Spectrum-aware routing in discontinuous orthogonal frequency division multiplexing-based cognitive radio ad hoc networks

With the rapid requirement and development of the green ICT (Information and Communication Technology) technology, the demand for dynamically radio spectrum resources has significant attention. The low utilisation of licensed spectrum leads to the scarcity of the spectrum resource. The emerging cognitive radio (CR) systems become increasingly important in the wireless green communication. In cognitive radio ad hoc networks, unlicensed users (called secondary users, SUs) communicate with other CR users through an ad hoc connection on licensed spectrum bands, but spectrum bands may be unexpectedly preempted by licensed users (called primary users, PUs). The design of routing protocol for CR ad hoc network considers problems of the dynamic spectrum sensing, management, sharing and mobility caused by reappearance of PUs. In this paper, the authors developed a spectrum-aware routing protocol for discontinuous orthogonal frequency division multiplexing-based cognitive ad-hoc networks by using the concept of the minimum expected total transmission time. With the expected total transmission time of all possible paths, a route with the smallest expected total transmission time is constructed. Mathematical analysis and simulation result illustrate that the proposed routing protocol can significantly reduce the total transmission time and improve the throughput.