Boundary Helps: Efficient Routing Protocol Using Directional Antennas in Cognitive Radio Networks

The unpredictable activities of primary users (PUs) make the channel availabilities in cognitive radio networks (CRNs) very unstable. The dynamic channel availabilities cause routing in CRNs to be more difficult than in traditional wireless networks. Specifically, when a source node needs to select a route to reach the destination, the "optimal" route during the route selection phase may not be reliable because of the sudden appearance of a PU, and thus, may not be optimal during the data transmission phase. In this paper, we propose a novel routing protocol based on the source routing in traditional wireless networks. We consider the angle dimension of CRNs by assuming that the directional antennas are equipped on every node. The directional antennas can facilitate the marking of boundary areas of primary users. We use the USRP/Gnu radio to show the sensing result differences of different directions at the boundary area of a primary user. For every optional route between a source node and a destination node, we can evaluate its reliability and other performance by evaluating the PU areas it passes through, and estimating the possible transmission rate of each link on this route. Based on these parameters, we propose an algorithm for route selection, considering both the reliability and delay. Our routing protocol only requires very limited piggyback information, compared to other routing protocols in CRNs. It is efficient and highly adaptable under the dynamic channel availabilities. We evaluate our approach through extensive simulations.