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Intelligent Surfaces Empowered Wireless Network: Recent Advances and the Road to 6G
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| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 112 (No. 7) |
| Halaman | : | 724-763 |
| Abstrak | : | Intelligent surfaces (ISs) have emerged as a key technology to empower a wide range of appealing applications for wireless networks, due to their low cost, high energy efficiency, flexibility of deployment, and capability of constructing favorable wireless channels/radio environments. Moreover, the recent advent of several new IS architectures further expanded their electromagnetic functionalities from passive reflection to active amplification, simultaneous reflection, and refraction, as well as holographic beamforming. However, the research on ISs is still in rapid progress and there have been recent technological advances in ISs and their emerging applications that are worthy of a timely review. Thus, in this article, we provide a comprehensive survey on the recent development and advances of ISs-aided wireless networks. Specifically, we start with an overview on the anticipated use cases of ISs in future wireless networks such as 6G, followed by a summary of the recent standardization activities related to ISs. Then, the main design issues of the commonly adopted reflection-based IS and their state-of-the-art solutions are presented in detail, including reflection optimization, deployment, signal modulation, wireless sensing, and integrated sensing and communications. Finally, recent progress and new challenges in advanced IS architectures are discussed to inspire future research. |
Safeguarding Next-Generation Multiple Access Using Physical Layer Security Techniques: A Tutorial
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 112 (No. 9) |
| Halaman | : | 1421-1466 |
| Abstrak | : | Driven by the ever-increasing requirements of ultrahigh spectral efficiency, ultralow latency, and massive connectivity, the forefront of wireless research calls for the design of advanced next-generation multiple access schemes to facilitate the provisioning of these stringent demands. This inspires the embrace of nonorthogonal multiple access (NOMA) in future wireless communication networks. Nevertheless, the support of massive access via NOMA leads to additional security threats due to the open nature of the air interface, the broadcast characteristic of radio propagation, and the intertwined relationship among paired NOMA users. To address this specific challenge, the superimposed transmission of NOMA can be explored as new opportunities for security-aware design; for example, multiuser interference inherent in NOMA can be constructively engineered to benefit communication secrecy and privacy. The purpose of this tutorial is to provide a comprehensive overview of the state-of-the-art physical layer security techniques that guarantee wireless security and privacy for NOMA networks, along with the opportunities, technical challenges, and future research trends. |
The Integrated Sensing and Communication Revolution for 6G: Vision, Techniques, and Applications
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 112 (No. 7) |
| Halaman | : | 676-723 |
| Abstrak | : | Future wireless networks will integrate sensing, learning, and communication to provide new services beyond communication and to become more resilient. Sensors at the network infrastructure, sensors on the user equipment (UE), and the sensing capability of the communication signal itself provide a new source of data that connects the physical and radio frequency (RF) environments. A wireless network that harnesses all these sensing data can not only enable additional sensing services but also become more resilient to channel-dependent effects such as blockage and better support adaptation in dynamic environments as networks reconfigure. In this article, we provide a vision for integrated sensing and communication (ISAC) networks and an overview of how signal processing, optimization, and machine learning (ML) techniques can be leveraged to make them a reality in the context of 6G. We also include some examples of the performance of several of these strategies when evaluated using a simulation framework based on a combination of ray-tracing measurements and mathematical models that mix the digital and physical worlds. |
Next-Generation Multiple Access With Cell-Free Massive MIMO
| Pengarang | : | Mohammadali Mohammadi |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 112 (No. 9) |
| Halaman | : | 1372 - 142 |
