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s1 interface 5g

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The "S1 interface" is a critical component in the architecture of 4G LTE (Long-Term Evolution) networks. However, when it comes to 5G NR (New Radio), the network architecture changes significantly, and the S1 interface as we know it from LTE evolves into different interfaces for 5G.

To provide a more technical overview:

S1 Interface in 4G LTE:

In LTE, the S1 interface is used to connect two main components:

  1. eNodeB (eNB): This is the base station in LTE networks responsible for radio transmission/reception to/from the user equipment (UE).
  2. Mobility Management Entity (MME): This is a core network entity responsible for control signaling, including authentication, mobility management, and more.

The S1 interface carries both user data (User Plane) and control/signaling information (Control Plane) between the eNodeB and the MME.

S1 Interface Evolution in 5G:

With the introduction of 5G NR, the network architecture was revamped to provide enhanced capabilities, including higher data rates, reduced latency, and support for diverse use-cases. Consequently, the interface concepts evolved as well.

In 5G, the architecture has a new set of interfaces. The direct counterpart to the S1 interface in LTE is not a singular interface in 5G but is rather segmented into multiple new interfaces:

  1. NG (Next Generation) Interfaces:
    • NG-AP (Next Generation - Application Protocol): This is the control plane interface between gNB (5G New Radio Base Station) and AMF (Access and Mobility Management Function). The gNB is the 5G base station equivalent to the LTE eNodeB.
    • NG-U (Next Generation - User Plane): This is the user plane interface between the gNB and UPF (User Plane Function). The UPF handles the user data forwarding.
  2. AMF (Access and Mobility Management Function): This plays a role similar to the MME in LTE, handling mobility and session management for the 5G network.
  3. UPF (User Plane Function): This function in the 5G core network is responsible for the user plane data handling, including packet routing, forwarding, and encapsulation/decapsulation.