DIFFERENTIALLY AMPLITUDE AND PHASE-ENCODED QAM FOR THE CORRELATED RAYLEIGH-FADING CHANNEL WITH DIVERSITY RECEPTION

This paper studies the differentially amplitude and phase-encoded (DAP E) quadrature amplitude modulation (QAM) transmission over correlated Rayleigh channels with diversity reception, Operating over two success ive received symbols, the optimum and an asymptotic maximum-likelihood (AML) differentially coherent receivers are developed and compared wi th a conventional switched diversity combining (SDC) grid receiver, It is shown that the AML and SDC grid receivers are much simpler in comp lexity than the optimum receiver in that no channel side information i s required in their realization, An exact expression of the bit-error probability (BEP) is obtained for the SDC grid receiver, Based on a un ion bound argument, a BEP upper bound for the AML receiver is also der ived and verified by simulation, Numerical results on 16- and 64-point constellations show that the AML receiver exhibits almost the optimum performance and the SDC grid receiver with a small level of diversity is nearly optimum. It is also shown by simulation that the convention al equal-gain diversity receiver performs almost optimumly for demodul ating a 16-point DAPE QAM signal.