End-to-End HARQ in Cognitive Radio Networks

Cognitive radio networks (CRN) may greatly enhance the throughput based on a given bandwidth. CRN has a unique feature, consisting of uni-directional opportunistic wireless links, and packets may be cooperatively relayed from source node to destination node through one or multiple paths, while each path consists of multi-hop opportunistic wireless fading links. Effective end-to-end error control is therefore a must to complete transportation of packets in CRN, though not being touched in open literatures. Traditional ARQ cannot generally function over uni-directional opportunistic links. We consequently develop a novel hybrid ARQ based on amplify-and- forward cooperative relay of CRN to reach the purpose of end-to-end error control at session level. Multiple coded subpackets are sent through multiple paths, and the destination node decodes these received coded sub-packets from different paths. This HARQ for CRN works even missing some coded sub-packets. By the concept of outage, we also study allocation of coded sub-packets on multiple paths in an information theoretical view and develop a coding rate adaptation scheme for CRN such that end-to-end error control is possible.