Microwave Journal
www.microwavejournal.com/articles/33966-wireless-communication-beyond-5g

Online Spotlight: Wireless Communication Beyond 5G

May 13, 2020

While the world experiences the rise of 5G, researchers are beginning to think about 6G, the sixth wireless communication generation. In this article, developments and trends in wireless communication are discussed, including visions of 6G and the challenges and technologies based on emerging 5G and Industry 4.0.

We live in a world where the creation and transmission of information has value. The development of humankind is inseparable from information exchange, or communication. How to communicate most efficiently, with respect to speed and cost, affects the pace of human evolution. The 5G rollout is promising and exciting, but it is time to start envisioning the future beyond 5G.1-3

The Evolution of Wireless Communication

Michael Faraday proposed the law of Electromagnetic Induction at 1931, the year when James Clerk Maxwell was born, providing the key to unlocking the door to the science of electromagnetics. With this key, Maxwell in 1861 developed a set of equations describing how electric and magnetic fields are generated by charges and currents, and how changing fields propagate. Maxwell's equations describe the unity of electromagnetic interactions and provide the foundation of modern electromagnetism, the theoretical basis of modern radio communication.

Strictly speaking, wireless communication originated with Marconi in 1895, if the ancient beacon-fire is not included. It took nearly 70 years to evolve wireless communication to the first commercial analog wireless cellular standard 1G (see Figure 1). Voice was the main content of 1G, established in the 1970s. In the 1990s, with the development of digital wireless communication technology, 2G was born. It is also worth noting that, 2G is naturally linked to the infant internet. CDMA ushered in the 3G era, and the 4G era is where the mobile internet is now flourishing and developing. Mobile payment is also booming in 4G; worldwide annual mobile transactions topped 20 trillion dollars in 2018, more than the USA's GDP.

The 5G concept and Industry 4.0 were both proposed around 2014 at almost the same time, making them interconnected and somewhat parallel to each other in development. Industry 4.0 ushered in the age of intelligent manufacturing.4 Everything connected as the core of the fourth industry revolution is dependent on 5G and beyond. 5G, with massive MIMO, mmWave and the IoT, makes it possible to realize the internet of everything.3 The six-level Matryoshka doll in Figure 1 illustrates the evolution of wireless communication from Marconi’s shortwave to 5G in one picture.

Figure 1

Figure 1 The evolution of wireless communication systems from shortwave to 5G.

THE PROMISE OF 6G

In a 1926 Colliers interview with Nikola Tesla, he stated that “When wireless is perfectly applied, the whole earth will be converted into a huge brain…When the wireless transmission of power is made commercial, transport and transmission will be revolutionized…” He accurately predicted the development of wireless communication a century later! It is time now to begin moving beyond 5G with new architectures incorporating new services and technologies to realize this vision.

The promise of 6G is that it will make our planet an intelligent “giant.” With the support of massively integrated electronics and mechanical devices, the “body” of the giant will be built, artificial intelligence (AI) technologies will provide the body with a “brain” and 6G networks will connect the entire body to the brain by operating as “neural networks.” Distributed AI-defined wireless “blockchains” will be capable of providing conditioned reflexes to external stimuli. The giant will be ruled by relevant new scientific ethics.

The world is becoming more interconnected with multiple fields and levels of integration. It is anticipated that 6G networks will provide specific services for different applications. The integrated 6G vision is illustrated in Figure 2. It includes, for example, ultra-high density (hundreds devices/m2) in vertical factories, extreme reliability and latency for remote precision operation like remote surgery, high security for businesses and information transactions, high data transmission speed for high-speed applications like real-time online virtual reality, simultaneous wireless communication and wireless power transfer (WPT) for battery-less wireless electronic devices.

Figure 2

Figure 2 Vision of an all wireless connected intelligent planet.

Potential Technologies and Related Issues

To support the vision, 6G will require a fusion of technologies across several fields, including RF communications, WPT, electromagnetic radiation effects, computer science and engineering, AI, cloud and fog computing, wireless block chain, materials, electronics and physical science.

