CW Survey Planning Guide: Xanthos N. Angelides 5 April 2000
CW Survey Planning Guide: Xanthos N. Angelides 5 April 2000
CW Survey Planning Guide: Xanthos N. Angelides 5 April 2000
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CONTENTS
1. INTRODUCTION... 2
2. DIGITAL MAP DATA... 2 2.1. Map Data Recommendations ..... 2 3. CW MEASUREMENT DATA...... 3.1 Site Parameters and Visits.. 3.1.1 Site Selection.......... 3.1.2 Site Parameters where Verification is Required.. 3.1.3 Factors to Observe During Site Visits... 2 3 3 3 3
3.2 Survey Planning....... 4 3.2.1 Factors for Planning Surveys. 4 3.3 Equipment Parameters.... 5 3.3.1 Typical Test Transmitter Setup.... 5 3.3.2 Typical Receiver Setup....... 6 3.4 Collected CW Data... 7 3.4.1 Data Filtering...... 7 3.4.2 Survey Feedback..... 7 3.4.3 Data Binning.... 8 3.4.4 File Format for CW Survey Data.. 8 APPENDIX A..... APPENDIX B...... 10 11
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1. INTRODUCTION
This Application Note aims to provide guidance on the process of conducting Continuous Wave (CW) propagation surveys for the collection of actual data required for the calibration of the propagation model in ASSET. The calibration process is directly depended on the quality of the data used to conduct it. The two key inputs which dictate the results of a calibration process of any propagation model are: 1. The resolution accuracy and quality of the available digital terrain and morphology data. 2. The quality, statistical validity and accuracy of the Continuous Wave (CW) propagation survey data used to calibrate the model. These inputs must be verified before and during the CW survey process to ensure that errors are minimal. This Application Note examines these various inputs along with methods of planning and implementing CW surveys identifying issues which may affect the overall results.
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3. CW MEASUREMENT DATA
Apart from the actual measurements collected while conducting CW surveys various other parameters are required for the calibration. It is highly recommended that all parameters of the calibration configuration are verified throughout the data collection process. The main areas where attention and constant verification are required are identified as follows. Site Parameters Survey Planning Equipment Parameters Analysis on Collected CW Data The following subsections describe the various issues and suggestions for each of the above areas.
the site and the possibility to drive as close as possible to the site so as to collect data at distances under 200m which usually causes problems. Morphology of the Site Urban sites are often installed on tall large terrace buildings with wide roof-tops thus if a test antenna is installed on the building the first reflections of the signal will be blocked in areas near the building. The shadowing effect of the building can be minimised by installing the test antenna as close as possible to one edge of the building or at the tallest point of the building. The drives must then be planned in the direction of the building where the antenna was installed thus avoiding any blocking effects on the other side of the building. Site Access and Power Issues
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Feeder
Transmitter Settings Power: Constant stable power must be used throughout the surveys and it would be recommended that its value was verified before and after each survey. This power must be high enough so that the radiated signal would be sufficiently higher than the noise floor. Frequency: The test frequency should be selected so that no signals other than that of the test transmitter are measured. It would be wise to scan the air interface for any interfering signals that may cause problems to the data collection. Connector Losses The power at the input of the antenna is a required input to any calibration process. In simple setups like the one illustrated above the power can be measured by subtracting the loss through the cable from the transmitter power. It is therefore necessary to use a cable with known losses. In more sophisticated setups an NRT sensor can be connected between the antenna and the end of the feeder to monitor the power into the antenna. This is usually more accurate since the transmitter clock usually has a slight error upto 20%. Antenna Settings Type: In order to make measurements more accurate simple antennas should be used as it would limit the number and depth of sidelobes. Generally low gain simple omnidirectional antennas are suitable. It is necessary to know the antennas radiating pattern and to use it within ASSET during the calibration.
