System Feature Overview 11
68007024085 April 2011
2.1.3.2 Predicting Digital Audio Coverage
Predicting coverage for a radio site can be complicated. There are many factors that affect RF
performance prediction, and generally, the more factors that can be considered, the more accurate
the prediction of coverage. Perhaps the most influential factor is the selection of the RF
propagation model and/or RF prediction software tools.
Coverage prediction techniques for analog and digital systems generally follow the same basic
procedures, and require similar sets of input factors. Therefore, if the site’s analog coverage
footprint is already known, it is easier to plan the site’s digital coverage footprint. This approach
allows the system designer to use their existing analog site coverage prediction techniques,
whether simple or complex, and then translate the results of the analog coverage prediction to
predict digital coverage.
Delivered Audio Quality (DAQ) is a method to quantify audio quality. It is a measure of the
intelligibility and quality of voice transported through a communications system, as defined in TIA
TSB-88. DAQ reports audio quality on a 5 point scale, with a DAQ rating of 3 considered as the
minimal acceptable level of audio quality for public safety applications. The definition of DAQ 3 is
“Speech understandable with slight effort and occasional repetition required due to Noise/
Distortion.”.
When comparing an analog site and a MOTOTRBO site, the relative regions of coverage offering
comparable audio quality are illustrated in the figure below.
For a DAQ 3 audio quality, MOTOTRBO provides a greater usable range than analog, when all
other factors are considered equal (e.g. transmit power level, antenna height, receiver noise
figures, IF filter bandwidths, no audio processing – such as Hear Clear – on the analog radios,
terrain, antenna combining equipment, etc.).
Figure 2-6 Differences in Analog Coverage
Improving Audio Quality
Analog Digital
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