CSI Measurement in eMTC Using Multiple Reference Subframes
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Solution Overview
Problem
In enhanced machine-type communication (eMTC) and narrowband Internet-of-Things (NB-IoT) systems, user equipment (UE) faces challenges in performing channel state information (CSI) measurements due to low signal-to-noise ratio (SNR), making it difficult to measure CSI using a single subframe.
Innovation Solution
The UE is indicated a set of CSI reference subframes for measurement, which can be spread across multiple frequencies during frequency hopping, and may omit older subframes to provide an updated CSI report, allowing CSI measurements to be performed using a portion of these subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a UE uses a single subframe for CSI measurement like regular UEs, then the measurement process is simple and fast, but the measurement accuracy is insufficient due to low SNR in eMTC/NB-IoT
Solution Approach 1:
The patent segments the CSI measurement process by dividing it into multiple reference subframes instead of using a single subframe. This allows the UE to accumulate channel state information across multiple time instances, improving measurement accuracy in low SNR conditions while managing complexity through structured segmentation of the measurement resources.
Solution Approach 2:
The patent introduces a time dimension to the CSI measurement by utilizing multiple reference subframes across different time instances. This transforms the measurement from a single-point-in-time assessment to a multi-temporal measurement, enabling better accuracy in low SNR environments by capturing channel variations over time.
2Reliability
If a UE measures CSI using multiple reference subframes, then measurement accuracy improves in low SNR conditions, but the measurement time and processing complexity increase
Solution Approach 1:
The patent applies preliminary action by having the network pre-configure the set of reference subframes and their indices before the actual CSI measurement takes place. This allows the UE to know in advance which subframes to measure, reducing processing time and enabling more efficient measurement execution while maintaining improved accuracy through multiple reference points.
3Loss of information
If a UE includes all measured subframes in the CSI report, then the CSI information is comprehensive, but the report becomes outdated when including older subframes
Solution Approach 1:
The patent extracts only the most relevant and recent subframe information for the CSI report while excluding older or less relevant subframes. This selective extraction ensures that the CSI report contains current and accurate channel state information without being diluted by outdated measurements, maintaining both information quality and currency.
Solution Approach 2:
The patent introduces dynamics to the CSI reporting by allowing the set of reference subframes to be flexible and adaptable. The network can dynamically adjust which subframes are included in the measurement set based on current channel conditions and requirements, ensuring that the CSI report remains current and relevant while maintaining completeness of necessary information.
Data Source
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AI summary
The present disclosure proposes indicating to the UE a set of CSI reference subframes that may be used in performing a CSI measurement. The set of CSI reference subframes may be measured over multiple frequencies when frequency hopping occurs. In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may receive information associated with a number of CSI reference subframes to use in performing CSI measurements in a narrowband communication. In addition, the apparatus may monitor subframes on at least two frequency channels including a PDCCH. Further, the apparatus may perform a CSI measurement across the at least two frequency channels based on the information associated with the number of CSI reference subframes.