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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Serie: Wiley - IEEE
- Sprache: Englisch
6G Key Technologies An accessible and integrated roadmap to the technologies enabling 6G development In 6G Key Technologies: A Comprehensive Guide, two internationally well-recognized experts deliver a thoroughly original and comprehensive exploration of the technologies enabling and contributing to the development of 6G. The book presents the vision of 6G by reviewing the evolution of communications technologies toward 6G and examining the factors driving that development, as well as their requirements, use cases, key performance indicators, and more. Readers will discover: * Thorough introductions to the standardization and technology evolution toward 6G, as well as the vision behind the development of 6G in terms of architectures, algorithms, protocols, and applications. * In-depth explorations of full-spectrum wireless technologies in 6G, including enhanced millimeter wave technologies, terahertz-based communications and networking, visible-light and optical wireless communications. * Fulsome discussions of smart radio networks and new air interface technologies for 6G including intelligent reflecting surface, cellular massive MIMO, cell-free massive MIMO, adaptive and non-orthogonal multiple access technologies. Perfect for professional engineers, researchers, manufacturers, network operators, and software developers, 6G Key Technologies: A Comprehensive Guide will also earn a place in the libraries of graduate students studying in wireless communications, artificial intelligence, signal processing, microwave technology, information theory, antenna and propagation, system-on-chip implementation, and computer networks.
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Table of Contents
Cover
Title Page
Copyright
Preface
List of Abbreviations
Part I: The Vision of 6G and Technical Evolution
1 Standards History of Cellular Systems Toward 6G
1.1 0G: Pre‐Cellular Systems
1.2 1G: The Birth of Cellular Network
1.3 2G: From Analog to Digital
1.4 3G: From Voice to Data‐Centric
1.5 4G: Mobile Internet
1.6 5G: From Human to Machine
1.7 Beyond 5G
1.8 Conclusions
References
2 Pre‐6G Technology and System Evolution
2.1 1G – AMPS
2.2 2G – GSM
2.3 3G – WCDMA
2.4 4G – LTE
2.5 5G – New Radio
2.6 Conclusions
References
3 The Vision of 6G: Drivers, Enablers, Uses, and Roadmap
3.1 Background
3.2 Explosive Mobile Traffic
3.3 Use Cases
3.4 Usage Scenarios
3.5 Performance Requirements
3.6 Research Initiatives and Roadmap
3.7 Key Technologies
3.8 Conclusions
References
Note
Part II: Full‐Spectra Wireless Communications in 6G
4 Enhanced Millimeter‐Wave Wireless Communications in 6G
4.1 Spectrum Shortage
4.2 mmWave Propagation Characteristics
4.3 Millimeter‐Wave Channel Models
4.4 mmWave Transmission Technologies
4.5 Summary
References
5 Terahertz Technologies and Systems for 6G
5.1 Potential of Terahertz Band
5.2 Terahertz Applications
5.3 Challenges of Terahertz Communications
5.4 Array‐of‐Subarrays Beamforming
5.5 Lens Antenna
5.6 Case Study – IEEE 802.15.3d
5.7 Summary
References
6 Optical and Visible Light Wireless Communications in 6G
6.1 The Optical Spectrum
6.2 Advantages and Challenges
6.3 OWC Applications
6.4 Evolution of Optical Wireless Communications
6.5 Optical Transceiver
6.6 Optical Sources and Detectors
6.7 Optical Link Configuration
6.8 Optical MIMO
6.9 Summary
References
Part III: Smart Radio Networks and Air Interface Technologies for 6G
7 Intelligent Reflecting Surface‐Aided Communications for 6G
7.1 Basic Concept
7.2 IRS‐Aided Single‐Antenna Transmission
7.3 IRS‐Aided Multi‐Antenna Transmission
7.4 Dual‐Beam Intelligent Reflecting Surface
7.5 IRS‐Aided Wideband Communications
7.6 Multi‐User IRS Communications
7.7 Channel Aging and Prediction
7.8 Summary
References
8 Multiple Dimensional and Antenna Techniques for 6G
8.1 Spatial Diversity
8.2 Receive Combining
8.3 Space‐Time Coding
8.4 Transmit Antenna Selection
8.5 Beamforming
8.6 Spatial Multiplexing
8.7 Summary
References
9 Cellular and Cell‐Free Massive MIMO Techniques in 6G
9.1 Multi‐User MIMO
9.2 Massive MIMO
9.3 Multi‐Cell Massive MIMO
9.4 Cell‐Free Massive MIMO
9.5 Opportunistic Cell‐Free Communications
9.6 Summary
References
10 Adaptive and Non‐Orthogonal Multiple Access Systems in 6G
10.1 Frequency‐Selective Fading Channel
10.2 Multi‐Carrier Modulation
10.3 Orthogonal Frequency‐Division Multiplexing
10.4 Orthogonal Frequency‐Division Multiple Access
10.5 Cell‐Free Massive MIMO‐OFDMA
10.6 Non‐Orthogonal Multiple Access
10.7 Summary
References
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 First‐generation cellular standards.
Table 1.2 Second‐generation cellular standards.
Table 1.3 Third‐generation cellular standards.
Table 1.4 Comparison of the main system parameters between LTE/LTE‐Advanced ...
Table 1.5 Minimum technical performance requirements for IMT‐2020.
Chapter 2
Table 2.1 The main WCDMA radio parameters, in comparison with GSM and IS‐95....
Table 2.2 Comparison of major technical features in previous generations.
Chapter 3
Table 3.1 Performance requirement of 5th percentile user spectral efficienc...
Table 3.2 Performance requirement of average spectral efficiency.
Table 3.3 The 6G vision of mobile industry.
Table 3.4 European Commission Horizon 2020 5G‐PPP beyond‐5G and 6G research...
Chapter 4
Table 4.1 Comparison of free‐space path loss for various frequencies.
Table 4.2 Reflection coefficients of typical building materials measured at...
Table 4.3 Penetration losses of typical building materials measured at 28 G...
Table 4.4 Exemplary comparison of key characteristics between microwave and...
Table 4.5 Summary of major mmWave measurement campaigns.
Table 4.6 3GPP indoor path loss models.
Table 4.7 The parameters of the 3GPP CDL‐A model.
Table 4.8 The parameters of the 3GPP TDL‐A model.
Table 4.9 The mapping between the cell identity within the group and root s...
Table 4.10 OFDM numerology in NR radio frames and SS block parameters.
Chapter 5
Table 5.1 Operating frequency bands specified by 3GPP for NR in FR2.
Table 5.2 The main features of different frequency bands over the whole ele...
Table 5.3 Available THz communications frequency bands recommended by the IT...
Table 5.4 Unlicensed THz communications spectrum bands in the United States...
Table 5.5 Spectroscopic absorption lines for oxygen attenuation.
Table 5.6 Spectroscopic absorption lines for water‐vapor attenuation.
