Terahertz communications: Physical layer enablers and analysis
Undoubtedly, spectrum scarcity constitutes the main bottleneck of current wireless networks. It is therefore imperative to move beyond the sub-6 GHz band in order to overcome this limitation. Toward this direction, terahertz (THz) communication is deemed a promising solution for future wireless syst...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/673252 |
| Acceso en línea: | http://hdl.handle.net/10803/673252 |
| Access Level: | acceso abierto |
| Palabra clave: | Beam squint effect Compressive channel estimation Hybrid combining Massive MIMO Planar antenna arrays Wideband THz communications Far-field beamforming Near-field beamfocusing Electromagnetics Intelligent reflecting surfaces Near-field model 62 |
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Terahertz communications: Physical layer enablers and analysis |
| title |
Terahertz communications: Physical layer enablers and analysis |
| spellingShingle |
Terahertz communications: Physical layer enablers and analysis Dovelos, Konstantinos Beam squint effect Compressive channel estimation Hybrid combining Massive MIMO Planar antenna arrays Wideband THz communications Far-field beamforming Near-field beamfocusing Electromagnetics Intelligent reflecting surfaces Near-field model 62 |
| title_short |
Terahertz communications: Physical layer enablers and analysis |
| title_full |
Terahertz communications: Physical layer enablers and analysis |
| title_fullStr |
Terahertz communications: Physical layer enablers and analysis |
| title_full_unstemmed |
Terahertz communications: Physical layer enablers and analysis |
| title_sort |
Terahertz communications: Physical layer enablers and analysis |
| dc.creator.none.fl_str_mv |
Dovelos, Konstantinos |
| author |
Dovelos, Konstantinos |
| author_facet |
Dovelos, Konstantinos |
| author_role |
author |
| dc.contributor.none.fl_str_mv |
Bellalta, Boris Universitat Pompeu Fabra. Departament de Tecnologies de la Informació i les Comunicacions |
| dc.subject.none.fl_str_mv |
Beam squint effect Compressive channel estimation Hybrid combining Massive MIMO Planar antenna arrays Wideband THz communications Far-field beamforming Near-field beamfocusing Electromagnetics Intelligent reflecting surfaces Near-field model 62 |
| topic |
Beam squint effect Compressive channel estimation Hybrid combining Massive MIMO Planar antenna arrays Wideband THz communications Far-field beamforming Near-field beamfocusing Electromagnetics Intelligent reflecting surfaces Near-field model 62 |
| description |
Undoubtedly, spectrum scarcity constitutes the main bottleneck of current wireless networks. It is therefore imperative to move beyond the sub-6 GHz band in order to overcome this limitation. Toward this direction, terahertz (THz) communication is deemed a promising solution for future wireless systems owing to the abundant spectrum resources at these frequencies. Despite the prospect of terabit- per-second wireless links, THz signals suffer from severe propagation losses, which can undermine the communication range and performance of THz systems. In this dissertation, we tackle this challenge by putting forward two key physical layer technologies, namely massive multiple-input multiple-output (MIMO) and intelligent reflecting surfaces (IRSs). More particularly, this dissertation consists of two parts. In the first part, we thoroughly study the spatialwideband effect in THz massive MIMO. We commence by demonstrating that conventional narrowband beamforming/combining leads to substantial performance degradation for large antenna arrays and high transmission bandwidths. With this in mind, we propose a wideband array architecture based on true-timedelay and virtual subarrays. For the channel estimation problem, we introduce a wideband dictionary along with a novel variant of the orthogonal matching pursuit algorithm. Numerical simulations are provided showcasing that the proposed design enables: i) nearly squint-free beamforming/combining with a small number of true-time-delay elements; and ii) accurate channel acquisition with reduced pilot overhead even in the low signal-to-noise-ratio regime. In the second part, we focus on the fundamentals of IRSs at THz frequencies. Specifically, we show that an IRS has the potential to improve the energy efficiency of THz MIMO, when it is placed close to one of the link ends. As a result, electrically large IRSs are expected to operate in the radiating near-field zone, where the spherical wavefront of the emitted electromagnetic (EM) waves cannot be neglected. To this end, we introduce a spherical wave channel model by leveraging EM theory, which includes far-field as special case. Furthermore, we discuss the importance of using EM principles to characterize the path loss of IRS-aided links, as simplistic models may wrongly estimate the link budget and actual system performance. Our analysis reveals that: i) conventional far-field beamforming is highly suboptimal in terms of power gain, and hence beamfocusing is the optimal mode of operation for THz IRSs; and ii) frequencydependent beamfocusing is required in wideband THz transmissions, as beam squint can substantially reduce the achievable data rate. |
| publishDate |
2021 |
| dc.date.none.fl_str_mv |
2021 2022 2022 |
| dc.type.none.fl_str_mv |
info:eu-repo/semantics/doctoralThesis info:eu-repo/semantics/publishedVersion |
| format |
doctoralThesis |
| status_str |
publishedVersion |
| dc.identifier.none.fl_str_mv |
