to ensure
that the data generated is of a manageable size.
The drive test teams use the Test Mobile equipment (e.g.TEMS) to make
test calls to the MSC test number on the network of 2 minute duration with a 15 second break.
All data is logged on the computer, location information is also taken using
a GPS receiver.
During or after completion of the drive test route, analysis of the data
collected is performed to identify areas of dropped or noisy calls.
After conformation as to what is causing the problem with the drive test route, the drive test engineer will attempt to find a solution to the problem. This can be one of a number of possibilities i.e. Power Change to BTS, Frequency Plan change, Neighbor addition required, etc. Once a possible solution to the problem has been found it may be possible in some circumstances to immediately attempt the solution via the OMC, this usually relates to minor database changes and adding neighbors. The solution is implemented and proven immediately. If the problem is rectified the change remains in place and a change request is raised for the solution for the purpose of keeping records of all changes in the network. If the solution requires a major database change or antenna work a change request must be raised via the Optimization Control Engineers. After the solution is implemented a retest of the problem area is carried out to confirm the problem has been solved
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Problem drive testing Any problem reported by statistical analysis, routine drive testing, customer care centre , alarms need to be analyzed in detail to find a solution. Problem specific drive testing is a important tool which helps us do it. Here we make a list of problematic cell and drive test them thoroughly to analyze the problem. There may be many different methods which a optimization engineer may employ for the analysis. As an example, if a particular cell is being interfered the frequency of the cell may be changed temporarily to identify the interferer. Also the levels and TA at which the cell is being interfered may be analyzed. Here the data collection and analysis are done simultaneously.
Cell Coverage Analysis Drive Test It has been found that normally that the coverage and server area of the cells differ from the planned area. Hence it is often found that new cells that come on air serve far more or much less area than initially planned and same could be the case with the coverage. This could lead to two problems. If the server area is less than planned it could lead to coverage holes or poor cover areas. If the coverage area is more than planned it may cause interference in the network. Hence it is important that once new cells come on air they must be thoroughly drive tested to determine their server and coverage areas. If any major deviation from the initially planned design is found the cell sites should be optimized.
Scanning This is a important feature of the drive test software. It enables us to lock onto a particular frequency during the drive test which is helpful in determining the server area of a cell. Also we scan a set of frequencies and have a graphical display of the same or can also be stored for further analysis. This is helpful in finding interfering frequencies and also in finding clear frequency.
Optional Features Some drive test equipment provide supplementary features which help during drive test. Map displaying the drive tested area showing the major roads, location, cell sites is provided ,this helps us to be always aware as to where we are in the network. Also some vendors provide spectrum analyzer which helps in finding the interfering frequencies and to find clear frequencies.
Using the drive test equipment we can monitor the following Status Information
Error reports
Mode reports Layer 2 messages
Layer 3 messages
Status Information In status information we get the following information General Information: This includes the Latitude ,longitude data, server call name, Marker ,data, time , log file name etc. Serving cell: This includes Cell Identity, BSIC, ARFCN ,MCC, MNC, LAC. Serving + Neighbor cell data: This includes CI, BSIC, ARFCN, Rxlev, C1 and C2 for the serving and the best 6 neighbors. Dedicated channel: This includes data such as Channel number, Timeslot number, Channel type and TDMA offset,hopping information and channel mode. Radio Environment: This includes serving cell,lat , long, rxlev, rxqual, TA, DTX and RL Timeout counter information.
Error reports If any errors are reported during the call they can be analyzed from this report. Mode reports These are the channel mode reports.
Layer 2 messages
All the layer 2 messages can be analyzed. Layer 3 messages All the layer 3 messages can be analyzed.
