Road to 5G: Introduction and Migration - April 2018 - GSMA

 
Road to 5G: Introduction and Migration - April 2018 - GSMA
Road to 5G:
Introduction
and Migration
April 2018
Road to 5G: Introduction and Migration - April 2018 - GSMA
ROAD TO 5G: INTRODUCTION AND MIGRATION

 About the GSMA                                               Future Networks Programme
 The GSMA represents the interests of mobile operators        The GSMA’s Future Networks is designed to help operators
 worldwide, uniting nearly 800 operators with almost 300      and the wider mobile industry to deliver All-IP networks so
 companies in the broader mobile ecosystem, including         that everyone benefits regardless of where their starting
 handset and device makers, software companies,               point might be on the journey.
 equipment providers and internet companies, as well as
                                                              The programme has three key work-streams focused on:
 organisations in adjacent industry sectors. The GSMA also
                                                              The development and deployment of IP services, The
 produces industry-leading events such as Mobile World
                                                              evolution of the 4G networks in widespread use today, The
 Congress, Mobile World Congress Shanghai, Mobile World
                                                              5G Journey developing the next generation of mobile
 Congress Americas and the Mobile 360 Series of
                                                              technologies and service.
 conferences.
                                                              For more information, please visit the Future Networks
 For more information, please visit the GSMA corporate
                                                              website at: www.gsma.com/futurenetworks
 website at www.gsma.com. Follow the GSMA on Twitter:
 @GSMA.                                                       Document Editor
                                                              Dongwook Kim, 5G Project Manager
                                                              Michele Zarri, Technical Director – Networks

Acknowledgement (5G Introduction Project Members)

 Applied Communication Sciences                              MediaTek Inc.
 ARM Ltd.                                                    Nokia
 AT&T Mobility                                               NTT DOCOMO, Inc.
 Axiata Group Berhad                                         Orange
 China Mobile Limited                                        Qualcomm Incorporated
 China Telecommunications Corporation                        SingTel Mobile Singapore Pte. Ltd.
 China Unicom                                                SK Telecom Co., Ltd.
 Deutsche Telekom AG                                         SoftBank Corp.
 DISH Network Corporation                                    Sprint Corporation
 Ericsson                                                    Syniverse Technologies, Inc
 Guangdong OPPO Mobile Telecommunications Corp.,Ltd.         Telecom Italia SpA
 Huawei Technologies Co Ltd                                  Telefónica S.A.
 iBasis, Inc                                                 Telenor Group
 Intel Corporation                                           Telia Finland Oyj
 KDDI Corporation                                            T-Mobile USA, Inc
 KPN B.V.                                                    Turkcell Iletisim Hizmetleri A.S.
 KT Corporation                                              United States Cellular Corporation
 Kuwait Telecom Company (K.S.C.)                             Videotron Ltd
 LG Electronics Inc                                          Vodafone Roaming Services S.à r.l
 LG Uplus, Corp.                                             ZTE Corporation
Road to 5G: Introduction and Migration - April 2018 - GSMA
ROAD TO 5G: INTRODUCTION AND MIGRATION

Contents
Executive Summary                         5   4.3.4       Impact on device and                 22
1           Introduction                  8               network
1.1         Scope                         9   4.3.5       Impact on voice including            22
                                                          service continuity
1.2         Abbreviations                 9
                                              4.4         NSA Option #3 to NSA                 23
1.3         References                   11
                                                          Option #7 and SA Option
                                                          #5
2           Why 5G?                      12   4.4.1       Description                          23
2.1         The advent of the 5G era     13   4.4.2       Feasibility of the path in           23
2.2         Drivers of 5G                13               meeting 5G use cases
2.3         Expectations on 5G           13   4.4.3       Deployment considerations            23
2.4         Use cases and spectrum       14   4.4.4       Impact on device and                 23
            bands for 5G                                  network
                                              4.4.5       Impact on voice including            24
Part I                                   15               service continuity
3           5G Network Deployment        15   4.5         NSA Option #3 to NSA                 24
            Options                                       Option #3 and SA Option
                                                          #2
3.1         Standalone (SA) and Non-     16
            standalone (NSA)                  4.5.1       Description                          24
3.2         Evolved Packet Core (EPC)    16   4.5.2       Feasibility of the path in           24
            and 5G Core Network (5GC)                     meeting 5G use cases
                                              4.5.3       Deployment considerations            24
4           5G Network Introduction &    18   4.5.4       Impact on device and                 24
            Migration Paths                               network
4.1         General observations and     19   4.5.5       Impact on voice including            25
            assumptions                                   service continuity
4.2         EPS to SA Option #2          19   4.6         NSA Option #3 to NSA                 26
                                                          Option #4 and SA Option
4.2.1       Description                  19
                                                          #2
4.2.2       Feasibility of the path in   19
                                              4.6.1       Description                          26
            meeting 5G use cases
                                              4.6.2       Feasibility of the path in           28
4.2.3       Deployment considerations    19
                                                          meeting 5G use cases
4.2.4       Impact on device and         20
                                              4.6.3       Deployment considerations            26
            network
                                              4.6.4       Impact on device and                 27
4.2.5       Impact on voice including    20
                                                          network
            service continuity
                                              4.6.5       Impact on voice including            27
4.3         EPS to NSA Option #3         21
                                                          service continuity
4.3.1       Description                  21
                                              4.7         Other migration steps                27
4.3.2       Feasibility of the path in   21
            meeting 5G use cases
                                              5           Recommendations for                  28
4.3.3       Deployment considerations    21
                                                          collaborative actions
Road to 5G: Introduction and Migration - April 2018 - GSMA
ROAD TO 5G: INTRODUCTION AND MIGRATION

                                               7.1.2       5GC (5G Core)                42
Part II                                   30   7.2         Comparison of EPC and        44
6           Study of 5G Network           30               5GC
            Introduction Case
6.1         Why 5G?                       31   8           Detailed considerations on   45
6.1.1       5G technology and service     31               5G deployment options
            trial activities                   8.1         Standalone considerations    46
6.1.2       Other business/social         32   8.2         Non-standalone               46
            drivers in the nation                          considerations
6.1.3       Deployment purpose and        33
            spectrum at disposal               9           Impact on voice including    49
6.2         Analysis of 5G migration      34               service continuity
            options                            9.1         Options for operator         50
6.3         Rationale behind migration    35               voice/video
            option                                         communications service in
6.4         Challenges in actual          36               5G
            migration                          9.2         Recommendations for          51
6.5         Lessons learned from          38               voice/video
            migration case study                           communications service in
                                                           5G

Part III                                  40
                                               Annex A                                  52
7           Core network                  40
            considerations                     Other considerations for operators
7.1         Core network solutions        41   A.1         Status Icon related to 5G    53
7.1.1       EPC (Evolved Packet Core)     41
Road to 5G: Introduction and Migration - April 2018 - GSMA
ROAD TO 5G: INTRODUCTION AND MIGRATION