Table 5.7 The values for two coefficients in the calculation of rain attenua...
Table 5.8 Parameters of LDPC codes in IEEE 802.15.3d.
Chapter 6
Table 6.1 The optical spectrum.
Table 6.2 Laser classification.
Table 6.3 Some typical semiconductor materials and their emission ranges.
Table 6.4 Typical laser‐diode materials and their emission wavelength range...
Table 6.5 A comparison of light‐emitting diodes and laser diodes.
Table 6.6 Typical performance parameters of photodiodes.
Chapter 8
Table 8.1 Approximate symbol and bit error probabilities for coherent modul...
Table 8.2 Precoding codebooks for LTE with two antenna ports.
Table 8.3 Precoding codebooks for LTE with four antenna ports.
Chapter 10
Table 10.1 Transmission bandwidth configuration of 3GPP LTE.
List of Illustrations
Chapter 1
Figure 1.1 IMT‐2000 standards approved by ITU‐R [ITU‐R M.1457, 2000].
Figure 1.2 Releases of 3GPP specifications for WCDMA.
Figure 1.3 The evolution path of CDMA2000.
Figure 1.4 IMT‐Advanced standards approved by ITR‐R.
Figure 1.5 Releases of 3GPP specifications for LTE.
Figure 1.6 Usage scenarios of IMT‐2020 defined in ITU‐R M.2083.
Figure 1.7 Improvement of key performance indicators from IMT‐Advanced to IM...
Figure 1.8 Releases of the 3GPP NR‐5GC specifications.
Figure 1.9 The evolution of cellular systems.
Chapter 2
Figure 2.1 Architecture of a typical AMPS system.
Figure 2.2 Cellular network layout illustrating frequency reuse and cell spl...
Figure 2.3 Architecture of the GSM system, overlapped with a GPRS network.
Figure 2.4 Architecture of the WCDMA system. UTRAN stands for new air interf...
Figure 2.5 Architecture of the LTE system. Source: Secureroot/FreeImages.
Figure 2.6 Architecture of the 5G SA system. 5GC, 5GC network; AF, Applicati...
Chapter 3
Figure 3.1 The trend of global mobile subscriptions and mobile traffic from ...
Figure 3.2 An example of 6G usage scenarios: three new scenarios of uMBB, UL...
Figure 3.3 Beyond 5G vision of Huawei.
Figure 3.4 Improvement of key performance indicators from IMT‐2020 to 6G....
Figure 3.5 Estimation of a roadmap of research, definition, specification, s...
Chapter 4
Figure 4.1 The chart of the U.S. spectrum allocation up to 3 GHz, which acco...
Figure 4.2 Illustration of NLOS radio propagation through reflection, diffra...
Figure 4.3 Atmospheric attenuation due to the absorption of oxygen and water...
Figure 4.4 The angular‐domain representation of multipath propagation.
Figure 4.5 The azimuth (a) and elevation (b) angles of a propagation path.
Figure 4.6 Path losses of 3GPP UMa and UMi scenarios, without shadow fading,...
Figure 4.7 Path losses of 3GPP UMa and UMi scenarios as a function of carrie...
Figure 4.8 Far‐field geometry of the radiation of a plane wave from a unifor...
Figure 4.9 Beamforming over an eight‐element ULA with inter‐antenna spacing ...
Figure 4.10 Block diagram of an analog beamforming transmitter. Going throug...
Figure 4.11 Block diagrams of two typical hybrid beamforming: (a) fully conn...
Figure 4.12 Far‐field geometry of the radiation of a plane wave from a unifo...
Figure 4.13 Illustration of two basic multi‐beam synchronization approaches:...
Figure 4.14 Timing of synchronization and broadcasting signals in the FDD (a...
Figure 4.15 Multiple time‐multiplexed SS blocks within an SS‐burst‐set perio...
Figure 4.16 Random beams over an eight‐element ULA with inter‐antenna spacin...
Figure 4.17 Schematic diagrams of the Alamouti‐enhanced random beamforming (...
Figure 4.18 Complementary random beams over an eight‐element ULA with inter‐...
Chapter 5
Figure 5.1 The electromagnetic spectrum and the positions of the mmWave and ...
Figure 5.2 Illustration of the free‐space radiation of an electromagnetic wa...
Figure 5.3 An example to illustrate the decay rate of the received power as ...
Figure 5.4 Atmospheric attenuation at millimeter‐wave and terahertz frequenc...
Figure 5.5 Rain attenuation measured in dB/km for terrestrial communications...
Figure 5.6 The array‐of‐subarrays structure of hybrid beamforming in a terah...
Figure 5.7 Schematic diagram of a lens antenna consisting of a radiator and ...
Figure 5.8 Schematic diagram of a lens antenna array with an incident signal...
Figure 5.9 Schematic diagram of a MIMO system with lens antenna arrays at bo...
Figure 5.10 Channelization of IEEE 802.15.3d, where a total of 69.12 GHz spe...
Figure 5.11 The structure of IEEE 802.15.3d frame.
Figure 5.12 The construction process of IEEE 802.15.3d frame header.
Chapter 6
Figure 6.1 The optical spectrum consisting of infrared, visible light, and u...
Figure 6.2 Block diagram of an end‐to‐end optical wireless communications sy...
Figure 6.3 Schematic diagram of the linear mapping between output optical po...
Figure 6.4 The principle of spontaneous and stimulated radiation.
Figure 6.5 Schematic diagram of a light‐emitting diode, where a semiconducto...
Figure 6.6 Typical radiation spectra of different LEDs, including blue (470 ...
Figure 6.7 Light radiation of a diode rises sharply above the laser threshol...
Figure 6.8 The structures of an edge‐emitting laser diode (the upper) and a ...
Figure 6.9 The basic construction of a photodiode, and the principle of gene...
Figure 6.10 Classification of wireless optical communications links in terms...
Figure 6.11 Schematic diagram of a non‐imaging optical MIMO system where mul...
Figure 6.12 Schematic diagram of spatial modulation using
and
as an exam...
Chapter 7
Figure 7.1 Some examples of promising IRS applications in wireless networks....
Figure 7.2 Illustration of a discrete‐time baseband equivalent model of IRS‐...
Figure 7.3 Comparison of the product‐distance path loss model in the IRS con...
Figure 7.4 Schematic diagram of an IRS‐aided MIMO system.
Figure 7.5 Block diagrams of two‐branch partially connected hybrid beamformi...
Figure 7.6 Illustration of the dual‐beam IRS using hybrid beamforming.
Figure 7.7 Simulation results of the received SNR versus the horizontal dist...
Figure 7.8 Schematic diagram of an IRS‐aided multi‐user MIMO system, consist...
Figure 7.9 Illustration of a downlink IRS‐aided NOMA system consisting of a ...
Figure 7.10 Auto‐correlation of fading channels in terms of different Dopple...
Figure 7.11 The structure of a typical RNN network.
Figure 7.12 Illustration of a three‐hidden‐layer deep LSTM network.
