Channel Estimation Edge Effect Reduction via Signal Extension
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Solution Overview
Problem
OFDM systems face challenges in channel estimation due to edge effects caused by the use of FFT/IFFT on blocks of data, which limits the choice of known signal portions and increases the complexity and cost of channel estimation circuits, especially when signal samples do not have the proper number of samples.
Innovation Solution
A channel estimation system that uses FFT and IFFT circuits for any length of known signal portions, incorporating an extension circuit to create an extended frequency domain signal, followed by IDFT and DFT operations, and filtering to reduce edge effects, allowing for accurate channel estimation without the limitations of signal length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If FFT/IFFT is used for channel estimation, then circuit complexity is reduced, but edge effects cause disruption to channel estimation accuracy
Solution Approach 1:
The patent applies preliminary action by extending the known signal portion with additional samples before performing FFT/IFFT operations. This extension is done in advance to prevent edge effects from disrupting the channel estimation, thereby maintaining both circuit simplicity and estimation accuracy.
Solution Approach 2:
The patent applies preliminary anti-action by introducing extended signal samples that counteract the harmful edge effects. These additional samples are prepared beforehand to compensate for the disruptions caused by FFT/IFFT operations, ensuring accurate channel estimation without requiring complex circuits.
2Device complexity
If known signal portion length is limited to powers of two for FFT/IFFT, then circuit design is simplified, but design flexibility is reduced
Solution Approach 1:
The patent applies universality by creating a channel estimation method that works with known signal portions of any length. The extension technique allows the system to handle various signal lengths without requiring different circuit designs, making the solution universally applicable while maintaining FFT/IFFT efficiency.
Solution Approach 2:
The patent applies preliminary action by extending the known signal portion with additional samples before FFT/IFFT processing. This pre-extension allows the system to accommodate any original signal length while still using efficient power-of-two FFT/IFFT circuits, thereby preserving both simplicity and flexibility.
3Adaptability or versatility
If signal samples are passed through FFT and IFFT despite not having proper number of samples, then any signal length can be processed, but edge effects are exacerbated
Solution Approach 1:
The patent applies preliminary action by extending the signal samples with additional known values before passing them through FFT/IFFT. This extension ensures that the input always has the proper number of samples required for efficient processing while preventing edge effects from degrading accuracy, thus maintaining both adaptability and precision.
Solution Approach 2:
The patent converts the harmful edge effects into a benefit by using the extension technique. The additional samples introduced are specifically designed to counteract the edge effects, transforming what would be a source of error into a mechanism that actually improves channel estimation accuracy while maintaining signal length flexibility.
Data Source
AI summary
A channel estimator (150) is provided that comprises: an extension circuit (410) configured to receive a pilot signal (510), and add front and back extension signals (620, 630) to a front and back of the pilot signal, respectively, creating a first signal (610), the front and back extension signals being extension of a first and last symbol, respectively, in the pilot signal; an IDFT circuit (420) configured to perform an IDFT function on the first signal, generating a second signal (710); a signal processing element (430, 440, 470, 480) configured to perform one or more operations on the second signal, generating a third signal (910); a DFT circuit (450) configured to perform a DFT function on the third signal, generating a fourth signal (1010); and a reduction circuit configured to cut off front and back ends of the fourth signal, generating a channel estimation signal (1110).