| Notes |
© 2020 NTT DOCOMO, INC. All Rights Reserved.
White Paper
5G Evolution and 6G
NTT DOCOMO, INC.
January 2020
2
Table of Contents
1. Introduction................................................................................................................ 2
2. Direction of Evolution “5G Evolution and 6G”...................................................... 3
2.1. Considerations for 5G evolution ...................................................................... 3
2.2. Considerations for 6G........................................................................................ 5
3. Requirements and Use Cases ............................................................................... 7
3.1. Extreme-high-speed and high-capacity communications ............................ 7
3.2. Extreme coverage extension............................................................................ 8
3.3. Extreme-low power consumption and cost reduction................................... 8
3.4. Extreme-low latency........................................................................................... 9
3.5. Extreme-reliable communication ..................................................................... 9
3.6. Extreme-massive connectivity & sensing..................................................... 10
4. Technological Study Areas................................................................................... 10
4.1. New network topology ..................................................................................... 11
4.2. Coverage extension including non-terrestrial network ............................... 12
4.3. Frequency extension and improved spectrum utilization........................... 13
4.4. Further advancement of wireless transmission technologies ................... 13
4.5. Enhancement for URLLC and industrial IoT networks............................... 14
4.6. Expanded integration of variable wireless technologies............................ 15
4.7. Multi-functionalization and AI for everywhere in mobile network.............. 15
5. Conclusion............................................................................................................... 16
References ...................................................................................................................... 16
1. Introduction
Since the Nippon Telegraph and Telephone Public Corporation (NTT) initiated the world’s first
cellular mobile communication service in December 1979, the technology of mobile
communications has continued to develop every decade, evolving to new generation systems.
With the progress of technology, services have continued to evolve. From the first generation (1G)
to the second generation (2G), voice calls were the main means of communication, and simple
e-mail was possible. However, from the third generation (3G), data communications such as
“i-mode” and multimedia information such as photos, music, and video could be communicated
using mobile devices. From the fourth generation (4G), smartphones have been explosively
popularized by high-speed communication technology exceeding 100 Mbps using the Long Term
Evolution (LTE), and a wide variety of multimedia communication services have appeared. 4G
technology continues to evolve in the form of LTE-Advanced, and has now reached a maximum
communication speed close to 1 Gbps. NTT DOCOMO plans to initiate services based on the fifth
generation (5G) mobile communication system [1-1], which is a more technologically advanced
system, in the spring of 2020.
5G is expected to provide new value as a basic technology supporting future industry and
society, along with artificial intelligence (AI) and the Internet of Things (IoT), as well as further
upgrading of the multimedia communication services with its technical features such as high
speed, high capacity, low latency, and massive connectivity. As shown in Fig. 1-1, the mobile
communication system has been evolving technically every decade, while the services of mobile
communications have changed greatly in cycles of approximately 20 years. Therefore, the “Third
Wave” initiated by 5G is expected to become a larger wave through 5G evolution and the sixth
generation (6G) technology, and will support industry and society in the 2030s.
This white paper describes NTT DOCOMO’s current technical prospects for 5G evolution and
6G. Chapter 2 discusses the direction of future technological evolution from the viewpoints of 5G
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evolution and 6G. Chapter 3 describes the requirements and use cases, and Chapter 4 describes
the prospects of technical research areas. This white paper describes the current thinking (as of
January 2020). Based on this content, we will promote discussions in various industries in a joint
industry-academia-government approach, and update the content.
2G 3G 4G
1980 1985 1990 2000 2010
1G
The First Wave
Dissemination of Mobile Phones
5G
2020
The Third Wave
New Business Value
The Second Wave
Mobile Multimedia
Creating new value for markets (every 20 years)
Technology evolution (every 10 years)
2030
6G
Car phone Shoulder phone MOVA i-mode Smartphone Resolution of
social issues
Human-centered
value creation
Portable
telephone
Handy
telephone
Mobile
phone for
everyone
Information
in hand
A variety of
apps/videos
Figure 1-1. Evolution of technologies and services in mobile communications
2. Direction of Evolution “5G Evolution and 6G”
2.1. Considerations for 5G evolution
The commercial introduction of 5G has already begun worldwide. NTT DOCOMO started 5G
pre-service in September 2019 and is scheduled to start 5G commercial service in the spring of
2020. However, some technical issues and further expectations that need to be actualized in 5G
have already been found, and further technological enhancements in the form of 5G evolution are
necessary as we head into the 2020s.