Chapter 8
Figure 8.1 Schematic diagram of multi‐antenna receive diversity with a linea...
Figure 8.2 Average BER performance of selection combining with QPSK under
i.
...
Figure 8.3 Comparison between single‐antenna transmission and multi‐antenna ...
Figure 8.4 An example of space‐time trellis coding with four states, QPSK co...
Figure 8.5 The Alamouti scheme over two‐branch transmit diversity system wit...
Figure 8.6 Schematic diagram of transmit antenna selection where the best an...
Figure 8.7 Schematic diagram of a transmit beamformer and a receive beamform...
Figure 8.8 Schematic diagram of multiple transmit antennas with precoding.
Figure 8.9 Schematic diagram of a MIMO channel having
transmit antennas an...
Figure 8.10 Converting a MIMO channel into parallel subchannels through the ...
Figure 8.11 Schematic diagram of linear precoding in a single‐user MIMO syst...
Figure 8.12 Original and rotated constellation.
Figure 8.13 Principle of MIMO detection based on a matched filter, where the...
Figure 8.14 Schematic diagram of successive interference cancelation: a bank...
Chapter 9
Figure 9.1 Schematic diagram of the downlink for a multi‐user MIMO system.
Figure 9.2 Capacity region of a two‐user multi‐antenna system.
Figure 9.3 The model of a multi‐cell massive MIMO system, where cell
is ce...
Figure 9.4 Schematic diagram of a cell‐free massive MIMO system where
sing...
Figure 9.5 The layout of a cell‐free massive MIMO system where
access poin...
Figure 9.6 Schematic diagram for time alignment of zero‐forcing precoding in...
Figure 9.7 The CDF comparison under different conditions of user mobility an...
Figure 9.8 Illustration of opportunistic AP selection in a cell‐free massive...
Figure 9.9 CDFs of the achievable spectral efficiency for different schemes ...
Chapter 10
Figure 10.1 Illustration of the filter taps generated from the 3GPP ETU chan...
Figure 10.2 Block diagram of a multi‐carrier modulation system consisting of...
Figure 10.3 Illustration of a group of orthogonal subcarriers [Jiang and Kai...
Figure 10.4 The rectangular prototype filter of the OFDM signal in the time ...
Figure 10.5 The principle of OFDM modulation and demodulation over a set of ...
Figure 10.6 The equivalence between multi‐carrier modulation over a set of o...
Figure 10.7 The cyclic prefix can alleviate the inter‐symbol interference an...
Figure 10.8 Block diagram of an end‐to‐end OFDM transmission system, and its...
Figure 10.9 Illustration of orthogonal frequency‐division multiple access us...
Figure 10.10 Block diagram of single‐carrier frequency‐division multiple acc...
Figure 10.11 Schematic diagram of cyclic delay diversity in an OFDM system, ...
Figure 10.12 The principles of fractional frequency reuse and soft frequency...
Figure 10.13 Schematic diagram of a cell‐free massive MIMO‐OFDM system where...
Figure 10.14 Illustration of user‐specific resource allocation in a cell‐fre...
Figure 10.15 Illustration of downlink NOMA consisting of a base station, a f...
Figure 10.16 Illustration of uplink NOMA consisting of a base station, a far...
Figure 10.17 An example of composite constellations of downlink superpositio...
Figure 10.18 Block diagram of an LDS‐CDMA system, where multiple users simul...
Figure 10.19 An example of the indication matrix and its corresponding facto...
Figure 10.20 Illustration of an SCMA system with six users and four subcarri...
Guide
Cover
Table of Contents
Title Page
Copyright
Preface
List of Abbreviations
Begin Reading
Index
End User License Agreement
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6G Key Technologies
A Comprehensive Guide
Wei Jiang and Fa‐Long Luo
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Preface
Wireless technologies and applications are now being developed in a very rapid speed and massively large scale. In the early 2019, when South Korea's three mobile operators and US Verizon were arguing with each other about who would be the world's first provider of the fifth generation (5G) communication services, we stepped into the era of 5G. In the past three years, the term 5G has been remaining one of the hottest buzzwords in the media, attracting unprecedented attention from the whole society. It even went beyond the sphere of technology and economy, becoming the focal point of geopolitical tension. In addition to further improving network capacities such as the previous generations, 5G expands mobile communication services from human to things and from consumers to vertical industries. The potential scale of mobile subscriptions is substantially enlarged from merely billions of the world's populations to almost countless inter‐connectivity among humans, machines, and things. It enables a wide variety of services from traditional mobile broadband to Industry 4.0, virtual reality, Internet of things, and automatic driving. In 2020, the outbreak of the COVID‐19 pandemic leads to a dramatic loss of human life worldwide and imposes unprecedented challenges on societal and economic activities. However, this public health crisis highlights the unique role of telecommunication networks and digital infrastructure in keeping society running and families connected, especially the values of 5G services and applications, such as remote surgeons, online education, remote working, driver‐less vehicles, unmanned delivery, robots, smart healthcare, and autonomous manufacturing.
As of the writing of this book, the 5G mobile networks are still on its way to being deployed across the world, but it is already time for the academia and industry to shift their attention to beyond 5G or the sixth generation (6G) system to satisfy the future demands for information and communications technology in 2030. Even though discussions are ongoing within the wireless community as to whether there is any need for 6G or whether counting the generations should be stopped at 5, many research groups, standardization and regulatory organizations, and countries across the world have kicked off their initiatives toward 6G. A focus group called Technologies for Network 2030 within the International Telecommunication Union Telecommunication (ITU‐T) standardization sector was established in July 2018. This group intends to study the capabilities of networks for 2030 and beyond, when it is expected to support novel forward‐looking scenarios, such as holographic‐type communications, pervasive intelligence, tactile internet, multi‐sense experience, and digital twin. The European Commission initiated to sponsor beyond 5G research activities, as its recent Horizon 2020 calls – ICT‐20 5G Long Term Evolution and ICT‐52 Smart Connectivity beyond 5G – where a batch of pioneer research projects for key 6G technologies was kicked off at the early beginning of 2020. The European Commission has also announced its strategy to accelerate investments in Europe's “Gigabit Connectivity” including 5G and 6G to shape Europe's digital future. In October 2020, the Next Generation Mobile Networks (NGMN) has launched its new “6G Vision and Drivers” project, intending to provide early and timely direction for global 6G activities. At its meeting in February 2020, the International Telecommunication Union Radiocommunication (ITU‐R) sector decided to start studying future technology trends for the future evolution of International Mobile Telecommunications (IMT‐2030).
