Secondary Cell Handover in Inter-eNB Carrier Aggregation
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Solution Overview
Problem
In radio communication systems using Inter-eNB CA, there is a challenge in maintaining continuous communication services when a UE changes the secondary cell from one low-power base station to another, as existing methods require releasing and reconfiguring information, leading to disruption of communication services in the original low-power base station cell.
Innovation Solution
The system allows for seamless handover of secondary cells by keeping communication status information on the original cell during the change, enabling the radio terminal and network to resume communication services on the new cell without interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the UE changes the secondary cell from one low-power base station to another using existing methods, then the handover can be completed, but the communication service in the original low-power base station cell is disrupted and requires releasing and reconfiguring information
Solution Approach 1:
The network side performs preliminary actions by establishing forwarding bearers and transferring communication status information (such as PDCP sequence numbers and buffer status) from the source low-power base station to the target low-power base station before the UE actually switches cells. This preliminary setup ensures that when the handover occurs, the communication service can continue without disruption.
Solution Approach 2:
The macro base station acts as an intermediary between the source and target low-power base stations during the handover process. It coordinates the establishment of forwarding bearers and facilitates the transfer of communication status information, enabling seamless service continuity across different base stations.
2Adaptability or versatility
If the UE releases and reconfigures information when changing secondary cells, then the new cell can be properly configured, but the communication service experiences interruption
Solution Approach 1:
The system maintains continuity of useful action by establishing forwarding bearers that allow data transmission to continue uninterrupted during the handover process. The communication status information is transferred and maintained, ensuring that the data transmission function continues without break, even as the UE switches from one low-power base station to another.
Solution Approach 2:
The forwarding bearers and communication status information are set up in advance before the UE releases the old cell configuration. This preliminary setup allows the reconfiguration process to occur without causing service interruption, as the new configuration is already prepared and ready to take over immediately.
3Reliability
If the system maintains communication status information during secondary cell change, then service continuity is achieved, but the system complexity increases
Solution Approach 1:
The macro base station serves as an intermediary that centralizes the management of communication status information during handovers. Instead of each low-power base station independently managing complex information transfer, the macro base station coordinates and facilitates this process, reducing the overall system complexity while maintaining service continuity.
Solution Approach 2:
The system creates copies of the communication status information (such as PDCP sequence numbers and buffer status) and transfers them from the source to the target low-power base station. This copying approach simplifies the information management process compared to attempting to maintain single-source truth across distributed base stations, as each base station can work with its local copy.
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 secondary cell form the second cell (20) to a third cell (30) while keeping communication status information regarding the radio terminal (4) on the second cell (20). It is thus, for example, possible to enable a communication service in the secondary cell to be continued after the secondary cell is changed when the radio terminal which is simultaneously using a plurality of cells served by different radio stations changes the secondary cell from a cell of one radio station to a cell of another radio station.