Sequential sensing based spectrum handoff in cognitive radio networks with multiple users

Spectrum handoff occurs when the primary users appear in the licensed spectrum temporarily occupied by the secondary users and aims to help the secondary users to vacate the spectrum rapidly and to resume transmission on new selected available channels. However, a spectrum handoff policy that comprehensively considers spectrum sensing, target channel selection as well as spectrum estimation has yet to be developed. In this paper we present a sequential sensing based spectrum handoff policy for multiple-user cognitive radio networks. First, we select the appropriate candidate channels for each secondary user, then their associated optimal sensing order together with the best target handoff channel is determined through sequential sensing based on Dynamic Programming (DP). Note that many spectrum handoff will occur during one secondary user transmission and our objective is to minimize the total number of spectrum handoff. The sequential sensing based spectrum handoff policy is evaluated through a comprehensive simulation study. The results reveal significant improvements in the system performance by reducing the number of spectrum handoff over conventional approaches. Moreover, our proposed DP method can significantly lower the computational complexity compared to exhaustive search and common DP (performing sequential sensing over all the channels in the system using Dynamic Programming).