Receiver FFT Window Positioning for ATSC 3.0 Sub-Frame Switching
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Solution Overview
Problem
In the ATSC version 3.0 OFDM system, channel estimation operations face inter-symbol interference and degraded decoding performance due to poor FFT window positioning and channel impulse response arrangement when switching between sub-frames with different parameters.
Innovation Solution
A receiver is designed with a signal processing method that uses the channel profile of the last symbol of a sub-frame to determine the FFT window start point and channel offset for the next sub-frame, ensuring optimal processing by adjusting these parameters based on attribute differences between sub-frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FFT window position is not accurately adjusted when switching sub-frames, then processing speed is maintained, but channel estimation accuracy deteriorates due to inter-symbol interference
Solution Approach 1:
The patent performs preliminary channel estimation using the previous sub-frame's channel profile before actually switching to the new sub-frame. The FFT window start point is pre-calculated based on the previous channel impulse response, so when sub-frame switching occurs, the processing can immediately use the pre-determined parameters without causing inter-symbol interference. This preliminary action ensures accuracy without adding complex real-time adjustment mechanisms.
Solution Approach 2:
The system uses its own previous sub-frame processing results (channel impulse response and channel profile) to automatically determine the optimal FFT window positioning for the current sub-frame. The channel estimation circuit generates the channel profile that directly feeds into the FFT window start point calculation, creating a self-service loop where the system's own output from the previous operation becomes the input for optimizing the current operation, eliminating the need for external complex control mechanisms.
2Reliability
If FFT window start point is fixed for all sub-frames, then device complexity is reduced, but decoding performance deteriorates when sub-frame parameters change
Solution Approach 1:
The patent implements dynamic adjustment of the FFT window start point based on the actual channel conditions of each sub-frame. Instead of using a fixed position, the system continuously updates the FFT window start point calculation using the channel impulse response and channel profile from the previous sub-frame. This dynamic adaptation ensures that when sub-frame parameters such as guard interval length or scattered pilot pattern change, the FFT window positioning automatically adjusts to maintain optimal decoding performance.
Solution Approach 2:
The system establishes a feedback loop where the channel estimation results from each sub-frame are fed back to determine the FFT window start point for the next sub-frame. The channel profile generated from the previous sub-frame's channel impulse response serves as feedback that directly influences the parameter selection for the current sub-frame, creating a closed-loop control system that maintains high decoding performance across varying sub-frame parameters without requiring complex external control.
3Object-affected harmful factors
If channel impulse response is not properly positioned, then processing simplicity is maintained, but signal quality deteriorates due to inter-symbol interference
Solution Approach 1:
The patent replaces complex mechanical or algorithmic methods for determining optimal FFT window positioning with a signal-processing-based approach. Instead of using predefined tables or complex optimization algorithms, the system uses the channel impulse response itself as the basis for calculating the FFT window start point. The channel estimation circuit processes the received signal to extract channel characteristics, and these characteristics directly determine the parameter adjustments needed to eliminate inter-symbol interference, substituting signal processing for more complex positioning mechanisms.
Data Source
AI summary
A signal processing method including the steps of: using a FFT window to process a last symbol of a first sub-frame of a frame to generate a frequency-domain signal, wherein the FFT window has a first start point; performing an IFFT operation on the frequency-domain signal to generate a channel impulse response; performing a channel estimation on the channel impulse response to generate a channel profile; referring to the channel profile of the last symbol of the first sub-frame, an attribute of a start symbol of a second sub-frame and the first FFT window start point to determine a second FFT window start point; using the FFT window having the second start point to process the start symbol of the second sub-frame to generate another frequency-domain signal.