Reduced complexity maximum likelihood detection for DAPSK based relay communication systems

We propose a reduced complexity maximum likelihood detection technique for coded 16 level differentially encoded amplitude phase shift keying modulation in amplify-and-forward relaying system. This method eliminates the need for pilot symbols for channel estimation, equalization and there is no need for accurate phase tracking at the receiver which is particularly important in Relay aided cooperative system. This DAPSK based non-coherent differential detection method is spectrally efficient and more robust to non linear distortion. Our Simulation results demonstrate that the proposed method exhibits lower detection complexity and achieves approximately 3 dB gain at high SNR for a BER of 10-3 when compared to diversity combiner based detector and hard limiter based detection technique.