This paper studies the secrecy transmission with the aid of a large-scale multi-antenna amplify-and-forward (AF) relay wireless powered by the source. Specifically, the wireless energy harvesting (WEH)-enabled relay devices a hybrid receiver architecture, in which the received power at each individual antenna is split for energy harvesting (EH) and information receiving (IR) in the first transmission phase; the aggregate of the total harvested power is further split for cooperative jamming (CJ) to confound the eavesdroppers, and AF for information transmission in the second transmission phase. Assuming that the eavesdroppers in the proximity are distributed as homogeneous Poisson point process (HPPP), no channel state information (CSI) but the density of the eavesdroppers is known to the relay, the ergodic secrecy rate (ESR) is used to characterize the secrecy performance. The optimum portion of power allocated for CJ is also derived. Simulation results also demonstrate the pronounced improvement on the ESR by CJ.
This paper studies the secrecy transmission with the aid of a large-scale multi-antenna amplify-and-forward (AF) relay wireless powered by the source. Specifically, the wireless energy harvesting (WEH)-enabled relay devices a hybrid receiver architecture, in which the received power at each individual antenna is split for energy harvesting (EH) and information receiving (IR) in the first transmission phase; the aggregate of the total harvested power is further split for cooperative jamming (CJ) to confound the eavesdroppers, and AF for information transmission in the second transmission phase. Assuming that the eavesdroppers in the proximity are distributed as homogeneous Poisson point process (HPPP), no channel state information (CSI) but the density of the eavesdroppers is known to the relay, the ergodic secrecy rate (ESR) is used to characterize the secrecy performance. The optimum portion of power allocated for CJ is also derived. Simulation results also demonstrate the pronounced improvement on the ESR by CJ.
This paper studies secrecy transmission with the aid of a group of wireless energy harvesting-enabled amplify-and-forward (AF) relays performing cooperative jamming (CJ) and relaying. The source node in the network does simultaneous wireless information and power transfer with each relay employing a power splitting receiver in the first phase; each relay further divides its harvested power for forwarding the received signal and generating artificial noise for jamming the eavesdroppers in the second transmission phase. In the centralized case with global channel state information (CSI), we provide the closed-form expressions for the optimal and/or suboptimal AF-relay beamforming vectors to maximize the achievable secrecy rate subject to individual power constraints of the relays, using the technique of semidefinite relaxation (SDR), which is proved to be tight. A fully distributed algorithm utilizing only local CSI at each relay is also proposed as a performance benchmark. Simulation results validate the effectiveness of the proposed multi-AF relaying with CJ over other suboptimal designs.
This paper analyzes the ergodic secrecy capacity of an energy-constrained multiple-antennas amplify-and-forward (AF) relaying system in the presence of a passive eavesdropper. In the first phase, the source broadcasts information signal, while the destination sends an artificial jamming signal. The jamming signal has two main purposes: 1) enhancing the system security; 2) increasing the energy harvesting (EH) at the relay node. In the second phase, the relay uses the harvested energy to amplify and forward the received signal to the destination. For this system model, explicit mathematical expressions for the ergodic secrecy capacity are derived for three different common EH-relaying protocols, namely, power splitting relaying (PSR), antenna selection and power splitting (ASPS) receiver, and ideal relaying receiver (IRR). Monte-Carlo simulations are included to validate the analysis and the effect of different parameters on the system security are investigated. The results show that, the ASPS receiver outperforms PSR in terms of secrecy capacity.
The emerging radio signal enabled simultaneous wireless information and power transfer (SWIPT), has drawn significant attention. To achieve secrecy transmission by cooperative jamming, especially in the upcoming 5G networks with self-sustainable mobile base stations (BSs) and yet not to add extra power consumption, we propose in this paper a new relay protocol, i.e., harvest-and-jam (HJ), in a relay wiretap channel with an additional set of spare helpers. Specifically, in the first transmission phase, a single-antenna transmitter (Tx) transfers signals carrying both information and energy to a multi-antenna amplify-and-forward (AF) relay and a group of multi-antenna helpers; in the second transmission phase, the AF relay processes the information and forwards it to the receiver while each of the helpers generates an artificial noise (AN), the power of which is constrained by its previously harvested energy, to interfere with the eavesdropper. By optimizing the transmit beamforming matrix for the AF relay and the covariance matrix for the AN, we maximize the secrecy rate for the receiver subject to transmit power constraints for the AF relay and all helpers. The formulated problem is shown to be non-convex, for which we propose an iterative algorithm based on alternating optimization. Finally, the performance of the proposed scheme is evaluated by simulations as compared to other heuristic schemes.
In this paper, we analyze the secrecy capacity of a half-duplex energy harvesting (EH)-based multi-antenna amplify-and-forward relay network in the presence of a passive eavesdropper. During the first phase, while the source is in the transmission mode, the legitimate destination transmits an auxiliary artificial noise (AN) signal which has two distinct purposes: 1) to transfer power to the relay and 2) to improve system security. Since the AN is known at the legitimate destination, it is easily cancelled at the intended destination, which is not the case at the eavesdropper. In this respect, we derive new exact analytical expressions for the ergodic secrecy capacity for various well-known EH relaying protocols, namely, time switching relaying (TSR), power splitting relaying (PSR), and ideal relaying receiver (IRR). Monte Carlo simulations are also provided throughout our investigations to validate the analysis. The impacts of some important system parameters, such as EH time, power splitting ratio, relay location, AN power, EH efficiency, and the number of relay antennas, on the system performance are investigated. The results reveal that the PSR protocol generally outperforms the TSR approach in terms of the secrecy capacity.
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.
Cooperative jamming has been demonstrated to be an effective means to provide secret wireless communications and yet this is realized at the expense of the power consumption of the friendly jammers. This paper considers the scenario where friendly jammers harvest energy wirelessly from the signal transmitted by the source, and then use only the harvested energy to transmit the jamming signals for improving the secrecy of the communications of the source to the destination. In particular, we investigate the use of multi-antenna harvest-and-jam (HJ) helpers in a multi-antenna amplify-and-forward (AF) relay wiretap channel assuming that the direct link between the source and destination is broken. Our goal is to maximize the achievable secrecy rate at the destination subject to the transmit power constraints of the AF relay and HJ helpers. In the case of perfect channel state information (CSI), the joint optimization of the artificial noise (AN) covariance for jamming and the AF beamforming matrix is presented as well as a suboptimal solution with lower complexity based on semidefinite relaxation (SDR) which is tight in this case. For the practical case where the CSI is imperfect at both the relay and the HJ helpers, we provide the formulation of the robust optimization for maximizing the worst-case secrecy rate. Using SDR techniques, a near-optimal robust scheme is proposed. Numerical results are provided to validate the effectiveness of the HJ protocol.