Study on Power Allocation of Cognitive OFDM Systems

Cognitive radio is an emerging technique to improve the spectrum utilization in future wireless communication systems. In this paper, we study the power allocation strategy of cognitive orthogonal frequency division multiplexing (OFDM) system, where both primary user and cognitive user have multiple channels to transmit. The mathematical optimization problem is first formulated, based on the interference temperature model. The object of problem is to maximize the capacity of cognitive user under the constraint of interference temperature at the primary receiver and peak power constraint at the cognitive transmitter. An optimal solution based on Lagrange multiplexer is proposed to solve the optimization problem. Three suboptimal solution, which requires less channel side information, are also presented for the purpose of comparison. Numerical simulation results of different algorithms are provided.