Page 49 - ITU-T Focus Group IMT-2020 Deliverables
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ITU-T Focus Group IMT-2020 Deliverables                                 2


            •       Control plane of each NSI is composed of common CP NFIs and NSI specific CP NFIs. Control plane
                    of a NSI may have no common CP NFIs or no NSI specific CP NFIs;
            •       Some  NSIs  may  have  applications  used  by  end-users.  Applications  in  the  NSI  are  managed  by
                    management plane. And the applications are created from the resource in the slice management
                    and orchestration level architecture, based on the template or blue print.

            •       As new services emerge in the future, interconnection model between network functions needs to
                    allow easy  insertion of  new  network  functions while  maintaining  the existing  network  function
                    interconnection path without increasing complexity of the system.


            6       Functional architecture of IMT-2020 network

            6.1     Design principles

            From [b-ITU IMT-O-042] and [b-3GPP TR 22.861], a large number of requirements and principles of IMT-2020
            system are identified in order to design a system architecture in terms of evolutionary architecture, vertical
            industries’ demand and multiple access, etc. The following principles and characteristics are considered for
            the design of IMT-2020 network functional architecture framework:
            •       Separation of control plane (CP) and user plane (UP) functions, allowing independent scalability and
                    evolution, where CP dynamically configures UP functions (i.e. activates various operations of the
                    user plane functions as needed). The IMT-2020 network should support highly scalable distributed
                    architecture  to  avoid  signalling  congestion  and  to  minimize  the  signalling  overhead  for  diverse
                    UE/RAT/service requirements. In order to support distributed network architecture, and optimized
                    routes  for  application  data  and  signalling  data,  Control/User-plane  functions  should  be  clearly
                    separated with defined interface;
            •       Flexible deployment of UP and CP functions, i.e. centralized or distributed;
            •       Access network (AN) agnostic common core network (CN) design (e.g., AN-CN functional division
                    and a common interface between them);

            •       Efficient support of different levels of UE mobility. It is expected that mobility requirements for user
                    devices  will  vary  depending  on  the  device  and/or  application  types.  Many  user  devices  are
                    stationary, e.g., smart meters and CPE, even in mobile networks while fast handover is a key feature
                    of  most  mobile  devices  and  some  applications  may  address  the  mobility  by  setting  up  a  new
                    connection automatically with the help of buffering. Therefore, IMT-2020 should not assume the
                    same  mobility  support  for  all  devices  and  application  services  but  rather  provide  mobility  on
                    demand only to those that need it.
            •       Support of services that have different latency requirements between the UE and the Data Network.
                    In IMT-2020 networks, gateways to a core network can be flexibly located closer to the cell sites,
                    which will bring a significant reduction on back haul and core network traffic (e.g., with placing
                    content servers closer to UE, services latency leads to be reduced). Furthermore, The IMT-2020
                    network should support services that have different end-to-end QoS (data rate, reliability, latency,
                    location accuracy etc.) requirements. There may be some latency critical applications while there
                    are others which are tolerant long end-to-end latency.
            •       Support of network slicing. An IMT-2020 network, as an integrated common core network, will be
                    flexible  enough  to  support  extremely  variety  of  requirements  in  user  devices  and  application
                    services.  Therefore,  the  IMT-2020  network  is  envisioned  as  a  network  where  multiple  logical
                    network  instances  tailored  to  various  requirements  can  be  created.  Network  slicing  allows  the
                    operator  to  provide  dedicated  logical  networks  (i.e.,  network  slices)  with  customer  specific
                    functionality.  The  architecture  shall  allow  different network configurations  in different  network
                    slices. A network slice can span all the domains of network, such as transport network supporting
                    flexible  locations of  functions,  dedicated  radio  configurations or  specific  RAT and  core  network
                    dedicated to different types of services. Different types of network slices can be composed of not
                    only  standardized  network  functions  but  also  some  proprietary  functions  that  are  provided  by
                    different operators or 3rd parties. Modular function design to enable flexible network slicing is
                    desirable (e.g., separation of mobility management (MM) and session management (SM) control
                    functions);



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