Broadcasting in multihop wireless networks: The case for multi-source network coding

Network Coding, in particular Random Linear Network Coding, has been extensively researched for communication in multihop wireless networks, such as MANETs. A key aspect of random linear network coding is the definition of generations, the set of native data packets that can be coded together. To keep the decoding complexity and packet latency low, generations are typically small. In addition, to simplify generation management, it is usually assumed that a generation only contains packets originating from the same source. For broadcast scenarios, we show via examples, analytically derived lower bounds, and protocol simulations that the latter restriction reduces the coding gains that are achievable. Allowing packets from different sources to be combined (i.e., coded together) can improve PDR, reduce packet latency, and further reduce the number of packet transmissions at the MAC layer. We also discuss the added complexity that results from having packets from different sources in a single generation and propose our solution, embedded in a RLNC broadcast protocol called ARLNCCF.