Paper review on 5 g mobile technology

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NETWORK ARCHITECTURE OF 5G MOBILE TECHNOLOGY
(Paper Review)
Madhunath Yadav (16909)
MECE
Year / Semester – I/II
Nepal College of Information Technology
08-01-2017

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Table of contents
Title Page
A Abstract 3
B Key word 3
1 Introduction 3
2 System Concept on 5G 4
3 The Main features of the 5G Systems 8
4 The Functional Architecture for 5G Networks 12
5 Meeting the goals for 5G – Research Challenges 19
6 Conclusion 22
7 References 22

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Network Architecture of 5G Mobile Technology
Abstract:
5G Technology stands for fifth Generation Mobile technology, currently the term 5G is not officially used. Research
on 5G mobile wireless technologies has been very active in between service providers and users. The proper 5G
standard is due to be finished in 2018, with the first real networks arriving in 2020. The overall requirements of 5G
wireless systems (e.g., in data rate, network capacity, delay), various enabling wireless technologies have been
considered and studied to achieve these performance targets. The paper throws light on network architecture of 5G
technology. In general, many fundamental changes and innovations to re-engineer the overall network architecture
and algorithms in different layers and to exploit new system degrees of freedom would be needed for the future 5G
wireless system. To fulfill 5G rate and capacity requirements including network densification, employment of large-
scale (massive) multiple input multiple output (MIMO), and exploitation of the millimeter wave (mmWave) spectrum
to attain Gigabit communications. In addition, design tools from the computer networking domain including
software defined networking, virtualization, and cloud computing are expected to play important roles in defining
the more flexible, intelligent, and efficient 5G network architecture. It highlights salient features, i.e., flexibility,
accessibility, and cloud-based service offerings, those are going to ensure the futuristic mobile communication
technology as the dominant protocol for global communication. 5G technology going to be a new mobile revolution
in mobile market. 5G technology has extraordinary data capabilities and has ability to tie together unrestricted call
volumes and infinite data broadcast within latest mobile operating system. This forthcoming mobile technology will
support IPv6 and flat IP.
Keywords
5G Technology, Dense networks, HetNets, mmWave, Massive MIMO, C-RAN, RAN2.0, D2D, Software defined
networking (SDN), Virtualization, WWWW, Software-Defined air interface (SDA), Ultra High Definition (UHD), CoMP.
1. Introduction:
During last two decades, there is rapid evolution of cellular communication technologies from the 2G Global System
for Mobile (GSM) to the 4G Long Term Evolution-Advanced (LTE-A) system. The main motivation has been the need
of more bandwidth and lower latency. While throughput is the actual data transfer rate, latency depends largely on
the processing speed of each node data streams traverse through.
This system has to be significantly more efficient in terms of energy, cost, and resource utilization than today’s
systems, more versatile to support a significant diversity of requirements (e.g., payload size, availability, mobility,
and Quality-of-Service (QoS)) and new scenario use cases, and provide better scalability in terms of number of
connected devices, densely deployed access points, spectrum usage, energy, and cost. The technical goals derived
from these main objectives for 5G are:

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As mentioned before challenges and requirements, various breakthroughs and advancements of wireless
technologies at the physical and higher layers as well as system architecture are strongly needed for the future 5G
wireless system.
In particular, waveform design must be rethought for 5G since the current orthogonal frequency multiple access
(OFDM) technique may not be suitable for stringent delay-constrained wireless applications due to its large
transmission time interval. Moreover, OFDM may not be very efficient in terms of communication signaling overhead
to support emerging M2M applications. In addition, novel solutions exploiting new network degrees of freedom
must be sought to fundamentally increase the communication rate and network capacity. Since frequency spectrum
below 6 GHz has been very crowded, exploitation of the millimeter wave (mmWave) frequency deems necessary to
meet the aggressive requirements in terms of network capacity and from Gigabit broadband applications. However,
mmWave spectrum with its unique characteristics including high attenuation, sensitivity to signal blockage, and fast
channel variations requires innovative solutions from different design aspects ranging from communication
algorithms, network protocols to network architecture engineering.
To meet the requirement, air interface in 5G technology should have flexible Air-interface with flexibility and
adaptability. The flexible air interface consists of block and configuration mechanism to support Adaptive
waveforms, adaptive protocol, adaptive channel structure, adaptive coding, and adaptive multiple access.
The key challenge is to meet these goals at a similar cost and energy consumption as today’s networks. From the
point of view of 5G, a complete redesign of the Internet is discarded. Since the current Internet has become so large,
the implementation of new architectural principles is impractical due to the commercial and operational difficulties
it poses
If 5G includes a revolution, it will come from the radio interface design, where some new paradigms under discussion
represent a radical change in the current view we have on mobile networks in addition to some fundamental changes
in the mobile core functionalities, e.g., driven by new concepts of mobility.
2. System concept on 5G
The 5G services will have very different requirements in terms of minimum data rates, latency, battery life, coverage,
data volume, etc. The 5G system concept is highly flexible and configurable in order to adapt to the large variation
in requirements (rate, latency, number of devices) that occur in different scenarios. It is a user-centric 5G system
concept based on multi-RAT (Radio Access Technologies) that provides improved Quality of user Experience (QoE)
and reliability to both consumers and devices/machines.
To address these challenges, new flexible air interfaces, new possible waveforms, and new multiple access schemes,
medium access control (MAC), and radio resource management (RRM) solutions, and signaling protocols must be
investigated to discard the idea that physical layer improvements are already close to their upper limit.
In 5G system there are three generic service and some service enablers.
The three generic service in 5G are: extreme Mobile Broadband (xMBB), ultrareliable MTC (uMTC), and massive
MTC (mMTC).
 xMBB provides increased data rates, but also improved QoE through reliable provisioning of moderate
rates. Larger data rates are requested by high-demand applications, such as augmented reality or remote
presence.
 mMTC provides connectivity for a large number of cost and energy-constrained devices. Sensor and
actuator deployments can be in a wide-area for surveillance and area-covering measurements, but also co-
located with human users, as in body-area networks.
 uMTC addresses the needs for ultra-reliable, time-critical services, e.g., V2X (Vehicle-to
Vehicle/Infrastructure) applications and industrial control applications. Both examples require reliable
communication and V2X additionally require fast discovery and communication establishment.

