Company confidential
MODEL TUNING WITH EXISTING GSM BTS AND TEMS GUIDELINES The information contained herein is the property of Asiacell and is provided on condition that it will not be reproduced, copied, lent or disclosed, directly or indirectly, nor used for any purpose other than that for which it was specifically furnished
AUTHOR
Chatchai Wiboonsittichok
DOCUMENT OWNER
Chatchai Wiboonsittichok
DIVISION
RF and Optimization
DEPARTMENT
Technical
CONFIDENTIALITY STATUS
Technical
DOCUMENT REVISION 1.0
1.0
REVIEW PERIOD Page 1 of 18
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Company confidential Document Release History Version no
Release Date
1.0
11 November 2006
Purpose
Document Review Team Name
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Name Division/Department Approvals Approved By AUTHOR:
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Date
Chatchai Wiboonsittichok Nov 11, 2006
QA REPRESENTATIVE: DOCUMENT OWNER: GENERAL MANAGER: Page 2 of 18
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Table of contents 1. INTRODUCTION 1.1 PURPOSE 1.2 SCOPE 1.3 DEFINITIONS 2. MODEL PARAMETER TUNING PROCESS 3. AREA AND SITE SELECTION 4. AREA AND SITE SURVEY 5. DRIVE TEST WITH TEMS 5.1 Get ready to drive test 5.2 TEMS configuration 5.3 Drive test 6. POST PROCESSING 7. CALIBRATION 7.1 Preparing calibration 7.2 Manual calibration 7.3 Auto calibration 8. EQUIPMENT 9. APPENDIX 9.1 RF data inspection list form 9.2 Signia CW data (*.hd) 9.3 Data file (*.DAT)
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1. INTRODUCTION In order to plan a network using Asset prediction tools, accurate models are required. As models use clutter offsets for estimating the losses, the clutter offsets must be tuned for the area where predictions are going to be made. By comparing actual drive test measurements with prediction made by the model, the model parameters, clutter offsets can be tuned Due to lack of CW measurement tools in our network, it is a good practice to select the existing GSM sites replaced of CW test transmitter and TEMS replaced of CW receiver. 1.1 Purpose The purpose of this guideline is to present a set of tuned model parameters to be used for the radio network planning and optimization department in Iraq during CW measurement equipment set is acquiring so that we can minimize the current mean, RMS and standard deviation error between prediction and actual and good for practice. In additional this document can help a local engineer more understand the model tuning for preparing the CW measurement activity during CW measurement equipment set is acquiring. 1.2 Scope Model tuning for radio network planning department in Iraq. The one city was selected first: Sulaimaniyah. This document also considers model tuning whenever there is no test transmitter or signal generator available, the drive test log files from TEMS cannot actually be imported in the asset planning tool without ADVANTAGE the additional software of Aircom or modifying file format before therefore this exercise takes a time consuming. The result of this model tune may not be accurate compare with using CW test transmitter because; - This method observes a measurement data from existing GSM site which is modulated by carrier and not continuously wave (TDMA technique). In correctly, pure sine wave is required for this. - The Co and adjacent channel will make an insufficient sample during drive test. - RF systems such as antenna, feeder, TRX is not a testing equipment and not passed calibrating.
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Company confidential - Some clutters in Asset database are not corrected due to they has not updated for a long time while the city in Sulaimaniyah is growing and expanding up continuously. - Due to Sulaimaniyah is not a big city, some clutters can not be found, they can not be calibrated and hence they can not be found a clutter offset. - The best existing site may be not found in each clutter type therefore a measurement data get some errors. - GSM feature, which effect to this activity, is to be disable such as hopping, DL Power control, DTX etc. 1.3 Definitions The model is stated in this document is based on the standard model supplier with Asset called Okumura-Hata model as below Path loss = k1 + k2log(d) + k3(Hms) + k4log(Hms) + k5log(Heff) + k6log(Heff)log(d) + k7(diffn) + C_loss Where: d Distance from the base station to the mobile station (km). Hms Height of the mobile station above ground (m). This figure may be specified either globally or for individual clutter categories. Heff Effective base station antenna height (m). diffn Diffraction loss calculated using either Epstein, Peterson, Deygout or Bullington Equivalent knife edge methods. k1 and k2 Intercept and Slope. These factors correspond to a constant offset (in dBm) and a multiplying factor for the log of the distance between the base station and mobile. k3 Mobile Antenna Height Factor. Correction factor used to take into account the effective mobile antenna height. k4 Okumura-Hata multiplying factor for Hms. k5 Effective Antenna Height Gain. This is the multiplying factor for the log of the effective antenna height.
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Company confidential k6 Log (Heff)Log(d). This is the Okumura-Hata type multiplying factor for log(Heff)log(d). k7 Diffraction. This is a multiplying factor for diffraction calculations. A choice of diffraction methods is available. C_loss Clutter specifications such as heights and separation are also taken into account in the calculation process.
