On the secrecy performance and power allocation in relaying networks with untrusted relay in the partial secrecy regime

Abstract Recently, three useful secrecy metrics based on the partial secrecy regime were proposed to analyze secure transmissions on wireless systems over quasi-static fading channels, namely: generalized secrecy outage probability, average fractional equivocation, and average information leakage. These metrics were devised from the concept of fractional equivocation, which is related to the decoding error probability at the eavesdropper, so as to provide a comprehensive insight on the practical implementation of wireless systems with different levels of secrecy requirements. Considering the partial secrecy regime, in this paper we examine the secrecy performance of an amplify-and-forward relaying network with an untrusted relay node, where a destination-based jamming is employed to enable secure transmissions. In this regard, a closed-form approximation is derived for the generalized secrecy outage probability, and integral-form expressions are obtained for the average fractional equivocation and the average information leakage rate. Additionally, equal and optimal power allocation schemes are investigated and compared for the three metrics. From this analysis, we show that different power allocation approaches lead to different system design criteria. The obtained expressions are validated via Monte Carlo simulations

Impact of wireless energy transfer strategies on the secrecy performance of untrustworthy relay networks

Abstract This work investigates the secrecy outage performance of a dual-hop relaying network with an untrustworthy energy-constrained amplify-and-forward relay. A destination-based jamming technique is adopted in order to prevent the relay from decoding confidential messages from the source. Additionally, three time switching-based wireless energy transfer strategies are investigated for supplying power to the relay. For these three strategies, we derive simple closed-form asymptotic expressions for the secrecy outage probability at high signal-to-noise ratio. Moreover, we provide analytical expressions for the optimum power allocation factor for the information transmission phase. Finally, Monte Carlo simulations are carried out to verify the theoretical results through different illustrative cases

Wireless-powered full-duplex UAV relay networks over FTR channels

Abstract A thorough understanding of fundamental limits of wireless-powered unmanned aerial vehicle (UAV) relay networks in millimeter waves is still missing. We narrow this gap by investigating the outage performance of a UAV-assisted wireless network over fluctuating two-ray (FTR) channels. The FTR fading model is particularly appealing since well characterizes the wireless propagation in a wide range of frequencies, including those in millimeter waves. The proposed setup consists of a source-destination pair communicating with the assistance of a UAV, which is a wireless-powered relay station operating in full-duplex mode under the amplify-and-forward protocol. For the wireless energy harvesting at the UAV, wireless power transfer (WPT), simultaneous wireless information and power transfer (SWIPT), and self-recycling energy techniques are employed together. To characterize the system outage probability, we obtain an integral-form expression derived from an approximate analysis and a simple closed-form expression derived from an asymptotic analysis at the high signal-to-noise ratio (SNR) regime. Monte Carlo simulations are provided to validate the correctness of our theoretical results and provide insights on the network performance in terms of key system parameters. Interestingly, obtained results show that the FTR fading parameters corresponding to the first hop and second hop play no role on the system outage performance at high SNR. Instead, it is mainly governed by the effect of the residual self-interference at the UAV, leading to outage floors

Safeguarding MTC at the physical layer:potentials and challenges

Abstract 5G networks must provide a highly resilient, secure, and privacy-protected platform to support the emergence of new business and technologies expected from the so-called vertical-industry paradigm. However, as the definition and implementation of 5G networks are in progress, many security challenges arise. Thus, special emphasis will be given in the coming years to provide security and privacy for 5G and beyond networks. In this regard, physical layer security has been recognized as a potential solution to safeguard the confidentiality and privacy of communications in such stringent scenarios. In light of this, herein we provide an overview on some promising physical-layer techniques, focusing on the requirements and design challenges for machine-type communication scenarios. Key issues are discussed along with potential solutions

Performance analysis of full-duplex relay-aided NOMA systems using partial relay selection

