Variable Sub-band CQI Reporting for LTE-Advanced Uplink Overhead
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Solution Overview
Problem
Existing LTE-Advanced systems face challenges in designing a channel quality indication (CQI) scheme that maintains a constant CQI word size while supporting bandwidths up to 100 MHz with multiple component carriers, requiring efficient frequency domain link adaptation and scheduling with minimal uplink signaling overhead.
Innovation Solution
The system monitors component carriers by referring to sub-bands with variable sub-band sizes, identifying the best component carriers based on channel quality and adjusting the sub-band size accordingly, allowing for a constant CQI word size by increasing the sub-band size in proportion to the number of best component carriers, and sending detailed CQI reports to the eNode-B.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the system supports bandwidths up to 100 MHz with multiple component carriers, then the system capacity and bandwidth are improved, but the uplink CQI signaling overhead increases
Solution Approach 1:
The patent extracts and reports CQI information only for the 'best' component carriers (those with channel quality above a threshold) rather than all component carriers. This selective extraction reduces the amount of CQI signaling overhead while maintaining sufficient information for link adaptation in multi-carrier LTE-Advanced systems with up to 100 MHz bandwidth
Solution Approach 2:
The patent applies different CQI reporting strategies to different component carriers based on their local channel quality characteristics. Best component carriers with high channel quality are reported with detailed sub-band CQI information, while other carriers use wideband CQI or are excluded from reporting, optimizing the overall signaling overhead
2Measurement precision
If detailed CQI reports are sent for all component carriers, then the measurement precision is improved, but the CQI word size and signaling overhead increase
Solution Approach 1:
The patent applies different levels of measurement precision to different component carriers. For best component carriers, detailed sub-band CQI measurements are reported to achieve high measurement precision. For other carriers, wideband CQI or no reporting is used, reducing the overall CQI word size while maintaining sufficient precision where needed
Solution Approach 2:
The patent applies partial action by reporting detailed CQI information only for the necessary subset of best component carriers rather than all carriers. This partial reporting provides sufficient measurement precision for effective link adaptation while keeping the CQI word size manageable
Data Source
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AI summary
According to several embodiments of the present invention, an apparatus (e.g., a UE) monitors a set of component carriers by referring to sub-bands having a sub-band size. The channel quality of the component carriers is detected, best component carriers are identified based on the channel quality, the number of the best component carriers is identified, and the subband size is varied based the identified number of the best component carriers. Identification information and channel quality information on the best component carriers may then be provided, for example to a network control element such as an eNode-B.