Adaptive network coded cooperation (ANCC) for wireless relay networks: matching code-on-graph with network-on-graph

We consider user cooperation in a relay network that comprises a large collection of transmitters sending wireless data to a common receiver. A new framework exploiting the network coding technology, referred to as adaptive network coded cooperation (ANCC), is proposed to combat the lossy nature of wireless links and to adapt to the changing network topology. The central idea is to match network-on-graph, i.e. instantaneous network topologies described in graphs, with the well-known class of code-on-graph, i.e. low-density parity-check (LDPC) codes and LDPC-like codes. Both achievable rates and outage probabilities are evaluated for ANCC, and closed-form expressions are derived for the asymptotic case where the network size increases without bound. Compared with the existing schemes, ANCC significantly outperforms repetition-based schemes and performs on par with space-time coded cooperation (STCC), but obviates the need for stringent inter-user synchronization at the bit/baud level.