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Reconfigurable Intelligent Surfaces and Polarization for Future Wireless Communication and Localization Systems
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.ORCID iD: 0000-0002-9170-3240
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Reconfigurable intelligent surface (RIS) is considered as a promising technology for future wireless communication, localization and sensing systems. An RIS is a thin planar array that consists of multiple sub-wavelength-sized reflecting elements, each of which can induce independent and controllable interactions with the incident signal. An RIS can actively control the propagation channel, creating energy-efficient smart radio environments. Meanwhile, polarization is a fundamental property of electromagnetic (EM) waves; it refers to the orientation of the electric field component relative to the direction of propagation. The EM polarization provides additional degrees of freedom (DoF) to the wireless channel beyond the well-exploited time, frequency, and spatial dimensions.

In this thesis, we explore the RIS technology and EM polarization as two potential key enablers for future wireless communication and localization systems. First, we exploit the RIS technology to address a fundamental bottleneck for point-to-point multiple-input multiple-output (MIMO) communications in line-of-sight environments. Specifically, we deploy multiple RISs as controllable scatterers to create an artificial scattering environment, thereby providing additional spatial DoF and restoring the spatial multiplexing gain of MIMO systems.

Second, we present two studies that focus on the RIS operation regarding its efficient position of deployments and the channel state information acquisition. In the former study, we analyze the positional impact of the RIS on the achievable rate for single and multiple antenna systems. We consider not only the impact of propagation losses but also the impact of channel richness with multipath components to identify the efficient region of RIS deployments. In the latter study, we develop two distinct channel estimation schemes based on the superimposed pilot signals to reduce the significant pilot overhead required in RIS-aided wideband multi-user communications. Then, we incorporate iterative channel estimation and data detection techniques. Furthermore, we develop an RIS reflection design using an alternating optimization to maximize channel power.

Third, we unlock the RIS capability to control the polarization states of reflected signals by considering dual-polarized RIS. We utilize the RIS as an information modulator by performing three distinct polarization-based modulation schemes: binary polarization modulation, joint differential polarization and phase modulation, and joint polarization and spatial modulation. 

Finally, we study the potential benefits of integrating the polarization dimension into localization applications. We identify the DoF provided by polarization for localization. Subsequently, we leverage these DoF to introduce three distinct localization applications which enable three dimensional (3D) orientation estimation, 2D angle of departure estimation, and mixed 2D position and 1D orientation estimation for vehicular scenarios.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2024.
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords [en]
Wireless Communications, Signal Processing, Localization, Reconfigurable Intelligent Surfaces, Electromagnetic Polarization, MIMO, Polarization Modulation, Spatial Modulation, Differential Modulation, Channel Estimation, OFDM, massive MIMO, Positioning, 3D Orientation Estimation
National Category
Telecommunications Signal Processing
Research subject
Signal Processing
Identifiers
URN: urn:nbn:se:ltu:diva-110068ISBN: 978-91-8048-638-5 (print)ISBN: 978-91-8048-639-2 (electronic)OAI: oai:DiVA.org:ltu-110068DiVA, id: diva2:1900179
Public defence
2024-11-19, E632, Luleå University of Technology, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2024-09-23 Created: 2024-09-23 Last updated: 2024-10-29Bibliographically approved
List of papers
1. Intelligent Reflecting Surfaces for MIMO Communications in LoS Environments
Open this publication in new window or tab >>Intelligent Reflecting Surfaces for MIMO Communications in LoS Environments
2021 (English)In: 2021 IEEE Wireless Communications and Networking Conference (WCNC), IEEE, 2021Conference paper, Published paper (Refereed)
Abstract [en]

In line-of-sight (LoS) environments, point-to-point (P2P) multiple-input multiple-output (MIMO) channel matrix turns out to be rank deficient such that spatial multiplexing becomes unattainable. In this paper, we propose the deployment of distributed intelligent reflecting surfaces (IRSs) to act as artificial scatterers and synthesize a sort of multi-path propagation such that additional degrees of freedom are created. We show that given the far-field deployment of the IRS, it simply resembles a full-duplex relay with a single effective reflection coefficient. However, to maximize the channel capacity both the effective reflection coefficients of all IRSs and the transmit covariance matrix should be jointly optimized, which is a nonconvex optimization problem. Thus, we develop an alternating optimization algorithm to iteratively find a sub-optimal solution. Moreover, we propose different schemes to enhance the composite channel power which would result in an improvement to the achievable rate. Our simulation results show that the deployment of distributed IRSs with P2P MIMO systems in LoS environments increases the rank of the channel matrix, and improves the achievable rate by making spatial multiplexing possible.