http://hdl.handle.net/10803/673252 |
| url |
http://hdl.handle.net/10803/673252 |
| dc.language.none.fl_str_mv |
Inglés |
| language_invalid_str_mv |
Inglés |
| dc.rights.none.fl_str_mv |
info:eu-repo/semantics/openAccess |
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openAccess |
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84 p. application/pdf application/pdf |
| dc.publisher.none.fl_str_mv |
Universitat Pompeu Fabra |
| publisher.none.fl_str_mv |
Universitat Pompeu Fabra |
| dc.source.none.fl_str_mv |
TDX (Tesis Doctorals en Xarxa) reponame:TDR. Tesis Doctorales en Red instname:CBUC, CESCA |
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CBUC, CESCA |
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TDR. Tesis Doctorales en Red |
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TDR. Tesis Doctorales en Red |
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|
| repository.mail.fl_str_mv |
|
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1869409325939687424 |
| spelling |
Terahertz communications: Physical layer enablers and analysisDovelos, KonstantinosBeam squint effectCompressive channel estimationHybrid combiningMassive MIMOPlanar antenna arraysWideband THz communicationsFar-field beamformingNear-field beamfocusingElectromagneticsIntelligent reflecting surfacesNear-field model62Undoubtedly, spectrum scarcity constitutes the main bottleneck of current wireless networks. It is therefore imperative to move beyond the sub-6 GHz band in order to overcome this limitation. Toward this direction, terahertz (THz) communication is deemed a promising solution for future wireless systems owing to the abundant spectrum resources at these frequencies. Despite the prospect of terabit- per-second wireless links, THz signals suffer from severe propagation losses, which can undermine the communication range and performance of THz systems. In this dissertation, we tackle this challenge by putting forward two key physical layer technologies, namely massive multiple-input multiple-output (MIMO) and intelligent reflecting surfaces (IRSs). More particularly, this dissertation consists of two parts. In the first part, we thoroughly study the spatialwideband effect in THz massive MIMO. We commence by demonstrating that conventional narrowband beamforming/combining leads to substantial performance degradation for large antenna arrays and high transmission bandwidths. With this in mind, we propose a wideband array architecture based on true-timedelay and virtual subarrays. For the channel estimation problem, we introduce a wideband dictionary along with a novel variant of the orthogonal matching pursuit algorithm. Numerical simulations are provided showcasing that the proposed design enables: i) nearly squint-free beamforming/combining with a small number of true-time-delay elements; and ii) accurate channel acquisition with reduced pilot overhead even in the low signal-to-noise-ratio regime. In the second part, we focus on the fundamentals of IRSs at THz frequencies. Specifically, we show that an IRS has the potential to improve the energy efficiency of THz MIMO, when it is placed close to one of the link ends. As a result, electrically large IRSs are expected to operate in the radiating near-field zone, where the spherical wavefront of the emitted electromagnetic (EM) waves cannot be neglected. To this end, we introduce a spherical wave channel model by leveraging EM theory, which includes far-field as special case. Furthermore, we discuss the importance of using EM principles to characterize the path loss of IRS-aided links, as simplistic models may wrongly estimate the link budget and actual system performance. Our analysis reveals that: i) conventional far-field beamforming is highly suboptimal in terms of power gain, and hence beamfocusing is the optimal mode of operation for THz IRSs; and ii) frequencydependent beamfocusing is required in wideband THz transmissions, as beam squint can substantially reduce the achievable data rate.Programa de doctorat en Tecnologies de la Informació i les ComunicacionsUniversitat Pompeu FabraBellalta, BorisUniversitat Pompeu Fabra. Departament de Tecnologies de la Informació i les Comunicacions202220222021info:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/publishedVersion84 p.application/pdfapplication/pdfhttp://hdl.handle.net/10803/673252TDX (Tesis Doctorals en Xarxa)reponame:TDR. Tesis Doctorales en Redinstname:CBUC, CESCAInglésADVERTIMENT. Tots els drets reservats. L'accés als continguts d'aquesta tesi doctoral i la seva utilització ha de respectar els drets de la persona autora. Pot ser utilitzada per a consulta o estudi personal, així com en activitats o materials d'investigació i docència en els termes establerts a l'art. 32 del Text Refós de la Llei de Propietat Intel·lectual (RDL 1/1996). Per altres utilitzacions es requereix l'autorització prèvia i expressa de la persona autora. En qualsevol cas, en la utilització dels seus continguts caldrà indicar de forma clara el nom i cognoms de la persona autora i el títol de la tesi doctoral. No s'autoritza la seva reproducció o altres formes d'explotació efectuades amb finalitats de lucre ni la seva comunicació pública des d'un lloc aliè al servei TDX. Tampoc s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant als continguts de la tesi com als seus resums i índexs.info:eu-repo/semantics/openAccessoai:www.tdx.cat:10803/6732522026-06-14T12:46:07Z |
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15,300724 |