Content uploaded by Madhusanka Liyanage
Author content
All content in this area was uploaded by Madhusanka Liyanage on Oct 07, 2022
Content may be subject to copyright.
1
A Survey on the Use of Blockchain for Future 6G:
Technical Aspects, Use Cases, Challenges and
Research Directions
Anshuman Kalla, Chamitha de Alwis, Pawani Porambage, G¨
urkan G¨
ur, Madhusanka Liyanage
Abstract—While 5G is at the early deployment state around
the globe, the research and industrial communities have already
started concentrating their efforts on formulating the overall
6G vision comprising requirements, key enabling technologies,
performance indicators, and applications. Following the trend,
it is evident that 6G will emerge as highly softwarized and
open networks allowing the participation of multiple stake-
holders. This undoubtedly will make 6G more flexible, agile,
autonomous, intelligent, and cost-efficient networks. However,
the programmability and openness will make 6G networks more
prone to issues like security, privacy, traceability, interoperability,
auditability, resource manageability, spectrum efficiency, and 3D
mobility. To address these issues, a deep integration of blockchain
technology with 6G networks is foreseen. Thus, we aim to put
together blockchain and 6G under a magnifying lens to gain
a comprehensive understanding of the role of blockchain in
the 6G ecosystem. We begin by providing an overview of the
envisioned 6G networks and blockchain technology. Next, we
present a high-level view of the role of blockchain for 6G trends
and requirements. Following that, we conduct an in-depth study
on how the blockchain can provide a secure, transparent, and
decentralized underpinning to various technical aspects and use
cases of 6G. Thereafter, we discuss the deployment challenges
to be faced while integrating blockchain in 6G and the possible
solutions. Finally, future research directions are expounded to set
the floor for further advancements in the blockchainized 6G.
Index Terms—6G Networks, Telecommunications, Blockchain,
Distributed Ledger Technology.
I. INTRODUCTION
The evolution of mobile networks has come a long way
and has hitherto fulfilled the market demands as well as users’
expectations. The time has come for the world to experience
and enjoy the services offered by the fifth-generation (5G)
of mobile networks. It is going to radically change the
way humans and machines communicate, interact and stay
Anshuman Kalla is with the CGPIT, Uka Tarsadia University (UTU), India,
email: anshuman.kalla@ieee.org
Chamitha de Alwis is with the School of Computer Science and Technology,
University of Bedfordshire, United Kingdom and Department of Electrical and
Electronic Engineering, University of Sri Jayewardeneprua, Sri Lanka, email:
chamitha@ieee.org
Pawani Porambage is with VTT Technical Research Centre of Finland,
email:pawani.porambage@vtt.fi
G¨
urkan G¨
ur is with the Institute of Applied Information Technology (InIT),
Zurich University of Applied Sciences (ZHAW), Winterthur, Switzerland,
email: gueu@zhaw.ch
Madhusanka Liyanage is with the School of Computer Science, University
College Dublin, Ireland and Centre for Wireless Communications, University
of Oulu, Finland, email: madhusanka@ucd.ie
This work is partly supported by Academy of Finland under 6Genesis (grant
no. 318927) project and Science Foundation Ireland under CONNECT phase
2 (Grant No: 13/RC/2077 P2)
connected. Distinctively, 5G supports three different broad
traffic classes namely eMBB (enhanced Mobile Broadband),
URLLC (Ultra-Reliable and Low Latency Communication),
and mMTC (massive Machine Type Communications) [1], [2].
These are designed to meet heterogeneous and customized
demands of individuals as well as network tenants such as
industry verticals, mobile virtual network operator (MVNO),
Over The Top (OTT) service providers [3]. Moreover, vari-
ous new technologies such as Software Defined Networking
(SDN), Network Function Virtualization (NFV), Multi-access
Edge Computing (MEC), Network Slicing (NS), Cloud Com-
puting (CC), Non-Orthogonal Multiple Access (NOMA), and
massive Multiple-Input Multiple-Output (MIMO) drive the 5G
ecosystem and help achieve the 5G vision [4], [5].
Nevertheless, the research community already has identified
numerous gaps that will not be filled through 5G even with
its full capacity. For instance, 5G, in line with its predecessor
generations, remains confined to cell-based communications
that offer primarily ground coverage [6]–[8]. Further, even
with 5G, a significant portion of the earth will remain uncon-
nected and uncovered which includes large bodies of water,
areas with low (or negligible) population, deep deserts, and
mountains [9]. Hence, 5G’s state-of-art and its ongoing ini-
tial deployments reveal many limitations when one envisions
future requirements [7]. Hence, in a decade or so, even with
5G technology it would be difficult to scale up and meet the
diverse demands (in terms of traffic, connection density, and
services) of the hyper-connected future era. This understanding
has impelled a new wave of interest in the next generation
of mobile networks which is touted as the 6G. At present,
with a resurgence of research activities around the globe, the
research and industrial community is formulating the overall
vision, exploring the potential use cases, defining the future
requirements, and identifying the key enabling technologies
for 6G [1].
6G, the future generation of wireless communication sys-
tem, is envisioned to lay the foundation of a new era of hyper-
connected and artificially intelligent societies [10]. It would
enable complete digitization, mobilization, and automation
with seamless integration of heterogeneous networks spanning
over space, air, ground, underground and undersea, thereby
paving the way for universal communication system [11]. For
instance, the use of Unmanned Aerial Vehicles (UAVs) as
Aerial Base Stations (ABS) will extend the reach of ground
stations enabling better coverage and cell-free communica-
tions. Integrating heterogeneous networks in 6G calls for a
2
TABLE I
SUMMARY OF IMPO RTANT ACRONYMS
Acronym Definition
5G Fifth Generation
6G Sixth Generation
ABS Aerial Base Stations
AI Artificial Intelligence
AP Access Point
API Application Program Interface
AR Augmented Reality
BaaS Blockchain as Service
BANs Body Area Networks
BCI Brain-Computer Interfaces
BS Base Station
CAV Connected Autonomous Vehicles
DApps Decentralized Applications
DDoS Distributed Denial of Service
DLT Distributed Ledger Technology
DSA Dynamic Spectrum Access
EHR Extremely High Reliability
EI Energy Internet
ELPC Extremely Low Power Communications
eMBB enhanced Mobile Broadband
eURLLC extremely Ultra Reliable Low Latency Communications
FeMBB Further-enhanced Mobile Broadband
GAA general authorized access
Gbps Gigabits per second
H2H Hospital-to-Home
IIoMT Intelligent Internet of Medical Things
IoE Internet of Everything
IoT Internet of Things
IWD Intelligent Wearable Devices
L5GO Local 5G Operators
LAA Licensed-Assisted Access
LBT Listen-Before-Talk
LDHMC Long Distance and High Mobility Communications
LEO Low Earth Orbit
LoS Line-of-Sight
M2M Machine to Machine
MaaS Mobility-as-a-Service
MANO Network Management and Orchestration
MIMO Multiple-Input and Multiple-Output
ML Machine Learning
mMTC massive Machine Type Communications
MNOs Mobile Network Operator
MR Mixed Reality
PAL Priority Access License
PAT Process Analysis Toolkit
PHY Physical
PoW Proof of Work
PUs Primary Users
QC Quantum communication
SAS Spectrum Access System
SIR Signal-to-Interference Ratio
SNR Signal-to-Noise Ration
SUs Secondary Users
TDD Time Division Duplex
THz Tera Hertz
UAV Unmanned Aerial Vehicle
UE User Equipment
uHDD ultrahigh Data Density
umMTC ultra-massive Machine Type Communication
URLLC Ultra Reliable and Low Latency Communication
V2X Vehicle-to-everything
VLC Visible Light Communication
VoIP Voice over IP
VR Virtual Reality
XR Extended Reality
ZSM Zero-touch network and Service Management
unified framework comprising of key enabling technologies
like Artificial Intelligence (AI), Blockchain, Visible Light
Communication (VLC), quantum communications, and Ter-
aHertz (THz) communications [7], [9], [12]. Moreover, 6G is
believed to go beyond conventional RF-based communications
and embrace various other propagation media like sonar waves
for underwater, optical fiber for the fronthaul and the backhaul,
and magnetic induction for underground communications [13].
Undoubtedly, 6G has to meet the predicted explosive growth
in terms of the number of connected devices as well as the
exponentially increasing traffic demands. As per CISCO, by
2030, 500 billion devices would be connected across the
globe, which will be of the order of 59 times more than the
human population by then [10]. The traffic is estimated to
be 607 exabyte/month by 2025 and 5016 exabyte/month by
2030 [14]. Major contributors to this expected traffic will be
video traffic and the M2M communications traffic [14]. The
trend exhibits that the prominent users of 6G are going to be
machines/devices thus network services will be more machine-
centric than human-centric. The fascinating range of new
devices that will proliferate the space of connected devices
will be AR (Augmented Reality) glasses, VR (Virtual Reality)
headsets, hologram devices, swarm robots, home appliances,
range of sensors of autonomous vehicles, industrial machines,
and Internet of Everything (IoE) devices [10].
6G networks are envisioned to be softwarized, virtualized,
customized, cloudified, edgified, intelligent, autonomous and
self-sustainable [15]. Security and privacy of such open and
programmable networks will be one of the indispensable archi-
tectural requirements. Some of the identified technologies that
will play a cardinal role in this direction include blockchain
technology, native Artificial Intelligence (AI), quantum com-
puting and communication, and Physical Layer Security (PLS)
techniques [9], [16].
Some of the captivating applications to be offered by 6G are
VR, AR, MR (Mixed Reality) and XR (Extended Reality) ap-
plications [17], M2M type subscription and applications [14],
3D holographic imaging and presence [18], [19], 5D com-
munications (sight, hearing, touch, smell and taste) [18],
VLC (Visible Light Communications) [20], smart clothing
and wearables, fully autonomous (Level-5 [21]) and connected
vehicles, and accurate indoor positioning [22].
In a nutshell, the envisioned motive of 6G networks revolves
around the following:
•To offer a universal communication system integrating un-
derwater, ground, air, and space networks.
•To effortlessly accommodate a proliferation of heteroge-
neous devices emerging from IoE.
•To proactively meet the futuristic traffic demands.
•To offer strict Quality-of-Service (QoS) for new heteroge-
neous traffic classes and services.
•To open a new landscape of business opportunities with
strong consideration for network tenants and industry ver-
ticals.
