OFDM CPE Correction via FFT Output Reordering
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Solution Overview
Problem
Conventional OFDM signal receiving apparatuses are cumbersome and complex due to the requirement of large memory capacity for storing subcarrier values, which affects the efficiency of common phase error (CPE) correction in HDTV broadcast systems, leading to performance deterioration.
Innovation Solution
An OFDM demodulator with a fast Fourier transformation (FFT) block and a correction block that includes an output shuffle memory, CP location memory, and a complex conjugate multiplier to reorder and correct CPE by multiplying reordered output values of current and previous OFDM symbols, reducing memory requirements and simplifying hardware structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large memory capacity is used to store subcarrier values for CPE correction, then CPE correction accuracy is improved, but device complexity and hardware structure become cumbersome
Solution Approach 1:
The patent extracts only the necessary subcarrier values (continual pilot values) from the FFT output for CPE correction, rather than storing all subcarrier values. This selective extraction reduces memory requirements while maintaining correction accuracy, directly resolving the contradiction between precision and complexity.
Solution Approach 2:
The patent segments the FFT output into specific continual pilot locations that are relevant for CPE correction. By identifying and processing only these specific segments (continual pilots at known frequency positions), the system achieves accurate CPE correction without the overhead of storing and processing the entire spectrum.
2Reliability
If conventional CPE correction methods are used, then phase error correction is achieved, but memory requirements increase and processing efficiency decreases
Solution Approach 1:
The patent performs preliminary reordering of FFT output values according to continual pilot locations before the CPE correction process. This preliminary organization allows the correction algorithm to access only the necessary data in the correct sequence, reducing memory requirements while ensuring reliable phase error correction.
Solution Approach 2:
The patent changes the organizational parameter of the FFT output from conventional sequential ordering to continual-pilot-based reordering. This parameter change enables more efficient memory utilization by grouping relevant data together, reducing the total memory capacity needed while maintaining correction reliability.
3Measurement precision
If all FFT output values are processed for CPE correction, then correction completeness is improved, but processing time and computational complexity increase
Solution Approach 1:
The patent extracts and processes only the continual pilot values from the complete FFT output for CPE correction. This selective extraction maintains correction completeness because continual pilots contain the necessary phase information, while significantly reducing processing time by avoiding unnecessary computation on non-pilot subcarriers.
Data Source
AI summary
An apparatus, method and computer program for correcting a common phase error (CPE) of symbols of a received OFDM signal is described, in which FFT processing may be performed on a time domain OFDM to transform the received signal to a signal in the frequency-domain. Reordered output values resulting from the FFT processing and locations of the reordered output values may be stored. One or more of the stored reordered output values for a current symbol of the OFDM signal may be transferred based on receipt of an address, and each of the transferred reordered output values may be multiplied by a corresponding reordered output value of a previous OFDM signal symbol, so as to determine phase differences between the reordered output values of the current and previous OFDM signal symbols. The CPE of the transformed OFDM signal may be corrected based on the detected phase differences.