Laying down highways for 5G future cities

SNU Professor Byonghyo Shim, leading the era of 5G technology

The current focus of interest in the IT industry is ‘5G’. Last April, the era of 5G technology was initiated with the commercialization of 5G. Consumers were primarily interested in how faster 5G would be compared to LTE. This was because for mainstream consumers of mobile communications, matters such as ‘how fast can KakaoTalk messages be sent’, and ‘whether youtube videos can be viewed without buffering’ are important. Phrases in the advertisements also emphasized the fast speed.

With the approach of 5G, we are welcoming an era where devices with AI (Artificial Intelligence), including cars, drones, sensors, robots, and machines, act as agents of communication. Accordingly, spotlight has been thrown upon diverse aspects of communication including not only speed but also latency time, energy efficiency, and connectivity. The 5G infrastructure currently in construction is a container for much more diverse values, not only speed enhancement.

For SNU Professor Byonghyo Shim, who has studied mobile and wireless communications for the past two decades, this is a meaningful moment where 5G has become a near reality. This is because the time for the actual commercialization of technologies he has researched such as super speed, super low-latency, and super connectivity has arrived. Professor Shim likened 4G to a city with narrow roads and a lack of parking space. On the other hand, he expressed 5G as a ‘future city with wide roads and efficient road networks and traffic light systems’. He noted, “With a future city with well-established infrastructure, it will be much easier to construct an ecosystem for new businesses and future-oriented industries. If super low-latency is realized, it will be possible to implement services that were previously impossible.”

On May 24th, we met Professor Shim at SNU Institute of New Media and Communications, Gwanak-gu, Seoul, to listen about ‘low-latency communications technology for artificial intelligence of things’.

-What is ‘low-latency communication technology for AIoT’?

“The three technical characteristics that define 5G technology are super-speed transmission at 20 times the speed of 4G LTE, super low-latency that allows both the transmission and reception of information within 0.01 seconds, and super connectivity that ensures the access of hundreds of thousands devices. The low-latency communications technology for AIoT is a 5G technology that focuses on super low-latency and super connectivity.”

-5G is currently the focus of interest in the IT industry. Could you explain the characteristics of 5G?

“As aforementioned, new technologies have been adopted to guarantee the flexibility of the transmission system so that various situations can be simultaneously supported by using an enhanced encoding and decryption scheme and a wider range of high frequency band to ensure super speed, super low-latency, and super connectivity. If 4G can be likened to a city with many traffic lights, narrow roads, and a lack of parking space, 5G can be viewed as a future city with wide roads and an efficient road network and traffic light system. It is evident that in a future city with well-established infrastructure, it will be easy to construct a new business ecosystem with future-oriented industries. With faster transmission speed and lower latency, it will be possible to enable various mobile services previously thought impossible due to issues of transmission speed and latency time.”

-Among super speed, super low-latency, and super connectivity, which does your research focus on?

“The three categories cannot be decisively divided as water is separated with oil. However, my research focuses more on the super low-latency method. To elaborate, I am conducting research on technologies for super low-latency such as methods to lower the latency that occurs when several mobile devices access the network simultaneously and a straightforward transmission and reception method for IoT that transmits simple information such as control commands and instructions.”

-Why are you focusing on low-latency research?

“The bulk of past research in mobile communications was focused on super speed, and 2~3 years ago, super speed was considered the major topic of communications research. However, with the recently emerging 5G and the approaching fourth industrial revolution, now the focus of wireless mobile communications must be shifted from a human-centric to a machine and device-centered perspective. The communication between devices or machines inherently differs from that between humans in both characteristics and patterns. In unmanned autonomous vehicles, for example, the amount of data for control and instruction information is not bountiful, but the time latency becomes a significant issue. For such reasons, I have focused my research on super low-latency for future communications where devices become the subject of communication.”

-Why was low latency communications technology necessary?

“Latency that occurs during information transmission is not significantly important for most human-to-human communications. It is not a serious issue even if my KakaoTalk message is transmitted 0.5 seconds late to the recipient or if it takes one second for me to look up news on Naver. Things become different, however, when it comes to communication between devices. For example, if important information(such as the sudden stop signal of a car in front) is transmitted a few seconds later during unmanned autonomous driving at high speed, accidents can occur. In unmanned smart factories, if the control and instruction signal for welding, cutting, or sewing of clothing is delayed and the robot or machine malfunctions, this could critically affect the quality of the product. As can be seen, in the sense that reliability is important, we call low-latency technology as URLLC (Ultra-Reliable and Low Latency Communications), to be exact.”

-Which technologies allow the implementation of super speed, super low-latency, and super connectivity in 5G?

“5G is made possible with technologies such as the use of a broader frequency spectrum and advanced encoding and decryption schemes, radio resource control methods for super low-latency service, device to device communication, narrow band transmission methods, and new technologies that ensure the flexibility of transmission systems to support such various situations.”

- And yet, there are complaints that it is still difficult to actually notice the difference with 5G. What is the reason?

“Coverage denotes the regions that provide 5G service. Because more base stations and relay stations have to be constructed to increase coverage, a significant amount of time, effort, and expenses are required. This is why base stations are usually equipped starting from major cities such as Seoul or Busan. Therefore, it is difficult for the user to actually experience and notice 5G technology. Besides, because the frequency used for 5G is higher than that used for 4G, the reach of the signal is comparatively short and less diffraction(a phenomenon of wave going around an obstacle) occurs. In other words, if high frequency is used, the reception performance is significantly deteriorated if the distance between the transmitter and receiver is far, when one is in the next room or in the basement, or when there is an obstacle. For such reasons, in terms of wireless mobile communications, high frequency is considered to have limited propagation characteristics. Due to restriction in the frequency range available for 5G, the 3.5GHz band and millimeter wave band of 28GHz are used, which is higher than the LTE frequency (900MHz, 1.8GHz, etc.), which is why the propagation characteristics are somewhat limited. Through various research, technologies are being developed to overcome such limitations, but it will be difficult to perfectly experience 5G for the current moment.”

