OFDM Receiver Adaptive Filtering for High-Speed Channel Estimation
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Solution Overview
Problem
Conventional orthogonal frequency division multiplexed (OFDM) signal receiving apparatuses experience deteriorated channel estimation accuracy and errors in data reception when moving at high speeds, leading to potential errors in amplitude and phase correction of subcarriers.
Innovation Solution
The apparatus employs a discrete Fourier transform unit, channel estimation, equalization, timing generation, memory, filtering, and coefficient update units to optimize filter coefficients using adaptive algorithms like steepest descent or recursive least-squares, and considers pilot carrier reliability to reduce channel estimation errors and improve receiving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional channel estimation using minimum pilot carriers is used to maximize data transmission amount, then data transmission capacity is improved, but channel estimation accuracy deteriorates during high-speed movement
Solution Approach 1:
The patent performs preliminary channel estimation using pilot carriers before data reception, and then applies adaptive filtering to refine the estimation. This preliminary action allows the system to prepare accurate channel state information in advance, which is then used to correct errors during actual data reception, thereby maintaining high estimation accuracy even with limited pilot carriers.
Solution Approach 2:
The patent implements an adaptive filtering mechanism that continuously updates filter coefficients based on received pilot carriers and channel conditions. This feedback loop allows the system to adjust to changing channel characteristics during high-speed movement, maintaining accurate channel estimation despite the limited number of pilot carriers used for transmission.
2Measurement precision
If the number of pilot carriers is increased to improve channel estimation accuracy, then measurement precision is improved, but data transmission capacity decreases
Solution Approach 1:
The patent introduces an adaptive filter as an intermediary processing stage between pilot carrier reception and channel estimation. This intermediary component enhances the effectiveness of limited pilot carriers by applying optimized filtering techniques, thereby achieving high estimation accuracy without needing to increase the number of pilot carriers, thus preserving data transmission capacity.
Solution Approach 2:
The patent dynamically adjusts filter parameters and coefficients based on received pilot carriers and channel conditions. By optimizing these parameters adaptively, the system maximizes channel estimation accuracy from the available pilot carriers without requiring additional pilot carriers, thus maintaining high data transmission capacity.
3Adaptability or versatility
If channel estimation is performed by interpolating pilot carriers in time and frequency directions to follow channel changes, then adaptability is improved, but measurement precision deteriorates at high speeds
Solution Approach 1:
The patent employs dynamic adaptive filtering where filter coefficients are continuously updated based on current channel conditions and pilot carrier observations. This dynamic approach allows the system to track channel changes during high-speed movement more accurately than static interpolation methods, maintaining measurement precision while preserving adaptability to changing conditions.
Solution Approach 2:
The patent uses feedback from continuously received pilot carriers to update channel estimates and adjust filter parameters in real-time. This feedback mechanism enables the system to adapt to channel changes during high-speed movement while maintaining accurate estimation, overcoming the limitations of pure interpolation methods that deteriorate at high speeds.
Data Source
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AI summary
An object of the present invention is to provide an orthogonal frequency division multiplexed signal receiving apparatus that is capable of compensating for channel estimation errors due to the receipt of signals when moving fast and thereby properly reproducing transmission data. Such an orthogonal frequency division multiplexed signal receiving apparatus (100) includes a discrete Fourier transform unit (1) for transforming a signal that has been frequency-translated to a desired frequency, by the discrete Fourier transform, to demodulate the signal into a sequence of subcarriers, a channel estimation unit (2) for estimating a channel characteristic for each subcarrier, an equalization unit (3) for outputting an equalized signal that is obtained by equalizing the subcarriers and a header signal that is synchronized with a received symbol, a timing generation unit (4) for generating, based on the header signal, a timing signal used for downstream processing, a memory unit (5) for repeatedly outputting an equalized signal n times, where n ≥ 2 , a filtering unit (6) for filtering an equalized signal based on a filter coefficient and outputting a signal that is compensated for the nth equalized signal as a demodulated signal, and a coefficient update unit (7) for computing a filter coefficient and updating the filter coefficient to a computed filter coefficient in the filtering unit (6).