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Height: The antenna is usually set on a pump-up mast. The height of the mast must therefore be measured and added to the overall site height which will be used in the calibration. 3.3.2 Typical Receiver Setup
CP U
Antenna Settings Type: Typically a simple omnidirectional antennas with zero gain should be used are suitable. Height: The receiver antenna height should remain constant throughout the surveys at the typical height of mobile stations (human height). This in practice is set as the height of the roof of the measurement vehicle. Connector Losses The losses in the cables and connectors must be taken into account when measuring the signal strength at the receiver ends. At the operating frequency these losses should be measured prior the commencement of the surveys and then be added to the received signal strength. This way the collected data will represent signals at the input of the receiver antenna. Measurement Receiver It is suggested that the receiver takes measurements using a narrow band filter. This would enable measurements at lower signal levels and would decrease any possibility of interference. Positional Data To ensure positional accuracy the use of differential GPS (DGPS) is recommended. This may also need to be augmented with dead-reckoning to cope with areas where satellite lock is lost for long periods. Measurement Software Data will be collected with the use of a processor using a measurement software package usually provided by the measurement receiver vendor. Each measurement will be a set of coordinates calculated by the DGPS and a value for
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the received signal in dBms. The rate by which data is stored is dictated by the sampling rate achieved by the receiver. It is recommended that the samples should be distance triggered and that the speed of the mobile be directly proportional to the sampling rate.
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3.4.2 Survey Feedback Feedback from surveys may prove valuable when defining new drive routes. Drive routes can be planned taking into account any problems encountered thus minimising time delays during the drive. The team conducting the survey team may point out roads that cannot be driven through or one way streets, which can be taken into account so as to plan surveys which are easier to follow. 3.4.3 Data Binning Once all the erroneous data has been filtered out the data must be appropriately binned for its use within ASSET. Conversion of Coordinates Long/Lat format used in the map data. Interpolation of coordinates (useful when using distance triggering and GPS coordinates are not updated fast enough) Once the bins are taken all values below 110 dBm are removed (values below 110 are usually too close to the noise floor to be valid). Averaging of values over areas based upon the resolution of the map data used for the calibration. 3.4.4 File Format for CW Survey Data Once the data is binned then it must be stored in the required format for the calibration process. ASSET supports various file formats for CW measurement analysis. The most commonly used file format is the Signia file format and is recommended for use since it can easily be generated for all types of surveys. Each survey performed consists of two files. They are: Header File It consists of all detailed information about the test site and the survey. Typically Data about Site Location and Parameters Numerical data about equipment configuration Management Data and Comments The file is in ASCII text format and it is useful to name it in the following format for organisation purposes: SiteID_SurveyNo_Date.hd An example of a Signia Header file can be found in Appendix B Data File It contains any number of measurements where each line of data represents one measurement. The data for each measurement is split into three columns separated with a single space. The data in each column is as follows: Decimal Longitude for measurement Decimal Latitude for measurement Signal Strength Received
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The file is in ASCII text format and is named the same way as the corresponding header file with a different extension: SiteID_SurveyNo_Date.dat An example of a Signia Data file can be found in Appendix B
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APPENDIX A
CW S URVEY D ETAILS Site ID Start Date End Date TEST S ITE P ARAMETERS Site Coordinate (Decimal Long-Lat) Height Of Mast (m) Height of Building (m) Overall Antenna Height (m) Antenna Type Mast Type TRANSMITTER P ARAMETERS Date Time Power At Transmitter Output
SWR
Frequency
Time
Bandwidth
Frequency
C ABLE P ARAMETERS Length Transmitter-Antenna (dBm) Antenna-Receiver (dBm) S ETUP C OMMENTS /P ROBLEMS Date Time Details Loss Connector Losses
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APPENDIX B
Signia Header File Format SITE_ID 02FON SITE_NAME 02FON SITE_LONGITUDE 4.34491439 SITE_LATITUDE 50.84546273 SITE_TYPE M AST TX_AZIMUTH 0 TX_TILT 0 TX_HEIGHT 26.86 TX_POWER 38.4 ANTENNA_TYPE K005U0_USED FEEDER_TYPE UNKNOWN FEEDER_LENGTH 0 CONNECTOR_LOSS 0 FREQUENCY 900 OPERATOR UNKNOWN COMMENTS P OWER WAS MEASURED AT OUTPUT OF CABLE DATE_START 13/3/2000 TIME_START 12:30 DATE_END 14/3/2000 TIME_END 16:00
Signia Data File Format 4.33942533 50.83962315 -54.514 4.33970832 50.83962315 -53.273 4.33999132 50.83962316 -52.988 4.33942532 50.83980312 -52.356 4.33999132 50.83980313 -56.232 4.33942532 50.83998310 -44.772 4.33999131 50.83998310 -57.323 4.33942531 50.84016307 -47.866 4.33970831 50.84016307 -53.212 4.33999131 50.84016307 -55.332 4.33942531 50.84034304 -53.991 4.33970830 50.84034304 -45.953 4.33942530 50.84052301 -56.469 4.33970830 50.84052302 -49.795 4.33999130 50.84052302 -43.670
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