Antenna array design for directional modulation

Directional modulation (DM) has been applied to linear antenna arrays to increase security of signal transmission. However, only the azimuth angle is considered in the design, due to inherent limitation of the linear array structure, since linear antenna array lacks the ability to scan in the three dimensional (3-D) space. To solve the problem, planar antenna arrays are introduced in the design, where both the elevation angle and azimuth angle are considered. Moreover, a magnitude constraint for weight coefficients is introduced. Design examples are provided to verify the effectiveness of the proposed design

Multi-carrier based phased antenna array design for directional modulation

Directional modulation (DM) has been developed based on narrowband antenna arrays, which can form the desired constellation values in the directions of interest while scrambling the values and simultaneously maintaining a magnitude response as low as possible in other directions. In this study, for the first time, the authors develop a multi-carrier based DM framework using antenna arrays, where simultaneous data transmission over multiple frequencies can be achieved, so that a much higher data rate can be obtained. In addition, such a framework allows possible frequency division based multi-user access to the system and also provides the flexibility of using different modulation schemes at different frequencies. Then, they study the antenna location optimisation problem for multi-carrier based DM using a compressive sensing based approach by employing the group sparsity concept. Examples are provided for both the design of weight coefficients and the optimisation of antenna locations

Compressive sensing based sparse antenna array design for directional modulation

Directional modulation (DM) can be achieved based on uniform linear arrays where the maximum spacing between adjacent antennas is half-wavelength of the frequency of interest in order to avoid spatial aliasing. To exploit the additional degrees of freedom provided in the spatial domain, sparse antenna arrays can be employed for more effective DM. In this study, the spare array design problem in the context of DM is formulated from the viewpoint of compressive sensing (CS), so that it can be solved using standard convex optimisation toolboxes in the CS area. In detail, a common set of active antennas needs to be found for all modulation symbols generating a response close to the desired one. The key to the solution is to realise that group sparsity has to be employed, as a common antenna set cannot be guaranteed if the antenna locations are optimised for each modulation symbol individually. Moreover, two practical scenarios are considered for the proposed design: robust design with model errors and design with practical non-zero-sized antennas, and corresponding solutions are found by modifying the proposed standard solution

Sparse planar antenna array design for directional modulation

Directional modulation (DM) has been applied to sparse linear antenna arrays to increase security of signal transmission. In this work, we extend the DM design to sparse planar antenna arrays and provide the corresponding design formulations. In previous studies, group sparsity technique was used for sparse antenna array design, but no quantitative analyses were given. In this paper, both designs with and without group sparsity are provided, and the corresponding optimised antenna locations are shown explicitly. Design examples are provided to verify the effectiveness of the proposed design

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