Abstract Capitalizing on the benefits of non-orthogonal multiple access (NOMA) and full-duplex relaying as key technologies to boost spectral efficiency in the next generation of wireless communications, herein we investigate the performance of a cooperative network in which a source communicates with two destinations via one node selected from a set of full-duplex amplify-and-forward relays. For this purpose, a power-domain NOMA scheme is used to transmit information from the source to the destinations, and partial relay selection is performed to choose the relay based on the channel state information of the first hops. The system performance is characterized in terms of both the outage probability and the ergodic capacity, for which, exact analytical expressions are derived in integral form. In addition, to reduce the computational complexity of the obtained analytical results, closed-form expressions are derived from lower-bound, approximate, and asymptotic analyses. From these analytical expressions, the impact on the system performance of the number of relays, the power allocation factor between the NOMA destinations, and the residual self-interference at full-duplex relays is assessed. The correctness of our analyses is validated by Monte Carlo simulations, and a comparison with the half-duplex relay-aided NOMA system counterpart is also provided

Impact of self-energy recycling and cooperative jamming on SWIPT-based FD relay networks with secrecy constraints

Abstract This paper investigates the secrecy performance of a power splitting-based simultaneous wireless information and power transfer cooperative relay network in the presence of an eavesdropper. The relay is considered to operate in full-duplex (FD) mode to perform both energy harvesting and information decoding simultaneously. To accomplish that, the relay is assumed to employ two rechargeable batteries, which switch between power supplying mode and charging mode at each transmission block. We also assume that the self-interference inherent of the FD mode is not completely suppressed. Therefore, it is assumed that, after some stages of passive and active self-interference cancellation, there is still a residual self-interference (RSI). A portion of this RSI (remaining after passive cancellation) is recycled for energy harvesting. In order to improve the system secrecy performance, it is considered that the relay can split its transmit power to send the information signal and to emit a jamming signal to degrade the eavesdropper’s channel. The secrecy performance is evaluated in terms of the secrecy outage probability and the optimal secrecy throughput. Tight-approximate and asymptotic expressions are obtained for the secrecy outage probability, and the particle swarm optimization method is employed for addressing the secrecy throughput optimization problem. From numerical results, we show that the secrecy performance can be increased depending on the self-energy recycling channel condition. Finally, our derived expressions are validated via Monte Carlo simulations

Cognitive full-duplex decode-and-forward relaying networks with usable direct link and transmit-power constraints

Abstract The performance of an underlay cognitive radio network that coexists with a primary destination is studied in terms of the outage probability. The investigated secondary network comprises a source-destination pair communicating under the assistance of a full-duplex decode-and-forward relay. We consider the following key aspects pertinent to the underlay cognitive-radio approach and to the fullduplex operation at the relay: the transmit power constraint of the cognitive network by the maximum interference tolerated at the primary destination, as well as by the maximum-available transmit power at the cognitive terminals; the impact of the residual self-interference inherent to the relay; and the use of a joint-decoding technique at the destination in order to combine the concurrent signals coming from the source and relay, which enables the treatment of the direct-link transmission as information signal, rather than as interference. Herein, the joint effect of the maximum interference power constraint and the residual self-interference are both examined. To this end, an arbitrary power allocation between source and relay is allowed. Then, an accurate closed-form approximation to the outage probability is proposed, from which an asymptotic expression is derived for the high SNR ratio regime. Our analytical results are validated via Monte Carlo simulations. Importantly, we show that a maximum-available transmit power not only saves energy but also reduces the outage probability at medium to high SNR ratio

On the statistics of the ratio of nonconstrained arbitrary α ‐ μ random variables:a general framework and applications

Abstract In this paper, we derive closed‐form exact expressions for the main statistics of the ratio of two squared α‐μ random variables, which are of interest in many scenarios for future wireless networks where generalized distributions are more suitable to fit with field data. Importantly, different from previous proposals, our expressions are general in the sense that are valid for nonconstrained arbitrary values of the parameters of the α‐μ distribution. Thus, the probability density function, cumulative distribution function, moment generating function, and higher‐order moments are given in terms of both (i) the Fox H‐function for which we provide a portable and efficient Wolfram Mathematica code and (ii) easily computable series expansions. Our expressions can be used straightforwardly in the performance analysis of a number of wireless communication systems, including either interference‐limited scenarios, spectrum sharing, full‐duplex, or physical‐layer security networks, for which we present the application of the proposed framework. Moreover, closed‐form expressions for some classical distributions, derived as special cases from the α‐μ distribution, are provided as byproducts. The validity of the proposed expressions is confirmed via Monte Carlo simulations