Optimal Power Allocation for Cognitive Relay Systems under Interference and Power Costraints

Abstract

In Cognitive Radio (CR) networks, power control deals with the selection of suitable transmit power for CR users’ transmissions that achieves high spectrum efficiency by enabling CR users to reuse the PUs’ spectrum bands under the interference constraints imposed by PUs. Without consideration of the minimum signal-to-interference-and-noise ratio (SINR) and frequent information exchange, the SINR requirements of secondary users (SUs) and primary users (PUs) in cognitive radio networks cannot always be satisfied by common power control algorithms. In this paper, the objective is to maximize the sum utility of SUs subject to the interference constraints of PUs, the transmission power constraints of SUs, and the SINR constraint of each SU. Finding the largest set of secondary users (i.e., the system capacity) that can be supported in the system is hard to solve due to the non-convexity of the cardinality objective. To maximize the total utility of SUs, a method based on gravitational Search Algorithm (GSA) is presented for the optimal power allocation. Simulation results show that the presented algorithm converges to the optimal power level while the interference level is guaranteed to the primary network.