•To pave the way for an unseen fleet of real-time and AI-
powered applications.
A. Paper Motivation
Blockchain, one of the most popular types of distributed
ledger technology, has been identified as a key enabler for
3
mobile communication systems. Already its applicability in
5G networks has been a hot research topic in the recent
past [23], [24]. Since the future generation of mobile net-
works, especially 6G, is going to be increasingly softwarized,
decentralized, and open systems thus the underpinning of
blockchain technology is believed to be indispensability for
secure and complete automation. In particular, there are
technical aspects (such as security, privacy, network service
management, resource utilization, and spectrum management
discussed in detail in section V)) and applications of 6G (such
as healthcare, energy Internet, UAVs, CAVs, and XR presented
in depth in section VI) that are expected to be enhanced with
the use of blockchain technology . In this context, researchers
have already started exploring the role of blockchain in 6G
networks [25]–[27].
B. Selection Method
The aim of this paper is to put the integration of blockchain
technology for 6G under the magnifying glass to provide an
in-depth understanding of a wide range of benefits that can be
achieved with the use of blockchain technology in 6G era. In
particular, the motivation is to answer set of research questions
when leveraging blockchain technology in conjunction with
smart contracts for 6G. Table II provides section-wise research
questions and the search keywords that were used for the
search process. Various databases such as IEEExplore, ACM,
Scopus, and Web of Science have been used to gather all the
papers that fall within the scope of the this survey. Although,
references used for this survey paper were published between
2002 and 2022, however, majority of the references (more than
200 out of total 380 references) are from year 2020 and 2021.
This is evident since research community gained momentum
towards 6G since 2018, and specially the work regarding use
of blockchain in 6G has picked up since 2019. Thus, this paper
provides in-depth survey of latest research work that have been
performed considering blockchain and smart contracts for next
generation mobile networks, i.e., 6G.
Table III summarises the relevant works concerning the use
TABLE II
SEC TIO N-WISE RESEARCH QUESTIONS AND SEARCH KEYWORDS
Section Research Questions Search Keywords
Section II - Background of
6G
•What are the trends expected by 2030 which will drive the 6G
applications and services?
•What are the technologies that will be required to enable new set of
applications and services in the 6G era?
•What is 6G’s vision, and how the technical requirements of 6G are
different then its predecessor?
6G trends, 6G applications, 6G tech-
nologies, 6G requirements, and 6G vi-
sion
Section III - Blockchain
and Smart Contracts
•What is blockchain technology and why it is one of the most popular
type of DLT?
•What are the different types of blockchain and their characteristics?
•What are smart contracts and their benefits when deployed on top of
blockchain?
•What are the salient features of blockchain-enabled system?
Blockchain, DLT, type of blockchain,
smart contracts, and feature or charac-
teristics of blockchain
Section IV - Blockchain
for 6G Trends and Re-
quirements
•How blockchain and smart contracts together can support 6G trends,
from bird’s point-of-view?
•Given the 6G technical requirements, how blockchain-powered 6G can
help achieve these requirements?
6G trends, 6G requirements, 6G ser-
vices with blockchain and smart con-
tracts.
Section V - Blockchain
for 6G Technical Aspects
•What are the 6G’s technical aspects which are either new or enhanced
version of it predecessor?
•What are the challenges envisioned to implement these 6G technical
aspects, and how blockchain together with smart contracts can mitigate
them?
•What are both the pros and cons of leveraging blockchain for 6G
technical aspects by studying the existing research works?
3D networking, heterogeneous net-
works, dynamic spectrum management
or sharing, security, privacy, access
control, resource management, network
slicing, intelligent networks, mobility,
ZSM, edge computing, tactile internet,
and quantum computing with 6G, and
blockchain and smart contracts.
Section VI - Blockchain
for 6G Use Cases and Ap-
plications
•What are the fleet of innovative use cases and applications expected in
6G era?
•Which challenges are to faced while realizing these 6G use cases and
applications?
•How can blockchain and smart contracts address these challenges?
•What are the down side of employing blockchain for 6G use cases and
applications, in addition to the envisaged benefits?
Industry 5.0, CPS, IIoT, smart health-
care, IIoMT, MIoT, UAVs, CAVs, En-
ergy Internet, Smart Grid 2.0, Holo-
graphic telepresence, smart cities, Dig-
ital Twins with 6G, and blockchain and
smart contracts.
Section VII - Deployment
Challenges
•What are various deployment challenges when using blockchain and
smart contracts for 6G?
•Why these challenges are pertinent in the 6G context?
•What are the possible solutions that can be exploited to overcome these
blockchain-related deployment challenges?
Scalability, decentrality, security, pri-
vacy, consensus algorithms, standard-
ization, legal issues, interoperability
with 6G, and blockchain and smart con-
tracts.
4
of blockchain for 6G networks.
C. Paper Contribution
Given the fact that blockchain has been envisioned as
one of the key enabling technologies for 6G mobile net-
works [17], [33], [15], it is imperative to study various oppor-
tunities and challenges foreseen with its usage. Nevertheless,
to the best of our knowledge, there exists no comprehen-
sive survey that presents the broader and in-depth role of
blockchain technology in 6G. The current paper is the first
attempt to exhaustively survey the cardinal role of blockchain
technology in 6G networks considering both the technical
aspects of 6G and the applications & use cases envisioned
with the underpinning of 6G. The main contributions of this
survey are as follow:
•To explore the driving trends, applications, require-
ments, and key enabling technologies for 6G ecosystem:
The paper discusses the trends that are propelling the
futuristic 6G applications as well as outlines the distinct
requirements of 6G along with the key enabling technolo-
gies. Blockchain is one of the key enabling technologies.
•To provide an overview of blockchain and present
a high-level view of its role towards 6G trends and
applications: Given, the observed trends and the estimated
requirements, a zoom-out view of what blockchain can offer
for 6G is projected. This sets the floor to probe thoroughly
the use of blockchain in 6G ecosystem.
•To investigate blockchain-enabled improvements for
6G’s technical aspects: Next generation of mobile net-
works will demand significant enhancement of the exist-
ing technical aspects in the current generation as well as
new technical building blocks. For every technical aspect
considered, this paper, identifies the key challenges and
investigates how blockchain can play an instrumental role
in mitigating them. Furthermore, efforts have been made to
fairly represent both the pros and cons of using blockchain
for the considered technical aspects.
•To gauge the use of blockchain for the envisioned 6G
use cases and applications: The paper probes the role that
blockchain will play in realizing a fleet of innovative 6G use
cases. In particular, the motive is to comprehensively survey
how the research efforts in the realm of blockchain-enabled
6G use cases are (and will be) shaping up.
•To elaborate deployment challenges encountered with
the use of blockchain for 6G: Despite the promising
role the blockchain can play for enabling various techni-
TABLE III
SUM MARY O F SU RVEY S RE LATE D TO TH E US E OF B LOC KC HA IN IN 6 G ECOSYSTEM
Reference Key Contributions Relevance to Blockchain for 6G
Nguyen et al. [23]
The work is a comprehensive survey on the use of blockchain technology for the key
5G technologies (like MEC, CC, NFV, NS, and D2D communication), 5G services
(such as spectrum management, data sharing, resource management, infrastructure
management, security, and privacy), and 5G applications (such as healthcare, smart
cities, smart transportation, smart grid, and UAVs
The primary focus of the paper is the
integration of blockchain for 5G (tech-
nologies, services, and 5G IoT applica-
tions). Thus, no explicit focus on 6G’s
trends, requirements, technical aspects,
and applications.
Wang et al. [7]
The survey primarily investigates security and privacy issues that are expected in
6G networks. In particular, the authors identify four key areas for 6G (real-time
intelligent edge, distributed AI, intelligent radio, and 3D intercoms), discuss six
key technologies that can drive them, and finally reveals the potential security and
privacy issues that arise with the use of these technologies.
Briefly presents the use of blockchain
(as one of the six identified technolo-
gies) in 6G and related security con-
cerns.
Nguyen et al. [28]
The work presents a brief discussion on security and privacy issues in 6G,
opportunities and challenges in terms of use of blockchain in 6G, and outlines
potential solutions towards mitigation of the challenges.
Briefly introduces the opportunities
where blockchain can be used in 6G
networks.
Liu et al. [29]
A comprehensive survey on joint use of blockchain and Machine Learning (ML)
technologies for communication networks as well as the mutual benefits gained with
their integration (i.e., how blockchain can help ML’s functioning and vice-versa)
In-depth study of convergence of
blockchain and ML for decentralized,
secure and intelligent networks. How-
ever, no explicit focus on 6G.
Sekaran et al. [30] The work elaborates the security-related issues in the landscape of blockchain-
enabled IoT in 6G, and touches on the application of blockchain of things in 6G.
Special focus on blockchain-enabled
IoT systems in future 6G networks.
Yrj¨
ol¨
aet al. [31] An overview on the prospective use of blockchain to create an open business model
comprising of multiple stakeholders in 6G ecosystem.
Confined to the use of blockchain for
a decentralized and trustless business
model for 6G.
Xu et al. [25]
A study on blockchain as a key enabler for infrastructure and resource management
in 6G. The work briefly discusses few application scenarios (IoT, network slicing,
and other sharable resources) where the use of blockchain can be beneficial.
Special emphasis on improving re-
source management in 6G network with
the use of blockchain.
Hewa et al. [32]
The work introduces the general challenges for 6G and presents how blockchain
can be leveraged for 6G ecosystem. It includes some 6G technical aspects and uses
cases that can be improved by blockchain’s underpinning
A short survey that presents a high-
level view of 6G challenges and what
blockchain offers to 6G networks.
Our Work
A comprehensive survey on the key enabling role of blockchain in 6G considering
(i) 6G trends and requirements, (ii) 6G technical aspects (3D Networking, Dynamic
Spectrum Management, Ubiquitous Intelligence, Mobility Management, and more),
and 6G applications and uses cases (such as Industry 5.0, Connected Autonomous
Vehicles (CAVs), Energy Internet, Smart healthcare, UAVs, Holographic Telepres-
nce, Digital Twins.). Also, provides deployment challenges along with the possible
solutions.
An in-depth coverage of use of
blockchain (i) to build a secure,
privacy-protected, decentralized, and
trustless 6G networks, and (ii) to enable
the future 6G uses cases and applica-
tions.
