This document defines the following terms:
3.2.1 Network Softwarization: Network softwarization is an overall transformation trend for designing, implementing, deploying, managing and maintaining network equipment and network components by software programming, exploiting characteristics of software such as flexibility and rapidity of design, development and deployment throughout the lifecycle of network equipment and components, for creating conditions that enable the re-design of network and services architectures; allow optimization of costs and processes; and enable self-management.
3.2.2 back haul: the network path connecting the base station site and the network controller or gateway site.
3.2.3 front haul: the intra-base station transport, in which a part of the base station function is moved to the remote antenna site. (Note that this definition is equivalent to the definition given in MEF 22.1.1 for the current 4G technology.)
4 Abbreviations and acronyms
This document uses the following abbreviations and acronyms:
Ed: Not complete.
5G The fifth generation mobile network
AAA Authentication, Authorization, Accounting
APN Application Network
AR Augmented Reality
BH back haul
CCN Content Centric Networking
CGF Converged Gateway Function
CN Core Network
CPRI Common Public Radio Interface
C-RAN Cloud RAN
CS Content Store
D2D Device-to-device
D2N Device-to-Network
DBA Dynamic Bandwidth Assignment
DWDM Dense Wavelength Division Multiplex
E2E End-to-End
EPC Evolved Packet Core
FH front haul
FIB Forwarding Information Base
GBR Guaranteed Bit Rate
GW Gateway
GTP Generic Tunnelling Protocol
GTP-C GTP Control
ICN Information Centric Networking
IDC Internet Data Center
IMT International Mobile Telecommunications
IoT Internet of Things
IP Internet Protocol
IPDV IP packet Delay Variation
IPER IP packet Error Rate
IPLR IP packet Error Ratio
IPTD IP packet Transfer Delay
KPI Key Performance Index
LINP a logically isolated network partitions
LISP Location/Identity Separation Protocol
MBR Maximum guaranteed Bit Rate
MIMO Multiple-Input and Multiple-Output
MEC Mobile Edge Computing
MNO Mobile Network Operator
MPLS Multi-Protocol Label Switching
MTC Machine Type Communication
NAS Non-Access Stratum
NDN Named Data Networking
NFV Network Function Virtualization
NP Network Performance
OAM Operation, Administration and Management
OBSAI Open Base Station Architecture Initiative
ODN Optical Distribution Network
OSU Optical Subscriber Unit
OTN Optical Transport Network
PDN Packet Data Network
PGW Packet Data Network Gateway
PIF Protocol Independent Forwarding
PIT Pending Interest Table
POF Protocol Oblivious Forwarding
PON Passive Optical Network
PTN Packet Transport Network
QCI QoS Class Identifier
QoE Quality of Experience
QoS Quality of Service
RAN Radio Access Network
RAT Radio Access Technologies
RoF Radio over Fiber
TSDN Transport SDN
TWDM Time and Wavelength Division Multiplex
SDN Software Defined Networking
SR Segment Routing
UCF Unified Control Function
UE User Equipment
UHD Ultra High Definition
UMTS Universal Mobile Telecommunication System
UNI User Network Interface
VLAN Virtual LAN (Local Area Network)
VM Virtual Machine
VNF Virtual Network Function
VPN Virtual Private Network
WDM Wavelength Division Multiplex
5 Conventions
Within the context of this document, the term IMT-2020 refers to the technology and networks defined for future mobile networking. Within the telecommunications industry this is commonly referred to “fifth generation mobile networking”, or simply 5G. For the purposes of this document, IMT-2020 and 5G are synonymous.
6 Executive Summary
The purpose of this document is to provide recommends to the ITU-T on the requirements for standardization related to the wireline elements of “fifth generation mobile” (5G) or more properly referred to as IMT-2020) networks as per the terms of reference of this focus group. It is not a purpose of this document to provide a large amount of tutorial/overview material but instead to reference the copious amounts of such material where necessary and to give sufficient context that experts in the various fields can understand what gaps are being identified.
While the breadth of the document is wide we do not claim to have covered every possible aspect of IMT-2020 wireline networking, indeed IMT-2020 is a large and moving target and therefore we have had to extrapolate in many areas what we believe the wireline requirements will be and what standards are missing or need improvement. There are definitely areas we have missed that will require further study and some of these are outlined as gaps in this gap analysis.
IMT-2020 systems will differentiate themselves from fourth generation (4G) systems not only through further evolution in radio performance but also through greatly increased flexibility end-to-end. This end-to-end flexibility will come in large part from the incorporation of softwarization into every component. Well known techniques such as SDN, NFV and cloud computing will together allow unprecedented flexibility in the IMT-2020 system. Such flexibility will enable many new capabilities including network slicing.
The following figure gives a broad view of key areas that require study to effectively determine all the wireline gaps.
