OFDM Channel Estimation Mitigating Edge Effect
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Solution Overview
Problem
The existing FFT interpolation channel estimation method in OFDM systems suffers from significant errors, particularly at the edge frequency points of the bandwidth, due to insufficient sampling, leading to an 'edge effect' that compromises the accuracy of channel estimation.
Innovation Solution
The proposed method involves mirroring pilot points at the edges of the effective sub-carrier frequency band, performing IFFT, windowing, zero-padding, and FFT to increase the number of pilot points, thereby mitigating the edge effect and improving channel estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If FFT interpolation channel estimation is used, then implementation complexity is reduced and operations are fewer, but measurement precision deteriorates due to large errors at edge frequency points
Solution Approach 1:
The patent applies preliminary action by adding virtual pilot points at the edge frequency bands before performing FFT interpolation. This pre-processing step extends the pilot signal coverage to include protection sidebands, ensuring that the interpolation process has sufficient reference points at the edges to maintain accuracy without increasing the complexity of the overall estimation algorithm.
Solution Approach 2:
The patent uses copying by creating virtual pilot points that replicate the characteristics of existing pilot points and placing them at the edge frequency bands. These copied pilot signals serve as additional reference points for interpolation, enabling accurate channel estimation at edge frequencies without requiring additional physical pilots or increasing system complexity.
2Measurement precision
If pilot points are increased to reduce edge effect, then measurement precision improves, but device complexity increases due to additional processing operations
Solution Approach 1:
The patent applies dimensionality change by extending the frequency domain representation from the effective sub-carrier band to include the protection sideband region. By adding virtual pilot points in this extended frequency dimension, the method improves edge frequency estimation accuracy without requiring additional time-domain processing or increasing the number of actual transmitted pilots, thus avoiding complexity increases.
3Device complexity
If pilots sample only effective sub-carrier frequency band, then device complexity is reduced, but measurement precision deteriorates due to insufficient sampling coverage
Solution Approach 1:
The patent introduces virtual pilot points as an intermediary element that bridges the gap between the effective sub-carrier band and the protection sidebands. These virtual pilots act as mediators that extend the sampling coverage to the full frequency band without requiring actual additional pilots, thereby improving measurement precision while maintaining the simplicity of the original sampling structure.
Data Source
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AI summary
A channel estimation method of an Orthogonal Frequency Division Multiplexing (OFDM) system and a corresponding receiving apparatus are provided. The technical solutions use the receiving apparatus to firstly perform channel estimation in time dimension on received signals, obtain channel information of pilot points from an effective sub-carrier frequency band on a frequency domain of each OFDM symbol, obtain information of the pilot points on frequency bands outside the effective sub-carrier frequency band by adding the information of the pilot points, and then perform Inverse Fast Fourier Transform (IFFT), windowing, zero-padding, and Fast Fourier Transform (FFT) to obtain a channel frequency response, so as to obtain a channel estimation result. The technical solutions can achieve goals of restraining an edge effect and improving accuracy of the channel estimation.