5
Section I: Introduction
Motivation Contribution Outline
Section II: Background of 6G Networks Section III: Overview of Blockchain
Section IV: Blockchain for 6G Trends and Requirements - A High-Level View
6G Driving Trends Blockchain - A Type of DLT
Blockchain for 6G Trends Blockchain for 6G Requirements
6G Applications
6G Technical Requirements 6G Enabling Technologies
Types of Blockchain
Smart Contracts Salient Features
THz Communication
3D Networking
Dynamic Spectrum
Management
Security
Privacy
Resource Management
Ubiquitous Intelligence
Mobility Management
Other Emerging Technical
Aspects
Summary
Role of Blockchain
Key Challenges
Industrial Applications in
Industry 5.0
Smart Healthcare
Unmanned Aerial Vehicles
(UAVs) Applications
Connected Autonomous
Vehicles (CAVs)
Energy Internet (EI)
Other Use Cases
Section V: Blockchain for
6G Technical Aspects
Section VI: Blockchain for
6G Use Cases and
Applications
Structure Followed
Section VII: Deployment Challenges
Scalability (Data) -
Throughput and Storage
Measure of Decentrality
Security and Privacy
Consensus Algorithms
Interoperability
Introduction
Challenges
Possible Solutions
Importance in context of 6G
Introduction
Section VIII: Lessons Learned and Future Research Directions
6G Applications6G Requirements 6G Technical Aspects
Future Directions
Lessons Learned
Section IX: Conclusion
Fig. 1. Outline of this paper
cal aspects and use cases of 6G, there exist deployment
challenges. Use blockchain in 6G ecosystem on the one
hand will bring numerous advantages, but on the other
hand, will encounter integration challenges. Thus, the paper
put the use of blockchain in 6G through the prism of
challenges. Moreover, various possible solutions are also
briefly discussed.
•To present the lessons learned and the future research
directions: As essence of our survey, the paper presents a
concise discussion on the lessons learned for various 6G
technical aspects and use cases. Furthermore, based on the
findings, the paper put forward interesting future research
directions.
D. Outline
The rest of the paper is organized as follows. Section
II presents the trends that is driving the new applications
envisaged with 6G networks. Moreover, this section also
highlights the requirements (much beyond 5G’s capabilities)
and summarises the key enabling technologies to achieve these
requirements. Section III provides an overview of blockchain
technology. Section V focuses on the use of blockchain
for various technical aspects 6G. Section VI discusses how
blockchain technology provides a solid underpinning to realize
emerging and unforeseen futuristic 6G-enabled use cases. The
deployment challenges stands in the way towards the use of
blockchain in 6G and possible solutions are highlighted in
section VII. Section VIII discusses the lessons learned and
provides the landscape for future research directions. Finally,
the section IX concludes this paper. The overall outline of this
survey paper is depicted in the Figure 1.
II. BACKG ROUND OF 6G NE TW OR K
Fig. 2. Development path towards 6G networks [12], [15], [34]
6G mobile networks are expected to be deployed within
the next decade around the globe [12]. As experienced from
previous mobile generations, a new mobile generation appears
every ten years. Therefore, it is realistic to assume that 6G
will emerge around 2030 [12], [35]. 6G is going to implement
smart and intelligent mobile networks that can satisfy all the
expectations not met with 5G, as well as new requirements to
be defined at a later stage.
6G will play a vital role as the main communication
infrastructure in 2030 and beyond. Therefore, the development
of 6G network will shape up by the future trends of the 2030’s
6
Fig. 3. High-level 6G architecture [1], [12], [35], [38]
world. As illustrated in Figure 2, the future trends in the future
world will define the new applications and services enabled
by 6G network. To realize these new 6G applications and
services, a new set of technologies will be integrated with
mobile networks.
Figure 3 presents the high-level view of 6G architecture.
Among other 6G technologies, the integration of AI, edge AI,
and ML will play a vital role in 6G network [36], [37].
A. 6G Driving Trends
6G will be the key communication infrastructure to satisfy
the demands of future needs of hyper-connected societies in
2030 [12], [15], [34]. Thus, these future demands will drive
the development and define the features of 6G networks.
•Expansion of IoT: It is expected that the number of IoT
devices in the world will grow up to 24 billion by 2030.
Moreover, the revenue related to IoT will hit the market
capitalization of USD 1.5 trillion by 2030 [39].
•Massive Availability of Small Data: Due to the anticipated
popularity of 6G-based IoT devices and new 6G IoT ser-
vices, 6G network will trend to generate an increasingly
high volume of data. Most of such data will be small,
dynamic, and heterogeneous in nature [35], [40].
•Availability of Self-Sustained Networks: 6G mobile sys-
tems need to be energy self-sustainable, both at the infras-
tructure side and at the device side to provide uninterrupted
connectivity in every corner of the world. The development
of energy harvesting capabilities will extend the life-cycle
of both network infrastructure devices and end devices such
as IoE devices [11], [41].
•Convergence of Communication, Sensing, Control, Lo-
calization, and Computing: Development of sensor tech-
nologies and direct integration of them with mobile network
accompanied by low energy communication capabilities will
lead to advanced 6G networks [35], [42]. Such a network
will be able to provide sensing and localization services
in addition to advanced communication and computing
features [35], [42], [43].
•Zero Energy IoT: Generally, IoT devices will consume
significantly more energy for communication than sensing
and processing [44]. The development of ultra-low-power
communication mechanisms and efficient energy harvesting
7
mechanisms will lead to self-energy sustainable or zero
energy IoT devices [44].
•More Bits, Spectrum, and Reliability: The advancement
of wireless communication technologies including coding
schemes and antenna technologies will allow the utilization
of new spectrum as well as reliably send more information
bits over existing wireless channels [12], [35].
•Gadget-free Communication: The integration of an in-
creasing number of smart and intelligent devices and digital
interfaces in the environment will lead to a change from
gadget-centric to user-centric or gadget-free communication
model. With such a transition, the user will be able to
communicate with the hyper-connected digital surroundings
without any devises. The “omnipotential” environment is
smart enough to provide the necessary information, and
digital services according to the user requirements [45]–
[47].
•Increasing Elderly Population: Due to factors such as
advanced healthcare facilities and the development of new
medicines, the older population in the world is increasing
rapidly. According to “An Aging World: 2015” report,
nearly 17 percent (1.6 billion) of the world’s population
will be aged 65 and over by 2050 [48].
•Emergence of New Technologies: By 2030, the world will
experience new technological advancements such as stand-
alone cars, AI-powered automated devices, smart clothes,
printed bodies in 3D, humanoid robots, new AR devices,
quantum computing, and space travel [12], [35]. 6G will be
the main underlying communication infrastructure to realize
these technologies.
B. 6G Applications
A new set of 6G applications will appear due to above-
mentioned 6G trends. Some of these important 6G applications
are discussed below:
•UAV based Mobility: The popularity and progress of
research and development (R&D) activities related UAV
based services are improving around the globe. This will
lead to use UAVs in new domains such as taxi services,
logistics, passenger transport, and military operations [49],
[50].
•Holographic Telepresence: is another exciting 6G appli-
cation. Using holographic telepresence, it is possible to
real-time project distant objects including people as full-
motion 3D images. Due to a high level of realism to the
actual physical presence, holographic telepresence useful
for applications such as, meeting, conferences and news
broadcasting [51], [52].
•Extended Reality (XR): 6G is believed to offer extended
reality which can combine real and digital/virtual envi-
ronments. XR terms expands over mulpiple technologies
i.e., Augmented Reality (AR), Virtual Reality (VR), Mixed
Reality (MR), and everything in between [53], [54].
•Connected Autonomous Vehicles (CAV): With more than
40 companies active contribution for R&D activities in CAV
domain, the future human society will soon experience the
fully autonomous, highly reliable, and commercially viable
autonomous vehicles [55].
•Internet of Everything (IoE): Current IoT ecosystem will
evolve further to the Internet of Everything (IoE) which
interconnects not only things but also people, processes and
data itself [56].
•Smart Grid 2.0: Energy networks will evolve from Smart
grid 1.0 which is about installing interconnected smart
meters and getting them integrated, to Smart Grid 2.0 which
will actually do more advanced things such as automated
meter data analysis, dynamic pricing, prepayments, and
intelligent line loss analysis. Smart Grid 2.0 offers the
distribution grid management automation via a self-healing,
digitally controlled energy network for reliable electric
power delivery [57].
•Industry 5.0: 6G will provide a solid underpinning for
next generation of industries, i.e., Industry 5.0. It enables
co-working concept of people, intelligent robots and smart
machines. In this manner, Industry 5.0 adds the personalized
human touch to the automation and efficiency in Industrial
Internet applications [58].
•Hyper-intelligent IoT: is a next generation of IoT applica-
tion which relies mainly on AI technologies. It will use
AI algorithms to mainly optimize the complex IoT data
processing task to control automated devices such as robots
and UAVs. In this way, hyper-intelligent IoT can use to
implement intelligent digital services [59].
•Collaborative Robots: directly collaborate with people by
work side-by-side with them. These collaborative robots can
perform tedious, repetitive, and risky tasks which are diffi-
cult to do with humans. The use of co-robots can improve
the health and safety of human workers and automate the
production process [60].
•Personalized Body Area Networks(PBANs): is a short-
range network which basically deploy around or within the
human. PBAN are important to implement integrated mo-
bile health (mHealth) systems. These mHealth systems are
used to perform health monitoring and personalized health
management. mHealth systems deploys multiple sensors
within the human body to collect health information. PBAN
interconnects these sensors to enable dynamic exchange of
the collected information [61].
•Intelligent Healthcare: is the next generation of health-
care systems. Novel AI technologies will use in ehealth
sector realize this new intelligent healthcare systems. New
devices such as Intelligent Wearable Devices (IWD) and
Intelligent Internet of Medical Things (IIoMT) will use
to implement Hospital-to-Home (H2H) services and hyper-
connected smart hospitals [38], [62].
C. 6G Technical Requirements/Vision
The technical capabilities of 6G networks have to improved
to to realize new 6G applications. Thus, technical requirement
of 6G networks should extend the capabilities of 5G networks.
6G networking requirements can be divided into different
categories as follows:
•Further enhanced Mobile Broadband (FeMBB): The mo-
bile broadband speed should exceed the limits of 5g network
and offer the peak data rate at Terabits per second (Tbps)
8
level. Moreover, the user-experienced data rate should also
increase to Gigabits per second (Gbps) level [38].
