Читать книгу NG-RAN and 5G-NR - Frédéric Launay - Страница 15

The NG-RAN provides both NR and LTE radio access.

An NG-RAN node is either a gNB (5G base station), providing NR user plane and control plane services, or an ng-eNB (new generation 4G base station) providing the LTE/E-UTRAN services towards the UE (control plane and user plane).

The NG-RAN ensures the connection of mobiles and the reservation of radio resources between:

1 – the mobile and the ng-eNB base station on a single 4G carrier (LTE) or on several 4G frequency carriers (LTE-Advanced);

2 – the mobile and the gNB base station on one or more 5G frequency bands (5G-NR).

The gNBs and ng-eNBs are interconnected through the Xn interface. The gNBs and ng-eNBs are also connected, via NG interfaces, to the 5G core (5GC).

The NG interface is the point of reference between the NG-RAN and the 5G core network:

1 – the NG-C interface is the interface between the radio node and the AMF (Access and Mobility Management Function). It supports signaling via NG-AP (Next Generation Application Protocol);

2 – the NG-U interface is the interface between the radio node and the UPF (User Plane Function) for tunneling traffic (the IP packet) via GTP-U (GPRS Tunneling Protocol).

The UPF is configured by the SMF (Session Management Function) under the control of the AMF.

Figure 1.6. NG-RAN general architecture

The mobile exchanges data with the DN (Data Network) through logical connections called PDU (Protocol Data Unit) sessions. This logical connection is divided into two parts:

1 – the NG-RAN ensures the connection of the mobiles with the base station and interconnects the control plane and user plane (traffic) of the mobile UE with the core network;

2 – the 5G core network interconnects the NG-RAN, provides the interface to the DN, ensures the registration of mobiles, the monitoring of their mobility and the establishment of data sessions with the quality of the corresponding QoS (Quality of Service).