Inspired by the tremendous impact of 5G technology, governments and the public further recognized the significance of mobile systems for economic prosperity and national security. In the past two years, many countries have announced ambitious plans on the development of 6G or already launched research initiatives officially. In Finland, the University of Oulu began ground‐breaking 6G research as part of Academy of Finland's flagship program called “6G‐Enabled Wireless Smart Society and Ecosystem (6Genesis)”, which focuses on several challenging research areas including reliable near‐instant unlimited wireless connectivity, distributed computing and intelligence, as well as materials and antennas to be utilized in future for circuits and devices. In March 2019, the Federal Communications Commission (FCC) of the United States announced that it opens experimental license for the use of frequencies between 95 GHz and 3 THz for 6G and beyond, fostering the test of THz communications. In October 2020, the Alliance for Telecommunications Industry Solutions (ATIS) launched Next G Alliance with founding members including AT&T, T‐Mobile, Verizon, Qualcomm, Ericsson, Nokia, Apple, Google, Facebook, Microsoft, etc. It is an industry initiative that intends to advance North American mobile technology leadership in 6G over the next decade through private sector‐led efforts. Another US company, SpaceX, which is famous for its revolutionary innovation of reusable rockets, announced the Starlink project in 2015. Starlink is a very large‐scale LEO communication satellite constellation aiming to offer ubiquitous Internet access services across the whole planet. It is envisioned that such as a space communication infrastructure will reshape the architecture of the next‐generation mobile communications. In November 2019, the Ministry of Science and Technology of China has officially kicked off the 6G technology research and development works coordinated by the ministry, together with five other ministries or national institutions. A promotion working group from the government that is in charge of management and coordination, and an overall expert group that is composed of 37 experts from universities, research institutes, and industry were established at this event. In late 2017, a working group was established by the Japanese Ministry of Internal Affairs and Communications to study next‐generation wireless technologies. South Korea announced a plan to set up the first 6G trial in 2026 and is expected to spend around 169 million US dollars over five years to develop key 6G technologies. Germany has also entered this crowded field. Beginning in August 2021, the German Federal Ministry of Education and Research (BMBF) funded the establishment of four hubs for research into the future technology 6G with up to 250 million euros in the first four year term.
At this historical crossroad, it is strongly believed that a book on 6G will serve as an enlightening guideline to spur interests and further investigations related to 6G communication systems. Such a book will also attract a broad audience in both academia and industry of all related fields. By far, a book to deal in a systematic and unified manner to cover the state‐of‐the‐art vision of 6G and elaborate a complete list of identified key technologies is still lacking but highly desirable. From technology research and development point of views and authored by two experts in the field, this book aims to be the world's first book to provide a comprehensive and highly consistent treatment on the enabling techniques for 6G radio transmission and signal processing by covering New Vision, New Spectrum, New Propagation, as well as New Air Interface and Smart Radio Systems. This book is organized into 10 chapters in three parts.
Part 1: Vision of 6G and Technical Evolution
In terms of the technology development and practice applications, the first part of this book will present the vision of 6G by reviewing the evolution from 1G standards to 5G standards and put the emphasis on the driving factors, requirements, use cases, key performance indicators (KPI), and roadmap toward 6G. Consisting of three chapters, the first part will also drive a detailed list of potential 6G technologies to support the targeted use cases and KPIs.
Chapter 1: Standards History of Cellular Systems Toward 6G
To well understand the complex cellular systems of today, it is vital to have a complete view of how cellular systems have evolved. To this end, the motivation of the first chapter is to provide the readers a brief review of the whole history of mobile cellular systems, from pre‐cellular to 5G. Then, the readers should be able to well prepare for getting insights into the 6G technology.
Chapter 2: Pre‐6G Technology and System Evolution
The second chapter will provide an in‐depth study of the previous generations from the technological perspective. A symbolic standard, which achieved a dominant position commercially in the market worldwide and adopted mainstreaming technologies at that time, is elaborated. In this regard, the readers will understand the overall architecture of the representative cellular system for each generation, including major network elements, functionality split, interconnection, interaction, and operational flows.
Chapter 3: Vision of 6G: Drivers, Enablers, Uses, and Roadmap
It is necessary to clarify the significance and the fundamental motivation of developing 6G and convince the readers that 6G will definitely come like the previous generations of mobile communications before jumping into 6G technical details. This chapter will provide a comprehensive vision concerning the driving forces, use cases, and usage scenarios and demonstrate essential performance requirements and identify key technological enablers.
Part 2: Full‐Spectra Wireless Communications in 6G
Organized into three chapters, the second part of this book focuses on the full‐spectra wireless communications for 6G by including new spectrum opportunities related to millimeter wave, terahertz communications, visible light communications, and optical wireless communications.
Chapter 4: Enhanced Millimeter‐Wave Wireless Communications in 6G
Millimeter‐wave (mmWave) has been adopted in 5G systems, but its utilization is infancy. Hence, enhanced mmWave wireless communications is highly probably a key enabler of 6G. Regardless of the abundant spectral resources and contiguous large‐volume bandwidths, the characteristics of mmWave signal propagation are distinct from that of low‐frequency bands at UHF and microwave bands. This chapter will focus on the characteristics of mmWave signal propagation and key mmWave transmission technologies to unleash the potential of high frequencies.
Chapter 5: Terahertz Technologies and Systems for 6G
To satisfy the demand of extreme transmission rate on the magnitude order of tera‐bits‐per‐second envisioned in the 6G system, wireless communications need to exploit the abundant spectrum in the Terahertz (THz) band. In addition to THz communications, the THz band is also applied for other particular applications, such as imaging, sensing, and positioning, which are expected to achieve synergy with THz communications in 6G. In addition to shed light on its high potential, this chapter will analyze major challenges such as high free‐space path loss, atmospheric absorption, rainfall attenuation, blockage, and high Doppler fluctuation and will introduce enabling THz technologies such as array‐of‐subarrays beamforming in an ultra‐massive MIMO system and lens antenna arrays. Meanwhile, the world's first THz communications standard, i.e. IEEE 802.15.3d, will be presented to give an insight.
Chapter 6: Optical and Visible Light Wireless Communications in 6G
Optical Wireless Communications points to wireless communications that use the optical spectrum, including infrared, visible light, and ultraviolet, as the transmission medium. Optical wireless communications show great advantages in deployment scenarios such as home networking, vehicular communications in intelligent transportation systems, airplane passenger lighting, and electronic medical equipment that is sensitive to RF interference. This chapter will introduce the main technical features, the physical fundamentals of optical devices, and the major challenges in optical communications systems.
Part 3: Smart Radio Networks and Air Interface Technologies for 6G
Moving to radio network and air interface level of 6G, the third part of this book consists of four chapters by mainly addressing the related technologies including intelligent reflecting surface (IRS)‐based systems, multiple dimensional and antenna techniques, cellular and cell‐free massive MIMO, and adaptive and non‐orthogonal multiple access.
