Channel assignment and routing with overhead reduction for cognitive radio-based wireless mesh networks

Cognitive radio (CR) technology has been attracted as a solution for the frequency scarcity problem in the wireless mesh network which operates on multiple frequency bands (or channels). In this paper, we consider the channel assignment and routing in CR-based wireless mesh networks (CRWMNs). In the CRWMN, CR nodes access the channels without disturbing primary users (PUs) which have a privilege to access the channels. When a PU is activated on one of the operating channels of the CRWMN, the network should update the channel assignment and routing to protect the transmission of the PU. This update, called joint channel assignment and routing update (JCAR-update), causes large signaling overhead in the CRWMN. To reduce such signaling overhead, we propose a two-step JCAR-update scheme. In the first step, each CR node tries to perform a simple recovery algorithm in a distributed way. The recovery algorithm is to reassign channels to affected links without exchanging control information. In the second step, only if the recovery fails, the CRWMN re-optimizes the channel assignment and routing. Simulation results show that the proposed scheme reduces the signaling overhead and supports stable operation in CRWMNs.