Optimum diversity combining with finite-tap decision feedback equalization in digital cellular mobile radio

This paper analyzes the performance of space diversity structures combined with finite-tap decision-feedback equalization technique in a mobile radio environment with QAM transmission and frequency-selective fading. Two optimum diversity structures, combining-diversity and selection-diversity, are considered in our analysis. By analytic techniques and simulation, we show that for the same number of taps the improvement is always greater with combining-diversity structure. The combining-diversity with a certain finite number of taps can outperform the selection-diversity with infinite taps. The numbers of taps to approach optimum performance (infinite-tap bound) in outage for different mobile environments are also determined. The decision-feedback equalizer not only provides better performance than the linear equalizer, but also needs a smaller number of taps to approach the optimum performance, especially in the combining diversity system or in the severe time-dispersion environment.