Figure 1: Focus Group IMT 2020 wire line potential gap analysis areas
Since the primary purpose of the focus group is to generate a list of gaps/recommendations the reader will find this list of gaps and recommendations immediately after this executive summary. Following the list of gaps/recommendations the reader will find the detailed work sub topics as appendices.
This focus group has looked at the following wireline aspects of IMT-2020 and has studied each in some detail and produced detailed gaps related to each subject. Due to the short and fixed duration of the Focus Group, there will be some areas, one example is security, which not have been addressed. This should also be considered when formulating possible new work on standardization topics.
A – High level architecture – This study focused on major requirements of IMT-2020 and the analyses of technical gaps to satisfy them. The gaps identified some of the major challenges in IMT-2020 including the diversities in requirements, particularly in bandwidth, mobility, and signalling. The flexibility of the architecture, the tight integration of various radio access networks as well as fixed access networks, end-to-end OAM, among others, are also identified as essential requirements in IMT-2020. Finally, the study provides a high-level network architecture based on the analysis of the requirements, which will be more elaborated or changed in the standardization phases.
Figure 2 provides an overall view of the architecture.
Figure 2: Network architecture for IMT-2020 networks
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B – Network softwarization – Network softwarization is an overall transformation trend for designing, implementing, deploying, managing and maintaining network equipment and network components by software programming, exploiting characteristics of software such as flexibility and rapidity of design, development and deployment throughout the lifecycle of network equipment and components, for creating conditions that enable the re-design of network and services architectures; allow optimization of costs and processes; and enable self-management. All these bring added value to network infrastructures. The terminology, Network Softwarization, was first introduced in Academia, at the NetSoft conference in 2015, the first IEEE Conference on Network Softwarization, to include broader interests regarding Software Defined Networking (SDN) and Network Functions Virtualization(NFV),Network Virtualization, Mobile Edge Computing, Cloud and IoT technologies.
Figure 3 provides an overall view of network softwarization in IMT-2020 networks.
Figure 3: Network softwarization view of IMT-2020 mobile networks
C – End-to-End QoS – This work focused on how the wireline network together with the wireless network can provide guaranteed end-to-end QoS. It provides a survey of various white papers on the subject and identifies differences in how QoS is defined/measured etc. across the different organizations. In addition to a conventional QoS standardization approach, IMT-2020-specific use cases need new approaches in areas of definition of end-to-end connectivity supervision and integrity, QoS parameters, performance objectives, QoS classification, budget allocation, measurement/monitoring methodology, etc. These gaps identify device-to-device/device-to-network QoS requiring additional standardization.
Figure 4 provides an overall view of end-to-end QoS for both wireless and wireline networks.
Figure 4: The scope end-to-end QoS standardization for 3GPP (Red) and ITU-T Standards (Purple)
D – front haul/back haul – This work focused on the different transport aspects of the IMT-2020 wireline network. front haul refers to the intra-base-station transport, where part of the base station function is moved to the remote antenna site. Back haul is the packet based communications between the base stations and the various entities that make up the packet processing elements of a core network. This work focuses almost exclusively on the front haul because this is where the majority of the gaps occur. The front haul analysis looks in detail at the projected IMT-2020 bandwidth requirements of a current C-RAN architecture and various architectural variants thereof. Most of the gaps revolve around the need to optimize the front haul network, either to reduce/right-size the bandwidth demands or to increase/optimize the bandwidth supply. An example of the former is to allow front haul to reduce bandwidth capacity when there is not much data being transmitted or received from a given remote site. An example of the latter is to use more advanced transport solutions that are tailored to the front haul application and optimized for low power, low fiber-count, and low cost. The back haul gaps however seem limited to the successful handling of network timing and synchronization, and low latency; as well as improvements in power consumption. All of these suggest gaps in the current standardized technology, many of which are already being addressed by work going on in ITU-T SG15 and various groups in the IEEE. The basic recommendation on FH/FB to SG13 is to establish liaison to all these established groups to better coordinate their efforts.
Figure 5 provides an overall view of the front haul in FMT-2020 networks.
Figure 5: IMT-2020 front haul
E- Emerging Network Technologies – This work focused on the network requirements of IMT-2020 to support enhanced mobile broadband, massive machine-type communications, and ultra-reliable low-latency communications. The work specifically looked at Information Centric Networking (ICN) protocols as possible emerging technologies to meet these needs. Current research shows ICN is possible technology that can provide benefits for IMT-2020 network supporting very large-scale heterogeneous devices, IoT networks, new mobility models, edge computing, and end device self-configuration. Because ICN is a flexible networking architecture, The study scoped the ICN gaps with several incremental deployment options, as described in Appendix V. In clause 7.5, standardization gaps have been identified for ICN deployment in IMT-2020. The basic recommendation on Emerging Network Technologies such as ICN, to SG13 is to establish liaison to IETF ICNRG, universities and research organizations to further feasibility studies.
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