MEASUREMENT METRICS
GSM Drive Test Metrics GSM drive test data can be presented in a number of ways. A combination of graphical presentation and statistical analysis is recommended. The examples below show measurements for 2 networks for comparison purposes. Graphical Presentation The following parameters can be displayed on a map, allowing the visualisation of specific problems by location: Route Plots RxLev Full: Route Coverage Plot RxLev Sub: Route Coverage Plot (excluding dummy bursts during DTX operation) RxQual Full: Route Quality Plot RxQual Sub: Route Quality Plot (excluding dummy bursts during DTX operation) FER: Route Frame Erasure Rate Plot MS TX Power: Route plot of Mobile Transmit Power SQI Plot: Route Plot of Speech Quality Index (or equivalent, if available) Events Events plots may be superimposed on one of the above route plots, eg. RxLev or RxQual. Call Drops: Plot of dropped call events Setup Failures: Plot of call setup failure events HO Failures: Plot of Handover Failure events HO Success: Plot of Successful Handover events (if required)
GPRS Drive Test GPRS drive test data can be presented in a number of ways, much the same as GSM drive test data. A combination of graphical presentation and statistical analysis is recommended. Graphical Presentation The following parameters can be displayed on a map, allowing the visualisation of specific problems by location: Route Plots UL/DL RLC Throughput: Radio Link Layer data throughput UL/DL LLC Throughput: Logical Link Layer throughput (user data) UL/DL RLC Block Error Rate (BLER): Radio Link Block Error Rate UL/DL RLC Retransmission Rate: Radio Link Retransmission Rate UL/DL Coding scheme used (CS1-4): Allocated Coding Scheme UL/DL Number of timeslots used: Allocated timeslots Events Events plots may be superimposed on one of the available route plots, eg. RxLev, RxQual, RLC throughput, etc. PDP Context Activation Failure: Failure to activate PDP Context (Packet Data Protocol) PDP Context Loss: Loss of PDP Context (GPRS Call Drop)
Additional GPRS Metrics The following metrics are also useful, if available: UL/DL TCP Throughput UL/DL UDP Throughput Delay (Latency) UL/DL/Round-trip IP Packet Loss Rate Jitter
Following types of analysis are carried out: Coverage Analysis Interference Analysis: Handover Analysis Neighbour Analysis: Call Analysis: Layer 2 Analysis Layer 3 Analysis Level Analysis Quality Analysis To identify co-channel and adjacent channel interference related problem To identify missing neighbours. To check network performance against predefined KPIs like DCR,CSSR,CSR,Call Setup time,Call hold time etc.
RxLev Distribution
RxLev Distribution
4500000
Number of Measurements
4000000 3500000 3000000 2500000 2000000 1500000 1000000 500000 0 0-10 11-20 21-30 31-40 41-50 51-60 61-70
Network A Network B
RxLev
RxQual Distribution
RxQual Distribution
12000000
Number of Measurements
Network A Network B
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FER Distribution
Frame Erasure Rate Distribution
12000000
Number of Measurements
Network A Network B
FER
MS TX Power
Mobile Transmit Power Distribution
10000000
Number of measurements
Network A Network B
MS TX Power
1.3%
Average SQI
Average Speech Quality Index (SQI)
24 21 SQI 18 15 12 9 6 3 0.0 Network A Network B 19.3 19.1
12
18
26
33
41
52
63
83
12
18
26
33
41
52
63
83
NEPTUNE is a sophisticated test and diagnostic optimization tool on the market and, uniquely, does not simply collect, log and display the necessary data, but also suggests possible causes and solutions to any problems. NEPTUNE can be used for GSM900, 1800, 1900 and Dual Band and GPRS technologies, fully supporting dual-mobile tests and measurement such as GSM900/DCS1800 or GSM1900.
