Maximum Doppler Frequency Estimation in Channel Models
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Solution Overview
Problem
The existing methods for calculating the maximum Doppler frequency in channel models fail to accurately estimate this parameter in actual propagation path environments, especially when the influence of moving objects cannot be ignored, leading to unrealistic estimates even when the mobile phone terminal is stationary.
Innovation Solution
A test system and method that utilize IQ data from downlink signals to calculate estimation characteristics, transforming them into frequency domain to estimate the maximum Doppler frequency, considering the influence of moving objects by calculating quasi-Doppler or Doppler spectra, which allows for accurate estimation even at zero or low movement velocities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the maximum Doppler frequency is calculated using the formula fd=vfc/c based on mobile phone terminal movement velocity, then the calculation is simple and follows standard channel models, but the estimation becomes unrealistic when the mobile phone terminal is stationary or when the influence of moving objects in the environment cannot be ignored
Solution Approach 1:
The patent replaces the mechanical calculation method (using terminal velocity v in fd=vfc/c) with a signal processing approach. By transforming channel estimation characteristics from time domain to frequency domain and analyzing the Doppler spectrum, the system extracts the maximum Doppler frequency directly from the spectral characteristics without relying on terminal velocity measurements. This substitution allows accurate estimation even when the terminal is stationary but surrounded by moving objects.
2Ease of operation
If a predetermined value is used for maximum Doppler frequency in conformance tests, then the test procedure is standardized and simple, but the test cannot evaluate performance under realistic propagation conditions with moving objects
Solution Approach 1:
The patent transforms the static, predetermined maximum Doppler frequency value into a dynamic parameter that adapts to actual propagation conditions. By continuously analyzing the Doppler spectrum from received signals and identifying the frequency with maximum power, the system automatically adjusts the maximum Doppler frequency to reflect the current environment, including the presence and movement of objects in the propagation path.
3Measurement precision
If the channel model parameters are configured to match actual propagation path characteristics, then the evaluation of demodulation performance becomes more realistic, but the calculation of maximum Doppler frequency becomes complex requiring transformation between time and frequency domains
Solution Approach 1:
The patent performs preliminary transformation of channel estimation characteristics from time domain to frequency domain using Fast Fourier Transform (FFT). By pre-processing the time-domain channel estimates and converting them to the frequency domain, the system prepares the data in a format that directly reveals the Doppler spectrum characteristics. This preliminary action simplifies subsequent analysis steps while maintaining high accuracy in maximum Doppler frequency estimation.
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
The system effectively estimates the maximum Doppler frequency in actual propagation path environments, accounting for the influence of moving objects, thereby providing a more realistic and accurate representation of channel conditions.
Implementation Method 1
a domain transformation unit (22a) that transforms the estimation characteristics H{circumflex over ( )}nij(k) in a subcarrier k (k is an integer from 0 to K−1) from time domain characteristics indicating a temporal change of each subcarrier to frequency domain characteristics Gkij(f)
Implementation Method 2
a quasi-Doppler spectrum calculation unit (22b) that calculates a quasi-Doppler spectrum of the analysis target channel by adding a power spectrum, for each subcarrier, of the frequency domain characteristics Gkij(f) for K subcarriers, and a maximum Doppler frequency estimation unit (22c) that estimates a maximum value among the frequencies of frequency components of the quasi-Doppler spectrum
Data Source
AI summary
A test system includes an actual propagation path estimation characteristic calculation unit that calculates estimation characteristics, at a plurality of analysis target timings, of propagation path characteristics of an analysis target channel among one or more channels constituting an actual propagation path, and a parameter calculation unit that calculates a maximum Doppler frequency of the analysis target channel, as one of parameters characterizing statistical properties of the estimation characteristics of the propagation path characteristics, in which the parameter calculation unit includes a maximum Doppler frequency estimation unit that estimates a maximum value among the frequencies of frequency components of a quasi-Doppler spectrum of the analysis target channel that have power equal to or higher than specified power, as the maximum Doppler frequency.