Wireless Secure Communications via Cooperative Relaying and Jamming

Ling TANG  Hao CHEN  Jianhui WU  

IEICE TRANSACTIONS on Communications   Vol.E95-B    No.9    pp.2774-2784
Publication Date: 2012/09/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E95.B.2774
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Fundamental Theories for Communications
physical layer security,  cooperative relaying,  cooperative jamming,  beamforming,  robust beamforming,  

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We consider wireless secure communications between a source and a destination aided by a multi-antenna relay, in the presence of an eavesdropper. In particular, two cooperation schemes of the relay are explored: cooperative relaying (CR) and cooperative jamming (CJ). We first investigate the transmit weight optimization of CR and CJ, for both cases with and without the eavesdropper's channel state information (ECSI). Then, for the case with ECSI, we derive the conditions under which CR achieves a higher secrecy rate than CJ; for the case without ECSI, we compare the secrecy rates of CR and CJ in high transmit power regimes. Building on this, we propose a novel hybrid scheme in which the relay utilizes both CR and CJ, and study the power allocation of the relay between CR and CJ for maximizing the secrecy rate under individual power constraints. Further, we study the case with imperfect channel state information (CSI) for both CR and CJ. At last, extensive numerical results are provided.