TUT-01: A Primer on Non-terrestrial Networks: Connecting the Dots between Ground, Air, and Space
Giovanni Geraci (University Pompeu Fabra)
Adrian Garcia-Rodriguez (Ericsson R&D, France)
Next-generation wireless networks are envisioned to break the boundaries of the current ground- focused paradigm and fully embrace aerial and spaceborne communications. In a quest for anything, anytime, anywhere connectivity, this vertical (r)evolution entails defining a new intelligently integrated network architecture and characterizing its fundamental limits. While the technological and societal implications would be of the greatest long-term significance, important hurdles must be overcome to optimally orchestrate the integrated ground-air-space mobile network of tomorrow. In light of the unprecedented interest in this field, this one-of-a-kind tutorial blends our academic and industrial views to take a holistic approach to non-terrestrial mobile communications. We will discuss: Connectivity requirements for UAVs in 2030; tangible performance results and novel research questions on next-generation aerial communications in microwave, mmWave, and THz bands. Fresh updates on the non-terrestrial networks within the 3GPP, including use cases and deployments, architecture, channel modeling, and technical challenges. A well-grounded forecast of the potential and design challenges of the future 6G ground-air-space mobile network, jointly orchestrated for direct access, relayed fixed broadband, and IoT support.
TUT-02: Near-Field XL-MIMO for 6G: Challenges, Solutions, and Opportunities
Linglong Dai (Tsinghua University, China)
Compared with massive MIMO for current 5G systems, extremely large-scale MIMO (XL-MIMO), where the antenna number is further increased, is a promising technology to achieve the very high spectrum efficiency of Kbps/Hz for future 6G communications. However, the change from massive MIMO for 5G to XL-MIMO for 6G not only means the increase in antenna number, but also leads to the fundamental change of the electromagnetic field property. With a very large number of antennas, the near-field property of XL-MIMO systems becomes dominant. In this tutorial, the near-field effect, a new electromagnetic property distinguishing XL-MIMO from massive MIMO, will be discussed. Specifically, this tutorial will first introduce the background and advantages of XL-MIMO for 6G. Then, the physical foundation and properties of the near-field for XL-MIMO will be explained. Based on the fundamental of near-field effect, three typical cases will be elaborated to present the advanced XL-MIMO techniques. For the first case, we will introduce the property of near-field beam focusing, where near-field beams focus the signal energy on the desired locations instead of desired angles as far-field beams. Thus, the far-field beam forming for multi-user communications cannot be directly utilized in the near-field scenario. To solve this problem, the near-field multi-users communications design based on the property of near-field beam focusing is presented. Then, the near-field wideband effect for XL-MIMO will be explained, based on which we will show that this effect dramatically decreases the actual transmission rates of XL-MIMO systems. To address this new challenge, this tutorial will discuss how to develop advanced transmission techniques to make practical XL-MIMO work. Particularly, this tutorial will also illustrate that the near-field wideband effect not only introduces challenges but also brings opportunities for XL-MIMO, which leads to the change of design paradigm of future 6G communications. Finally, for the last case, a new favorable phenomenon will be introduced, where the degrees of freedom (DoFs) increase in the near-field channel. Accordingly, the capacity of the near-field channel will be analyzed theoretically based on the near-field DoFs. The corresponding precoding and channel estimation schemes are also introduced.
TUT-03: Evolution of NOMA Toward Next Generation Multiple Access
Zhiguo Ding (The University of Manchester, UK)
Yuanwei Liu (Queen Mary University of London, UK)
User data traffic, especially a large amount of video traffic and small-size internet-of-things (IoT) packets, has dramatically increased in recent years with the emergence of smart devices, smart sensors and various new applications such as virtual reality and autonomous driving. It is hence crucial to increase network capacity and user access to accommodate these bandwidth consuming applications and enhance the massive connectivity. As a prominent member of the next generation multiple access (NGMA) family, non-orthogonal multiple access (NOMA) has been recognized as a promising multiple access candidate for the sixth-generation (6G) networks. The main content of this tutorial is to discuss the so-called “One Basic Principle plus Four New” concept. Starting with the basic NOMA principle to explore the possible multiple access techniques in non-orthogonal manner, the advantages and drawbacks of both the channel state information based successive interference cancelations (SIC) and quality-of- service based SIC are discussed. Then, the application of NOMA to meet the new 6G performance requirements, especially for massive connectivity, is explored. Furthermore, the integration of NOMA with new physical layer techniques is considered, followed by introducing new application scenarios for NOMA towards 6G. Finally, the application of machine learning in NOMA networks is investigated, ushering in the machine learning empowered NGMA era, for making multiple access in an intelligent manner for the next generation networks.
