This paper explores the use of a full-duplex (FD) friendly jammer to secure the communication between a transmitter and a receiver in the presence of a passive eavesdropper. The friendly jammer is considered as a wireless-powered node without embedded power supply but can harvest energy from radio frequency (RF) signals, accumulate it in the storage, and use the harvested energy to perform the cooperative jamming (CJ). A novel CJ protocol termed accumulate-and-jam (AnJ) is proposed to improve the jammer efficiency, which splits the transmission blocks into dedicated energy harvesting (DEH) blocks and opportunistic energy harvesting (OEH) blocks. In DEH blocks, the transmitter transfers wireless power to replenish the jammer. In OEH blocks, the transmitter sends information to the receiver. Using the accumulated energy, the jammer transmits jamming signals to confound the eavesdropper. Mean-while, thanks to the FD capability, the jammer can continue to harvest energy from the signals overheard from the transmitter. Compared with the existing protocols using a wireless powered half-duplex (HD) jammer, the proposed design possesses the advantage of uninterrupted energy harvesting at the jammer. A closed-form expression for the secrecy outage probability of the considered system is derived. Numerical results show that our proposed AnJ protocol can significantly outperform its HD counterpart in terms of secrecy outage probability.
This paper explores the use of a full-duplex (FD) friendly jammer to secure the communication between a transmitter and a receiver in the presence of a passive eavesdropper. The friendly jammer is considered as a wireless-powered node without embedded power supply but can harvest energy from radio frequency (RF) signals, accumulate it in the storage, and use the harvested energy to perform the cooperative jamming (CJ). A novel CJ protocol termed accumulate-and-jam (AnJ) is proposed to improve the jammer efficiency, which splits the transmission blocks into dedicated energy harvesting (DEH) blocks and opportunistic energy harvesting (OEH) blocks. In DEH blocks, the transmitter transfers wireless power to replenish the jammer. In OEH blocks, the transmitter sends information to the receiver. Using the accumulated energy, the jammer transmits jamming signals to confound the eavesdropper. Mean-while, thanks to the FD capability, the jammer can continue to harvest energy from the signals overheard from the transmitter. Compared with the existing protocols using a wireless powered half-duplex (HD) jammer, the proposed design possesses the advantage of uninterrupted energy harvesting at the jammer. A closed-form expression for the secrecy outage probability of the considered system is derived. Numerical results show that our proposed AnJ protocol can significantly outperform its HD counterpart in terms of secrecy outage probability.
This paper develops a new cooperative jamming protocol, termed accumulate-and-jam (AnJ), to improve physical layer security in wireless communications. Specifically, a full-duplex (FD) friendly jammer is deployed to secure the direct communication between source and destination in the presence of a passive eavesdropper. We consider the friendly jammer as an energy-constrained node without embedded power supply but with an energy harvesting unit and rechargeable energy storage; it can thus harvest energy from the radio frequency signals transmitted by the source, accumulate the energy in its battery, and then use this energy to perform cooperative jamming. In the proposed AnJ protocol, based on the energy status of the jammer and the channel state of source-destination link, the system operates in either dedicated energy harvesting (DEH) or opportunistic energy harvesting (OEH) mode. In DEH mode, the source sends dedicated energy-bearing signals and the jammer performs energy harvesting. In OEH mode, the source transmits an information-bearing signal to the destination. Meanwhile, using the harvested energy, the wireless-powered jammer transmits a jamming signal to confound the eavesdropper. Thanks to the FD capability, the jammer also harvests energy from the information-bearing signal that it overhears from the source. We study the complex energy accumulation and consumption procedure at the jammer by considering a practical finite-capacity energy storage, of which the long-term stationary distribution is characterized through applying a discrete-state Markov Chain. An alternative energy storage with infinite capacity is also studied to serve as an upper bound. We further derive closed-form expressions for two secrecy metrics, i.e., secrecy outage probability and probability of positive secrecy capacity. In addition, the impact of imperfect channel state information on the performance of our proposed protocol is also investigated. Numerical results validate all theoretical analyses and reveal the merits of the proposed AnJ protocol over its half-duplex counterpart.
