INCP: Practical Wireless Network Coding for Multiple Unicast Sessions

Abstract

In this paper, we propose INCP, inter-flow network coding protocol, for wireless mesh networks. INCP is designed with the concept of Layered Approach. It acts as a distinct layer above the MAC and has close cooperation with IP layer. INCP exploits the opportunities of network coding through multiple unicast sessions to decrease the number of transmissions, thereby increasing the aggregated throughput. Unlike most prior work that is mainly theoretical, INCP addresses the practical issues of network coding such as impact of lossy links, enabling/disabling RTS/CTS mechanism, packet size and its variation. We consider a retransmission mechanism to ensure a reliable broadcasting. We analyze the cost of this approach by providing a theoretical formulation for the amount of required bandwidth for successful broadcasting a coded packet to n neighbors. Further, we examine the coding gain for lossy networks by considering the ETX metric for routing in addition to traditionally shortest-path metric. The results, implemented in ns-3, show that not only INCP increases network throughput, but also improves the fairness of the IEEE 802.11 MAC. Moreover, the gain for real MAC is greater than the theoretical gain in most cases. The performance gain of INCP reaches up to several folds depending on the traffic model and congestion level.