MULTIPLE DIFFERENTIAL DETECTION WITH ADAPTIVE SEQUENCE ESTIMATION (MDD-ASE) - MOBILE RADIO TRANSMISSION PERFORMANCE IN FREQUENCY-SELECTIVE FADING ENVIRONMENT

This paper aims at the improvement of the transmission performance of the differential detection system in the mobile radio transmission cha nnel in a frequency selective environment. The multiple differential d etection with adaptive sequence estimation (MDD-ASE) is proposed, and the performance is analyzed by a computer simulation. In MDD-ASE, not only the differential detection by one-symbol delay but also the diffe rential detection by two- or more-symbol delays are applied. The soft decision is applied to the output of the multiple differential detecti on, and the symbol sequence is estimated by Viterbi algorithm (VA). Th e bit error rate (BER) performance is improved by the extended observa tion time by the multiple differential detection and the sequence esti mation. The number of states in VA and the processing complexity of th e adaptive algorithm increases exponentially with the extension of the observation time. Consequently, the following method is proposed: (i) the number of parameters to be estimated is reduced; and (ii) the seq uence candidates stored in each path of VA are fed back. In this paper , the configuration and operation of MDD-ASE are described first and t hen the transmission performance of the 40 kbit/s QPSK modulation syst em is presented. As a result of analysis for the static and the dynami c performances of ADD-MSE using one- and two-symbol differential detec tion, it is shown that the improvement effect is almost the same as in coherent detection DFE.