Figure 2-1 shows the current technical challenges facing 5G. 5G is the first generation mobile
communication system that supports high frequency bands such as the millimeter wave band that
exceeds 10 GHz, and it is a technology that actualizes ultra-high speed wireless data
communications of several gigabits per second using a frequency bandwidth of several-hundred
megahertz, which is remarkably wider than that achieved previously. However, there is much
room for future enhancement in millimeter wave technology in mobile communications. In
particular, improving the coverage and uplink performance in non-line-of-sight (NLOS)
environments are issues that can be discerned from 5G-related trials.
5G has attracted much attention as a technology that supports future industry and society, and
special requirements and high performance in particular are often required in industrial use cases.
In Japan, the discussion of “Local 5G,” which specializes in industry use cases, is on-going and it
is a topic of interest in industry [2-1]. In the future, further enhancement of 5G technology will be
necessary to correspond flexibly to such wide requirements in industrial use cases.
In the initial 5G, i.e., NR Release 15, 3GPP standardized radio technologies focused on
enhanced mobile broadband (eMBB) and a part of ultra-reliable and low latency communications
(URLLC). As with LTE, best-effort services focusing on downlink data rates were mainly actualized.
In the case of 5G evolution, as shown in Fig. 2-2, a direction to promote a highly reliable radio
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technology for industrial applications is considered while improving the uplink performance. In
particular, there are some industry cases in which the uploading of a large amount of image data is
assumed and a guaranteed data rate is required in a service, and the uplink enhancements and
technology to guarantee performance are more important than the communication service for
general users.
High interests from industries
UHF bands
Ex. 800MHz, 2GHz
Frequency
Low SHF bands
3-6GHz
High SHF bands
6-30GHz
EHF bands
> 30GHz
Existing bands Exploitation of higher frequency bands
1G, 2G, 3G
4G
5G
Very high
performances
Key technical issues
Not optimum
yet
mmW
coverage/mobility
improvement
Uplink
performance
enhancement
High requirements
for industry use cases
First generation using mmW
Figure 2-1. Technical challenges on 5G real issues
Best effort Guaranteed
Uplink
Downlink
Initial
5G
5G evolution
Figure 2-2. Direction of performance improvement to 5G evolution
At present, with the popularization of big data and AI, the interest in cyber-physical fusion has
become heightened [2-2]. As shown in Fig. 2-3, AI reproduces the real world in cyberspace and
emulates it beyond the constraints of the real world, so that “future prediction” and “new
knowledge” can be discovered. Various values and solutions such as the solution to social
problems can be offered by utilizing this in services in the real world. The role of wireless
communications in this cyber-physical fusion is assumed to include high capacity and low latency
transmission of real world images and sensing information, and feedback to the real world through
high reliability and low latency control signaling. When considering a human analogy, radio
communications in the cyber-physical fusion corresponds to the role of the nervous system that
transmits information between the brain, i.e., AI, and each organ, i.e., device, such as the eyes
and limbs. Thus, it is easy to imagine that the quantity of information entering the brain, which
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corresponds to the uplink, overwhelmingly increases. Therefore, the direction of performance
improvement shown in Fig. 2-2 is considered to be applicable to this case.
Cyber-space
Physical-space
Cyber Physical Fusion
1. Turn humans, things and
events into information
（large quantity/various types/realtime)
4. Actuate
（Feedback of value to the physical world)
2. Acquire/Accumulate data
(Replication of the physical space/digital twin)
3. Forecast the future /
Discover knowledge
（Data analysis to turn data into value)
Device to AI
High capacity
Low latency
etc.
AI to Device
High reliability
Low latency
etc.
Figure 2-3. Cyber-physical fusion and wireless communications
2.2. Considerations for 6G
In order to examine requirements, we must investigate 6G use cases, technological evolution,
society, and the worldview in the 2030s when 6G will be introduced. The use cases and problem
solutions expected in 5G will mostly be actualized in the 2020s and expand from there. It is
considered that wider and deeper diffusion will be required as a type of further development in the
2030s. In addition, there will be the need for more advanced services, integration of multiple use
cases, and new use cases along with the acceleration of signal processing and the evolution of
various devices. Below are some specific views of the world.
