OFDM Channel Estimation via Zero-Padded Phase Compensation
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Solution Overview
Problem
In OFDM systems like LTE, conventional DFT-based channel estimation fails to accurately estimate the frequency domain channel due to channel power leakage caused by sampling at non-integer tap positions, leading to noise contamination and reduced accuracy.
Innovation Solution
Estimate and compensate for the phase rotation of the frequency domain channel estimate, transform it into a time domain channel estimate, filter to suppress noise, and then revert to a noise-suppressed frequency domain estimate, thereby improving channel estimation accuracy while maintaining low computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional DFT-based channel estimation is used in OFDM systems with partial frequency bandwidth access, then the estimation process can be implemented, but channel power leaks to all taps in the time domain due to sampling at non-integer tap positions, causing noise contamination and reduced accuracy
Solution Approach 1:
The patent applies preliminary action by performing zero-padding in the frequency domain before transforming to the time domain. This preparatory step ensures that when the inverse DFT is performed, the channel impulse response is properly sampled at integer tap positions, preventing channel power leakage before the transformation occurs. The zero-padding is done in advance to set up the correct sampling conditions.
Solution Approach 2:
The patent changes the sampling parameters by using zero-padding to effectively change the sampling rate and sampling positions in the time domain. By adding zeros in the frequency domain, the inverse DFT produces a time domain signal that is sampled at integer multiples of the sampling interval, thereby changing the sampling parameters from non-integer to integer positions and eliminating the leakage effect.
2Device complexity
If conventional DFT-based channel estimation is used, then the process is computationally simple, but the channel power leaks to all taps in the time domain, making it impossible to distinguish useful channel power from noise
Solution Approach 1:
The patent applies preliminary action by performing zero-padding in the frequency domain before transforming to the time domain. This preparatory step ensures that when the inverse DFT is performed, the channel impulse response is properly sampled at integer tap positions, preventing channel power leakage before the transformation occurs. The zero-padding is done in advance to set up the correct sampling conditions.
Solution Approach 2:
The patent changes the sampling parameters by using zero-padding to effectively change the sampling rate and sampling positions in the time domain. By adding zeros in the frequency domain, the inverse DFT produces a time domain signal that is sampled at integer multiples of the sampling interval, thereby changing the sampling parameters from non-integer to integer positions and eliminating the leakage effect.
3Adaptability or versatility
If each user accesses only a part of the available frequency bandwidth in OFDMA/SC-FDMA systems, then user-specific frequency allocation is achieved, but channel estimates are only available for a part of the complete frequency bandwidth, preventing accurate time domain channel estimation
Solution Approach 1:
The patent applies preliminary action by performing zero-padding in the frequency domain before transforming to the time domain. This preparatory step ensures that when the inverse DFT is performed, the channel impulse response is properly sampled at integer tap positions, preventing channel power leakage before the transformation occurs. The zero-padding is done in advance to set up the correct sampling conditions.
Solution Approach 2:
The patent changes the sampling parameters by using zero-padding to effectively change the sampling rate and sampling positions in the time domain. By adding zeros in the frequency domain, the inverse DFT produces a time domain signal that is sampled at integer multiples of the sampling interval, thereby changing the sampling parameters from non-integer to integer positions and eliminating the leakage effect.
Data Source
AI summary
The present invention relates to a receiving node, and to a related method of adjusting a frequency domain channel estimate in a receiving node of a wireless communication system using Orthogonal Frequency Division Multiplexing. The method comprises estimating (210) a phase rotation of the frequency domain channel estimate, and compensating (220) for the estimated phase rotation in the frequency domain channel estimate. It also comprises transforming (230) the compensated frequency domain channel estimate into a time domain channel estimate, filtering (240) the time domain channel estimate to suppress noise, transforming (250) the filtered time domain channel estimate back into a noise suppressed frequency domain channel estimate, and adding (260) the estimated phase rotation in the noise suppressed frequency domain channel estimate to achieve an adjusted and improved frequency domain channel estimate.