Performance comparison of iteratively filtered and decoded MDD and PSAM systems with linear complexity

Joint channel estimation and decoding in a time-varying Rayleigh fading channel is considered. Knowing that the optimal design has an exponential complexity which hinders the practicability, a reduced complexity approach is proposed. This approach keeps the existing channel estimation and decoding schemes almost intact, while applying the turbo or iterative processing principle to enable information exchange between them. Thus the complexity is rendered linear; and the filter adaptability can be easily established. We apply this approach to two commonly used modulation schemes for noncoherent detection, namely, pilot symbol assisted modulation (PSAM) and differential modulation, with the intention to overcome certain disadvantages seen in their demodulation. It turns out that the performance is improved and the robustness is enhanced. In this paper, we first give the system descriptions of the two applications. Their performances are then simulated and compared with the existing systems. To reveal the tradeoffs in practical applications, the two new designs are also compared with each other in terms of throughput, complexity, performance, and robustness.