Asynchronous Cooperative Spectrum Sensing in Multi-hop Cognitive Radio Networks

Previous cooperative sensing schemes require the cooperative Secondary Users (SUs) to behave in a synchronous way. This requires each SU to start cooperations at the same time by stopping their own transmissions. In multi-hop cognitive radio networks, it is very difficult to keep all SUs synchronized with others for sensing. In this paper, we propose an asynchronous cooperative sensing scheme for multi-hop cognitive radio networks in which each SU only provides its energy information in stead of ceasing its own transmission to perform the cooperative sensing. Each energy information is assigned an appropriate weight by considering the temporal and spatial diversities of each SU. We formulate the probabilities of detection and false alarm as optimization problems to find the optimal weight for every energy information. The achievable throughput has been derived. Numerical results show that the proposed scheme is able to achieve substantially higher throughput compared with the existing schemes.