Coordinated Hybrid Automatic Repeat Request

We develop a coordinated hybrid automatic repeat request (HARQ) approach. With the proposed scheme, if a user message is correctly decoded in the first HARQ rounds, its spectrum is allocated to other users, to improve the network outage probability and the users´ fairness. The results, which are obtained for singleand multiple-antenna setups, demonstrate the efficiency of the proposed approach in different conditions. For instance, with a maximum of M retransmissions and single transmit/receive antennas, the diversity gain of a user increases fromMto(J + 1)(M - 1) + 1 where J is the number of users helping that user.