FFT Module Timing Window Adjustment for OFDM Synchronization
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Solution Overview
Problem
OFDM receivers face challenges in sample timing synchronization due to feedback delays and nonlinear mathematical operations in FFT modules, leading to performance losses and increased error generation when correcting timing errors.
Innovation Solution
A Fast Fourier Transform (FFT) module with an input for receiving timing window correction signals, allowing for immediate adjustment of the timing window within the input queue, reducing the number of symbols processed with incorrect timing by using a tracker to generate error signals for correcting sample synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional FFT modules process samples through nonlinear mathematical operations in a pipeline, then data processing is achieved, but feedback delays occur and timing error correction is delayed causing performance loss
Solution Approach 1:
The patent applies preliminary action by detecting timing errors at the output of the FFT module and immediately adjusting the timing window of the input queue before subsequent symbols are processed. This forward adjustment mechanism eliminates feedback delays by correcting timing errors in advance, preventing performance loss from delayed correction.
Solution Approach 2:
The patent implements feedback by using a tracker to monitor output symbols and generate timing error signals that are fed back to adjust the timing window of the input queue. This closed-loop feedback mechanism continuously corrects timing synchronization errors, improving reliability despite the pipelined processing structure.
2Reliability
If the timing window is adjusted after timing errors are detected in processed symbols, then timing synchronization is corrected, but multiple subsequent symbols have already been processed with incorrect timing causing error propagation
Solution Approach 1:
The patent uses preliminary action by adjusting the timing window of the input queue immediately when timing errors are detected, before subsequent symbols enter the FFT processing pipeline. This prevents error propagation to future symbols, maintaining high decoding accuracy without sacrificing processing throughput.
Solution Approach 2:
The patent applies skipping by rapidly adjusting the timing window parameter in response to detected errors, effectively rushing through the correction process. This minimizes the window of vulnerability where incorrect timing could affect multiple symbols, reducing error generation while maintaining productivity.
3Productivity
If data buffers are provided at the input of the FFT module to permit parallel processing, then processing efficiency is improved, but the timing window adjustment cannot be applied immediately to correct synchronization errors
Solution Approach 1:
The patent combines parallel processing with preliminary action by maintaining data buffers for efficient FFT processing while simultaneously adjusting the timing window of the input queue in advance. This allows the system to maintain high productivity through parallel processing while ensuring timing corrections are applied responsively before data enters the processing pipeline.
Data Source
AI summary
A FFT module for a baseband processor of a receiver includes an input for receiving a timing window correction signal. In response to the timing window correction signal the FFT module adjusts a timing window for processing groups of samples within an input queue of the FFT module.