Figure 2-4. Image of the worldview in 6G era
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Solving social problems
Many social issues and needs expected in 5G will be resolved in the 2020s. It is expected that
various solutions such as telework, remote control, telemedicine, distance education, and
autonomous operation of various equipment including cars will be provided by high-speed and
low-latency communication networks for social problems such as regional creation, low birth rate,
aging, and labor shortage in the 2020s. Further popularization of solutions and more advanced
correspondence in the 2030s will require complete problem solving and development. The world is
expected to become a place in which all people, information, and goods can be accessed
anywhere in an ultra-real experience, and the constraints of working place and time are completely
eliminated. This will dramatically eliminate social and cultural disparities between rural and urban
areas, avoid urban concentration of people, and promote local development. It can also make
people's lives more stress-free.
Communication between humans and things
Advanced functions of wearable devices including XR (VR, AR, MR) devices, high definition
images and holograms exceeding 8K, and new five sense communications including tactile sense
will proliferate, and communications between humans and between humans and things will
become ultra-real and rich. As a result, innovative entertainment services and enterprise services
for games, watching sports, etc. will be provided without time and place restrictions.
Through rapid popularization and development of IoT services, the demand for the
communications of things will become very large. High speed and low latency performance that far
exceed the human ability will be required for communications because large data processing
including high-definition images and control of equipment with ultra-low latency will be carried out
by machines.
Expansion of communication environment
Communications are now as ubiquitous as the air around us and as vital as electricity and water.
Therefore, users do not need to be aware of communication settings and the communication
service area. A communication environment will be required in all places with the expansion of the
activity area of people and things. High-rise buildings, drones, flying cars, airplanes, and even
space will be natural activity areas, and not only the ground but also the sky and space will be
indispensable communication areas. The need is increasing for communication areas at sea and
under the sea. Due to the needs of various sensor networks, unmanned factories, and unmanned
construction sites, it is also necessary to construct a communication area in an environment
without human beings. As a result, every place on the ground, sky, and sea will become a
communication area.
Sophistication of cyber-physical fusion
Many services utilizing cyber-physical fusion will be created in the 2020s and will be used
practically in all environments, but more advanced cyber-physical fusion will be required in the
2030s. By transmitting and processing a large amount of information between cyberspace and
physical space without delay, tighter cooperation between both spaces will be achieved, and
ultimately, fusion without a gap between the spaces will be actualized. For humans, it will become
possible for cyberspace to support human thought and action in real time through wearable
devices and micro- devices mounted on the human body. All kinds of things such as transportation
equipment including cars, construction machinery, machine tools, monitoring cameras, and
various sensors will be linked in cyberspace. They will support safety and security, solutions to
social problems, and a rich life for people.
Figure 2-5 shows an image of the technological development toward 6G to actualize the above
concept. In the future, there will be use cases that require extreme performance that even 5G
cannot achieve, as well as new combinations of requirements that do not fall into the three
categories of 5G: eMBB, URLLC, and massive machine type communication (mMTC).
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eMBB
mMTC URLLC
eMBB
mMTC URLLC
New combinations of
requirements for new
use cases
Extreme requirement
for specific use cases
5G 6G
Figure 2-5. Image of technological development toward 6G
3. Requirements and Use Cases
Figure 3-1 shows the requirements for wireless technology to be actualized by 6G through 5G
evolution [3-1]. In addition to the higher requirements of 5G, new requirements that were not
considered in 5G have been added, and they have been expanded more widely. Moreover, as
with 5G, not all requirements need to be met at the same time, but new combinations of
requirements will be required for the future new use cases. The requirements are outlined below
with use cases.
6G
5G
New combinations
of requirements
for new use cases
Extreme high
data rate/capacity
Extreme low
latency
Extreme coverage
Extreme high
reliability
Extreme massive
connectivity
Extreme low
energy & cost
• Peak data rate >100Gbps
exploiting new spectrum bands
• >100x capacity for next decade
• Gbps coverage everywhere
• New coverage areas, e.g.,
sky (10000m), sea (200NM), space, etc.
