OFDM Receiver Carrier Frequency Correction in Multipath
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Solution Overview
Problem
In OFDM systems, synchronization corrections for carrier frequencies and clock frequencies are challenging in multipath environments with multiple desired waves at different delay times and varying carrier frequencies, leading to degraded signal receiving quality and non-convergent synchronization processes.
Innovation Solution
A receiver is designed with a transformation part to convert signals to the frequency domain, extracting channel characteristics to calculate carrier frequency errors using power spectra and correcting carrier frequencies, while improving clock frequency correction accuracy by combining multiple delay profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier correction is performed based on the phase excursion of one desired wave in a multipath environment, then the carrier frequency of that specific wave is corrected, but offsets occur from the phase excursions of other desired waves, degrading signal receiving quality
Solution Approach 1:
The patent combines phase excursion information from multiple desired waves at different delay times into a unified carrier correction process. Instead of correcting based on a single wave, the system integrates phase data from all detected desired waves to determine a common carrier frequency correction that benefits the entire signal, thereby resolving the contradiction between precise correction of individual waves and overall signal quality.
2Measurement precision
If the number of IFFT points is increased to improve clock error detection resolution, then the maximum delay time analyzable is improved, but the device complexity and computation load increase
Solution Approach 1:
The patent applies partial action by using only the necessary number of IFFT points required to achieve the desired clock error detection resolution and maximum delay time coverage. Rather than always using the maximum possible IFFT points, the system determines the minimum sufficient configuration based on the specific channel conditions and requirements, thereby achieving adequate precision without excessive computational complexity.
3Adaptability or versatility
If synchronization correction is performed in a multipath environment with multiple desired waves at different delay times and carrier frequencies, then comprehensive signal correction is attempted, but the synchronization process may not converge at the optimum position
Solution Approach 1:
The patent segments the synchronization correction process into distinct stages: first detecting desired waves at different delay times, then separately analyzing their phase excursions and delay time offsets, and finally integrating these segmented results into a unified synchronization correction. This segmentation allows the system to handle multiple desired waves systematically without causing convergence failures, while still achieving comprehensive signal correction.
Data Source
AI summary
A receiver includes a transformation part configured to convert a time domain received signal to a frequency domain signal, a known signal extraction part configured to extract a known signal from the frequency domain signal, an estimation part configured to estimate a channel characteristic based upon the extracted known signal, a time direction extraction part configured to extract channel characteristic values of a particular carrier in a time direction from the estimated channel characteristic, a power spectrum acquiring part configured to acquire a power spectrum from the channel characteristic values extracted in the time direction, an error calculation part configured to calculate a carrier frequency error from the power spectrum, and a carrier correction part configured to correct for a carrier frequency of the received signal based upon the carrier frequency error.