Multiple differential detection with adaptive sequence estimation (MDD-ASE)–-mobile radio transmission performance in frequency selective fading environment

Abstract

This paper aims at the improvement of the transmission performance of the differential detection system in the mobile radio transmission channel in a frequency selective environment. The multiple differential detection 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 differential detection by two- or more-symbol delays are applied. The soft decision is applied to the output of the multiple differential detection, and the symbol sequence is estimated by Viterbi algorithm (VA). The bit error rate (BER) performance is improved by the extended observation time by the multiple differential detection and the sequence estimation. The number of states in VA and the processing complexity of the 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 sequence candidates stored in each path of VA are fed back. In this paper, the configuration and operation of MDD-ASE are described first and then the transmission performance of the 40 kbit/s QPSK modulation system is presented. As a result of analysis for the static and the dynamic performances of ADD-MSE using one- and two-symbol differential detection, it is shown that the improvement effect is almost the same as in coherent detection DFE.