Rate-Adaptive Link Quality Estimation for Coded Packet Networks

Coded packet networks allow for proactive injection of redundant packets to compensate for packet loss. Link metrics are usually based on the estimated transmission counter (ETX). This metric is used to determine the expected number of coded packets needed, but does not make guarantees for a specific decoding probability. In this paper we show that relying on the ETX metric leads to a surprisingly high probability that decoding is not possible. Based on this result, we derive a redundancy scheme to allow for an adjustable decoding probability. In a third step, we extend this scheme to also consider the reliability of link quality estimates themselves. We provide a numerically stable and hardware-accelerated implementation of our redundancy scheme, and compare all approaches in a simulated environment. Finally, we show the effect of the new redundancy scheme on different transport layer protocols in a wireless setup with random linear network coding.