Subcarrier and Optimal Power Allocation for Cognitive Radio System with Hybird Spectrum Access Mechanism
A. Thilagam, R. Ganesh Babu · SSRN Electronic Journal · 2015
In this paper investigates the subcarrier and power allocation problem for an OFDMA-based multiuser cognitive radio (CR) system. In particular, for such a CR system, the total transmission rate of CR users is maximized for a given power budget while keeping the interference introduced to the primary-user (PU) receivers’ below given thresholds with a certain probability. As the optimal scheme can be highly complex, we also propose a low-complexity suboptimal subcarrier-and-power-allocation scheme. First, a suboptimal subcarrier algorithm is proposed that allocates subcarriers to CR users that not only increase the capacity, but also reduces the interference introduced to the primary user (PU) band. Further, for a given subcarrier allocation an optimal power loading algorithm is proposed that maximizes the capacity of CR users while keeping the interference introduced to the PU band and the total power below a threshold. The selected numerical results show that a significant gain in terms of total achievable transmission rate can be obtained over an USAM or an OSAM. The proposed optimal scheme can lead to an unfairness among CR users in sharing the total transmission rate; therefore, we also propose a suboptimal subcarrier-allocation scheme that can guarantee a certain level of fairness among CRusers.