Terminal Device Cell Registration for Network Slice Availability
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Solution Overview
Problem
In 5G networks, terminal devices cannot normally perform subsequent operations, such as PDU session establishment, when the cell they are registered in becomes unavailable, due to issues with network slice authentication or service type mismatches in registration accept messages.
Innovation Solution
The terminal device reselects a cell and initiates a registration procedure to obtain a normal service by determining the unavailability of the current cell and sending a second registration request to another cell, ensuring it can establish a PDU session on a suitable network slice.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal device is registered in a cell with network slice authentication failure or service type mismatch, then the terminal device can be registered in the cell, but the terminal device cannot normally perform subsequent operations such as PDU session establishment
Solution Approach 1:
The terminal device performs preliminary detection by checking whether the registration accept message contains allowed NSSAI or configured NSSAI information before attempting subsequent operations. This preliminary check allows the device to identify registration failures due to network slice authentication issues or service type mismatches, and trigger a cell reselection procedure in advance, preventing wasted attempts at PDU session establishment in unavailable cells.
2Stability of the object's composition
If the terminal device continues to operate in an unavailable cell, then the terminal device maintains its registered state, but service disruption occurs
Solution Approach 1:
The terminal device uses feedback from the registration accept message (presence or absence of allowed NSSAI/configured NSSAI) to determine cell availability. When the message lacks these information elements, the device feedback-induces a cell reselection procedure. This feedback mechanism ensures the terminal transitions from a stable but non-functional registered state to an active service state by selecting a new cell that can provide required network slice services.
Data Source
Figure 1~1A
Figure 2
Figure 2A~2C
AI summary
This application provides a registration method in a cell and a terminal, and relates to the field of communications technologies, to resolve a problem that a terminal cannot normally perform subsequent steps when a cell in which the terminal is currently successfully registered is unavailable. The method includes: sending, by a terminal device, a first request, where the first request is used to request to register in a first cell; receiving a first message, where the first message is used to indicate that the terminal device is successfully registered in the first cell; when the first message does not carry a first network slice identifier, or when the first message carries a first network slice identifier and the terminal device cannot establish a PDU session on a first network slice corresponding to the first network slice identifier, sending, by the terminal device, a second request, where the second request is used to request to register in a second cell, and the second cell is different from the first cell; receiving a second message, where the second message carries a second network slice identifier; and establishing, by the terminal device, the PDU session on a second network slice corresponding to the second network slice identifier.