Receiver Resampling Control for Stable Symbol Timing Synchronization
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Solution Overview
Problem
Existing communication systems face challenges in maintaining stable synchronization between transmitting and receiving devices, especially when clock frequencies are asynchronous, leading to difficulties in correcting symbol phase differences that accumulate over long periods of symbol transmission.
Innovation Solution
A receiving device is designed with a resampler to convert the sampling rate of the reception signal and an equalizer for adaptive equalization, along with a correlation calculator to calculate the correlation function between the signals and a rate controller to adjust the sampling rate, enabling stable synchronization regardless of the communication signal format.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an equalizer that realizes fractionally spaced equalization is used to correct symbol timing difference, then the equalizer can output a signal synchronized with symbol timing, but the correctable difference in symbol phase is limited and stable synchronization cannot be maintained for continuous demodulation of many symbols
Solution Approach 1:
The invention segments the clock frequency adjustment function from the equalizer by introducing a separate resampler. The resampler handles the clock frequency adjustment based on correlation function calculations, while the equalizer focuses on equalization tasks. This segmentation allows each component to specialize, enabling the resampler to maintain stable synchronization over long periods while the equalizer maintains timing accuracy.
Solution Approach 2:
The invention introduces a correlation calculator as an intermediary component that calculates the correlation function between the input signal and equalized signal. This correlation function serves as a mediator to determine the optimal sampling rate conversion ratio, enabling indirect measurement and adjustment of clock frequency differences without directly measuring symbol timing.
2Measurement precision
If a known sequence is used to detect symbol timing for adjusting clock frequency, then timing detection can be performed, but this method cannot be applied when the communication signal format does not include a known sequence
Solution Approach 1:
The invention enables the signal itself to serve as the reference for timing detection by calculating the correlation function between the input signal and the equalized signal. This self-service approach eliminates the need for external known sequences, allowing the system to adapt to any communication signal format while maintaining accurate symbol timing detection.
Solution Approach 2:
The correlation-based timing detection method provides universal applicability across different communication signal formats. By using the correlation function between input and equalized signals, the system can detect symbol timing whether the signal contains known sequences, unknown data sequences, or multiplexed formats, making the solution universally compatible.
3Ease of operation
If the clock frequencies of transmitting and receiving devices are not synchronized, then the receiving device can operate independently, but a difference in symbol timing occurs that accumulates over time
Solution Approach 1:
The invention implements a feedback mechanism where the correlation function between the input signal and equalized signal is continuously calculated and used to adjust the sampling rate conversion ratio in the resampler. This closed-loop feedback enables the receiving device to independently compensate for clock frequency differences and maintain accurate symbol timing without requiring synchronization with the transmitting device.
Data Source
AI summary
A receiving device includes: a resampler to convert a sampling rate of a reception signal, and output a first signal that is a signal having been subjected to sampling rate conversion; an equalizer to perform an adaptive equalization process using the first signal as an input, and output a second signal that is a signal having been subjected to the adaptive equalization process and having a sampling rate that is an integer fraction of an input signal; a correlation calculator to calculate a correlation function between the first signal and the second signal; and a rate controller to control a rate conversion ratio for sampling rate conversion in the resampler on a basis of the correlation function.