Executive Summary
Unlike previous generations of mobile networks,               cases effectively while supporting global
the fifth generation (5G) technology is expected              interoperability.
to fundamentally transform the role that
telecommunications technology plays in the                    This document therefore analyses the alternatives
society. 5G is also expected to enable further                available for operators intending to introduce a
economic growth and pervasive digitalisation of a             3GPP compliant 5G system migrating from their
hyper-connected society, where not only are all               3GPP 4G network. The structure of the document
people connected to the network whenever                      is as follows: Part I provides an high level
needed, but also many other devices/things                    description of the 5G introduction and subsequent
virtually creating the society with everything                migration along recommendations for
connected (i.e. Internet of Everything). 5G will              collaborative actions while Part II delves into real
therefore enable new use cases such as smart                  operator case study and Part III provides
cities, smart agriculture, logistics and public safety        advanced technology considerations requiring a
agencies. Furthermore, there are a variety of                 reasonably advanced level of understanding of the
spectrum bands available for deployment of 5G,                3GPP system.
which can be sub-divided in three macro
                                                              While 3GPP is defining both a new 5G core
categories: sub-1GHz, 1-6GHz and above 6GHz.
                                                              network (5GC) as well as a new radio access
In addition, 3GPP (3rd Generation Partnership
                                                              technology called 5G “New Radio” (NR), it is
Project) has specified new 5G radio access
                                                              possible to integrate elements of different
technology, 5G enhancements of 4G (fourth
                                                              generations in different configuration with 5G: SA
generation) network, and new 5G core network.
                                                              (standalone) and NSA (non-standalone). SA
The variety of requirements and spectrum needs                scenario uses only one radio access technology
show that there are many options of 5G                        (5G NR or the evolved LTE (Long Term Evolution)
introduction and different spectrum bands will be             radio cells) and the core networks are operated
needed to support all use cases. Operators must               alone. NSA scenario combines NR radio cells and
therefore consider the feasibility of different               LTE radio cells using dual-connectivity to provide
options in meeting their intended initial use cases           radio access and the core network may be either
and interoperability of their choice with other               EPC (Evolved Packet Core) or 5GC (see Table 1
options to ensure their networks deliver the use              for details).

 Table 1: Comparison of 5G radio access and core networks
                                            Advantages                            Disadvantages
                                            • Simple to manage                    • Not able to leverage existing
                   SA                       • Inter-generation handover             LTE deployments if NR is used
 Radio                                        between 4G-5G                         in SA
 access
 network                                                                          • Tight interworking between LTE
                                            • Leverage existing LTE
                   NSA                                                              and NR required
                                              deployments
                                                                                  • May impact end user experience

                                            • Leverage existing EPC
                   EPC                                                            • Cloud support is optional
                                              deployment
 Core
 network                                    • Cloud native
                   5GC                      • Easier to support multiple          • New deployment required
                                              access

                                                                                                                     5
Road to 5G: Introduction and Migration - April 2018 - GSMA
ROAD TO 5G: INTRODUCTION AND MIGRATION

    Figure 1: 4G and 5G Deployment Options

Consequently, five deployment options are                    • NSA Option #3 to NSA Option #3 and SA
available for 5G as depicted in Figure 11. Red                 Option #2
colour denotes NR and 5GC.                                   • NSA Option #3 to NSA Option #4 and SA
                                                               Option #2
     NOTE: for simplicity, the figure does not
     depict control and user plane connection             The analysis of the paths (see Table 2) take four
                                                          perspectives. First, feasibility of use case refers to
As there can be multiple paths to reach the final         the ability of the path in addressing 5G use cases.
target configuration that an operator intends to          Second, deployment considerations consider the
deploy, it is essential to consider migration steps       support for early 5G devices and core network &
that would comprise different paths. This                 radio access network deployment considerations
document analyses the following migration steps           of the migration step (i.e. the core network
that the 5G Introduction project group members            solution adopted as a result of the path and the
believe to be more likely.                                extent of leveraging existing LTE deployment).
                                                          Third, impact on device and network considers
     • EPS (Evolved Packet System) to SA Option
                                                          the impact of the migration step on device and
       #2
     • EPS to NSA Option #3                               network. Finally, impact on voice service including
     • NSA Option #3 to NSA Option #7 and SA              service continuity refers to the ease of voice
       Option #5                                          service provisioning and continuity offered by the
                                                          migration step.

1
  For completeness, the figure also includes “Option 1”
representing today’s 4G deployments

6
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ROAD TO 5G: INTRODUCTION AND MIGRATION

    Table 2: High-level overview of migration step analysis results

          Path              Use Case1            Deployment              Device/Network            Voice

                                                                      • Little impact on     • IMS Voice
                                              • 5G Core benefits        4G                     supported
    EPS to SA#2         • Full 5G use cases   • Needs to retain       • 4G/5G system         • No CS
                                                EPC                     interworking           interworking from
                                                                        required               5GS

                                              • Leverage LTE
                                              • Quick time-to-
                        • Limited support                             • EPC procedures       • Leverage existing
    EPS to NSA#3                                market
                          for 5G use case                             • Impact on 4G           VoLTE service
                                              • No 5G Core
                                                benefits

                                                                                             • IMS Voice
                                                                      • Impact on NR,
                                              • 5G Core benefits                               supported
    NSA#3 to            • Full 5G use cases                             LTE
                                              • Needs to retain                              • No CS
    NSA#7 / SA#5        • Initially limited                           • Impact on IMS
                                                EPC                                            interworking from
                                                                      • 5GC deployment
                                                                                               5GS

                                                                                             • IMS Voice
                                              • 5G Core benefits      • Impact on NR,
                        • Full 5G use cases                                                    supported
    NSA#3 to                                  • Needs to retain         LTE
                        • Initially limited                                                  • No CS
    NSA#3 / SA#2                                EPC                   • Impact on IMS
                        • Core migration                                                       interworking from
                                              • Wide area NR          • 5GC deployment
                                                                                               5GS

                                                                                             • IMS Voice
                                                                      • Impact on NR,
                        • Full 5G use cases   • 5G Core benefits                               supported
    NSA#3 to                                                            LTE
                        • Initially limited   • Needs to retain                              • No CS
    NSA#4 / SA#2                                                      • Impact on IMS
                        • Core migration        EPC                                            interworking from
                                                                      • 5GC deployment
                                                                                               5GS
1
    Limited support for 5G use case denotes focus on enhanced mobile broadband use case
NOTE: CS stands for circuit-switched

The availability of options and migration steps                  • Global profile for the industry to address
indicate that the mobile industry needs to respect                   •    Basic connectivity of devices to a 5G
the need of different operators to follow different                       network (including interoperability
migration strategies with some degree of                                  between 5G and LTE networks)
divergence. Nevertheless, customers and the                          •    IMS (IP Multimedia Subsystem)
wider industry will be able to benefit as a whole if                      services delivered over NR
the following collaborative actions are taken by                     •    Support roaming to/from networks
                                                                          with same/different 5G deployment
operators in order to guarantee service continuity,
                                                                          option
services and network interoperability and to
unlock economies of scale.                                       • Global issue registry and resolution group
                                                                   that receives issues encountered during 5G
                                                                   commercialization and collaboratively
                                                                   resolves the issues.