Chapter 7: Intelligent Reflecting Surface‐Aided Communications in 6G
Using a large number of small, passive, and low‐cost reflecting elements, IRS can proactively form a smart and programmable wireless environment. Thus, it provides a new degree of freedom to the design of 6G wireless systems, enabling sustainable capacity and performance growth with affordable cost, low complexity, and low energy consumption. This chapter will introduce the system model and the signal transmission of IRS‐aided systems with either single‐antenna or multi‐antenna base stations in both frequency‐flat and frequency‐selective fading channels. It can serve as a tutorial for the readers as a starting point to further carry out research works on this promising topic.
Chapter 8: Multiple Dimensional and Antenna Techniques for 6G
This chapter will explore the fundamentals of multi‐antenna transmission, including spatial diversity, beamforming, and spatial multiplexing. Although some of these multi‐antenna techniques have been adopted in pre‐6G standards, they will also play a critical role in the 6G systems, especially when combining with emerging technologies, such as intelligent reflecting surface, cell‐free structure, non‐orthogonal multiple access and terahertz as well as optical, and visible‐light communications. Therefore, this chapter will provide comprehensive insights into these techniques aiming to unleash their full potentials in 6G.
Chapter 9: Cellular and Cell‐Free Massive MIMO Techniques for 6G
This chapter will first introduce the critical issues of multi‐user MIMO techniques, including the principle of the well‐known dirty‐paper coding. Then, a revolutionary technique called massive MIMO that breaks the scalability barrier by not attempting to achieve the full Shannon limit and paradoxically by increasing the size of the system is shown. This chapter will emphasize a cutting‐edge technology called cell‐free massive MIMO. The cell‐free architecture is particularly attractive for the upcoming 6G deployment scenarios, such as a campus or a private network dedicated to an industrial vertical, and it is envisioned as a key technology enabler of 6G.
Chapter 10: Adaptive and Non‐orthogonal Multiple Access Systems in 6G
A cellular network needs to accommodate a lot of active subscribers simultaneously over a finite amount of time frequency resources. Both orthogonal and non‐orthogonal multiple accesses are envisioned to be evolved further and play a critical role in the upcoming 6G system design. Although OFDM, OFDMA, SC‐FDMA, and NOMA have been adopted in pre‐6G standards, these techniques will play a fundamental role in 6G, in the conventional sub‐6 GHz band and high‐frequency bands. There exists a big room for further exploiting these techniques when combining with intelligent reflecting surface, cell‐free structure, mmWave, terahertz, and optical transmission techniques.
For Whom Is this Book Written?
It is hoped that this book serves not only as a complete and invaluable reference for professional engineers, researchers, manufacturers, network operators, software developers, content providers, service providers, broadcasters, and regulatory bodies aiming at development, standardization, deployment, and applications of 6G system, but also as a textbook for graduate students in circuits, signal processing, wireless communications, artificial intelligence, microwave technology, information theory, antenna and propagation, system‐on‐chip implementation, and computer networks.
Wei Jiang, Ph.DKaiserslautern, GermanyMarch, 2022
Fa‐Long Luo, Ph.DSilicon Valley, California, USAMarch, 2022
List of Abbreviations
0G
Zeroth Generation
1G
First Generation
2G
Second Generation
3G
Third Generation
3GPP
Third Generation Partnership Project
3GPP2
Third Generation Partnership Project 2
4G
Fourth Generation
5G
Fifth Generation
5GC
5G Core network
6G
Sixth Generation
AAS
Active Antenna System
ACI
Adjacent Channel Interference
AF
Application Function
AGV
Automated Guided Vehicle
AI
Artificial Intelligence
AMF
Access and Mobility Management Function
AMPS
Advanced Mobile Phone System
AOA
Angle of Arrival
AOD
Angle of Departure
AP
Access Point
APP
Application
ARIB
Association of Radio Industries and Businesses
AUSF
Authentication Server Function
AWGN
Additive White Gaussian Noise
BBU
Baseband Unit
BCI
Brain–Computer Interface
BD
Block Diagonalization
BER
Bit Error Ratio
BPSK
Binary Phase‐Shift Keying
BPTT
Back‐Propagation Through Time
BS
Base Station
BSC
Base Station Controller
BSS
Base Station Subsystem
BTS
Base Transceiver Station
CAPEX
Capital Expenditure
CDD
Cyclic Delay Diversity
CDF
Cumulative Distribution Function
CDMA
Code‐Division Multiple Access
CDPD
Cellular Digital Packet Data
CEPT
Conference of European Postal and Telecommunications
CFR
Channel Frequency Response
CIR
Channel Impulse Response
CoMP
Coordinated Multi‐Point transmission and reception
CP
Cyclic Prefix
CPRI
Common Public Radio Interface
CPU
Central Processing Unit
CR
Cognitive Radio
C‐RAN
Cloud Radio Access Network
CRC
Cyclic Redundancy Code
CS
Circuit‐Switched
CSI
Channel State Information
CTN
Cellular Telephone Number
CU
Centralized Unit
D2D
Device‐to‐Device
DAC
Digital‐to‐Analog Convertor
D‐AMPS
Digital Advanced Mobile Phone System
DFT
Discrete Fourier Transform
DHCP
Dynamic Host Configuration Protocol
DL
Downlink
DPC
Dirty Paper Coding
DPSK
Differential Phase Shift Keying
DSA
Dynamic Spectrum Allocation
DSL
Digital Subscriber Line
DSP
Digital Signal Processing (DSP)
DSS
Dynamic Spectrum Sharing
DU
Distributed Unit
DVB
Digital Video Broadcasting
E2E
End‐to‐End
EDGE
Enhanced Data Rates for GSM Evolution
eICIC
Enhanced Inter‐Cell Interference Coordination
EIRP
Effective Isotropic Radiated Power
eMBB
Enhanced Mobile Broadband
EPC
Evolved Packet Core
ESN
Electronic Serial Number
ESPRIT
Estimation of Signal Parameters via Rational Invariance Techniques
ETSI
European Telecommunications Standards Institute
ETU
Extended Typical Urban
E‐UTRA
Evolved Universal Terrestrial Radio Access
FBMC
Filter‐Bank Multi‐Carrier
FCC
Federal Communications Commission
FD
Full‐Duplex
FDD
Frequency Division Duplexing
FDMA
Frequency‐Division Multiple Access
FEC
Forward Error Correction
FFR
Fractional Frequency Reuse
FFSK
Fast Frequency‐Shift Keying
FFT
Fast Fourier Transform
FIR
Finite Impulse Response
FM
Frequency Modulation
FOMA
Freedom of Mobile Multimedia Access
FOV
Fields of View
FPGA
Field‐Programmable Gate Array
FSK
Frequency‐Shift Keying
FSO
Free‐Space Optical
FSPL
Free Space Pass Loss
FSTD
Frequency‐Switched Transmit Diversity
FTN
Faster‐Than‐Nyquist
GDPR
General Data Protection Regulation
GERAN
GSM EDGE Radio Access Network
GFDM
