749 research outputs found
Directional Modulation via Symbol-Level Precoding: A Way to Enhance Security
Wireless communication provides a wide coverage at the cost of exposing
information to unintended users. As an information-theoretic paradigm, secrecy
rate derives bounds for secure transmission when the channel to the
eavesdropper is known. However, such bounds are shown to be restrictive in
practice and may require exploitation of specialized coding schemes. In this
paper, we employ the concept of directional modulation and follow a signal
processing approach to enhance the security of multi-user MIMO communication
systems when a multi-antenna eavesdropper is present. Enhancing the security is
accomplished by increasing the symbol error rate at the eavesdropper. Unlike
the information-theoretic secrecy rate paradigm, we assume that the legitimate
transmitter is not aware of its channel to the eavesdropper, which is a more
realistic assumption. We examine the applicability of MIMO receiving algorithms
at the eavesdropper. Using the channel knowledge and the intended symbols for
the users, we design security enhancing symbol-level precoders for different
transmitter and eavesdropper antenna configurations. We transform each design
problem to a linearly constrained quadratic program and propose two solutions,
namely the iterative algorithm and one based on non-negative least squares, at
each scenario for a computationally-efficient modulation. Simulation results
verify the analysis and show that the designed precoders outperform the
benchmark scheme in terms of both power efficiency and security enhancement.Comment: This manuscript is submitted to IEEE Journal of Selected Topics in
Signal Processin
Coherent optical binary polarisation shift keying heterodyne system in the free-space optical turbulence channel
In this paper, analytical and simulation results for the bit error rate (BER) performance and fading penalty of a coherent optical binary polarization shift keying (2PolSK) heterodyne system adopted for a free space optical (FSO) communication link modeled as the log-normal and the negative exponential atmospheric turbulence channels are presented. The conditional and unconditional BER expressions are derived, demonstrating the comprehensive similarity between the 2PolSK and the binary frequency shift keying (2FSK) schemes with regards to the system sensitivity. The power penalty due to the non-ideal polarization beam splitter (PBS) is also analyzed. The receiver sensitivity employing 2PolSK is compared with other modulation schemes in the presence of turbulence and the phase noise. The results show that 2PolSK offers improved signal-to-noise ratio (SNR) performance compared to the binary amplitude shift keying (2ASK)
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Rethinking Secure Precoding via Interference Exploitation: A Smart Eavesdropper Perspective
Based on the concept of constructive interference (CI), multiuser
interference (MUI) has recently been shown to be beneficial for communication
secrecy. A few CI-based secure precoding algorithms have been proposed that use
both the channel state information (CSI) and knowledge of the instantaneous
transmit symbols. In this paper, we examine the CI-based secure precoding
problem with a focus on smart eavesdroppers that exploit statistical
information gleaned from the precoded data for symbol detection. Moreover, the
impact of correlation between the main and eavesdropper channels is taken into
account. We first modify an existing CI-based preocding scheme to better
utilize the destructive impact of the interference. Then, we point out the
drawback of both the existing and the new modified CI-based precoders when
faced with a smart eavesdropper. To address this deficiency, we provide a
general principle for precoder design and then give two specific design
examples. Finally, the scenario where the eavesdropper's CSI is unavailable is
studied. Numerical results show that although our modified CI-based precoder
can achieve a better energy-secrecy trade-off than the existing approach, both
have a limited secrecy benefit. On the contrary, the precoders developed using
the new CI-design principle can achieve a much improved trade-off and
significantly degrade the eavesdropper's performance
Directional Modulation for Compact Devices
A new directional modulation system which uses radiation pattern data for modulation encoding is proposed. The approach allows compact multiport antennas (e.g. MIMO capable antennas) to be used for directional modulation, replacing extensive arrays. The modulation weighting coefficients are calculated with a fixed, antenna specific equation, thus reducing computational complexity. The solution is intended to enhance privacy in small, battery-operated wireless devices, required for âInternet of Thingsâ applications
A Tutorial on Interference Exploitation via Symbol-Level Precoding: Overview, State-of-the-Art and Future Directions
IEEE Interference is traditionally viewed as a performance limiting factor in wireless communication systems, which is to be minimized or mitigated. Nevertheless, a recent line of work has shown that by manipulating the interfering signals such that they add up constructively at the receiver side, known interference can be made beneficial and further improve the system performance in a variety of wireless scenarios, achieved by symbol-level precoding (SLP). This paper aims to provide a tutorial on interference exploitation techniques from the perspective of precoding design in a multi-antenna wireless communication system, by beginning with the classification of constructive interference (CI) and destructive interference (DI). The definition for CI is presented and the corresponding mathematical characterization is formulated for popular modulation types, based on which optimization-based precoding techniques are discussed. In addition, the extension of CI precoding to other application scenarios as well as for hardware efficiency is also described. Proof-of-concept testbeds are demonstrated for the potential practical implementation of CI precoding, and finally a list of open problems and practical challenges are presented to inspire and motivate further research directions in this area
Interference Exploitation via Symbol-Level Precoding: Overview, State-of-the-Art and Future Directions
Interference is traditionally viewed as a performance limiting factor in wireless communication systems, which is to be minimized or mitigated. Nevertheless, a recent line of work has shown that by manipulating the interfering signals such that they add up constructively at the receiver side, known interference can be made beneficial and further improve the system performance in a variety of wireless scenarios, achieved by symbol-level precoding (SLP). This paper aims to provide a tutorial on interference exploitation techniques from the perspective of precoding design in a multi-antenna wireless communication system, by beginning with the classification of constructive interference (CI) and destructive interference (DI). The definition for CI is presented and the corresponding mathematical characterization is formulated for popular modulation types, based on which optimization-based precoding techniques are discussed. In addition, the extension of CI precoding to other application scenarios as well as for hardware efficiency is also described. Proof-of-concept testbeds are demonstrated for the potential practical implementation of CI precoding, and finally a list of open problems and practical challenges are presented to inspire and motivate further research directions in this area
Transmit Precoding for Interference Exploitation in the Underlay Cognitive Radio Z-channel
This paper introduces novel transmit beamforming approaches for the cognitive radio (CR) Z-channel. The proposed transmission schemes exploit non-causal information about the interference at the SBS to re-design the CR beamforming optimization problem. This is done with the objective to improve the quality of service (QoS) of secondary users by taking advantage of constructive interference in the secondary link. The beamformers are designed to minimize the worst secondary user's symbol error probability (SEP) under constraints on the instantaneous total transmit power, and the power of the instantaneous interference in the primary link. The problem is formulated as a bivariate probabilistic constrained programming (BPCP) problem. We show that the BPCP problem can be transformed for practical SEPs into a convex optimization problem that can be solved, e.g., by the barrier method. A computationally efficient tight approximate approach is also developed to compute the near-optimal solutions. Simulation results and analysis show that the average computational complexity per downlink frame of the proposed approximate problem is comparable to that of the conventional CR downlink beamforming problem. In addition, both the proposed methods offer significant performance improvements as compared to the conventional CR downlink beamforming, while guaranteeing the QoS of primary users on an instantaneous basis, in contrast to the average QoS guarantees of conventional beamformers
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