                                                                                                                   7
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ROAD TO 5G: INTRODUCTION AND MIGRATION

1
1. Introduction

8
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ROAD TO 5G: INTRODUCTION AND MIGRATION

1.1 Scope                                             CSCF        Call Session Control Function
This document analyses the alternatives available     CSFB        Circuit Switched Fallback
for operators intending to introduce a 3GPP           CUPS        Control Plane – User Plane Separation
compliant 5G system migrating from their 3GPP
                                                      E2E         End-to-End
4G network. For each of the options and
                                                      eMBB        enhanced Mobile BroadBand
consequent migration steps, this paper considers
the technical, economic and strategic perspective.    EMM         EPS Mobility Management
The structure of the document is as follows: Part I   eNB         Evolved Node B
provides a high level description of the 5G           EN-DC       E-UTRA-NR Dual Connectivity
introduction and subsequent migration along
                                                      EPC         Evolved Packet Core
recommendations for collaborative actions. Part II
delves into real operator case study of deploying     ePDG        Evolved Packet Data Gateway
5G while Part III outlines advanced technology        EPS         Evolved Packet System
considerations requiring a reasonably advanced        ESM         EPS Session Management
level of understanding of the 3GPP system.
                                                      EU          European Union
It is assumed that the mobile network operator                    Evolved Universal Terrestrial Radio
                                                      E-UTRA
deploying a 5G network is already operating a 4G                  Access
network. This document covers 3GPP mobile                         Evolved Universal Terrestrial Radio
                                                      E-UTRAN
accesses (4G and 5G) only. Non-3GPP accesses                      Access Network
are not covered in this version of the document.      EVS         Enhanced Voice Services

1.2 Abbreviations                                                 Federation Internationale de Football
                                                      FIFA
                                                                  Association
 Term       Description
                                                      gNB         Fifth Generation NodeB
 2G         Second Generation (Mobile Network)
                                                                  Global System for Mobile
 3G         Third Generation (Mobile Network)         GSM
                                                                  Communications
 3GPP       Third Generation Partnership Project
                                                      GW          Gateway
 4G         Fourth Generation (Mobile Network)
                                                      HEVC        High Efficiency Video Coding
 5G         Fifth Generation (Mobile Network)
                                                      HO          Handover
 5GC        5G Core (network)
                                                      HSS         Home Subscriber Server
            Fifth Generation Private Public
 5GPPP                                                IMS         IP Multimedia Subsystem
            Partnership
                                                                  International Mobile
 5GS        Fifth Generation System                   IMT
                                                                  Telecommunications
 AMF        Access & Mobility Management Function
                                                      IOC         International Olympic Committee
 AP         Access Point
                                                      IoT         Internet of Things
 API        Application Programme Interface
                                                      IP          Internet Protocol
 AS         Application Server
                                                      IPTV        Internet Protocol Television
 ASN.1      Abstract Syntax Notation One
                                                      ISD         Inter-Site Distance
 B2B        Business-to-Business
                                                      ITU         International Telecommunication Union
 CA         Carrier Aggregation
                                                      LCS         Location Services
 CAPEX      Capital Expenditure
                                                      LIPA        Local IP Access
 CN         Core Network
                                                      LS          Liaison Statement
 CP         Control Plane
                                                      LTE         Long Term Evolution
 CS         Circuit-Switched

                                                                                                          9
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ROAD TO 5G: INTRODUCTION AND MIGRATION

 MCG       Master Cell Group                     SIPTO    Selected IP Traffic Offload
 MCPTT     Mission Critical Push-To-Talk         SM       Session Management
 mIoT      Massive IoT                           SMF      Session Management Function
 MME       Mobility Management Entity            SMS      Short Message Service
 mMTC      Mobile Machine Type Communications    SN       Secondary Node
 MN        Master Node                           SRVCC    Single Radio Voice Call Continuity
 MPS       Multimedia Priority Service           TB       Terabyte
 MR-DC     Multi-RAT Dual Connectivity           TCO      Total Cost of Ownership
 NAS       Non Access Stratum                    TV       Television
 NB-IoT    Narrowband-IoT                        TWAG     Trusted Wireless Access Gateway
 NE-DC     NR E-UTRA Dual Connectivity           TX       Transmission
 NF        Network Function                      U-20     Under 20
 NFV       Network Function Virtualization       UDM      User Data Management
 NGEN-DC   NG-RAN E-UTRA-NR Dual Connectivity    UE       User Equipment
 NR        New Radio                             UL       Uplink
 NRF       Network Repository Function                    Universal Mobile Telecommunications
                                                 UMTS
 NSA       Non-Standalone                                 System

 NWDA      Network Data Analytics                UPF      User Plane Function
                                                          Ultra-Reliable Low Latency
 OEM       Original Equipment Manufacturer       URLLC
                                                          Communications
 PCF       Policy Control Function
                                                 USA      United States of America
 PCRF      Policy and Charging Rules Function
                                                 ViLTE    Video over LTE
 P-CSCF    Proxy Call Session Control Function
                                                 VoLTE    Voice over LTE
 PDCP      Packet Data Convergence Protocol
                                                 VoWiFi   Voice over WiFi
 PGW       PDN (Packet Data Network) Gateway
                                                 WLAN     Wireless Local Area Network
 PGW-C     Control plane of the PGW
 PGW-U     User plane of the PGW
 QCI       QoS Class Identifier
 QoE       Quality of Experience
 QoS       Quality of Service
 RAN       Radio Access Network
 RAT       Radio Access Technology
 RRC       Radio Resource Control
 RX        Reception
 SA        Standalone
 SBA       Service Based Architecture
 SCG       Secondary Cell Group
 SGW       Serving Gateway
 SIG       Special Interest Group
 SIP       Session Initiation Protocol

10
ROAD TO 5G: INTRODUCTION AND MIGRATION

1.3 References
 Ref       Title                                      3GPP TS 23.501 System
  [1]      “5G New Wave”, 5G Forum             [11]   Architecture for the 5G System;
           “5G PPP use cases and performance          Stage 2
  [2]
           evaluation models”, 5GPPP                  3GPP TS 23.502 Procedures for the
                                               [12]
           “5G Spectrum Public Policy                 5G System; Stage 2
  [3]
           Position”, GSMA                            3GPP TS 36.300 Evolved Universal
  [4]      “5G White Paper”, NGMN                     Terrestrial Radio Access (E-UTRA)
                                               [13]   and Evolved Universal Terrestrial
           “Mobile Broadband Transformation
  [5]                                                 Radio Access Network (E-UTRAN);
           LTE to 5G”, 5G Americas
                                                      Overall description; Stage 2
  [6]      “The 5G Era”, GSMA
                                                      3GPP TS 37.340 Evolved Universal
  [7]      “Understanding 5G”, GSMAi                  Terrestrial Radio Access (E-UTRA)
                                               [14]
           “White Paper on 5G Vision and              and NR
  [8]
           Requirements”, IMT-2020 PG                 Multi-connectivity; Stage 2
           3GPP TS 23.214 Architecture                3GPP TS 38.300 NR; Overall
                                               [15]
  [9]      enhancements for control and user          description; Stage 2
           plane separation of EPC nodes              ITU-R M.2083 “IMT-2020 Vision”,
                                               [16]
           3GPP TS 23.401 General Packet              ITU-R
           Radio Service (GPRS) enhancements          R2-1713952 LS Reply to SA WG2 on
  [10]     for Evolved Universal Terrestrial   [17]
                                                      Status Icon related to 5G
           Radio Access Network (E-UTRAN)
                                                      S2-178933 LS Reply to SA WG2 on
           access                              [18]
                                                      Status Icon related to 5G

                                                                                               11
ROAD TO 5G: INTRODUCTION AND MIGRATION

2
2. Why 5G?