Generalized Frequency Division Multiplexing
GGSN
Gateway GPRS Support Node
GMSK
Gaussian Minimum Shift Keying
gNB
Next‐generation Node B
GNSS
Global Navigation Satellite System
GPRS
General Packet Radio Service
GPS
Global Positioning System
GRU
Gated Recurrent Unit
GSM
Global System for Mobile communications
HAP
High Altitude Platform
HARQ
Hybrid Automatic Repeat Request
HDTV
High‐Definition Television
HetNet
Heterogeneous Network
HLR
Home Location Register
HSDPA
High Speed Downlink Packet Access
HSPA
High Speed Packet Access
HSUPA
High Speed Uplink Packet Access
IAB
Integrated Access and Backhaul
ICI
Inter‐Cell Interference
ICIC
Inter‐Cell Interference Coordination
ICNIRP
International Commission on Non‐Ionizing Radiation Protection
ICT
Information and Communications Technology
IFFT
Inverse Fast Fourier Transform
IIoT
Industrial Internet of Things
IMEI
International Mobile Equipment Identity
IMSI
International Mobile Subscriber Identity
IMT
International Mobile Telecommunications
IMTS
Improved Mobile Telephone Service
IoT
Internet of Things
IR
Infra‐Red
IRC
Interference Rejection Combining
IRS
Intelligent Reflecting Surface
ISD
Inter‐Site Distance
ISDN
Integrated Services Digital Network
ISI
Inter‐Symbol Interference
JT
Joint Transmission
KPI
Key Performance Indicator
LAA
License‐Assisted Access
LD
Laser Diode
LDPC
Low Density Parity Check
LED
Light‐Emitting Diode
LEO
Low Earth Orbit
LIDAR
Light Detection and Ranging
Li‐Fi
Light Fidelity
LOS
Line‐Of‐Sight
LPF
Low Pass Filter
LSTM
Long‐Short Term Memory
LTE
Long‐Term Evolution
LTE‐Advanced
Long‐Term Evolution‐Advanced
MAC
Medium Access Control
MAP
Maximum a Posteriori
MC‐CDMA
Multi‐Carrier Code‐Division Multiple Access
MCM
Multi‐Carrier Modulation
MCS
Modulation and Coding Scheme
MEC
Mobile Edge Computing
MF
Matched Filtering
MIB
Master Information Block
MIMO
Multiple Input Multiple Output
ML
Maximum‐Likelihood
MME
Mobility Management Entity
MMS
Multimedia Messaging Service
MMSE
Minimum Mean Square Error
mMTC
Massive Machine‐Type Communications
mmWave
Millimeter Wave
MRC
Maximum‐Ratio Combining
MRT
Maximum‐Ratio Transmission
MSS
Mobile Station Subsystem
MTC
Machine‐Type Communications
MTS
Mobile Telephone Service
MTSO
Mobile Telephone Switching Office
MUD
Multi‐User Detection
MU‐MIMO
Multi‐User Multiple‐Input Multiple‐Output
MUSA
Multi‐User Shared Access
MUSIC
Multiple Signal Classification
MUST
Multi‐User Superposition Transmission
NaaS
Network‐as‐a‐Service
NB‐IoT
Narrow‐Band Internet of Things
NEF
Network Exposure Function
NFV
Network Function Virtualization
NGMA
Next Generation Mobile Networks
NLoS
Non‐Line‐of‐Sight
NOMA
Non‐Orthogonal Multiple Access
NR
New Radio
NRF
NF Repository Function
NSA
Non‐Standalone
NSS
Network and Switching Subsystem
NTIA
National Telecommunications and Information Administration
NTT
Nippon Telegraph and Telephone
NTT
Non‐Terrestrial Networks
OAM
Orbital Angular Momentum
OFDM
Orthogonal Frequency‐Division Multiplexing
OFDMA
Orthogonal Frequency‐Division Multiple Access
OMA
Orthogonal Multiple Access
OOB
Out‐Of‐Band
OOK
On‐Off Keying
OPEX
Operational Expenditure
O‐RAN
Open Radio Access Network
OSS
Operation and Support Subsystem
OTT
Over‐The‐Top
OWC
Optical Wireless Communications
QAM
Quadrature Amplitude Modulation
QoE
Quality of Experience
QoS
Quality of Service
QPSK
Quadrature Phase Shift Keying
P2P
Peer‐to‐Peer
PA
Power Amplifier
PAM
Pulse Amplitude Modulation
PAPR
Peak‐to‐Average‐Power Ratio
PAS
Power Angular Spectrum
PBCH
Physical Broadcast Channel
PCEF
Policy and Charging Enforcement Function
PCF
Policy Control Function
PCM
Pulse Coded Modulation
PCRF
Policy and Charging Rules Function
PD
Photo Diode
PDC
Personal Digital Cellular
PDN
Packet Data Network
PER
Packet Error Rate
P‐GW
Packet Data Network Gateway
PHICH
Physical Hybrid ARQ Indicator Channel
PHY
Physical Layer
PIC
Parallel Interference Cancelation
PMI
Precoding Matrix Indicator
PPN
Polyphase Network
PRACH
Physical Random Access Channel
PS
Packet‐Switched
PSD
Power Spectral Density
PSS
Primary Synchronization Signal
PSTN
Public Switched Telephone Network
RAN
Radio Access Network
RAT
Radio Access Technology
RB
Resource Block
RF
Radio Frequency
RFU
Radio Frequency Unit
RIS
Reconfigurable Intelligent Surface
RMS
Root Mean Square
RNC
Radio Network Controller
RNN
Recurrent Neural Network
RRC
Radio Resource Control
RRH
Remote Radio Head
RRM
Radio Resource Management
RU
Radio Unit
SAR
Synthetic Aperture Radar
SBA
Service‐Based Architecture
SC
Single Carrier
SC‐FDMA
Single Carrier‐Frequency‐Division Multiple Access
SCM
Spatial Channel Model
SCMA
Sparse Code Multiple Access
SDMA
Space‐Division Multiple Access
SDR
Software‐Defined Radio
SDSF
Structured Data Storage network Function
SFBC
Space‐Frequency Block Coding
SFR
Soft Frequency Reuse
SGD
Stochastic Gradient Descent
SGSN
Serving GPRS Support Node
S‐GW
Serving Gateway
SIC
Successive Interference Cancellation
SIM
Subscriber Identity Module
SIMO
Single‐Input Multiple‐Output
SINR
Signal‐to‐Interference‐plus‐Noise Ratio
SISO
Single‐Input Single‐Output
SLA
Service Level Agreement
SLAM
Simultaneous Localization And Mapping
SMF
Session Management Function
SMS
Short Messaging Service
SNR
Signal‐to‐Noise Ratio
SON
Self‐Organizing Network
SSS
Secondary Synchronization Signal
STBC
Space‐Time Block Coding
STTC
Space‐Time Trellis Code
SU‐MIMO
Single‐User Multiple‐Input Multiple‐Output
SVD
Singular Value Decomposition
SWIPT
Simultaneous Wireless Information and Power Transfer
TAS
Transmit Antenna Selection
TDD
Time Division Duplexing
TDMA
Time‐Division Multiple Access
TD‐SCDMA
Time Division‐Synchronous Code Division Multiple Access
THP
Tomlinson–Harashima Precoding
THz
Terahertz
TIA
Telecommunications Industry Association
TRI
Transmit Rank Indicator
TTI
Transmission Time Interval
UAV
Unmanned Aerial Vehicle
UCA
Uniform Circular Array
UDM
Unified Data Management
UDN
Ultra‐Dense Network
UDSF
Unstructured Data Storage network Function
UE
User Equipment
UHF
Ultra High Frequency
UL
Uplink
ULA
Uniform Linear Array
UMTS
Universal Mobile Telecommunications System
UPF
User Plane Function
URLLC
Ultra‐Reliable and Low‐Latency Communications
UTRA
Universal Terrestrial Radio Access
UV
Ultraviolet
V2I
Vehicle‐to‐Infrastructure
V2P
Vehicle‐to‐Pedestrian
V2V
Vehicle‐to‐Vehicle
V‐BLAST
Vertical Bell Laboratories Layered Space‐Time Architecture
VLC
Visible Light Communications
VLR
Visitor Location Register
VR
Virtual Reality
WAP
Wireless Application Protocol
WCDMA
Wideband Code‐Division Multiple Access
Wi‐Fi
Wireless Fidelity
WiMAX
Worldwide Interoperability for Microwave Access
WLAN
Wireless Local Area Network
WRAN
Wireless Regional Area Networks
WRC
World Radiocommunication Conference
ZFP
Zero‐Forcing Precoding
