Channel Estimation for Overlay Coding in Multibeam Satellite Systems

We investigate the effect of channel estimation inaccuracy in multibeam satellite system forward link, with dense frequency reuse, using our previously proposed overlay coding technique. We have shown overlay coding to be the capacity achieving multi user detection (MUD) technique, by transmitting over non-orthogonal channels. The overlay coding scheme is based on cooperation of transmitting beams by targeting one user terminal at a time. The jointly reception of data streams features multiple access channel (MAC), where both data will be recovered by devising successive interference cancellation (SIC). However, in case of channel estimation error, though it might result in slight errors at the beginning, the propagation of error through SIC causes huge loss of data frames and throughput degradation. So, we propose a strategy based on a back-off algorithm to mitigate the problem. Our simulation results show that significant drop in frame error rate (FER) can be achieved, and overlay coding can reach expected data throughput gain almost the same as the cases with perfect channel estimation.