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Performance Verification of LMR Systems
Using TIA TSB-88.3c Methodologies2011APCO Western Regional Conference, Ontario, CA
David Buchanan
This series of documents was prepared in response to requests from APCO, LMCC and the NCC
These organizations recognized that new technologies and the drive for more efficient use of spectrum required better methods for frequency coordination.
TSB-88 also covers:◦ Independent Methods of Performance Modeling◦ Propagation and Noise
TSB-88 History
Area Coverage Covered Area Reliability Delivered Audio Quality (DAQ) Mean and Median Signal Levels and other
ugly statistical terms Outdoor Coverage testing Developing a test methodology to verify
system performance
What We Will Cover
What Do We Mean by Coverage Boundary?
Example of a coverage Boundary
Yucaipa, CA
% of the Area? % of the Area with X% of Confidence What level of signal? Faded or not faded? What % of time Why do we need all these statistics? Unfortunately radio propagation is not
constant over time and area It can only be characterized using statistics
Define Coverage!
Start with signal level
Why don’t we decide on a method to define coverage!
Inferred Noise Floor -123 dBm
Static Threshold-116 dBm
Faded Threshold
-106 dBm
Higher value for Interference limited systems or Portable coverage
-94 dBm
We need to divide our coverage area into tiles to test for the signal level throughout the coverage area
Test Tiles
Estimate of proportions Tt = Z2pq/e2
Where:Tt = number of test tilesZ = Standard Deviate unit (confidence level
97% = 1.881)p = Service Area Reliability (95% = .95) q = 1-pe = Sampling error allowance (e =2% = .02)And Tt >= 100
So How many Tiles?
Tt = Z2pq/e2
Tt = 2.2362*.95*(1-.95)/.022 = 5942.236 = 99% confidence level as
recommended by TSB-88594>100 so Service area needs to be divided
into 594 equal area tilesAlso for outside tests Tile size ≥ 100λ x 100λ
but less than 2 km x 2 km
Example for Number of tiles
We now need to test each tile one time to determine the signal level
How do you test outdoors? You need to measure 50 subsamples to produce
a 90% confidence level that the measured value is within +/- 1 dB of the true value. Also the subsamples should be measured over 40 wavelengths. Use the median value of these measurements for each tile.
A tile passes if the measured value is >= to the CPC value (level from slide 7)
The “Greater Than” Test
To find out divide the number tiles that pass by the total number of tiles. Example: 594 total tiles and 580 passed = .976 or 97.6 %. If your criteria was 97% area coverage – the system passes. If not your vendor has some problems.
You should also do subjective voice checks for analog systems particularly for simulcast systems as they can show good levels but not be optimized in the overlap areas. For digital systems measure the bit error rate to check for voice quality.
Does My System Pass?
Use an automated system for the testing Don’t mix mobile and portable testing if the
service areas differ Not all tiles may be accessible for testing and
should be excluded Some tiles may be critical to have coverage
and those should be noted to the vendors before system design
There are methods for indoor coverage testing and mobile data system testing in the document
A Few Other Notes
Recommended