Simultaneously Transmitting and Reflecting (STAR) RIS assisted over-the-air computation systems
Simultaneously Transmitting and Reflecting (STAR) RIS assisted over-the-air computation systems
The performance of over-the-air computation (Air-Comp) systems degrades due to the hostile channel conditions of wireless devices (WDs), which can be significantly improved by the employment of reconfigurable intelligent surfaces (RISs). However, the conventional RISs require that the WDs have to be located in the half-plane of the reflection space, which restricts their potential benefits. To address this issue, the novel family of simultaneously transmitting and reflecting reconfigurable intelligent surfaces (STAR-RIS) is considered in AirComp systems to improve the computation accuracy across a wide coverage area. To minimize the computation mean-squared-error (MSE) in STAR-RIS assisted AirComp systems, we propose a joint beamforming design for optimizing both the transmit power at the WDs, as well as the passive reflect and transmit beamforming matrices at the STAR-RIS, and the receive beamforming vector at the fusion center (FC). Specifically, in the updates of the passive reflect and transmit beamforming matrices, closed-form solutions are derived by introducing an auxiliary variable and exploiting the coupled binary phase-shift conditions. Moreover, by assuming that the number of antennas at the FC and that of elements at the STAR-RIS/RIS are sufficiently high, we theoretically prove that the STAR-RIS assisted AirComp systems provide higher computation accuracy than the conventional RIS assisted systems. Our numerical results show that the proposed beamforming design outperforms the benchmark schemes relying on random phase-shift constraints and the deployment of conventional RIS. Moreover, its performance is close to the lower bound achieved by the beamforming design based on the STAR-RIS dispensing with coupled phase-shift constraints.
Array signal processing, Massive MIMO, OFDM, Optimization, Power demand, Synchronization, Wireless communication, simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS), Over-the-air computation (AirComp), internet-of-things (IoT) networks
1309-1322
Zhai, Xiongfei
3607a1ff-dc1d-425a-b725-6cf8190536ab
Han, Guojun
0d7729f5-be8f-48b7-8bbb-6ce9499aa7ea
Cai, Yunlong
ec2375f2-7878-430a-ac52-ff73781b4bf4
Liu, Yuanwei
2767c2bc-6199-4106-ac28-81c3dadcfa29
Hanzo, Lajos
66e7266f-3066-4fc0-8391-e000acce71a1
1 March 2023
Zhai, Xiongfei
3607a1ff-dc1d-425a-b725-6cf8190536ab
Han, Guojun
0d7729f5-be8f-48b7-8bbb-6ce9499aa7ea
Cai, Yunlong
ec2375f2-7878-430a-ac52-ff73781b4bf4
Liu, Yuanwei
2767c2bc-6199-4106-ac28-81c3dadcfa29
Hanzo, Lajos
66e7266f-3066-4fc0-8391-e000acce71a1
Zhai, Xiongfei, Han, Guojun, Cai, Yunlong, Liu, Yuanwei and Hanzo, Lajos
(2023)
Simultaneously Transmitting and Reflecting (STAR) RIS assisted over-the-air computation systems.
IEEE Transactions on Communications, 71 (3), .
(doi:10.1109/TCOMM.2023.3235915).
Abstract
The performance of over-the-air computation (Air-Comp) systems degrades due to the hostile channel conditions of wireless devices (WDs), which can be significantly improved by the employment of reconfigurable intelligent surfaces (RISs). However, the conventional RISs require that the WDs have to be located in the half-plane of the reflection space, which restricts their potential benefits. To address this issue, the novel family of simultaneously transmitting and reflecting reconfigurable intelligent surfaces (STAR-RIS) is considered in AirComp systems to improve the computation accuracy across a wide coverage area. To minimize the computation mean-squared-error (MSE) in STAR-RIS assisted AirComp systems, we propose a joint beamforming design for optimizing both the transmit power at the WDs, as well as the passive reflect and transmit beamforming matrices at the STAR-RIS, and the receive beamforming vector at the fusion center (FC). Specifically, in the updates of the passive reflect and transmit beamforming matrices, closed-form solutions are derived by introducing an auxiliary variable and exploiting the coupled binary phase-shift conditions. Moreover, by assuming that the number of antennas at the FC and that of elements at the STAR-RIS/RIS are sufficiently high, we theoretically prove that the STAR-RIS assisted AirComp systems provide higher computation accuracy than the conventional RIS assisted systems. Our numerical results show that the proposed beamforming design outperforms the benchmark schemes relying on random phase-shift constraints and the deployment of conventional RIS. Moreover, its performance is close to the lower bound achieved by the beamforming design based on the STAR-RIS dispensing with coupled phase-shift constraints.
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Accepted/In Press date: 4 January 2023
e-pub ahead of print date: 10 January 2023
Published date: 1 March 2023
Additional Information:
Funding Information:
The work of Xiongfei Zhai was supported in part by the Science and Technology Program of Guangzhou under Grant 202102020869, and the Guangdong Basic and Applied Basic Research Foundation under Grants 2022A1515010153 and 2021A1515011645. The work of Guojun Han was supported in part by the Joint Funds of the National Natural Science Foundation of China and Guangdong under Grant U2001203, Key-Area RandD Program of Guangdong Province under Grant 2021B1101270001, and Guangdong Provincial Key Laboratory of Photonics Information Technology under Grant 2020B121201011. The work of Yunlong Cai was supported in part by the National Natural Science Foundation of China under Grants 61971376 and U22A2004. This work of Yuanwei Liu was supported in part by the CHIST-ERA grant under the project CHIST-ERA-20-SICT-005, by the Engineering and Physical Sciences Research Council (EPSRC) under Project EP/W035588/1, in part by the Royal Society under grant RGS\R1\221050 and grant IEC\NSFC\201112, and in part by the PHC Alliance Franco-British Joint Research Program under Grant 822326028. The work of Lajos Hanzo was supported by the Engineering and Physical Sciences Research Council projects EP/W016605/1 and EP/P003990/1 (COALESCE) as well as of the European Research Council’s Advanced Fellow Grant QuantCom (Grant No. 789028)
Publisher Copyright:
© 1972-2012 IEEE.
Keywords:
Array signal processing, Massive MIMO, OFDM, Optimization, Power demand, Synchronization, Wireless communication, simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS), Over-the-air computation (AirComp), internet-of-things (IoT) networks
Identifiers
Local EPrints ID: 474176
URI: http://eprints.soton.ac.uk/id/eprint/474176
ISSN: 0090-6778
PURE UUID: c8933d15-74dd-41c1-8182-44608057246c
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Date deposited: 14 Feb 2023 18:01
Last modified: 18 Mar 2024 02:36
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Contributors
Author:
Xiongfei Zhai
Author:
Guojun Han
Author:
Yunlong Cai
Author:
Yuanwei Liu
Author:
Lajos Hanzo
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