Optimal algorithm for Multi-hop relay selection based on cognitive radio

Relay selection, also called opportunistic relay, is capable of fast narrowing the search scope, finding the optimal relays and achieving a better cooperative transmission. With the continuous expansion of network capacity, the coverage area and the participating relays, it is unwise to traverse all the nodes to select the best relay. An optimal scheme based on cognitive wireless multi-hop relay selection has been proposed in this study, in which a threshold value is set for the signal-to-interference-plus-noise ratio (SINR). Only when the SINR exceeds the threshold can the node be selected as the relay node. Because of the random distribution and geographical universality of the relay, the candidate relays would better be limited within a particular area. Then a model based on stochastic geometry is established to rapidly find the relay which meets the demand near optimally, without needing of the global channel state information of the network in advance. The simulation results show that the optimized scheme can reduce the searching time and improve the performance of the secondary transmission. In addition, theoretical formula of the outage probability and channel data transmission rate has also been derived and verified its effectiveness through simulation.