•Enhanced Ultra-Reliable, Low-Latency Communication
(ERLLC/eURLLC): The E2E latency in 6G should be
further reduced up to µs level to enable new high-end real-
time 6G applications [15].
•Ultra massive Machine Type Communication (umMTC):
Connection density will further increase in 6G due to
the popularity of IoT devices and the novel concept of
IoE. These devices communicate with each other and offer
automated services collaboratively [63], [64].
•Extremely Low-Power Communications (ELPC): The
network energy efficiency of 6G will be improved by 10x
than 5G and 100X than 4G. It will enable extremely low
power communication channels for resource-constrained
IoT devices [15], [65].
•Long Distance High-Mobility Communications
(LDHMC): With the support of fully integrated
satellite technologies, 6G will provide communication
for extreme places such as space and the deep sea. Satellite
communication is said to have potential to enable Internet
of Remote Things (IoRTs) [66]. Moreover, AI-based
automated mobility management systems and proactive
migration systems will be able to support seamless mobility
at speed beyond 1000 kmph [38].
•High Spectrum Efficiency: The spectrum efficiency will
be further improved in 6G up to five times as in 4G and
nearly two times as in 5G networks [15].
•High Area Traffic Capacity: The exponential growth of
IoT will demand the improvement of the area traffic capacity
by 100 times than 5G networks. It will lead up to 1 Gbps
traffic per square meter in 6G networks.
In addition to the above network level requirements, 6G
networks are expected to deliver high security,high privacy
and high reliability to enable new 6G applications.
Figure 4 maps the key requirements of 6G with the services
and applications enabled by 6G networks.
D. 6G Enabling Technologies
Several technologies will play a crucial role in realizing
novel 6G applications and satisfying the requirements of 6G
networks.
•AI/ML: The concept of creating intelligent machines that
can simulate human thinking and human behavior is called
AI [67]. Machine learning allows machines to learn about
a process or performing a task from analyzing only data
without being programmed explicitly [68]. Thus, ML is
considered a subset of AI.
•Edge AI: is focusing on running AI algorithms locally at
the edge of the network with limited resources and very
low E2E latency. Due to limitations in edge computers,
these edge AI models/algorithms can be pre-trained in the
cloud for optimized results and can then be moved to the
edge [69].
•Above 6GHz Radio Frequency: With the greater use
of small cells and emerging advances in communication
technology, 6G will be able to support the use of higher
frequencies in future use cases [70].
•Blockchain/DLT: Distributed Ledger Technology (DLT)
is a decentralized, secure and immutable database that is
managed by multiple users. It will play a vital role in
enabling many 6G services [32].
•Swarm Networking: is the concept of managing a group
of network elements or users as a part of a swarm. 6G
will need to use swarm networking concepts to efficiently
manage a swarm of edge devices, UAVs, or robots, due to
the collaborative nature of these elements [71].
•Zero touch network and Service Management (ZSM):
is the concept of enabling full end-to-end automation of
network and service management to deliver services in an
agile, high speed, and scalable manner [72].
•Smart Surfaces: In the near future, the novel smart surfaces
will be inherently intelligent to offer services. They will
evolve from the current form to integrate smart technology
onto the surfaces of furniture, buildings, and vehicles. Thus,
these smart surfaces will combine the materials science of
smart materials with IoT and big data analysis to offer
dynamic, reconfigurable, and digitally controllable surfaces
[73].
•Quantum Communication: With the development of quan-
tum computing research, 6G may utilize quantum infor-
mation processing and quantum teleportation to enable
quantum communication. One of the most interesting ap-
plications of quantum communication is the protection of
information channels against eavesdropping using quantum
cryptography [74].
III. OVERVIE W OF BLOCKCHAIN
In recent years, the rise of DLT, in particular blockchain
technology, has gained significant momentum and has been
embraced by the industry and research communities. This
section briefly covers the basic concepts, types of blockchain,
smart contracts, and salient features of blockchain.
A. Blockchain - A Type of DLT
Blockchain is a type of distributed ledger which is main-
tained in a decentralized manner by the underlying P2P
network of nodes. As the name implies, blockchain comprises
of series of blocks of transactions that are logically chained or
linked together to form a digital ledger. Transactions occurring
in a given time frame are verified and then bundled together
in a unit called as block. So, each block contains a finite set
of transactions. All these blocks are logically linked together
in the order of their creation using cryptographic hashes.
This is to say that every block stores the hash value of the
previous block in the ‘previous block hash’ field. The first
block, aka genesis block, does not have any previous block.
Thus, the previous block hash field of the genesis block is
set to all 0’s. The digital ledger holds all the past transactions
in chronological order and is cryptographically sealed [75].
Further, this ledger is replicated at all the participating nodes
in a P2P blockchain network. With time, the distributed ledger
keeps growing because the write operations are performed in
9
Fig. 4. 6G Requirements vs Applications [11], [35], [38]
exclusively append mode [76]. From a technological view-
point, blockchain is considered as one single technological
innovation which is a unique, and powerful mix of underly-
ing concepts, techniques and technologies [77]. For instance,
blockchain uses cryptographic techniques like Public Key
Infrastructure (PKI), hashing, digital signature, and Merkle
tree. It also utilizes P2P technology for connecting nodes
(aka miners) to establish a blockchain network. Furthermore, a
consensus mechanism allows nodes in the blockchain network
to be synchronized and to agree on the current state of the
distributed ledger.
Blockchain promises to solve the issues like exclusive
peer-to-peer transactions without centralized third parties,
fraudulent replication of digital asset/value or transaction
(e.g., double spending), establishing trust with pseudonymity,
transparent yet immutable record-keeping, provenance and
auditable enabled distributed ledger, and digital signing and
execution of legal agreements (between parties) in the form of
softwarized contracts. The technology is also optionally driven
by incentive mechanisms to attract more nodes to participate
in the decentralized management of the digital ledger [78].
B. Types of Blockchain
There exist different types of blockchain and many times
the clear distinction between them is missing. Figure 5 shows
different types of blockchain and the classification is based
on (i) who is allowed to read, write and commit transactions
in blockchain (i.e., permission configuration) [77], and (ii) on
10
Blockchain
Public
Blockchain
Private
Blockchain
Public
Permissionless
Blockchain
Public
Permissioned
Blockchain
Private
Permissionless
Blockchain
Private
Permissioned
Blockchain
Who can perform read operations?
Hosting is done on what type of servers?
Public
Permissionless
Blockchain
Public
Blockchain
Public
Permissionless
Blockchain
Who can perform write and commit?
Open Type Closed Type
Fig. 5. Types of Blockchain [77], [79]
what type of servers hosting is done [79]. The read permission
allows a node to access and see all the past transactions, and
the write permission enables nodes to create and broadcast a
transaction to all the other nodes in the blockchain network.
The commit permission empowers a node to update the
distributed ledger [77]. Fundamentally, there are four different
types of blockchain: (i) public, (ii) private, (iii) permissionless
and (iv) permissioned blockchain. If a blockchain permits
any node to acquire read permission by default, and public
servers are used for its hosting then it is considered as public
blockchain. On the contrary, if read permission is restricted
and private hosting is used then such a blockchain is called
as private blockchain. In other words, in public blockchain
anyone can read whereas in private blockchain only the set
of vetted nodes can read. Next, a blockchain is said to be
permissionless, if all the nodes with read capability can also
write and commit. However, in permissioned blockchain only
the authorized subset of the participating nodes (who can read)
are capable to write and commit.
Based on these four basic types of blockchain, there are
four combinations possible which are shown as the leaf
nodes of the inverted tree structure in the Figure 5. Public
permissionless blockchain are the ones where anyone can join
the blockchain network and perform read and write operations.
Cryptocurrencies like Bitcoin and Ethereum are examples
of such blockchain. Public permissioned blockchain allows
anyone to read but allows only the selected few nodes to
write and commit. For instance, a supply chain ledger that
can be read by customers but updated by only the authorized
nodes under the control of company [79] or a blockchain-based
voting system. Private permissionless blockchain is formed
by only the set of restricted nodes which can perform read,
write and commit operations. Such a type of blockchain is also
called a consortium or federated blockchain. Finally, private
permissioned blockchain enable all the nodes in the set of
approved nodes to carry out read operation, however, the write
and commit operations are exclusively performed by network
operators (i.e., a subset of a set of approved nodes) [77].
C. Smart Contract
Yet another important concept that has extended the capabil-
ity of blockchain is smart contract. The idea of smart contract
existed much before the birth of blockchain technology. It
was first introduced by Szabo in 1994 [80]. It can be simply
defined as a computer program that encodes all the terms and
conditions of an agreement between participating entities and
runs on top of blockchain [81]. Any node in the blockchain
network is capable of executing a smart contract either when
it is called by initiating a transaction or when certain prede-
fined conditions are met. Moreover, a smart contract can be
established between untrusted and anonymous entities in the
blockchain ecosystem without the need of a third party [82].
As and when the pre-defined encoded conditions are reached
the corresponding smart contract gets self-executed thereby
empowering automation. It is worth noting that once a smart
contract is deployed on the blockchain, it cannot be stopped
by any entity within the system or outside the system [81].
D. Salient Features of Blockchain
This section briefly discusses salient features of blockchain
technology. They are as follows:
•Decentralization: Unlike, conventional centralized tech-
nologies, blockchain technology offers decentralized
modus operandi. This implies there is no central authority
that owns and controls a given system completely. Rather,
the system is collectively operated by a dynamic set of
nodes (or miners) such that any node can create new
block comprising a set of transactions. Thus, blockchain
decentralizes the decision-making and control of the
entire system.
•Immutability: Once any transaction or data is stored
on the blockchain in general, there is no way that it
can be tampered with or altered. This is due to the
11
distributed digital ledger, use of cryptographic techniques,
and consensus-based update procedure. Thus, it is impor-
tant to note that immutability also implies irrevocability
and non-deletion of content from the blockchain infras-
tructure.
•Transparency with Pseudonymity: Transparency im-
plies any node in the blockchain network has access
to read any content present in the digital ledger. The
level of transparency is highest for public permission-
less blockchain and is minimum in private permissioned
blockchain. Further, nodes in the P2P blockchain network
can just see transactions happening between different
digital addresses (account IDs), however, the information
about which ID belongs to whom (i.e., an individual
or an organization) is absent. Thus, blockchain allows
transparency with pseudonymity.
•Fast Processing and Lower Cost: Conventional (logi-
cally centralized) systems involve multiple intermediaries
and/or trusted third parties. For the overall processing of a
transaction, each of these intermediaries performs its set
of dedicated tasks which incur some processing delay.
