Restricted RAT Registration Handling With UE Reselection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The behavior of user equipment (UE) during registration on a restricted radio access technology (RAT) in mobile communications is undefined, necessitating a solution for handling procedures on restricted RATs.
Innovation Solution
UEs and networks can initiate or receive reject messages with causes indicating restricted RATs, allowing selection of alternative RATs or new public land mobile networks (PLMNs) to comply with network restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the network operator regulates the utilization of a particular access technology combination within a PLMN, then the network control and compliance with regulations is improved, but the behavior of UE during registration on restricted RAT becomes undefined and problematic
Solution Approach 1:
The network provides feedback to the UE through a reject message with a specific cause value indicating that the attempted RAT is restricted. This feedback mechanism allows the UE to understand why its registration attempt was rejected and guides it to select an alternative RAT, thereby defining clear UE behavior in response to network restrictions.
Solution Approach 2:
The reject message is segmented to include a specific cause value that identifies the restriction reason. This segmentation of information allows the UE to process the rejection reason and take appropriate action, making the overall system behavior well-defined despite the restriction.
2Loss of information
If the network transmits a reject message with a cause indicating restricted RAT, then the clarity of rejection reason is improved, but the complexity of the signaling procedure increases
Solution Approach 1:
The reject message structure is designed to be multi-functional, serving both as a general rejection indicator and as a specific cause communicator. By reusing the existing reject message framework and adding a cause value, the solution provides clear rejection reasons without creating an entirely new signaling procedure, thus balancing information clarity with procedural simplicity.
3Reliability
If the UE selects another RAT or new PLMN responsive to receiving a reject message, then the compliance with network restrictions is improved, but the time required for successful registration increases
Solution Approach 1:
The UE performs preliminary actions by maintaining a list of alternative RATs and PLMNs before the registration attempt fails. When a reject message with a restricted RAT cause is received, the UE can immediately switch to a pre-identified alternative without extensive searching, thus reducing the time penalty while ensuring compliance with network restrictions.
Solution Approach 2:
The UE autonomously handles the reselection process by itself selecting alternative RATs or PLMNs based on the reject message cause, without requiring additional network assistance or manual intervention. This self-service approach minimizes the time required for compliance while maintaining registration success.
Data Source
AI summary
Techniques pertaining to handling procedure performed on a restricted radio access technology (RAT) in mobile communications are described. An apparatus (e.g., a UE) initiates a procedure with a network. The apparatus then receives from the network, responsive to the initiating, a reject message with a cause indicating that a RAT attempted to be accessed by the apparatus is restricted. In response to receiving the reject message, the apparatus selects another RAT or a new public land mobile network (PLMN).