Yao, J;
Lai, X;
Zhi, K;
Wu, T;
Jin, M;
Pan, C;
Elkashlan, M;
... Wong, KK; + view all
(2025)
A Framework of FAS-RIS Systems: Performance Analysis and Throughput Optimization.
IEEE Transactions on Wireless Communications
10.1109/TWC.2025.3590458.
(In press).
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Abstract
In this paper, we investigate reconfigurable intelligent surface (RIS)-assisted communication systems which involve a fixed-antenna base station (BS) and a mobile user (MU) that is equipped with fluid antenna system (FAS). Specifically, the RIS is utilized to enable communication for the user whose direct link from the base station is blocked by obstacles. We propose a comprehensive framework that provides transmission design for both static scenarios with the knowledge of channel state information (CSI) and harsh environments where CSI is hard to acquire. It leads to two approaches: a CSI-based scheme where CSI is available, and a CSI-free scheme when CSI is inaccessible. Given the complex spatial correlations in FAS, we employ block-diagonal matrix approximation and independent antenna equivalent models to simplify the derivation of outage probabilities in both cases. Based on the derived outage probabilities, we then optimize the throughput of the FAS-RIS system. For the CSI-based scheme, we first propose a gradient ascent-based algorithm to obtain a near-optimal solution. Then, to address the possible high computational complexity in the gradient algorithm, we approximate the objective function and confirm a unique optimal solution accessible through a bisection search method. For the CSI-free scheme, we apply the partial gradient ascent algorithm, reducing complexity further than full gradient algorithms. We also approximate the objective function and derive a locally optimal closed-form solution to maximize throughput. Simulation results validate the effectiveness of the proposed framework for the transmission design in FAS-RIS systems.
| Type: | Article |
|---|---|
| Title: | A Framework of FAS-RIS Systems: Performance Analysis and Throughput Optimization |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1109/TWC.2025.3590458 |
| Publisher version: | https://doi.org/10.1109/twc.2025.3590458 |
| Language: | English |
| Additional information: | This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
| Keywords: | Probability, Power system reliability, Antennas, Reconfigurable intelligent surfaces, Throughput, Optimization, Wireless communication, Approximation algorithms, Fluids, Switches |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10214479 |
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