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The Main service Enablers
The key enablers towards creating a versatile 5G system that can support the three services are:
 Dense and dynamic RAN providing a new generation of dynamic radio access networks (RANs). The term
RAN 2.0 could be also used referring to this flexibility of the RAN.
 The spectrum toolbox contains a set of enablers (tools) to allow 5G systems to operate under different
regulatory and spectrum sharing scenarios.
 Flexible air interface incorporating several radio interface technologies operating as a function of the user
needs.
 Massive MIMO, in which the number of transmit and receive antennas increase over an order of
magnitude.
 New lean signaling/control information is necessary to guarantee latency and reliability, support spectrum
flexibility, allow separation of data and control information, support large variety of devices with very
different capabilities, and ensure energy efficiency.
 Localized contents/traffic flows allow offloading, aggregation, and distribution of real-time and cached
content.
2.1. Dense and dynamic RAN
UDN refers to this new paradigm of wireless communication network, which includes network cooperation and ultra-
dense availability of access points. Wandering and moving
nodes, mounted on a car, bus, or train, can provide connectivity
to users in their proximity and increase data rates by reducing
the radio distance to the nearest access node. D2D
communications will guarantee the ubiquity of high-quality
services and offload the infrastructure transport network. UDNs
present serious challenges in terms of mobility support,
interference management, and operation (cost, maintenance,
and backhaul).
It is clear that new system designs are needed for 5G networks
to tackle the root of the problem, that is, the huge imbalance
between the nature of mobile devices and cell infrastructure.
This leads to the idea of asymmetric user association and the
fact that UL and DL should be treated as independent networks.

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This way, the unity of the cell is broken, and UL and DL are totally decoupled and served by different access points.
This decoupling philosophy is also being proposed in the 3GPP for the splitting of control and user planes (C/ U-
plane). Given this, it is possible to transmit the C-plane, and consequently HO messages, from a stable macro cells
whereas the U-plane is transmitted from the closest small cell.
2.2 The spectrum toolbox
The new spectrum bands must be identified in the International Telecommunication Union-Radio-communication
(ITU-R) Radio Regulations to support the increase of traffic demand. In this direction, the worldwide allocation of a
number of bands to International Mobile Telecommunications (IMT) technologies is on the agenda for the next
World Radio Conference 2015 (WRC-15). Following figure shows Of course, new spectrum bands must be identified
in the International Telecommunication Union-Radio-communication (ITU-R) Radio Regulations to support the
increase of traffic demand. Despite the fact that the current practice of predominantly using dedicated licensed
spectrum will remain the main stream, new regulatory tools and approaches of sharing the spectrum and optimizing
its use must be devised. On the other hand, the coverage of higher frequency bands may be limited, for example, to
hot spots or dense areas. MMC and low latency on the other hand are required in wide area coverage.
Figure Possible candidate bands for IMT under WRC-15 under Agenda item 1.1

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For its special relevance, we need to mention here the use of millimeter wave (mmW) communications (30 to 300
GHz). Although conventionally beyond 6 GHz spectrum has been discarded due to its high attenuation, recent
research points towards its potential use for backhaul, D2D and even cellular communications. Moreover,
semiconductor technologies are getting mature enough to reduce cost and power consumption of wireless
communications in these new bands.
2.3 Air interface
To meet the requirement, air interface in 5G
technology should have flexible Air-interface with
flexibility and adaptability. The flexible air interface
consists of block and configuration mechanism to
support Adaptive waveforms, adaptive protocol,
adaptive channel structure, adaptive coding, and
adaptive multiple access. It uses universal radio to
support ultra-high data rate, the key component of 5G
Air-interface are:
F-OFDM: Flexible-Orthogonal/Filtered- OFDMA and
SCMA: Sparse Code Multiple Access, which reduce latency and bandwidth consuming, like Virtual Reality. For
example three sub band filter is used to create three sub OFDM carrier grouping with spacing, duration and guard
time.
Frequency division duplex (FDD) and time division duplex (TDD) systems are expected to further coexist, while TDD-
only operation is expected to become more widely used in higher frequency bands. Full duplex is under investigation,
but its use will probably be restricted to low-power radio nodes, e.g., for indoor and outdoor small cell applications
(including in-band wireless backhaul). Evolved versions of existing communication systems need to be efficiently
integrated.
2.4 Massive MIMO
In massive MIMO, we see a very large antenna array at each base station and in general an order of magnitude more
antenna elements as compared with conventional systems. Massive MIMO can be used for a more efficient backhaul
wireless link or even for the access link, in which a large number of users are served simultaneously. Here, massive
MIMO is interpreted as multiuser MIMO with lots of base station antennas.
Massive MIMO can increase system capacity by a factor of 10 and, at the same time, increase the energy efficiency
on the order of 100 times. This boost incapacity
comes from the use of aggressive schemes of
spatial multiplexing whereas the improvement
in energy consumption is due to the
concentration of power in very concrete space
regions.
The main concern when the concept of massive
MIMO comes to real deployments relies on the
factor form of an antenna of hundreds of
element. In this sense, the concept of massive
MIMO is intrinsically related to its use in high
frequencies, e.g., in the centimeter wave
(cmW) and mmW bands, which will reduce the
size of each of these elements. Many different configurations for the real antenna arrays can be used, as depicted
in figure below, ranging from distributed antenna systems, to planar and cylindrical arrays.

