Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey

This paper provides a comprehensive review of the domain of physical layer security in multiuser wireless networks. The essential premise of physical-layer security is to enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers without relying on higher-layer encryption. This can be achieved primarily in two ways: without the need for a secret key by intelligently designing transmit coding strategies, or by exploiting the wireless communication medium to develop secret keys over public channels. The survey begins with an overview of the foundations dating back to the pioneering work of Shannon and Wyner on information-theoretic security. We then describe the evolution of secure transmission strategies from point-to-point channels to multiple-antenna systems, followed by generalizations to multiuser broadcast, multiple-access, interference, and relay networks. Secret-key generation and establishment protocols based on physical layer mechanisms are subsequently covered. Approaches for secrecy based on channel coding design are then examined, along with a description of inter-disciplinary approaches based on game theory and stochastic geometry. The associated problem of physical-layer message authentication is also introduced briefly. The survey concludes with observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials, 201

Optimum Power Randomization for the Minimization of Outage Probability

Cataloged from PDF version of article.The optimum power randomization problem is studied to minimize outage probability in flat block-fading Gaussian channels under an average transmit power constraint and in the presence of channel distribution information at the transmitter. When the probability density function of the channel power gain is continuously differentiable with a finite second moment, it is shown that the outage probability curve is a nonincreasing function of the normalized transmit power with at least one inflection point and the total number of inflection points is odd. Based on this result, it is proved that the optimum power transmission strategy involves randomization between at most two power levels. In the case of a single inflection point, the optimum strategy simplifies to on-off signaling for weak transmitters. Through analytical and numerical discussions, it is shown that the proposed framework can be adapted to a wide variety of scenarios including log-normal shadowing, diversity combining over Rayleigh fading channels, Nakagami-m fading, spectrum sharing, and jamming applications. We also show that power randomization does not necessarily improve the outage performance when the finite second moment assumption is violated by the power distribution of the fading. © 2013 IEEE

Power splitting versus time switching based cooperative relaying protocols for SWIPT in NOMA systems

Non-orthogonal multiple access (NOMA) along with wireless power transfer have recently been adapted to cooperative communications for 5G and beyond wireless networks. This paper investigates NOMA based cooperative relaying wireless- powered networks (CRWPNs) where, decode-and-forward (DF) relaying and successive interference cancellation are both employed at a wireless-powered intermediate node. For simultaneous wireless information and power transfer (SWIPT), power-splitting relaying (PSR) and time switching-based relaying (TSR) protocols are considered in the NOMA based CRWPN. As a result, the combination of cooperative relaying power domain NOMA network and PSR and TSR protocols is proposed in this paper. The outage performance and ergodic rate of both protocols are analysed for evaluation of the impacts of energy harvesting (EH) time, EH efficiency, power splitting ratio, source data rate, and the distance between the nodes. In addition, two delay limited transmission (DLT) and delay tolerant transmission (DTT) modes are considered in this network model to investigate the throughput and ergodic rate of the system according to the source transmission rate. It is shown that the cooperative relaying NOMA (CRNOMA) scheme achieves a lower outage probability when compared to the conventional orthogonal multiple access (OMA) schemes. Additionally, the PSR outperforms the TSR in both low and high signal-to-noise ratio (SNR) regions in terms of throughput, ergodic rate and energy efficiency. For instance, the outage probability of CRNOMA for both PSR and TSR in SNR range of from -10 dB to +20 dB (i.e. a low SNR region) decreases gradually but not linearly. However, in SNR range of from +20 dB to +40 dB (i.e. a high SNR region), the outage probability of CRNOMA for both PSR and TSR decreases quickly. Furthermore, the energy efficiency is shown to be considerably enhanced with the employment of EH for CRNOMA. Finally, the impacts of the distance between the nodes on the performance and a comparison between two scenarios of having and without having direct links are evaluated