Joint power/rate control and channel assignment in cognitive radio networks: A multi-level spectrum opportunity perspective

In a cognitive radio network (CRN), the spectrum opportunities should be effi-ciently utilized through careful coordination between cognitive radio (CR) users. In this paper, we formulate the coordinated channel access as a joint power/rate control and channel assignment optimization problem, with the objective of maximizing the sum-rate achieved by all CRs over all channels. The problem is formulated under a generalized multi-level spectrum opportunity framework, which reflects the microscopic spatial opportunity available for CRs. Both centralized and distributed approximate algorithms to the problem are developed. We prove that the distributed algorithm can achieve a certain fraction of the optimal throughput, while the centralized algorithm gives a tight upper bound on the optimal solution. We apply our algorithms to a spectrum-leasing application, and demonstrate the throughput gain of the multi-level spectrum opportunity structure over the conventional binary structure while taking the overhead into account. Numerical results verify the accuracy of our algorithms and the significant gain achieved by the multi-level framework.