SPARC: Superposition-Aided Rateless Coding in Wireless Relay Systems

Energy accumulation and information accumulation are two approaches to exploit multiple transmissions in wireless relay systems. There is a tradeoff between energy accumulation and information accumulation from an outage perspective, in which a packet is successfully received if the channel capacity exceeds the transmission rate. However, how to strike a balance between these two approaches is still unknown. In this paper, we propose a new rateless-coding-based transmission scheme in wireless relay systems, where the relay superposes two rateless-coded packets generated from different codebooks to strike a balance between energy accumulation and information accumulation. We analyze the average end-to-end throughput of the proposed scheme and formulate an optimization problem to find the optimal power allocation ratio. Simulation results will validate our analysis and show that, compared with pure energy accumulation and pure information accumulation, our proposed scheme can achieve substantial throughput gain.