Performance comparison of multiple-symbol differential detection and optimum combining

The performance of multiple symbol differential detection (MSDD) over Rayleigh diversity channels and in the presence of cochannel interference is compared with that of optimum combining (OC). For this purpose, we derive the asymptotic expressions for the approximate upper bound of the bit error probability of MSDD for multiple phase shift keying modulations. Similar asymptotic expressions are derived for OC. These relatively simple expressions provide a clear insight into the performance of MSDD and OC. Through analysis and simulation results, we show that as the observation interval increases, the performance of MSDD approaches that of OC (with differential encoding).