Baseband Performance of a Pilot Diversity System with Simulated Rayleigh Fading Signals and Co-Channel Interference

Using simulated Rayleigh-fading FM signals, the baseband performance of a diversity system that uses a separate pilot is studied. The effect of various RF/audio bandwidth expansion ratios is included. These results show an approach to a constant asymptotic baseband SNR for large expansion ratios, with diversity increasing this asymptote by 5 dB in the case of moderate to large interference and/or RF noise levels (9 to 15 dB below the carrier), to over 10 dB in the case of lower impairment levels (21 to 27 dB below the signal level). Assuming the usual hex-cell radio coverage plan, and a propagation law of the form
r^{-n}, n = 3
or 4, bandwidth expansion ratios of about three to six seem to yield the most efficient RF spectrum utilization in many practical situations. The number of required channel subsets (cells) is strongly influenced by the propagation law ranging from about 19 for
n = 3
, to about 7 for
n = 4
.