In this letter, we investigate the secure transmission in radio frequency (RF) powered two-hop untrusted relay networks, where the source node and untrusted relay are both wireless powered by an RF power supplier. Specifically, considering the non-linear energy-harvesting (EH) model, the two-process communication protocol is proposed. The secrecy rate is maximized by jointly designing the beamforming vector at source and beamforming matrix at relay, under the constraints of transmit power at RF power supplier and destination. The secrecy rate maximization (SRM) is non-convex, hence we propose an alternative optimization (AO) based iterative algorithm. Numerical results demonstrate that the proposed scheme can significantly increase the secrecy rate compared to the baseline schemes.
In this letter, we investigate the secure transmission in radio frequency (RF) powered two-hop untrusted relay networks, where the source node and untrusted relay are both wireless powered by an RF power supplier. Specifically, considering the non-linear energy-harvesting (EH) model, the two-process communication protocol is proposed. The secrecy rate is maximized by jointly designing the beamforming vector at source and beamforming matrix at relay, under the constraints of transmit power at RF power supplier and destination. The secrecy rate maximization (SRM) is non-convex, hence we propose an alternative optimization (AO) based iterative algorithm. Numerical results demonstrate that the proposed scheme can significantly increase the secrecy rate compared to the baseline schemes.
This paper investigates secure transmission in the radio-frequency (RF) powered untrusted relay networks. The relay conducts amplify-and-forward (AF) protocol and may intercept information passively. Based on the physical-layer security technique, a two-phase communication protocol is proposed for transmit security. We aim to minimize the average total transmit power by jointly designing the transmit parameters of the networks under the security quality of service (QoS). The power minimization problem is non-convex, hence an alternative optimization (AO) based algorithm is proposed. The simulation results show that the proposed transmit scheme can significantly increase the power efficiency.
The broadcast nature of the wireless medium allows unintended users to eavesdrop on confidential information transmission. In this regard, we investigate the problem of secure communication between a source and a destination via a wireless energy harvesting untrusted node that acts as a helper to relay the information; however, the source and destination nodes wish to keep the information confidential from the relay node. To realize the positive secrecy rate, we use destination-assisted jamming. Being an energy-starved node, the untrusted relay harvests energy from the received radio-frequency (RF) signals, which include the source's information signal and the destination's jamming signal. Thus, we utilize the jamming signal efficiently by leveraging it as a useful energy source. At the relay, to enable energy harvesting and information processing, we adopt power splitting (PS) and time switching (TS) policies. To evaluate the secrecy performance of this proposed scenario, we derive analytical expressions for two important metrics, viz., the secrecy outage probability and the ergodic secrecy rate. The numerical analysis reveals design insights into the effects of different system parameters such as PS ratio, energy harvesting time, target secrecy rate, transmit signal-to-noise ratio (SNR), relay location, and energy conversion efficiency factor, on secrecy performance. Specifically, the PS policy achieves better optimal secrecy outage probability and optimal ergodic secrecy rate than that of the TS policy at higher target secrecy rate and transmit SNR, respectively.
In this article, we raise the concern on secure energy efficiency (SEE) over the wireless-powered untrusted relay networks with nonlinear energy harvesting (EH). To achieve data confidentiality and secrecy performance enhancement concurrently, the untrusted relay can enable simultaneous energy signal reception and confidential information forwarding during the second phase, where no dedicated energy transmission phase or relaying signal splitting is needed for the energy supply. In particular, with the help of destination jamming, the relay can also harvest energy from source signal and jamming signal during the first phase, which is different from conventional relaying protocol that only harvests energy from source and recycled energy. Considering the nonlinear EH efficiency, our objective is to maximize the SEE through piecewise region selection and power allocation. To address this intractable nonconvex problem, a two-layer algorithm based on optimization decoupling, fractional programming, Lagrange dual decomposition and difference of convex functions (DC) programming is proposed. The core idea of the proposed algorithm is to convert the primary problem into simple subproblems by sequentially exploiting the above-mentioned optimization methods. Simulation results reveal the superior secrecy performance of the proposed scheme. The proposed algorithm achieves near-optimal solutions with faster convergence rate.
