5G NR 网络架构和网元功能

不废话，先放名词解释：

gNB: node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC.

ng-eNB: node providing E-UTRA user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC.

NG-C: control plane interface between NG-RAN and 5GC.

NG-U: user plane interface between NG-RAN and 5GC.

NG-RAN node: either a gNB or an ng-eNB.

Xn: network interface between NG-RAN nodes.

然后请欣赏5G网元功能划分和网络架构：

各个模块功能描述如下：

（关注几点：1. gNB和ng-eNB的区别在于一个支持5G新空口一个支持LTE空口，都可以连入到5G核心网   2. AMF的功能更加类似于MME在LTE中地位 3. UPF的功能接近LTE中SGW+PGW的功能，只是UE IP地址的分配，交给了SMF去干）

The gNB and ng-eNB host the following functions:

-     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.

The AMF hosts the following main functions (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.

The UPF hosts the following main functions (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.

The Session Management function (SMF) hosts the following main functions (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.

别急，还没完，下边请欣赏基站的模块划分，你会发现仿佛回到了RNC-nodeB时代，只不过在某种程度上做了CU的控制面与用户面的分离：

gNB Central Unit (gNB-CU): a logical node hosting RRC, SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en-gNB that controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected with the gNB-DU.

gNB Distributed Unit (gNB-DU): a logical node hosting RLC, MAC and PHY layers of the gNB or en-gNB, and its operation is partly controlled by gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected with the gNB-CU.

editor: ZYB

2018/05

BeiJing