We enhance the physical-layer security (PLS) of amplify-and-forward relayingnetworks with the aid of joint relay and jammer selection (JRJS), despite thedeliterious effect of channel state information (CSI) feedback delays.Furthermore, we conceive a new outage-based characterization approach for theJRJS scheme. The traditional best relay selection (TBRS) is also considered asa benchmark. We first derive closed-form expressions of both the connectionoutage probability (COP) and of the secrecy outage probability (SOP) for boththe TBRS and JRJS schemes. Then, a reliable-and-secure connection probability(RSCP) is defined and analyzed for characterizing the effect of the correlationbetween the COP and SOP introduced by the corporate source-relay link. Thereliability-security ratio (RSR) is introduced for characterizing therelationship between the reliability and security through the asymptoticanalysis. Moreover, the concept of effective secrecy throughput is defined asthe product of the secrecy rate and of the RSCP for the sake of characterizingthe overall efficiency of the system, as determined by the transmit SNR,secrecy codeword rate and the power sharing ratio between the relay and jammer.The impact of the direct source-eavesdropper link and additional performancecomparisons with respect to other related selection schemes are furtherincluded. Our numerical results show that the JRJS scheme outperforms the TBRSmethod both in terms of the RSCP as well as in terms of its effective secrecythroughput, but it is more sensitive to the feedback delays. Increasing thetransmit SNR will not always improve the overall throughput. Moreover, the RSRresults demonstrate that upon reducing the CSI feedback delays, the reliabilityimproves more substantially than the security degrades, implying an overallimprovement in terms of the security-reliability tradeoff.
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