Timing Correction for Serial Offset QPSK Signals
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Solution Overview
Problem
Existing communication systems face challenges in accurately correcting synchronization errors for serial offset quadrature pulse-shaped spread signals, which affects data despreading performance, especially in multi-path channels.
Innovation Solution
A method and system that decimate serial in-phase and quadrature signals to form even and odd samples, obtain autocorrelation and cross-correlation profiles, and adjust the synchronization starting point to correct timing errors, allowing for effective despreading using either even or odd samples based on profile analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional timing correction methods are used for serial offset quadrature pulse-shaped spread signals, then synchronization error correction can be achieved, but the complexity of the synchronization process increases and processing time is extended
Solution Approach 1:
The patent divides the timing correction process into discrete steps: (1) correlating the received signal with the spreading code to generate correlation values, (2) identifying peak correlation values that indicate synchronization points, (3) adjusting the synchronization starting point based on the identified peaks, and (4) selecting even or odd samples based on the adjusted synchronization point. This segmentation reduces the overall complexity by breaking down the timing correction into manageable operations rather than requiring a single complex correction algorithm.
Solution Approach 2:
The patent performs preliminary correlation between the received signal and the spreading code before actual data despreading. By pre-identifying the synchronization starting point and determining whether to use even or odd samples during this correlation phase, the system prepares all necessary timing information in advance. This preliminary action eliminates the need for complex real-time timing adjustments during the main data processing phase, thereby reducing overall system complexity while maintaining high synchronization accuracy.
2Measurement precision
If traditional timing correction methods are used, then synchronization error can be corrected, but the data processing time increases
Solution Approach 1:
The patent performs the correlation operation and synchronization point identification during the same time frame as the data despreading process. By pre-determining whether to use even or odd samples and adjusting the synchronization starting point in advance, the system eliminates sequential processing steps that would otherwise extend the total processing time. The timing correction is integrated into the data processing flow rather than being a separate pre-processing or post-processing stage.
Solution Approach 2:
The patent dynamically selects between even and odd samples based on the adjusted synchronization starting point identified during correlation. This dynamic adaptation allows the system to optimize the processing path in real-time based on the actual signal characteristics, avoiding fixed-time processing delays and reducing overall processing time while maintaining high timing correction accuracy.
3Measurement precision
If complex synchronization algorithms are applied, then timing correction can be achieved, but the computational resources required increase
Solution Approach 1:
The patent segments the computational tasks into two efficient stages: (1) correlation computation between the received signal and spreading code to identify synchronization points, and (2) simple selection of even or odd samples based on the identified points. This segmentation replaces complex synchronization algorithms with two straightforward operations that require significantly fewer computational resources while achieving the same synchronization accuracy.
Solution Approach 2:
The patent uses a simple correlation function that can be efficiently implemented with standard signal processing techniques, replacing computationally intensive synchronization algorithms. The correlation approach leverages the inherent structure of the spreading code to achieve synchronization with minimal computational overhead, using only basic multiplication and accumulation operations rather than complex iterative optimization methods.
Data Source
AI summary
A simplified timing correction method is provided for data despreading of serial offset quadrature pulse-shaped spread signals. The simplified timing correction algorithm is applied to a rake receiver for improved performance in a multi-path channel. Serial formatting of the spreading modulation waveform is selected to reduce the SYNC/serial probe correlation complexity. The method includes the steps of: (a) decimating serial inphase (I) and quadrature (Q) signals to form decimated I and Q even samples and decimated I and Q odd samples; (b) obtaining an autocorrelation profile of a spreading sequence used by the receiver; (c) detecting a synchronization starting point using the I and Q even samples; and (d) deciding to either move, or not move, the synchronization starting point, based on the autocorrelation profile obtained in step (b). Step (d) decides to move the synchronization starting point, and uses the I and Q odd samples for subsequent despreading of the I and Q signals. Step (d) also decides not to move the synchronization starting point, and uses the I and Q even samples for subsequent despreading of the I and Q signals.