• Affordable mmW/THz NW & devices
• Devices free from battery charging
• Massive connected devices (10M/km2
)
• Sensing capabilities &
high-precision positioning (cm-order)
• E2E very low latency <1ms
• Always low latency
• Guaranteed QoS for wide range
of use cases (upto 99.99999% reliability)
• Secure, private, safe, resilient, …
eMBB URLLC
mMTC
Figure 3-1. Requirements for 6G wireless technology
3.1. Extreme-high-speed and high-capacity communications
Through further improvements in communication speed, for example, by wireless technology
with extremely high speeds exceeding 100 Gbps, it is considered that new sensory services equal
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to or exceeding actual sensory quality can be actualized. It is anticipated that the user interface
that actualizes such a service will evolve as a wearable device through the evolution of
glasses-type terminals. Such new experience services will be shared among multiple users in real
time, and new synchronized applications such as virtual experience and virtual collaboration in
cyberspace can be expected. In addition, considering trends such as use cases for industry and
cyber-physical fusion, various types of real-time information will be required to be transmitted to
the cloud and AI, which are “brains,” so improvement in the uplink performance becomes more
important.
Figure 3-2. Extreme-high-speed and high-capacity communications
3.2. Extreme coverage extension
In the future, we will aim to develop “extreme coverage extension” that can be used in all kinds
of places, including the sky, sea, and space, which are not covered by current mobile
communication systems. Through this, further expansion of activity environments for humans and
machines and the creation of new industries are expected. This expansion is also expected to be
applied to future use cases such as flying cars and space travel.
Figure 3-3. Extreme coverage extension
3.3. Extreme-low power consumption and cost reduction
As with 5G, low power consumption and cost reduction for network and terminal devices will be
important requirements in 6G from both business and environmental viewpoints. In the future
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including 6G, a world in which devices do not need to be charged by, for example, the
development of power supply technology using radio signals is also expected.
Figure 3-4. Extreme-low power consumption and cost reduction
3.4. Extreme-low latency
In cyber-physical fusion, wireless communications that connect AI and devices is analogous to
the human nervous system which transmits information. In order to actualize services in real-time
and be highly interactive, an always stable end-to-end (E2E) low latency seems to be a basic
requirement. For 6G, concretely, an approximately 1 ms or less E2E latency is considered as the
target value. With this, for example, in a shop automated by robotics, interactive services that
respond attentively similar to a human by watching the facial expression of a customer may be
actualized.
Figure 3-5. Extreme-low latency
3.5. Extreme-reliable communication
As described in the previous chapter, 5G evolution and 6G are expected to trend toward
requiring not only best-effort communication but also quality assurance communication. Wirelessly
communicating highly reliable control information is an important requirement for many industrial
use cases such as remote control and factory automation, and 6G is expected to achieve higher
levels of reliability and security than 5G. With the popularization of robots and drones and the
expansion of radio coverage to the sky, etc., there is a possibility that highly-reliable
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communications in not only limited areas such as factories but also wider areas will be required,
and actualization of highly-reliable communications in various scenes is also expected.
Figure 3-6. Extreme-reliable communication
3.6. Extreme-massive connectivity & sensing
Wearable user devices and an extremely large number of IoT devices that collect images and
sensing information of the real world are expected to spread further in the 6G era, and an
extremely large number of connections that are approximately 10 fold (= 10 million devices per
square km) more than the 5G requirements are expected. In addition to the approach of
connecting a large number of IoT devices to a network, the wireless communication network itself
is expected to evolve to have functions for sensing the real world such as positioning and object
detection using radio waves. In particular, the study of positioning has already advanced for 5G
evolution, and it is expected that ultra-high-precise positioning with the error of several centimeters
or less can be achieved in some environments.
Figure 3-7. Extreme-massive connectivity & sensing
4. Technological Study Areas
Figure 4-1 shows an image of technological evolution from the past mobile communication
generations to 6G. In the previous generations, there was one representative technology in each
generation. However, since 4G, radio access technology (RAT) has comprised a combination of
multiple new technologies based on orthogonal frequency-division multiplexing (OFDM), and in
6G, technical fields are thought to become more diversified. This is because the communications
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quality close to the Shannon limit has already been achieved by technology based on OFDM, and
at the same time, requirements and use cases will be further expanded as described in the
previous chapter.
Therefore, in 6G, high-level requirements as described in the preceding chapter will be satisfied
through a combination of many technologies. Additionally, the definition of 6G RAT also needs to
be clarified. The technical fields considered as candidates for 5G evolution and 6G are outlined
below.
