Uplink Doppler Metric Estimation via SRS Configuration
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Solution Overview
Problem
In wireless communications, accurately determining the uplink Doppler frequency is challenging due to inaccurate estimation from reference signals that are ill-suited for Doppler frequency measurement, leading to suboptimal demodulation reference signal configurations and reduced spectral efficiency.
Innovation Solution
A base station configures an uplink sounding reference signal with consistent repetition spacing based on the subcarrier spacing and carrier frequency used by the user equipment, allowing for accurate Doppler frequency estimation and selection of a suitable demodulation reference signal configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional reference signals are used for Doppler frequency estimation, then the estimation process can be performed, but the estimation accuracy is poor leading to suboptimal demodulation reference signal configurations
Solution Approach 1:
The base station performs preliminary Doppler frequency estimation using sounding reference signals before configuring demodulation reference signals. This preliminary action allows the system to determine appropriate demodulation reference signal configurations (such as time spacing between repetitions) based on the estimated Doppler characteristics, thereby optimizing spectral efficiency for the actual channel conditions.
Solution Approach 2:
The system changes parameters of the demodulation reference signal configuration based on the estimated Doppler frequency. Specifically, the time spacing between demodulation reference signal repetitions is adjusted according to the Doppler characteristics - larger spacing for high Doppler frequencies and smaller spacing for low Doppler frequencies, thereby optimizing the configuration to match channel conditions.
2Measurement precision
If reference signals with inconsistent spacing are used, then the measurement process is simpler, but the Doppler frequency estimation becomes inaccurate
Solution Approach 1:
The sounding reference signal configuration is specifically optimized for the local task of Doppler frequency estimation. The base station configures sounding reference signals with appropriate time spacing and repetition patterns that are locally optimized for accurate Doppler measurement, while other reference signals maintain their standard configurations for their respective functions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy of uplink Doppler frequency estimation, enabling better selection of demodulation reference signal configurations and improving spectral efficiency in wireless communications systems.
Implementation Method 1
The base station may measure the SRS repetitions from the UE to determine the Doppler frequency for the uplink channel
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A base station may determine the subcarrier spacing and carrier frequency used by a user equipment (UE) for communicating with the base station. The base station may select a sounding reference signal (SRS) configuration for the UE that is based on the subcarrier spacing and carrier frequency used by the UE. The SRS configuration may define the temporal spacing between repetitions of the SRS. The base station may indicate the SRS configuration to the UE so that the UE transmits repetitions of the SRS according to the SRS configuration. The base station may measure the SRS repetitions from the UE to determine the Doppler frequency for the uplink channel. The base station may use the uplink Doppler frequency to select a demodulation reference signal (DMRS) configuration for the UE.