Part IThe Vision of 6G and Technical Evolution
1Standards History of Cellular Systems Toward 6G
In the summer of 1895, a few decades after the invention of the wire telephone, Guglielmo Marconi successfully demonstrated the feasibility of radio transmission. Since then, a wide variety of radio communications and broadcasting services were adopted throughout the world. Around half of a century later, the world‐renowned research institution, Bell Labs, accomplished two historic innovations in the same year of 1947 – the Transistor and the Cellular concept. In the early 1980s, with tens of years' technical development, the first‐generation cellular networks were finally rolled out to offer commercial mobile telephony service to the public. With its ease of deployment, economic efficiency, portability, flexibility, and scalability compared with wire‐line networks, mobile cellular networks experienced explosive growth in the last decades. It became one of the critical infrastructures to empower modern society and drastically reshaped human behaviors in business, education, entertainment, and personal life. Recently, the term 5G has been remained as one of the hottest buzzwords in the media, attracting unprecedented attention from the public. The whole society has got a consensus that the fifth‐generation (5G) cellular system is one of the greatest innovations in the 2020s and will bring tremendous economic and societal benefits. At the moment of starting the writing of this book, more than 400 mobile operators in approximately 130 countries are deploying 5G networks, and the number of 5G subscribers in either the consumer market or vertical industries has already reached an enormous scale in many regions. Now, the attention of academia and industry is increasingly shifting toward the next generation. Since the first experiments with radio communications in the 1890s, it was quite a long journey to reach cutting‐edge mobile communications. To well understand the complex cellular systems of today, it is vital to have a complete view of how cellular systems have evolved. To this end, the motivation of the first chapter in association with the following chapter is to provide the readers a brief review of the whole history of mobile cellular systems, from pre‐cellular to the fifth generation. Then, the readers should be able to well prepared for getting insights into the forthcoming six‐generation (6G) system. This chapter will be organized chronologically in terms of the generations. Each section dedicates to one generation of cellular systems, where the main content generally consists of three main parts:
– The underlying motivation of evolution.
– The milestones of development, standardization, and deployment.
– The review of various competing standards with their major technical features.
1.1 0G: Pre‐Cellular Systems
Wireless communications had been exploited already in early ancient times when people tried to transfer critical messages such as the invasion of enemies by means of smoke, torches, flashing mirrors, signal flares, or semaphore flags. Long‐range transmission was realized through the signal relaying over a network of observation stations built on beacon towers or mountain peaks. These infant communication systems were replaced by the electric telegraph (invented by Samuel Morse in 1837) that transferred text messages over landlines, and later the wire telephone (invented by Alexander Graham Bell in 1876), carrying information‐rich voice signals. In the summer of 1895, a few decades after the invention of the telephone, Guglielmo Marconi successfully carried out the first experiment to illustrate the ability of radio communications. Since then, a wide variety of radio services such as wireless telegraph, mobile telephony, radio broadcasting, television broadcasting, satellite communications, wireless local area networks, and Bluetooth were adopted worldwide and sharply reshaped modern society. As the most successful form of radio technologies, mobile communications have experienced explosive growth in the last decades. Nowadays, cellular networks serve as the critical infrastructure and the basis for the mobile Internet that is an industry worth trillions of dollars per year.
The first cellular system originated in a portable radiophone known as Walkie‐Talkie during World War II, symbolized by SCR‐536 developed by Motorola for the US military. This handheld radio transceiver operated in a push‐to‐talk manner, allowing one radio to transmit while others in its range to listen (i.e. the half‐duplex operation). It was primitive but gained much experience for the later development of pre‐cellular mobile telephone systems. One of the earliest mobile telephone systems was known as Mobile Telephone Service (MTS), which was connected to the public telephone network as an extension of the wire telephone service and operated commercially in the United States in 1946 by Motorola in conjunction with the Bell System. On 17 June 1946, the Bell System demonstrated the world's first mobile call in the City of St. Louis through a car phone weighed around 36 kg. Initially, only 3 channels were available for all the subscribers in the metropolitan area but increased to 32 channels later. Within three years, this service had been expanded to 100 cities across the United States, attracting a total of 5 000 users. In 1964, an enhanced system named Improved Mobile Telephone Service (IMTS) was rolled out to replace the previous MTS system. It achieved two major advances: direct dialing allowing a phone call without manual connection by a human operator, and the full‐duplex transmission, by which two communicating parties can talk simultaneously.
Such pre‐cellular systems were the forerunners of the first generation of cellular networks, sometimes referred to as the zeroth generation (0G). These initial systems utilized a central transmission station to serve an entire metropolitan area. An IMTS base station generally covered a wide area with a diameter of 60–100 kilometers (km) using a transmit power of 100 Watts (100 W), in comparison with less than 1 W on modern base stations. Each voice conversation exclusively occupied a radio channel, but even a large cite was licensed with only a few channels, leading to very limited system capacity. In the 1970s, before the deployment of cellular networks, a customer wishing to subscribe to mobile telephone service had to wait for up to three years until an incumbent subscriber terminated his or her mobile subscription.
Cellular Network
The constraint of network capacity was the main driver for a more elegant network design known as the cellular system.
