PLMN Mobility Management via Temporary Access Rejection
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Solution Overview
Problem
In the event of a failure in the first Public Land Mobile Network (PLMN) by the first operator, there is no established technical method for the second operator's network to provide seamless mobility management and service continuity for subscribers, especially for inbound roaming users who may not recognize the second PLMN as a roaming partner, leading to inefficient resource utilization and poor user experience.
Innovation Solution
A method where the second PLMN manages mobility by receiving access request messages from User Equipment (UE) and transmitting response messages that reject the access request initially, providing system information about the first PLMN, and later allowing access when conditions are met, ensuring temporary rejection messages inform the UE to reselect the first PLMN after a certain period, thus managing network resources and user expectations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second PLMN provides service to UE by accepting access requests, then service continuity is maintained, but network resource utilization becomes inefficient due to unnecessary load on the second PLMN
Solution Approach 1:
The second PLMN pre-configures rejection cause information indicating temporary rejection with a back-off timer value before receiving access requests. When a UE from a failed first PLMN attempts to access the second PLMN, the second PLMN immediately rejects the request with this pre-configured information, preventing unnecessary resource consumption while maintaining service continuity by guiding the UE to wait and retry on the original network.
Solution Approach 2:
The second PLMN provides feedback to the UE through the rejection message containing the back-off timer value, informing the UE to reselect the first PLMN after a specific period. This feedback mechanism enables the UE to adjust its access behavior, avoiding continuous access attempts to the second PLMN and reducing unnecessary network load while ensuring service continuity when the first PLMN recovers.
2Productivity
If the second PLMN rejects all access requests from UE, then network resources are protected, but user experience deteriorates due to lack of service availability
Solution Approach 1:
The rejection message from the second PLMN includes a dynamic back-off timer value that can be adjusted based on network conditions and failure duration. This dynamic parameter allows the UE to understand when to retry access, providing a balanced approach that protects network resources during failures while ensuring service becomes available again when the original network recovers, thereby maintaining good user experience.
3Ease of operation
If the second PLMN accepts access requests from UE, then user experience is improved, but system complexity increases due to need for failure detection and conditional access control
Solution Approach 1:
The complex failure detection and conditional access control logic is extracted from the second PLMN and placed in the UE. The second PLMN only needs to transmit system information indicating PLMN failure and provide pre-configured rejection cause information with back-off timer values. The UE independently determines whether to attempt access based on this information, significantly reducing the processing complexity on the network side while maintaining good user experience through intelligent UE behavior.
4Adaptability or versatility
If the second PLMN transmits system information about first PLMN, then UE can make informed access decisions, but information transmission overhead increases
Solution Approach 1:
The second PLMN transmits only the essential system information indicating PLMN failure and pre-configured rejection cause information with back-off timer values, rather than transmitting complete network status or all possible access control parameters. This partial information transmission provides sufficient data for the UE to make informed access decisions while minimizing information transmission overhead and avoiding unnecessary data burden on the air interface.
Data Source
AI summary
According to one disclosure of the present specification, provided is a method in a network node that manages mobility in a second public land mobile network (PLMN). According to the method, an access request message from a terminal may be received through a base station in the second PLMN. In addition, a response message to an access request of the terminal may be transmitted. The response message may include information indicating rejection to the access request of the terminal, on the basis of the terminal that joined a third PLMN and on the basis of the base station that transmitted system information including information about a first PLMN on behalf of a base station of the first PLMN.