Cooperative Communications with Multiple Sources and Relays in Ad-Hoc Networks

In this paper, we investigate the cooperative communication performance involving space-time block codes (STBC), channel coding, network code and turbo decoding in a wireless Ad-hoc network scenario where two relays are employed for communications from a number of senders to a common sink. To reduce bandwidth and achieve diversity gain, STBC is applied at the two relays. Based on whether network coding is adopted at the relays, two systems are specifically proposed and compared. One is a simply decode-and-forward (DF) system without network coding at the relays and conducts only one round of channel decoding after diversity operations at the receiver. The other system uses network coding at the relays and carries out turbo decoding at the receiver. We show through simulations that the second system has a fast turbo decoding convergence within two or three iterations and generally provides a better performance. However, in the cases where the direct links between the sources and the sink are weak, the first system with a simple decoding process actually can outperform. This result indicates that different channel conditions may require different system designs and a more complex one does not necessarily result in a better performance at all times.