Cooperative Incremental Redundancy Hybrid Automatic Repeat Request Strategies for Multi-Source Multi-Relay Wireless Networks

In this letter, we present several cooperative incremental redundancy hybrid automatic repeat request strategies for the slow-fading half-duplex time slotted multiple access multiple relay channel. At a given retransmission round, the proposed strategies main steps are: 1) the destination acknowledges the successful decoding of the sources via limited feedback control channels; 2) the relays inform the destination about the result of their own decoding via forward coordination control channels; 3) the destination schedules the re-transmission in order to minimize the common outage probability of the system with the overall goal to maximize the long-term aggregate throughput; and 4) the scheduled relay cooperates with a subset of the successfully decoded sources (implicitly or explicitly indicated by the destination) applying either distributed coding or joint network channel coding. The analytical derivation of the individual (per source) and common outage probability plays an essential role in the scheduling algorithm and the performance evaluation. Numerical results show that the proposed strategies with control channels significantly outperform the one without control channels even when the impact of the control overhead is taken into account.