A selective cooperative HARQ protocol based on link quality

Aiming at the poor performance of retransmission delay in single-relay cooperative Hybrid Automatic Repeat Request(HARQ) system,this paper investigates the characteristics of BER and delay on the fast fading channel,proposes a selective cooperative HARQ(SC-HARQ) scheme based on link quality for single relay systems.The scheme can choose the link to retransmit in light of link quality for the direct link and the relay link in the single-relay system.The SC-HARQ scheme needs to set a threshold of link quality,and then chooses the corresponding retransmission scheme according to SNR of transmission links,and minimum retransmission delay with appropriate transmission quality guarantee.Namely,when the direct link quality is great than the threshold,system will choose the direct link to retransmission;conversely,choose the relay link.Simulation results show that this scheme can effectively decrease retransmission delay and achieve better performance in terms of system average delay with respect to traditional cooperative HARQ scheme.