The University of Southampton
University of Southampton Institutional Repository

Reconfigurable intelligent surfaces relying on non-diagonal phase shift matrices

Reconfigurable intelligent surfaces relying on non-diagonal phase shift matrices
Reconfigurable intelligent surfaces relying on non-diagonal phase shift matrices
Reconfigurable intelligent surfaces (RIS) have been actively researched as a potential technique for future wireless communications, which intelligently ameliorate the signal propagation environment. In the conventional design, each RIS element configures and reflects its received signal independently of all other RIS elements, which results in a diagonal phase shift matrix. By contrast, we propose a novel RIS architecture, where the incident signal impinging on one element can be reflected from another element after an appropriate phase shift adjustment, which increases the flexibility in the design of RIS phase shifts, hence, potentially improving the system performance. The resultant RIS phase shift matrix also has off-diagonal elements, as opposed to the pure diagonal structure of the conventional design. Compared to the state-of-art fully-connected/group-connected RIS structures, our proposed RIS architecture has lower complexity, while attaining a higher channel gain than the group-connected RIS structure, and approaching that of the fully-connected RIS structure. We formulate and solve the problem of maximizing the achievable rate of our proposed RIS architecture by jointly optimizing the transmit beamforming and the non-diagonal phase shift matrix based on alternating optimization and semi-define relaxation (SDR) methods. Moreover, the closed-form expressions of the channel gain, the outage probability and bit error ratio (BER) are derived. Simulation results demonstrate that our proposed RIS architecture results in an improved performance in terms of the achievable rate compared to the conventional architecture, both in single-user as well as in multi-user scenarios.
Array signal processing, Matrix converters, Optimization, Power system reliability, Reconfigurable intelligent surfaces (RIS), Rician channels, Simulation, Transmission line matrix methods, average bit error ratio (BER), channel gain, joint beamforming, outage probability
0018-9545
6367-6383
Li, Qingchao
69625501-d192-4a81-861f-f7ac9dd1e882
El-Hajjar, Mohammed
3a829028-a427-4123-b885-2bab81a44b6f
Hemadeh, Ibrahim
11f27b54-e3da-4699-bc72-9a3508e76ccf
Shojaeifard, Arman
fdf8f97f-8675-427e-831a-c54ec3c69824
Mourad, Alain
7a39422e-4c9b-4f76-8653-8551ec8cfb4b
Clerckx, Bruno
3f83190f-c8a4-447c-ab89-3f1e1df43ac1
Hanzo, Lajos
66e7266f-3066-4fc0-8391-e000acce71a1
Li, Qingchao
69625501-d192-4a81-861f-f7ac9dd1e882
El-Hajjar, Mohammed
3a829028-a427-4123-b885-2bab81a44b6f
Hemadeh, Ibrahim
11f27b54-e3da-4699-bc72-9a3508e76ccf
Shojaeifard, Arman
fdf8f97f-8675-427e-831a-c54ec3c69824
Mourad, Alain
7a39422e-4c9b-4f76-8653-8551ec8cfb4b
Clerckx, Bruno
3f83190f-c8a4-447c-ab89-3f1e1df43ac1
Hanzo, Lajos
66e7266f-3066-4fc0-8391-e000acce71a1

Li, Qingchao, El-Hajjar, Mohammed, Hemadeh, Ibrahim, Shojaeifard, Arman, Mourad, Alain, Clerckx, Bruno and Hanzo, Lajos (2022) Reconfigurable intelligent surfaces relying on non-diagonal phase shift matrices. IEEE Transactions on Vehicular Technology, 71 (6), 6367-6383. (doi:10.1109/TVT.2022.3160364).

Record type: Article

Abstract

Reconfigurable intelligent surfaces (RIS) have been actively researched as a potential technique for future wireless communications, which intelligently ameliorate the signal propagation environment. In the conventional design, each RIS element configures and reflects its received signal independently of all other RIS elements, which results in a diagonal phase shift matrix. By contrast, we propose a novel RIS architecture, where the incident signal impinging on one element can be reflected from another element after an appropriate phase shift adjustment, which increases the flexibility in the design of RIS phase shifts, hence, potentially improving the system performance. The resultant RIS phase shift matrix also has off-diagonal elements, as opposed to the pure diagonal structure of the conventional design. Compared to the state-of-art fully-connected/group-connected RIS structures, our proposed RIS architecture has lower complexity, while attaining a higher channel gain than the group-connected RIS structure, and approaching that of the fully-connected RIS structure. We formulate and solve the problem of maximizing the achievable rate of our proposed RIS architecture by jointly optimizing the transmit beamforming and the non-diagonal phase shift matrix based on alternating optimization and semi-define relaxation (SDR) methods. Moreover, the closed-form expressions of the channel gain, the outage probability and bit error ratio (BER) are derived. Simulation results demonstrate that our proposed RIS architecture results in an improved performance in terms of the achievable rate compared to the conventional architecture, both in single-user as well as in multi-user scenarios.

Text
2203.08184 - Accepted Manuscript
Download (1MB)

More information

Accepted/In Press date: 15 March 2022
Published date: 1 June 2022
Additional Information: arXiv:2203.08184
Keywords: Array signal processing, Matrix converters, Optimization, Power system reliability, Reconfigurable intelligent surfaces (RIS), Rician channels, Simulation, Transmission line matrix methods, average bit error ratio (BER), channel gain, joint beamforming, outage probability

Identifiers

Local EPrints ID: 456110
URI: http://eprints.soton.ac.uk/id/eprint/456110
ISSN: 0018-9545
PURE UUID: e2b63a6b-69ae-4b99-b3b5-3d8e3aee911c
ORCID for Qingchao Li: ORCID iD orcid.org/0000-0003-4928-334X
ORCID for Mohammed El-Hajjar: ORCID iD orcid.org/0000-0002-7987-1401
ORCID for Lajos Hanzo: ORCID iD orcid.org/0000-0002-2636-5214

Catalogue record

Date deposited: 26 Apr 2022 14:51
Last modified: 18 Mar 2024 03:59

Export record

Altmetrics

Contributors

Author: Qingchao Li ORCID iD
Author: Mohammed El-Hajjar ORCID iD
Author: Ibrahim Hemadeh
Author: Arman Shojaeifard
Author: Alain Mourad
Author: Bruno Clerckx
Author: Lajos Hanzo ORCID iD

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×