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Mathematical Problems in Engineering
Volume 2015, Article ID 587104, 9 pages
Research Article

Energy-Efficient Relay Selection Scheme for Physical Layer Security in Cognitive Radio Networks

State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications, Beijing 100876, China

Received 24 October 2014; Accepted 29 December 2014

Academic Editor: Elmetwally Elabbasy

Copyright © 2015 Li Jiang and Hui Tian. 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.


Security is a critical issue in cognitive radio (CR) relay networks. Most previous work concentrates on maximizing secrecy capacity (SC) as a criterion to guarantee the security requirements in CR relay networks. However, under the requirement of “green” radio communication, the energy consumption is largely ignored. This paper proposes a relay selection scheme which jointly considers the best relay selection and dynamic power allocation in order to maximize SC and to minimize energy consumption. Moreover, we consider finite-state Markov channels and residual relay energy in the relay selection and power allocation process. Specifically, the formulation of the proposed relay selection and power allocation scheme is based on the restless bandit problem, which is solved by the primal-dual index heuristic algorithm. Additionally, the obtained optimal relay selection policy has an indexability property that dramatically reduces the computational complexity. Numerical results are presented to show that our proposed scheme has the maximum SC and minimum energy consumption compared to the existing ones.