Summary In this paper, we investigate the problem of secure communication for a scenario, which consists of one pair of source‐destination nodes and one untrusted relay. The source communicates with the destination via the help of energy harvesting–aware untrusted relay, which acts as the helper to forward the source information to the destination; however, the relay also acts as the unintended user to eavesdrop the source information. To keep the source information confidential from untrusted relay, the destination‐assisted jamming technique is deployed. We evaluate the impact of energy harvesting protocols on such a secure communication scenario through the proposed energy transfer protocols, namely, source‐based energy harvesting protocol and maximum energy harvesting protocol. To evaluate the secrecy performance of these proposed schemes, we derive analytical expressions for two important performance metrics including intercept probability and strictly positive secrecy capacity. The numerical analysis reveals the different trade‐off between secure performance and relevant system parameters (i.e., power splitting ratio, time switching ratio, energy conversion efficiency, transmit signal‐to‐noise ratio, and relay location). Simulation results are also provided to demonstrate the accuracy of the developed analytical expression.
Summary In this paper, we investigate the problem of secure communication for a scenario, which consists of one pair of source‐destination nodes and one untrusted relay. The source communicates with the destination via the help of energy harvesting–aware untrusted relay, which acts as the helper to forward the source information to the destination; however, the relay also acts as the unintended user to eavesdrop the source information. To keep the source information confidential from untrusted relay, the destination‐assisted jamming technique is deployed. We evaluate the impact of energy harvesting protocols on such a secure communication scenario through the proposed energy transfer protocols, namely, source‐based energy harvesting protocol and maximum energy harvesting protocol. To evaluate the secrecy performance of these proposed schemes, we derive analytical expressions for two important performance metrics including intercept probability and strictly positive secrecy capacity. The numerical analysis reveals the different trade‐off between secure performance and relevant system parameters (i.e., power splitting ratio, time switching ratio, energy conversion efficiency, transmit signal‐to‐noise ratio, and relay location). Simulation results are also provided to demonstrate the accuracy of the developed analytical expression.
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.
This article studies a secure communication of a simultaneous wireless information and power transfer system in which an energy-constrained untrusted relay, which harvests energy from the wireless signals, helps the communication between the source and destination and is able to decode the source’s confidential signal. Additionally, the source’s confidential signal is also overheard by a passive eavesdropper. To create positive secrecy capacity, a destination-assisted jamming signal that is completely cancelled at the destination is adopted. Moreover, the jamming signal is also exploited as an additional energy source. To evaluate the secrecy performance, analytical expressions for the secrecy outage probability (SOP) and the average secrecy capacity are derived. Moreover, a high-power approximation for the SOP is presented. The accuracy of the analytical results is verified by Monte Carlo simulations. Numerical results provide valuable insights into the effect of various system parameters, such as the energy-harvesting efficiency, secrecy rate threshold, power-splitting ratio, transmit powers, and locations of the relay and eavesdropper, on the secrecy performance.
In this paper, we consider secure communication via a wireless-powered untrusted relay with outdated channel state information (CSI). The low security clearance of the relay means that both the source and destination wish to keep information confidential from it. To prevent the relay from decoding the source information, the destination emits a jamming signal to the relay during data transmission by the source. The wireless-powered relay uses both the data and the jamming signals as valuable sources of energy for the amplify-and-forward relaying process. In addition, it can adopt either a power splitting or a time switching policy to determine the proportions of energy harvesting and information processing. However, when the CSI of the relay-to-destination link is outdated, the destination cannot remove the jamming signal completely from the relaying signal due to imperfect channel reciprocity. To evaluate the effect of outdated CSI on the secrecy performance, we derive the analytical expressions of two performance metrics, outage probability (Pout) for delay-limited transmission and ergodic secrecy rate (R̅) for delay-tolerant transmission. The results of the analysis also allow us to find the jamming power level and energy harvesting ratio to optimize Poutand R̅, respectively. Numerical simulations are used to verify the precision of our analysis, and confirm that the proposed secure relaying protocols accomplish near-optimal secrecy performances. Our results indicate that there is a need to reduce the jamming power level to ensure secure communication when the channel is severely outdated, while outdated CSI has a relatively low impact on the energy harvesting ratio.
This paper investigates secure communications of energy harvesting untrusted relay networks, where the destination assists jamming signal to prevent the untrusted relay from eavesdropping and to improve the forwarding ability of the energy constrained relay. Firstly, the source and the destination transmit the signals to the relay with maximal ratio transmission (MRT) technique or transmit antenna selection (TAS) technique. Then, the destination utilizes maximal ratio combining (MRC) technique or receive antenna selection (RAS) technique to receive the forwarded information. Therefore, four transmission and reception schemes are considered. For each scheme, the closed-form expressions of the secrecy outage probability (SOP) and the connection outage probability (COP) are derived. Besides, the effective secrecy throughput (EST) metric is analyzed to achieve a good tradeoff between security and reliability. In addition, the asymptotic performance of EST is also considered at the high signal-to-noise ratio (SNR). Finally, simulation results illustrate that: (1) the EST of the system with MRT and MRC scheme are superior to other schemes, however, in the high SNR regime, the EST of the system with MRT scheme is inferior to TAS; and (2) for the source node, there exists an optimal number of antennas to maximize the EST of the proposed schemes.
In this study, the authors investigate the security and the reliability performance of a two‐way relay‐based network, where a source–destination pair establishes secured communication through a wireless‐powered untrusted amplify‐and‐forward relay while employing a friendly jammer. The relay utilises the harvested energy from radio‐frequency signals sent by the sources to forward the received data; however, the friendly jammer employs that to generate and transmit noise‐like signals to confuse the curious relay. Two power transmission protocols, namely variable power transmission (VPT) and constant power transmission (CPT) at the jammer and relay are adopted. As a benchmark to highlight the performance advantages of employing a jammer, they also considered the case of zero power transmission (ZPT), where there is no jammer in the network. For the three scenarios, the intercept probability (IP) and the connection outage probability (COP), as well‐known secrecy criteria associated with the successful transmission are mathematically examined. Finally, the derived expressions are confirmed by comparison with Monte–Carlo simulations and furthermore, numerical examples are provided to demonstrate the effects of system parameters on the IP and the COP metrics. Specifically, they find that jammer's artificial noise distribution plays a paramount role in the secrecy performance of the considered system.
In this work, we focus on the issue of secure communication in energy harvesting untrusted relay networks taking into account the impact of hardware impairments, where an energy‐constrained relay, powered by received radio frequency signals, attempts to decode sensitive data from the source without authorization. To achieve secure communication, we employ destination‐assisted jamming to prevent the untrusted relay from decoding sensitive data while serving as a useful energy source. We derive the interception probability (IP), connection outage probability (COP), and effective secrecy throughput (EST) in closed form for time switching relaying (TSR) strategy. Subsequently, we conduct an asymptotic analysis in the high signal‐to‐noise ratio (SNR) regime to provide practical insights into how various system parameters affect security, reliability, and efficiency, including time switching factor and the level of hardware impairments. Our findings demonstrate that the presence of hardware impairments improves security performance but compromises reliability performance, which does more harm than good.