TUT-04: Holographic Radio: A New Paradigm for Ultra-Massive MIMO
Boya Di (Peking University, China)
Hongliang Zhang (Princeton University, USA)
Lingyang Song (Peking University, China)
To enable a ubiquitous intelligent information network, the forthcoming sixth generation (6G) wireless communications are expected to provide revolutionary mobile connectivity and high-throughput data services through ultra-massive multiple input multiple output (MIMO). Widely-utilized phased arrays relying on costly components make the implementation of ultra-massive MIMO in practice become prohibitive from both cost and power consumption perspectives. The recently developed reconfigurable holographic surfaces (RHSs) composing of densely packing sub-wavelength metamaterial elements can achieve holographic beamforming without costly hardware components. By leveraging the holographic principle, the RHS serves as an ultra-thin and lightweight surface antenna integrated with the transceiver, thereby providing a promising alternative to phased arrays. In this tutorial, we will first provide a basic introduction of RHSs. We then introduce the unique features of RHSs which enable ultra-massive MIMO for both communication and sensing, in a comprehensive way. Related design, analysis, optimization, and signal processing techniques will be presented. Typical RHS-based applications for both wireless communications and radio-frequency sensing will be explored. The implementation issues along with our developed prototypes and experiments will also be discussed. Formalized analysis of several up-to-date challenges and technical details on system design will be provided for different applications.
TUT-05: 6G Wireless Channels: Measurements, Parameter Estimation, Characteristics
Cheng-Xiang Wang (Southeast University, China)
Jie Huang (Southeast University, China)
Haiming Wang (Southeast University, China)
Harald Haas (University of Strathclyde, UK)
For the design, performance evaluation, and optimization of wireless communication systems, channel measurements, parameter estimation, characteristics analysis, and realistic channel models with good accuracy-complexity-generality trade-off are indispensable. The proposed tutorial is intended to offer a comprehensive and in-depth course to communication professionals/academics, aiming to address recent advances and future challenges on channel measurements and models for sixth generation (6G) wireless communication systems. Network architecture and key technologies for 6G that will enable global coverage, all spectra, and full applications will be first discussed. Channel measurements and non-predictive channel models are then reviewed for challenging 6G scenarios and frequency bands, focusing on shortwave, millimeter wave (mmWave), terahertz (THz), and optical wireless communication channels under all spectra, satellite, unmanned aerial vehicle (UAV), maritime, and underwater acoustic communication channels under global coverage scenarios, and high-speed train (HST), vehicle-to-vehicle (V2V), ultra-massive multiple-input multiple-output (MIMO), reconfigurable intelligent surface (RIS), industry Internet of things (IoT), and orbital angular momentum (OAM) communication channels under full application scenarios. New machine learning based predictive channel models will also be investigated. A non-predictive 6G pervasive channel model will then be proposed, which is expected to serve as a baseline for future standardized 6G channel models. Future research challenges and trends for 6G channel measurements and models will be discussed in the end of the tutorial.
TUT-06: Digital Twin for 6G
Yan Zhang (University of Oslo, Norway)
In this tutorial, we will present basic concepts related to digital twin for 6G and key enabling technologies with respect to communications, computation, machine learning, and cyber-physical optimization. We will first introduce the main concepts and challenges related to Digital Twin (DT) and we will provide a thorough perspective on why and how DT can be adapted for 6G. Then, we present a novel scenario DITEN (Digital Twin Edge Networks) and the research challenges related to offloading and edge association. In this scenario, we will focus on resource allocation, system models and optimization problems, and various offloading and edge association techniques. Next, we will present DT and machine learning to add intelligence and present our ideas on utilizing deep learning (deep reinforcement learning, federated learning) for low-latency, privacy-preservation, energy-efficiency and Quality-of-Service in 6G networks. We will further present DT in Air-Ground 6G networks which is essential for next-generation satellite-air- ground integrated networks. The approach and the solutions in this context will result in highly efficient interconnection and synergy among various types of components in 6G networks and its applications. Finally, we will point out several promising research directions related to Intelligent Reflecting Surface (IRS), blockchain intelligence, and deep learning.
