Robust beamforming design for RIS-aided cell-free systems with CSI uncertainties and capacity-limited backhaul

In this paper, we consider the robust beamforming design in a reconfigurable intelligent surface (RIS)-aided cell-free (CF) system considering the channel state information (CSI) uncertainties of both the direct channels and cascaded channels at the transmitter with capacity-limited backhaul. We joi...

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Main Authors: Yao, Jiacheng, Xu, Jindan, Xu, Wei, Ng, Derrick Wing Kwan, Yuen, Chau, You, Xiaohu
Other Authors: School of Electrical and Electronic Engineering
Format: Article
Language:English
Published: 2023
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Online Access:https://hdl.handle.net/10356/172080
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Institution: Nanyang Technological University
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spelling sg-ntu-dr.10356-1720802023-11-22T01:16:28Z Robust beamforming design for RIS-aided cell-free systems with CSI uncertainties and capacity-limited backhaul Yao, Jiacheng Xu, Jindan Xu, Wei Ng, Derrick Wing Kwan Yuen, Chau You, Xiaohu School of Electrical and Electronic Engineering Engineering::Electrical and electronic engineering Robust Beamforming Design Capacity-Limited Backhaul In this paper, we consider the robust beamforming design in a reconfigurable intelligent surface (RIS)-aided cell-free (CF) system considering the channel state information (CSI) uncertainties of both the direct channels and cascaded channels at the transmitter with capacity-limited backhaul. We jointly optimize the precoding at the access points (APs) and the phase shifts at multiple RISs to maximize the worst-case sum rate of the CF system subject to the constraints of maximum transmit power of APs, unit-modulus phase shifts, limited backhaul capacity, and bounded CSI errors. By applying a series of transformations, the non-smoothness and semi-infinite constraints are tackled in a low-complexity manner that facilitates the design of an alternating optimization (AO)-based iterative algorithm. The proposed algorithm divides the considered problem into two subproblems. For the RIS phase shifts optimization subproblem, we exploit the penalty convex-concave procedure (P-CCP) to obtain a stationary solution and achieve effective initialization. For precoding optimization subproblem, successive convex approximation (SCA) is adopted with a convergence guarantee to a Karush-Kuhn-Tucker (KKT) solution. Numerical results demonstrate the effectiveness of the proposed robust beamforming design, which achieves superior performance with low complexity. Moreover, the importance of RIS phase shift optimization for robustness and the advantages of distributed RISs in the CF system are further highlighted. Ministry of Education (MOE) This work was supported in part by the National Key Research and Development Program 2020YFB1806608; in part by the NSFC under Grants 62022026 and 62211530108; in part by the Fundamental Research Funds for the Central Universities under Grants 2242022K60002 and 2242023K5003. The work of D. W. K. Ng was supported by the Australian Research Council’s Discovery Project (DP210102169, DP230100603). This work of C. Yuen was supported by the Ministry of Education, Singapore, under its MOE Tier 2 (Award number MOE-T2EP50220-0019). 2023-11-22T01:16:28Z 2023-11-22T01:16:28Z 2023 Journal Article Yao, J., Xu, J., Xu, W., Ng, D. W. K., Yuen, C. & You, X. (2023). Robust beamforming design for RIS-aided cell-free systems with CSI uncertainties and capacity-limited backhaul. IEEE Transactions On Communications, 71(8), 4636-4649. https://dx.doi.org/10.1109/TCOMM.2023.3277539 0090-6778 https://hdl.handle.net/10356/172080 10.1109/TCOMM.2023.3277539 2-s2.0-85160226254 8 71 4636 4649 en MOE-T2EP50220-0019 IEEE Transactions on Communications © 2023 IEEE. All rights reserved.
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Electrical and electronic engineering
Robust Beamforming Design
Capacity-Limited Backhaul
spellingShingle Engineering::Electrical and electronic engineering
Robust Beamforming Design
Capacity-Limited Backhaul
Yao, Jiacheng
Xu, Jindan
Xu, Wei
Ng, Derrick Wing Kwan
Yuen, Chau
You, Xiaohu
Robust beamforming design for RIS-aided cell-free systems with CSI uncertainties and capacity-limited backhaul
description In this paper, we consider the robust beamforming design in a reconfigurable intelligent surface (RIS)-aided cell-free (CF) system considering the channel state information (CSI) uncertainties of both the direct channels and cascaded channels at the transmitter with capacity-limited backhaul. We jointly optimize the precoding at the access points (APs) and the phase shifts at multiple RISs to maximize the worst-case sum rate of the CF system subject to the constraints of maximum transmit power of APs, unit-modulus phase shifts, limited backhaul capacity, and bounded CSI errors. By applying a series of transformations, the non-smoothness and semi-infinite constraints are tackled in a low-complexity manner that facilitates the design of an alternating optimization (AO)-based iterative algorithm. The proposed algorithm divides the considered problem into two subproblems. For the RIS phase shifts optimization subproblem, we exploit the penalty convex-concave procedure (P-CCP) to obtain a stationary solution and achieve effective initialization. For precoding optimization subproblem, successive convex approximation (SCA) is adopted with a convergence guarantee to a Karush-Kuhn-Tucker (KKT) solution. Numerical results demonstrate the effectiveness of the proposed robust beamforming design, which achieves superior performance with low complexity. Moreover, the importance of RIS phase shift optimization for robustness and the advantages of distributed RISs in the CF system are further highlighted.
author2 School of Electrical and Electronic Engineering
author_facet School of Electrical and Electronic Engineering
Yao, Jiacheng
Xu, Jindan
Xu, Wei
Ng, Derrick Wing Kwan
Yuen, Chau
You, Xiaohu
format Article
author Yao, Jiacheng
Xu, Jindan
Xu, Wei
Ng, Derrick Wing Kwan
Yuen, Chau
You, Xiaohu
author_sort Yao, Jiacheng
title Robust beamforming design for RIS-aided cell-free systems with CSI uncertainties and capacity-limited backhaul
title_short Robust beamforming design for RIS-aided cell-free systems with CSI uncertainties and capacity-limited backhaul
title_full Robust beamforming design for RIS-aided cell-free systems with CSI uncertainties and capacity-limited backhaul
title_fullStr Robust beamforming design for RIS-aided cell-free systems with CSI uncertainties and capacity-limited backhaul
title_full_unstemmed Robust beamforming design for RIS-aided cell-free systems with CSI uncertainties and capacity-limited backhaul
title_sort robust beamforming design for ris-aided cell-free systems with csi uncertainties and capacity-limited backhaul
publishDate 2023
url https://hdl.handle.net/10356/172080
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