This paper investigates physical layer security of cooperative NOMA in a severe scenario where there is no direct link from the source to far destination while the direct link between the eavesdropper and source exists. An energy harvesting (EH) jammer aided cooperative NOMA (namely EJCN) scheme is proposed to enable secure communications for the scenario. In particular, the EH jammer can opportunistically harvest energy from ambient radio frequency (RF) signals without occupying special time and power resources, and the harvested energy is exploited to emit the artificial noise (AN) for confusing the eavesdropper. The closed-form expressions of secrecy throughput achieved by the EJCN scheme are derived to evaluate the secrecy performance for the scenario. An iterative algorithm is presented to obtain the optimal codeword rate. The analysis and simulation results show that the EJCN scheme can achieve better secrecy performance than conventional transmission scheme without an EH jammer, indicating the superiority of the proposed scheme. In addition, the codeword rate of users should be carefully designed to maximize the secrecy throughput.
This paper investigates physical layer security of cooperative NOMA in a severe scenario where there is no direct link from the source to far destination while the direct link between the eavesdropper and source exists. An energy harvesting (EH) jammer aided cooperative NOMA (namely EJCN) scheme is proposed to enable secure communications for the scenario. In particular, the EH jammer can opportunistically harvest energy from ambient radio frequency (RF) signals without occupying special time and power resources, and the harvested energy is exploited to emit the artificial noise (AN) for confusing the eavesdropper. The closed-form expressions of secrecy throughput achieved by the EJCN scheme are derived to evaluate the secrecy performance for the scenario. An iterative algorithm is presented to obtain the optimal codeword rate. The analysis and simulation results show that the EJCN scheme can achieve better secrecy performance than conventional transmission scheme without an EH jammer, indicating the superiority of the proposed scheme. In addition, the codeword rate of users should be carefully designed to maximize the secrecy throughput.
Non-orthogonal multiple access (NOMA) and wireless energy harvesting are two promising technologies for improving spectral efficiency and energy efficiency, respectively. In this paper, we study the physical layer security of a wireless-powered full-duplex (FD) relay-aided cooperative NOMA system. In particular, the source is wiretapped by an eavesdropper, and the FD relay assists the transmission from the source to a near user and a far user with self-energy recycling. To enhance the security performance of the system, we propose an artificial noise (AN)-aided cooperative transmission scheme, in which the relay emits a jamming signal to confuse the eavesdropper while receiving the signal from the source. For the proposed scheme, the ergodic secrecy sum rate (ESSR) is derived to characterize the secrecy performance and a lower bound of ESSR is obtained. Finally, numerical results verify the accuracy of the theoretical analysis of the proposed AN-aided secure transmission scheme. The superiority of the proposed scheme is also demonstrated since this scheme can achieve better secrecy performance, compared to the conventional cooperative NOMA scheme.
This paper studies the secure communications of a wireless-powered full-duplex cooperative non-orthogonal multiple access (CoNOMA) system with a source node, a group of near users, a far user and an external eavesdropper. In particular, the eavesdropper intends to wiretap the transmitted signals from the source. Two of the near users are picked up, served as a wireless-powered relay and a wireless friendly jammer, respectively. We propose a user selection and cooperative jamming based secure transmission scheme. Specifically, the source transmits a superimposed signal to the selected near user. The selected near user, who is employed as a relay, can harvest energy from the radio frequency signals and decode the information simultaneously. The harvested energy are then utilized to forward the signal to the far user. The jammer also collects energy from the source, and emits artificial noise by using the harvested energy to confuse the eavesdropper. Based on the proposed scheme, the closed-form expression for secrecy outage probability (SOP) and effective secrecy throughput (EST) are derived. The correctness of our theoretical analysis is verified by Monte-Carlo simulations, and the superiority of the proposed scheme in improving the system secure performance is also validated.
