Handover Cell List Configuration in Multi-Carrier Systems
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Solution Overview
Problem
In multiple component carrier systems, handover procedures are challenging due to the difficulty in accurately determining the quality of service provided by target base stations, which can lead to inadequate configuration of component carriers, resulting in potential call disconnections during user equipment movement between cells.
Innovation Solution
A method and apparatus where the source base station configures a candidate cell list, an aggregatable cell list, and a list of sensible cells based on user equipment measurements, and requests handover to a target base station, ensuring that the user equipment can select appropriate component carriers for seamless handover, including a measurement report message, handover request message, and handover command message to facilitate smooth transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target base station configures component carriers based on limited information, then the handover procedure is simple and fast, but the quality of service cannot be accurately determined leading to inadequate component carrier configuration
Solution Approach 1:
The source base station performs preliminary actions by configuring candidate cell lists, aggregatable cell lists, and sensible cell lists before handover. These lists contain pre-evaluated cell information that will be transferred to the target base station, eliminating the need for the target to perform complex quality of service determination from scratch.
Solution Approach 2:
The source base station acts as an intermediary that collects cell measurement information from the user equipment, evaluates candidate cells, and prepares comprehensive cell lists. This intermediary role transfers accurate cell information to the target base station without requiring the target to directly interact with the user equipment for measurements.
2Productivity
If multiple component carriers are configured for handover, then the transmission capacity is maintained, but the power consumption increases
Solution Approach 1:
The system applies local quality by configuring component carriers selectively based on cell-specific conditions. The source base station evaluates each candidate cell's suitability and includes only appropriate component carriers in the handover command, rather than uniformly configuring all carriers for all handovers.
Solution Approach 2:
The system uses partial action by configuring only the necessary subset of component carriers for each specific handover scenario. The candidate cell lists allow the target base station to select only those carriers needed for maintaining transmission capacity, avoiding unnecessary carrier configurations that would increase power consumption.
3Measurement precision
If the target base station determines cell configuration independently, then the handover decision is fast, but the component carrier configuration may be inadequate
Solution Approach 1:
The source base station performs preliminary cell evaluation and configuration work before handover by creating candidate cell lists with detailed cell information. This preliminary action ensures high measurement precision for cell evaluation while reducing the time needed at the target base station, as the heavy evaluation work is already completed.
Solution Approach 2:
The system implements feedback by having the user equipment provide measurement reports to the source base station, which then uses this feedback information to evaluate and rank candidate cells. The measured cell qualities are fed back into the candidate cell list configuration, ensuring accurate cell evaluation based on actual signal conditions.
Data Source
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AI summary
A method for performing handover in a multiple component carrier system includes a UE transmitting a measurement report message, including measurement values for one or more cells, to a source BS, the source BS transmitting a handover request message, including at least one of a candidate cell list including at least one candidate cell to be used in a target BS, an aggregatable cell list including at least one aggregatable cell in which UE capability is taken into consideration, and a list of sensible cells including at least one cell defined based on a similarity sensitivity of a measured frequency, to the target BS based on the measurement value, the source BS checking the cell included in the at least one list, receiving a handover ACK message including a final cell from the target BS, and determining handover, and the source BS transmitting a handover command message to the UE.