Radio Resource Allocation in OFDMA Cognitive Radio Systems

Cognitive radio has been recently introduced to enhance spectrum efficiency, while orthogonal frequency division multiple access (OFDMA) as a multi-carrier technology is widely considered for future wireless communications. In this paper, we consider practical OFDMA cognitive radio operating environments at physical layer by a composite hypothesis test to identify channel status. Lloyd-Max Algorithm is used in channel identification function to cluster observed data and generate a threshold for hypothesis test. By incorporating such information from cognitive radio physical layer, we develop a novel three-step cross-layer optimization of OFDMA radio resource allocation, while keep fairness among users and maximization of total capacity in such time varying environment. The power, time slots and sub-carriers are jointly optimized by two separate optimal algorithms in three steps. Our results show that capacity of OFDMA can be maximized and fairness can also be maintained well by such a pioneer optimization in dynamic and time-varying communication environment.