Jamming-and-Relaying Strategy for Non-linear Energy Scavenging Networks

Relay selection not only maintains but also improves the reliability of source-destination communication when the direct communication link cannot be established because of deep fading and/or shadowing. Nevertheless, two-hop communication makes wireless networks more vulnerable to overhearing as compared to single-hop/direct communication, raising a serious concern about security. To exploit relay selection with both high reliability and security, we propose a jamming-and-relaying (JaR) strategy to adopt one user as a jammer and another user as a traditional relay. Specifically, in this way, legitimate messages are protected against wire-tappers over both relay-destination and source-relay hops where the former and the latter are respectively secured by the jamming signals created by the jammer and the source. Meanwhile, the reliability of such cooperative communication systems is improved by selecting one user as a traditional relay with the highest signal-to-noise ratio over the source-relay channels. Moreover, both the jammer and the traditional relay operate with energy scavenged from source signals through a non-linear energy scavenger (NL-ES) to improve energy efficiency as well as motivate them to secure and forward source messages. The proposed JaR strategy is evaluated over Nakagami-m fading channels in terms of reliability and security by derived exact and asymptotic formulas. Illustrative results expose its superiority to two baseline strategies, namely non-jamming-and-relay selection (nJaR) and non-jamming non-relay selection (nJnR); more specifically, the proposed JaR strategy is more secure than two baseline strategies with a signal-to-noise ratio (SNR) gain of at least 7 dB and is more reliable than the nJnR strategy with a SNR gain of 4 dB for the fading severity \(m=3\). Nonetheless, the reliability-security trade-off presents in all the considered strategies. Additionally, an appropriate equilibrium between security and reliability is achievable by setting up system parameters in a proper manner. Furthermore, the NL characteristic of the energy scavengers drastically impacts the reliability yet insignificantly affects the security for the JaR strategy. Also, the NL-ES is more secured yet less reliable than the linear ES (L-ES).