On the performance of Random Linear Network Coding in relay networks

We compare the reliability performance gain of Random Linear Network Coding (RLNC) with Automatic Repeat Request (ARQ) for a wireless relay network taking into account overhead and complexity of feedback mechanism as well as overhead due to encoding vector embedded in packet header under RLNC. Our goal is not to propose a new ARQ or RLNC error control protocol, but rather to study the fundamental properties of ARQ and RLNC under condition of finite block sizes. We consider an Enhanced ARQ (ARQ-E) scheme that exploits sender side path diversity between the sender and the relays as well as a Single Path Routing (ARQ-SPR) scheme that uses a hop-by-hop ARQ protocol. The performance metric of interest is reliability gain, the expected number of channel uses per data bit received at the receiver. In the case of AWGN channels, we compare the reliability performance of these protocols with each other and observe the fact that RLNC provides limited performance gains.