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With fixed number of available channels in the traditional wired networks and wireless ad hoc network, routing protocols are paying more attention on the establishment of network topology and the optimization of routing path selection. Although there are multi-channel multi-interface nodes in the wireless ad hoc networks, the set of each node's available channels is fixed, or even the same. With a fixed and static available channel set, the researchers can consider the MAC layer has already provided error-free data link for the up-layer applications. Therefore, it is not necessary to take the underlying link problems related to channel access into account during the routing protocol design. In cognitive radio networks, nodes achieve the dynamic access of available spectrum by sensing the spectrum hole. When the primary user appears in the authorized band, the secondary users must give up the occupied channel, thus resulting in the available channel set of the cognitive radio terminals changing with time and space location, and the available channel set of each node different from each other at the same time. The dynamic change of the available channel set brings about the dynamic change of physical link connectivity, thus making the routing based on it is also on highly dynamic. When one node has multiple wireless interfaces, the routing will become even more subtle. It is important to take the influence on the performance of routing protocol introduced by the spectrum allocation into account.