Time Offset Determination Using Peak-to-Average Ratio
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Solution Overview
Problem
Current methods for determining time offsets in multiple-access communications systems face challenges such as high operation complexity, high implementation costs, and susceptibility to interference like frequency offset and phase noise, particularly in initial ranging signals, leading to alignment issues and increased conflict probabilities during terminal registration.
Innovation Solution
A method that determines time offsets based on peak-to-average ratios of symbols in the time-domain signal received by the head end, using specific formulas to calculate the time offset, which reduces reliance on phase rotation and averaging of phase results, thereby decreasing the number of preambles required in initial ranging signals and enhancing resistance to interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase rotation and averaging of phase results are used to determine time offset, then measurement precision is improved, but operation complexity and implementation costs increase
Solution Approach 1:
The patent changes the fundamental parameter used for time offset determination from phase-based metrics to peak-to-average ratio (PAR) based metrics. This parameter change eliminates the need for complex phase rotation and averaging operations while maintaining determination accuracy, as PAR values can be directly calculated and compared without iterative phase processing
Solution Approach 2:
The patent extracts and utilizes the peak-to-average ratio characteristic of the time-domain signal, which inherently contains time offset information. By focusing on this specific signal characteristic rather than processing the entire phase structure, the method removes unnecessary operational complexity while preserving measurement precision
2Reliability
If more preambles are used in initial ranging signals, then reliability of time offset determination is improved, but device complexity and costs increase
Solution Approach 1:
By switching from phase-based to PAR-based determination, the patent achieves reliable time offset measurement with fewer preambles. The PAR metric provides robust interference resistance inherently, eliminating the need for multiple preambles to achieve statistical reliability through averaging
Solution Approach 2:
The patent converts the potentially harmful effect of interference (frequency offset and phase noise) into a benefit by using PAR values that are inherently resistant to these interferences. This allows reliable determination with minimal preambles, as each preamble provides sufficient reliable information
3Ease of operation
If conventional time offset determination methods are used, then ease of operation is maintained, but susceptibility to interference increases
Solution Approach 1:
The patent changes to using PAR values as the determination parameter, which maintains operational simplicity through direct calculation and comparison while providing inherent resistance to frequency offset and phase noise interferences that plague conventional phase-based methods
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AI summary
A method and an apparatus for determining a time offset are disclosed. The method includes: obtaining, by a device at a head end, a time-domain signal based on a received signal; and then determining a time offset based on values of peak-to-average ratios of a preset quantity of symbols starting from a qth symbol in the time-domain signal, where a peak-to-average ratio of the qth symbol is greater than a preset threshold. A new method for determining a time offset is provided, and takes advantages that the time-domain signal obtained by the device at the head end has stronger capabilities of resisting interference such as frequency offset and phase noise. The method for determining a time offset can be applied both to initial ranging and periodic ranging, so as to ensure that time points at which signals sent by all terminals arrive at the device at the head end are aligned, and ensure normal communication of a multiple-access communications system.