12
ROAD TO 5G: INTRODUCTION AND MIGRATION

 Table 3: Key performance requirements of IMT-2020

2.1 The advent of the 5G era                          2.2 Drivers of 5G
Unlike previous generations of mobile networks,       While previous generations of mobile networks
the fifth generation (5G) technology is expected      were purpose built for delivering communications
to fundamentally transform the role that              services such as voice and messaging (e.g. 2G) or
telecommunications technology plays in society.       mobile broadband (e.g. 4G), 5G will have
5G is also expected to enable further economic        flexibility and configurability at the heart of its
growth and pervasive digitalisation of an hyper-      design to enable mobile operators to serve IoT
connected society, where not only are all people      (Internet of Things) use cases and to support
are connected to the network whenever needed,         ultra-reliable, low latency connections as well as
but also many other devices/things virtually          enhanced mobile broadband [4], [5], [6], [16].
creating the society with everything connected        Particularly, new use cases designed to support
(i.e. Internet of Everything) [1], [7]. It is not a   smart cities, smart agriculture, logistics and public
coincidence that governments around the world         safety agencies will deeply impact for the better
(especially in the most advanced economies such       every aspect of our lives.
as China, EU, Japan, Korea and USA) are
demanding acceleration in the introduction of 5G      2.3 Expectations on 5G
technology in their respective markets.               Technically, 5G is a system designed to meet the
                                                      requirements of IMT-2020 set by the ITU-R
The variety of business models and services that      specification M.2083 [16]. 5G will provide more
5G systems will support, however, leads to            advanced and enhanced capabilities compared to
numerous strategies a mobile operator has             4G LTE (IMT-Advanced). The following table
available to introduce 5G services. As global reach   summarises some of the key performance
and economies of scale for network equipment as       parameters.
well as devices remain a vital component for the
success of a mobile telecommunications networks,      It can be noted that 5G will aim to provide 20
it is important to ensure that although different     times the peak data rate (speed), 10 times lower
operators may follow different 5G introduction        latency (responsiveness) and 3 times more
and deployment options, those two tenets are          spectral efficiency than 4G LTE.
preserved.

                                                                                                         13
ROAD TO 5G: INTRODUCTION AND MIGRATION

2.4 Use cases and spectrum bands for 5G                        mixture of coverage and capacity for 5G services.
5G has three major use case classes: enhanced                  There is a reasonable amount of existing mobile
Mobile Broadband (eMBB), mIoT and ultra-reliable               broadband spectrum identified with this range
low latency (URLLC). The requirements for the                  which could be used for initial 5G deployments.
use case classes and the use cases within each                 Spectrum bands above 6GHz provide significant
class vary significantly [2], [4], [8]. For example,           capacity thanks to the very large bandwidth that
smart meters will require only periodic                        can be allocated to mobile communications and
transmission of relatively small sized traffic while           thus enable enhanced mobile broadband
enhanced mobile broadband will require bursty                  applications [3]. The downside of using high
/continuous transmission of large size traffic.                spectrum bands (so called “millimetre wave”2) is
                                                               the much reduced coverage size of each cell and
In terms of spectrum bands earmarked for                       its susceptibility to blocking.
deployment of 5G, they can be sub-divided in
three macro categories: sub-1GHz, 1-6GHz and                   This variety of requirements and spectrum needs
above 6GHz.                                                    show that there are many options of 5G
                                                               introduction and different spectrum bands will be
Sub-1GHz bands are suitable to support IoT                     needed to support all use cases. Operators must
services and extend mobile broadband coverage                  therefore consider the feasibility of different
from urban to suburban and rural areas. This is                options in meeting their intended initial use cases
because the propagation properties of the signal               and interoperability of their choice with other
at these frequencies enable 5G to create very                  options to ensure their networks deliver the use
large coverage areas and deep in-building                      cases effectively while supporting global
penetration. The 1-6GHz bands offer a reasonable               interoperability.

    Figure 2: Capacity and coverage considerations of spectrum
    categories

2
 As the wavelength is defined as the ratio between the speed   obtained at 30 GHz, however it is common practice to use this
of light and the frequency of the wave, a 1 mm wavelength is   terminology for spectrum bands above 25 GHz.

14
Part I:
3. 5G Network
Deployment Options
ROAD TO 5G: INTRODUCTION AND MIGRATION

3.1 Standalone (SA) and Non-standalone (NSA)           Dual Connectivity: Operation where a given
                                                       UE consumes radio resources provided by at
As with the previous generations, 3GPP is defining     least two different network points (e.g. NR
both a new 5G core network, referred to as 5GC,        access from gNB and LTE access from eNB).
as well as a new radio access technology called
                                                      Three variations of NSA are defined in 3GPP:
5G “New Radio” (NR). Unlike previous generations
that required that both access and core network          • Option 3 using EPC and an LTE eNB acting
of the same generation to be deployed (e.g.                as master and NR en-gNB acting as
Evolved Packet Core (EPC) and LTE together                 secondary;
formed a 4G system), with 5G it is possible to           • Option 4 using 5GC and an NR gNB acting
integrate elements of different generations in             as master and LTE ng-eNB acting as
                                                           secondary; and
different configurations, namely:
                                                         • Option 7 using 5GC and an LTE ng-eNB
                                                           acting as master and an NR gNB acting as
     • Standalone using only one radio access
                                                           secondary.
       technology and
     • Non-Standalone combining multiple radio
       access technologies.                           3.2 Evolved Packet Core (EPC) and 5G Core
                                                      Network (5GC)
In a standalone scenario, the 5G NR or the            5G deployment options are being defined in 3GPP
evolved LTE radio cells and the core network are      using either the existing EPC (Evolved Packet
operated alone. This means that the NR or             Core, specified in 3GPP TS 23.401 [10]) or the
evolved LTE radio cells are used for both control     5GC (5G Core network, specified in 3GPP TS
plane and user plane. The standalone option is a      23.501 [11]).
simple solution for operators to manage and may
be deployed as an independent network using           The two architectures follow a very different set
normal inter-generation handover between 4G           of design principles and the main differences are
and 5G for service continuity.                        discussed more in detail in section 7.2.

Three variations of SA are being defined in 3GPP:     While EPC could be considered an evolution of
                                                      previous generation packet core networks, the
     • Option 1 using EPC and LTE eNB access          5GC has been designed from its inception to be
       (i.e. as per current 4G LTE networks);         “cloud native”, that is inheriting many of the
     • Option 2 using 5GC and NR gNB access;          technology solutions used in cloud computing and
       and
                                                      with virtualisation at its core. 5GC also offers
     • Option 5 using 5GC and LTE ng-eNB access
                                                      superior network slicing and QoS features.
                                                      Another important characteristic is the separation
In non-standalone (NSA) scenario, the NR radio
                                                      of the control plane and user plane that besides
cells are combined with LTE radio cells using dual-
                                                      adding flexibility in connecting the users also
connectivity to provide radio access and the core
                                                      allows an easier way to support a multitude of
network may be either EPC or 5GC depending on
                                                      access technologies, better support for network
the choice of operator. This scenario may be
                                                      slicing and edge computing.
chosen by operators that wish to leverage existing
4G deployments, combining LTE and NR radio            NOTE: from 3GPP Release 14 onwards, the
resources with existing EPC and/or that wish new      separation of control plane and user plane is also
5GC to deliver 5G mobile services. This solution      an available option in 4G.
will require tight interworking with the LTE RAN.
The end user experience will be dependent on the
radio access technology(ies) used.