2. MODEL PARAMETER TUNING PROCESS A suggested process of work for tuning a model is presented in the following flow chart:
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Company confidential Area and site selection Area and site survey Drive test with TEMS Post processing Prediction Change parameter
Comparison
Result Ok? Calibration
No
Yes Global Apply in Asset
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3. AREA AND SITE SELECTION This activity works on Asset planning tool. - Select area with representative in each clutter type with enough roads for collecting measurements. - Select an existing site and sector to completely cover in each clutter type. The antenna height should be 3-5 m above the clutter height. - Antenna tilt should be lower than 4 degree depend on vertical half power bandwidth because antenna radiated pattern can be invalid out of half power bandwidth. - Select a suitable measurement route. It is important to select the test routes within a clutter as much as it is possible as enough bins must be collected in each drive route and measurement. The measurement should be within a half power bandwidth of antenna horizontal pattern and more than 300 meter away from testing site and avoid a potential obstacle. - It should be avoid a hilly terrain where it can be provided improper measurements. - In region with seasonal of leaves, only take measurements if vegetation is in leaf. (Worst case)
4. AREA AND SITE SURVEY To ensure a testing site, site survey activity is need to check and confirm following; - Check whether clutter in each selected area is match with actual area or not. The clutter type in actual selected area must be same with clutter in the Asset otherwise a selected area must be changed to new one. - Check whether RF and antenna configuration in actual site. See RF data inspection list form as Appendix - Antenna type - Azimuth - Tilt - Feeder type and length - Combiner type and etc Page 8 of 18
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Company confidential After site survey finished, RF data in each testing sector has to be updated in the Asset database.
5. DRIVE TEST WITH TEMS A very detail drive test of the coverage area of each cell is required to provide sufficient data to accurately tune the clutter offsets. 5.1 Get ready to drive test It is important that the access roads to be within one clutter as much as possible. Ideally, every road should be driven but this is not always possible. There must be two people dedicated for drive testing; one driver and one responsible for collection of the data. It is important that the driver understands the way model tuning is carried out and how the routes should be driven. Before drive test, ensure that all of configuration must not be changed and GSM feature, which effect to this activity, is to be disable such as DL power control, hopping, DTX and so on. 5.2 TEMS configuration In testing area of high C-I or low interference, TEMS is to be locked onto the cell. TEMS should be locked onto that ARFCN on BCCH and disable handover. In testing area of low C-I or high interference where can not be collected enough measurements because of many call drop, it is to be retuned a co and adjacent channel or alternatively co and adjacent channel are to be barred or blocked. After that, TEMS is to be locked onto that ARFCN on BCCH and disable handover. When surveying the site, the call must be in dedicated mode. 5.3 Drive test It should not be driven closer than 300 meter to the site. It is very important that the routes are driven until the signal strength or quality is so poor that the call almost drops. By this way, it is possible to “see” how far the signal strength propagates. By obtaining a very detail drive test and determining how far the signal propagates, essential information for tuning the clutter offsets is gathered. Tuning a model is time consuming and the more clutters that need to be measured and tuned at least 400 samples to be collected in each clutter. Therefore it is good to have a sufficient number of clutters. It should be driven within a half power bandwidth of horizontal antenna power pattern where Page 9 of 18
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Company confidential is valid and be avoid a potential obstacle such as big hill and avoid LOS to site so that signal measurements can pass through a clutter which can give us a clutter loss. Check and see that the drive test log files are stored and not lost.
6. POST PROCESSING Creating site configuration as Signia CW Data (*.hd) format as explained as detail as below DATA_FILENAME (To open a data file *.DAT) SITE_ID SITE_NAME SITE_GRHEIGHT (Meter) SITE_LONGITUDE (Decimal) SITE_LATITUDE (Decimal) SITE_TYPE (Directional or Omni) TX_AZIMUTH (Degree) TX_TILT (Degree) TX_HEIGHT (Meter) TX_POWER (EIRP in dBm) ANTENNA_TYPE (It is to be contained in the Asset database) FEEDER_TYPE (It is to be contained in the Asset database) FEEDER_LENGTH (Meter) CONNECTOR_LOSS (dB) FREQUENCY (MHz) OPERATOR (Asiacell) COMMENTS DATE_START TIME_START DATE_END TIME_END A sample of Signia CW Data (*.hd) can be seen in Appendix. Then log file must be modified into *.DAT format as explained more detail as below Page 10 of 18
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Company confidential Longitude Latitude Rxlev Start 45.428513 35.553211 -61 45.428513 35.553211 -61 Finish After that, It should be eliminated a data which is the same data. Inspect the measurement data to verify its validity and filter out any erroneous data such as LOS data. Ensure that sufficient data points are available for each clutter class. In most Situations it is desirable for the data to be evenly distributed with respect to log (distance) from the site, clutter classes and with transmitter antenna being placed in typical locations.