Place, publisher, year, edition, pages
IEEE, 2021
Series
IEEE Conference on Wireless Communications and Networking, E-ISSN 1558-2612
Keywords
Intelligent reflecting surface, MIMO, line-of-sight
National Category
Telecommunications
Research subject
Signal Processing
Identifiers
urn:nbn:se:ltu:diva-84182 (URN)10.1109/WCNC49053.2021.9417270 (DOI)000704226500043 ()2-s2.0-85115809696 (Scopus ID)
Conference
IEEE Wireless Communications and Networking Conference (WCNC 2021), Najing, China (Hybrid on-line), March 29-April 1, 2021
Note

ISBN för värdpublikation: 978-1-7281-9505-6

Available from: 2021-05-07 Created: 2021-05-07 Last updated: 2024-09-23Bibliographically approved
2. On the Position of Intelligent Reflecting Surfaces
Open this publication in new window or tab >>On the Position of Intelligent Reflecting Surfaces
2021 (English)In: 2021 Joint European Conference on Networks and Communications & 6G Summit (EuCNC/6G Summit), IEEE, 2021, p. 66-71Conference paper, Published paper (Refereed)
Abstract [en]

We study the positional impact of an intelligent reflecting surface (IRS) on the achievable rate for single and multiple antenna systems. We show that in IRS-aided single antenna systems, it is always best to place the IRS as close as possible to the transmitter or receiver since the large-scale fading for IRS-reflected links is the main factor that characterizes the performance gain. However, for IRS-aided multiple antenna systems, the propagation environment has an important role in characterizing the efficient regions of IRS placement. In the case of a line-of-sight environment, the channel matrix turns out to be rank-deficient. Thus, both far and near IRS placements result in significant achievable rate improvements where the former provides a substantial additional degree-of-freedom, while the latter results in a power gain. Furthermore, as the wireless channel becomes richer with multipath, the rank of the channel matrix increases. Thus, the efficient far placement regions gradually shrink until they disappear in the case of a Rayleigh fading channel where IRS near placements become more efficient than far placements as they result in higher power gains.

Place, publisher, year, edition, pages
IEEE, 2021
Series
European Conference on Networks and Communications (EuCNC), E-ISSN 2575-4912
Keywords
Intelligent reflecting surface, Position analysis
National Category
Signal Processing
Research subject
Signal Processing
Identifiers
urn:nbn:se:ltu:diva-86487 (URN)10.1109/EuCNC/6GSummit51104.2021.9482610 (DOI)000698755200012 ()2-s2.0-85112649725 (Scopus ID)
Conference
2021 Joint European Conference on Networks and Communications & 6G Summit (EuCNC/6G Summit), Porto, Portugal, June 8-11, 2021
Note

ISBN av värdpublikation: 978-1-6654-1526-2; 978-1-6654-1525-5; 978-1-6654-3021-0

Available from: 2021-07-29 Created: 2021-07-29 Last updated: 2024-09-23Bibliographically approved
3. Channel Estimation based on Superimposed Pilots for RIS-aided Massive MIMO-OFDM Systems
Open this publication in new window or tab >>Channel Estimation based on Superimposed Pilots for RIS-aided Massive MIMO-OFDM Systems
(English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248Article in journal (Other academic) Submitted
National Category
Telecommunications Signal Processing
Research subject
Signal Processing
Identifiers
urn:nbn:se:ltu:diva-110067 (URN)
Available from: 2024-09-23 Created: 2024-09-23 Last updated: 2024-10-18
4. Binary Polarization Shift Keying with Reconfigurable Intelligent Surfaces
Open this publication in new window or tab >>Binary Polarization Shift Keying with Reconfigurable Intelligent Surfaces
2022 (English)In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 11, no 5, p. 908-912Article in journal (Refereed) Published
Abstract [en]

We propose a novel binary polarization shift keying modulation scheme for a line-of-sight environment by exploiting the polarization control ability of the reconfigurable intelligent surface (RIS). The RIS encodes the information data in terms of the polarization states of either the reflected wave from the RIS or the composite wireless channel between an RF source and receiver. In the first case, polarization mismatch correction becomes essential at the receiver. In the second case, the RIS pre-codes the reflected wave to compensate for the polarization mismatch which allows non-coherent demodulation at the receiver.

Place, publisher, year, edition, pages
IEEE, 2022
Keywords
Reconfigurable intelligent surface, Polarization shift keying
National Category
Telecommunications Communication Systems
Research subject
Signal Processing
Identifiers
urn:nbn:se:ltu:diva-88772 (URN)10.1109/LWC.2022.3149618 (DOI)000793809500010 ()2-s2.0-85124731655 (Scopus ID)
Funder
Interreg Nord
Note

Validerad;2022;Nivå 2;2022-05-30 (johcin)

Available from: 2022-01-13 Created: 2022-01-13 Last updated: 2024-09-23Bibliographically approved
5. RIS-Assisted Joint Differential Polarization and Phase Modulation for Non-Coherent Receivers
Open this publication in new window or tab >>RIS-Assisted Joint Differential Polarization and Phase Modulation for Non-Coherent Receivers
2024 (English)In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345Article in journal (Refereed) Epub ahead of print
Abstract [en]

This letter introduces a reconfigurable intelligent surface (RIS)-assisted modulation scheme tailored for non-coherent receivers. Employing a RIS of dual-polarized elements, we manipulate the polarization state of the reflected signals to enable a differential polarization shift keying modulation scheme while simultaneously beamforming the reflected signal towards the receiver. Subsequently, an additional differential phase shift keying (DPSK) modulation layer is superimposed under two distinct deployments, where either the source or the RIS performs the DPSK modulation. Furthermore, the analytical performance is investigated, and a comparison with benchmark schemes is evaluated.