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Extensive use of beamforming will be an essential tool to improve link budgets. In addition, spatial multiplexing using
massive MIMO techniques at mmW along with small cell geometries seems to be a symbiotic convergence for
throughput boost. The success of these techniques might be threatened by impairments in the transmission and
reception chain, such as hardware limitations and lack of appropriate channel knowledge. This will be a matter of
exhaustive research in the coming years. Another important problem with massive MIMO is pilot contamination.
2.5 New signaling/control information
The control information/signaling needs to be fundamentally
readdressed in 5G systems to accommodate the different
needs of different services. In order to facilitate the spectrum-
flexible multi-layer connectivity for eMBB services, a separation
of control and data plane can be used. One example is mmW
communication, where the control channel can be established
at lower frequencies. Another example is network-controlled
communication of content via D2D connection, offloading the
cellular network. More generally, the user centricity of 5G
systems shown in Figure induces separation of control and data
planes.
MMC, on the other hand, benefits from a closer coupling
between the control and data plane, even integration of the
control and data planes. MMC also requires optimized sleep mode solutions for battery-operated devices and
mobility procedures with a minimum of signaling and measurements.
2.6 Localized contents and traffic flows
In MMC/D2D, the use of concentrators acting as local gateways could allow direct communication among sensors
located in capillary networks without the need to reach the core network gateway. For MMC/D2D, the localized
traffic flows allow low-power access to the network. The network edge nodes can provide aggregation and
information fusion of sensor data reducing the transport load and provide local added information value. Further,
the necessary context information for MMC operations can be stored locally.
For delay-sensitive services, e.g., road safety applications, it is necessary to turnaround the traffic flow and perform
critical computations close to the user to meet the latency constraints of less than 5 ms. Moreover, the concept of
caching could be shifted to the network edges, reaching access nodes or even the own devices that could act as
proxies in case of having the requested content in the memory.
Based on D2D communication, local data sharing zones can be easily set up, allowing real-time and cached content
sharing by a large number of users without overloading the global network. The short distance transmission enables
high-rate links with reduced power consumption, even if D2D is operated on the same carrier as the cellular network.
Another enabler for localized traffic handling is the establishment of local data sharing by means of wireless access
points in dense deployments, which can coordinate the sharing process. For example, the local content interesting
for the target crowd may be stored at nomadic nodes on-a need basis. The use nomadic nodes, which follow the
crowd, allows for operating local data sharing hotspots in an ad-hoc manner.
3. The Main features of the 5G Systems
The future 5G wireless systems will contain three types of features:
 Mature elements of the system concepts transferred from the previous generations. These features will
be carried into the 5G systems, with suitable adaptation. Examples include: wide-area coverage, efficient
mobility support and energy-efficient terminal operation.
 Emerging system concepts. Some of those concepts are already deployed and operational,
but are expected to mature in order to fit the 5G requirements and architecture. Examples include cloud
RAN, offloading through local connections, etc.

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 Novel 5G-specific concepts. These concepts include nomadic cells, ultra-reliable connections for critical
control, D2D for relaying and aggregation of machine-type traffic, massive machine-type communications,
flexibility and configurability across a large range of rate and latency requirements, etc.
By using a system architecture that supports also D2D communication and UDN deployments, 5G foresees a multi-
Radio Access Technologies (RAT) system that efficiently integrates fundamental building blocks as:
 Massive machine communications (MMC) will provide up- and down-scalable connectivity solutions for
tens of billions of network-enabled devices, where scalable connectivity is vital to the future mobile and
wireless communications systems.
 Vehicle to Vehicle, Device and Infrastructure (V2X) and driver assistance services require cooperation
between vehicles and between vehicles and their environment (e.g., between vehicles and vulnerable road
users over smartphones) in order to improve road safety and traffic efficiency in the future. Such V2X
services for MNs require reliable communication links that enable the transmission of data packets with
guaranteed maximum latencies even at high vehicle speeds.
 Ultra-reliable communications (URC) will enable high
degrees of availability. It is required to provide scalable and
cost-efficient solutions for networks supporting services
with extreme requirements on availability and reliability.
Reliable service decomposition provides mechanisms for
graceful degradation of rate and increase of latency,
instead of dropped connections, as the number of users’
increases.
3.1 Dual role of the mobile wireless devices
Traditionally, mobile wireless networks feature two node types:
infrastructure nodes (access
points, base stations) and terminal nodes (mobile devices). There has been a clear, predefined
hierarchy of master nodes (infrastructure) and slave nodes (terminals) that is underlying any
protocol pertaining to the establishment, usage and maintenance
of a wireless link. As the processing /computing capability of the
wireless devices increases, 5G networks will feature mobile
wireless devices that float in the region between pure
infrastructure and pure
terminal nodes. The key enabler is the directD2D communication,
where certain radio network control functions are transferred to
the device. A D2D-equipped device can have a dual role,
illustrated in the figure, either act as an infrastructure node or as
a terminal, such as:
 Vehicle acting as a terminal, but also as an access node
of a nomadic cell.
 D2D relaying for range extension, improved capacity, longer battery life and confinement of the traffic to
the local area instead of using resources over a wide area.
 Caching of popular contents in mobile devices, which puts them later on in a position to act as access
node for wireless distribution of contents.
The dual role of a wireless device parallels the emerging concept of prosumer in smart energy grids, where a user
can act both as a consumer and producer of energy.
3.2 Ultra-reliable links with low latency