| Abstrak | : | To meet the unprecedented mobile traffic demands of future wireless networks, a paradigm shift from conventional cellular networks to distributed communication systems is imperative. Cell-free massive multiple-input multiple-output (CF-mMIMO) represents a practical and scalable embodiment of distributed/network MIMO systems. It inherits not only the key benefits of co-located massive MIMO systems but also the macro-diversity gains from distributed systems. This innovative architecture has demonstrated significant potential in enhancing network performance from various perspectives, outperforming co-located mMIMO and conventional small-cell systems. Moreover, CF-mMIMO offers flexibility in integration with emerging wireless technologies such as full-duplex (FD), nonorthogonal transmission schemes, millimeter-wave (mmWave) communications, ultrareliable low-latency communication (URLLC), unmanned aerial vehicle (UAV)-aided communication, and reconfigurable intelligent surfaces (RISs). In this article, we provide an overview of current research efforts on CF-mMIMO systems and their promising future application scenarios. We then elaborate on new requirements for CF-mMIMO networks in the context of these technological breakthroughs. We also present several current open challenges and outline future research directions aimed at fully realizing the potential of CF-mMIMO systems in meeting the evolving demands of future wireless networks. |
Trends in Channel Coding for 6G
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 112 (No. 7) |
| Halaman | : | 653-675 |
| Abstrak | : | Error correction coding (i.e., channel coding) is a key ingredient of any digital communications system. In mobile wireless communications, channel codes have evolved from simple convolutional codes in Global System for Mobile Communications (GSM) (2G), parallel concatenated (turbo) codes in Universal Mobile Telecommunications Service (UMTS) (3G), and long-term evolution (LTE) (4G), to carefully designed multirate/multilength low-density parity-check (LDPC) codes in 5G, combined with polar codes for short messages on the synchronization channel. Based on this rich history, and by accounting for the technological advances in very large-scale integration, this article will outline some recent trends in channel coding as they may be applied in 6G systems, ranging from novel approaches for short blocklengths such as automorphism ensemble decoding, via ideas of coding for multiple access, to concepts for unified coding schemes that may simplify encoding/decoding hardware at competitive error-correcting performance. |
AI Empowered Wireless Communications: From Bits to Semantics
| Pengarang | : | Zhijin Qin |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 112 (No. 7) |
| Halaman | : | 621-652 |
| Abstrak | : | Artificial intelligence (AI) and machine learning (ML) have shown tremendous potential in reshaping the landscape of wireless communications and are, therefore, widely expected to be an indispensable part of the next-generation wireless network. This article presents an overview of how AI/ML and wireless communications interact synergistically to improve system performance and provides useful tips and tricks on realizing such performance gains when training AI/ML models. In particular, we discuss in detail the use of AI/ML to revolutionize key physical layer and lower medium access control (MAC) layer functionalities in traditional wireless communication systems. In addition, we provide a comprehensive overview of the AI/ML-enabled semantic communication systems, including key techniques from data generation to transmission. We also investigate the role of AI/ML as an optimization tool to facilitate the design of efficient resource allocation algorithms in wireless communication networks at both bit and semantic levels. Finally, we analyze major challenges and roadblocks in applying AI/ML in practical wireless system design and share our thoughts and insights on potential solutions. |
Simultaneously Transmitting and Reflecting Surfaces for Ubiquitous Next-Generation Multiple Access in 6G and Beyond
| Pengarang | : | Xidong Mu |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 112 (No. 9) |
| Halaman | : | 1346-1371 |
| Abstrak | : | The ultimate goal of next generation multiple access (NGMA) is to support massive terminals and facilitate multiple functionalities over the limited radio resources of wireless networks in the most efficient manner possible. However, the random and uncontrollable wireless radio environment is a major obstacle to realizing this NGMA vision. Given the prominent feature of achieving a 360° smart radio environment, simultaneously transmitting and reflecting surfaces (STARS) are emerging as one key enabling technology among the family of reconfigurable intelligent surfaces for NGMA. This article provides a comprehensive overview of the recent research progress of STARS, focusing on fundamentals, performance analysis, and full-space beamforming design, as well as promising employments of STARS in NGMA. In particular, we first introduce the basics of STARS by elaborating on the foundational principles and operating protocols as well as discussing different STARS categories and prototypes. Moreover, we systematically survey the existing performance analysis and beamforming design for STARS-aided wireless communications in terms of diverse objectives and different mathematical approaches. Given the superiority of STARS, we further discuss advanced STARS applications as well as the attractive interplay between STARS and other emerging techniques to motivate future works for realizing efficient NGMA. |