Features
State-of- the-art PC based optimization tool delivering real time
analysis capabilities. User friendly with intuitive menu structure making it ideal for both real-time and post measurement analysis. Automatic fault finding and problem solving diagnostic capabilities Live call analysis
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Analysis
In terms of data analysis, NEPTUNE provides: Full summary of actual signal coverage (RXLev) Full summary of received quality (RXQual) Enhanced handover performance and level distribution calculations Statistical Analysis Replay & Analysis Call Success
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Call Analysis
NEPTUNE can analyze live calls, call success, signal levels and call quality and provide separate graphical displays on the 2D Map View in real time. NEPTUNE also incorporates the following features - mean and worst call levels, quality, detailed comparative summary of cells signal strengths, analysis of sites which utilize the co-channel and adjacent channels and results of co-channel and adjacent channel interference. The user may define thresholds for acceptable signals and quality levels.
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Statistical Reporting
Once a file is loaded, NEPTUNE will automatically generate a statistical summary enabling the improvement of ongoing system engineering to be measured.
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Handover Analysis
All handovers are analysed and problems are identified.For each problem, causes and solutions are suggested. NEPTUNE examines handovers in great detail:
Problem areas are automatically identified Handover success/failure is shown on route Position failure is located on XY graph Cause/solution proposed for each failure Step-by-step replay control allows every stage of handover to be broken down for detailed analysis Forced Handover
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Neighbour Analysis
NEPTUNE summarizes critical information relating to the neighbour relations and, once a problem is perceived, will provide the following:
The serving cells ID and full geographic location The ID and full geographic location of the Neighbour cells that are either missing or have not been measured Problem areas are separately displayed on the 2D map view
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Diagnostic Capabilities
NEPTUNE is the only system to provide automatic faultfinding and problem solving diagnostic capabilities. Full location and proposed solutions are provided for: Low signal level Poor speech quality Failed handovers Missing system neighbour definitions
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PROBE
PROBE is an add on module to Neptune that a gives you the ability to perform time-based, operator based and distance based analyses. As a network analysis tool, PROBE differs from the existing analysis functionality of Neptune because the statistics generated show the system s problems as a whole rather than pin-pointing each and every problem.
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Features
Ideal for both real-time and post measurement analysis Displays a networks Key Performance Indicators Key Performance Indicators are combined to produce the Network Quality and Efficiency Factor Statistical and graphical display Long and short term cost savings due to competitive pricing and the substantial shortening of the optimization process
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number of handovers that occurred per call within the testmobile survey.
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Level Statistics
The level statistics refer to the received signal level for a mobile:
Level (Full) Distribution (between -46 and -110) Level (Sub) Distribution (between -46 and -110) Cumulative Level Distribution Level Banding
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Quality Statistics
These provide with important system level information about the received quality:
Quality full and Sub distribution
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Call Statistics
Offer similar functionality to the call success analysis performed for every survey in NEPTUNE
Call Holding Time - Displays the duration of each call. Call Performance - Details for the Setup rate, Failure
rate and Release rate.
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Cell Statistics
Important statistics for all the cells that were observed within a survey are provided. Cell Domination Cell poor Quality Distribution
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EXPANSION STRATEGY
4.Service model
1.Propagation model- A model needs to be defined which is used to simulate the propagation characteristics of the environment. 2.Coverage model-Based upon the link budget various coverage thresholds need to be defined for various clutter categories. 3.Service model-Based upon the requirements a service model is defined which will enlist the services to be provided like voice,data,SMS,VMS etc. 4.Traffic model-This model gives a description of the traffic growth that needs to be implemented vis a vis service model and demographic distribution of subscriber.Traffic model also gives an idea about the mE/sub for a region for different offered services.
Based upon all the models an Expansion strategy is formulated.The expansion strategy should meet the following objectives:
1. The new areas should be provided adequate coverage based upon the coverage model.
2. The congestion which is existing in the network should be removed by proposing Delta sites which are over and above the traffic which needs to be distributed for expansion. 3.Based upon the traffic model new sites should be proposed. Demographic distribution of the data should be done based upon existing traffic and by mapping the additional sites on the hotspots. 4.The KPIs set for the network should be met after addition of the new sites.Hence the network needs to be optimised.
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