Interference cancellation based transmission strategy using primary ARQ for cooperative CRNs

Aiming at efficient utilizing the licensed spectrum, in this paper, we develop an interference cancellation based transmission strategy (ICTS) for the cooperative cognitive radio networks (CRN) which will take advantage of the opportunities that arise during the primary automatic repeat requests (ARQ) and cancel the primary interference in both the primary initial transmission and retransmission slots. Simultaneously, the secondary system will cooperate with the primary system by supporting its outage quality-of-service (QoS) requirement to speedup the primary transmission and acquire more interference-free spectrum opportunities. Specifically, in the primary initial transmission slot, the secondary users (SU) will transmit in the underlay mode. In addition, SUs try to decode the primary signal to cancel the primary interference and overhear the primary ARQ signal. In the retransmission slot, SUs can cancel the primary interference directly when the primary signal is successfully decoded in the initial slot or utilize the primary information redundancy to cancel the interference. With statistical channel state information (CSI), SUs can calculate their interference cancellation probabilities in both slots and derive their average transmission rate. To maximize SUs' average transmission rate while meeting PUs outage QoS requirement, we formulate the optimization problem and efficiently allocate SUs transmit power. The closed-form expressions of the average transmission rates for both PUs and SUs are derived. Furthermore, SUs' upper bound symbol error probability (SEP) and PUs' SEP are derived. Simulation results demonstrate the performance superiority of our developed ICTS over conventional ARQ-based transmission strategies in terms of SUs' average throughput and PUs' outage probability and SEP.