Room-Temperature Selective Metallization Processes Applied to 3D Printed and Flexible Materials for Wireless Sensing
| Pengarang | : | Valentina Palazzi |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 112 (No. 8) |
| Halaman | : | 1065-1090 |
| Abstrak | : | This article describes sensors and radio frequency (RF) components manufactured by applying selective-metallization processes (metal foil tape, liquid metal filling, electro and electroless plating, and surface embossing) to 3-D-printed and flexible dielectric substrates. All these technologies can be implemented at room temperature, thus enabling the adoption of unconventional materials and biopolymers with low glass transition temperatures. In this article, we also describe how the above technologies are used to manufacture wireless transponders for tracking and sensing applications. Several examples of RF components are reported, including antennas, beamforming networks, Doppler radars, and wireless passive transponders based on backscatter radio. Innovative circuit design approaches (such as the via-less approach) are presented and their impact on circuit manufacturing and recyclability is discussed. |
NOMA as the Next-Generation Multiple Access in Nonterrestrial Networks
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 112 (No. 9) |
| Halaman | : | 1303-1345 |
| Abstrak | : | Nonterrestrial networks (NTN) are pivotal, enabling technologies for achieving global and ubiquitous connectivity in the sixth generation (6G) of wireless systems. On the other hand, nonorthogonal multiple access (NOMA) emerges as a promising candidate for the next-generation multiple access (NGMA), designed to enable massive connectivity and improve spectral efficiency. In this article, we investigate the synergy between NTN and NOMA [power-domain NOMA (PD-NOMA)], which are integral in addressing the connectivity challenges of 6G. First, we present an overview of NTN, detailing their types, unique characteristics, and the challenges they face. Then, we explain the foundational principles of NOMA, such as power allocation and access strategies. We, then, argue the suitability of NOMA as an NGMA technology for 6G and how it addresses the specific challenges associated with NTN. Furthermore, we explore the integration and the interplay of NTN and NOMA with emerging technologies such as millimeter-wave (mmWave), terahertz (THz) frequencies, reconfigurable intelligent surfaces (RISs), and integrated sensing and communication (ISAC) systems. These advancements are critical in meeting the 6G requirements for extremely high data rates and improved spectral efficiency, enhancing the overall functionality of NTN and NOMA. We, then, examine how NTN using NOMA can use different architectural frameworks, including cellular, cell-free (CF), ad hoc, and integrated access and backhaul (IAB) systems, and detailed several use cases where the integration of NTN and NOMA could have a significant impact, such as in vehicular communications, the Internet of Things (IoT), urban air mobility (UAM), and achieving global connectivity. To optimize NTN using NOMA, we present a comprehensive overview of the mathematical optimization algorithms and machine learning tools. Finally, we elaborate on the primary challenges associated with merging NTN with NOMA and propose relevant future research avenues. |
3D Printing and Gallium Based Liquid Metal Technologies for Microwave and Millimeter-Wave Components
| Pengarang | : | Hervé Aubert |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 112 (No. 8) |
| Halaman | : | 1051-1064 |
| Abstrak | : | This article presents an overview of 3-D-printed microwave and millimeter-wave components integrating gallium-based (Ga-based) liquid metal (LM). The LM is considered here as a fourth degree of freedom for the design of 3-D-printed antennas, filters, and wireless sensors. The 3-D printing combined with LM technology can be considered as a 4-D printing technology. It can benefit from the advantages offered by 3-D printing technologies (low cost and fast manufacturing) and LM at room temperature (flexibility and reconfigurability). To date, in microwave and millimeter-wave applications, 4-D printing technology is mainly used to achieve the metallization and/or reconfigurability and/or mechanical flexibility of high-frequency 3-D-printed components. |