In this paper, we investigate the achievable secrecy rate in a relay channel where the source and the destination wish to keep the information confidential from an untrusted relay (potential eavesdropper). The relay has no energy supply, and harvests its required energy for relaying from its received signals. For radio-frequency (RF) Energy Harvesting (EH) at the relay, we adopt power splitting (PS) approach. We study the problem of achieving positive secrecy rates between the transmitter and the receiver while making use of an untrusted relay. Energy limitation at the relay makes the problem more interesting. Because, the relay must choose either to eavesdrop the signal to be able to decode or to harvest energy (from the information signal) to be able to forward the message. Our scheme to guarantee the secrecy uses cooperative jamming by either the destination or an extra jammer node. We derive the achievable secrecy rates for the compress-and-forward (CF) and amplify-and-forward (AF) relays for two different scenarios. First, we assume the destination and the jammer are two separate nodes. Then, we consider destination-assisted jamming. In addition, we let the relay to use both the sources and the jammers transmitted signals to harvest energy. Our numerical results show that our proposed schemes guarantee a positive secrecy rate by properly locating the jammer and allocating enough jamming power. However, for a given power budget (i.e., fixed total transmission and jamming power) there is an optimum amount for the jamming power.
In this study, the authors propose a cooperative transmission scheme with energy‐harvesting (EH) relays under wiretapping of an eavesdropper. In this scheme, the relays harvest energy from radio‐frequency (RF) signals of a source through power‐splitting receivers, and process arrived signals by amplify‐and‐forward (EH‐AF protocol) and decode‐and‐forward (EH‐DF protocol) technologies. In the proposed protocols, a best relay is selected at the destination so that the end‐to‐end achievable secrecy rates are maximal. Exact and asymptotic secrecy outage probability expressions are used to evaluate the EH‐AF and EH‐DF protocols, respectively, and are confirmed by Monte Carlo simulations. The simulation results show that (i) the EH‐DF protocol outperforms the EH‐AF protocol, and both proposed protocols are improved when the number of cooperative relays and the distances of the relay–eavesdropper links increase and the relays move toward the destination, (ii) the secrecy performance of the EH‐AF and EH‐DF protocols is the best at optimal power‐splitting ratios, which are obtained by the golden section search method, (iii) the energy conversion efficiency and the noise at RF‐to‐baseband conversion units seriously affect the proposed protocols, and finally, (iv) the theoretical analysis results fit those of the Monte Carlo simulations.
In this paper, we propose an energy harvestingbased jamming scheme to enhance secrecy outage probability (SOP) for cooperative relaying protocols. In the proposed scheme, one of available relays is selected to forward data from a source to a destination, while an energy-constrained relay harvests energy from the source's radio frequency signals to generate artificial noise to an eavesdropper. Moreover, we consider a generalized relay selection scheme, in which the Nth-best relay is resorted to help the source-destination communication. We derive exact and asymptotic expressions of the SOP over Rayleigh fading channels. Monte-Carlo simulations are performed to verify the analysis results and confirm the advantage of the proposed scheme.
This paper investigates secure transmission in a wireless powered cooperative communication network (WPCCN) over Nakagami-mfading channels, where multiple intermediate energy harvesting (EH) nodes with finite energy storage are deployed to assist the secure transmission between source and destination in the presence of an eavesdropper. Specifically, the intermediate EH nodes first harvest and accumulate energy from the source's signal and then forward the confidential signal or emit jamming signal to interfere the eavesdropper according to actual requirements. In order to exploit the intermediate EH nodes for secure improvement, considering both energy storage status and channel gains, three relay-and-jammer selection schemes at the intermediate nodes are proposed, namely: energy threshold based best-relay and random-jammer (ETBR), energy threshold based random-relay and best-jammer (ETRB), and energy threshold based best-relay and best-jammer (ETBB). For understanding the impact of critical parameters on the secrecy performance, we first capture the evolution of the EH nodes’ storages using finite-state Markov chain (FSMC) and then derive the analytical expressions for hybrid outage probability (HOP) and secrecy throughput (ST). Furthermore, numerical results demonstrate that our proposed selection schemes outperform the existing schemes (bR-rJ, rR-bJ, bR-bJ) due to the consideration of energy accumulation and storage status. In addition, there is a suitable value of the energy threshold for each proposed scheme to achieve the optimal secrecy performance.