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5G systems will have to satisfy requirements, not supported currently, in terms of reliability and availability and
enable applications such as traffic safety, automatic train control systems, industrial automation, and e-health
services. Two examples are illustrated in following figure.
Figure Two example scenarios that require ultrareliable links with low latency.
For example, some traffic safety applications require information packets to be successfully delivered with very high
probability, within a certain deadline. The failure to achieve this can seriously affect the wellbeing of the users relying
on the traffic safety service. Achieving high reliability at all locations and all times would result in an overdesigned
system and air interface that is inefficient in terms of data rate and power consumption. It is therefore necessary to
carefully co-design the application layer and wireless link to guarantee safety while keeping the costs acceptable.
.
In order to support reliable and low-latency (<10ms) connections within a relatively short range,
5G wireless systems will feature network-controlled D2D communication.
3.3 Guaranteed moderate rates and very high peak rates
The feature that is most commonly associated with 5G is the provision of extremely high rates to each user, ranging
in the order of Gbps. However, from the user perspective, reliable provisioning of moderate rates is at least as
important as maximizing the peak rates. The new transmission technologies, such as Massive MIMO, and the concept
of ultra-dense deployments are instrumental for providing robust radio signal and maintain the desired Signal-to-
Interference-and-Noise Ratio (SINR). High reliability means that moderate rates should be sustained when the
wireless network is challenged, such as in crowded scenarios or under high mobility.
For example, in crowded scenarios, the reliable moderate rates means that the system is capable to gracefully
degrade the performance of each user instead of refusing service to some of the users. An important enabler of
reliable moderate rates is the tight integration of multiple RATs, using optimized signaling/control information.
3.4 Wireless resilient to the lack of infrastructure support
The lack of infrastructure support in general occurs due to: (1) user mobility towards places with worsened or
nonexistent network coverage; (2) equipment failure or infrastructure damages due to reasons like natural disasters.
5G systems should integrate the complementary use of network controlled and pure ad-hoc D2D communications
in order to offer minimal connectivity in emergency/disaster scenarios, and to satisfy the availability and reliability
requirements for mission-critical applications (uMTC), such as road safety and public safety, in an efficient
manner.
Network-controlled D2D communication provides a significantly better performance than pure ad-hoc D2D
communication as result of the superior resource allocation and interference management that can be achieved by
the involvement of a central entity (i.e. base station). Nevertheless, critical applications must operate at some degree
along the entire service area (e.g. the road network in the case of road safety applications), and not only in the
presence of network coverage. The use of ad-hoc D2D communication is therefore essential to enable the
communication between devices even in out-of-coverage circumstances. 5G networks are expected to feature mode
selection schemes that manage the switching between different communication modes, such as ad hoc and
network-controlled D2D mode.
The future 5G network shall also work in case of partial network failure caused, for instance, by a natural disaster.
In this manner, the base stations or even the devices can adopt the role of a cluster head to form ad-hoc networks,

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and thus, enable local communication even if the connection to the core network is broken. To this purpose, limited
core network functions could be preconfigured in the radio access network.
3.5 Increased cooperation among operators
5G services will require novel and more complex way of interaction
and collaboration among the operators. Let us consider, as an
example, the new services associated with V2X communication,
supported by network controlled D2D communication. Compared to a
normal cellular operation, D2D requires changes in operating
procedures especially considering communication among devices from
different operators. Only when operators can cooperate more closely,
and the devices or vehicle terminals from different operators can
establish direct communication link among themselves, the D2D based
solution can provide satisfactory performance, as show in the figure.
Situations where increased cooperation between operators is beneficial or even necessary to provide the desired
service level.
3.6 Self-organized network follows the crowd
Self-organizing networks (SON) have been specified and defined in 3GPP featuring self-configuration, self-
optimization, and self-healing functions. However, next-generation networks will show a new level of adoptivity that
even goes beyond SON. One clear instance is the introduction of nomadic nodes, which will provide a very flexible
tool for dynamic network deployment in order to respond to the user demand.
For example, the on-board communications infrastructure deployed in future vehicles may serve for such purposes
while the vehicle is parked since the density of cars is strongly correlated to the density of people i.e. follows the
crowd. Although nomadic nodes are stationary, the inherent uncertainty with regards to their availability resembles
a network that is “moving” or “movable”. Wireless backhaul, either in band or out band, utilizing massive-MIMO in
cmW/mmW and network coding are promising. In this sense, future networks will “follow” the crowd (i.e., end users)
as well as the demands of novel and revolutionary services.
3.7 Localized traffic offloading
Direct D2D communication is the key enabler for seamless and local traffic offloading in 5G networks. Network-
controlled D2D communication offers the opportunity for local management of short-distance communication links,
which allows separating local traffic from the global network. This will not only significantly unburden the load on
the backhaul and core network caused by data transfer and signaling, but also reduce the effort necessary for traffic
management at the central network nodes. Based on D2D communication, local data sharing zones can be easily set
up, allowing real-time and cached content sharing by a large number of users without overloading the global
network. The short distance transmission enables high-rate links with reduced power consumption, even if D2D is
operated on the same carrier as the cellular network.
Another enabler for localized traffic handling is the establishment of local data sharing by means of wireless access
points in dense deployments, which can coordinate the sharing process. For example, the local content interesting
for the target crowd may be stored at nomadic nodes on-a need basis. The use nomadic nodes, which follow the
crowd, allows for operating local data sharing hotspots in an ad-hoc manner.
3.8 Unprecedented spectrum flexibility
Licensed exclusive use of spectrum builds the most important basis for good quality of service for end users basis
for good quality of service for end users and businesses. 3GPP is currently discussing to supplement the licensed
spectrum for LTE with an unlicensed spectrum. However, as we are facing an exponential increase in the amount of
wireless traffic, there is a need for novel approaches to the spectrum use, demanding unprecedented flexibility in
allocating and using the spectrum in order to adapt to the opportunities and demands in space and time. One

