SeNB Bearer Management for Seamless MeNB Handover in Dual Connectivity
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Solution Overview
Problem
Existing Dual Connectivity (DC) technologies in 3GPP Release 12 require the release of the secondary base station (SeNB) during inter-MeNB handovers, which complicates the handover process and involves unnecessary data forwarding, whereas supporting handovers without SeNB change is being discussed in Release 13.
Innovation Solution
Implementing a method that uses existing X2 interface procedures and signaling messages to perform MeNB changes without releasing the SeNB, by sending a Secondary Node addition request message that specifies which bearers to keep at the SeNB and which to move to the new MeNB, allowing for seamless handovers while maintaining connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the secondary base station (SeNB) is released during inter-MeNB handovers as per existing DC technologies, then the handover process can be completed, but the complexity of the handover process increases and unnecessary data forwarding is required
Solution Approach 1:
The patent applies preliminary action by establishing the SeNB connection and configuring bearers before the handover occurs. The target MeNB sends a Secondary Node addition request message to the SeNB during handover preparation, pre-configuring the bearer distribution (which bearers to keep at SeNB vs. move to target MeNB) before the actual handover executes, thus avoiding post-handover reconfiguration and reducing complexity
Solution Approach 2:
The patent applies segmentation by dividing the bearer management into two distinct groups: bearers to be kept at the SeNB and bearers to be moved to the target MeNB. This segmentation is explicitly indicated in the Secondary Node addition request message, allowing the SeNB and target MeNB to independently manage their respective bearers without requiring complete re-establishment, thereby reducing handover complexity and unnecessary data forwarding
2Reliability
If the secondary base station (SeNB) is released during inter-MeNB handovers, then the handover can proceed, but unnecessary data forwarding operations are required
Solution Approach 1:
The patent eliminates unnecessary data forwarding by performing preliminary configuration of bearer distribution before handover. The target MeNB identifies which bearers should remain at the SeNB and which should be transferred to the target MeNB, and this information is conveyed to the SeNB in advance via the Secondary Node addition request message, allowing direct bearer routing without intermediate forwarding
Solution Approach 2:
The patent extracts only the necessary data forwarding operations by selectively identifying which bearers require transfer to the target MeNB. Instead of forwarding all bearer data, the system extracts and transfers only the specific bearers indicated in the Secondary Node addition request message, while other bearers maintain direct routing through the SeNB, thereby eliminating unnecessary data forwarding time
Data Source
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AI summary
A secondary base station (2) is configured to receive an SeNB addition request message from a second master base station (3) while providing a radio terminal (1) with a secondary cell group (SCG) for DC in cooperation with a first master base station. The SeNB addition request message indicates whether each of at least one bearer that has already been configured in the secondary base station (2) for DC with the first master base station (1) is to be kept at the secondary base station (2). It is thus, for example, possible to contribute to performing a procedure for changing a master base station in Dual Connectivity (DC) by using existing inter-base station interface procedures and inter-base station signaling messages.