Cooperative HARQ protocols using semi-blind relays for underlay cognitive radio networks

In this paper, we evaluate the throughput of cooperative ARQ and HARQ I protocols in underlay cognitive radio networks using semi blind relays. Semi Blind Relays do not require to estimate the channel of the first hop, they use only some channel statistics. Relays help the secondary source to deliver its packet. Only relays that generate an interference to primary receiver lower than a predefined threshold will be activated. Three relay selection techniques are considered: opportunistic relaying, partial and reactive relay selection. Opportunistic relaying consists in selecting the relay that offers the highest end-to-end SNR. Partial relay selection consists in selecting the relay that offers the highest SNR of the first hop. Reactive relay selection consists in selecting the relay that offers the highest SNR of the second hop. This relay is selected among the active ones that generate an interference to primary receiver lower than a predefined threshold. To the best of our knowledge, there are no studies dealing with throughput evaluation of HARQ protocols for cognitive radio networks using opportunistic relaying, partial and reactive relay selection. Besides, this is the first paper to deal with HARQ protocols using semi blind relays. Previous studies dealt with outage, bit and symbol error probabilities evaluation for cognitive radio networks.