What is the purpose of the N3 interface between NG-RAN and 5GC?

The radio access network (RAN) in a mobile communication system must be connected to the core network through an interface and then interoperate with public communications and the Internet. After that, the mobile terminal (UE) can realize data and voice communication; this interface is N3 in 5G.

I. N3 interface It is the interface between NG RAN (radio access network) and 5GC (core network) in 5G (NR) system; the main function is to realize the exchange of user data and signaling messages between core network and radio access network.

Fig. 1.N3 interface location in 5G system

II.N3 uses mainly include the following;

• Data transmission:The N3 carries user-plane and control-plane traffic, where the user plane is responsible for transmitting user data, such as Internet traffic, voice calls, and multimedia content, between the user equipment and the 5G core network.
• Control signaling:In addition to user data, the N3 interface handles control signaling messages. These messages are critical for establishing, managing and releasing connections between user equipment (UE) and 5G core network functions.
• Interface Protocols:The N3 interface relies on a variety of protocols to communicate and ensure that the core network and RAN elements correctly transmit and interpret data and signaling messages.Common protocols used on the N3 interface include IP (Internet Protocol), SCTP (Stream Control Transmission Protocol), and other protocols specific to the 5G network architecture.
• Dynamic Connectivity:The N3 interface allows for dynamic and flexible connection management, a key feature of 5G networks. It supports seamless switching, Quality of Service (QoS) tuning, and efficient resource allocation to provide a superior user experience.
• Slicing Support:Network slicing is a fundamental concept in 5G that supports the creation of multiple virtual networks within a single physical infrastructure.The N3 interface plays a critical role in supporting network slicing by ensuring that traffic for each slice is properly routed and managed within the NG RAN.
• Scalability:The N3 interface is designed to handle large volumes of data traffic and signaling messages, making it suitable for a variety of 5G use cases, including: eMBB (enhanced mobile broadband), URLLC (ultra-reliable low-latency communication), and mMTC (massive machine type communication).

The N3 interface is a key component of the 5G (NR) system architecture, enabling high-performance communications between the 5G core network and the radio access network, and it is critical to take advantage of the benefits of 5G technology to bring it to the user (UE) and its applications.