In this paper, we propose a two-way secure communication scheme where two transceivers exchange confidential messages via a wireless-powered untrusted amplify-and-forward relay in the presence of an external jammer. We take into account both friendly jamming (FJ) and Gaussian noise jamming (GNJ) scenarios. Based on the time switching (TS) architecture at the relay, the data transmission is done in three phases. In the first phase, both the energy-starved nodes, the untrustworthy relay and the jammer, are charged by noninformation radio frequency (RF) signals from the sources. In the second phase, the two sources send their information signals and concurrently, the jammer transmits artificial noise to confuse the curious relay. Finally, the third phase is dedicated to forward a scaled version of the received signal from the relay to the sources. For the proposed secure transmission schemes, we derive new closed-form lower-bound expressions for the ergodic secrecy sum rate (ESSR) in the high signal-to-noise ratio (SNR) regime. We further analyze the asymptotic ESSR to determine the key parameters; the high SNR slope and the high SNR power offset of the jamming based scenarios. To highlight the performance advantage of the proposed FJ, we also examine the scenario of without jamming (WoJ). Finally, numerical examples and discussions are provided to acquire some engineering insights, and to demonstrate the impacts of different system parameters on the secrecy performance of the considered communication scenarios. The numerical results illustrate that the proposed FJ significantly outperforms the traditional one-way communication and the constellation rotation (CR) approach, as well as our proposed benchmarks, the two-way WoJ and GNJ scenarios.
In this paper, we propose a two-way secure communication scheme where two transceivers exchange confidential messages via a wireless-powered untrusted amplify-and-forward relay in the presence of an external jammer. We take into account both friendly jamming (FJ) and Gaussian noise jamming (GNJ) scenarios. Based on the time switching (TS) architecture at the relay, the data transmission is done in three phases. In the first phase, both the energy-starved nodes, the untrustworthy relay and the jammer, are charged by noninformation radio frequency (RF) signals from the sources. In the second phase, the two sources send their information signals and concurrently, the jammer transmits artificial noise to confuse the curious relay. Finally, the third phase is dedicated to forward a scaled version of the received signal from the relay to the sources. For the proposed secure transmission schemes, we derive new closed-form lower-bound expressions for the ergodic secrecy sum rate (ESSR) in the high signal-to-noise ratio (SNR) regime. We further analyze the asymptotic ESSR to determine the key parameters; the high SNR slope and the high SNR power offset of the jamming based scenarios. To highlight the performance advantage of the proposed FJ, we also examine the scenario of without jamming (WoJ). Finally, numerical examples and discussions are provided to acquire some engineering insights, and to demonstrate the impacts of different system parameters on the secrecy performance of the considered communication scenarios. The numerical results illustrate that the proposed FJ significantly outperforms the traditional one-way communication and the constellation rotation (CR) approach, as well as our proposed benchmarks, the two-way WoJ and GNJ scenarios.
In this paper, we propose a self-dependent two-way secure communication where two sources exchange confidential messages via a wireless powered untrusted amplify-and-forward (AF) relay and friendly jammer (FJ). By adopting the time switching (TS) architecture at the relay, the data transmission is accomplished in three phases: Phase I) Energy harvesting by the untrusted relay and the FJ through non-information transmissions from the sources, Phase II) Information transmission by the sources and jamming transmissions from the FJ to reduce information leakage to the untrusted relay; and Phase III) Forwarding the scaled version of the received signal from the untrusted relay to the sources. For the proposed system, we derive a new closed-form lower bound expression for the ergodic secrecy sum rate (ESSR). Numerical examples are provided to demonstrate the impacts of different system parameters such as energy harvesting time, transmit signal-to-noise ratio (SNR) and the relay/FJ location on the secrecy performance. The numerical results illustrate that the proposed network with friendly jamming (WFJ) outperforms traditional one-way communication and the two-way without friendly jamming (WoFJ) policy.
In this paper, we propose a two-way secure communication network where two sources exchange confidential messages via a wireless powered untrusted amplify-and-forward (AF) relay and a friendly jammer (FJ). By adopting the time switching (TS) architecture at the relay, the data transmission is accomplished in three phases. In the first phase, both the relay and FJ are charged by non-information radio frequency signals from the sources. In the second phase, the two sources transmit information signals and concurrently, the FJ transmits artificial noise to confuse the curious relay. Finally, the third phase is dedicated to forward the scaled version of the received signal from the relay to the sources. For the proposed network, we derive a new closed-form lower-bound expression for the ergodic secrecy sum rate (ESSR) in the high signal-to-noise ratio (SNR) regime. As a benchmark, we also examine the scenario of without friendly jamming (WoFJ) to highlight the performance advantages of the proposed with friendly jamming (WFJ) scenario. We further specify the high SNR slope and the high SNR power offset to determine the effect of friendly jamming on the ESSR. In the next step, novel compact closed-form expressions are derived for the intercept probability (IP) as a well-known security metric. Finally, numerical examples are provided to demonstrate the impacts of different system parameters such as energy harvesting time ratio, transmit SNR and the power allocation factor on the secrecy performance of both WFJ and WoFJ scenarios. The results illustrate that the proposed WFJ network outperforms the traditional one-way communication and the two-way WoFJ policy.
In this paper, we examine the secrecy performance of two-way relaying between a large-scale multiple antenna base station (BS) and a single antenna mobile user (MU) in the presence of a multiple antenna external jammer. We consider the untrusted relaying scenario, where an amplify-and-forward relay is both a necessary helper and a potential eavesdropper to the BS and MU transmissions. With the aim of maximizing the instantaneous secrecy sum rate, we derive new closed-form solutions for the optimal power allocation (OPA) under the following three scenarios: 1) without jamming (WoJ) where the jammer is not activated; 2) friendly jamming (FJ) where the jamming signal is known a priori at the BS and MU; and 3) Gaussian noise jamming (GNJ) where the jamming signal is unknown at the BS and MU. Based on our OPA solutions, new closed-form expressions are derived for the ergodic secrecy sum rate (ESSR) with Rayleigh fading channels. Furthermore, we characterize the high signal-to-noise ratio slope and power offset of the ESSR to provide a fundamental comparison of the WoJ, FJ, and GNJ scenarios. Based on our analysis, we propose a simple relay selection criterion for the scenario when the BS and MU are assisted by multiple untrusted relays. Numerical examples are presented to demonstrate the impact of the jammer's location, number of antennas and the advantage of the proposed relay selection criterion on the secrecy performance. Our findings highlight that similar to the trusted relaying scenario, the ESSR of all three secure transmission scenarios improve as the number of untrusted relays increases. Moreover, we highlight an interesting insight that the OPA for the GNJ scenario results in the same ESSR performance as the OPA for the WoJ scenario.
In this paper, we examine the secrecy performance of two-way relaying between a multiple antenna base station (BS) and a single antenna mobile user (MU) in the presence of a multiple antenna friendly jammer (FJ). We consider the untrusted relaying scenario where an amplify-and-forward relay is both a necessary helper and a potential eavesdropper. To maximize the instantaneous secrecy sum rate, we derive new closed-form solutions for the optimal power allocation (OPA) between the BS and MU under the scenario of relaying with friendly jamming (WFJ). Based on the OPA solution, new closed-form expressions are derived for the ergodic secrecy sum rate (ESSR) with Rayleigh fading channel. Furthermore, we explicitly determine the high signal-to-noise ratio slope and power offset of the ESSR to highlight the benefits of friendly jamming. Numerical examples are provided to demonstrate the impact of the FJ's location and number of antennas on the secrecy performance.
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.
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.