Efficient Spectrum Sharing in Cognitive Radio Networks with Implicit Power Control

Cognitive radio technology solves the spectrum under- utilization problem by enabling the secondary users access the spectrum holes opportunistically. How to efficiently share the spectrum holes among the secondary users, therefore, is of interest. Previous studies on spectrum sharing either do not consider interference constraints or assume the links being unidirectional. For simplicity the power control is usually not jointly considered when modeling the spectrum sharing in most of the previous studies. In this paper, we present a cross-layer design by modeling the spectrum sharing and power control with the interference constraints. A binary integer linear programming (BILP) problem is formulated to determine which link will be established, which channel will be assigned to each established link and which power level each established link will use for transmission. Different from the previous work, we assume links being bidirectional because we believe the link level acknowledgements in an ad-hoc network are a must. Moreover, we propose an implicit power control approach, where the power level for each link is predefined and implicitly embedded in the formulation, which makes the problem formulation very simple. Numerical results show that the power control helps to reduce the interference and therefore significantly (up to 56.3% in the simulated scenario) improves the total spectrum utilization.