RF Technologies

The RF spectrum is a non-renewable resource. Although, in theory, it has no upper limit, due to the state of current technologies the range of available spectrum is limited and cost increases exponentially with frequency. Since all wireless services need to occupy a portion of the spectrum, this resource is becoming more and more scarce.

From 1G, 2G, 3G, 4G and now again to 5G, the wireless communications spectrum has been expanding to higher frequency bands; 5G is growing from sub-6 GHz to mmWave, while the next evolution may enter the terahertz regime. Simply raising the upper frequency limit is not necessarily the best solution; instead, maximizing value with limited spectral resources has become the preferred approach.

Software-defined radio technology can automatically detect available wireless channels, then program and configure its transmission or reception parameters, dynamically, to enable more concurrent wireless communications. Thanks to massive MIMO, which largely reduces transmitter power level in the RF chain from the order of 10 W to 1 mW, and new semiconductor technologies, it is possible to realize an all-digital transmitter; the rapidly evolving capabilities of high-frequency digital electronics render practical many processes which were once only theoretically possible. Picocells and femtocells at higher frequencies offer solutions for large density and high-speed applications at smaller ranges, mitigating the limitations of path loss, diffraction and penetration at mmWave frequencies. To meet future requirements, more radical RF technologies like orbital angular momentum communication, quantum communication and visible light communication are being considered.

WPT Technologies

Wireless communication between electronic devices is no longer dependent on intricate cables or fibers, while WPT offers the possibility to cut the shackle to the power supply. At a time when battery technologies, including capacity, life and size are struggling to meet the needs of mobile electronic devices, a broadcast system for simultaneous wireless communication and power transmission is an enabling technology for 6G. This eliminates battery cost as well as space for the battery and related electronics. Moreover, charging or changing of the battery will no longer be required.

This is not an entirely new concept. As early as the beginning of 20th century, Nikola Tesla put forward the idea of wireless energy transmission; he stated: “When the wireless transmission of power is made commercial, transport and transmission will be revolutionized…” Now, after nearly 100 years of development, there are already many wireless transmission technologies, roughly divided into two categories: resonate coupling and electromagnetic (EM) radiation.

EM radiation which supports simultaneous wireless communication and wireless power has the greater potential.5 Near field communication technologies (commonly within 10 cm) were the first to provide solutions for short-range simultaneous wireless communication and power transfer at 6.78 and 13.56 MHz. For long-range applications, the use of mmWave signals is attracting increased interest. Massive MIMO and beamforming technologies make it possible to realize simultaneous wireless communication and power transfer in picocells and femtocells. For long-range, high power transfer, e.g. to power drones or satellites, light wave or laser may be a better choice.

Electromagnetic Radiation Pollution

High intensity electromagnetic waves not only affect the operation of some high precision electronic devices, but may also have an impact on humans, animals, plants and the natural environment. Electromagnetic radiation in nature is distributed in the form of white noise; however, the massive application of electromagnetic technologies has changed the distribution of the noise spectrum.

Studies of electromagnetic radiation risks may be found in the literature.6 For human beings, the first is the thermal effect. More than 70 percent of the human body is water. When electromagnetic energy is absorbed by the body, water molecules collide, and electromagnetic energy is converted into heat energy. Excessive electromagnetic radiation affects tissue development, bone development and vision. The other effect is genetic; microwave energy can damage chromosomes. Animal testing has found a large dose of electromagnetic radiation will accelerate chromosomal variation.

Computer Science and Engineering
AI is considered the most promising enabling 6G technology.1, 7 It has been applied in robotics, economics and political decision-making, control and simulation systems. We are already surrounded by AI such as intelligent search engines and smooth-talking AI assistants. Since Garry Kasparov, the former world chess champion was defeated by ‘Deep Blue’ in 1997, AI has been overtaking humans in field after field. Twenty years later, AlphaGo defeated the best Go player Ke Jie in 2017; Go is considered the most complex board game in the world with even more variables than the stars in the universe.



