Abstract
Recently, reconfigurable intelligent surfaces (RISs) have received much interest from both academia and industry due to their flexibility and cost-effectiveness in adjusting the phase and amplitude of wireless signals with low-cost passive reflecting elements. In particular, many RIS-aided techniques have been proposed to improve both data rate and energy efficiency for 6G wireless communication systems. In this paper, we propose a novel RIS-based channel randomization (RCR) technique for improving physical-layer security (PLS) for a time-division duplex (TDD) downlink cellular wire-tap network which consists of a single base station (BS) with multiple antennas, multiple legitimate pieces of user equipment (UE), multiple eavesdroppers (EVEs), and multiple RISs. We assume that only a line-of-sight (LOS) channel exists among the BS, the RISs, and the UE due to propagation characteristics of tera-hertz (THz) spectrum bands that may be used in 6G wireless communication systems. In the proposed technique, each RIS first pseudo-randomly generates multiple reflection matrices and utilizes them for both pilot signal duration (PSD) in uplink and data transmission duration (DTD) in downlink. Then, the BS estimates wireless channels of UE with reflection matrices of all RISs and selects the UE that has the best secrecy rate for each reflection matrix generated. It is shown herein that the proposed technique outperforms the conventional techniques in terms of achievable secrecy rates.
Highlights
Reconfigurable intelligent surfaces (RISs) or intelligent reflecting surfaces (IRSs) have been proposed to achieve high spectral and energy efficiency for future 6G wireless communication systems [1,2,3,4]
Millimeter-wave and tera-hertz (THz) communication are known to be well-compatible with the RISs for line-ofsight (LOS) environments, since mmWave and THz communications suffer from significant path-loss in general
We propose a novel RIS-based channel randomization (RCR) technique for improving physical-layer security (PLS) for a time-division duplex (TDD) downlink cellular wire-tap network consisting of a single base station (BS), multiple legitimate pieces of user equipment (UE), multiple passive EVEs, and multiple RISs
Summary
Reconfigurable intelligent surfaces (RISs) or intelligent reflecting surfaces (IRSs) have been proposed to achieve high spectral and energy efficiency for future 6G wireless communication systems [1,2,3,4]. Joint transmit beamforming and reflecting beamforming optimization with artificial noise (AN) or jamming signals have been proposed for PLS enhancement in various wireless networks [33,34,35,36,37,38,39] These techniques aim to maximize the signal to interference-plus-noise ratio (SINR) for a legitimate user and to minimize SINR for the EVE by transmitting a signal that combines the private message and AN. We propose a novel RIS-based channel randomization (RCR) technique for improving PLS for a time-division duplex (TDD) downlink cellular wire-tap network consisting of a single BS, multiple legitimate pieces of UE, multiple passive EVEs, and multiple RISs. Each RIS pseudo-randomly generates multiple reflection matrices and utilizes them for pilot signal duration (PSD) in uplink and data transmission duration (DTD).
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