Cw Survey Planning

7/27/2019 Cw Survey Planning

1/14

Copyright 1999 AIRCOM International LtdAll rights reserved. No part of this work, which is protected by copyright, may be reproduced

in any form or by any means - graphic, electronic or mechanical, including photocopying,

recording, taping or storage in an information retrieval system without the written permission

of the copyright owner.

CW Survey

Planning GuideXanthos N. Angelides

5th April 2000


2/14

CW Survey Planning Guide Page 1

5th April 2000

CONTENTS

1. INTRODUCTION... 2

2. DIGITAL MAP DATA... 2

2.1. Map Data Recommendations..... 2

3. CW MEASUREMENT DATA...... 2

3.1 Site Parameters and Visits.. 3

3.1.1 Site Selection.......... 3

3.1.2 Site Parameters where Verification is Required.. 33.1.3 Factors to Observe During Site Visits... 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... 73.4.1 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..... 10

APPENDIX B...... 11


3/14


5th April 2000

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 calibrationof 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 andmorphology 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.

2. DIGITAL MAP DATA

Mapping data is essential for the functionality of a prediction model. Furthermore its

accuracy will play a key role throughout the calibration process and will determine the

quality of the resulting propagation model. It is therefore important that mapping data is up-

to-date and various map data sets are available for the calibration of the different prediction

models.

2.1. Map Data Recommendations

Data sets must be derived from source material less than two years old.

A countrywide data set should be used for the rural and semi rural locations whereashigh-resolution maps should be used for the denser urban areas and city centres.

These should comprise of the features described in the ASSET user manual.

High resolution scanned maps would be of great advantage.


4/14


5th April 2000

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.

3.1Site Parameters and VisitsTo ensure validity of the calibration process it is essential that sites are selected carefully

and that various parameters required for the calibration process are verified.

Furthermore site visits before planning and conducting surveys are always useful since

through these possible delays and problems can be identified soon before the surveys

commence. The site morphology is also a major factor in determine the extent of surveys

regarding direction around the site.

3.1.1 Site Selection

Test sites measured should be representative of typical BTS sites, consideringissues such as the general environment and antenna height surrounding clutter

characteristics etc.

They should be spread around the area where the prediction model will be usedon so as to capture a wider range of DTM heights and locations thus ensuring a

valid model for all the area in hand.

Sites should have flat roofs and power outlets (possibly sites with BTS equipmenton the roof) so that test masts and equipment can be installed.

3.1.2 Site Parameters where Verification is Required

HeightThe heights of sites should be verified using an altimeter. Building heights are

usually provided by estate authorities and are usually inaccurate.

LocationThe site location should be verified in Longitude-Latitude format, which will be

used for the calibration. These coordinates must be calculated in the ellipsoid

format used by the mapping data in ASSET.

3.1.3 Factors to Observe During Site Visits

Area Around SiteKnowledge on the area surrounding a site is always beneficial when planning andconducting surveys. It is useful to know the clutter types in the near areas around


5/14


5th April 2000

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 SiteUrban sites are often installed on tall large terrace buildings with wide roof-topsthus 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 Issues3.2Survey PlanningOnce identifying any drive limitations through the site visits care must be taken in the

actual route planning. Various factors shape the actual drive and the validity and

accuracy of the CW data.

3.2.1 Factors for Planning Surveys

Drive tests must first be planned according to the limitations observed through thesite visits.

It is important to collect a statistically significant amount of data. The more dataavailable the more accurately the model can be calibrated.

The data should be evenly distributed with respect to distance from thetransmitter. Distance should also be taken into account on a per clutter type

basis. Using various locations of test sites this is practically implemented.

When planning drive routes it is of great importance to ensure that the drive goesthrough the clutter type in mind since consecutive roads may be classified as

different clutter types.

Using partially the same routes for different surveys is beneficial since the differentlocation of the test antenna will provide different data with respect to distance.

The extent of the survey is dictated on the amount of clutter types and requiredbins along with the actual purposes of the survey data. In cases where the data

collected will be used for analysing interference between sites survey may tend to

reach long distances away from the site and the actual route exceeding 100km.