In practice, numerous AI technologies have been applied to wireless communication, from electronic engineering, such as IC design, electromagnetic simulation and computer-assisted optimization, to resource management such as the dynamic management of base stations and the management of spectral and storage resources, and to information processing such as security and authentication, detection and prediction. In some ways, AI has become an integral part of wireless communication and will be even more important for 6G. The final form of AI-defined wireless communication will make the earth an intelligent planet. It relies on realizing an integrated AI system from the device to the entire network.

Supplements to AI
Edge computing is a distributed computing solution. Researchers believe the data transmission resources required and latencies introduced by the data transmission between terminals and the central servers will be unacceptable. In the following decades, Industry 4.0 is expected to evolve toward a massively distributed production organization, with connected products (i.e., with communication ability), collaborative AI robots, integrated manufacturing and logistics management.7 By distributing data producing devices between the cloud and the edges of the networks, edge computing enables distributed cloud applications while providing higher speed and reducing latencies. It could support more personalization and the management of personal data as well.

6G must be intelligent and world-connected, including one or several cores and countless distributed edge devices. Utilizing big data, deep neural networks and edge computing in conjunction with game theory and self-evolution will provide the “brain,” which along with the 6G wireless communication network will ensure the internet of everything, anywhere and anytime.

“Cloudified” and “Foggified” New World

Cloud computing refers to the wide area network or local area network including hardware, software, network and other unified resources to achieve data computing, storage, processing and sharing of a managed technology.

The concept of fog computing was proposed in 2011. It is a combination of weak and more decentralized computers, which infiltrate all smart devices, including mobile devices, personal computers, smart cars, and various intelligent objects in people's lives. No matter how weak the capacity of a single node, it plays a role in the entire network. Fog computing is an emergent architecture for computing, storage, control and networking that distributes these services closer to end users along the cloud-to-things continuum.

Compared with cloud computing, the architecture of fog computing is more distributed and closer to the edge of the network. Fog computing decentralizes data, data processing and applications on devices to the edge of the network, rather than storing them entirely in the cloud. Data storage and processing rely more on local devices than servers. Combining cloud and fog computing will create a new generation in line with the "decentralized" goals of 6G.

AI-Defined Wireless “Blockchain” Networks

Distributing data producing devices between the cloud and network edges provides higher speeds and reduced latencies, while Blockchain, a decentralized distributed database, allows non-trusting members to have distributed peer-to-peer connections verifiably without a trusted intermediary.

For wireless communication, an AI-defined wireless “blockchain” network an alternative dynamic sharing technology with reduced cost and without the need for a centralized database to support access and sharing. It enables the nearby wireless devices to build a quick-connect dynamic temporary network, to achieve data sharing, computing power sharing, network enhancements, sensors or other device sharing.

Materials, Electronics and Physical Science

Novel material technologies such as graphene open the door to breakthroughs in room-temperature superconductors and battery technology. Heterogeneous integration makes it possible to fabricate microwave analog and digital circuits on one chip. New material science is the key; it provides the possibility to realize technologies that were once only theoretically possible.

Moore’s law states the number of transistors in a densely integrated IC doubles about every 18 months. Moore's prediction proved accurate for several decades and has been used in the semiconductor industry to guide long-term planning and to set targets for research and development. However, IC processing is predicted to reach a limit of 3-5 nanometer (nm) by 2025, after which Moore's law may be no longer hold. It is generally believed that when the device size is close to 5 nm, charge carriers are subject to quantum mechanical effects, and current classical theories break down.

6G coverage will not be limited to the earth’s surface, but will extend into deep water, deep underground, near-earth space, beyond our solar system and into deep space. Quantum information science is the most promising way to realize space level real-time communication. Quantum science is also the key to extending the life of Moore’s law.

Ethics

When developing science and technology, it is important to consider philosophies and ethics as early as possible. These are just a few examples:

The Trolley Problem

Philippa Foot proposed a famous moral psychology dilemma. He described a spectacle of an uncontrolled trolley in which the driver must choose whether to hit one person on the rail or five innocent bystanders. It is simple if the decision is made by an individual; no matter what the choice, it can be explained by a choice made in the heat of the moment. However, when it comes to AI, it becomes complicated since the code is previously programmed. That means the AI's behavior is completely predictable, and therefore the risks must be evaluated.

