An Overview of Physical Layer Security With Finite-Alphabet Signaling

Abstract

Providing secure communications over the physical layer with the objective of achieving secrecy without requiring a secret key has been receiving growing attention within the past decade. The vast majority of the existing studies in the area of physical layer security focus exclusively on the scenarios where the channel inputs are Gaussian distributed. However, in practice, the signals employed for transmission are drawn from discrete signal constellations such as phase shift keying and quadrature amplitude modulation. Hence, understanding the impact of the finite-alphabet input constraints and designing secure transmission schemes under this assumption is a mandatory step toward a practical implementation of physical layer security. With this motivation, this paper reviews recent developments on physical layer security with finite-alphabet inputs. We explore transmit signal design algorithms for single-antenna as well as multi-antenna wiretap channels under different assumptions on the channel state information at the transmitter. Moreover, we present a review of the recent results on secure transmission with discrete signaling for various scenarios including multi-carrier transmission systems, broadcast channels with confidential messages, cognitive multiple access and relay networks. Throughout the article, we stress the important behavioral differences of discrete versus Gaussian inputs in the context of the physical layer security. We also present an overview of practical code construction over Gaussian and fading wiretap channels, and discuss some open problems and directions for future research.

Programming Wireless Security Through Learning‐Aided Spatiotemporal Digital Coding Metamaterial Antenna

“…This so‐called multipath effect is caused by refraction and reflection of waves from water bodies and terrestrial objects. The knowledge of channel gains between the antenna elements at the transmitter and those at a receiver, known as channel state information (CSI), is commonly available at two levels of perfect instantaneous CSI and partial CSI, [ 2,47 ] where the former amounts to the actual realization of the channel gain at a given time, while the latter implies only the statistical distribution of the channel. In practice, CSI knowledge can readily be acquired in OFDM systems where certain subcarriers are allotted for sending/receiving known signals termed “pilot.” Having access to the received version of the pilot and the actual transmitted pilot, one can utilize methods like least squares to estimate the channel coefficients.…”

“…The last few years have witnessed a rapid proliferation of mobile users and communicating devices in the realm of wireless communication systems. [1,2] In this vein, the vision of "smart and connected" devices has been put forth by the industry, suggesting that the Internet-of-Things (IoT)-driven revolution is just around the corner. For IoT networks, even the most conservative estimates are projecting tens of billions of devices by 2030.…”

“…Physical layer (PHY) security seeks to provide a comprehensive authentication mechanism for a communication system by exploiting the unique radio signal and electromagnetic characteristics of the communication links. [2,4,5] As a promising PHY security technique, directional modulation (DM) has enjoyed broad research attention in the last few years, [6,7] as it has the capability of transmitting digitally modulated signals whose waveforms are well preserved only along a preselected direction along which legitimate user equipments are located. In practice, DM can be realized by conventional approaches for radio frequency front-ends, such as phased antenna array or digital beamforming, to provide the necessary weighting coefficients to distort (and diminish) modulated signals at undesired directions.…”

Noncoherent Massive MIMO With Embedded One-Way Function Physical Layer Security

“…The resilience of the proposed PLS-protected N-DSTC scheme described in Subsection V-A to the eavesdropping attack described above can be assessed via its secrecy rate under a finite-alphabet signaling which is given by [30], [31], [32], and [33]…”

Programming nonreciprocity and harmonic beam steering via a digitally space-time-coded metamaterial antenna

“…On the other hand, time modulation has also been applied to antenna arrays [28], in which a predetermined periodic sequence can achieve side lobe reduction for the fundamental frequency pattern [29]. Moreover, generated harmonic components can be leveraged to provide physical layer security in wireless communication as well as enable radar detection [30][31][32][33][34][35][36][37][38][39][40][41][42]. Nevertheless, for conventional time modulated antenna arrays, pin diodes are usually employed as RF switches that decrease the power efficiency due to power dissipation in their off state [43].…”