Terahertz (THz) band communications is envisioned as a key technology for future wireless standards. Advances in hardware design, channel models, and signal processing have all contributed significantly to advancing the field. Practical THz wireless has been demonstrated in high data-rate backhaul links. However, the next great leap for adopting THz-band frequencies in widespread communication systems must cover a massive canyon. Such communication systems must operate in the massive near field of the high-gain devices that are required to overcome the very high spreading losses of THz frequencies while providing all the promises of very high data rates and sensing resolution. Recent years have seen progress toward near-field THz, with investigations centered around the physical layer, combining both wave and communication theory to provide meaningful solutions to the challenges of THz signal propagation in the near field. In this article, an in-depth look is presented on the aspect of near-field THz. The aspect of signal propagation is first explained from a symbiosis of array and wave theory, following which it is conclusively shown how canonical beamforming is decimated in the near field. It is further explained why THz wireless must necessarily be near field, at least in some cases. Then, a vision of beamshaping is presented in which wavefront engineering is presented to address the design of new beams, specifically beamfocusing, Bessel beams, and Airy beams, which each offer distinct attractive advantages in creating THz links. Issues related to their generation and reception and issues involving narrowband limitations are presented. Finally, the article ends by discussing some of the more promising and upcoming applications of these beams as well as the exciting challenges and opportunities in this new and intriguing research area.
{"title":"Near-Field Terahertz Communications for 6G and Beyond: From concepts to realizations","authors":"Arjun Singh;Vitaly Petrov;Priyangshu Sen;Josep Miquel Jornet","doi":"10.1109/MSP.2024.3496395","DOIUrl":"https://doi.org/10.1109/MSP.2024.3496395","url":null,"abstract":"Terahertz (THz) band communications is envisioned as a key technology for future wireless standards. Advances in hardware design, channel models, and signal processing have all contributed significantly to advancing the field. Practical THz wireless has been demonstrated in high data-rate backhaul links. However, the next great leap for adopting THz-band frequencies in widespread communication systems must cover a massive canyon. Such communication systems must operate in the massive near field of the high-gain devices that are required to overcome the very high spreading losses of THz frequencies while providing all the promises of very high data rates and sensing resolution. Recent years have seen progress toward near-field THz, with investigations centered around the physical layer, combining both wave and communication theory to provide meaningful solutions to the challenges of THz signal propagation in the near field. In this article, an in-depth look is presented on the aspect of near-field THz. The aspect of signal propagation is first explained from a symbiosis of array and wave theory, following which it is conclusively shown how canonical beamforming is decimated in the near field. It is further explained why THz wireless must necessarily be near field, at least in some cases. Then, a vision of beamshaping is presented in which wavefront engineering is presented to address the design of new beams, specifically beamfocusing, Bessel beams, and Airy beams, which each offer distinct attractive advantages in creating THz links. Issues related to their generation and reception and issues involving narrowband limitations are presented. Finally, the article ends by discussing some of the more promising and upcoming applications of these beams as well as the exciting challenges and opportunities in this new and intriguing research area.","PeriodicalId":13246,"journal":{"name":"IEEE Signal Processing Magazine","volume":"42 1","pages":"106-125"},"PeriodicalIF":9.4,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143667500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-20DOI: 10.1109/MSP.2025.3531196
Provides society information that may include news, reviews or technical notes that should be of interest to practitioners and researchers.
提供社会信息，可能包括新闻，评论或技术笔记，从业者和研究人员应该感兴趣。
{"title":"Chapter of the Year and New IEEE Fellows","authors":"","doi":"10.1109/MSP.2025.3531196","DOIUrl":"https://doi.org/10.1109/MSP.2025.3531196","url":null,"abstract":"Provides society information that may include news, reviews or technical notes that should be of interest to practitioners and researchers.","PeriodicalId":13246,"journal":{"name":"IEEE Signal Processing Magazine","volume":"42 1","pages":"12-14"},"PeriodicalIF":9.4,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10934795","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143667550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-20DOI: 10.1109/MSP.2025.3546042
{"title":"SPS Social Media","authors":"","doi":"10.1109/MSP.2025.3546042","DOIUrl":"https://doi.org/10.1109/MSP.2025.3546042","url":null,"abstract":"","PeriodicalId":13246,"journal":{"name":"IEEE Signal Processing Magazine","volume":"42 1","pages":"8-8"},"PeriodicalIF":9.4,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10934777","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143667334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-20DOI: 10.1109/MSP.2025.3527199
Ahmet M. Elbir;Özlem Tuğfe Demir;Kumar Vijay Mishra;Symeon Chatzinotas;Martin Haardt
After nearly a century of specialized applications in optics, remote sensing, and acoustics, the near-field (NF) electromagnetic (EM) propagation zone is experiencing a resurgence in research interest. This renewed attention is fueled by the emergence of promising applications in various fields, such as wireless communications, holography, medical imaging, and quantum-inspired systems. Signal processing within NF sensing and wireless communications environments entails addressing issues related to extended scatterers, range-dependent beampatterns, spherical wavefronts, mutual coupling effects, and the presence of both reactive and radiative fields. Recent investigations have focused on these aspects in the context of extremely large arrays and wide bandwidths, giving rise to novel challenges in channel estimation, beamforming, beam training, sensing, and localization. While NF optics has a longstanding history, advancements in NF phase retrieval (PR) techniques and their applications have lately garnered significant research attention. Similarly, utilizing NF localization with acoustic arrays represents a contemporary extension of established principles in NF acoustic array signal processing. This article aims to provide an overview of state-of-the-art signal processing techniques within the NF domain, offering a comprehensive perspective on recent advances in diverse applications.