Gambling and Free Self-Evolution

Game theory and free self-evolution of AI leaves open the possibility for unpredictable behavior. Self-evolution of AI is considered both promising and dangerous. All intelligent things are ultimately realized through computing, and the fundamental theoretical model of the computer is a Turing machine. The "gene" of the Turing machine, and hence AI, is Turing code. Since Turing code is the "gene" of AI, it is the key to realizing AI self-evolution. When AI evolves enough to alter Turing codes and even create new algorithms, it might evolve in its own way, with the possibility of growing out of control in its self-evolution “game.”

Data Discrimination

With strong AI and big data analysis, people live in a panoramic prison under 24 hour monitoring. AI and big data, including age, income, location, marital status, employment, consumption habits and hobbies of each individual; as well as information disclosed in histories of purchases and browsing, security personal information collected from email, phone calls and social media provide differentiated individual information. Sometimes, products or services pushed by advertisers based on big data mining and AI are so suitable as to stimulate the desire to buy. So, to a certain extent, AI and big data know you better than you know yourself. The problem is that while AI and big data know you, they don't necessarily love you. Instead, they use what they know about you to achieve their own purposes, for example, by increasing an airplane ticket price based on travel habits.

Replacement Crisis

Beyond the replacement of handicraft by the machinery manufacturing industry, AI and its derivative technologies have the potential to make people in all fields unemployable, including manual workers, mental workers and even politicians. It is important to make use of AI to enhance the abilities of human beings, rather than the simply replacing their livelihoods.
There must be strong regulations established with sound ethical considerations before new technology is introduced and begins to spiral out of control. Science and technology themselves are lifeless, but their roles and impacts depend on the people and institutions that control them.

CONCLUSION

Potential 6G technologies and challenges are summarized in Figure 3. Whatever 5G brings, it is time for scholars to take it a step further. This article attempts to glimpse beyond 5G, at AI-defined wireless communication systems.

f3.jpg

Figure 3 Potential 6G technologies and challenges.

References

  1. K. David and H. Berndt, "6G Vision and Requirements: Is There Any Need for Beyond 5G?" IEEE Vehicular Technology Magazine, Vol. 13, No. 3, September 2018, pp. 72-80.
  2. M. Katz, M. Matinmikko-Blue and M. Latva-Aho, "6Genesis Flagship Program: Building the Bridges Towards 6G-Enabled Wireless Smart Society and Ecosystem," IEEE 10th Latin-American Conference on Communications, November 2018.
  3. F. Boccardi, R. W. Heath, A. Lozano and T. L. Marzetta "Five Disruptive Technology Directions for 5G," IEEE Communications Magazine, Vol. 52, No. 2, February 2014, pp. 74-80.
  4. Plattform Industrie 4.0. (2016), Aspects of the Research Roadmap in Application Scenarios, Federal Ministry for Economic Affairs and Energy. Berlin, Germany. Web. https://www.plattform-i40.de/I40/Redaktion/EN/Downloads/Publikation/aspects-of-the-research-roadmap.pdf%3F__blob%3DpublicationFile%26v%3D10
  5. R. Zhang and C. K. Ho, "MIMO Broadcasting for Simultaneous Wireless Information and Power Transfer," IEEE Transactions on Wireless Communications, Vol. 12, No. 5, May 2013, pp. 1989-2001.
  6. O. P. Gandhi, G. Lazzi and C. M. Furse, "Electromagnetic Absorption in the Human Head and Neck for Mobile Telephones at 835 and 1900 MHz," IEEE Transactions on Microwave Theory and Techniques, Vol. 44, No. 10, October 1996, pp. 1884-1897.
  7. M. Yao, M. Sohul, V. Marojevic and J. H. Reed, "Artificial Intelligence Defined 5G Radio Access Networks," IEEE Communications Magazine, Vol. 57, No. 3, March 2019, pp. 14-20.