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Entropy 2017, 19(10), 522;

Secure Communication for Two-Way Relay Networks with Imperfect CSI

School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China
Current address: No. 10, Xi Tu Cheng Road, Haidian District, Beijing 100876, China.
Author to whom correspondence should be addressed.
Received: 30 July 2017 / Revised: 24 September 2017 / Accepted: 26 September 2017 / Published: 29 September 2017
(This article belongs to the Special Issue Information-Theoretic Security)
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This paper considers a two-way relay network, where two legitimate users exchange messages through several cooperative relays in the presence of an eavesdropper, and the Channel State Information (CSI) of the eavesdropper is imperfectly known. The Amplify-and-Forward (AF) relay protocol is used. We design the relay beamforming weights to minimize the total relay transmit power, while requiring the Signal-to-Noise-Ratio (SNRs) of the legitimate users to be higher than the given thresholds and the achievable rate of the eavesdropper to be upper-bounded. Due to the imperfect CSI, a robust optimization problem is summarized. A novel iterative algorithm is proposed, where the line search technique is applied, and the feasibility is preserved during iterations. In each iteration, two Quadratically-Constrained Quadratic Programming (QCQP) subproblems and a one-dimensional subproblem are optimally solved. The optimality property of the robust optimization problem is analyzed. Simulation results show that the proposed algorithm performs very close to the non-robust model with perfect CSI, in terms of the obtained relay transmit power; it~achieves higher secrecy rate compared to the existing work. Numerically, the proposed algorithm converges very quickly, and more than 85% of the problems are solved optimally. View Full-Text
Keywords: physical layer security; amplify-and-forward two-way relay; imperfect CSI; robust optimization; line search technique physical layer security; amplify-and-forward two-way relay; imperfect CSI; robust optimization; line search technique

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Sun, C.; Liu, K.; Zheng, D.; Ai, W. Secure Communication for Two-Way Relay Networks with Imperfect CSI. Entropy 2017, 19, 522.

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