Wireless energy harvesting, physical-layer security, and full-duplex wireless are important, emerging fifth generation (5G) technologies. In this paper, we thus investigate a source-destination link with an energy-harvesting full-duplex relay and a jammer (to degrade the eavesdropper channel) in the presence of an eavesdropper. Thus, to exploit energy harvesting and to improve security, we propose a full-duplex jammer (FDJ) protocol and its half-duplex version (HDJ). Two cases for availability of the eavesdropper channel state information (ECSI) are considered: complete ECSI and incomplete ECSI. For both FDJ and HDJ protocols and for complete ECSI, we derive the instantaneous and average secrecy rates and compute optimal time split for energy harvesting. To gain more insights, we consider a practical interference-limited scenario and derive closed-form cumulative distribution function of the signal-to-interference plus noise ratio at the destination and eavesdropper nodes. Comparatively, we show that FDJ improves instantaneous secrecy rate over HDJ. However, the degree of improvement is highly dependent on time split for energy harvesting, amount of self-interference, the channel gains, and locations of the nodes. Our findings reveal that FDJ increases the average secrecy rate 150% over HDJ and 260% over HD relaying without jammer. For incomplete ECSI scenario, we derive asymptotic secrecy outage and show that FDJ performs better for small-to-medium values of source powers; otherwise, HDJ yields a higher gain.
This paper studies a robust resource allocation framework to enhance physical layer security where it is assumed that the system is equipped with a full-duplex (FD) receiver in contrast to conventional frameworks where a half-duplex (HD) receiver is at hand. Conventionally, relays are used as jammer to reduce the signal quality received by the eavesdroppers so as to increase the secrecy transmission rate between the legitimate transmitter and receiver. This is referred to as cooperative jamming (CJ). In a system equipped with a FD receiver, we propose to use the FD receiver as the jammer, i.e., the FD receiver simultaneously transmits jamming signals toward the eavesdropper while receiving data from the transmitter. The proposed scheme eliminates the need for external helpers, i.e., jamming relays which is welcome from practical point of view. We consider different scenarios to compare the proposed scheme against the CJ scheme in which, under a legitimate transmitter power constraint, optimal power allocation is obtained for each scenario to maximize the secrecy rate. To take into account the impact of imperfect state information of the channels between the eavesdropper and other nodes on the network, worst-case optimization approaches are considered. Simulation results demonstrate that for certain positions of the jamming relay and eavesdropper, the proposed system can outperform the conventional CJ schemes.
Exploring a cooperative node as a friendly jammer is an effective means of providing secure communication between a source-destination pair in the presence of an eavesdropper. In this work, we consider the use of a wireless-powered friendly jammer. Without relying on external energy supply, the friendly jammer is powered by the source node via wireless power transfer. We apply a simple time-switching protocol where the power transfer and jammer-assisted secure transmission occur in different time blocks. By investigating the long-term behavior of the communication protocol, we derive a closed-form expression of the throughput. We further optimize the jamming power and the rate parameters for maximizing the throughput subject to a secrecy outage probability constraint.
This letter considers wireless-powered cooperative jamming to secure communication between a transmitter (Tx) and an information receiver, in the presence of an energy receiver (ER), which is termed a potential eavesdropper. The full-duplex jammer harvests energy from the Tx's information signal and transmits jamming signal at the same time, where the jamming signal not only confounds the ER (potential eavesdropper) but also charges the ER. Our goal is to maximize the secrecy information rate by jointly optimizing the power allocation at the Tx and jammer, while maintaining the harvested energy requirement of the ER. The studied problem is non-convex and we propose the optimal solution based on the Lagrange method. Simulation results show that the proposed scheme significantly outperforms the benchmark schemes.
In this paper, we investigate the secrecy capacity of a point-to-point, full-duplex (FD) wirelesly powered communication system in the presence of a passive eavesdropper (EVE). The considered system is comprised of an energy transmitter (ET), an energy harvesting user (EHU), and a passive EVE. The ET transmits radio-frequency energy, which is used for powering the EHU as well as for generating interference at the EVE. The EHU uses the energy harvested from the ET to transmit confidential messages back to the ET. As a consequence of the FD mode of operation, both the EHU and the ET are subjected to self-interference, which has different effects at the two nodes. In particular, the self-interference impairs the decoding of the received message at the ET, whilst it serves as an additional energy source at the EHU. For this system model, we derive an upper and a lower bound on the secrecy capacity. For the lower bound, we propose a simple achievability scheme. Our numerical results show significant improvements in terms of achievable secrecy rate when the proposed communication scheme is employed against its half-duplex counterpart, even for practical self-interference values at the ET.