This article investigates secure communication between a source and a destination via multiple radio frequency (RF) energy harvesting (EH) relays, in which the RF-EH relays are untrusted and apply the amplify-and-forward policy. On the one hand, to prevent the untrusted relays from eavesdropping the confidential information, the destination-aided jamming is employed, in which the destination emits jamming signal to interfere the relays while the source transmits information signal. On the other hand, the power splitting (PS) policy is adopted at the relays to harvest energy and process information, in which every relay has a finite energy storage to accumulate the energy harvested from the source’s information signal and destination’s jamming signal. To achieve energy-efficient and fully distributed implementation, we propose an energy-aware distributed beamforming (EADB) scheme, in which each relay only needs local information to decide whether to assist the source-destination communication. To evaluate the secrecy performance of the EADB scheme, the charging and discharging behaviors of the relays’ energy storage are first tracked using the Markov chain. On this basis, we derive analytical expressions for the hybrid outage probability (HOP) and secure energy efficiency (SEE) of the considered network. Finally, numerical results show that the EADB scheme has a better secrecy performance than the existing scheme. In addition, despite the curiousness of the untrusted relays, deploying more relays and increasing their energy storage capacity can enhance the security of the considered network.
In this paper, we consider a non-regenerative relay network supporting simultaneous wireless information and power transfer, in which the energy harvesting relay is powered by radio-frequency signals from the source node. Assuming imperfect channel state information from the source/relay to the destination/eavesdropper, we investigate the artificial noise-aided secure robust beamformer that minimize the transmission power at the relay, while guaranteeing the secrecy rate constraint and the transmit power constraint at the relay. In particular, two types of energy harvesting strategies are considered termed power splitting (PS) and time switching (TS), respectively. These constraints make the optimization problems formulated non-convex and challenging, which are efficiently solved by using the S-procedure and semidefinite relaxation techniques to formulate a tractable approximated version of the original problems. Numerical results show the effectiveness of the proposed robust beamforming schemes. Furthermore, the PS strategy performs better than the TS strategy.
Limited power and computational resources make the employment of complex classical encryption schemes unrealistic in resource-limited networks, e.g., the Internet of Things (IoT). To this end, physical layer security (PLS) has shown great potential in securing such resource-limited networks. To further combat the power scarcity in IoT nodes, radio frequency (RF) based energy harvesting (EH) is an attractive energy source while relaying can enhance the energy efficiency and extend the range of data transmission. Additionally, due to deploying low-cost hardware, imperfections in the RF chain of IoT transceivers are common. Against this background, in this paper, we investigate an untrusted EH relay-aided secure communication with RF impairments. Specifically, the relay simultaneously receives the desired signal from the source and the jamming from the destination in the first phase. Hence the relay is unable to extract the confidential desired signal. The resultant composite signal is then amplified by the relay in the second phase by using the energy harvested from the composite signal followed by its transmission to the destination. Since the destination is the original source of the jamming, its effect can be readily subtracted from the composite signal to recover the original desired signal of the source. Moreover, in the face of hardware impairments (HWIs) in all nodes, maintaining optimal power management both at the source and destination may impose excessive computations on an IoT node. We solve this problem by deep learning (DL) based optimal power management maximizing the secrecy rate based on the instantaneous channel coefficients. We show that our learning-based scheme can reach the accuracy of the exhaustive search method despite its considerably lower computational complexity. Moreover, we developed an optimization framework for judiciously sharing HWIs across the nodes, so that we attain the maximum secrecy rate. To derive an efficient solution, we utilize a majorization-minimization (MM)algorithm, which is a particular instance in the family of successive convex approximation (SCA) methods. The simulation results show that the proposed HWI aware design considerably improves the secrecy rate.