A Near-Transparent Cooperation Scheme in Cognitive Radio Networks

In studies of cooperation between primary users (PUs) and cognitive users (CUs), compared with non-transparent protocol, the applicability of transparent protocol to existing communication system is higher, while almost no changes are needed to the transmission protocol of primary system. But there are also some disadvantages in existing transparent protocol: 1) the throughput of cognitive relay (CRL) is significantly lower compared with non-transparent protocol; 2) retransmission on spectrum holes, proposed in traditional transparent protocol, may bring signification delay. In this work, based on retransmission of primary packets on retransmission slots configured by primary system, a near-transparent cooperation protocol between PUs and CU is proposed to mitigate the retransmission delay. According to this protocol, an optimal choosing scheme of primary links for CRL is proposed. Based on prediction of CRL´s available throughput in each primary link, we analyze and simulate the performance of this optimal choosing scheme in scenario with single CRL and multi primary links. Simulation and analysis show that the near-transparent cooperation scheme can make the retransmission delay relatively low and constant, and significantly improve the throughput of CRL.