User Terminal CSI Measurement Using Early Reference Subframes
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Solution Overview
Problem
Existing LTE systems face challenges in reducing communication latency and processing time, which hinders the implementation of shortened transmission time intervals (TTIs) and reduced processing times, potentially leading to deterioration in communication quality, throughput, and spectral efficiency.
Innovation Solution
A user terminal that measures and transmits channel state information (CSI) using a CSI reference resource found in a subframe located a shorter period before the given subframe, allowing for appropriate CSI measurements and reporting even with shortened TTIs and processing times, and configuring processing time reduction for earlier signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If shortened transmission time interval (TTI) and reduced processing time are implemented, then latency is reduced and system throughput is improved, but communication quality deteriorates and measurement precision of channel state information decreases
Solution Approach 1:
The patent applies preliminary action by having the user terminal measure channel state information in advance using a CSI reference resource located in a subframe before the given subframe. This allows the measurement to be completed beforehand, providing time for processing while still delivering timely CSI reports. The measurement is performed on a CSI reference resource that is positioned earlier in time, enabling the system to reduce latency without sacrificing measurement accuracy.
2Productivity
If shortened transmission time interval (TTI) is implemented, then the number of users per unit time increases and productivity improves, but device complexity increases and system reliability decreases
Solution Approach 1:
The patent applies preliminary action by positioning the CSI reference resource in an earlier subframe, allowing the user terminal to complete measurements before the current transmission time interval. This advance measurement provides a buffer that maintains reliability even with shortened TTIs, ensuring that accurate CSI is available for scheduling decisions without compromising communication quality.
3Speed
If processing time is reduced, then latency is reduced and speed increases, but the accuracy of channel state information reporting decreases
Solution Approach 1:
The patent applies preliminary action by having the user terminal perform CSI measurements in advance using a reference resource located in a previous subframe. This early measurement provides sufficient processing time for the network to receive and utilize the CSI information, maintaining accuracy while enabling faster overall processing and reduced latency.
Data Source
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Figure 3A~3B
AI summary
The present invention is designed to support appropriate CSI measurements and reporting even when shortened TTIs and/or processing time reduction are introduced. A user terminal according to one aspect of the present invention communicates in a cell, which uses a shortened transmission time interval (TTI) that has a shorter TTI duration than 1 ms and/or in a cell in which communication is controlled by applying shortened processing time that is shorter than processing time in an existing LTE system, and this user terminal has a measurement section that measures channel state information (CSI) by using a CSI reference resource, and a transmission section that transmits the CSI in a given subframe, and the CSI reference resource is found in a subframe that is located a period before the given subframe, the period being shorter than a given time period.