AMF Always-On PDU Session Activation in 5G
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Solution Overview
Problem
In 5G wireless communication systems, always-on PDU sessions may be omitted from activation when a user equipment (UE) transitions to a connection management-connected state, leading to delayed data transmission and potential latency issues, particularly for services sensitive to data transmission latency like URLLC.
Innovation Solution
The proposed solution involves the Access and Mobility Management Function (AMF) and Session Management Function (SMF) collaborating to ensure always-on PDU session activation by transferring an always-on indication between them, storing this indication in UE context, and identifying omitted PDU sessions during registration and service requests, thereby preventing user plane resource omission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the UE includes only necessary PDU sessions in the activation list during state transition, then signaling overhead is reduced, but always-on PDU sessions may be omitted leading to latency issues
Solution Approach 1:
The network pre-configures always-on PDU sessions with an activation flag before the UE transitions to connected state. When the AMF receives the service request, it checks this pre-configured flag to automatically activate the user plane for always-on sessions without requiring explicit inclusion in the activation list, thus preventing omission while maintaining signaling efficiency.
Solution Approach 2:
The AMF implements a feedback mechanism where it compares the received activation list against the UE's configured always-on PDU sessions. When an always-on session is detected as omitted, the AMF sends a supplementary activation request to the SMF to ensure the user plane is activated, providing corrective feedback to prevent latency issues.
2Reliability
If the UE activates all PDU sessions upon connection, then no sessions are omitted and data transmission is immediate, but signaling overhead and processing complexity increase
Solution Approach 1:
PDU sessions are segmented into two categories: regular sessions and always-on sessions. This segmentation allows the system to apply different activation strategies - regular sessions follow the standard activation list approach while always-on sessions have a dedicated activation mechanism based on pre-configured flags, reducing overall management complexity while ensuring reliable activation of critical sessions.
Solution Approach 2:
Different activation behaviors are applied to different PDU sessions based on their local quality requirements. Always-on PDU sessions, which have strict latency requirements, receive special treatment with pre-configured activation flags and supplementary activation mechanisms, while other sessions use the standard activation process, optimizing the system for critical services without unnecessarily complicating overall session management.
3Reliability
If the network monitors and corrects omitted always-on PDU sessions, then activation reliability is improved, but additional signaling messages are required
Solution Approach 1:
The network performs preliminary configuration of always-on PDU sessions with activation flags during session establishment. This preliminary action enables the AMF to proactively identify and activate always-on sessions without requiring reactive monitoring and correction messages, thereby improving activation reliability while minimizing additional signaling overhead.
Data Source
AI summary
Disclosed is a 5th generation (5G) or pre-5G communication system for supporting a data transmission rate higher than that of a 4th generation (4G) communication system such as long term evolution (LTE). According to various embodiments of the disclosure, provided is a method for operating an access and mobility management function (AMF) in a wireless communication system, comprising the steps of: receiving, from user equipment (UE), a service request including a list of protocol data unit (PDU) sessions to be activated, or a message about a mobility registration update; checking, on the basis of UE context information about the UE, whether identifiers (IDs) of all of always-on PDU sessions are included in the list of PDU sessions to be activated; and, when an omitted always-on PDU session is checked from the list of the PDU sessions to be activated, transmitting, to a session management function (SMF), a Nsmf_PDUSession_UpdateSMContext request message for requesting user plane activation of the omitted always-on PDU session.