Impact Of Asynchronism on Wireless Relay Channels

In this work, we investigate the effects of asynchronism arised by time delay between the source and relay transmissions over the wireless relay channel. We revise the maximum-a-posteriori (MAP) type detector designed for synchronous case and proposed a receiver for asynchronous relay channel. We also integrate source-relay cooperation with the low density parity check (LDPC) codes in decode and forward (DF) mode to enhance the system performance. The convergence threshold of the overall system is evaluated using extrinsic information transfer (EXIT) chart analysis. Also the performance of asynchronous system is compared with synchronous counterpart via Monte Carlo simulations for various level of delay time. Using the convergence behaviour and simulation results, it's demonstrated that that the proposed receiver can cope with asynchronized transmission over the ergodic fading relay channel.