Sub-band CQI Reporting via Range and Resolution Indicator
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Solution Overview
Problem
In next-generation wireless communication systems like 5G NR, there is a challenge in accurately reporting sub-band Channel Quality Indicators (CQI) due to variations in channel quality and interference, which limits the network's ability to select optimal Modulation and Coding Schemes (MCS) for Ultra-Reliable Low-Latency Communications (URLLC), especially when sub-band CQI may be lower than wide-band CQI despite similar quality across all Physical Resource Blocks (PRBs).
Innovation Solution
Introducing a Range and Resolution Indicator (RRI) that improves sub-band CQI reporting by determining sub-band differential CQI values relative to wide-band CQI, allowing for more precise MCS selection through enhanced sub-band CQI mapping tables and increased reporting bits, such as using 3 or 4 bits for sub-band CQI, and optionally using a common RRI for all sub-bands or individual RRIs for each sub-band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If sub-band CQI reporting uses limited bits (2 bits), then reporting overhead is reduced, but measurement precision and MCS selection accuracy deteriorate
Solution Approach 1:
The patent segments the CQI reporting into wide-band CQI (WB-CQI) and sub-band differential CQI (SB-CQI). The WB-CQI provides the base quality metric for the entire bandwidth, while the SB-CQI provides differential adjustments for specific sub-bands. This segmentation allows the system to capture both overall and local channel quality variations without requiring full precision for every sub-band, thus reducing overhead while maintaining accuracy.
Solution Approach 2:
The patent changes the parameter representation from absolute CQI values for each sub-band to differential values relative to the wide-band CQI. By using differential encoding, the patent exploits the statistical correlation between wide-band and sub-band qualities, allowing most sub-bands to be represented with fewer bits since their differential values tend to be small. This parameter transformation reduces the information loss while maintaining measurement precision.
2Measurement precision
If sub-band CQI reporting uses more bits (3 or 4 bits), then measurement precision and MCS selection accuracy improve, but reporting overhead and device complexity increase
Solution Approach 1:
The patent divides the CQI reporting task into two segments: wide-band CQI determination and sub-band differential CQI determination. The UE first determines the WB-CQI for the entire bandwidth, then determines differential values for each sub-band relative to the WB-CQI. This segmentation allows the system to achieve high precision for sub-band quality assessment while keeping the processing complexity manageable by reusing the WB-CQI calculation results.
Solution Approach 2:
The patent performs preliminary action by first determining the wide-band CQI before determining sub-band differential CQI values. The WB-CQI serves as a reference that is calculated once and then used as the basis for all sub-band differential calculations. This preliminary action reduces the overall processing complexity because the UE doesn't need to independently calculate absolute CQI for each sub-band, but rather only needs to calculate the differential adjustment from the pre-computed WB-CQI.
3Productivity
If sub-band CQI values are used for MCS selection, then spectral efficiency improves, but reliability deteriorates when sub-band CQI is lower than wide-band CQI despite similar quality across all PRBs
Solution Approach 1:
The patent applies local quality by allowing different CQI values for different sub-bands when actually channel conditions vary locally. However, it also provides a safeguard mechanism where the network can choose to use WB-CQI instead of SB-CQI for MCS selection when sub-band values appear anomalously low. This approach enables the system to exploit local quality variations for spectral efficiency improvement while maintaining reliability by having a fallback to the more robust wide-band measurement.
Solution Approach 2:
The patent implements feedback by reporting sub-band differential CQI values to the network, enabling the gNB to observe the relationship between WB-CQI and SB-CQI over time. Through this feedback mechanism, the network can learn when sub-band measurements are reliable and when they might be anomalously low despite similar actual quality across PRBs. This feedback allows the network to adaptively choose between using SB-CQI for spectral efficiency or WB-CQI for reliability based on observed patterns.
Data Source
AI summary
The present disclosure provides a method performed by a wireless communication device. The method comprises: determining at least one range and/or resolution indicator, RRI, for sub-band Channel Quality Indicator, CQI, based on sub-band CQI values for two or more sub-bands; determining sub-band differential CQI values for the sub-band CQI values relative to a wide-band CQI value based on the determined RRI; and transmitting the determined at least one RRI for sub-band CQI and the determined sub-band differential CQI values to a network node.