Channel Estimation for RIS-Aided MU-MIMO mmWave Systems with Direct Channel Links
Taihao Zhang, Zhendong Peng, Cunhua Pan, Hong Ren, and Jiangzhou Wang

TL;DR
This paper introduces a three-stage channel estimation method for RIS-assisted MU-MIMO mmWave systems with direct links, improving accuracy by carefully designing pilot signals and RIS vectors.
Contribution
It proposes a novel three-stage estimation strategy that effectively estimates direct and cascaded channels in RIS-aided systems with direct links, reducing error propagation.
Findings
Outperforms existing channel estimation methods in accuracy.
Effectively estimates angles of departure and arrival for all users.
Reduces error propagation through orthogonal projection techniques.
Abstract
In this paper, we propose a three-stage unified channel estimation strategy for reconfigurable intelligent surface (RIS)-aided multi-user (MU) multiple-input multiple-output (MIMO) millimeter wave (mmWave) systems with the existence of the direct channels, where the base station (BS), the users and the RIS are equipped with uniform planar array (UPA). The effectiveness of the developed three-stage strategy stems from the careful design of both the pilot signal sequence of the users and the vectors of RIS. Specifically, in Stage I, the cascaded channel components are eliminated by configuring the RIS phase shift vectors with a {\pi} difference to estimate the direct channels for all users. The orthogonal subspace projection is employed in Stage II to obtain equivalent signal matrices, enabling the estimation of angles of departure (AoDs) of the user-RIS channel for all users. In Stage…
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Taxonomy
TopicsAdvanced Wireless Communication Technologies · Millimeter-Wave Propagation and Modeling · Advanced MIMO Systems Optimization
