Establishment of a PDU Session in 5G/NR involves a structured multi-step process to facilitate communication between the User Equipment (UE) and the network's Data Network (DN) through the 5G Core (5GC). This ensures that the UE can access services such as internet and Voice over New Radio (VoNR). Below are the key steps involved:
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PDU Session Establishment Request: The process starts with the UE requesting a PDU session establishment and this request is usually triggered either by the UE.
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Initial Registration: The UE undergoes initial registration with the 5G network for authentication and to establish a secure connection, involving the Access and Mobility Management Function (AMF) and the Authentication Server Function (AUSF).
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Session Management Function (SMF) Selection: The AMF selects a suitable SMF for session management based on the UE's subscription data and session requirements.
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Session Establishment: The selected SMF initiates the session establishment, setting up the user plane with the User Plane Function (UPF) for routing and forwarding the session's data packets.
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Allocation of Network Resources: Necessary network resources and an IP address for the UE are allocated, with the SMF coordinating with the UPF for resource allocation and routing paths establishment.
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PDU Session Establishment Acceptance: The UE is notified through a message from the SMF, via the AMF, that the PDU session has been successfully established.
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Data Transfer: With the PDU session established, the UE can start transferring data packets with the DN via the 5G Core network, with the UPF managing routing and forwarding.
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Session Management and Modification: The SMF manages and modifies the session as needed, adjusting QoS parameters, reallocating resources, or handling mobility events.
This process is defined by the 3rd Generation Partnership Project (3GPP) standards, ensuring interoperability, security, and efficiency across different network vendors and configurations.