Joint design of spectrum sharing and routing with channel heterogeneity in cognitive radio networks

Cognitive radio technology solves the spectrum under-utilization problem by enabling the secondary users access the spectrum holes opportunistically. Therefore, how to efficiently share the spectrum holes among the secondary users is of interest. Previous studies on spectrum sharing focused on the formulations with homogeneous channels. The channel heterogeneity, which is a unique feature in cognitive radio networks, has been ignored. In this paper, we model the channel heterogeneity and present a cross-layer optimization framework which jointly considers the spectrum sharing and routing with the objective of maximizing the fairness ratio. Since the formulation is in the forms of mixed integer linear programming (MILP), which is generally a difficult problem, we develop a heuristic method by solving a relaxation of the original problem, followed by rounding and simple local optimization. Simulation results show that the heuristic approach performs very well, i.e., the solutions obtained by the heuristic approach are very close to the global optimum obtained via LINGO. To the best of our knowledge this is the first attempt to model the channel heterogeneity into the formulation of spectrum sharing in cognitive radio networks.