Aperiodic CQI Triggering for Selective Component Carrier Feedback
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Solution Overview
Problem
In LTE-A systems with carrier aggregation, existing methods for triggering channel quality feedback (CQI) result in inefficient use of downlink control signaling overhead and uplink resources due to the need for multiple UL-DCI messages for each component carrier, lacking flexibility in selecting which carriers to request feedback from.
Innovation Solution
A mechanism is introduced where a CQI request flag in dedicated control information is used in conjunction with additional bits to indicate which component carriers require channel quality feedback, allowing flexible interpretation based on the status of the CQI request flag and other control information fields, such as hopping flags, resource assignment, and carrier indicators, to optimize signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If multiple UL-DCI messages are used to trigger CQI feedback for each component carrier, then channel quality feedback can be obtained for all carriers, but downlink control signaling overhead increases
Solution Approach 1:
The patent combines multiple CQI trigger indications into a single UL-DCI message by using a bitmap field where each bit corresponds to a specific component carrier. This merging approach allows the network to trigger CQI feedback for multiple component carriers simultaneously using one downlink control signaling message, thereby reducing the total number of UL-DCI messages required while maintaining complete channel quality feedback coverage across all aggregated carriers.
2Loss of information
If CQI feedback is requested for all component carriers, then comprehensive channel quality information is available, but uplink resources are wasted when not all carriers need feedback
Solution Approach 1:
The patent enables selective CQI feedback triggering on a per-component-carrier basis using the bitmap field in the UL-DCI message. Each bit in the bitmap can be independently set to indicate whether CQI feedback is required for the corresponding component carrier. This local quality approach allows the network to request feedback only for specific carriers where it is currently needed, optimizing uplink resource usage by avoiding unnecessary feedback transmissions while ensuring comprehensive coverage when required.
3Stability of the object's composition
If existing CQI triggering mechanisms are used in LTE-A with carrier aggregation, then backward compatibility is maintained, but flexibility in selecting which carriers to request feedback from is limited
Solution Approach 1:
The patent enhances the existing UL-DCI message format by incorporating a bitmap field that can indicate component carriers in a flexible manner. This modification maintains backward compatibility with existing LTE systems while adding multi-functionality to the control signaling mechanism. The bitmap field can be configured to trigger CQI feedback for any combination of component carriers, providing adaptability and versatility in carrier selection while preserving the original message structure and interpretation for legacy systems.
Data Source
AI summary
The invention relates methods for triggering channel quality feedback for at least one of plural component carriers of a communication system available for downlink transmission. The invention suggests a mechanism for triggering channel quality feedback from a terminal where the downlink control signaling overhead for the selection of component carrier(s) to be reported on is minimized. One aspect of the invention is a new interpretation of a predetermined format for dedicated control information comprising a CQI request flag, which is depending on the status of the CQI request flag. In case the CQI request flag is set at least one further bit of the dedicated control information is interpreted as information indicative of the one or more component carriers available for downlink transmission to the terminal and the terminal is providing channel quality feedback on the channel quality experienced on the indicated component carrier or component carriers.