Differential CQI Encoding for CoMP Signaling Overhead
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Solution Overview
Problem
In MIMO communication systems using Cooperative Multipoint (CoMP) transmission, the existing channel feedback mechanisms consume significant signaling resources due to the need to report multiple Channel Quality Indicators (CQIs, especially when the differences between these indicators are small, leading to inefficient use of uplink channels.
Innovation Solution
The proposed solution involves differentially encoding Channel Quality Indicators (CQIs) in a mobile communication terminal, where one CQI is used as a reference, and the differences between other CQIs are encoded, reducing the number of bits required for feedback, thereby minimizing signaling overhead without significant performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple CQIs are reported for each cell in CoMP transmission, then channel feedback quality is improved, but signaling overhead increases
Solution Approach 1:
The patent extracts only the essential feedback information by reporting one full CQI value and differential values for other cells. This selective extraction maintains channel feedback quality while significantly reducing the quantity of signaling data transmitted over the uplink channel.
Solution Approach 2:
Instead of reporting absolute CQI values for all cells, the patent inverts the approach by reporting one absolute CQI and only the differences (deltas) for other cells. This inversion reduces signaling overhead while preserving the ability to reconstruct all CQI values at the receiver.
2Quantity of substance
If differential encoding is applied to CQIs, then signaling overhead is reduced, but feedback information complexity increases
Solution Approach 1:
The patent changes the parameter representation from absolute CQI values to differential values (deltas). This parameter transformation reduces the number of bits required for transmission while the complexity is managed through systematic calculation of differences between reference and non-reference cell CQIs.
Data Source
AI summary
A method includes receiving in a mobile communication terminal signals from multiple cells that coordinate transmission of the signals with one another in a Cooperative Multipoint (CoMP) scheme. At least first and second Channel Quality Indicators (CQIs), for respective communication channels over which the signals are received, are calculated in the terminal based on the received signals. The second CQI is differentially encoded relative to the first CQI. Feedback information, including the first CQI and the differentially-encoded second CQI, is transmitted from the terminal.