ARQ versus Rateless Coding: From a point of view of redundancy

Automatic Repeat reQuest (ARQ) and Rateless Coding (RC) are two major feedback-based error control schemes. However, due to the lack of common metrics for measuring the performance, ARQ and RC have not been systematically compared yet. In this paper, we establish a unified analytical framework based on two novel metrics, namely forward redundancy and feedback redundancy, and present a comparative study on ARQ and RC from the point of view of redundancy. In particular, we conduct a fair comparison of both schemes over point-to-point fading channels and broadcast fading channels. The comparison indicates that RC is capable of beating ARQ completely at low signal-to-noise ratios in broadcast communications. In other cases, neither of them could dominate the other. Therefore, we propose a selection method to determine which scheme to employ with given system parameters.