A low complexity protocol for relay channels employing rateless codes and acknowledgement

We provide a low complexity communication protocol for relay channels that can achieve a significant rate reliably even when a code word spans only finite number of fading blocks on average. Both full duplex and half duplex relay are considered. In the past, when a fixed rate code word spans a finite number of fading blocks, the capacity is zero. Therefore, a large amount of research has tried to reduce outage probability and increase throughput, such as the high signal-to-noise ratio (SNR) diversity-and-multiplexing-gain-tradeoff study of relay channels. Differently, the protocol in this paper achieves a significant information rate with asymptotically zero error probability (no outage) when the number of information bits represented by a code word increases to infinity. This performance is achieved by employing rateless codes and acknowledgements so that the destination obtains just enough mutual information to decode. This approach has the advantages that the protocol is not channel statistics dependent, has low complexity, is power efficient, has high performance, and can be easily generalized to other network communication settings.