Optimal Power Allocation for Multiple Access Channels in Cognitive Radio Networks

Cognitive radio (CR) has been proposed as a strategy to enhance the spectrum utilization efficiency. In a CR network, the secondary users (SUs) share the same radio spectrum with the primary user (PU) under the constraint that the interference from the SUs to PU is below a certain threshold. In this paper, we consider the single-input multiple-output multiple access channels (SIMO-MAC) for the secondary network, and study the optimal power allocation strategy for maximizing the weighted sum rate of the SIMO-MAC under interference constraints and peak transmit power constraints. Employing decoupling techniques, we develop an iterative algorithm to obtain optimal power allocation for maximizing weighted sum rate. Simulation results are presented to verify the effectiveness of the proposed algorithm.