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Effective Rank Maximization for Active RIS-Assisted MIMO Systems
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DOI：10.1109/TCOMM.2025.3628735.png)
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Abstract
En 中文
In strong line-of-sight (LoS) scenarios, the lack of scattering paths leads to significant rank deficiency in the channel, thereby limiting the spatial multiplexing capabilities of multiple-input multiple-output (MIMO) systems. To address this inherent deficiency, reconfigurable intelligent surfaces (RISs) have been proposed as a promising solution for enhancing the channel scattering environment in the context of sixth-generation (6G) networks. However, traditional passive RISs often require a large number of elements to counteract multiplicative fading. In contrast, active RISs (ARISs) can greatly reduce the reflecting elements requirement and effectively overcome the multiplicative fading. This paper investigates using multiple ARISs to reshape the wireless channel and formulates the effective rank (ER) maximization problem under two ARIS phase-shift models. We propose a multi-phase particle swarm optimization (MPSO) scheme to optimize the phase shifts of the ARISs under a continuous phase-shift model. However, the continuous phase-shift model entails substantial hardware implementation costs. To solve this, we introduce the multi-phase maximum cross-swapping algorithm (MMCA) under a discrete phase-shift model. Furthermore, we explore the impact of ARIS deployment positions on the channel ER and employ the sparrow search algorithm (SSA) to adjust the ARIS positions. The SSA-MPSO scheme is then proposed, which alternately optimizes the deployment positions and phase shifts of multiple ARISs, achieving an ER close to the theoretical upper bound. Simulation results demonstrate that the proposed scheme significantly outperforms baseline schemes, effectively enhancing the spectral efficiency.
Keywords:
Line-of-sight communications
rank deficiency
multiple-input multiple-output
active reconfigurable intelligent surfaces
alternating iterative optimization
Journal
IF:
8.3
Papers:
1.2W
Citations:
3.6W
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