Abstract:A novel cooperative Hybrid-ARQ protocol is presented on the basis of network coding. Two users communicate with the base station with the assistance of a relay node. Relay node responds the repeat request and processes two users’ incremental redundancy frames with physical-layer network coding, i.e. signal superposition modulation, before transmitting to the base station. Multi-user joint detection and joint soft decision decoding are adopted at the base station. Compared with traditional Hybrid-ARQ protocol, the proposed cooperative Hybrid-ARQ protocol can achieve better performance on flat Rayleigh fading channel, and approximates the performance of cooperative Hybrid-ARQ protocol without network coding with fewer hardware and bandwidth resources.