3GPP SA2 Architecture and Functions of 5G System

3GPP SA2 Architecture and Functions of 5G System Junseok Kim†, Dongmyung Kim‡, and Sunghyun Choi† †Department

of ECE and INMC, Seoul National University, Seoul, South Korea, Network Lab., SK Telecom, Seongnam, South Korea

‡Access

Introduction  Service and System Aspects working group 2 (SA2) in 3GPP  Define architecture and main functions of network  Finalize 1st phase of 5G System (5GS) in Jun. 2018  Based on TS 23.501 [1]

 Protocol Data Unit (PDU) session for 5GS  PDU session: logical connection between UE and RAN

Architecture for 5GS

• Various PDU type: IPv4, IPv6, Ethernet, etc.

AMF: Access and Mobility management Function

 Establish PDU session when service is needed

SMF: Session Management Function AUSF: Authentication Server Function

• Independent of attachment procedure

UPF: User Plane Function UDM: User Data Management

 Support multiple PDU sessions to same data network or

PCF: Policy Control Function NRF: NF Repository Function

different data networks

AF: Application Function

 Encapsulation header: have different QoS classes • QoS flow (no bearer in 5GC) • Radio bearer: QoS flow = 1:n  Service Data Adaption Protocol (SDAP)

 Converged 5G Core network (5GC)  RAN: base station using New Radio (NR) and evolved LTE  AN: general base station including non-3GPP access

 Consists of various Network Functions (NFs)  Control plane: AMF, SMF, AUSF, and etc.  User plane: UPF

 Service-based architecture for control plane functions  Software and cloud-friendly network structure

 Network slicing

• Use HTTP/2

 Customized network service

Functions for 5GS

 Select control plane and user plane NFs required for specific service

RRC IDLE

RRC INACTIVE

RRC CONNECTED

Conclusion  5GS architecture  Modularize NFs  make network flexible and scalable

 Radio Resource Control (RRC) INACTIVE state  Primary sleeping state prior to RRC IDLE state

 Develop new state model and session management  Introduce new technology such as network slicing

 UE and RAN: keep context information for RRC connection  Keep connection between RAN and 5GC for UE in RRC INACTIVE state  Enable lightweight transition from inactive to active state

References [1] 3GPP TS 23.501, “System architecture for the 5G system,” ver.15.2.0, Jun. 2018. [2] J. Kim, D. Kim, and S. Choi, “3GPP SA2 architecture and functions for 5G mobile communication system,” ICT Express, vol. 3, pp. 1–8, 2017.