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Channel Modeling and Performance Analysis for RIS-Assisted Communication Systems
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DOI：10.1109/JIOT.2025.3626769.png)
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Abstract
En 中文
Reconfigurable intelligent surfaces (RISs) have attracted significant attention due to their capability of establishing virtual line-of-sight (VLoS) links. This article proposes a channel model for RIS-assisted millimeter wave (mmWave) communication systems that incorporates the effective aperture (EA) of RIS elements, the horizontal and vertical rotation angles of the RIS, the servomechanism limitations associated with these rotation angles, and the activation criteria to constrain the feasible range of these rotation angles. To enhance the system performance, we jointly optimize the horizontal and vertical rotation angles of the RIS with the objective of maximizing the signal-to-noise ratio (SNR) based on the proposed model. An alternating optimization (AO) algorithm is developed to solve this problem efficiently. Specifically, the original optimization problem is decomposed into two subproblems corresponding to independent optimization of the horizontal and vertical angles, and closed-form optimal solutions are derived for each subproblem. Updating iteratively these closed-form solutions yields suboptimal horizontal and vertical rotation angles for the RIS. Moreover, a global optimal solution of closed-form to the original optimization problem is derived for the special case where the base station (BS) is positioned directly in front of the RIS. Numerical results demonstrate that the suboptimal rotation angles obtained by the AO algorithm closely approximate the optimal solutions. Furthermore, the proposed AO algorithm, which jointly optimizes both rotation angles, significantly outperforms the methods that individually optimize either the horizontal or vertical angle.
Keywords:
Effective aperture (EA)
millimeter wave (mmWave)
reconfigurable intelligent surfaces (RISs)
RIS rotation angles optimization
signal-to-noise ratio (SNR)
Journal
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8.9
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7.8W