- What environment has to be created for high performance in 5G?

“First of all, 5G coverage must be expanded to cover the entire nation, and for this, more base stations must be equipped. If you look at the 5G coverage map provided by mobile service companies, base stations are mostly centered in major cities. Second, effort must be put into optimizing the 5G network performance while actually operating the system. For better communications performance, various aspects such as the locations of the base stations, the surrounding environment(obstacles such as buildings), and the population density should be considered when designing a network. As can be seen, a lot of effort, money, and time are required to enhance the performance and coverage of 5G technology.”

Virtual diagram of networks to support ultra-reliable, low latency communications and other various services.

- I heard that 5G is inaccessible within buildings and when underground.

“As frequency becomes higher, the tendency of waves to propagate straightforward is enforced whereas phenomena such as reflection and scattering become weaker. Also, as the loss en route increases, the signal damping amplifies when transmitting to far off distances. To elaborate, if you are using high frequency, if the receiver is in the next room or in the basement, or if there are obstacles, the reception performance deteriorates. Because of the limited range of frequency available for 5G, the 3.5GHz band and 28GHz millimeter wave band are used, which is higher than the LTE frequency (900MHz, 1.8GHz, etc.). This is why the propagation characteristics are rather limited. When it comes to frequency, outdoors is rather favorable. Advanced technologies such as small cell technology or the use of relay bases are required for the signal to get through underground or indoors.”

- It occurred to me that it may be more efficient to use LTE in everyday life surroundings, excluding industrial settings.

“If you only consider the frequency characteristics, the propagation characteristics of millimeter waves of 28GHz are rather limited. However, there is no significant characteristic difference between the 3.5GHz band and the LTE frequency. As the frequency range used for 5G is broader and a wider variety of technologies are applied, it will eventually perform better than LTE technology. However, it will take time.”

- How many years, do you think, will be necessary for 5G technology to be easily accessible?

“Currently, each mobile service company has tens of thousands 5G base stations, and the number will rise. To establish a network that covers all regions of our country, or in other words, a network with a hundred percent coverage, there needs to be hundreds of thousands base stations. I expect that this will happen several years from now.”

- How can 5G transform our lives?

“Online industries surfaced with the advent of 4G LTE. With your mobile phone, you can now do your banking, make reservations for the KTX train, and look up and purchase products such as cosmetics and clothes. With the emergence of 5G, the mobilization and onlinization of all fields surrounding the industry and consumer ecosystem will be accelerated. In the case of shopping, offline stores including traditional markets, major supermarkets, and shopping malls will decline. The growth of online markets such as Coupang will become a trend that cannot be evaded. For now, AI speakers such as Bixby or Google Home remain rudimentary, but in the near future, they will become smarter and be handily used as they will shop for us, search for information, buy airplane tickets, and do the desk work. 5G will act as the platform that facilitates the use of artificial intelligence. Also, through 5G, a variety of objects (machines, robots, automobiles, drones, and sensors) will be connected with a network, and various new services will emerge, including smart cities, smart factories, smart buildings, and smart farms.”

- To which fields can 5G technology be applied?

“First of all, I think it will provide mobile users with faster speed and thus be used to commercialize AR (Augmented Reality) and VR(Virtual Reality), which have been difficult to realize. The transmitted data load for AR and VR is immense, and the real time response time is extremely important for immersion. For such reasons, the super speed transmission of a maximum of 20Gbps and 1msec super low-latency, which can both be attained with 5G, is crucial for the commercialization of AR and VR technology. With higher transmission speed and significantly lower both-way transmission latency time, the user’s sense of realty and immersion is greatly enhanced, which is why I think interactive games, sports broadcasting, 3D broadcasting, and realistic shopping will get a boost. In addition, 5G will expediate the advent of unmanned autonomous vehicles. With a faster 5G network, it will be possible to transmit and receive real time information about surrounding vehicles. Car accidents could be prevented while also reducing traffic congestions and raising the fuel efficiency. Also, it will be applied in various industrial fields such as rescue missions, telemedicine, and unmanned security systems.”

- Where are we in terms of technical development stages?

“In 5G technology’s early standards, a non-standalone (NSA) technical standard is used. To explain NSA, it means using 5G only in wireless networks and using 4G for wire communication infrastructure. The first standard, which is Release 15 is currently commercialized, and the standardization of an advanced standard, Release 16, is under progress.”

- How do you think this will develop as one of the 100 technologies?

“Until now, the main user of communications was humans, but in the future, device-to-device (robots, artificial intelligence, sensors, and cars) communications will also become a main sector. In a variety of perspectives including latency time, energy consumption, the number of accessing devices, and pattern of information transmission and reception, communications between devices has different characteristics from communications between humans. Fundamental research for this is crucial. In the fourth industrial revolution, technologies such as artificial intelligence, bioengineering, big data will be merged, and IoT (Internet of Things) will act as the key infrastructure that makes this possible. The emphasis on communications technology for devices will increase.”

Source: http://ee.snu.ac.kr/community/news?bm=v&bbsidx=48897

Translated by: Jee Hyun Lee, English Editor of Department of Electrical and Computer Engineering, jlee621@snu.ac.kr