16
ROAD TO 5G: INTRODUCTION AND MIGRATION

Figure 3: Overview of SA and NSA Options

 Standalone LTE under EPC    Standalone NR under 5GC         Standalone LTE under 5GC (option
         (option 1)                 (option 2).                             5)

 Non-standalone LTE and NR   Non-standalone NR and LTE       Non-standalone LTE and NR under
    under EPC (option 3)       under 5GC (option 4).                  5GC (option 7)
ROAD TO 5G: INTRODUCTION AND MIGRATION

Part I:
4. 5G Network
Introduction &
Migration paths

18
ROAD TO 5G: INTRODUCTION AND MIGRATION

4.1 General observations and assumptions                2017 (see
                                                        http://www.3gpp.org/specifications/releases).
As discussed in the previous section, 5G can be
introduced either in standalone mode (option 2          4.2.3 Deployment Considerations
and option 5) using 5GC or in non-standalone
                                                        Compared to EPC-based deployment options such
mode, using EPC (option 3) or 5GC (options 4 and
                                                        as Option 1 and Option 3, this option provides an
7).
                                                        open, flexible, and service-based network
There are therefore several possible “paths”            architecture for 5G which can fully exert the
operators can follow to first introduce 5G and          ability of 5G. In this context, it may be considered
then migrate it to the target configuration(s). This    as the deployment choice for operators who need
section presents a selection of what are thought        to fulfil the market requirements, especially of
to be likely introduction and migration scenarios.      vertical industries. It is also a long term network
Readers should be aware that many aspects need          architecture as it already uses both the newly
to be considered when deciding on the best              defined radio and core network.
migration strategy, including spectrum allocation,
                                                        Direct interworking between 5GS and 2G/3G CS
support for other service and industries, and
                                                        domain is not considered at the beginning of
support of 5G capabilities in terminals.
                                                        deployment for this option.
In this section, it is assumed that the operator:

   • has deployed a full 4G system comprising
     an EPC and LTE access
   • plans to migrate in mid- or long-term to
     5GS.

4.2 EPS to SA Option #2
4.2.1 Description
In this scenario the operator migrates directly
from EPS (Option 1) to the standalone Option 2
with inter-RAT mobility mechanisms used to move
devices between 4G LTE under EPC coverage and
5G NR under 5GC coverage.

4.2.2 Feasibility of the path in meeting 5G use
cases
One of the key benefit of this option is that SA
architecture can take full advantage of 5G end-to-
end network capabilities supported by NR and
5GC, providing customized service, especially to
vertical industry, in an effective and efficient way.
New features, including service-based
architecture, end-to-end network slicing, and
MEC, can be enabled according to specific
requirement of each service, providing customized
superior user experience. The 3GPP specifications
of Option 2 will be completed by June 2018 with
the 5GC stage 2 specification completed in Dec.

                                                                                                          19
ROAD TO 5G: INTRODUCTION AND MIGRATION

 Figure 4: Description of EPS to SA Option #2

4.2.4 Impact on Device and Network                     The UE supports complete set of functionalities
SA Option #2 envisages the deployment of both          for Control-Plane and User-Plane and for all
NR gNB based NG-RAN as a new radio access and          interfaces to the network.
5GC as new core along with new features on LTE
                                                       To avoid the coverage limitations in UL due to
eNB based E-UTRAN to support inter-RAT
                                                       different TX/RX configurations and network
mobility. Option #2 requires the device to support
                                                       deployment between downlink and uplink, high
both a radio front end capable of receiving and
                                                       power UE can be used to enhance UL coverage.
transmitting data over NR as well as new
procedures for the 5GC.                                4.2.5 Impact on voice including service continuity

Since SA operator provides services that are           NOTE: a detailed description of the technical
delivered over standalone 5GS, interworking            implications for providing service continuity in this
between 5GS and EPS for service continuity for         scenario is provided in Section 9.
those services may be required. Based on
                                                       Depending on whether the operator supports
operator strategy, single registration solution with
                                                       voice services over IMS and whether it provides
or without AMF-MME interface as defined in 3GPP
                                                       national coverage (i.e. 100% of its coverage) or
TS 23.501/502 can be deployed [11], [12].
                                                       less, the feasibility of voice service continuity in
Converged nodes of SMF+PGW-C, UPF+PGW-U,
                                                       this migration step will differ.
UDM+HSS and PCRF+PCF are needed
accordingly. MME is also impacted to support 5GS       If the operator provides VoLTE (Voice over LTE)
and EPS interworking for converged SMF+PGW-C           with national coverage, then the operator can
selection or for dual registration without AMF-        either provide IMS voice service over 5G network
MME interface.                                         (5GS) or utilize existing VoLTE service. If IMS
                                                       voice service over 5G network (5GS) is not
Since Dual-connectivity is not required for Option
                                                       provided, the operator may still be in the position
#2, workload and cost for 4G existing eNB
                                                       to provide voice by adopting non-standardised
upgrade and modification is relatively low, with
                                                       solutions, hence requiring experimental approach.
only minor upgrades needed to support
                                                       If the operator only offers VoLTE service over
interworking with 5G.
                                                       EPS, then interworking of 5GS with EPS is

20
ROAD TO 5G: INTRODUCTION AND MIGRATION

necessary for subscribers to fall back from 5G to     finishing the specification for other options (see
4G when voice service is required.                    3GPP news article on approval of NR spec and
                                                      industry support for 3GPP NR)
If the operator provides VoLTE with partial
coverage and CS voice complements VoLTE to            Besides the accelerated time to market, as the NR
support national coverage, then the operator          will augment the existing capability of the LTE
needs to utilize existing VoLTE service and ensure    radio network, this option allows flexible “on
that continuity between LTE and CS access is          demand” deployment where capacity is needed
implemented (i.e., SRVCC: Single Radio Voice Call     using the same or different vendors for LTE and
Continuity). In the case where the VoLTE service      NR. Furthermore, this option is going to be
does not provide continuity between LTE and CS        maintained in future releases of 3GPP (beyond
access, then the voice call continuity would not be   release 15) and therefore can be used in longer-
guaranteed for regions where VoLTE is not             term, even if other options are deployed in
supported.                                            parallel.

If the operator does not provide VoLTE and            The capability of deploying NR while anchoring
provides CS voice with national coverage only,        the communication to the EPC network offers the
then this migration step would involve some           opportunity of making optimal use of the
investment. The operator would need to provide        spectrum above 6GHz where operators will have
national coverage IMS voice service over 5G           available the large bandwidths necessary to
network (5GS). Otherwise, the migration step          deliver the high throughput in hotspots but that
would not guarantee voice service continuity as       cannot be provided easily over large areas due to
there is no standardized solution for 5G networks     the fast signal attenuation. However, NR in option
(5GS) equivalent to the SRVCC operation defined       3 can also be deployed in spectrum bands below
for 4G networks (EPS) in initial release of 5G        6GHz and the example above should be
(3GPP Release 15). Note that there is also no         considered as illustration of one of the possible
Circuit Switched Fallback (CSFB) operation            deployment scenarios.
available for 5GS.
                                                      4.3.3 Deployment considerations of option 3
4.3 EPS to NSA Option #3                              Depending on the EPC features defined by 3GPP
4.3.1 Description                                     in Release 15 and future releases, the EPC
This section covers the migration from EPS            capabilities may represent a possible bottleneck
(Option 1) to non-standalone Option 3 with the E-     (e.g., latency) that limits the performance that
UTRA extended to allow compatible devices to use      could otherwise be extracted from NR.
dual connectivity to combine LTE and NR radio
                                                      Data throughput per 5G connected subscriber
access.
                                                      (e.g. in SGW/PGW) is expected to increase via NR
4.3.2 Feasibility of the path in meeting 5G use       and LTE in dual-connectivity. While the increase
cases                                                 of data requires additional consideration in
                                                      network planning (for example, adding user plane
One of the key advantages of this option is that it
                                                      nodes for SGW/PGW), adoption of additional
only requires the development of specifications of
                                                      features in the latest releases of 3GPP
NR as non-standalone access as part of E-UTRAN
                                                      specification may resolve the challenge.
connected to EPC rather than the specification of
the full 5G system as it is the case for standalone   Finally, as the 5GC is not going to be used in this
NR in section 4.2 and other 5GS cases. In Dec.        option, none of the differentiating capabilities of
2017, 3GPP completed the specifications of Option     the new architecture described in Section 7.1.2
3 with the corresponding ASN.1 encoding due in        are available to the operator.
March 2018 as an intermediate milestone before

