Secure communications with untrusted relays: a multi-pair two-way relaying approach

• Published in: IET communications Vol. 12; no. 20; pp. 2552 - 2560
• Main Authors: Zhao, Tantan, Li, Guobing, Lv, Gangming, Zhang, Yizhen
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 20.12.2018
• Subjects: approximation theory; array signal processing; artificial noise injection; concave programming; convex programming; convex subproblems; cooperative beamforming; cooperative communication; iterative algorithm; iterative methods; legitimate source; legitimate user pairs; multipair legal users; multipair two‐way relaying; multiple noncolluding eavesdroppers; multiple untrusted relays; multiple user pairs; nonconvex problem; physical‐layer security; radio networks; relay networks (telecommunication); Research Article; secrecy sum‐rate maximisation; secure communications; secure transmission; semidefinite relaxation; Taylor series approximation; telecommunication security; wireless relay networks; telecommunication security; radio networks; iterative methods; multiple user pairs; artificial noise injection; legitimate source; semidefinite relaxation; wireless relay networks; Taylor series approximation; concave programming; secrecy sum-rate maximisation; relay networks (telecommunication); array signal processing; legitimate user pairs; approximation theory; multiple noncolluding eavesdroppers; convex programming; nonconvex problem; secure communications; secure transmission; physical-layer security; iterative algorithm; cooperative communication; multiple untrusted relays; convex subproblems; multipair two-way relaying; cooperative beamforming; multipair legal users
• ISSN: 1751-8628; 1751-8636; 1751-8636
• DOI: 10.1049/iet-com.2018.5640

Physical-layer security is usually ensured by the injection of artificial noise (AN) at the legitimate source or destination when relays are cooperative but untrusted. In this work, in order to avoid the power-consuming AN at the legitimate user pairs, the authors investigate multi-pair two-way relaying as a solution for secure transmission in wireless relay networks with untrusted relays. They formulate a generalised problem for the joint design of cooperative beamforming (CB) and AN at relays to maximise the secrecy sum-rate in wireless networks with multi-pair legal users, multiple untrusted relays as well as multiple non-colluding eavesdroppers. Further, they reformulate, approximate and relax the original non-convex problem into a sequence of convex sub-problems based on semi-definite relaxation (SDR) and Taylor series approximation. Particularly, for the reformulated problem they prove that the SDR is in fact tight, and hence propose an iterative algorithm for CB and AN design at the relays. In the simulations, they demonstrate the fast convergence and high achievable secrecy sum-rate of the proposed algorithm. Also, they simulate and discuss the impact of the number of user pairs on the secrecy sum-rate, and reveal the change of performance gain with the number of multiple user pairs.