This chapter aims to provide readers with a general vision of 6G. Firstly, we give a simple overview of various aspects related to 6G, including inevitability of 6G research, international organizations for standardization, and also 6G research progress of some countries/regions. Then, 6G spectrum compositions are discussed in detail with emphasis on SUB-6, mmWAVE, and Terahertz (THz).

Millimeter-wave plays an indispensable role in the new generation of mobile communication because of its abundance of unexplored resources, which can be used to meet the requirements of greater bandwidth and ultra-high data rate. This chapter firstly introduces the development, characteristics, and applications of millimeter-wave. Then the application of millimeter-wave in mobile communication systems is described in detail, and the common channel model is listed. Secondly, a large-scale MIMO system, precoding technology, and three kinds of beam forming structures are introduced. Finally, combined with the current development of mobile communication, the requirements on the millimeter-wave devices for the new generation of mobile communication system are summarized, and some typical millimeter-wave devices are listed.

Massive MIMO technology is one of the key technologies of the 6G communication system and the basis of high-speed transmission in the wireless communication network. At the same time, massive MIMO puts forward new requirements for antenna devices in the communication system, such as active integration, miniaturization, broadband, etc. This chapter first reviews the development process and the latest progress of antenna technology in wireless communication. The requirement of a 6G communication network for the base station antenna and the terminal antenna is emphasized. The theoretical basis of massive MIMO technology in the 6G communication system is described in detail, and RIS technology which is closely related to massive MIMO, is introduced. The technical characteristics and development trends of massive MIMO antennas are discussed in detail, including antenna design and synthesis, feed network, and antenna selection technology. Finally, combined with the development of current antenna measurement and calibration technology, the measurement engineering technology closely related to the antenna feeder industry in 6G communication is introduced.

Owing to its ultra-high frequency, the terahertz band becomes one of the candidate bands for 6G communication. In this chapter, the characteristics and application fields of the terahertz wave, especially the application in wireless communication, are introduced in detail. Firstly, the characteristics of the terahertz wave are briefly introduced, and then the terahertz technology, including terahertz devices and the main application fields of the terahertz wave, is introduced. Next, focusing on the application of the terahertz wave in the wireless communication system, it introduces two mainstream terahertz wireless communication systems, describes the key technologies, and finally describes the potential application prospect of the terahertz wave in the wireless mobile communication system.

The Internet of Things (IoT) is a key enabler of smart cities, where a variety of applications proliferate to help citizen services. As different IoT applications have different service holders, it becomes necessary to employ network slicing (NS) to gain distinct virtual networks, and differentiated quality of service (QoS) guarantees. Other than conventional IoT scenarios, smart city IoT relies on 6G networks for broad coverage, ultra-low latency, and reliable connection. This chapter proposes a selforganizing network (SON) driven network slicing architecture, where software-defined networking (SDN) and network function virtualization (NFV) also play important roles. Some preliminary simulation results are given to validate the efficiency of our design.

The Internet of things (IoT) has been the information infrastructure of a digitalized society and drives the newest wave of industrial development. With the rise of smart vehicular IoT applications, such as intelligent transport, smart navigation, and automatic driving, vehicular IoT is gaining some new features that cannot be fully addressed by current 5G networks. This chapter presents an overview of the vehicular IoT developing trend and discusses its relationship to 5G and the coming generation. It also presents some survey results from recent literature on the challenges and promising technologies for vehicular massive IoT.

This chapter gives a systematic introduction to cloud/edge computing and big data system. Cloud computing provides the ability to use flexible and telescopic services for cloud users and could implement through various hosted services provided by the Internet. Edge computing refers to the open platform which uses the network, computing, storage, and application core capabilities on the side of the object or data source and provides the nearest end service to avoid the relatively long delay to reach the data cloud center. Big data technology refers to the analysis of potentially useful information from a large number of data. Analysis of big data can get hidden patterns, unknown relevance, customer trends, and other messages to ensure comprehensive data management. In addition, the speed of 6G is faster, and its service field becomes more extensive compared with the previous generation communication technologies, which makes 6G play a more important or extensive role in the future of the technology field and society. In this regard, the authors also analyze the effect of 6G on cloud/edge computing and big data system. According to the future users' demand for 6G and the characteristics of 6G itself, cloud/edge computing and big data system will play an irreplaceable role in achieving high efficiency and benefits.