                                                                                                           21
ROAD TO 5G: INTRODUCTION AND MIGRATION

 Figure 5: Description of EPS to NSA Option #3

4.3.4 Impact on Device and Network                      not, the feasibility of voice service continuity in
NSA Option #3 requires deployment of NSA NR             this migration step will differ.
en-gNB in E-UTRAN and new features on LTE eNB
                                                        If the operator provides VoLTE with national
to support EN-DC procedures, hence has impacts
                                                        coverage, then there is no negative impact
on E-UTRAN. NSA Option #3 has also impact on
                                                        associated with migrating from EPS to NSA Option
UE, but limited impact on EPC and HSS depending
                                                        #3. The operator can utilize existing VoLTE
on operators’ choice, and no impact on IMS.
                                                        service.
From the point of view of the device, the
                                                        NOTE: The operator can also choose to upgrade
attractiveness of this solution is that it only
                                                        VoLTE to utilize NR
requires the additional support of specifications of
NR as non-standalone access as part of E-UTRAN          If the operator provides VoLTE with partial
connected to EPC. The device will communicate           coverage and CS voice complements VoLTE to
with the core network using the same EPC                support national coverage, then the operator
procedures used by currently available devices          needs to utilize existing VoLTE service and ensure
either under only LTE or under both LTE and NR          that continuity between LTE and CS access is
radio coverage. It should be noted however that         implemented (e.g., SRVCC). However, this is
combining of LTE and NR radio interfaces for split      something an operator would consider
bearers may increase memory requirements.               independently from the deployment of 5G to
                                                        ensure voice service continuity.
4.3.5 Impact on IMS voice including service
continuity                                              If the operator does not provide VoLTE and
NOTE: a detailed description of the technical           provides CS voice with national coverage only,
implications for providing service continuity in this   then the operator needs to utilize existing CS
scenario is provided in Section 9.                      voice service and ensure CSFB is implemented. As
                                                        is the case of VoLTE with complementary CS
Depending on whether the operator supports              voice, the decision to adopt this technical solution
voice services over IMS and whether it provides         is independent from the introduction of 5G.
national coverage (i.e. 100% of its coverage) or

22
ROAD TO 5G: INTRODUCTION AND MIGRATION

 Figure 6: Description of NSA Option #3 to NSA Option #7 and SA
 Option #5

NOTE 1: Early 5G device refers to devices that support only NSA Option #3 5G deployment option
NOTE 2: New 5G device refers to devices that support NSA Option #3 and also other 5G deployment option(s)

4.4 NSA Option #3 to NSA Option #7 and SA                     have an EPC protocol stack. Mobile network
Option #5                                                     operators are likely to maintain Option #3 support
4.4.1 Description                                             after the introduction of Options #7/5. LTE RAN
                                                              also needs upgrade to connect to 5GC and more
This section covers the migration from non-
                                                              LTE base stations (eNode B) may need to be
standalone Option 3 to non-standalone Option 7
                                                              upgraded to interwork with NR. This path also
and standalone Option 5 with RAN connectivity to
                                                              requires tight interworking between LTE and NR.
5GC in parallel to EPC connection for early 5G
devices.                                                      This path allows operators to continue to
                                                              selectively deploy NR only where needed. As LTE
4.4.2 Feasibility of the path in meeting 5G use
cases                                                         is already offered in wide-area coverage in initial
                                                              condition (NSA Option #3), the network can still
Whereas the network was not able to leverage                  leverage the wide-area coverage LTE network and
the advantages of 5GC in NSA Option #3, in this               deploy NR only when intended use case requires
path 5GC is deployed so that the full advantage of            it.
5G end-to-end network capabilities can be
delivered to the users. This path enables                     4.4.4 Impact on Device and Network
operators to provide initial 5G use cases (e.g.,
                                                              Option #7/5 upgrade from Option 3 requires
mobile broadband) leveraging LTE and EPC
                                                              deployment of 5GC and upgrade of LTE eNB to
installed base, while new use cases can be
                                                              support 5GS session, mobility, QoS management
addressed on clean slate 5GS architecture.                    and MR-DC procedures and 5GC N2/3 RAN-core
4.4.3 Deployment considerations                               interfaces along with upgrade of NR gNB to
                                                              support 5GC N3 RAN-Core user plane interface. In
Since the 5GC is now used, this path requires that
                                                              addition to the need to deploy the new 5GC and
devices support the new protocol stack to access              (for Option 7) DC, devices will need to support
this core network. This is problematic not only for
                                                              5GC NAS messages, devices and E-UTRA need to
legacy 4G-only devices, but also for early 5G                 support extensions to the LTE RRC layer, E-UTRA
devices supporting only NSA Option #3 that only

                                                                                                              23
ROAD TO 5G: INTRODUCTION AND MIGRATION

will need upgrades to terminate the 5GC N2/3            there is no standardized solution for 5G networks
RAN-Core interfaces and both E-UTRA and IMS             (5GS) equivalent to the SRVCC operation defined
will require upgrades to support changes to QoS         for 4G networks (EPS) in initial release of 5G
model. N2 interface is the interface between the        (3GPP Release 15).
5G RAN and AMF, while N3 interface is the
interface between the 5G RAN and UPF.                   4.5 NSA Option #3 to NSA Option #3 and SA
                                                        Option #2
4.4.5 Impact on IMS voice including service             4.5.1 Description
continuity
                                                        This section covers the migration from having
NOTE: a detailed description of the technical           only non-standalone Option 3 to adding
implications for providing service continuity in this   standalone Option 2 with inter-RAT mobility
scenario is provided in Section 9.                      mechanisms used to move devices between 5G
                                                        NSA LTE plus NR under EPC coverage and 5G NR
Depending on whether the operator supports
                                                        under 5GC coverage.
voice services over IMS and whether it provides
national coverage (i.e. 100% of its coverage) or        4.5.2 Feasibility of the path in meeting 5G use
not, the feasibility of voice service continuity in     cases
this migration step will differ.
                                                        Whereas the network was not able to leverage
If the operator provides VoLTE with national            the advantages of 5GC in NSA Option #3, in this
coverage, then there is no significant impact to        path 5GC is deployed so that the full advantage of
service continuity as a result of migrating from        5G end-to-end network capabilities can be
NSA Option #3 to NSA Option #7 and SA Option            delivered to the users. This path enables
#5. The operator can either provide IMS voice           operators to address all use cases on clean slate
service over 5G network (5GS) or utilize existing       5GS architecture. However, the operator may
VoLTE service. If IMS voice service over 5G             need to consider migration of initial use cases
network (5GS) is provided, the operator will need       served by EPC to 5GC if all use cases are to be
to ensure that adequate tests are performed. If         supported by 5GC.
VoLTE service is utilized, then EPC is necessary
                                                        4.5.3 Deployment considerations
for subscribers when voice service is used.
                                                        Since there is no tight interworking at radio level
If the operator provides VoLTE with partial             between 4G and 5G, this path works best when
coverage and CS voice complements VoLTE to              NR has been deployed to support wide-area
support national coverage, then the operator            coverage: while operators can offer seamlessly
needs to utilize existing VoLTE service and ensure      handover traffic from 5GC to EPC, this transition
that continuity between LTE and CS access is            requires also a change of core network
implemented (e.g., SRVCC and CSFB). In the case         architecture and QoS model and therefore should
where the VoLTE service does not provide                not be used too frequently.
continuity between LTE and CS access, then the
voice call continuity would not be guaranteed for       Early 5G devices supporting only NSA Option #3,
regions where VoLTE is not supported.                   and capable of communicating only with EPC, will
                                                        be able to use their 5G radio capabilities in the
If the operator does not provide VoLTE and              target scenario provided the gNB is able to
provides CS voice with national coverage only,          support both option #2 and #3 devices
then this migration step would involve some             simultaneously.
investment. The operator would need to provide
national coverage IMS voice service over 5G             4.5.4 Impact on Device and Network
network (5GS). Otherwise, the migration step            Option #2 requires deployment of 5GC and
would not guarantee voice service continuity as         update of NR gNB to support both NSA (option

