3GPP：TS 38.300 NR; 网络架构

5G的基站节点 NG-RAN node 分为两类：

• gNB: 5G基站；
• ng-eNB：非5G基站，LTE/E-UTRAN协议的基站。

---

• 5G基站和非5G基站之间通过Xn接口通信。
• 5G基站和非5G基站都是通过NG接口连接5G核心网。

功能划分

基站的功能：

• Functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (scheduling);
• IP header compression, encryption and integrity protection of data;
• Selection of an AMF at UE attachment when no routing to an AMF can be determined from the information provided by the UE;
• Routing of User Plane data towards UPF(s);
• Routing of Control Plane information towards AMF;
• Connection setup and release;
• Scheduling and transmission of paging messages;
• Scheduling and transmission of system broadcast information (originated from the AMF or O&M);
• Measurement and measurement reporting configuration for mobility and scheduling;
• Transport level packet marking in the uplink;
• Session Management;
• Support of Network Slicing;
• QoS Flow management and mapping to data radio bearers;
• Support of UEs in RRC_INACTIVE state;
• Distribution function for NAS messages;
• Radio access network sharing;
• Dual Connectivity;
• Tight interworking between NR and E-UTRA.

AMF（Access and Mobility Management Function）的功能(see 3GPP TS 23.501 [3])：

• NAS signalling termination;
• NAS signalling security;
• AS Security control;
• Inter CN node signalling for mobility between 3GPP access networks;
• Idle mode UE Reachability (including control and execution of paging retransmission);
• Registration Area management;
• Support of intra-system and inter-system mobility;
• Access Authentication;
• Access Authorization including check of roaming rights;
• Mobility management control (subscription and policies);
• Support of Network Slicing;
• SMF selection.

UPF（User Plane Function）的功能 (see 3GPP TS 23.501 [3])：

• Anchor point for Intra-/Inter-RAT mobility (when applicable);
• External PDU session point of interconnect to Data Network;
• Packet routing & forwarding;
• Packet inspection and User plane part of Policy rule enforcement;
• Traffic usage reporting;
• Uplink classifier to support routing traffic flows to a data network;
• Branching point to support multi-homed PDU session;
• QoS handling for user plane, e.g. packet filtering, gating, UL/DL rate enforcement;
• Uplink Traffic verification (SDF to QoS flow mapping);
• Downlink packet buffering and downlink data notification triggering.

SMF（Session Management function）的功能 (see 3GPP TS 23.501 [3]):

• Session Management;
• UE IP address allocation and management;
• Selection and control of UP function;
• Configures traffic steering at UPF to route traffic to proper destination;
• Control part of policy enforcement and QoS;
• Downlink Data Notification.

Multi-RAT Dual Connectivity(MR-DC)

NG-RAN 节点需要支持Multi-RAT Dual Connectivity，即UE可以通过RRC_CONNECTED 可以由两个调度器配置，当Backhaul非理想状态下，可以提供ng-eNB接入或者NR接入。