Place, publisher, year, edition, pages
IEEE, 2024
Keywords
Reconfigurable intelligent surface, differential polarization modulation, and differential phase modulation
National Category
Telecommunications Signal Processing
Research subject
Signal Processing
Identifiers
urn:nbn:se:ltu:diva-110049 (URN)10.1109/LWC.2024.3496257 (DOI)2-s2.0-85209347448 (Scopus ID)
Note

Full text license: CC BY;

Funder: European Project Hexa-X-II (101095759); InterReg Aurora project Arctic 6G;

Available from: 2024-09-20 Created: 2024-09-20 Last updated: 2024-11-25
6. Joint Polarization and Spatial Modulation Using Reconfigurable Intelligent Surface
Open this publication in new window or tab >>Joint Polarization and Spatial Modulation Using Reconfigurable Intelligent Surface
2024 (English)In: 2024 IEEE Wireless Communications and Networking Conference (WCNC), IEEE, 2024Conference paper, Published paper (Refereed)
Abstract [en]

We propose a joint polarization and spatial modulation (JPSM) scheme using reconfigurable intelligent surface (RIS). In this scheme, a RIS equipped with dual-polarized (DP) reflecting elements is used to assist the communication between a transmitter of a single polarized antenna and a receiver equipped with a uniform linear array of DP antennas, while additionally encoding the reflected waves on the RIS to perform JPSM scheme. The information data is encoded in terms of the receiver DP antenna index as well as the polarization state of the received signal. Furthermore, we develop exhaustive and heuristic RIS phase shift design solutions to enable the RIS-JPSM scheme. Moreover, both an optimum maximum likelihood and a low complexity greedy detectors are formulated. The proposed scheme enhances the data rate by operating higher-order polarization modulation in comparison to the conventional RIS-based spatial modulation scheme.

Place, publisher, year, edition, pages
IEEE, 2024
Keywords
polarization modulation, Reconfigurable intelligent surface, spatial modulation
National Category
Telecommunications Communication Systems Signal Processing
Research subject
Signal Processing
Identifiers
urn:nbn:se:ltu:diva-108636 (URN)10.1109/WCNC57260.2024.10570637 (DOI)001268569300133 ()2-s2.0-85198845448 (Scopus ID)
Conference
25th IEEE Wireless Communications and Networking Conference (WCNC 2024), Dubai, United Arab Emirates, April 21-24, 2024
Note

ISBN for host publication: 979-8-3503-0358-2; 

Available from: 2024-08-20 Created: 2024-08-20 Last updated: 2024-11-20Bibliographically approved
7. Inferring Direction and Orientation From Polarized Signals: Feasibility and Bounds
Open this publication in new window or tab >>Inferring Direction and Orientation From Polarized Signals: Feasibility and Bounds
Show others...
2024 (English)In: IEEE Open Journal of the Communications Society, E-ISSN 2644-125X, Vol. 5, p. 6033-6047Article in journal (Refereed) Published
Abstract [en]

Polarization is a fundamental property of electromagnetic radio signals but often neglected in localization studies. In this paper, we study the potential benefits of integrating the polarization dimension into localization applications. We develop a three-dimensional (3D) geometric channel model between a base station (BS) and user equipment (UE), both equipped with dual-polarized (DP) antennas, which offers fundamental insights into the angles of departure (AoD) from the BS to the UE as well as the 3D orientation of the UE. From the model, we identify the degrees of freedom (DoF) provided by the polarization dimension for localization solutions by evaluating the rank of the equivalent Fisher information matrix. Subsequently, we leverage these DoF to introduce three distinct localization applications: (i) 3D orientation estimation, (ii) 2D AoD estimation, and (iii) mixed 2D position and 1D orientation estimation for vehicular scenarios. Furthermore, for the three localization applications we identify their regions of operation in terms of the ranges of the angles of interest, to avoid any ambiguity occurrence through the estimation process, thereby guaranteeing unique solutions. Finally, we derive the Cramér-Rao lower bounds and numerically establish the efficiency of the proposed estimators.

Place, publisher, year, edition, pages
IEEE, 2024
Keywords
Polarization, Localization, 3D Orientation Estimation
National Category
Signal Processing
Research subject
Signal Processing
Identifiers
urn:nbn:se:ltu:diva-110050 (URN)10.1109/ojcoms.2024.3462689 (DOI)001322071500004 ()2-s2.0-85204462130 (Scopus ID)
Funder
Interreg Aurora, Arctic-6G
Note

Validerad;2024;Nivå 1;2024-11-14 (hanlid);

Full text license: CC BY;

Funder: European Project Hexa-X II (101095759)

Available from: 2024-09-20 Created: 2024-09-20 Last updated: 2024-11-20Bibliographically approved

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