On the Packet Delay Characteristics for Serially-Connected Links using Random Linear Network Coding with and without Recoding

Low latency and high reliability are critical characteristics of many wireless use cases, such as real-time video surveillance. In a dense network, the best way to resolve such problems is by utilizing the fastest and most reliable connection to the destination, typically through relaying. Classical solutions, such as Reed-Solomon codes, increase the reliability, but also introduce additional coding delays at the relays. This paper describes the reduction of the packet delay achievable by network coding through a series of network nodes. Our metric captures the elapsed time between (network) encoding RTP frames and complete decoding of the packets on the receiver side while playing out the video recording contained in the payload. Our solutions are implemented and evaluated on serially connected Raspberry Pi devices and a network (de)coding enabled software running on a regular PC. We find that the recoding relays work at least as well as the systematic approach to network coding. In all cases network coding outperformed schemes employing classical Reed-Solomon codes. 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.