CLIX: Network Coding and Cross Layer Information Exchange of Wireless Video

Network coding (NC) can be efficiently combined with the "physical layer broadcast" property of wireless mediums to facilitate mutual exchange of independent information. At the same time, experimental/theoretical analysis of wireless networks has shown the efficacy of cross-layer protocols that relay corrupted packets in bandwidth hungry video applications. The integration of NC-based information exchange and cross-layer (CL) protocols for wireless video is the primary theme of this work. A particular issue addressed in this paper is the impact of errors in a packet, on the performance of a network code. Thus, we identify the operating conditions under which NC, despite the presence of residue errors, is beneficial. Based on theoretical analysis and experiments using 802.11b wireless traces it is established that the combination of NC with relay of corrupted packets can perform better than (i) conventional schemes that drop all corrupted packets (ii) a scheme that deploys network coding only (iii) a scheme that only deploys a CL strategy that recovers information from corrupted packets. The proposed cross-layer exchange (CLIX) scheme significantly improves the performance of an H.264 based video codec for wireless networks.