1G
2G
3G
4G
NR
FDMA
TDMA
W-CDMA
OFDM-based
MIMO
Turbo coding
IoT
OFDM-based
cmW & mmW
mMIMO
LDPC/Polar coding
URLLC/mMTC
Future
RAT?
eLTE
eNR?
OFDM-based and/or new waveform
cmW & mmW & THz
Extreme coverage
New NW topology
Further enhanced mMIMO
Enhanced URLLC/mMTC
AI for everywhere
5G (= eLTE + NR)
6G (definition is FFS)
Generation
Performance
6G will be a combination of new technologies
and enhancements to bring “Big gain”
Figure 4-1. Technological evolution up to 6G in mobile communications
4.1. New network topology
When ultra-high speed, high capacity (especially uplink), and improvement in the reliability of
wireless communications are pursued, it is ideal to communicate at as close a distance and in an
unobstructed environment (low-loss path) as possible, and to generate as many communication
paths as possible to increase path selection candidates (increase redundancy). To achieve this, a
network topology that is distributed in the space domain is required. In the previous generation, it
was considered ideal to construct a cellular network with hexagonal cells so that the cells do not
interfere with each other; however, in order to increase the path selection, a topology of spatially
non-orthogonal distributed networks will be pursued by abandoning the concept of cells as shown
in Fig. 4-2. The topology of such a distributed network is considered to be familiar with the
development of high frequency bands, wireless sensing, and wireless power supply.
On the other hand, according to conventional common sense, this new network topology is not a
good network configuration because inter-cell interference occurs and many redundant antennas
are installed. It seems that interference can be technically avoided by beam control and path
selection, but the fundamental problem of how to achieve this at low cost remains. Various
approaches are considered, but the solution will be one that does not use conventional base
station antennas.
There are various investigations such as using glass antennas [4-1, 4-2], reflectors [4-3],
integration of sensors and communication antennas, cooperation between terminals [4-4],
terminal-like base stations, a new optical fiber distribution and optical transmission technology that
enables the distributed network topology, extension of front-haul and back-haul technology
including integrated access and backhaul (IAB) [4-5], and an uplink-only-receiving node. In order
to make the new network topology function more efficiently and effectively, topology management
and control technology using AI, etc. will be an important element. Furthermore, considering a
network topology that utilizes these in combination with a conventional cellular composition seems
to be necessary.
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New-type deployment
Legacy deployment
Small node on traffic
lights or street lights for
road coverage Small node mounted
in signboard or
vending machine
FWA with extensions
for O2I coverage
Mobile relay node
Reflector
FWA for O2I coverage
Coordinated and fixed topology Overlapped and dynamic topology
Figure 4-2. Concept of new network topology
4.2. Coverage extension including non-terrestrial network
Coverage extension technology is required in order to provide services for drones, flying cars,
ships, and space stations, since their service areas such as the sky, sea, and space are not fully
covered by conventional cellular networks. Therefore, new network topologies should be
examined three-dimensionally including the vertical direction. In addition, a technology that
achieves long distance wireless transmission over several tens of kilometers is considered to be
necessary mainly on the assumption of the wireless backhaul and IAB application.
In super coverage extension, by considering the utilization of geostationary satellites (GEO), low
earth orbit satellites (LEO), and high altitude pseudo satellites (HAPS), it becomes possible to
cover mountainous and remote areas, sea, and space, and to provide communication services to
new areas [4-6]. In particular, HAPS has attracted attention again recently because it can be
stationed at a fixed location at an altitude of approximately 20 km, and can form a wide coverage
area with a cell radius of greater than 50 km on land. As shown in Fig. 4-3, in addition to the broad
coverage mentioned above, HAPS has the advantages of providing a backhaul to portable base
stations in a timely and simple manner, and of securing independence from land-based
communication networks (public networks). HAPS is considered to be effective not only as a
disaster countermeasure but also for many industry use cases expected in 5G evolution and 6G.
