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International Journal of Antennas and Propagation
Volume 2015, Article ID 530632, 15 pages
Research Article

Joint Power Allocation at the Base Station and the Relay for Untrusted Relay Cooperation OFDMA Network

College of Communication Engineering, Chongqing University, Chongqing 400044, China

Received 13 October 2014; Revised 17 March 2015; Accepted 17 March 2015

Academic Editor: Francisco Falcone

Copyright © 2015 Weiheng Jiang and Wenjiang Feng. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The secure communication that multiple OFDMA-based cell-edge mobile stations (MS) can only transmit confidential messages to base station (BS) through an untrusted intermediate relay (UR) is discussed. Specifically, with the destination-based jamming (DBJ) scheme and fixed MS transmission power assumption, our focus is on the joint BS and US power allocation to maximize system sum secrecy rate. We first analyze the challenges in solving this problem. The result indicates that our nonconvex joint power allocation is equivalent to a joint MS access control and power allocation. Then, by problem relaxation and the alternating optimization approach, two suboptimal joint MS access control and power allocation algorithms are proposed. These algorithms alternatively solve the subproblem of joint BS and UR power allocation and the subproblem of MS selection until system sum secrecy rate is nonincreasing. In addition, the convergence and computational complexity of the proposed algorithms are analyzed. Finally, simulations results are presented to demonstrate the performance of our proposed algorithms.