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Hybrid Core Network – 4G Core to 5 G Core Interconnection

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The transition from 4G to 5G networks involves the interconnection between the core networks of these two generations. A hybrid core network is typically used during this transition period to ensure compatibility and seamless communication between 4G and 5G devices. Let's break down the technical aspects of the 4G to 5G core interconnection in a hybrid core network.

  1. Architecture Overview:
    • 4G Core Network (EPC): The 4G core network is based on the Evolved Packet Core (EPC) architecture, comprising elements such as the Mobility Management Entity (MME), Serving Gateway (SGW), Packet Data Network Gateway (PGW), and others.
    • 5G Core Network (5GC): The 5G core network introduces a new architecture with key elements like the Access and Mobility Management Function (AMF), Session Management Function (SMF), User Plane Function (UPF), and others.
  2. Dual Connectivity:
    • The hybrid core network enables what is known as dual connectivity, allowing a device to be connected to both 4G and 5G networks simultaneously. This ensures a smooth transition and backward compatibility for devices that support both generations.
  3. NG-RAN (New Radio Access Network) Integration:
    • The 5G radio access network (RAN) is called NR (New Radio), and it coexists with the 4G LTE RAN. The interconnection between the 4G and 5G cores involves integrating the NG-RAN, allowing the 5G NR and 4G LTE radio technologies to work together seamlessly.
  4. Dual Registration:
    • Devices capable of both 4G and 5G connectivity undergo a dual registration process. This involves registering with both the 4G EPC and the 5G core network simultaneously. The dual registration ensures that the device can use services from both networks based on factors such as coverage, network load, and device capabilities.
  5. Anchor Point and Data Routing:
    • The Serving Gateway (SGW) in the 4G EPC serves as an anchor point for the user plane. The user plane traffic is then routed to the User Plane Function (UPF) in the 5G core network. This enables the data to flow seamlessly between 4G and 5G networks.
  6. Interworking Function (IWF):
    • The Interworking Function plays a crucial role in the interconnection. It manages the translation and mapping of signaling and data between the 4G and 5G protocols, ensuring that messages exchanged between the 4G and 5G cores are correctly interpreted.
  7. Handover Procedures:
    • During a mobility event where a device moves from a 4G to a 5G coverage area or vice versa, handover procedures take place. The handover ensures continuity of the connection, and the mobility management entities in both the 4G and 5G cores coordinate to transfer the session seamlessly.
  8. Slice Management:
    • 5G introduces the concept of network slicing, allowing the creation of logical, isolated networks tailored for specific use cases. The hybrid core network must manage these slices and ensure that devices moving between 4G and 5G maintain their connectivity and service quality.
  9. Security Considerations:
    • Security measures are critical during the interconnection process. Both 4G and 5G networks need to authenticate and authorize devices properly. Additionally, encryption and integrity protection mechanisms must be applied to secure user data during transit between the 4G and 5G cores.

the hybrid core network for 4G to 5G interconnection involves a combination of dual connectivity, anchor point management, interworking functions, handover procedures, and security measures to ensure a seamless and secure transition between the two generations of mobile networks.