CW Testing

Md Joynal Abaden
+880 1830457155
joynalabaden@gmail.com

• There are 2 parts to the RF network design to meet the :-
• Capacity requirement
• Coverage requirement
• For the RF Coverage Design
RF
Coverag
e Design
Link
Budget
Propagation
Model
Digitized
DatabasesCW Drive
Testing
Customer
Requirements
Md Joynal Abaden +880 1830 457 155

• CW drive test can be used for the following purposes :-
• Propagation model tuning
• Assessment of the suitability of candidate sites, from both coverage
and interference aspect
• CW drive test process can be broken down to :-
Test
Preparation
Propagation
Test
Data
Processing
Equipment required
BTS antenna selection
Channel selection
Power setting
Drive route planning
Test site selection
Transmitter setup
Receiver setup
Drive test
Transmitter dismantle
Measurement averaging
Report generation

• The test equipment required for the CW drive testing :-
• Receiver with fast scanner
• Example : HP7475A, EXP2000 (LCC) etc.
• The receiver scanner rate should conform to the Lee Criteria of 36 to 50
sample per 40 wavelength
• CW Transmitter
• Example : Gator Transmitter (BVS), LMW Series Transmitter (CHASE),
TX-1500 (LCC) etc.
• Base Station test antenna
• DB806Y (Decibel-GSM900), 7640 (Jaybeam-GSM1800) etc.
• Accessories
• Including flexible coaxial cable/jumper, Power meter, extended power
cord, GPS, compass, altimeter

• Base Station Antenna Selection
• The selection depends on the purpose of the test
• For propagation model tuning, an omni-directional antenna is
preferred
• For candidate site testing or verification, the choice of antenna
depends on the type of BTS site that the test is trying to simulate.
• For Omni BTS :
• Omni antennas with similar vertical beamwidth
• For sectorised BTS
• Utilising the same type of antenna is preferred
• Omni antenna can also be used, together with the special feature in
the post processing software like CMA (LCC) where different
antenna pattern can be masked on over the measurement data
from an omni antenna

• Test Site Selection
• For propagation model tuning, the test sites should be selected so
that :-
• They are distributed within the clutter under study
• The height of the test site should be representative or typical for
the specific clutter
• Preferably not in hilly areas
• For candidate site testing/verification, the actual candidate site
configuration (height, location) should be used.
• For proposed greenfield sites, a “cherry-picker” will be used.

• Frequency Channel Selection
• The necessary number of channels need to be identified from the
channels available
• With input from the customer
• The channels used should be free from occupation
• From the guard bands
• Other free channels according to the up-to-date frequency plan
• The channels selected will need to be verified by conducting a pre-
test drive
• It should always precede the actual CW drive test to verify the
exact free frequency to be used
• It should cover the same route of the actual propagation test
• A field strength plot is generated on the collected data to confirm
the channel suitability

• Transmit Power Setting
• For propagation model tuning, the maximum transmit power
is used
• For candidate site testing, the transmit power of the test
transmitter is determined using the actual BTS link budget to
simulate the coverage
• On sites with existing antenna system, it is recommended
that the transmit power to be reduced to avoid interference or
inter-modulation to other networks.
• The amount of reduction is subject to the possibility if
separating the test antenna from the existing antennas

• Drive Route Determination
• The drive route of the data collection is planned prior to the drive test
using a detail road map
• Eliminate duplicate route to reduce the testing time
• For propagation model tuning, each clutter is tested individually and the
drive route for each test site is planned to map the clutter under-study for
the respective sites.
• It is important to collect a statistically significant amount of data, typically a
minimum of 300 to 400 data points are required for each clutter category
• The data should be evenly distributed with respect to distance from the
transmitter
• In practice, the actual drive route will be modified according to the latest
development which was not shown on the map. The actual drive route
taken should be marked on a map for record purposes.

• Transmitter Equipment Setup
• Test antenna location
• Free from any nearby obstacle, to ensure free propagation in both
horizontal and vertical dimension
• For sites with existing antennas, precaution should be taken to avoid
possible interference and/or inter-modulation
• Transmitter installation
• A complete set of 360º photographs of the test location (at the test height)
and the antenna setup should be taken for record

• Scanning Receiver Setup - HP 7475A Receiver Example
HP 7475A Receiver

• Scanning Receiver Setup
• The scanning rate of the receiver should always be set to allow at least 36
sample per 40 wavelength to average out the Rayleigh Fading effect.
• For example: scanning rate = 100 sample/s
• test frequency = 1800 MHz
• therefore, to achieve 36 sample/40 wavelength, the max. speed
is =
•
• It is recommended that :-
• Beside scanning the test channel, the neighbouring cells is also
monitored. This information can be used to check the coverage overlap
and potential interference
• Check the field strength reading close to the test antenna before starting
the test, it should approach the scanning receiver saturation
hkmsm
36/100
0.166740
/67.66/52.18 


• Drive Test
• Initiate a file to record the measurement with an agreed naming
convention
• Maintain the drive test vehicle speed according to the pre-set
scanning rate
• Follow the pre-plan drive route as closely as possible
• Insert marker wherever necessary during the test to indicate special
locations such as perceived hot spot, potential interferer etc.
• Monitor the GPS signal and field strength level throughout the test,
any extraordinary reading should be inspected before resuming the
test.
• Dismantling Equipment
• It is recommended to re-confirm the transmit power (as the pre-set
value) before dismantling the transmitter setup

• Data Averaging
• This can be done during the drive testing or during the data
processing stage, depending on the scanner receiver and the
associated post-processing software
• The bin size of the distance averaging depends on the size of the
human made structure in the test environment
• Report Generation
• For propagation model tuning, the measurement data is exported into
the planning tool (e.g. Asset)
• Plots can also be generated using the processing tool or using
MapInfo
• During the export of the measurement data, it is important to take
care of the coordinate system used, a conversion is necessary if
different coordinate systems are used.

• Standard Macrocell Model for Asset
• Lp (dB) = K1 + K2 log(d) + K3 Hm + K4 log(Hm) + K5 log(Heff)
• + K6 log(Heff) log(d) + K7 Diffraction + Clutter
factor
• where Lp, Diffraction, Clutter factor are in dB
• d, Hm, Heff are in m
• It is based on the Okumura-Hata empirical model, with a number of additional
features to enhance its flexibility
• Known to be valid for frequencies from 150MHz to 2GHz
• Applies in condition :-
• Base station height : 30 - 200 m
• Mobile height : 1 - 10 m
• Distance : 1 - 20 km
• An optional second intercept and slope (K1, K2) for the creation of a two-
piece model with the slope changing at the specified breakpoint distance.

CW Testing

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