Moreover, each intermediary charges some processing
fee for the tasks performed. All these intermediaries
collectively increase the total delay and inflate the overall
cost to process a transaction. Thanks to the decentralized
and disintermediated blockchain-based system, users can
perform transactions directly at peep level without involv-
ing third parties or intermediaries. Any one node or miner
in blockchain-based system can process a new transaction
and this update gets registered in the distributed ledger.
This results in fast processing and a reduction in the
overall cost per transaction as compared to conventional
centralized system. For instance, processing of interna-
tional banking transaction using Society of Worldwide In-
terbank Financial Telecommunication (SWIFT) involves
many intermediary banks which may take days to com-
plete and charge high transaction cost [83]. However,
blockchain-based system can process transaction fast and
at low cost [83], [84].
•Consensus-based Decision Making: To add new content
or to update the current blockchain, consensus needs
to be established among the majority of the nodes in
the blockchain network. Thus, blockchain dethrones the
monopoly and embraces democracy in the system. The
algorithm required to establish the overall agreement in
blockchain infrastructure is called a consensus algorithm.
A variety of consensus algorithms are available for exam-
ple Proof-of-Work (PoW), Proof-of-Stake (PoS), Practical
Byzantine Faulty Tolerance (PBFT), Delegated Proof-of-
State (DPoS), Proof-of-Burn (PoB), and Proof-of-Activity
(PoA). Based on the suitability and a given use case, one
must be used.
•Automation Driven by Smart Contracts: Smart con-
tract enhances the capabilities of blockchain technol-
ogy and have been found to be versatile. In particular,
smart contract helps in exercising tight access control
and automating blockchainized systems. At any point
in time, when the predefined conditions embedded in
a smart contract are met, the smart contract gets self-
executed and performs the required tasks without any
human interventions. This results in achieving automation
among multiple untrusting stakeholders in a system.
IV. BLOCKCHAIN FOR 6G T RENDS AND REQUIREMENTS -
AHI GH -LE VE L VIEW
This section provides a high-level view of the use of
blockchain for 6G trends and requirements which were dis-
cussed in Section II.
Blockchain has significantly outgrown its inceptive use
in cryptocurrencies like in Bitcoin. It is rapidly emerging
as a promising technology in other sectors such as supply
chain management, healthcare, smart manufacturing, educa-
tion, and other businesses and trades [85], [86]. It holds
immense potential to transform the way peer transactions, log
management, record-keeping, decentralized negotiation, trade
agreements, audits and compliance, dispute settlements, access
management, and secure automation (via digital contracts), are
carried out.
Continuing the fundamental trend we have witnessed with
5G, it is evident that 6G is going to entail increasingly
softwarized, virtualized, intelligent, and programmable sys-
tems [15], [33]. Nevertheless, it is interesting to note the
following. On the one hand, concepts like softwarization,
virtualization, and programmability of the next-generation
mobile networks would lead to enormous advantages such
as agile and open network management and orchestration
(MANO), multi and micro services, on-demand creation of
virtual networks, and multi-tenancy. On the other hand, these
concepts tend to exacerbate the issues like security vulner-
abilities, privacy leakage, unauthorized access to user data,
dispute-prone soft spectrum sharing, fake or corrupted soft-
ware network functions and control APIs, illegitimate resource
utilization, and inability to provide differential security for
differentiated services [87]. Blockchain is entrusted to play
an alleviating and central role in providing a feasible solution
to these issues. For instance, 6G networks may witness the
availability of open-source software for implementing various
network functions at core, transport or access levels [10]. In
such an open environment, blockchain can ensure the correct
functioning, versioning, integrity, and overall security and trust
management for the software available to be deployed. In
essence, blockchain can be leveraged to improve and support
the technical aspects of 6G mobile networks as well as uplift
the applications and use cases envisioned with the realization
of 6G.
A. Blockchain for 6G Trends
The blockchain and smart contract will play a vital role
in 6G trends as well. Here we discuss the impact and added
benefit of blockchain on the the 6G driving trends mentioned
in Section II-A.
•Massive Availability of Small Data: Blockchain can be
used to eliminate the data silos and enable the trusted
data sharing between unknown parties. Smart contracts
can automate such transactions.
12
1) Accelerated Data Change
2) Distributed Trust
3) Efficient resource sharing
4) Interoperatbility
5) Data integrity and accountability
Role of Blockchain on 6G Trends
1) Distributed trust
2) Automation via smart contracts
3) Improved Interoperability
4) Improved security and privacy
1) Improved efficiency and
control over energy sources
2) New communication
opportunities for devices
3) Cost reduction
1) Improved efficiency and
control over energy sources
2) New communication
opportunities for devices
3) Accelerated Data Change
4) Distributed Trust
1) Scalability via automation
2) Lower Costs
3) Improved Security
4) A More Efficient Supply
Chain
1) Distributed Trust
2) Accelerated Data Change
3) Payment handling
4) Eliminate data silos
5) Data integrity and
accountability
1) Improved Privacy
2) Personal Data Management
3) Enable digital services
4) Digital Currency and
Smart Contracts
Massive Availability
of Small Data
Increasing Elderly
Population
1) Improved Security and Privacy
2) Personal Data Management
3) Distributed Trust
4) Automation
1) Automated Spectrum
Management
2) Fraud detection
3) Spectrum sharing market
place
Expansion of IoTs Gadget-Free
Communication
Availability of Self
Sustain Networks Zero Energy IoT
Emergence of New
Technologies
Convergence of
Communication, Sensing,
Control, Localization and
Computing
More Bits, Spectrum
and Reliability
Fig. 6. Importance of blockchain for 2030’s world 6G driving trends
•Availability of Self-Sustained Networks: The automa-
tion and management via smart contracts can reduce
the extra overhead on network management and or-
chestration. Especially, decentralized access control and
authentication will be used to fully enable energy-efficient
communications.
•Convergence of Communication, Sensing, Control,
Localization, and Computing: The development of
wireless technologies and semiconductor technologies
will lead to more advanced devices with different capa-
bilities. One device can support communication, sensing,
control, localization, and computing. This will lead these
devices to interact with multiple stakeholders simultane-
ously. For instance, sensing information can be shared
with MNOs and spectrum regulatory bodies [88]. Due to
the convergence, not only the collected raw data but also
computed data models (e.g., in the Federated Leading
(FL) use case [89]) can be shared with other stakehold-
ers. In such cases, Blockchain can be used to establish
distributed trust between different stakeholders, protect
the integrity of shared data and automate the process
via smart contacts which encourages the realization of
convergence.
•Expansion of IoT/Zero Energy IoT: Blockchain and
smart contracts can automate a variety of IoT-related tasks
such as authentication, data management, payment han-
dling, and agreement management to support scalability.
Such automation will lead to a reduction in operational
costs. In addition, extra blockchain-based security and
privacy mechanisms can be deployed to protect the IoT
ecosystem and its stakeholders.
•More Bits, Spectrum and Reliability: Blockchain with
clearly-defined smart contracts can alleviate the spectrum
shortcomings against extreme capacity/rates by sharing
spectrum in a transparent, agile (paperless), and trust-
worthy manner. In other words, it can enable on-demand
spectrum via secure and auditable transactions.
•Gadget-free Communication: Blockchain can play a
vital role in ensuring the required level of security and
privacy. Especially, blockchain-based services can be
deployed for the establishment of ad-hoc communica-
tion with different stakeholders in gadget-free environ-
ments. Moreover, the trustworthy sharing of user data
between different stakeholders can also be enabled via
blockchains.
•Increasing Elderly Population: The increasing elderly
population will raise different demands, such as high
demand for health services, the need for more prolonged
government services (i.e., welfare, pension), and user-
friendly and affordable shopping options (e.g., grocery
delivery, food delivery). To tackle these requirements,
several technological solutions are developed and also
proposed. E.g., the use of e-health services will reduce the
cost and stress on existing health services. E-government
can offer faster and more scalable services than exist-
ing legacy government service models. UAVs can be
used to deliver food and groceries. However, these new
technological solutions will face deployment challenges
such as trust establishment, automation support, need
for privacy protection, lack of scalability, etc. To tackle
these issues, blockchain with smart contracts can be
used as a viable solution in many application domains
including healthcare [90], e-governance [91], transport
[92], and multimedia [93]. In such domains, blockchain
and smart contracts can enable automation, reduce the
cost of operation, support scalability, and provide extra
13
TABLE IV
ROL E OF BLO CK CH AIN F OR T O ACH IEV E 6G R EQUIREMENTS
Important of Blockchain Features
Expected
Technical 6G
Requirements
Transparency
Decentralization
Non-Repudiation
Psudonymity
Immutability
Smart Contracts
Trust-building
The Role of Blockchain Key Challenging Points
Further enhanced
Mobile Broadband
(FeMBB)
L H L L L H H
•Use smart contracts to enable the automation
•Support to enable edge computing based services
•Reduction of computational overhead of
blockchain for resource management
•Need of lightweight data sharing tech-
niques for blockchainized systems
Ultra massive
Machine Type
Communication
(umMTC)
M H H M M H H
•Use smart contracts to enable automation and mar-
ket places
•Improve the scalability via enabling distributed con-
trol, universal identity management and automatic
authentication
•Improve the security and privacy in IoT data man-
agement
•Enable the trust between devices
•Development of low-latency blockchain
designs for delay-sensitive applications
•Synchronization/federation of different
blockchain-based network segments for
heterogeneous network architectures.
Enhanced
Ultra-Reliable,
Low-Latency
Communication
(ERLLC/eURLLC)
M H M L L H H
•Use smart contracts to enable the automation
•Support to enable edge computing based services
•Improve the scalability via enabling distributed con-
trol and automatic authentication
•Network scalability and speed of consen-
sus finality for low-complexity consensus
mechanisms
•Management of blockchains for separate
verticals for latency and performance pro-
tection
Extremely
Low-Power
Communications
(ELPC)
L M L L L M L
•Use of private permissioned blockchain for enabling
low-powered devices to exchange data with en-
hanced security
•Improve the scalability via enabling distributed con-
trol
•Need to investigate the energy impact
characterization of blockchain in 6G net-
works
•Requirement of lightweight consensus al-
gorithms
Long Distance
High-Mobility
Communications
(LDHMC)
M H M L M H H
•Support to intermittent session connectivity
•Use smart contracts to enable the automation
•Automated and dispute-free resource sharing
•Integration of blockchain into RAN man-
agement for infrastructure sharing
•Explore the security implications and im-
pact of using blockchains on OSS/BSS
for monitoring and accounting.
