Securing Untrusted RF-EH Relay Networks Using Cooperative Jamming Signals

We propose a new scheme to secure a wireless-powered untrusted cooperative-communication network, where a legitimate source node (Alice) transmits her information messages to a legitimate destination node (Bob) through the multiple amplify-and-forward untrusted relays. The relay nodes are assumed to be honest but curious nodes; hence, they are trusted at the service level but are untrusted at the information level. To reduce the energy consumption of the network, only one relay node is selected in each time slot to forward Alice's information signal. We assume a power-splitting-based energy-harvesting scheme, where each relay node splits its received signal into information and energy streams. Since the relay nodes are assumed to be untrusted at the information level, they attempt to decode the information intended to Bob while harvesting energy at the same time. When the relaying mode is selected, the scheme is realized over two non-overlapping time phases. To prevent any information leakage to the untrusted relay nodes, Bob and a cooperative jammer (John) inject jamming (artificial noise) signals during the first phase. During the second phase, the untrusted relay nodes that will not be forwarding the information signal must harvest energy to accumulate more energy to help Alice in future time slots. Moreover, the cooperative jammer will jam the untrusted relays to further power their batteries and prevent them from decoding the information-forwarding relay signal in case they decided to cheat and decode it. We model the battery state transitions at each relay as a finite-state Markov chain and analyze it. Our numerical results show the security gains of our proposed scheme relative to two benchmark schemes.This work was supported by NPRP from the Qatar National Research Fund (a member of Qatar Foundation) under Grant 8-627-2-260. The statements made herein are solely the responsibility of the authors.Scopu

User-Pair Selection in Multiuser Cooperative Networks With an Untrusted Relay

This paper investigates the physical-layer security of an amplify-and-forward wireless cooperative network, where N source nodes communicate with their corresponding destination nodes under the help of an untrusted relay. In each slot, only one user-pair is scheduled to transmit the information, and the destination-aided cooperative jamming is adopted to protect information from being intercepted by the untrusted relay. Three user-pair selection schemes have been proposed for the considered system, namely opportunistic user-pair selection (OUS) scheme, greedy user-pair selection (GUS) scheme, and genie-aided user-pair selection scheme. Both the secrecy outage probability and the average secrecy rate have been studied to evaluate the performance of the OUS and GUS schemes, and the asymptotic analysis has also been obtained. It reveals that the proposed schemes can improve the secrecy performance for the cooperative multiuser networks as the number of user-pairs increases. We also prove that the achievable diversity order of both OUS and GUS schemes is N/2 . Finally, numerical and simulation results are presented to validate the accuracy of the developed analytical results

Secrecy performance of untrustworthy AF relay networks using cooperative jamming and SWIPT

Abstract In this paper, the secrecy outage performance of a three-node amplify-and-forward relay network with an untrustworthy relay is investigated. To enable a secure transmission, we consider a destination-based jamming technique to prevent the relay from successfully decoding the secret messages between the source and the destination. In addition, the relay is assumed to be an energy-constrained device, thus being first energized by the source in order to be able to retransmit the information to the destination. In doing so, a time switching-based simultaneous wireless information and power transfer scheme is used. A closed-form asymptotic expression for the secrecy outage probability is derived in order to obtain a tight approximation at medium-to-high signal-to-noise ratio. The accuracy of the performed analysis is corroborated by Monte Carlo simulations through different illustrative cases. Numerical results show the impact of key system parameters on the secrecy performance, such as the time allocation factor between the energy harvesting and information transmission phases, the power allocation factor between source and destination for cooperative jamming, and the relay position, so as to provide insights on the design criteria for energy efficient and secure networks