{"title":"Near-Field Signal Processing: Unleashing the power of proximity","authors":"Ahmet M. Elbir;Özlem Tuğfe Demir;Kumar Vijay Mishra;Symeon Chatzinotas;Martin Haardt","doi":"10.1109/MSP.2025.3527199","DOIUrl":"https://doi.org/10.1109/MSP.2025.3527199","url":null,"abstract":"After nearly a century of specialized applications in optics, remote sensing, and acoustics, the near-field (NF) electromagnetic (EM) propagation zone is experiencing a resurgence in research interest. This renewed attention is fueled by the emergence of promising applications in various fields, such as wireless communications, holography, medical imaging, and quantum-inspired systems. Signal processing within NF sensing and wireless communications environments entails addressing issues related to extended scatterers, range-dependent beampatterns, spherical wavefronts, mutual coupling effects, and the presence of both reactive and radiative fields. Recent investigations have focused on these aspects in the context of extremely large arrays and wide bandwidths, giving rise to novel challenges in channel estimation, beamforming, beam training, sensing, and localization. While NF optics has a longstanding history, advancements in NF phase retrieval (PR) techniques and their applications have lately garnered significant research attention. Similarly, utilizing NF localization with acoustic arrays represents a contemporary extension of established principles in NF acoustic array signal processing. This article aims to provide an overview of state-of-the-art signal processing techniques within the NF domain, offering a comprehensive perspective on recent advances in diverse applications.","PeriodicalId":13246,"journal":{"name":"IEEE Signal Processing Magazine","volume":"42 1","pages":"20-32"},"PeriodicalIF":9.4,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143667365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As wireless technology begins to utilize physically larger arrays and/or higher frequencies, the transmitter and receiver will reside in each other’s radiative near field. This fact gives rise to unusual propagation phenomena, such as spherical wavefronts and beam focusing, creating the impression that new spatial dimensions—called degrees of freedom (DOF)—can be exploited in the near field. However, this is a fallacy because the theoretically maximum DOF are already achievable in the far field. This article sheds light on these issues by providing a tutorial on spatial frequencies, which are the fundamental components of wireless channels, and by explaining their role in characterizing the DOF in the near and far fields. In particular, we demonstrate how a single propagation path utilizes one spatial frequency in the far field and an interval of spatial frequencies in the near field. We explain how the array geometry determines the number of distinguishable spatial frequency bins and, thereby, the spatial DOF. We also describe how to model near-field multipath channels and their spatial correlation matrices. Finally, we discuss the research challenges and future directions in this field.
{"title":"Spatial Frequencies and Degrees of Freedom: Their roles in near-field communications","authors":"Alva Kosasih;Özlem Tuğfe Demir;Nikolaos Kolomvakis;Emil Björnson","doi":"10.1109/MSP.2024.3511922","DOIUrl":"https://doi.org/10.1109/MSP.2024.3511922","url":null,"abstract":"As wireless technology begins to utilize physically larger arrays and/or higher frequencies, the transmitter and receiver will reside in each other’s radiative near field. This fact gives rise to unusual propagation phenomena, such as spherical wavefronts and beam focusing, creating the impression that new spatial dimensions—called <italic>degrees of freedom</i> (<italic>DOF</i>)—can be exploited in the near field. However, this is a fallacy because the theoretically maximum DOF are already achievable in the far field. This article sheds light on these issues by providing a tutorial on spatial frequencies, which are the fundamental components of wireless channels, and by explaining their role in characterizing the DOF in the near and far fields. In particular, we demonstrate how a single propagation path utilizes one spatial frequency in the far field and an interval of spatial frequencies in the near field. We explain how the array geometry determines the number of distinguishable spatial frequency bins and, thereby, the spatial DOF. We also describe how to model near-field multipath channels and their spatial correlation matrices. Finally, we discuss the research challenges and future directions in this field.","PeriodicalId":13246,"journal":{"name":"IEEE Signal Processing Magazine","volume":"42 1","pages":"33-44"},"PeriodicalIF":9.4,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143667327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-20DOI: 10.1109/MSP.2025.3540344
Tülay Adali
{"title":"Looking Back on My First Year as Editor-in-Chief and Reflecting on the Challenges Ahead","authors":"Tülay Adali","doi":"10.1109/MSP.2025.3540344","DOIUrl":"https://doi.org/10.1109/MSP.2025.3540344","url":null,"abstract":"","PeriodicalId":13246,"journal":{"name":"IEEE Signal Processing Magazine","volume":"42 1","pages":"3-5"},"PeriodicalIF":9.4,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10934751","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143667249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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