Timing Synchronization Using Power Normalized Crosscorrelation
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Solution Overview
Problem
Existing digital communication systems, particularly OFDM-based systems, face challenges in achieving accurate timing synchronization due to the uncertainty in peak location of criterion functions and the likelihood of false synchronizations, especially under high noise levels and severe multipath conditions, leading to incorrect timing estimation and potential rejection of OFDM signals.
Innovation Solution
The method employs a power normalized crosscorrelation metric (PNCC) analysis using a combination of crosscorrelation and noise floor power estimation to determine timing synchronization, with adaptive threshold adjustment and peak detection to enhance synchronization accuracy and reduce false alarms, by using a crosscorrelator, signal power estimator, noise floor power estimator, and decision logic to declare synchronization events based on multiple criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple criterion functions (autocorrelation or crosscorrelation) are used for timing synchronization, then the synchronization process is simple, but the accuracy of timing estimation deteriorates due to peak location uncertainty and false alarms
Solution Approach 1:
The patent segments the timing synchronization process into multiple stages: first using autocorrelation of training symbols to obtain a coarse timing estimate, then using crosscorrelation with the known preamble to refine the estimate. This multi-stage approach breaks down the complex task into simpler steps while improving overall accuracy.
Solution Approach 2:
The patent introduces an intermediary criterion function that combines both autocorrelation and crosscorrelation metrics. This intermediary function serves as a mediator between the simple autocorrelation method and the more accurate crosscorrelation method, providing improved timing estimation by leveraging the strengths of both approaches.
2Ease of manufacture
If threshold-based synchronization detection is used, then the implementation is straightforward, but false synchronizations increase under high noise and multipath conditions
Solution Approach 1:
The patent dynamically changes the threshold parameter based on the observed criterion function values. Instead of using a fixed predetermined threshold, the system adapts the threshold level according to the signal conditions, which reduces false alarms while maintaining implementation simplicity.
Solution Approach 2:
The patent implements feedback by using the results of the criterion function evaluation to adjust subsequent detection parameters. The system monitors the correlation outputs and uses this feedback to refine timing estimates and adjust detection thresholds, thereby improving reliability under varying noise and multipath conditions.
3Measurement precision
If coarse timing adjustment followed by fine adjustment is used, then the synchronization accuracy is improved, but the processing time and complexity increase
Solution Approach 1:
The patent performs preliminary coarse timing adjustment using autocorrelation of training symbols before applying the more computationally intensive crosscorrelation-based fine adjustment. This preliminary action reduces the search space for the fine adjustment stage, thereby reducing overall processing time while maintaining high accuracy.
Solution Approach 2:
The patent segments the timing adjustment into distinct coarse and fine stages, each optimized for its specific purpose. The coarse stage uses simpler operations to quickly establish a rough estimate, while the fine stage refines this estimate with higher precision operations, optimizing the trade-off between accuracy and processing time.
Data Source
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AI summary
The present invention relates to a method and an apparatus (300, 400) for synchronising a receiver timing to a transmitter timing using a known preamble (2) of a signal (1). In the method and the apparatus (300, 400) of the present invention, a power normalised crosscorrelat ion metric (3) (PNCC metric) is estimated based on a signal power (4) and a noise floor power (5). According to a first embodiment, two crosscorrelation functions (CF1 and CF2); one based on the PNCC metric (6) and the other based on a crosscorrelat ion metric (3) are used to decide if synchronisation events occur and based on the analysis of time indexes and PNCC magnitude values, a timing synchronisation index used to synchronise receiver timing to transmitter timing is determined. According to a second embodiment, the crosscorrelation function (CF1) based on the PNCC metric (6) is used to decide if synchronisation events occur and based on an analysis of time indexes and PNCC magnitude values using a clustering approach, a timing synchronisation index is determined.