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approach is to build a set of tools to address the
expected needs in the expected situations. Figure
shows the possible tools, i.e., technical enablers,
and how they can be combined to address the
right spectrum usage scenarios under the possible
regulatory frameworks.
 Limited spectrum pool.
 Mutual renting.
 Vertical sharing
 Unlicensed horizontal sharing.
3.9 Energy efficiency
The energy consumption in current networks is
dominated by transmission of overhead signals,
such as pilots, when no user data traffic is
transmitted. Improvements in network energy
efficiency can be achieved by e.g., new lean signaling procedures, novel air interface designs, and network node
activation /deactivation. A 5G system will integrate nodes with large and small coverage areas operating in different
frequencies, e.g., macro cells below 6GHz and fixed and/or nomadic nodes in mmWs. This leads to a different split
of the control and user planes. For xMBB it makes sense to split the C and U planes, to have control at a lower
frequency and user traffic at higher frequencies for higher data rates. For other services, e.g. mMTC a C/U plane split
may not be desirable and it will therefore be a challenge to have xMBB and mMTC on the same carrier and hardware.
4. Architecture for 5G Networks
SDN and NFV are two technologies facilitating each other. SDN enables the separation of control planes from
forwarding planes and capability exposure based on centralized control, whereas NFV enables the decoupling of
software functions from hardware and virtualization of network functions, which redefines the cloud-based
architecture for telecom networks
i) SDN and NFV technologies
ii) The latest advancements in CRAN, and
iii) MEC technologies.
The following sections describe these building blocks.
4.1 NFV plus SDN
SDN and NFV are significant technology evolutions that are key to
realizing 5G networks. The primary focus of SDN is to decouple the
control plane from the data plane, allowing operators to simplify
service and networking provisioning. NFV enables the “cloudification”
of Network Functions (NFs), which may be implemented either on
dedicated or commercial-off-the-shelf (COTS) hardware.

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4.2 Cloud Radio Access Network(C-RAN)
The main idea behind Cloud-RAN (CRAN) is to pool the Baseband Units
(BBUs) from multiple base stations into a centralized BBU pool for
statistical multiplexing gain. A minimal set of critical functions remain
at the radio head (RRH, Remote Radio Head), whose main function is
frequency shifting. With CRAN, it is then possible to have a very tight
coordination between cells and to maximize the radio capacity in
bps/MHz/cell. Additionally, by leaving only the RRH on-site with a
compact power supply, CRAN facilitates antenna site engineering and
provides footprint reduction, as well as shorter installation times and
lower rental and energy costs.
4.3 Triple-layer Re-architectures
Re-architecture of network driven by cloud computing and SDN/NFV can be illustrated in three layers:
Network re-architecture: to build up a ―cloud & network converged‖ infrastructure layer.
Network service re-architecture: to construct a ―virtualized and open‖ service function layer.
Operation re-architecture: to compose a ―smartly-operated‖ orchestration layer.
Figure Triple-layer Re-architectures of Future Network Architecture
4.4. Network Re-architecture
Network re-architecture, in combination with cloud computing and SDN technologies, reconstructs legacy telecomm
network infrastructures to a cloud & network converged one. After network re-architecture is done, the new
infrastructure network will focus on enabling the IaaS (telco cloud, IT cloud and Enterprise cloud) capability.
Network Service Re-architecture
Network service re-architecture focuses on implementation of VNFs under the NFV framework, further
deconstruction and convergence of multiple VNFs, one-button deployment and elastic scalability of multiple VNFs
by the management of VNFM, and capability exposure of VNFs. After network re-architecture is done, a NFVI layer
based on NFV architecture will be formed, on which, enabled by service orchestration, a variety of VNFs can be
rapidly and agilely deployed. These VNFs include those operator‘s self-operated services (vEPC, vIMS, vBNG, vCPE
and etc.), which correspond to SaaS capability and the components of PaaS functional component library oriented
to third-parties which correspond to PaaS capability.
Operation Re-architecture

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While network re-architecture and network service re-architecture achieve the transformation of front-end systems
of telecom networks, operation re-architecture focuses on the transformation of back-end operation systems,
enabling their capabilities of operation and management of new virtual networks, seamless integration with the
legacy network, and E2E close-loop automation. The objective of operation re-architecture is to build a smartly
operated architecture based on cloud services.
Network re-architecture and network service re-architecture are the enablers of IaaS, PaaS and SaaS, whereas
operation re-architecture provides operability features such as cloud capabilities ‘presentation, subscription and
billing. After operation re-architecture is done, the service offering model of telecom networks will be based on
cloud services, and Everything as a Service (XaaS) will be put into reality.
Focusing on the triple-layer re-architectures, ZTE develops the ElasticNet solution. ElasticNet means software-
defined networks featuring layered structure, centralized control and unified management, which incorporate
SDN/NFV frameworks, and to be introduced with ideas of cloud computing, big data and openness. They adopt a
triple-layer architecture composed by orchestration layer – MICT-OS, service function layer - Elastic Cloud Service
and infrastructure layer - Elastic Cloud Infrastructure, and to be introduced with multi-tiered DC (Edge-DC, District-
DC and Central-DC) deployment mode, and constitutes the operator‘s target architecture in a form of ―Driven by
dual-engines of SDN/NFV technologies and centralized managed by the MICT-OSTM‖.
4.4 Network re-architecture: creates a "cloud & network converged" infrastructure layer
In the traditional telecom architecture, the network forms the infrastructure. After the introduction of DCs, DCs
and network will constitute together the new infrastructure that is "cloud & network convergent." The cloud &
network converged infrastructure includes two core resources:
 DC: the vDCs powered by SDN, which are the core "points" of the
infrastructure, and bear telco NFV cloud, IT cloud, enterprise
cloud and other cloud services based on IaaS.
 SD-WAN: the SDN-based WANs, which are the core "connection
lines" of the infrastructure, and include SD-OTN (SDON), SD-
IPRAN, SD-PTN, SD-Access, SD-DCI and other scenarios
Elastic DC provides four core capabilities to support the construction of
the operator‘s network.
 Virtualization, which is based on the cloud-based virtualization
and the SDN-based network virtualization.
 Forwarding acceleration ability, which is archived by the software
and hardware acceleration technology.
 Capability of containerization, such as Docker.
 Capability to achieve converged cloud, which provides telco NFV
cloud, IT cloud, enterprise cloud and other cloud services. Virtualization is the base of cloud DCs, high-speed

