Aperiodic CQI Trigger Mapping in Carrier Aggregation
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Solution Overview
Problem
In LTE-Advanced systems with carrier aggregation, existing methods for triggering aperiodic CQI/PMI/RI reports are inefficient due to high control signaling overhead and lack of flexibility, particularly when dealing with multiple downlink component carriers.
Innovation Solution
Implementing an implicit pre-defined pattern to map aperiodic report triggers to specific downlink component carriers within a group, using rules such as activation status or resource allocation, to determine which carrier requires the report, thereby reducing the need for additional signaling bits and improving scheduling flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a 1-bit CQI-request field is used to trigger aperiodic reports in carrier aggregation, then the control signaling overhead is reduced, but the ability to specify multiple downlink component carriers is lost
Solution Approach 1:
The downlink component carriers are divided into multiple groups, with each group associated with a specific uplink component carrier. The 1-bit CQI-request field triggers aperiodic reports for all carriers within a specific group rather than individual carriers, enabling multi-carrier triggering while maintaining low signaling overhead.
Solution Approach 2:
The 1-bit CQI-request field is given multi-functional capability by associating it with carrier groups. A single bit value can trigger reports for multiple carriers within a group, making the field universal for both single-carrier and multi-carrier aperiodic reporting scenarios.
2Adaptability or versatility
If separate aperiodic reporting configurations are provided for each downlink component carrier, then the flexibility and precision of reporting is improved, but the control signaling overhead increases significantly
Solution Approach 1:
Multiple downlink component carriers are merged into groups that share common uplink component carriers. A single aperiodic reporting configuration is applied to all carriers within a group, combining the configuration management of multiple carriers into one unified structure, thereby reducing overhead while maintaining group-level flexibility.
Solution Approach 2:
The patent introduces a new dimension of organization by grouping carriers based on their uplink association rather than treating each carrier independently. This dimensional shift from carrier-level to group-level configuration enables efficient resource management with reduced signaling.
3Productivity
If multiple uplink component carriers are configured for carrier aggregation, then the uplink capacity is increased, but the complexity of managing aperiodic report associations increases
Solution Approach 1:
The system uses the existing uplink component carrier to automatically identify and manage the associated downlink component carrier groups. The uplink carrier serves as a self-identifying key that the UE and eNodeB can use to determine which downlink carriers should receive aperiodic reports, eliminating the need for complex explicit association signaling.
Data Source
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AI summary
A user's downlink component carriers DL-CCs are divided into groups. An aperiodic CQI/PMI report is triggered by signaling (for example one bit). There is a pattern that maps the signaled trigger to a particular DL-CC within a group of DL-CCs that are configured for a user equipment UE, and that mapped particular DL-CC is determined to be the subject of the aperiodic report. In various embodiments the pattern is implicit and points to the DL-CC for which an aperiodic report has not been sent for more than a threshold time interval; or to the DL-CC for which resources have not been allocated for a periodic report; or to every DL-CC in the group that are activated for the user equipment. Examples are detailed for apparatus, method and computer program from the perspective of the network and from the perspective of the UE.