A robust hybrid-ARQ protocol for relay networks

This thesis explores wireless relay networks using the hybrid-ARQ protocol. Relay networks exploit spatial diversity from 'redundant' nodes in contrast to the single path of classic networks. Thus they show superior performance in dealing with fading and interference. The hybrid-ARQ technique under the constraints of noncoherent orthogonal modulation and hard-decision decoding is the primary focus of the thesis. Information theoretic bounds on the performance for such a system are derived.; The extension of hybrid-ARQ from a point-to-point protocol to a broadcast-oriented relaying protocol called HARBINGER (hybrid-ARQ based intra-cluster geographic relaying) was presented in a 2005 paper by Zhao and Valenti. While prior work on this protocol had assumed Gaussian or modulation-constrained inputs, a practical coding technique based on Reed-Solomon codes is now analyzed. The suitability of the proposed protocol to the IEEE 802.15.4/Zigbee based networks using commodity off-the-shelf hardware is shown. Lastly, in order to study the fundamental problem of multi-user interference, the thesis also considers a two-source relay network. The performance of interference avoidance mechanisms such as time-hopping and orthogonal transmissions is explored.