Hybrid channel assignment in multi-hop multi-radio cognitive ad hoc network

The existence of under-utilized spectrum and the congestion of certain spectrum give rise to development on cognitive radios as a promising technology to address these problems. However, the general precondition that secondary users should evacuate from the channel which primary users are willing to use, makes the cognitive ad hoc networks vulnerable and unstable since network partition may occur since the links affected by primary users may form a cut set of the network. In this paper, we address this problem through a hybrid channel assignment scheme, where channels are carefully assigned to each link to guarantee the connectivity and the capacity based on spanning trees. Since the optimal solution is NP-hard, we propose an effective approximation algorithm. Also, dynamic channel assignment is proposed to further improve the network performance.