  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
single- and 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 from M to (J+1)(M-1)+1 where J is the number of users helping
that user.
