OFDMA Measurement Reference Signal Mapping for FD-MIMO Precision
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Solution Overview
Problem
In future radio communication systems like 5G, the existing SRS is inadequate for precise channel state measurement in FD-MIMO, leading to insufficient feedback and interference issues, which hinders accurate beam control and measurement precision.
Innovation Solution
A user terminal configured to generate and transmit an enhanced SRS using orthogonal frequency division multiple access (OFDMA), allowing for flexible mapping of the measurement reference signal to discontinuous resources in the time and frequency directions, improving measurement precision and reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing SRS is used for measurement in FD-MIMO, then device complexity is reduced, but measurement precision is insufficient
Solution Approach 1:
The patent changes the fundamental parameters of the measurement reference signal by adopting OFDMA modulation instead of traditional SC-FDMA, enabling flexible resource mapping in both time and frequency domains. This parameter change allows the reference signal to be distributed across multiple resource elements, improving measurement precision while maintaining manageable device complexity through standardized signal generation procedures
Solution Approach 2:
The patent introduces discontinuous resource mapping in both time and frequency dimensions, transforming the traditional one-dimensional continuous SRS transmission into a two-dimensional distributed structure. This dimensional expansion allows measurements to be performed across multiple frequency subcarriers and time symbols, significantly enhancing channel state estimation accuracy for FD-MIMO systems
2Measurement precision
If user terminal feedbacks high precision channel state information, then measurement precision is improved, but feedback information amount becomes too large
Solution Approach 1:
The patent extracts the essential channel state information directly at the radio base station by utilizing uplink-downlink channel reciprocity. Instead of requiring the user terminal to compute and feedback comprehensive channel state information, the base station performs measurements on the OFDMA-based reference signal and extracts the necessary channel state parameters, thereby maintaining high precision while minimizing feedback overhead
Solution Approach 2:
The patent introduces an enhanced measurement reference signal as an intermediary that enables direct measurement at the base station. This intermediary signal carries sufficient information for the base station to perform accurate channel estimation through reciprocity, eliminating the need for complex terminal-side channel state computation and large-scale feedback
3Manufacturing precision
If existing SRS is used for beam control in FD-MIMO, then device complexity is reduced, but beam control accuracy is insufficient
Solution Approach 1:
The patent changes the signal structure parameters by implementing discontinuous resource mapping in time and frequency domains, which provides more comprehensive channel sampling for beam training. This enables more accurate estimation of channel characteristics across different spatial directions, improving beam control accuracy while maintaining device complexity at acceptable levels through efficient reference signal design
Solution Approach 2:
The patent segments the measurement reference signal across multiple frequency subcarriers and time symbols, creating a distributed measurement structure. This segmentation allows the system to capture channel variations across different frequency and time instances, providing more robust information for beam direction estimation and improving beam control accuracy in FD-MIMO systems
Data Source
AI summary
According to the present invention, a radio base station uses a measurement reference signal transmitted from a user terminal to carry out a measurement with a sufficient precision. According to an embodiment, a user terminal is configured to apply orthogonal frequency division multiple access (OFDMA) in an uplink, the user terminal including a generating section configured to generate a measurement reference signal used for carrying out a measurement in a radio base station; a mapping section configured to map the measurement reference signal to a radio resource that is discontinuous in a time direction and/or a frequency direction; and a transmitting section configured to transmit the measurement reference signal to the radio base station.