Abstract The secrecy rate of two‐way untrusted relay networks with imperfect channel state information based on SWIPT is investigated when multiple relays harvest energy from two sources. Despite assisting in information forwarding, the relays are considered untrusted in that they might attempt to eavesdrop on confidential information. To interfere with eavesdropping by untrusted relays, sources‐based friendly cooperative jamming is introduced. A joint power allocation and time switching strategy has been studied to maximize the sum secrecy rate of the system under total block transmission duration and power constraints. The genetic algorithm (GA) is introduced to optimize the proposed joint power allocation and time switching (JPTs) scheme. In addition, two suboptimal schemes are proposed: the power allocation and time switching scheme for individual power constraints and the power allocation scheme for equal time allocation. Simulation results demonstrate that the proposed joint power allocation and time switching strategy performs better in contributing to the total secrecy rate of the system.
Abstract The secrecy rate of two‐way untrusted relay networks with imperfect channel state information based on SWIPT is investigated when multiple relays harvest energy from two sources. Despite assisting in information forwarding, the relays are considered untrusted in that they might attempt to eavesdrop on confidential information. To interfere with eavesdropping by untrusted relays, sources‐based friendly cooperative jamming is introduced. A joint power allocation and time switching strategy has been studied to maximize the sum secrecy rate of the system under total block transmission duration and power constraints. The genetic algorithm (GA) is introduced to optimize the proposed joint power allocation and time switching (JPTs) scheme. In addition, two suboptimal schemes are proposed: the power allocation and time switching scheme for individual power constraints and the power allocation scheme for equal time allocation. Simulation results demonstrate that the proposed joint power allocation and time switching strategy performs better in contributing to the total secrecy rate of the system.
The secure communication of a two-way untrusted amplify-and-forward relay network under the imperfect channel state information is investigated. To improve the secrecy of the relay wiretap system, artificial noise is introduced into each source signal. The total and the individual power constraint conditions are considered. To maximize the attainable secrecy rate, an iterative power allocation algorithm is designed under the total power constraint. As a more practical system design, a suboptimal power allocation scheme is proposed. For the sake of comparison, the security performances of the noncooperative interference strategy and the one-way cooperative interference strategy are also investigated. Simulation results demonstrate that the proposed bidirectional cooperative interference schemes perform better in the secrecy rate of communication system.
Abstract A half‐duplex relaying network provides 2 opportunities for passive eavesdroppers (Eves) and 1 opportunity for untrusted relays to intercept the information. In this paper, we aim to enhance the physical layer security of a cooperative network where a single‐antenna source intends to communicate with a single‐antenna destination in the presence of a group of untrusted relays and a passive eavesdropper. The objective is to protect the data confidentially while concurrently relying on the untrusted relays as potential Eves to improve both the security and reliability of the network. To realize this objective, we design a joint cooperative beamforming and cooperative jamming strategy. With the aim of maximizing the instantaneous secrecy rate, an optimal power allocation (OPA) scheme is proposed where the transmission powers of both jammer and source are optimized simultaneously under the total power budget constraint. To further improve the secrecy rate, a jammer selection strategy is also proposed where cooperative jamming is performed by the destination or one of the idle relays. For the proposed scheme, a closed‐form expression of beamformer vector is derived by solving a generalized eigenvalue problem. Finally, for the OPA problem, it is possible to be neither convex nor concave. In this regard, all possible cases are investigated to determine the OPA factor accurately. Numerical results illustrate that the proposed joint OPA–cooperative beamforming scheme, together with the most appropriate jammer selection strategy, significantly increases the secrecy rate.
The secrecy performance of a wireless‐powered relaying system is investigated in the presence of imperfect channel state information. To improve the system secrecy performance, the destination splits a part of power to transmit the cooperative interference signal while the source transmits confidential information to the relay. The relay is assumed to be equipped with a non‐linear energy harvester and to harvest energy from the source and destination for information processing. A joint power splitting and time allocation scheme is studied to maximise the system secrecy rate. The joint optimisation problem is dealt with by the interior‐point method. For the sake of comparison, the equal time allocation scheme and the equal power splitting scheme are also investigated. The numerical results verify that the proposed scheme could achieve higher secrecy rate.
In this paper, we investigate the secure transmission in two-way untrusted amplify-and-forward relay networks with simultaneous wireless information and power transfer (SWIPT). Two secure SWIPT relaying strategies, namely, secure power splitting (SPS) and secure time switching (STS), are studied with the objective of secrecy rate (SR) and secure energy efficiency (SEE) maximization. First, the high signal-to-noise ratio approximations of SR and SEE are established, based on which non-convex SPS-based and convex STS-based SR maximization problems are formulated to jointly optimize the source transmit power and resource division ratio. Suboptimal solutions are obtained by employing Dinkelbach's method and Newton's method, respectively. Furthermore, to guarantee both the energy efficiency and secure quality of service (QoS) performance, SEE maximization problems are formulated with the consideration of the energy harvesting activation constraint and the target SR requirement. The intractable non-convex SEE maximization problems are reformulated as parameter programming, transformed to Lagrange dual problems, and finally solved by two SEE resource allocation algorithms with low complexity. Numerical results verify the convergence and effectiveness of the proposed algorithms and provide new insights into relaying strategy design and secure relay placement.
Abstract In this paper, for energy harvesting (EH) two‐way relay (TWR) networks with two‐sided eavesdroppers, the problem of secure information transmission is investigated. Based on this system model, a novel full‐duplex (FD) relaying jamming scheme is proposed to achieve simultaneously information reception, EH and jamming signal transmission at the cooperative relay. Particularly, the entire transmission phase and received signal at relay node are divided into two different time durations and three different parts by time allocation (TA) and power splitting (PS), respectively. For the aim of maximizing the sum secrecy rate, adaptive TA factor and PS factor are jointly optimized. We derive the non‐convex optimization function. To solve this highly non‐convex optimization problem, a heuristic approach based on particle swarm optimization (PSO) is proposed. Numerical results verify the superior sum secrecy rate of the proposed scheme. Besides, the impact of system parameters on the output performance is analyzed.
Untrusted relays might decode the information while forwarding it and lead to threaten the security of the system in some realistic scenarios. The aim of the paper is to maximize the secrecy performance, and therefore on the ground of the cooperative jamming, we propose a novel power allocation-relay selection program in a multi-untrusted relay network where numerous antennas are equipped in the source and the destination simultaneously. Besides, we allow an optimal application of the power allocation factor and the proper selection of the relays, which makes the Ergodic Secrecy Rate (ESR) increased directly. Moreover, the closed-form expressions of the ESR in different scenarios to measure the secrecy performance are acquired. It can be known that the simulation results of the ESR are compliant with the theoretical, especially when Signal-to-Noise Ratio (SNR) is low. Apart from this, the ESR in theoretical values are tested to be approximately equal to the simulation. Compared to other relay selection strategies like partial selection strategy and the Max-Min (MM) selection strategy, the scheme proposed here can get the secrecy performance strengthen better.