Disasters
MBB/IoT for wider area coverage
including non-terrestrial networks
High-speed wireless backhaul
for temporary industrial network
Wide-coverage backhaul for
non-terrestrial group mobility
Rural area coverage
HAPS Key Benefits 5G/6G Use Cases
Coverage
• Extremely wide coverage even
in sky, sea, remote island, …
Timeliness
• Easy deployment of portable
base stations
Dedicated
• Independency from public
cellular networks
Figure 4-3. HAPS benefits and use cases
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4.3. Frequency extension and improved spectrum utilization
In 5G NR, frequency bands up to 52.6 GHz are supported, and extension to approximately 100
GHz is examined for future release. In addition, the U.S. FCC recommends that frequencies
higher than 5G, such as 95 GHz to 3 THz, be considered for 6G [4-7]. In such high frequency
bands from the upper part of the millimeter wave band to the “terahertz wave” band, a remarkably
wide frequency bandwidth can be utilized even in comparison to 5G, and is under investigation to
achieve extreme high data rates exceeding 100 Gbps [4-8, 4-9]. At present, as shown in Fig. 4-4,
we assume that radio waves up to approximately 300 GHz are considered in the examination
range for 6G. However, “terahertz waves” have the problem in that the radio wave rectilinear
property is higher than that for the millimeter wave and do not propagate far. Technological
examination such as advance in Radio Frequency (RF) device technology and utilization based on
the above-mentioned new network topology is necessary.
Fig. 4-4 shows the concept of wireless access technology that takes into account the
development of such high-frequency bands and the aforementioned coverage extension including
the sky, sea, and space. Although these are different directions of development, there are
common technical problems in the sense that coverage and power efficiency become more
important than the spectrum efficiency. As for radio technology, the signal waveform of a single
carrier becomes dominant compared with OFDM, and as the application area for radio technology
is expanded including IAB in the future, the importance of radio technology such as in terms of a
power efficient single carrier may increase [4-10, 4-11].
In addition, when new frequency bands such as the millimeter wave and terahertz wave bands
are added to the existing frequency band, very wide frequency bands will be utilized in comparison
to the past. Therefore, there seem to be many related study fields such as optimizing the selected
application of multiple bands according to the application, reexamining the frequency reuse
method between cells, upgrading the duplexing method in the uplink and downlink, and
reexamining the utilization method of the low frequency band.
Frequency
Coverage
3GHz 30GHz 300GHz
FR1 FR2
100GHz
Initial 5G
(FR3) (FR4) (FR5)
Beyond 5G
10GHz
Sky Sea Space
Extreme coverage
New coverage areas that current cellular
system does not support
>100Gbps data rate
New frequency bands
with very wide bandwidth
Extreme high
data rate/capacity
Spectrum efficiency Power efficiency
Power
efficiency
Spectrum
efficiency
Power efficient transmission will
be important part of future RAT
High quality sensing
Figure 4-4. Expansion of radio access technology for exploiting new frequency and coverage
4.4. Further advancement of wireless transmission technologies
In 5G, massive MIMO (mMIMO) technology using multiple antenna elements was one of the
keys, especially as a technology to utilize millimeter waves effectively [1-1]. In 5G evolution and
6G, further advancement is expected such as mMIMO with more antenna elements, more layers
14
for spatial multiplexing [4-12], and distributed antenna arrangement combined with new network
topology.
In regard to the radio access technology almost reaching the Shannon limit in the OFDM-based
technology, faster-than-Nyquist (FTN) signaling, which compresses and transmits signals
non-orthogonally using a sampling rate faster than the frequency bandwidth in the time domain, is
studied. It is difficult to exceed the Shannon limit even by using FTN when considering a certain
propagation path within a given bandwidth, but when considering other factors such as the
peak-to-average power ratio (PAPR), FTN may provide benefits [4-13]. Furthermore, as shown in
Fig. 4-5, virtual massive (VM)-MIMO technology has been proposed as a technology for achieving
a spatial multiplexing gain equivalent to mMIMO with a single antenna [4-14]. In the VM-MIMO
technique, as in FTN, the received sampling rate is faster than the frequency bandwidth. The
antenna characteristics are varied at a very high speed and periodically to generate a large
number of virtual antennas and to increase the number of layers for spatial multiplexing. Since it is
not bound by Shannon limit conditions, it is considered to have the theoretical potential to obtain a
large gain, although problems such as applicable conditions and feasibility in a real environment
remain.
