Fixed Region Beamforming Using Frequency Diverse Subarray for Secure mmWave Wireless Communications

Abstract

Millimeter-wave (mmWave) using conventional phased array (CPA) enables highly directional and fixed angular beamforming (FAB), therefore enhancing physical layer security (PLS) in the angular domain. However, as the eavesdropper is located in the direction pointed by the mainlobe of the informationcarrying beam, information leakage is inevitable and FAB cannot guarantee PLS performance. To address this threat, we propose a novel fixed region beamforming (FRB) by employing a frequency diverse subarray (FDSA) architecture to enhance the PLS performance for mmWave directional communications. In particular, we carefully introduce multiple frequency offset increments (FOIs) across subarrays to achieve a sophisticated beampattern synthesis that ensures a confined information transmission only within the desired angle-range region (DARR) in close vicinity of the target user. More specifically, we formulate the secrecy rate maximization problem with FRB over possible subarray FOIs, and consider two cases of interests, i.e., without/with the location information of eavesdropping, both turn out to be NPhard. For the unknown eavesdropping location case, we propose a seeker optimization algorithm to minimize the maximum sidelobe peak of the beampattern outside the DARR. As for the known eavesdropping location case, a block coordinate descend linear approximation algorithm is proposed to minimize the sidelobe level in the eavesdropping region. By using the proposed FRB, the mainlobes of all subarrays are constructively superimposed in the DARR while the sidelobes are destructively overlayed outside the DARR. Therefore, FRB takes prominent effect on confining information transmission within the DARR. Numerical simulations demonstrate that the proposed FDSA-based FRB can provide superior PLS performance over the CPA-based FAB.Index Terms-Frequency diverse subarray (FDSA), fixed region beamforming (FAB), angle, range, frequency offset increment (FOI), physical layer security (PLS), secrecy rate (SR).

Tailoring mmWave Physical Layer Security to Wireless Channel Knowledge

“…447586980). direction of eavesdropper [7], tighter beamforming towards the receiver [8], and side-lobe reduction [6].…”

Decomposed and Distributed Directional Modulation for Secure Wireless Communication

“…Consequently, it is of interest to seek to new secure transmission methods that can promote to an extra layer of security by introducing additional flexibility. The frequency diverse array (FDA) adds a small frequency offset across the array antennas, which results in exhibiting an extra rangedimension dependence secure transmission [19], [20]. In particular, the authors in [21] jointly designed the frequency offsets and the beamforming vector of the FDA transmitter to enhance PLS for proximal LU and Eve.…”

Theoretical Demonstration of Security Improvement of Optical Phased Array Based on Optically Injection-Locked Lasers

“…The SLL is defined as the power ratio between the main beam and peak sidelobe. A low SLL reduces information leakage and improves the beam power efficiency in the desired direction [26][27][28].…”