R2NC: robust inter-session network coding in lossy wireless networks

The robustness of inter-session network coding is still an open issue in lossy wireless networks. The traditional XOR based network coding cannot work well if the overhearing is unperfect. Especially, the coding node cannot know the overheard information in time. In this paper, we consider a robust network coding method, namely R²NC which uses random linear network coding to encode packets together in the inter-session level, to resist the unperfect overhearing problem. With this method, coding node can always know the solvability of coded packets without the knowledge of overheard information. We analyse the performance of R²NC method with both lossy links of output and overhearing in the classic X-topology model, and give a necessary condition for the existence of coding gain. Finally, we design an optimal coding algorithm and a relay selection algorithm for R²NC to achieve its maximal transmission efficiency. Through ns-2 simulations, we demonstrate that R²NC plays a good performance in terms of throughput, delay and overhead, and is robust against losses on output and overhearing links.