・・・
Tx antennas
Fast
samp
ling
Varied antenna
characteristics
Time
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 41 2 3 4 1 2 3 41 2 3 4 1 2
Rx antenna Waveform
・・・
Waveform for
virtual antenna #1
Waveform for
virtual antenna #2
Waveform for
virtual antenna #3
Sampling points
・・・
・・・
・・・
Pick up the same
channel condition
Figure 4-5. Non-orthogonal transmission using sampling rate faster than frequency bandwidth
(e.g. VM-MIMO)
4.5. Enhancement for URLLC and industrial IoT networks
In many industrial use cases, guaranteeing the required performance level is necessary such as
in remote control and factory automation, and a highly efficient actualization method of a network
(individual network) specialized for the industry that is different from the best effort type service of
a public network has been a topic of interest recently. In addition to the “Local 5G” discussed in
Japan, many companies have participated in global study projects such as 5G-ACIA [4-15]. There
is a wide variation in the requirements based on each industry and application, and while there are
some cases that do not always require a low delay, very severe cases in which not only the
average delay must be low but also a stable low delay without fluctuation is required are assumed.
As shown in Fig. 4-6, various options are considered for network configuration and mobility
between public networks and industrial networks, and are discussed in 5G-ACIA, etc.
15
eLTE cell
NR cell Dedicated NW
Public NW (best effort)
Guaranteed
performance
Best effort
performance
Spectrum
Interference coordination
Interworking
SA vs. NSA
Figure 4-6. Overlays of public and industrial networks
4.6. Expanded integration of variable wireless technologies
When the technical domain of mobile communications is expanded to support broader use
cases, cooperation and integration with wireless technologies other than mobile communications
specialized for various existing applications must be considered. As with 5G, cooperation must
continue with unlicensed band wireless communications such as wireless LAN. In addition,
cooperation with wireless communications using waves other than radio waves, such as
underwater acoustic communications [4-16], is also considered. Furthermore, license assisted
access (LAA) [4-17] and integrated use of access links and backhaul links, i.e., IAB, are one
example, but an approach to integrate wireless technologies using different specifications and
frequencies into the mobile communication system is also conceivable. These will aid in
establishing an ecosystem that can support a wider range of use cases.
5G evolution and 6G system
WLAN/
WPAN
NFC Broadcast Satellite
Cellular
Figure 4-7. Expanded integration of variable wireless technologies
4.7. Multi-functionalization and AI for everywhere in mobile network
In cyber-physical fusion, images and various sensing information are transmitted to networks
through IoT devices. Therefore, some technical fields are considered to analyze such information
by AI and to apply it to the upgrading of radio communication control such as beam control and
propagation path estimation. For instance, the use of AI is considered to enhance the latency and
reliability of non-orthogonal multiple access (NOMA) [4-18], or to anticipate the changing
environment and autonomously arrange transportable base stations in the optimum location at all
times [4-19].
The evolution to utilize radio waves of wireless communications for various applications other
than information transmission is also promising, and the application to sensing such as positioning
and object detection [4-20, 4-21], and wireless power supply technology (e.g., energy harvesting
[4-22]) are considered. In particular, high frequency bands such as the millimeter wave and
terahertz wave bands are suitable not only for high speed and high capacity communications but
also for achieving high precision positioning and sensing. The study of positioning in particular is
advanced even in 5G evolution, and it is expected that ultra-high-precise positioning with the error
of several centimeters can be achieved in some environments. Here, the utilization of AI
technology is key. It may be used in all areas of the radio communication system, and in the future,
potentially in the design of the radio interface itself.
16
5. Conclusion
In this white paper, 5G evolution, which is the enhancement of 5G, and the direction of the
evolution of mobile communication technologies for 6G assuming the society and the worldview in
the 2030s are examined, and requirements, use cases, and concepts pertaining to technical
examination are described.
In the future, while 5G is expected to be utilized in various industrial fields, conducting research
and development aiming at the further future of 5G is desirable by looking at future market trends,
needs, social problems, and technological evolution. NTT DOCOMO will continue to enhance the
ultra-high-speed, high-capacity, ultra-reliable, low-latency and massive device-connectivity
capabilities of 5G technology. It will continue its research into and development of 5G evolution
and 6G technology, aiming to actualize technological advances including the following.
The simultaneous achievement of several requirements such as ultra-high-speed,
high-capacity, and low-latency connectivity
The pioneering of new frequency bands including terahertz frequencies
The expansion of communication coverage in the sky, at sea, and in space
The provisioning of extremely low energy and low-cost communications
The ensuring of extremely reliable communications
The developing of capabilities for extremely massive connectivity and sensing
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