High Spectrum
Efficiency H M H L H H H
•Use smart contracts to enable the automatic spec-
trum sharing and marketplaces
•Automatic fraud detection and stakeholders’ rating
•Dynamic spectrum allocation and dynamic contract
•Optimize the interference management
•Development of standardized APIs for
blockchain-powered decentralized spec-
trum sharing
•Implementation of pricing model to reg-
ulate the sharing of spectrum
High Area Traffic
Capacity L M L L L M L
•Support to enable edge computing based services
•Improve the scalability via enabling distributed con-
trol and smart contracts based automation
•Allocation of resources at the edge (for
blockchain) to ensure productiveness
•Mitigation of interoperability issues be-
tween edge and core
Improved Security M M H L H H H
•Security orchestration and automation via decentral-
ized applications (DApps)
•Improve the scalability via enabling distributed con-
trol
•Improve security of data management and user
authentication
•Support for automatic attack mitigation
•Analysing distributed access control for
data sharing
•Optimization of blockchain-based broker-
age techniques for secure resource man-
agement
•Reduction of blockchain overheads and
ensuring trustworthy data support for se-
cure AI-driven functions
Improved Privacy L M M H M H H
•Support the privacy via localization and removing
centralized authorities
•Improve privacy data management and enable the
user control over their data used in AI/ML algo-
rithms
•Enable the use of privacy-preserving digital identi-
ties
•Investigation on making blockchain oper-
ations privacy compliant
•Formulation of well-defined framework to
evaluate the level of privacy established
by blockchainized 6G
Improved
Reliability M M H L H H H
•Ensure the responsibility and non-repudiation
•Support for automatic attack mitigation and fraud
detection
•Performance rating and service classification
•Optimization of redundancy via
blockchains for reliable resource
management
•Robustness against malfunctioning and/or
malicious blockchain nodes
HHigh Impact MMedium Impact LLow Impact
14
security and privacy.
•Emergence of New Technologies: Blockchain can be
used as supporting technology for most of the novel tech-
nologies such as AI, humanoid robots, new AR devices,
and quantum computing. For instance, blockchain can
be used to eliminate the data positioning attacks on AI
systems.
Figure 6 presents in nutshell the importance of blockchain
for 6G trends. Moreover, the impact of blockchain in 6G trends
will be discussed in detail under 6G technologies (Section V)
and 6G applications (Section VI).
B. Blockchain for 6G Requirements
Table IV delineates the role of blockchain to support 6G
requirements.
•FeMBB: Decentrality, data sharing, and distributed com-
putation features of blockchain along with smart con-
tracts can prove to be instrumental to provide extremely
high data rates. Moreover, service automation can be
enabled with the use of blockchain as a secure and
decentralized service platform. Nevertheless, the design
of lightweight blockchain (in general DLT technology) is
important because of the computationally intensive nature
of blockchain.
•umMTC: Blockchain-based ultra massive sensing appli-
cations, fast data exchange without the need of central
entities, and trust-building can well support the extreme
massive connectivity requirement of 6G. However, the
design of a low-latency blockchain can further enhance
the applicability of blockchain.
•eURLLC: Park et al. [94] have proposed various so-
lutions such as ML-based prediction, non-RF modality
utilization, and co-design of communication and control
for eURLLC. Blockchain can support these solutions.
For instance, blockchain provides numerous benefits like
data and model sharing, trusted decision making, and
decentralized intelligence as presented by Liu et al. [29].
However, how to manage blockchains for different ver-
ticals and how to speed up the consensus finality need
further attention.
•ELPC: Use of private permissioned blockchain [95] or
consortium blockchain [96] turns out to be applicable
for low-energy communications. Deploying blockchain
nodes at the edge of the networks or even at gateways
[97] can enable power-constrained IoE devices to securely
store and process data. Nonetheless, it is essential to
access the impact of energy consumption of blockchain
in 6G networks. Furthermore, computationally inexpen-
sive consensus mechanisms tailored for ELPC are to be
designed.
•LDHMC: 6G networks will offer seamless connec-
tivity independent of 3D location, time, and mobility.
Blockchain can provide secure and trusted connectivity
monitoring and clearing among different network service
providers, especially for roaming cases. Nevertheless, the
overall latency and distributed storage of data from the
subscribers of heterogeneous networks need innovative
solutions. In addition, privacy must be guaranteed for
dispute-free coexistence.
•High Spectrum Efficiency: Blockchain-enabled trustless
and decentralized spectrum management can pave the
way for highly spectrum efficient 6G networks. Xu et
al. [25] proposed a basic blockchain-enabled framework
for decentralized resource management. For harnessing
the full potential, lightweight blockchain is required for
small cells and its integration for RAN management is to
be considered.
V. BLOCKCHAIN FOR 6G TECHNICAL AS PE CT S
This section extensively discusses the use of blockchain to
support and improve various technical aspects of 6G.
A. 3D Networking
6G is destined to break the conventional two-dimensional
(2D) nature of mobile communication systems and emerge
as three-dimensional (3D) mobile networks to provide truly
global coverage [11]. The aim is to extend the presence of
mobile networks in air, space, underground, and sea. Thus,
altitude is considered as the third dimension. Since the an-
tennas installed at terrestrial base stations are optimized for
ground users and cannot support high-elevation angles [98],
flying technologies, such as UAVs, tethered balloons, and Low
Earth Orbit (LEO) satellites have been proposed to contribute
towards the extension of the mobile network ecosystem. In par-
ticular, UAV as Aerial Base Stations (ABSs) is characterized
by flexible mobility, ease of maneuvering, varying capability,
and Line-of-Sight (LoS) communications [98]. UAVs can
provide coverage extension using UAV-to-user, UAV-to-UAV,
UAV-to-base station, and UAV-to-satellite communication in
future communication networks [99]. Thus, UAV ABSs can
provide wide coverage, broadband and reliable wireless con-
nectivity, cost-effective and flexible deployment, and pandemic
and disaster management. In contract to 5G, satellite commu-
nications are envisioned as a key component for 6G systems to
provide global coverage and services including multimedia [1],
[100]
1) Key Challenges: Some of the impediments that exist in
establishing a 3D networking paradigm are as follows:
•Interoperability and data management for heterogeneous
networks in a seamless, trustless, and automated fashion,
turns out to be an important challenge. One way to over-
come this issue would be to use a network of hierarchical
trusted entities. However, such a solution is prone to all the
issues related to a (logically) centralized system.
•Adding altitude as a new dimension will open a new attack
surface since the ABSs are not within the premises of their
operators. Moreover, since attackers can easily get control
of ABSs [101], secure key distribution and revocation are
essential.
•Another challenge is ensuring secure seamless movement
of increasing number of flying connected devices within
different heterogeneous networks.
•In addition, 3D localization, network planning, cell associa-
tion, and spectrum sharing are yet another set of challenges
that arise with the use of UAV ABS [98], [102].
15
2) Role of Blockchain: Blockchain has the required po-
tential to offer secure and decentralized management of inte-
grated heterogeneous mobile networks covering space, air, and
ground [103]. In particular, blockchain and well-defined smart
contracts can facilitate a decentralized solution for distributed
key management, authentication, authorisation, auditability.
and trustless interoperability among heterogeneous networks
(and even among various components of one network). Alladi
et al. [107] reviewed the role of blockchain for UAVs and high-
lighted a wide range of benefits that can be achieved. Some of
them are automated decision making, implementation of new
business models, load balancing, detection of hijacks and data
poisoning attacks, and avoidance of mid-air collisions [107].
To overcome the high latency and storage-intensive na-
ture of blockchain for Space-Air-Ground Integrated Networks
(SAGIN), Sun et al. [103] proposed the use of multiple
blockchains, namely, space chain, air chain, and ground chain.
Space chain is maintained by satellite network and to make
this blockchain lightweight, Byzantine Fault Tolerance (BFT)
consensus is used. The Air chain is maintained by air network
(mostly UAV ABSs) and also by some trusted ground stations.
Since ABSs are resource-constrained, authors used ground
stations to perform computational tasks and ABSs simply acts
like a mobile relay to flying users. Ground chain is main-
tained by mobile networks, ad-hoc networks and WiMAX.
Additionally, for interoperability among three chains, the au-
thors proposed the use of collaborative blockchain using side
chain/relay technology. The authors carried out implementa-
tion using Ethereum. Their results show gains in terms of
reduction in storage requirement, high average utilization, and
reduced failure probability.
Flying Ad-Hoc Networks (FANETs) are considered impor-
tant to realize 3D networking in 6G era by acting as airborne
relays and providing on-demand extension of radio connec-
tivity [108]. For distributed key management in the context
of FANETs, blockchain is a promising technology, neverthe-
less, it incurs computational and storage overheads. Thus, to
overcome the storage and computation issues associated with
the use of blockchain for resource-constrained drones, Tan et
al. [104] used heterogeneous FANETs containing resourceful
drones (as cluster heads) in addition to usual drones. Moreover,
to make use of blockchain lightweight for UAVs, authors
modified the structure of a block as well as a transaction. In
particular, the nonce and target difficulty fields were removed.
Consequently, PoW consensus algorithm is not used. In fact,
a miner election scheme is used which decides a miner who
is given chance to generate the next block. The limitations of
the proposed work are that the cluster heads are assumed to be
honest and deployment of resourceful UAVs as cluster heads
might be costly and at times not feasible for the state-of-art
industrial UAVs.
Shi et al. [105] deals with the issue of centralized man-
agement of data generated in Large-Scale Heterogeneous
Networks (LS-HetNet). The authors put forward blockchain-
based decentralized Authentication, Authorization, and Audit-
ing (AAA) scheme for providing data access in LS-HetNet
such that maintenance of Access Control List (ACL) is not
required. Different phases are used for registration, access
Flying Aerial
Base Stations
Satellite
Communications
Internet
Holographic
Applications
Networked
Gaming
V2X
MEC
Smart
Home
Remote Surgery
V2X
Connected
Vehicles
Smart
Cities
AR/VR/MR/XR
Industrial
Automation
Smart
Agriculture
Operator
Cloud
Healthcare
Smart
Building
Overwater or
Coastal or Sea
Communications
Underwater
Communica-
-tions
Swarm
UAVs
Core
Network
Remote / Rural Areas
Fig. 7. Use of blockchain for improving technical aspects of universal communication system envisioned with 6G
16
provisioning, and revocation of rights previously granted to the
data consumers. To implement the proposed scheme authors
used Ethereum private blockchain and evaluated throughput,
storage overhead, and computation overhead. The results pre-
sented show the feasibility of the proposed scheme, neverthe-
less, rigorous testing on real-life testbeds is required to ensure
efficacy.