TUT-07: Age of Information Optimizations in Wireless Networks: Theories, Applications, and Beyond
Zhiyuan Jiang (Shanghai University, China)
Sheng Zhou (Tsinghua University, China)
Howard H. Yang (Zhejiang University, China)
Meng Zhang (Zhejiang University, China)
Nikolaos Pappas (Linköping University, Sweden)
In this tutorial, we provide an extensive overview of recent research advances in Age of Information (AoI). In particular, we focus on AoI optimizations in wireless networks, including optimal algorithm design and more real-world applications. We start with the concept of AoI, emphasizing the key differences between AoI and conventional end-to-end latency, followed by several applications exploiting the AoI concept. To gain more insights on the concept of AoI, we present the fundamental analysis of AoI in various queueing models. After introducing the concept and the fundamental analysis of AoI, we discus several important AoI optimizations in wireless networks in a systematic way. Our discussions are comprehensive, encompassing various network topologies and system settings (e.g., centralized or decentralized, stochastic or adversarial, as well as economic approaches that include pricing and mechanism design). Moreover, we present cellular V2X enabled autonomous driving, i.e., intersection management and platooning, as a real-world example to validate our AoI optimal algorithms.
TUT-08: RIS Empowered Intelligent Communications, Sensing, and Computation
Chongwen Huang (Zhejiang University, China)
Liang Liu (The Hong Kong Polytechnic University, Hong Kong)
Zhaohui Yang (University College London, UK)
Zhaoyang Zhang (Zhejiang University, China)
Future 6G wireless communication systems are expected to realize an intelligent communication, sensing, computing and software reconfigurable functionality paradigm, where all parts of device hardware will adapt to the changes of the wireless environment, and provide various high-accuracy sensing services, positioning, etc. Furthermore. with the rapid development of wireless networks and Internet of things (IoT), emerging applications continue to appear, such as artificial intelligence (AI) task, immersive service, and digital twins. Those emerging applications have put forward higher demands on sixth generation (6G) networks for end-to- end information processing capabilities. In order to meet the higher performance demands, 6G will be an end- to-end information processing and service system, and its core functions will expand from information transmission to information collection, information computing and information application, providing stronger sensing, communication, and computation capabilities. Thus, this has led to the emergence of a fast-growing area, called joint sensing, communications, and computation. It is widely expected that the advancements in joint sensing, communications, and computation would provide a platform for implementing AI in 6G systems and solving large-scale problems in our society ranging from autonomous driving to personalized healthcare. However, one fundamental problem is how we implement AI, sensing, computing into the wireless communications. In the recent period, a brand-new technology was brought to the attention of the wireless research community, the “Reconfigurable intelligent surfaces (RIS)”. Following the recent breakthrough on the fabrication of programmable metamaterials, reconfigurable intelligent meta-surfaces have the potential to materialize the intelligent software-based control of the environment in wireless communication systems, when coated on the otherwise passive surfaces of various objects. Being a newly proposed concept going beyond massive MIMO, intelligent surfaces are low cost, ultra-thin, light weight, and low power consumption hardware structures that provide a transformative means of the wireless environment into a programmable smart entity. Therefore, we expect that to implement the ubiquitous intelligence, sensing, computing by leveraging the advance of the RIS. Achieving the goal of RIS-empowered joint communications, sensing, and computation with high communication efficiencies calls for the designs of new wireless techniques based on a sensing- communication-and-learning integration approach. The observation of the recent surge in relevant research and the emergence of many exciting opportunities motivate us to propose the tutorial of “RIS-empowered Joint communications, sensing, and Computation”. Thereby, this tutorial will seek to provide a comprehensive introduction to RIS-empowered sensing and computing over wireless communications while delineating the potential opportunities, roadblocks, and challenges.