MME CSG-Id List Deletion on Home Base Station Mode Transition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current 3GPP standards lack a method for the mobility management entity (MME) to discard the existing list of Closed Subscriber Group Identifiers (CSG-Ids) when a home base station (HNB) changes from a closed or hybrid access mode to an open access mode, as there is no way for the HNB to inform the MME to delete the CSG-Id list without sending a new list, leading to potential incorrect access control.
Innovation Solution
A communications node within the core network that processes a configuration message from the base station to determine if it has changed from a membership-based access mode to a non-membership-based access mode, and in response, deletes the stored list of membership identifiers, even if no list is included in the configuration message, ensuring accurate access control when the HNB operates in open mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the HNB sends a new list containing all current CSG-Ids to update the MME, then the MME can maintain accurate CSG-Id lists for closed or hybrid mode operation, but there is no way to inform the MME to discard the existing list when the HNB changes to open mode
Solution Approach 1:
Instead of requiring the HNB to explicitly send a deletion command or empty list to remove CSG-Ids, the invention inverts the approach: the HNB simply omits the CSG-Id list information element from the eNB Configuration Update message when transitioning to open mode. The MME, upon receiving the update message without this element, automatically discards the stored CSG-Id list. This inversion transforms a problematic requirement (how to delete) into a simple absence of information.
Solution Approach 2:
The invention extracts the CSG-Id list information element from the eNB Configuration Update message as an optional component. When the HNB operates in open mode, this element is simply not included in the message. The MME is designed to recognize the absence of this element as an instruction to discard the stored CSG-Id list, thereby separating the presence/absence of the element from the mandatory message structure.
2Adaptability or versatility
If the HNB operates in open mode without sending a CSG-Id list, then the HNB gains flexibility in access mode operation, but the MME cannot determine whether to keep or discard the existing CSG-Id list
Solution Approach 1:
The invention establishes a feedback mechanism where the MME monitors the presence or absence of the CSG-Id list information element in eNB Configuration Update messages. When the element is absent, the MME interprets this as feedback indicating the HNB has transitioned to open mode and should discard the CSG-Id list. This feedback loop ensures the MME maintains accurate information about the HNB's current access mode without requiring explicit status reports.
3Productivity
If the MME stores the CSG-Id list for future reference, then the MME can efficiently manage closed subscriber group access, but outdated lists cause incorrect access control when the HNB changes mode
Solution Approach 1:
The invention implements preliminary action by having the MME proactively discard the stored CSG-Id list as soon as it receives an eNB Configuration Update message without the CSG-Id list information element. This preliminary discarding action prevents the possibility of using outdated CSG-Id lists for access control decisions, ensuring that the MME always has current information before making access control determinations.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A communication system is described in which a base station operating in a hybrid or closed access mode requests deletion of the copy of the CSG-Id list maintained at the corresponding mobility management entity in the core network, when the base station changes its operation mode to an open (non-CSG) access mode.