In [109], authors put forward a framework that comprises
mobile mining nodes and communicating nodes. The latter
types of nodes are connected via a high-bandwidth backhaul
network and help former types of nodes to communicate min-
ing results. Following this approach, authors in [26] integrated
blockchain with federated learning for 6G edge to deal with
disaster management.
To ensure security, privacy and efficient resource sharing for
Space-Air-Ground-Sea Integrated Network (SAGSIN) in 6G
era, authors in [106] proposed close integration of blockchain,
network slicing and network softwarization. In particu-
lar, blockchain-based network management and blockchain-
enabled brokerage services are presented for SAGSIN. Some
of the important functionalities offered by decentralized
blockchain-based network management of SAGSIN are ID
management, authentication, authorization and firmware up-
date management. Whereas blockchain-enabled brokerage ser-
vice for cross-domain environment offers secure SLA, peer-to-
peer payment settlement, and smart contract based tight access
control.
3) Summary:The use of blockchain for 3D networking
can provide decentralized and secure solutions for data ac-
cessing, offloading, and interoperability. Moreover, the idea of
using multiple blockchains along with hierarchical structure
is highly appealing for 3D networks. Table V provides the
summary of important related works using blockchain for
3D networks. Nevertheless, efforts are required to design
lightweight encryption mechanisms and consensus algorithms
to run blockchain-based solutions on UAVs. In the case of
the use of multiple parallel blockchains, cross-chain security
and isolation among blockchains need to be ensured [103].
Furthermore, efficient ways are needed to perform transaction
prioritization in blockchain, and to handle interoperability
when different networks have their decentralized platforms.
B. Dynamic Spectrum Management (DSM)
Radio spectrum is a scarce and indispensable resource for
mobile communication; thus, its overall management (alloca-
tion, sensing, and sharing) must be carried out efficiently in
6G networks. The traditional way of static spectrum allocation
using Fixed Spectrum Access (FSA) policy by telecommu-
nication regulatory bodies though ensures legitimate use of
the spectrum but results in under-utilization of the allocated
spectrum [110]. In recent years, various Dynamic Spectrum
Management (DSM) mechanisms have emerged, such as Dy-
namic Spectrum Access (DSA), Licensed Shared Spectrum
(LSA), and Spectrum Access System (SAS) [111]. In general,
the DSM system comprises two types of users: primary user
and secondary user. The primary user (aka incumbent user)
is an authorized entity with the exclusive right over the
allocated spectrum; however, it might not be able to utilize
the spectrum completely all the time. The secondary user
is the one who gets access to the unused spectrum shared
by the primary user. DSA allows the secondary user devices
to assess the radio spectrum environment continually and
automatically adjust operating frequencies to accommodate
changing capacity/interference conditions [112]. However, the
interference-free access and QoS is not ensured in DSA [113].
In LSA, the telecom regulatory body oversees the sharing
agreement to overcome this issue [114]. In other words, a
secondary user must get an LSA license from the regulatory
body to access the spectrum primary user (or the incumbent)
is ready to share. MNOs or MVNOs are usually the secondary
users. The requirement for DSM becomes even more critical
in 6G era since the number of private networks or local
TABLE V
BLOCKCHAIN FOR 3D NETWORKING
Reference Key Contribution Blockchain Platform
and Consensus
Algorithm
Remarks
Sun et al. [103] Highlights the importance of using blockchain for SAGIN in
terms of decentralized control, privacy, data auditing, registration
and authentication. However, to overcome the high latency and
large storage space issues associated with blockchains, authors
proposed an architecture with multiple blockchains; space chain,
air chain, and ground chain.
Blockchain simulator
(Go language), BFT
consensus for space and
air chains, and DPoS or
BFT for ground chain.
Dedicated efforts are required to ensure secu-
rity of cross chain technology. Moreover, dy-
namic sharding or DAG to increase through-
put and use of technique such as zk-SNARK
to improve privacy are proposed.
Tan et al. [104] To remove the dependency on any central authority such as
base station, authors proposed lightweight blockchain-enabled
distributed key management for heterogeneous FANETs. Ratio-
nale is to include cluster heads which are resourceful UAVs in
addition to regular UAVs and modify the structure of block and
transaction.
Miner election scheme
using distributed random
generation (DRG) proto-
col.
The major limitation is that cluster heads are
assumed to be honest. A rouge cluster head
can send fake transactions and may revoke
benign UAVs from the system.
Shi et al. [105] To overcome the issues with the centralized (AAA) management
of LS-HetNet, authors proposed using of blockchain-enabled
decentralized AAA scheme. The approach does not required use
of ACL for exercising access control.
Ethereum private
blockchain
Challenges that still need to be addressed
are enabling secure routing within blockchain
and make blockchain lightweight and secure
at the same time.
Dai et al. [106] Highlights the challenges being faced by the emerging Space-
Air-Ground-Sea Integrated Network (SAGSIN) such as security
and privacy issues as well as difficulty in resource sharing among
heterogeneous networks. By integrating blockchain, network slic-
ing and network softwarization, authors proposed frameworks for
network management and brokerage services for SAGSIN.
NA Optimization of large-scale cross-domain
blockchain-based system is an open chal-
lenge to be addressed for maximum bene-
fits. Approaches that can be used for cross-
domain collaboration are game-theory and
machine learning based.
17
operators are expected to increase and coexist with public
networks [115]. The successful emergence of local (micro)
operators calls for dynamic spectrum sharing between MNOs
(or other incumbent users).
1) Key Challenges:
•The traditional (centralized) way of spectrum allocation
and management has numerous challenges. These are high
administrative cost, security vulnerabilities, privacy leakage,
unoptimized spectrum allocation, existence of intermedi-
aries to purchase spectrum, slow process of establishing
spectrum sharing agreement, and difficulty to ensure com-
pliance to SLA transparently.
•Although cognitive radio provides users the ability to ex-
ploit the unused spectrum, however, malicious unlicensed
Secondary Users (SUs), using the spectrum-sensing mecha-
nism, can randomly access the unused spectrum or channels
by the licensed-Primary Users (PUs). Subsequently, they can
launch attacks, such as primary user emulation or Denial
of Service (DoS), affecting the cognitive radio network’s
performance and security [116].
•In the case of shared spectrum, the primary issue with the
private networks is the coexistence, i.e., managing Priority
Access License (PAL) users and General Authorized Access
(GAA) users to ensure how they can coexist by sharing
the spectrum relatively [117]. Since private networks will
continue to exist in 6G, designing a dedicated Spectrum
Access System (SAS) will be crucial and challenging at the
same time.
2) Role of Blockchain: Blockchain turns out to be a highly
promising technology for dynamic spectrum allocation, shar-
ing, accessing, and overall management, including auctioning
and payment settlement. In particular, Federal Communica-
tions Commission (FCC) has already identified the potential
of blockchain for efficient management of spectrum [120].
Specifically, blockchain has immense potential to improve the
localized visibility in spectrum usage and ease of auditability
of overall activities for effective implementation of spectrum
sharing rules [125].
In contrast with the traditional exclusive frequency alloca-
tions, spectrum sharing by definition involves multiple entities
with shared access rights to use the spectrum. Here, the users
exchange spectrum usage rights to fulfill their needs [126]. In
this regard, blockchain can be used to set-up a trustless, de-
centralized and open spectrum trading platforms. Nevertheless,
blockchain-empowered open trading of spectrum resources
may lead to privacy issues like revealing trading patterns
or leakage of bids made in auction-based spectrum sharing.
Various privacy-protection mechanisms based on blockchain
and smart contracts can be used to protect the trading entities
from such privacy threats. In this line of approach, Tu et al.
[118] presented a double-auction scheme, which is deployed
as a smart contract in a blockchain platform. To preserve the
privacy of users, differential privacy, in addition to asymmetric
encryption, is used during the bidding process. Furthermore,
the problem of determining a winner in the double auc-
tion scheme, is formulated as Integer Linear Programming
(ILP). With a similar aim to overcome the privacy risks plus
the issues like administrative overheads and single-point-of-
failure associated with traditional Citizens Broadband Radio
Service (CBRS), Zhang et al. [119] proposed a distributed
CBRS model using blockchain. CBRS, originally proposed
by Federal Communications Commission (FCC) is regarded
as a potential candidate to meet the high spectral efficiency
requirement for 6G. Authors, in particular, put forward Proof-
of-Strategy (PoS) as a new consensus algorithm that is not only
lightweight but also integrates with the spectrum allocation
process, i.e., the system reaches the consensus by evaluating
the spectrum allocation strategy. Moreover, the use of ring
signature technique protects privacy by ensuring unlinkability
between users’ real-world identities and their pseudonyms.
Similarly, Hu et al. [120] posited two-level hierarchical
blockchain architecture powered by AI to manage spectrum
resources effectively. In particular, authors manifest the use of
blockchain to offer improved functionalities such as resource
advertisement, spectrum regulation, a record of spectrum
usage, and financial settlement. AI is suggested to provide
usage pattern recognition using deep learning and intelligent
decision-making using deep reinforcement learning. Moreover,
the use of hierarchical blockchain reduces administrative costs,
decreases computational and storage overheads, and mini-
mizes the complexity of consensus algorithms. Nonetheless,
blockchain overheads and techniques to acquire the training
data for AI models with complete privacy compliance are still
challenging.
Furthermore, blockchain can enable guarantee SLA and
dispute-free fast financial agreements for quasi-real time spec-
trum sharing (i) between different MNOs, and (ii) between
MNOs and micro/local operators [127]. For instance, Khan
et al. [121] leveraged blockchain to carry out fair trading of
spectrum in the future Secondary Spectrum Market (SSM) by
eliminating the possible economic malpractices. In particular,
the authors proposed tokenization of spectrum in form of a
new virtual coin named ‘Spectrum dollar’. Thus, their propo-
sition allows disintermediation of financial (central) exchanges
and faster financial settlement. Moreover, the authors used the
floor-and-trade rule to tune the price of a spectrum dollar
to maximize the profit, minimize the loss, and ensure loss-
free trading. Nevertheless, building confidence and onboarding
MNOs and local operators to such decentralized solutions with
spectrum tokenization will be challenging.
