Adaptive Broadcast Transmission in Distributed Two-Way Relaying Networks

In this paper we consider adaptive, distributed two-way relaying networks using physical-layer network coding (PLNC). In the multiple-access (MA) phase, two sources transmit simultaneously to multiple relays. Depending on the decoding success at the relays, adaptive transmission schemes are investigated to avoid error propagation in the broadcast (BC) phase employing distributed orthogonal space-time block codes (D-OSTBCs). Recently, adaptive schemes have been proposed, where only relays with correct estimates of the network coded message participate in the BC transmission. In this work, we extend the analysis by incorporating also the case, that some relays are able to detect only one source message and propose a corresponding modified adaptive transmission scheme. For performance evaluations we resort to a semi-analytical method in order to examine the outage behavior of the presented schemes. As demonstrated by link-level simulations, the proposed adaptive scheme outperforms the traditional scheme significantly, especially for asymmetric network topology.