A Stable Joint Routing and Spectrum Scheduling Scheme for Cognitive Radio Ad Hoc Networks

In CRAHNs (Cognitive Radio Ad Hoc Networks), cognitive users coexist with primary users who have priority in accessing a set of licensed bands. Cognitive users can use those bands only when the primary users don´t occupied them. And also, these occupied bands should be vacated immediately as soon as corresponding primary users wake up. Therefore, the more frequently primary user changes its activities, the less stable spectrum availability the cognitive user has. This makes route stability become one of the most concerned problems in CRAHNs. Some works have considered such kind of stability, but the overall performance of the network hasn´t been taken into account when multiple cognitive user pairs (also called multi-sessions in the following) have routing requirements. Thus, in this paper, we investigate a joint routing and spectrum scheduling problem, in which multi-sessions exist, and the route stability is required. To solve this problem, a greedy strategy named Distributed Stability Algorithm (DSA) is proposed, which aims to maximize the route stability of the session, whose route stability is the minimal. The message complexity of our algorithm DSA is O((L+2)·T_max·κ). Here, κ represents the number of transmission pairs, L and T_max are both two constants. Numerical results have shown that in a 100-node networks, compared with SAMER, our scheme can increase the route stability by 48.5% on average.