Blockchain has been shown to assist the sharing of spectrum
by Human-to-Human (H2H) users with mobile networks to
cater to the massive connectivity needs for M2M commu-
nications. Zhou et al. [122] proposed a blockchain-enabled
framework that (i) preserves privacy in terms of spectrum
sharing cost announced by H2H users, which acts like pri-
mary users and share their spectrum, (ii) facilitates optimized
incentives to H2H users by employing contract-theory, and
(iii) optimizes the allocation of the shared spectrum (by H2H
users) to M2M devices by developing a matching solution. In
general, such a technique can be helpful in dynamic spectrum
management in future convergence of heterogeneous networks
towards 3D networks. Nevertheless, the scenario involving
multiple services and multiple base stations still needs to be
studied, as stated in their work.
In context of MNOs augmented with micro/local operators,
18
TABLE VI
BLOCKCHAIN FOR DYNA MI C SPEC TRU M SHARING (DSM)
Reference Key Contribution Experimental
Setup
Parameters Evaluated Remarks
[118] Considering the centralized dynamic spectrum sharing attack
prone and non-transparent, authors proposed blockchain-enabled
privacy-protected double auction mechanism for decentralized
and auditable dynamic spectrum sharing.
Truffle framework
along with IPFS
were used to
develop a DApp
Spectrum provider’s rev-
enue and social welfare
(difference of spectrum
demanders’ utility and
providers’ utility)
The task of determining the winner
of double auction mechanism is
formulated as integer linear pro-
gramming and solved using Hun-
garian algorithm.
[119] To overcome the high administration cost and the privacy issues
faced by the traditional CBRS, authors leveraged blockchain to
propose distributed CBRS. Furthermore, ring signature is used to
ensure users’ privacy, and proof-of-strategy is proposed as a new
lightweight consensus algorithm.
Simulations using
MATLAB platform
Failure rate of system,
recognition rate (of both
authentic users and mali-
cious users), and system
utility were evaluated
Genetic algorithm is used to solve
the consensus puzzle which is a
class of binary integer program-
ming.
[120] To improve the resource utilization in 6G networks, authors
presented collaborative blockchain and AI for dynamic resource
sharing. In particular, blockchain is used for achieving security,
automation, regulation, and payment settlement, whereas, AI
is used to attain improved pattern recognition and intelligent
decision making.
Simulation based
setup is used and
traffic is modelled
using Poisson
process
Profit ratio and through-
put per licensed time slot
are evaluated
Two-tier blockchain structure is
used - local blockchain per area
(comprises of mobile devices and
base station of that area) and global
blockchain (comprises of all the
base stations).
[121] To address the issue of low utilization efficiency of radio
spectrum, authors proposed blockchain-based automated pricing
model for secondary spectrum market trades among Primary
Licensed Operators (PLOs).
Simulation based
experimental setup
is used
Total revenue of PLOs,
floor values and sensi-
tivity analysis are per-
formed
A new blockchain token named as
spectrum dollar is used as incentive
for spectrum trades in secondary
markets.
[122] To enable secure, privacy protected, and incentivized sharing of
underutilized spectrum by H2H users for M2M communications,
authors proposed blockchain based two-stage framework. In the
first stage, H2H enters into contract with base station to share
spectrum, and in second stage this shared spectrum is shared
with M2M devices.
Simulations based
experiments are
performed
Amount of shared spec-
trum resources and util-
ity of primary and sec-
ondary users are evalu-
ated
Contract theory is utilized to re-
solve the incentive optimization
problem under information asym-
metry.
[123] To meet various challenges & functionalities required by increas-
ing private local operators, authors put forward Blockchain as
a Service (BaaS) platform. In particular, various functionalities
such as subscription management for service registration, reputa-
tion management for service quality, fraud prevention for roaming
instances, and data management are enabled in a decentralized
and secure manner.
Simulation based
experiments using
MATLAB and
implementation
using Ethereum test
network Rinkeby
are done
Roaming cost, service
charge, error rate, ex-
ecution and transaction
costs, and latency are
evaluated.
The structures used for various
smart contracts used for DApp are
given in the paper.
[124] To effectively realize micro-operator based small cell deploy-
ments, authors presented blockchain and SDN integrated archi-
tecture where the complex service level agreements (SLAs) are
coded as smart contracts. These smart contracts run on blockchain
layer which logically sits on top of SDN layer.
Ethereum private
blockchain with
PoW consensus
algorithm and
simulation module.
Received signal strength,
network throughput and
transaction scalability
are evaluated.
Cost savings, and increase in net-
work coverage with guarantee QoS
are the main advantages of de-
ploying micro-operator based small
cell.
blockchain as a service has been proposed to automate the
secure management of spectrum between MNOs and local
operators. Such a service can provide: (i) selection of spectrum
owners (i.e. MNOs acting as primary user), (ii) open auction
in secondary spectrum market, (iii) direct P2P payment for
spectrum sharing, and dynamic creation of agreement using
smart contracts [123]. With similar intent, Okon et al. [124]
implemented a blockchain-based mechanism for spectrum
sharing and SLA compliance in a multi-operator scenario
characterized by small cell deployment by micro-operator. The
authors implemented blockchain network as an overlay on
SDN infrastructure.
3) Summary:In nutshell, the broad roles of blockchain
for 6G spectrum management are (i) decentralized, open and
privacy-protected platform for intelligent spectrum trading,
(ii) dispute-free and fast setting-up of agreements, (iii) tok-
enization of spectrum and P2P fast payments, and (iv) ease
of monitoring and auditing to ensure SLA compliance while
sharing spectrum. In particular, blockchain can be used as a se-
cure and decentralized database for spectrum management that
can record all the activities related to spectrum management.
Though there are significant advantages in using blockchain
for dynamic spectrum management, however, deployment of
blockchain network within the premises of cognitive radio net-
work is challenging keeping in mind the resource-constrained
mobile users [110]. Other practical challenging task will be the
onboarding MNOs and local operators to a blockchain-based
open platform which has no central authority.
C. Security
Security is an all-time important property in telecommuni-
cation and networking. Starting from no security mechanism
and hard handovers in 1G, authentication, anonymity, and
encryption-based security were introduced in 2G [5]. In 3G,
security features of 2G were enhanced by introducing Authen-
tication and Key Agreement (AKA), two-way authentication,
and 3GPP’s air-interface security and network authentication
by users [7]. With 4G Enhanced Packet System-AKA (EPS-
AKA), mutual authentication, trust mechanism, and handover
key management were introduced. 5G incorporated many ad-
vanced security features like better mutual authentication capa-
bilities, Subscription Concealed Identifier (SUCI), Extensible
Authentication Protocol-AKA (EAP-AKA) [128], and 5G-
AKA, Elliptic Curve Integrated Encryption Scheme (ECIES)
based identification mechanism [129], [130]. In future 6G
networks, many security challenges may encounter due to
extremely large network of heterogeneous networks, and the
expected extremely higher reliability requirements. In order to
thwart more sophisticated adversaries, advanced and intelligent
security mechanisms will be needed [31], [131], [132].
19
TABLE VII
SUMMARY OF SECURITY ATTACKS AND TENTATIVE MITIGATION TECHNIQUES WITH BLOCKCHAIN
Attack Description Blockchain based Solution
DDoS Attacks An attacker targets the resource consumption or
protocol vulnerability of a single victim node
by using malicious codes installed on several
computers.
Authors in [136] proposes a blockchain-based approach for intra-domain
and inter-domain DDoS mitigation. They use smart contracts to facilitate
collaboration among SDN-based networking domains. The work [137] use
smart contracts for AI-based DDoS detection and mitigation.
Eavesdropping An illegal action of a third party to secretly cap-
ture data being exchanged between both sides of
communication.
[138] adopts the blockchain platform (Ethereum) to decentralize a dynamic
distributed honeypot system and store the port access data by delivering a
private chain.
Scanning attacks Send requests to all ports of a target host,
aiming at exploring the opened ports and further
exploiting associated bug to launch attacks.
In [138], a private blockchain is used for encrypted communication and services
transformation. It mitigates spoofing attacks with changing service IP addresses
due to transformation property.
Spoofing attacks This attack occurs when fake entities can trick
users into sharing information for malicious ac-
tivities.
Use multi-layered blockchain framework for smart mobility data-market to
enforce fair trade with smart contracts. The identity keys will reduce the number
of fake users and node spoofing attack [139], [140].
Man-in-the-Middle This happens during data transmission where
an adversary eavesdrops, intercepts and manip-
ulates the information.
The work [141] uses an ultra-lightweight RFID protocol targeted for integration
in a supply chain management system that utilizes permissioned blockchain
network.
Sybil attack Adversaries create numerous fake identities to
gain a disproportionately large influence.
Trusted transaction mechanism is developed with permissionless tamper-proof
blockchain-based data structure for storing transaction records of agents without
central control [142].
Selfish mining attack When the selfish miners attempt to increase their
rewards by deliberately keeping their blocks
private
Introduce a life-time or an expiry time for the blocks to prevent block
withholding by selfish miners. Author in [143] formulate a set of Markov
chains to capture the state transitions of private and public chains.
Hijacking A network security attack divert traffic of le-
gitimate users and network towards hijacked
addresses.
In [144], a blockchain based distributed prefix authentication protocol is used in
ICN for authenticating mobile users. Each router in the network authenticates
the prefix to verify the ownership before updating and forwarding the state of
the network.
Poisoning attack Attackers intentionally inject false data into the
training pool of ML model.
Replace the central authority by a blockchain system integrated with federated
learning from the the aspect of fog servers [145]. The work [146] employs a
private blockchain to deliver a collaborative deep learning task in IoT.
Privacy attack Attackers intentionally capture personal data of
the users and to impose attacks.
Using digital signatures generated for a group of blockchain participants where
group members remain anonymous [28]. Zero-knowledge arguments and proofs
methods [28] and Coin mixers [147] are some other techniques to protect
privacy.
1) Key Challenges: Following are few security challenges
identified in the envisioned 6G networks.
•Confidentiality and integrity will be challenging since the
future 6G infrastructure may portray enormous threat sur-
faces with wireless connectivity and the massive data vol-
ume generated in the network.
•Uninterrupted service accessibility will be another challenge
because the broader