Downlink Channel Assignment and Power Control for Cognitive Radio Networks Using Game Theory

We consider a cognitive radio network in which a set of base stations make opportunistic spectrum access to support cognitive radios within their cells. As the spectrum of interest is licensed to the operator of a primary network, channel assignment and power control must be carried out in the cognitive network so that no excessive interference is caused to users of the primary network. Given this constraint, we are interested in the downlink channel/power allocation problem, with the objective of maximizing the total number of supported CRs. Since the problem belongs to the class of NP-hard problems, it is desirable to model and analyze it using game theory. First, we formulate the problem as a non-cooperative game. For distributed power allocation, we use Iterative Water Filling algorithm. Numerical results show that the pure non-cooperative game may result in non-convergence or many undesirable Nash equilibria with few supported CRs. To enhance the performances Nash bargaining solution (NBS) is used. NBS requires the cooperation between BSs but still power allocation is done in a distributed manner using ITW.