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N2 Control plane interface betw. RAN and core network in 5G → NG C

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The 5G New Radio (NR) system architecture is designed to enable a variety of new use cases and applications. It is designed to provide increased data rates, reduced latency, improved reliability, and greater scalability compared to previous generations of mobile networks. To achieve these goals, the 5G architecture consists of two main parts: the Radio Access Network (RAN) and the Core Network (CN). The RAN is responsible for the wireless transmission of data between the user equipment (UE) and the base station, while the CN is responsible for the management of user data, signaling, and connectivity.

The RAN and the CN are connected through the N2 Control Plane interface in 5G. This interface is responsible for carrying signaling messages between the RAN and the CN. In this article, we will discuss the N2 Control Plane interface in detail, including its functions, protocols, and architecture.

Functions of N2 Control Plane interface

The N2 Control Plane interface provides a variety of functions, including:

  1. Connection management: The N2 interface is responsible for establishing and maintaining the connection between the RAN and the CN.
  2. User plane configuration: The N2 interface is responsible for configuring the user plane between the RAN and the CN. This includes the allocation of radio resources, the selection of transport protocols, and the configuration of QoS parameters.
  3. Mobility management: The N2 interface is responsible for managing mobility-related functions, including handovers, cell reselection, and roaming.
  4. Session management: The N2 interface is responsible for managing sessions between the RAN and the CN. This includes the establishment, modification, and release of sessions.
  5. Signaling: The N2 interface is responsible for carrying signaling messages between the RAN and the CN. This includes the exchange of control messages for connection management, user plane configuration, mobility management, and session management.

Protocols used in N2 Control Plane interface

The N2 Control Plane interface uses a variety of protocols to support its functions. These protocols include:

  1. PDCP (Packet Data Convergence Protocol): The PDCP protocol is used to compress and decompress IP packets for transmission over the radio interface. It also provides encryption and integrity protection for user data.
  2. RRC (Radio Resource Control): The RRC protocol is used to establish and release radio connections, configure radio bearers, and manage mobility-related functions.
  3. NGAP (Next-Generation Application Protocol): The NGAP protocol is used to carry signaling messages between the RAN and the CN. It is based on the ASN.1 encoding scheme and provides support for a wide range of signaling functions.
  4. SDAP (Service Data Adaptation Protocol): The SDAP protocol is used to map QoS parameters to radio bearers and provide support for flow-based packet forwarding.

Architecture of N2 Control Plane interface

The N2 Control Plane interface is based on a client-server architecture. The RAN acts as the client, while the CN acts as the server. The RAN sends signaling messages to the CN using the NGAP protocol, while the CN sends signaling messages to the RAN using the same protocol. The NGAP protocol is designed to be flexible and scalable, allowing it to support a wide range of signaling functions.

The N2 interface is divided into two main parts: the UE-N2 interface and the gNB-N2 interface. The UE-N2 interface is used to carry signaling messages between the UE and the gNB, while the gNB-N2 interface is used to carry signaling messages between the gNB and the UPF (User Plane Function) in the CN.

Conclusion

The N2 Control Plane interface is an important component of the 5G architecture. It provides a variety of functions, including connection management, user plane configuration, mobility management, session management, and signaling. The N2 interface uses a variety of protocols, including PDCP, RRC, NGAP, and SDAP, to support its functions. The N2 interface is based on a client-server architecture, with the RAN acting as the client and the CN acting as the server. The N2 interface is divided into two main parts, the UE-N2 interface, and the gNB-N2 interface.

In summary, the N2 Control Plane interface is a crucial element of the 5G architecture, enabling seamless communication and management of user data and signaling between the RAN and the CN. Its flexibility and scalability make it suitable for a wide range of use cases and applications, making 5G a transformative technology that promises to revolutionize the way we live and work.