24
ROAD TO 5G: INTRODUCTION AND MIGRATION

#3) and SA (option #2) in parallel. Option #2 has             inter-RAT mobility, IMS to support 5GS QoS
impacts on E-UTRAN connected to EPC to support                management and also on UE.

 Figure 7: Description of NSA Option #3 to NSA Option #3 and SA
 Option #2

NOTE 1: Early 5G device refers to devices that support only NSA Option #3 5G deployment option
NOTE 2: New 5G device refers to devices that support NSA Option #3 and also other 5G deployment option(s)

4.5.5 Impact on IMS voice including service                   If the operator provides VoLTE with partial
continuity                                                    coverage and CS voice complements VoLTE to
NOTE: a detailed description of the technical                 support national coverage, then the operator
implications for providing service continuity in this         needs to utilize existing VoLTE service and ensure
scenario is provided in Section 9.                            that continuity between LTE and CS access is
                                                              implemented (e.g., SRVCC). In the case where
Depending on whether the operator supports                    the VoLTE service does not provide continuity
voice services over IMS and whether it provides               between LTE and CS access, then the voice call
national coverage (i.e. 100% of its coverage) or              continuity would not be guaranteed for regions
not, the feasibility of voice service continuity in           where VoLTE is not supported.
this migration step will differ.
                                                              If the operator does not provide VoLTE and
If the operator provides VoLTE with national                  provides CS voice with national coverage only,
coverage, then there is no significant impact                 then this migration step would involve some
associated with migration from NSA Option #3 to               investment. The operator would need to provide
SA Option #2. The operator can either provide                 national coverage IMS voice service over 5G
IMS voice service over 5G network (5GS) or utilize            network (5GS). Otherwise, the migration step
existing VoLTE service. Prior to the adoption of              would not guarantee voice service continuity as
IMS voice service over 5G network (5GS), the                  there is no standardized solution for 5G networks
operator may need to perform extensive testing.               (5GS) equivalent to the SRVCC operation defined
If VoLTE service is utilized, then it is necessary to         for 4G networks (EPS) in initial release of 5G
continue to support EPC for subscribers using                 (3GPP Release 15).
voice services.

                                                                                                             25
ROAD TO 5G: INTRODUCTION AND MIGRATION

4.6 NSA Option #3 to NSA Option #4 and SA               This section covers the migration from non-
Option #2                                               standalone Option 3 to non-standalone Option 4
4.6.1 Description                                       and standalone Option 2 with RAN connectivity to
                                                        5GC in parallel to EPC connection for early 5G
                                                        devices.

 Figure 8: Description of NSA Option #3 to NSA Option #4 and SA
 Option #2

NOTE 1: Early 5G device refers to devices that support only NSA Option #3 5G deployment option

NOTE 2: NSA 5GC device refers to devices that support NSA Option #4

NOTE 3: SA 5GC device refers to devices that support SA Option #2

4.6.2 Feasibility of the path in meeting 5G use         operators will keep maintaining the EPC for long-
cases                                                   term. In addition, LTE RAN needs upgrade to
In this path, unlike in NSA Option #3, the 5GC          connect to 5GC and more LTE base stations
core network is used to replace the EPC in serving      (eNodeB) may need to be upgraded to interwork
5G use cases (if 5GC replaces EPC completely            with NR. This path also requires tight interworking
then legacy 4G UEs or UEs with 4G only                  between LTE and NR.
subscription will no longer be served). This means
                                                        This path allows operators to continue to
that users can takes full advantage of 5G end-to-
                                                        selectively deploy NR only where needed.
end network capabilities. This path enables
                                                        However, compared with the migration described
operators to address all use cases on clean slate
                                                        in section 4.4., this path may require the
5GS architecture. However, the operator may
                                                        deployment of a larger number of more NR gNB
need to consider migration of initial use cases
                                                        since NR acts as is the master node with LTE
served by EPC to 5GC if all use cases are to be
                                                        secondary node in the area where option #4 is to
supported by 5GC.
                                                        be used. As the starting point of this migration is
4.6.3 Deployment considerations                         scenario #3 where NR and eLTE are already
                                                        tightly interworking, it is possible to continue to
Early 5G devices supporting only NSA Option #3
                                                        leverage the wide area coverage of LTE and
and only able to connect to EPC will imply that

26
ROAD TO 5G: INTRODUCTION AND MIGRATION

supplement it with selective NR deployment based        If the operator provides VoLTE with partial
on demand.                                              coverage and CS voice complements VoLTE to
                                                        support national coverage, then the operator
4.6.4 Impact on Device and Network                      needs to utilize existing VoLTE service and ensure
Option #4/2 upgrade from Option 3 requires              that continuity between LTE and CS access is
deployment of 5GC and upgrade of NR gNB to              implemented (e.g., SRVCC). In the case where
support 5GS session, mobility, QoS management           the VoLTE service does not provide continuity
and MR-DC procedures and 5GC N2/3 RAN-core              between LTE and CS access, then the voice call
interfaces along with upgrade of LTE eNB to             continuity would not be guaranteed for regions
support 5GC N3 RAN-Core user plane interface            where VoLTE is not supported.
(only required if option 4A is adopted). N2
interface is the interface between the 5G RAN and       If the operator does not provide VoLTE and
AMF, while N3 interface is the interface between        provides CS voice with national coverage only,
the 5G RAN and UPF. This step also has impacts          then this migration step would involve some
on IMS to support 5GS QoS management and also           investment. The operator would need to provide
on UE (refer to Section 7 for more details).            IMS voice service over 5G network (5GS).
                                                        Otherwise, the migration step would not
4.6.5 Impact on IMS voice including service             guarantee voice service continuity as there is no
continuity                                              standardized solution for 5G networks (5GS)
NOTE: a detailed description of the technical           equivalent to the SRVCC operation defined for 4G
implications for providing service continuity in this   networks (EPS) in initial release of 5G (3GPP
scenario is provided in Section 9.                      Release 15).