In 1947, William R. Young, an engineer who worked at AT&T Bell Labs, reported his idea about the hexagonal layout throughout each city so that every mobile telephone can connect to at least one cell. Douglas H. Ring, also at Bell Labs, expanded on Young's concept. He sketched out the basic design for a standard cellular network and published the intellectual groundwork as a technical memorandum entitled Mobile Telephony – Wide Area Coverage on Bell Labs' internal journal on 11 December 1947 [Ring, 1947]. In a cellular network, a wide area can be divided into small geographical areas called cells, each covered by a radio station. It allowed efficient reuse of precious spectral resources at spatially separated sites taking advantage of the fact that the power of a transmitted signal decays dramatically with distance.
Nevertheless, the development process of the cellular system from an initial concept to a practical network was quite a long journey due to technological barriers. AT&T requested a spectrum license for cellular service from the US Federal Communications Commission (FCC) as early as 1947, and the system design had been mostly completed in the 1960s. The first trial network consisting of 10 cells was eventually installed until 1977, when many of the original technologies were outdated [Goldsmith, 2005]. Based on this trial network, Bell Labs worked out the first cellular network standard in the United States called Advanced Mobile Phone System (AMPS) [Young, 1979], which was successfully deployed in many countries and smoothly evolved into a second‐generation cellular standard known as IS‐54 (where IS stands for Interim Standard).
1.2 1G: The Birth of Cellular Network
In December 1979, the Japanese network operator Nippon Telegraph and Telephone (NTT) launched the first commercial cellular system in the world. The initial network comprised 88 cells covering all metropolitan area districts in Tokyo, and inter‐cell handover was supported. It operated in the frequency band around 900 MHz and offered a total of 600 pairs of channels for Frequency‐Division Duplexing (FDD) operation. The voice signal of each mobile user was transmitted over an analog channel with a bandwidth of 25 kHz. Within five years, the network was expanded to cover the entire population of Japan, making it the first country to provide a nationwide cellular communications service.
However, the early mobile stations in the NTT network were still car phones, which had to be fitted into automobiles and were first commercialized in the 1940s. Motorola demonstrated the world's first car call in October 1946, but the phone was too heavy (the original equipment weighs around 36 kg) and consumed too much power. In 1985, NTT released shoulder phones that were still bulky but at least can be carried freely by a human. The gifted engineer Martin Cooper led a Motorola team to develop the first cellphone prototype and demonstrated the first cellphone call at the New York City Hilton in midtown Manhattan on 3 April 1973. Ten years later, Motorola introduced its historic product ‐ DynaTAC 8000X – the first commercial cellphone that was lightweight and small enough to carry. Owning a cellphone at that time was a symbol of affluence and social status since, for example, the Motorola DynaTAC 8000X was priced at in 1984 with, in addition, an expensive subscription cost. Motorola played an exceptionally influential role in the early days of the development of cellphones. Followed its iconic DynaTAC 8000 series, the company released the world's first flip phone Motorola MicroTAC and then the first clamshell phone Motorola StarTAC, which was not only the world's smallest at the time but also most lightweight with an extreme weight of 105 g. These early days also witnessed the rise of Nokia to become the world's second‐largest cellphone maker with the launch of their Cityman series followed by the Nokia 101 candy bar design as opposed to the previous “bricks” [Linge and Sutton, 2014].
While Motorola was developing the cellphone, Bell Labs worked out the AMPS system, which became the first cellular network standard in the United States [Frenkiel and Schwartz, 2010]. In October 1983, the United States eventually had got its first commercial cellular network launched by Ameritech in Chicago. Although it was later than other regions, the cellular service in the United States was offered through cellphones rather than car phones. In Europe, the Scandinavian countries pioneered the development of the first European cellular standard called Nordic Mobile Telephone (NMT). The first NMT network was rolled out in the Nordic countries of Norway and Sweden in 1981, followed by Denmark and Finland in the subsequent year. It was the first mobile network that can support international roaming. In 1985, the number of subscribers had grown to 110 000 in Scandinavia and Finland, made it the world's largest mobile network then. The initial NMT network was operated in 450 MHz (hence also known as NMT‐450) and adopted a channel bandwidth of 25 kHz. Additional frequency bands, i.e. 890–915 MHz for the uplink and 935–960 MHz for the downlink, were allocated in 1986, and the system operating in these bands became known as NMT‐900. As of 2021, according to Wikipedia, a limited NMT‐450 network is still in operation in some remote regions of Russia to offer basic communication services in sparsely populated areas with long distances. In addition to NMT, European countries developed several different cellular standards, including Total Access Communication System (TACS) first implemented by the United Kingdom in 1983, C‐450 in Germany (1985), and Radiocom 2000 in France (1986). However, the first‐generation European standards were incompatible due to the adoption of different frequency bands, air interfaces, and communication protocols, as summarized in Table 1.1.
Among all first‐generation analog standards, NMT and AMPS are regarded as two good representatives that achieved great success at that time, which are briefly introduced as follows:
1.2.1 Nordic Mobile Telephone (NMT)
Nordic Telecommunications Administrations developed the NMT standard to meet the heavy demand of voice service, which cannot be accommodated by the overcrowding mobile telephone networks then: Auto Radio Phone (ARP) in Finland, Mobile Telephony System (MTD) in Sweden and Denmark, and Public Land Mobile Telephony (OLT) Telephony in Norway. The principle technologies were ready by 1973, and the specifications for base stations were completed in 1977. In 1981, the first NMT system was launched in Norway and Sweden, followed by Denmark and Finland in the subsequent year. Using the FDD operation mode, the uplink transmission was assigned to the frequency band of 453–458 MHz while 463–468 MHz for the downlink. In 1986, another pair of frequency bands, i.e. 890–915 MHz and 935–960 MHz for the uplink and downlink, respectively, were allocated. The system employed Frequency‐Division Multiple Access (FDMA) to accommodate a large number of mobile users. As a consequence, the spectrum was subdivided into a magnitude of narrow‐band channels with a bandwidth of 25 kHz. The voice channels were analog, where the speech signals were modulated through Frequency Modulation (FM). Nevertheless, the control signaling between the base station and the mobile station was transmitted digitally, using Fast Frequency‐Shift Keying (FFSK) modulation with a rate of up to 1200 bps. The cell sizes in an NMT network ranged from 2 to 30 km. To serve car phones, the system utilized a transmission power of up to 15 W (NMT‐450) and 6 W (NMT‐900), while the power was lower (up to 1 W) for mobile handsets. NMT was the first cellular system with fully automatic switching (dialing), and supported the handover among cells from the beginning. It was also the first cellular system to realize international roaming. The NMT specifications were free and open, allowing many companies such as Nokia and Ericsson to produce network equipment and pushing the deployment cost down.
Table 1.1 First‐generation cellular standards.
1.2.2 Advanced Mobile Phone System (AMPS)
AMPS was developed in the United States primarily by Bell Labs, inspired by the heavily congested mobile telephone system. Originated in the cellular concept proposed in 1947, it underwent quite a long journey to become a practical network. The system des
