CSI Request Field Segmentation for Carrier Aggregation Overhead
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Solution Overview
Problem
LTE-Advanced carrier aggregation systems face challenges in efficiently triggering and reporting aperiodic channel state information (CSI) due to the complexity introduced by multiple component carriers, leading to increased overhead and feedback delay in existing mechanisms.
Innovation Solution
A method involving pre-assigning a corresponding relationship between bits of the CSI request field in uplink grants and multiple downlink component carriers, allowing for efficient triggering and reporting of aperiodic CSI by determining and marking the appropriate DL CCs for reporting, thereby reducing overhead and delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single bit in DCI format 0 is used to trigger aperiodic CSI reporting as in LTE, then the DCI format size remains small, but the mechanism becomes unsuitable for LTE-Advanced systems with multiple component carriers
Solution Approach 1:
The patent segments the CSI request field into multiple bits, where each bit corresponds to a specific downlink component carrier. This allows independent triggering of aperiodic CSI reporting for each DL CC while maintaining a compact DCI format structure. The segmentation enables the system to handle multiple carriers without requiring a completely new DCI format.
Solution Approach 2:
The patent extends the triggering mechanism from a single-bit dimension to a multi-bit dimension, where additional bits are added to the DCI format 0 to accommodate multiple DL CCs. This dimensional extension allows the system to maintain backward compatibility with LTE while adapting to LTE-Advanced carrier aggregation requirements.
2Reliability
If multiple uplink grants are sent to trigger aperiodic CSI reporting for multiple DL CCs, then each DL CC can be triggered individually, but the uplink grant overhead increases significantly
Solution Approach 1:
The patent merges the triggering function for multiple DL CCs into a single uplink grant by adding a CSI request field with multiple bits. Each bit in this field corresponds to a specific DL CC, allowing the eNB to trigger aperiodic CSI reporting for one or multiple DL CCs simultaneously through one uplink grant, thereby reducing uplink grant overhead while maintaining individual CC triggering capability.
Solution Approach 2:
The CSI request field in the uplink grant is designed to serve multiple functions: it can trigger aperiodic CSI reporting for a single DL CC, multiple DL CCs, or all configured DL CCs, depending on the bit pattern set by the eNB. This multi-functionality eliminates the need for separate uplink grants for different triggering scenarios.
3Device complexity
If a limited number of bits are used in the CSI request field, then the DCI format size is reduced, but the number of triggerable DL CCs is limited
Solution Approach 1:
The patent dynamically adjusts the number of bits in the CSI request field based on the system configuration and the number of activated DL CCs. By changing the parameter of the CSI request field length, the system can accommodate different numbers of DL CCs while keeping the DCI format size as small as possible for each specific scenario.
Data Source
AI summary
Embodiments of the present invention disclose triggering methods and apparatuses of aperiodic channel state information CSI and an aperiodic sounding reference signal SRS for a carrier aggregation system. The method comprises: (1) pre-assigning a corresponding relationship between bits of the CSI request field in an uplink grant and multiple downlink component carriers DL CCs of user equipment, wherein the number of bits of the CSI request field is greater than 1 and less than the maximum allowed number of DL CCs in the system; (2) determining the DL CC for which aperiodic CSI reporting is to be triggered; and (3) mapping the CSI request field in the uplink grant according to the pre-assigned corresponding relationship to mark the value of the bit corresponding to the determined DL CC as “trigger”.