Adaptive equalization in TDMA mobile radio systems

Digital transmission on a mobile radio channel requires sophisticated adaptive reception techniques. Two classes of non-linear adaptive equalization structures are studied in the present paper: the Maximum Likelihood Sequence Estimation (MLSE) and the Decision Feedback Equalizer (DFE). A coherently detected GMSK modulation has been assumed, with a 300 kb/s bit rate in a TDMA frame structure. Simulation results are presented with different kinds of static or dynamic multipath patterns. The results show that acceptable performance around the threshold objective of BER = 1% can be achieved without excessive complexity with both schemes. A further benefit will be provided by the use of FEC coding not considered here. At this point a direct comparison between the two structures may not be fair, because optimization work has not yet been completed to put both of them in optimal operating conditions.