OFDM Receiver Frequency Response Estimation via Zero Insertion
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Solution Overview
Problem
Existing OFDM signal receiving systems face challenges in reducing frequency response estimation error and require increased circuit size and processing load due to side lobes in impulse responses and aliasing components, especially when impulse responses do not coincide with sampling times.
Innovation Solution
The proposed OFDM signal receiving apparatus employs a series of processing steps including Fourier transforms, zero insertion, window function multiplication, coring, truncation, and interpolation to generate and compensate for frequency responses, reducing estimation errors and circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scattered pilot signals are used for channel estimation in OFDM systems, then frequency response can be estimated at pilot intervals, but side lobes appear in impulse response and aliasing components increase when impulse response does not coincide with sampling time
Solution Approach 1:
The patent applies preliminary action by performing zero signal insertion and window function multiplication on the frequency response before inverse Fourier transformation. This preprocessing eliminates side lobes in the impulse response before corruption occurs, preventing aliasing components from appearing in the final frequency response estimation.
2Measurement precision
If coring and truncation circuits are used to process impulse response, then aliasing components are removed, but circuit size and processing load increase
Solution Approach 1:
The patent extracts and eliminates the root cause of side lobes by applying zero signal insertion and window function multiplication in the frequency domain before inverse Fourier transformation. This approach removes the need for complex coring and truncation circuits in the time domain, significantly reducing circuit size and processing load while maintaining estimation precision.
3Measurement precision
If inverse Fourier transform and Fourier transform are performed with same data samples as main Fourier Transform circuit, then frequency response interpolation is achieved, but processing load increases for software implementation
Solution Approach 1:
The patent applies partial action by performing inverse Fourier transform and coring only on a portion of the frequency response data (where side lobes are present), rather than processing all data samples. This selective processing reduces the computational load for software implementation while still achieving effective frequency response interpolation.
Data Source
AI summary
An OFDM signal receiver reduces frequency response estimation error, and reduces the circuit scale needed for a hardware implementation and the number of operations performed in a software implementation. A first Fourier transform circuit converts an OFDM signal to the frequency domain by a Fourier transform. A first divider divides the pilot signal contained in the frequency domain OFDM signal by a specified pilot signal. A zero insertion means then inserts zero signals in the first divider output. A window function multiplying means multiplies the zero insertion means output by a window function, and an inverse Fourier transform means applies an inverse Fourier transform to the multiplier output. A coring means then cores the inverse Fourier transform output, and truncation means truncates the coring means output at a specified data length. A second Fourier transform circuit applies another Fourier transform to the truncated result. A window function dividing means then divides the Fourier transform result by the window function, and a second dividing means divides the output of the first Fourier transform means by the output of the window function dividing means.