Space and path diversity: theoretical matched filter bound and comparison to diversity gain obtained with practical MLSE receivers

Performance of space diversity techniques is considered for transmissions in mobile radio environments. Optimal performances are derived for any multipath Rayleigh fading channel for Nth-order diversity whenever the signals delivered by the antennas are correlated or not. The proposed theoretical study, illustrated for 2PSK, is suitable for any other modulation schemes (constellation, symbol rate, filter shaping...) to evaluate optimal performance of existing or future digital systems including imperfect channel estimation on fast varying channels. Matched filter bound performance is compared to practical receivers behavior. Simulations have been carried out in the case of the GSM system for second order diversity considering two practical receiver structures based on MLSE (maximum-likelihood sequence-estimator). The theoretical results and simulations show that second order diversity can be used in practical to considerably improve the BER performance or to improve the link budget of the transmission.