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forwarding and containerization are enhanced capabilities of cloud DCs, and converged cloud is the
manifestation of cloud DCs.
4.5 “Cloud & Network Converged” SD-WAN re-architects network connections
The future network will adopt cloud DCs as the core of architecture. Cloud and network will be integrated. Cloud
DCs provide containers and resource pools for network service control, on the other hand fast and flexible network
connections make it possible to access massive users and form larger cloud resources pools.
At first, IP access is the basic mode for personal, residential and enterprise users to access data centers. Mobile
access and fixed network access to cloud DCs are both popular for visiting of massive information of cloud DCs. The
operator need to deploy access networks in a flexible and elastic manner to provide fast connections. SDN-based
control becomes a high cost-effectiveness option for cloud access.
Secondly, when network is the basic structure of the cloud interconnection and various geographically separated
clouds are required to be merged into one large cloud, to realize the DCs‘ connections on WAN level will enable the
distribution of a tenant across WAN and the migration of VMs across WAN. The cloud interconnection provides cloud
IaaS network services.
The constructions of cloud DCs bring traffic to cloud nodes and change the traffic model of the traditional backbone
network and the optimization of IP backbone traffic is required at the same time. The synergy of the IP and optical
layers can achieve the globally optimized schedule of traffic at a larger scale and reduce the transmission cost. Finally,
SDN‘s northbound interface provides openness of network capabilities to users and third parties, which makes it
possible to reshape the form of the industry and provide infinite possibilities for network service innovations. On
the other hand, along with the trend of separation of the control planes from the forwarding planes, the forwarding
planes can adopt universal and equipment’s, the control planes can adopt centralized control. Simplified
equipment’s can reduce O&M and procurement costs.
SD-WAN is the typical application of SDN in the transport network area. SD-WAN focuses on the E2E connections
and provisioning of heterogeneous networks by introducing SDN technology and the flexible customization and
scheduling of APP users. Comparing with traditional transport networks, the SD-WAN has following 4 advantages:
 Support E2E connections
 Support centralized network control and optimization
 Support coordination of heterogeneous networks with multiple layer
 Support openness of network capability
Highlights of network re-architecture
The objective of network re-architecture is to create could-network convergent infrastructures. The key highlights
of Network re-architecture are:
 To constitute the target architecture featuring ―cloud & network convergence‖, and to achieve
coordination and unified management of could and network.
 To provide four key capabilities for building the telco cloud, which are virtualization, high-speed forwarding,
containerization and converged cloud.
 To achieve E2E coordination of SDN-based network, with multi-layer and heterogeneous integration &
openness.
4.6. Network service re-architecture: builds a “virtualized and open” service layer
Network service re-architecture focuses on the reconstruction and integration of traditional NEs and their service
capabilities, including the realization of virtualized NEs in different ways (such as componentization, micro-service
reforming and deploying using containers) and virtual network functions’-splitting and enhancement. For example,
for virtualized gateway, the re-architecture focuses on the separation of control planes from user planes (C-U
separation), while for 5G network, it focuses on the resource aggregation of BBUs‘ control planes and the
enhancement of service capability by introducing new forms of NEs, such as MEC

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Based on shared cloud infrastructure, network functions will be loaded as cloudified software featuring
componentization, stateless and C-U separation and they will be provided as VNFaaS (VNF as a Service). On the other
hand, along with the enhancement of operator‘s R&D capability and the maturity of ecology chain, the operators
have demands on creating innovative services by themselves.
Figure Focus Area of Network Service Re-architecture (Box with Red Dash Line)
Both the VNF capability formed by the re-architecture of traditional NE and the new service capability innovated
by operators and their partners are equally important to the operators in the evolution to future network.
The first step of network service re-architecture is to virtualize telecom services based on IaaS. The second step is
to achieve the migration and enhancement from IaaS to PaaS, and to form a shared and componentized PaaS
platform, and based on which, to achieve the light weight design of VNFs.
Virtualizing telecom network services based on IaaS
Along with the deployment of the cloud & network converged ‘infrastructure, soft NEs‘services will be borne by the
new infrastructure, On one hand, the performance of virtualization NEs will be guaranteed by the CPU performance
improvement, the deployment will be more flexible, and the capacity will be more elastic. On the other hand, the
implementation architecture of some NEs will change significantly, such as C-U separation, separation of status
information from network functions, and etc., which will bring additional advantages. NFV (network function
virtualization) will be introduced to multiple layers of telecom network, however the benefits are different from the
virtualization of different NEs. A brief analysis is illustrated as follows:
Figure Analysis for Different NEs at Multi-layers in Telecom Network
Access Layer

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 BBU: Multi-modes co-exist and cooperation, control resource pooling benefit for C-RAN architecture and
caching capability enhanced;
 OLT: Control plane pooling deployed on cloud benefit for OLT Cluster architecture and traffic break out in
the shortest path;
 CPE: Some new functions, such as vFW and etc. will be deployed on enterprise CPE enhanced with
computing, Some functions of tradition CPE will be removed to Edge DC benefit for, central maintain and
expand the new enterprise market besides traditional carrier market
Aggregation/bearer layer
 RNC/BSC: Geographic redundancy, 2G/3G/4G cooperation, resource sharing and dynamic resource
management;
 SeGW/AG/ HeNB GW: Software customization, cost reduction;
 BNG(BRAS/AC)： Central O&M, cost reduction;
 CR/SR/ DWDM： No obvious driver for virtualization.
Core/Service layer
 VAS： Expansion and maintenance cost reduction, resource pooling, data sharing;
 RCS/CDN/IMS： Quick deployment and innovation of new service, service convergence;
 EPC/UDC/CS： Satisfy MBB increasing requirements in a low cost way, reduce legacy equipment
maintenance cost.
Considering custom business increasing speed and TCO saving after the deployment of telecom NEs, and analyzing
the value acquired after introducing new soft network through network re-architecture, we can get the following
value matrix diagram. The conclusion is service re-architecture in VAS and core network will bring in most of the
value. The reason is that NEs in these domains are located in a centralized manner and have less coupling with down-
layer network functions, so their virtualizations are relatively easy. In addition, these NEs have big peak to average
ratios about capacity and high demand about deployment time, so services, based on resource pool re-architecture,
can enjoy the advantage of scalability and rapid deployment. The costs of services will be saved dramatically and the
gains are great.
Figure Value Analysis for Network Service Re-architecture about Legacy NEs
4.7 Flexible network architecture for 5G
The 5G architecture development is driven by three key aspects, namely: flexibility, scalability, and service-oriented
management. All of these three aspects are complementary to each other such that the diverse set of 5G
technologies which aim to fulfill broad range of service requirements can be efficiently supported.
Flexibility is the core aspect to enable dynamic configuration of the necessary network functionalities for the efficient
realization of a target service and use case. Furthermore, the future-proof architecture shall be flexible enough to

