CW Testing
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The document discusses conducting a CW (continuous wave) drive test to help with RF network design. It involves collecting signal strength data along drive routes to aid in propagation modeling, site selection, and interference assessment. The summary describes the key steps in CW drive test preparation, execution, and data processing to generate reports for RF planning tools.
CW Testing
- 1. Md Joynal Abaden +880 1830457155 joynalabaden@gmail.com
- 2. • 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 joynalabaden@gmail.com
- 3. • 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 Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 4. • 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 Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 5. • 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 Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 6. • 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. Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 7. • 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 Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 8. • 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 Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 9. • 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. Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 10. • 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 Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 11. • Scanning Receiver Setup - HP 7475A Receiver Example HP 7475A Receiver Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 12. • 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 Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 13. • 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 Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 14. • 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. Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com
- 15. • 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. Md Joynal Abaden +880 1830 457 155 joynalabaden@gmail.com