Physical layer security jamming: Theoretical limits and practical designs in wireless networks

Physical layer security has been recently recognized as a promising new design paradigm to provide security in wireless networks. In addition to the existing conventional cryptographic methods, physical layer security exploits the dynamics of fading channels to enhance secured wireless links. In this approach, jamming plays a key role by generating noise signals to confuse the potential eavesdroppers, and significantly improves quality and reliability of secure communications between legitimate terminals. This article presents theoretical limits and practical designs of jamming approaches for physical layer security. In particular, the theoretical limits explore the achievable secrecy rates of user cooperation based jamming whilst the centralized, and game theoretic based precoding techniques are reviewed for practical implementations. In addition, the emerging wireless energy harvesting techniques are exploited to harvest the required energy to transmit jamming signals. Future directions of these approaches, and the associated research challenges are also briefly outlined

RF impairments: Research challenges and applications in next generation mobile communications

Wireless connectivity has truly become ubiquitous over the last few years, as can be concluded from the increasing number of electronic devices that are being equipped with wireless communication capabilities. Nowadays, the wireless application range has been extended to a wide variety of consumer lifestyle areas. This causes wireless systems to move towards the commodity markets, where price pressure is high. This creates a drive for low-cost solutions.   On the other hand, there is a persistent demand for increasing performance of wireless solutions, since the same throughput and quality of service are demanded as that of the wired solutions they are replacing. To meet these requirements, wireless communication systems are continuously applying wider bandwidths, larger signal dynamics, and higher carrier frequencies. This results in an ever-increasing demand on the performance of radio frequency (RF) front-ends, which at the same time have to be low-cost and power-efficient. Since the RF technology is, consequently, pushed to its operation boundaries, the intrinsic imperfections of the RF IC technology are more and more governing the system performance of wireless modems.   Direct-conversion transceivers can offer highly integrated low-cost hardware solutions for wireless communication networks. Sch transceivers, however, are also very sensitive to various radio frequency (RF) impairments, which can considerably limit the outage performance. The most prominent imperfections are the nonlinear distortion due to the mixer and power amplifier (PA) nonlinearities, image-frequency interference due to I/Q mismatch, non-constant group delay distortion in bandpass filters, and phase noise (PHN) and carrier frequency offset (CFO) in the oscillators.  These impairments, if not properly understood and taken into account, will cause spectrum regrowth, which may violate the spectrum masks imposed by the regulatory bodies, as well as interference and noise, which degrade the transmitted or received signal qualities and thereby limit the performance of the whole communications system. Most of the existing studies in the open literature assume an ideal RF front-end and hence neglect the impact of such practical RF hardware limitations.</p

Beamforming optimization for full-duplex wireless-powered MIMO systems

We propose techniques for optimizing transmit beamforming in a full-duplex multiple-input-multiple-output wireless-powered communication system, which consists of two phases. In the first phase, the wireless-powered mobile station (MS) harvests energy using signals from the base station (BS), whereas in the second phase, both MS and BS communicate to each other in a full-duplex mode. When complete instantaneous channel state information (CSI) is available, the BS beamformer and the time-splitting (TS) parameter of energy harvesting are jointly optimized in order to obtain the BS-MS rate region. The joint optimization problem is non-convex, however, a computationally efficient optimum technique, based upon semidefinite relaxation and line-search, is proposed to solve the problem. A sub-optimum zero-forcing approach is also proposed, in which a closed-form solution of TS parameter is obtained. When only the second-order statistics of transmit CSI is available, we propose to maximize the ergodic information rate at the MS while maintaining the outage probability at the BS below a certain threshold. An upper bound for the outage probability is also derived and an approximate convex optimization framework is proposed for efficiently solving the underlying non-convex problem. Simulations demonstrate the advantages of the proposed methods over the sub-optimum and half-duplex ones

Physical layer security jamming: Theoretical limits and practical designs in wireless networks

Physical layer security has been recently recognized as a promising new design paradigm to provide security in wireless networks. In addition to the existing conventional cryptographic methods, physical layer security exploits the dynamics of fading channels to enhance secured wireless links. In this approach, jamming plays a key role by generating noise signals to confuse the potential eavesdroppers, and significantly improves quality and reliability of secure communications between legitimate terminals. This article presents theoretical limits and practical designs of jamming approaches for physical layer security. In particular, the theoretical limits explore the achievable secrecy rates of user cooperation based jamming whilst the centralized, and game theoretic based precoding techniques are reviewed for practical implementations. In addition, the emerging wireless energy harvesting techniques are exploited to harvest the required energy to transmit jamming signals. Future directions of these approaches, and the associated research challenges are also briefly outlined