Terminal Device CSI Feedback Grouping Low-Speed Backhaul
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Solution Overview
Problem
In heterogeneous networks with low-speed backhaul, existing methods for sharing channel state information between macrocells and small cells face challenges due to delayed information exchange, making efficient CSI feedback difficult.
Innovation Solution
The terminal device employs a method to efficiently share channel state information across cells regardless of backhaul speed by grouping serving cells and prioritizing CSI reports, allowing timely transmission even in low-speed backhaul conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal device uses existing CSI feedback methods in heterogeneous networks with low-speed backhaul, then the system maintains compatibility with standard protocols, but the CSI exchange is delayed and feedback efficiency deteriorates
Solution Approach 1:
The patent segments the serving cells into multiple cell groups (first cell group and second cell group) with different backhaul characteristics. This allows independent CSI feedback handling for each group, enabling timely feedback for high-speed backhaul cells while managing low-speed backhaul cells separately, thus resolving the time loss issue without compromising overall reliability
Solution Approach 2:
The patent introduces a priority mechanism as an intermediary to manage CSI feedback transmission. By assigning priorities to different CSI reports based on cell group and report type, the system can selectively transmit critical CSI information first, ensuring reliable feedback for important cells even when backhaul speed is limited
2Loss of information
If the terminal device transmits periodic CSI for all serving cells simultaneously, then complete channel state information is obtained, but transmission conflicts occur and feedback efficiency decreases
Solution Approach 1:
The patent divides serving cells into multiple groups and further segments CSI reports within each group by type (e.g., wideband CSI, subband CSI). This segmentation enables selective transmission of high-priority CSI information while deferring lower-priority reports, maintaining information completeness over time while improving immediate feedback efficiency
Solution Approach 2:
The patent establishes priority rules in advance that classify different CSI reports and cell groups into priority levels before transmission conflicts occur. This preliminary prioritization allows the terminal device to automatically resolve transmission conflicts by transmitting high-priority CSI first, ensuring both completeness and efficiency without real-time complex decision-making
3Speed
If the terminal device prioritizes CSI transmission for high-speed backhaul cells, then timely feedback is achieved for those cells, but low-speed backhaul cells experience delayed or lost CSI feedback
Solution Approach 1:
The patent applies different feedback strategies to different cell groups based on their local characteristics. High-speed backhaul cells receive priority CSI feedback with faster transmission, while low-speed backhaul cells are managed with adjusted priorities and timing. This local quality approach ensures optimal feedback speed for each cell type while maintaining overall system reliability
Solution Approach 2:
The patent uses periodic CSI feedback mechanisms where lower-priority cells are systematically included in subsequent feedback rounds. This periodic inclusion ensures that even low-speed backhaul cells receive reliable CSI feedback over time, balancing speed optimization for high-priority cells with reliability maintenance for all cells
Data Source
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AI summary
A terminal device that uses a first serving cell group including a primary cell has a higher layer control information acquisition unit that configures a second serving cell group not including the primary cell, a channel state information generation unit that calculates respective pieces of periodic channel state information of serving cells, an uplink control information generation unit that generates uplink control information by dropping reports of the periodic channel state information other than one thereof in a case where the reports of plural serving cells in the first serving cell group collide with each other in one subframe and by dropping the reports of the periodic channel state information other than one thereof in a case where the reports of plural serving cells in the second serving cell group collide with each other in one subframe, and an uplink control information transmission unit that transmits an uplink subframe including the uplink control information. The channel state information is thereby efficiently shared regardless of a backhaul speed.