Joint Relay and Jammer Selection Improves the Physical Layer Security in the Face of CSI Feedback Delays

• Published in: IEEE transactions on vehicular technology Vol. 65; no. 8; pp. 6259 - 6274
• Main Authors: Wang, Lei, Cai, Yueming, Zou, Yulong, Yang, Weiwei, Hanzo, Lajos
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Delay; Delays; Effective secrecy throughput; Feedback; feedback delay; Jammers; Jamming; Links; Mathematical models; Outages; physical layer security (PLS); Relay; relay and jammer selection; Relays; Reliability; reliability and security; Security; Signal to noise ratio; Throughput
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2015.2478029

We enhance the physical layer security (PLS) of amplify-and-forward (AF) relaying networks with the aid of joint relay and jammer selection (JRJS), despite the deleterious effect of channel state information (CSI) feedback delays. Furthermore, we conceive a new outage-based characterization approach for the JRJS scheme. The traditional best relay selection (TBRS) is also considered as a benchmark. We first derive closed-form expressions of both the connection outage probability (COP) and the secrecy outage probability (SOP) for both the TBRS and JRJS schemes. Then, a reliable and secure connection probability (RSCP) is defined and analyzed for characterizing the effect of the correlation between the COP and the SOP introduced by the corporate source-relay link. The reliability-security ratio (RSR) is introduced for characterizing the relationship between the reliability and the security through asymptotic analysis. Moreover, the concept of effective secrecy throughput is defined as the product of the secrecy rate and of the RSCP for the sake of characterizing the overall efficiency of the system, as determined by the transmit SNR, the secrecy codeword rate, and the power sharing ratio between the relay and the jammer. The impact of the direct source-eavesdropper link and additional performance comparisons with respect to other related selection schemes are also included. Our numerical results show that the JRJS scheme outperforms the TBRS method both in terms of the RSCP and in terms of its effective secrecy throughput, but it is more sensitive to the feedback delays. Increasing the transmit signal-to-noise ratio (SNR) will not always improve the overall throughput. Moreover, the RSR results demonstrate that, upon reducing the CSI feedback delays, the reliability improves more substantially than the security degrades, implying an overall improvement in terms of the security-reliability tradeoff. Additionally, the secrecy throughput loss due to the second-hop feedback delay is more pronounced than that due to the first-hop one.