There should be sufficient data collected within each clutter category to ensureaccurate modelling. Typically a minimum of 600 data points are required for each

clutter category.


6/14


5th April 2000

3.3 Equipment Parameters

For accuracy in the CW data it is required that the setups performance is verified and

factors contributing to variations in the CW data to be taken into account. Below thesetup of a typical test configuration for CW surveys is described with details on all the

elements and settings which need verification. It would be useful to note down the

performance of these elements before and after each survey. The template in Appendix

A may prove useful. It contains data fields which are required for the calibration

process.

3.3.1 Typical Test Transmitter Setup

Transmitter SettingsPower: 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 LossesThe 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 SettingsType: 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.

TRX

Simple

Omni

AntennaFeeder


7/14


5th April 2000

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

Antenna SettingsType: Typicallya 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 LossesThe 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 ReceiverIt is suggested that the receiver takes measurements using a narrow band filter.

This would enable measurements at lower signal levels and would decrease anypossibility of interference.

Positional DataTo 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 SoftwareData 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

Simple

Omni

AntennaFeeder

CP

DGPS

Measurement

Receiver


8/14


5th April 2000

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.

3.4 Collected CW Data

Before the collected data can be used appropriate filtering must be performed so as to

verify its validity and remove erroneous data. Inspecting the CW data using ASSET and

through the survey teams comment valuable feedback can be obtained which could be

used for future survey planning. Once the filtering process has been performed the

collected data must be binned and converted to the required format along with the

setup data for use within ASSET.

3.4.1 Data Filtering

It is essential to filter any invalid data that may cause anomalies in the calibration

process. Data which requires filtering can be identified through correct tagging of

measurements by the team conducting the surveys. Generally the following

circumstances would result to invalid data and therefore must be removed from the

measurement files.

Elevated RoadsData would be measured at a different height than desired and thus

would be invalid.

BlockingBlocking would cause abrupt drops in signal strength. Data would be

invalid since it does not represent the prediction model being calibrated.

This would occur when driving through tunnels, under bridges or when

driving alongside larger trucks or busses.

Dead Reckoning Drifting OffIn areas where satellite lock is lost for long periods the configuration uses

dead reckoning to ensure positional accuracy. Dead reckoning works

fine when driving over a steady bearing. If an abrupt turn is taken then

dead reckoning will drift off and positional data will be inaccurate. This

may result to measurements being assigned to different clutter types than

what they should be.

Consequences due to DGPS Offset EffectEven though it is strongly advised that DGPS is used for positional

accuracy it must be noted that this is accurate within 5-30m. The

consequence of this inaccuracy may result to measurements being

assigned to different clutter types and thus invalidity of measurements.

When filtering data this must be taken into account and there may be

circumstances where data will require shifting so as to coincide with the

correct mapping data.


9/14


5th April 2000


10/14


5th April 2000

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 problemsencountered thus minimising time delays during the drive.

The team conducting the survey team may point out roads that cannotbe 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 mapdata 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 FileIt 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.hdAn example of a Signia Header file can be found in Appendix B

Data FileIt 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


11/14


5th April 2000

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


12/14


13/14


5th April 2000

APPENDIX B

Signia Header File Format

SITE_ID 02FON

SITE_NAME 02FON

SITE_LONGITUDE 4.34491439

SITE_LATITUDE 50.84546273

SITE_TYPE MAST

TX_AZIMUTH 0

TX_TILT 0

TX_HEIGHT 26.86TX_POWER 38.4

ANTENNA_TYPE K005U0_USED

FEEDER_TYPE UNK NOWN

FEEDER_LENGTH 0

CONNECTOR_LOSS 0

FREQUENCY900

OPERATOR UNKNO WN

COMMENTS POWER WAS MEASURED AT OUTPUT OF CABLE

DATE_START 13/3/2000

TIME_START 12:30DATE_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 -52.3564.33999132 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


14/14


5th April 2000

4.33999129 50.84070299 -43.803

4.34027429 50.84070299 -42.132

4.34112328 50.84070300 -55.351

Cw Survey Planning

Documents

Transcript of Cw Survey Planning