7. CALIBRATION 7.1 Preparing calibration Before calibration, the RF and antenna configuration should be updated according to the information gathered during the site was surveyed. Use the same signal strength legends as those used in the drive test tool. Adding 900 MHz propagation model with standard macro1 as standard parameter as following Mobile Rx height 1.5 Earth Radius 8493 k1 150.6 k2 44.9 k1 (near) 0.00 k2 (near) 0.00 k3 -2.55 d < 0.00 k4 0.00 k5 -13.82 k6 -6.55 k7 0.7 Effective Antenna Height (Heff) algorithm Relative Diffraction Loss algorithm Epstein Peterson Page 11 of 18
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Company confidential Merge knife edges closer Dual slope Clutter parameters Use clutter heights Use clutter separations Use mobile heights
0.00 No N/A No No No
Loading the survey files, it must be set the map resolution and also select a prediction model. Delete measurements closer than 300m from the test transmitter – these will most likely be LOS or affected by reflections. Check Line of data and choose exclude bins outside the horizontal beamwidth. Filter out very high and very low signal measurements by setting remove measurements > -45 dBm and < -105 dBm which is recommended. Analyzing the measurement data, it can be shown a statistical analysis to compare how accurate model is with real world data. In case of manual tuning, ensure model accuracy is an iterative process, so do not change more than one parameter at once. Producing Graphs of measurement Data, graphs of Received Level versus log (distance) and Error versus log (distance) with a regression line, with the colors shown representing the clutter codes in which the measurements fall. 7.2 Manual calibration This section describes the often laborious process by which it can be tuned (calibrate) models. Normally this process is carried out by a specialist and performed the initial recommended steps as a guide to tuning the Standard Macro cell model as steps; 1. Load one or more CW survey files and use the filtering to remove questionable data and get an unbiased data set. For example, filter out readings with a signal level below the noise floor or clutter types with too little data to be statistically meaningful. 2. Derive an estimate of Slope Value (k2) from a plot of the Received Level vs. the (distance) using the CW Measurement Graph facility. Then fine tune this value. 3. Adjust the k1 parameter to a value, which will lower the mean error to 0. When the analysis report shows a negative mean error, it means the propagation model is pessimistic when Page 12 of 18
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Company confidential compared to the measurement data by the reported value. In this case, it should be lower the k1 value by the reported amount. Where a positive value is reported, the opposite applies. 4. Diffraction effects (k7) occur only when there is no Line of Sight from the site to mobile. Therefore to determine the k7 parameter, filter the dataset to include only the non-LOS. As a rule of thumb if the mean error is lower than 0, decrease k7 otherwise increase it. Normally it should be not calibrated and set 0.7. 5. Readjust the k1 value if the reported mean in the analysis report has increased or decreased after the k7 change. 6. Adjust the k6 value. It is useful to view the graphs and the signal error plot on the Map View to identify trends with successive parameter changes. Normally it should be set -6.55. 7. Readjust the k1 value if the reported mean in the analysis report has increased or decreased after the k7 change. 9. Adjust each clutter offset in turn trying to get the mean error of that particular clutter to 0. 10. The goal is to achieve a model with zero mean error and smallest possible error standard deviation. A standard deviation of can be accepted with 6-8 dB and less than 6 is considered very good. Apply the best parameter in propagation model. 7.3 Automatic Model Tuning The model can be tuned (calibrate) using the automatic calibration utility as steps; 1. Ensure to Create and configure an appropriate propagation model 2. Start the process with some sensible defaults for the model parameters. Do not leave all the K parameters at zero. 3. Archive data before proceeding, if changes are required to a standard Macro cell model and wish to retain these changes before tuning model parameters. 4. Select survey data, and then specify the model to compare against and the map data resolution which is wanted to use. 5. Click Autotune. 6. In the Optimizer Parameters pane, select the criteria that define when the optimization will stop: Page 13 of 18
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Company confidential - To end calibration after a set number of optimization iterations, enter a value in the Max Iterations box. Recommend value is 1000. - To end calibration when the standard deviation is no longer improving by a certain amount between iterations, enter a value in the Conv Accuracy box. Recommend value is 0.01. The optimization will end when either of these conditions is met, whichever occurs first. 7. If we only want to tune certain parameters, select the Fix check boxes next to the parameters which are not wanted to tune. 8. When finished, the resulting tuned parameters and performance statistics are displayed. If they are satisfied with model parameter corrections they can be applied the tuned parameters to propagation model. If they are not satisfied with model parameter corrections, - Re-tune by repeating steps 6 to 8. - Make a parameter change manually and view its effect on the model performance. To do this, enter the new parameter value. 9. A standard deviation of can be accepted with 6-8 dB and less than 6 are considered very well. Apply the best parameter in propagation model. Apply the best parameter in propagation model.
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8. EQUIPMENT The model tuning in this document is required a equipment and tools as followings 1. Asset (Aircom’s prediction tools) 2. TEMS 3. GPS 4. Tilt meter 5. Compass 6. Digital camera 7. 50 meter - Measuring tape
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9. APPENDIX 9.1 RF data inspection list form
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