Performance Analysis of Collaborative Hybrid-ARQ Incremental Redundancy Protocols Over Fading Channels

Future wireless communication systems are expected to rely heavily on spatial diversity for mitigation of fading impairments. In scenarios where practical constraints prevent the collocation of multiple antennas on a single user terminal, collaboration between single-antenna nodes becomes the only viable solution. Among cooperative schemes, collaborative ARQ transmission protocols, prescribing cooperation only upon erroneous decoding by the destination, emerge as an interesting solution in terms of achievable spectral efficiency. In this paper, an information theoretical approach is presented for assessing the performance of collaborative hybrid-ARQ protocol based on incremental redundancy. Upper and lower bounds for the expected number of retransmissions and the average throughput are derived in explicit form, for any number of relays. Numerical results are presented to supplement the analysis and give insight into the performance of the considered scheme