Inter-eNB Carrier Aggregation Handover Status Transfer
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Solution Overview
Problem
In radio communication systems employing carrier aggregation across multiple cells, particularly in Inter-eNB CA, the continuity of communication services in secondary cells is disrupted during handovers due to the lack of a mechanism to transfer communication status information to the target eNB, leading to service interruption when the primary cell changes.
Innovation Solution
The system configures radio terminals and networks to maintain communication status information on secondary cells during handovers, allowing seamless continuation of data communication services by keeping or resuming communication status and bearer configurations across cell changes, enabling inter-radio station carrier aggregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the UE performs handover by releasing SCell during inter-eNB CA, then the handover procedure can be simplified, but communication service continuity in the secondary cell is lost
Solution Approach 1:
The patent applies preliminary action by having the source eNB transfer communication status information about the SCell to the target eNB before the handover is completed. This advance preparation ensures that when the UE resumes connection, the target eNB already possesses the necessary context (bearer configurations, QoS parameters, etc.) to maintain service continuity without requiring the UE to release and re-establish the SCell connection.
Solution Approach 2:
The patent uses communication status information as an intermediary element that carries the state of the SCell connection from the source eNB to the target eNB. This intermediary data structure includes bearer configurations, QoS parameters, and other connection state information that mediates the handover process, allowing the target eNB to resume the SCell service without the UE needing to release it first.
2Reliability
If communication status information is transferred to target eNB, then service continuity is maintained, but additional information transfer mechanisms are required
Solution Approach 1:
The patent applies universality by utilizing the existing handover request message structure to carry the communication status information. Rather than creating a completely new information transfer mechanism, the invention extends the existing message to include additional fields for SCell status information, bearer configurations, and QoS parameters. This multi-functional approach allows the same message to serve both the handover control function and the service continuity preservation function.
3Device complexity
If SCell is released during handover, then resource management is simplified, but data communication integrity is disrupted
Solution Approach 1:
The patent applies discarding and recovering by temporarily discarding the SCell connection during the handover transition, then recovering it through the transfer of communication status information. The source eNB discards the SCell context locally but preserves it in the transferred information message. The target eNB then recovers the SCell service by reconfiguring bearers based on the received status information, thereby restoring data communication integrity without permanently losing the SCell resource.
Data Source
AI summary
A radio network (6) and a radio terminal (4) are configured to, when the radio terminal (4) is using a first cell (10) served by a first radio station (1) as a primary cell and a second cell (20) served by a second radio station (2) as a secondary cell, change the primary cell from the first cell (10) to a third cell (30) served by a third radio station (3) while keeping communication status information regarding the radio terminal (1) on the second cell (20). It is thus, for example, possible to enable a communication service in the secondary cell to be continued even after the primary cell is changed when the primary cell is changed during execution of carrier aggregation (e.g., Inter-eNB CA) on a plurality of cells served by different radio stations.