Exploiting cross-layer packet overhearing for opportunistic distributed STC in wireless relay networks

In this paper we propose a distributed Alamouti-based space-time code (STC) where opportunistic listening of packets from independent sources is exploited. Relays overhear broadcasted packets from multiple sources and acknowledge them dynamically. Acknowledgments are also overheard, allowing thus the relays to know the received packets at their neighbors. At each relay, the overheard data packets are multiplexed for generating in a distributed fashion the Alamouti STC that is broadcasted by the relays. Depending on the overheard packets the two relays may use dynamically the aforementioned multiplexed Alamouti STC scheme, or classic decode-and-forward (DF), or exploit transmit diversity with decode and joint forward (DJF). We perform extensive Monte Carlo simulations for testing the proposed protocol and the Alamouti-based STC under different channel conditions in the studied network topology.