I Introduction
Recently, the rapid spread of wireless communication cause the lack of frequency resources. However it has been said that most of frequency resources in time and space domain are not utilized effectively. One of the reasons is the frequency allocation policy. In the traditional policy, due to the frequency allocation in a fixed manner, there are wireless systems being lacking frequency resource and not being lacking frequency resource simultaneously, namely, it can be said that the utilization of frequency resource is not effective under this policy.