Adaptive redundancy control with network coding in multi-hop wireless networks

Recent research shows that random linear network coding is adapted into current network systems to provide transmission reliability. In lossy environments, like wireless networks, a redundancy control is also needed to mitigate losses. Some implementations suggest adding a fixed amount of redundant packets per batch. This solution poses the risk of wasting bandwidth by over-redundancy or unsuccessful decoding due to packet insufficiency, dramatically degrading the performance. In this paper, we present the Adaptive Redundancy Control for Network Coding (ARC) that adds redundant packets dynamically to mitigate losses. First, ARC is based on the use of MAC acknowledgements as a feedback on the state of link quality. Second, instead of determining the correct number of redundant packets, we decide to find the suitable time to send the redundant packets to cover losses. We design the multi-batch coding scheme that continuously streams new packets while interpreting the received MAC acknowledgements as the feedback on the state of link quality. The state of link quality will be rechecked before every transmission to deduct if it is appropriate for pumping the redundant packets or transmitting the new data. We implemented and compared ARC with 802.11 and FRC -Fixed Redundancy Control in NS-2. Results show that ARC outperforms 802.11 and FRC.