System Design and Testbed Implementation of Adaptive Coding Optimization in Lossy Networks

A fundamental challenge in wireless networks is handling packet loss due to dynamic noise, interference, and dynamic channel effects, especially when there is no per-packet acknowledgement due to additional delays and potential loss of feedback packets. We design and implement a packet coding optimization scheme applied at source node to enhance end-to end transmission reliability in a lossy multi-hop network. Each source node transmits a file of packets to its destination node in the network where the end-to-end packet acknowledgement is not readily available because of the possible error or delay effects over multiple hops. By simply retransmitting packets, a source node cannot guarantee innovative packet arrivals at the destination node. Thus, we design an optimization scheme for adaptive packet coding applied at the source node to avoid redundant packet traffic thereby significantly improving the throughput, even for the case of a single unicast session. This scheme does not require any knowledge of network topology and can seamlessly operate with any routing or network coding protocol used at the intermediate relay nodes. First, we discuss the throughput properties of coded transmissions and verify the feasibility of performance gains via simulations. Then, we provide high fidelity emulation test bed results with real radio transmissions over emulated channels to evaluate the throughput gains. Without relying on end-to-end acknowledgment for each packet, we show that the adaptive packet coding optimization scheme can achieve significantly higher throughput than the retransmission scheme in lossy networks with unicast traffic.