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handle diverse requirements of the use cases and services that we foresee today and the ones that may emerge in
the future and cannot be anticipated now.
They have to control and cope with the dynamics of traffic, user behavior, and active nodes involved and need to be
able to differentiate a larger variety of QoS characteristics, such as ultra-low latency traffic, ultra-reliable
communications, and broadcast traffic. SDN, Network Function Virtualization (NFV), and advanced self-organizing
network (SON) technologies will play an important role in the implementation and control of the network
functionalities, in particular, to improve scalability and reliability.
The generic 5G network architecture, as sketched in blow Figure from the topological point of view, must
accommodate a number of technical enablers and communication paradigms while taking into account existing and
emerging evolutionary and revolutionary architectural trends. The network topology will comprise various flavors of
Cloud-RAN (C-RAN), traditional access nodes as well as new virtual access nodes where the fixed-cell concept
disappears in favor of device-centric communications. Traditional access nodes are the ones that we have today with
the hardware and software components existing together, e.g., dedicated hardware implementations of base
stations. The virtual access node is a new notion anticipated for 5G mobile and wireless communications networks,
where the functionalities at an access node will be run by various virtual machines that can be modified or extended
based on a need basis of the services and/or use cases to be supported.
Figure Generic 5G network architecture (high-level topological view).
Moreover, 5G network architecture will also be scenario and use-case specific, e.g., it may be different in areas with
low user density compared to deployments in ultra-dense areas, such as Mega-Cities.
Implementation of radio network and service functions in C-RAN environments will simplify the mapping of
SDN and NFV features (known from core function virtualization in data centers) to the RAN. It also increases flexibility
with respect to integration of decentralized core functions in C-RAN processing units like local mobility management,
local breakouts, and content delivery networks (CDNs) with caching capabilities.
Due to centralized processing and minimum delay among baseband processing units (BBUs), C-RAN environments
allow simplified clustering of cells for joint RRM and interference coordination (including coordinated multipoint
transmission/reception (CoMP)). Dependent on network infrastructure availability of the mobile network operator
and delay limitations set on back-/ fronthaul links b, e.g., by CoMP schemes, C-RANs can be deployed in a distributed
or more centralized way, which differentiate especially in terms of the number of contained BBUs Nevertheless, the
BBU number of a local C-RAN can be also high in case of UDN, e.g., for a stadium scenario.

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Figure Generic 5G network architecture (high-level functional/logical view).
A first consideration of the main functional building blocks to appear in the 5G RAN architecture from the logical
point of view is shown in Figure 9. Flexibility shall enable a dynamic configuration of the necessary network
functionalities in order to fulfill the requirements of a target service. This can necessitate new or tailored
functionalities that will be made available on-demand based on the capabilities, such as processing and memory, of
the network elements. On this basis, the
5. Meeting the Goals for 5G – Research challenges
5.1. 1,000 times higher mobile data volume per area The primary methods to address this goal are to use more
frequency spectrum, to use more network nodes, and to enhance network performance and spectral efficiency.
5.1.1 Use more frequency spectrum Both higher data rates and higher data volume require access to more
frequency spectrum for mobile communications. As stated before, in WRC-15, it is expected that clearly more
spectrum will be released for mobile communications. This new spectrum lies in the frequency range between 300
MHz and 6 GHz. However, for the future 5G system, these new spectrum opportunities will not be sufficient.
Additionally, the release of new spectrum in the mmW bands was postponed to WRC-18.
5.1.2 Use more network nodes
Densification of networks by deploying more nodes is already applied today with femto or pico cells providing local
connectivity for increased capacity in addition to the macro cells in the wide-area. This trend is expected to continue,
where the small cells can make use of higher frequency bands, such as the 3.5 GHz bands or the mmW bands. The
use of TDD with higher frequencies can become more prominent as compared with 3G/LTE today. The different
network layers/cell hierarchies and RATs are to be integrated by means of smarter networks. Dedicated
implementation solutions such as distributed RRUs can be developed for specific deployments such as for providing
coverage of very crowded places, e.g., stadiums and events.
5.1.3 Enhance network performance and spectral efficiency
Enhanced network performance and spectral efficiency are to be achieved by applying more sophisticated protocol
and air interface technologies as compared to LTE-A [58]. The primary air interface technologies in this regard are

