Performance of multi-relay collaborative hybrid-ARQ protocols over fading channels

According to collaborative hybrid automatic-repeat-request (ARQ) protocols, relay stations that have been able to decode the original message from previous transmissions, collaborate with the source in future retransmissions by jointly sending a space-time codeword. In this letter, analysis of the average number of retransmissions and throughput of collaborative hybrid-ARQ Type I (i.e., without memory) and chase combining (i.e., with memory) protocols is provided for any number of relays.