On the Delay Characteristics for Point-to-Point Links using Random Linear Network Coding with On-the-Fly Coding Capabilities

Video surveillance and similar real-time applications on wireless networks require increased reliability and high performance of the underlying transmission layer. Classical solutions, such as Reed-Solomon codes, increase the reliability, but typically have the negative side-effect of additional overall delays due to processing overheads. This paper describes the delay reduction achieved through online network coding approaches with a limit on the number of packets to be mixed before decoding and a systematic encoding structure. We use the inorder per packet delay as our key performance metric. This metric captures the elapsed time between (network) encoding RTP packets and completely decoding the packets in-order on the receiver side. Our solutions are implemented and evaluated on a point-to-point link between a Raspberry Pi device and a network (de)coding enabled software running on a regular PC. We find that our sliding window approach (more feedback) outperforms all other tested mechanisms in terms of per-+packet delay including the Reed-Solomon encoding employing the systematic approach, a random linear network coding approach, and our proposed on-the-fly network coding approach (which relies on less feedback).We show gains in order of magnitudes between our sliding window and the other approaches when we manage the redundancy transmission adaptively. This low per-packet delay and the inherent reliability of our schemes make these solutions particularly suitable for real-time multimedia delivery in contrast to other classical and network coding strategies.