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the use of multiple antennas, possibly involving massive antenna constellations, multi-stream transmission such as
spatial multiplexing or non-orthogonal multiple access, and cooperation techniques such as coordinated multi-node
transmission or solutions based on interference alignment.
5.2 10 times to 100 times higher typical user data rate
The primary methods to address this goal are to use spectrum aggregation and more dynamic spectrum access,
usage of higher frequencies up to mmW frequencies and short-range communications.
5.2.1 Spectrum aggregation and more dynamic spectrum access Spectrum aggregation is already defined by 3GPP
LTE-A and enables peak data rates up to about 1 Gbps. This may evolve further to take into account the new bands
released during WRC-15. Aggregation of multiple bands over a wide range of frequencies poses challenges
concerning the cost and efficiency of radio frequency filter and transceiver solutions, in particular for the UEs. Global
research must be conducted to propose new schemes for spectrum opportunity detection and assessment and
spectrum management concept for LSA. Based on the need for spectrum, these technical enablers shall help to
obtain spectrum by negotiating access to it with other entities and also assessing the use of spectrum.
5.2.2 Usage of higher frequencies
Usage of higher frequencies up to mmW frequencies will further increase the achievable data rates to 10 Gbps or
beyond. To compensate for the path loss at such high frequencies, high antenna directivity is required if transmission
range shall be beyond a few meters. Accordingly, flexible air interfaces for mmW frequencies must be developed.
The identification of suitable frequency bands and the characterization of the propagation channel demand new
investigations.
5.2.3 Short-range communications
Finally, reducing the transmission distance, approaching short-range communications, e.g., D2D or UDN, is also an
efficient means to increase user data rate. Indeed, node densification and dynamic RAN (cf. RAN 2.0 described
previously) can allow confining interference to very specific areas of use while reducing the signal attenuation. Both
effects shall boost the signal to interference plus noise ratio (SINR) thus increasing the user data rate by a logarithmic
law.
5.3 10 times to 100 times higher number of connected devices
The primary methods to address this goal are to reduce signaling overhead, to use dynamic profiles of users, and to
implement traffic concentration, in particular for MMC applications.
5.3.1 Reduce signaling overhead
Signaling overhead can be reduced by designing more efficient protocols and by thinning out some protocol layers,
e.g., for the simplification of end-to-end procedures. On the air interface, the signaling for random access, time
adjustment, and/or resource assignment can be reduced, for example, by using contention-based access, waveforms
that are more tolerant to timing mismatch as compared to orthogonal frequency division multiplexing (OFDM), and/
or by resource reservation, making the air interface more flexible and suitable for small payload traffic. For instance,
methods dedicated to contention-based access for massive number of devices without scheduled access and
multiuser detection facilitated by compressive sensing are good candidates to reduce signaling.
5.3.2 Use dynamic profiles of users
NFV technologies can play a role to overcome current limitations of a rigid protocol stack by allowing flexible
configuration of the network functionalities. The future air interface shall support this flexibility by using dynamic
profiles of users, of which entries are configurable to pre-defined use cases. In this sense, some radio functions will
be activated/deactivated on demand depending on the specific needs of the service and the status of the network.
Again, the user-centric paradigm applies, since the network shall adapt its topology and operation mode according
to the needs of each user.
5.3.3 Traffic concentration

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Finally, traffic concentration can be achieved by means of gateways, for example, by linking a capillary MMC network
to a wide area cellular network. In this framework, the RAN might configure one specific device to act as such
concentrator (cluster head) by using D2D communications to collect all data from the surrounding machines. It is
expected that this last hop link should work on a different radio interface to host a large number of mesh devices
with severe energy constraints. For instance, techniques are developed to reduce the amount of traffic in gateway-
based MMC solutions by context-based device grouping and signaling.
5.4 10 times longer battery life for low power MMC devices
The primary methods to address this goal are to improve air interface, procedures, and signaling and to reduce the
distance between the MMC devices and the access node. Techniques to improve the air interface include the use of
sleep modes, energy-efficient modulation, coding and multiple access schemes, for example, use of constrained
modulation techniques such as Gaussian Minimum Shift Keying (GMSK), very robust coding and/or spreading
allowing very low transmission powers, and simplified procedures such as those introduced for the previous goal.
The MMC devices can, in some scenarios, be brought closer to the access node, for example, by gateways connecting
a capillary network to a wide area network or by denser deployment of small cells.
5.5 Times reduced End-to-End (E2E) latency
The primary methods to address this goal are to use more efficient network architectures, more efficient air interface
designs, signaling and procedures, better QoS differentiation, and direct D2D communication.
5.5.1 Efficient network architectures
Low-latency network architectures are concerned with shortening the distances and number of hops between the
user and the content, for example, by distributing some network functions that are centralized today or by applying
local and universal caching as well as local breakouts to external networks like Internet, service provider, or
enterprise networks.
5.5.2 Efficient air interface designs
The air interface may adapt the frame structures in order to reduce the Transmission Time Interval (TTI) and/or
Hybrid Automatic Repeat reQuest (HARQ) round trip times. While this can efficiently be implemented at the higher
frequencies where more bandwidth is available, this can become very inefficient for wide area coverage. Signaling
and procedures can be thinned out, by simplifying their components.
5.5.3 Better QoS differentiation
Better QoS differentiation is important in this context. As the low-latency transmission may become inefficient, it
should only be applied with the services that require such low latencies and should be avoided with delay insensitive
services.
5.5.4 D2D
With cellular-based D2D communication, also called proximity
service (ProSe), user data can be directly transmitted between
terminals without routing via eNodeBs and core network. D2D
communication has a structure quite different from that of a
traditional cellular network
D2D communication helps increase spectral efficiency, enhance user experience, and expand communication
applications.
 Increasing spectral efficiency

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 Enhancing user experience
 Expanding communication applications
Application of D2D on 5G
 Local service.
 Emergency communication.
 IoT enhancement. Figure
D2D based on IoV application.
6. Conclusions
The development of 5G wireless systems is in its infancy and it is difficult to state precisely how the final system
design options will look like. Yet, it is already possible to identify important services, enablers and features that will
be present in, practically, any conceivable solution for a 5G system. The main objective of this paper is to give insights
into the features, required flexibility, and the general architectural approach to the design of a 5G system. A theme
that pervades multiple features is direct D2D communication, as its combination with the cellular network
communication will lead to improvements in reliability and/or spectrum usage. The overall architecture follows the
trend of SDN and NFV, adding functions and procedures specific to wireless mobile communication, such as resource
allocation and mobility. We believe that this paper is shaping the 5G research agenda by setting a useful framework
for innovation and optimization of specific wireless transmission techniques and protocols.
References:
1. EU-FP7 Project METIS (ICT-317669) Deliverable 1.1, April 2013
2. http://netgroup.uniroma2.it/Stefano_Salsano/papers/tett-sf-arch-v35
3. http://eprints.networks.imdea.org/1346/1/CLEEN%20WORKSOP%20NORMA%20Final%20Manuscript
4. http://www.intel.com/content/dam/www/public/us/en/documents/white-papers/5g-a-network-
transformation-imperative
5. https://pdfs.semanticscholar.org/fa15/2676153e3cccacc2a4b9d3e8e7c6d37cd66c