Bit error probability of MSK modulation with switched diversity in a mobile-radio channel with two independently-fading paths

We investigate the bit error probability of an indoor mobile communications system (MSK modulation with differential detection) with RSSI-controlled and error-controlled switched antenna diversity. We model the mobile radio channel as a two-path Rayleigh fading channel; we sample in the middle between the two pulses. We derive analytical expressions for the error probabilities (BERs) for both diversity methods. We confirm our results with Monte Carlo simulations. For small delays, we show that the BER is proportional to the fourth power of the mean delay spread for both diversity methods, and that the low-cost RSSI-controlled diversity gives a BER that is only a factor 3 worse than error-controlled diversity but shows the same basic dependence on the delay spread. For typical indoor situations (delay spread equal to one-tenth of the bit length), we find that the BER is on the order of 10 ^-3 when using no diversity, 10^-5 for RSSI-controlled diversity, and 10^-6 for BER-controlled diversity