Depending on whether the operator supports              4.7 Other migration steps
voice services over IMS and whether it provides         This section lists the migration steps that are not
national coverage (i.e. 100% of its coverage) or        covered in this version of the document for
not, the feasibility of voice service continuity in     reader’s information:
this migration step will differ.
                                                           •   NSA Option #7 to NSA Option #4
If the operator provides VoLTE with national               •   SA Option #5 to NSA Option #4
coverage, then there is no significant impact              •   EPS to NSA Option #4
associated with migrating from NSA Option #3 to            •   EPS to NSA Option #7
NSA Option #4. The operator can either provide
IMS voice service over 5G network (5GS) or utilize      NOTE: The list above is not exhaustive and
existing VoLTE service. Prior to the adoption of        includes only the migration steps that are
IMS voice service over 5G network (5GS), the            considered as more likely by the project group
operator may need to perform extensive testing.
If VoLTE service is utilized, then EPC is necessary
for subscribers when voice service is used.

                                                                                                         27
ROAD TO 5G: INTRODUCTION AND MIGRATION

Part I:
5. Recommendations
for collaborative
actions

28
ROAD TO 5G: INTRODUCTION AND MIGRATION

The variety of options and migration steps
available for deploying 5G allow operators to
adopt different strategies that suit the specific
market situations, business models and
competition needs. Also, customers and the wider
industry will benefit as a whole from operators
taking certain collaborative actions that are aimed
to guarantee service continuity, service and
network interoperability and to unlock economies
of scale. Similar to the work carried out earlier for
IMS services (e.g. VoLTE, VoWiFi, ViLTE), a profile
should define the minimum requirements that
need to be fulfilled in order to ensure
interoperability, roaming and portability across the
various 5G deployment options. These profiles
should aim to address:

   • Basic connectivity of devices to a 5G
     network including interoperability between
     5G and LTE networks
   • IMS services delivered over NR
   • Support roaming to/from networks with
     same/different 5G deployment option

The creation of a database of issues to be
encountered during the 5G commercialisation, as
it was done for IMS services, will allow the
industry to efficiently address them and find
solutions that every stakeholder will benefit from.

                                                                                             29
ROAD TO 5G: INTRODUCTION AND MIGRATION

Part II:
6. Study of 5G
network introduction
case

30
ROAD TO 5G: INTRODUCTION AND MIGRATION

This section contains 5G case studies contributed by KT to share their 5G network introduction
cases to provide insights and foresight for challenges in 5G commercialisation in the near future.
This case study addresses KT’s 5G trial activities, tentative 5G commercialization plan and
roadmap, issues in 5G deployment/migration and KT’s challenges from technology and business
perspectives.

6.1 Why 5G?                                           during major events, as shown in Figure 9. During
6.1.1 5G technology and service trial activities      the FIFA U-20 World cup held in South Korea,
                                                      interactive broadcasting of soccer games using
To develop early technical specifications for 5G
                                                      360-degree VR and Time Slice technology was
trial system and services for the PyeongChang
                                                      offered through 5G connections.
Winter Olympics that will be held in February
2018, KT launched ‘5G SIG (Special Interest           The 5G trial system including core and radio
Group)’ along with global mobile manufacturers        access network, along with the 5G trial devices,
(Ericsson, Intel, Nokia, Qualcomm, and Samsung)       will be deployed by the end of 2017 in Seoul and
in September 2015 and then completed the 5G           Olympic venue areas. 5G trial services will be
SIG specifications in November 2016.                  offered during the Olympic Games in
                                                      PyeongChang, GangReung, JeongSeon, and
Furthermore, KT successfully completed the IOC
                                                      BoGwang areas as well as in Seoul.
Olympic Test Events in 2016 and 2017 based on
5G trial base stations and terminals. KT is           In PyeongChang Olympics, various 5G trial
currently carrying out lab and field tests for        services will be offered by KT such as fixed
debugging and verifying the functionalities and       wireless access service, mobile services, and
performance of 5G as well as service demos            autonomous vehicle services.

 Figure 9: KT’s 5G Trials and Commercialization Activities

                                                                                                        31
ROAD TO 5G: INTRODUCTION AND MIGRATION

In PyeongChang Olympics, various 5G trial                 • Smart Surveillance offers perfect safety and
services will be offered by KT such as fixed                security for visitors and on-site operators
wireless access service, mobile services, and               by using connected, intelligent surveillance
                                                            fixed cameras and drones.
autonomous vehicle services. Some key examples
of the 5G services are shown in Figure 10 and             • 5G-connected Autonomous Vehicles offer
                                                            autonomous driving experience and
Figure 11.
                                                            immersive in-vehicle next-generation
                                                            media.
     • Sync View enables viewers to enjoy the
       game with high-resolution player-view
       cameras on players.                             6.1.2 Other business/social drivers in the nation
     • 360-degree Live VR offers capability for
                                                       South Korea is fully covered with nation-wide LTE
       viewers to watch interactive UHD-class
       media in 360-degrees.                           network and the LTE traffic already comprises
                                                       more than 99% of the mobile traffic. Total
     • Hologram Live enables mobile users to
       transfer next-generation 3D hologram            number of mobile subscribers is around 60 million
       media contents.                                 and smartphone adoption rate is 85% in South
     • Time Slice Broadcasting offers capability for   Korea.
       viewers to watch realistic and close slow-
       motions of Olympic events by using
       multiple connected cameras.

 Figure 10: KT’s 5G Trial Services for Olympics

32
ROAD TO 5G: INTRODUCTION AND MIGRATION

 Figure 11: KT’s 5G-connected Autonomous vehicle

Besides, the annual growth rate of mobile-           respectively. Of course, connected vehicles may
connected IoT devices in South Korea is around       accelerate the growth of mobile traffic in the
20%. It is also expected that subscribed IoT         future. Figure 12 shows the trend and forecast of
devices will grow in number as commercial IoT        mobile data traffic in South Korea from 2012 to
network based on 3GPP NB-IoT specifications was      2019. Note that projected data during December,
deployed for KT LTE network in July 2017.            2017 to December, 2020 are estimated based on
Furthermore, KT is also concentrating on             the recent mobile status reports of KCC (Korea
enterprise and B2B IoT segments like home/office     Communications Commission), South Korea.
IoT, smart factory, smart city and smart energy.
                                                     Since mobile capacity in 2020’s must be expanded
In South Korea, video traffic occupies the biggest   to accommodate the growth of mobile traffic as
portion of the traffic (i.e. 56% as of June 2017),   well as the adoption of mobile broadband services
where mobile IPTV and video streaming services       and IoT devices (especially in urban and hot-spot
over LTE connection are widely spread. That is,      areas), the early introduction and deployment of
smartphones/tablets are starting to substitute       5G mobile broadband network is inevitable.
traditional TV.
                                                     6.1.3 Deployment purpose and spectrum at
Mobile data usage in South Korea is steadily         disposal
increasing. As of June 2017, total data volume per   In South Korea, social needs and market
month exceeds 290,000 TB and monthly data            competition for reducing retail cost per mobile
volume per subscriber exceeds 5 GB. This is          data used (bit) is growing, as mobile technology is
around 5 times the average volume of mobile          widespread and is commoditized in everyday life.
traffic of the past 5 years. Besides, the growth     Therefore, timely response from mobile operators
rate of mobile traffic from the previous year is     becomes urgent. It is expected that epoch-making
around 40%. It can be estimated that mobile          cost reduction for mobile data can be achieved by
traffic of around 700,000 TB and 1,000,000 TB        introducing relatively low-cost, ultra-broadband
will be reached in the end of 2019 and 2020,         millimetre-wave bands to mobile network.

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