Randomized Slave Time-Stamp Clocks for Packet Sync Precision
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Solution Overview
Problem
Network packet communications face challenges in achieving precise time and frequency alignment due to random transit delays and systematic time-stamp granularity errors, which are difficult to filter out using traditional methods.
Innovation Solution
The implementation of randomized slave time-stamp clock rates that differ from master time-stamp clock rates, using techniques such as spread spectrum or delta-sigma modulation, to reduce systematic time-stamp granularity errors by spreading noise spectral characteristics over a wide Fourier-frequency range, making errors easier to filter out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional time-stamp clocks with fixed granularities are used in slave devices, then time-stamping is simple and deterministic, but systematic granularity errors cannot be filtered out due to random transit delays
Solution Approach 1:
The slave time-stamp clock rate is made dynamic by randomly varying it around a nominal value, rather than keeping it fixed. This randomization transforms the systematic granularity error into a stochastic process that can be filtered out through averaging multiple measurements, thereby improving time-stamp precision while accepting increased clock mechanism complexity
Solution Approach 2:
The clock rate parameter of the slave time-stamp clock is changed from a fixed value to a randomly varying value. By modulating the clock rate parameter stochastically, the patent converts deterministic granularity errors into random errors that can be reduced through statistical filtering, improving measurement precision at the cost of additional control complexity
2Measurement precision
If slave time-stamp clock rate is randomized to reduce systematic errors, then synchronization precision improves, but device complexity and difficulty of operation increase
Solution Approach 1:
The slave device autonomously generates and applies random variations to its own time-stamp clock rate without requiring external coordination or configuration from the master device. This self-service approach maintains synchronization precision improvements while minimizing operational complexity by eliminating the need for complex inter-device configuration protocols
Solution Approach 2:
The patent employs feedback mechanisms where the slave device measures the actual transit delay variations and uses this information to adjust its randomized clock rate accordingly. This feedback loop enables the system to maintain high synchronization precision while automatically adapting to network conditions, reducing the need for manual configuration and intervention
3Measurement precision
If fixed clock rates are used in master and slave devices, then system operation is simple, but systematic time-stamp granularity errors persist and cannot be filtered
Solution Approach 1:
The slave device performs periodic time-stamping operations using its randomized clock rate and periodically filters the resulting time-stamp measurements to remove granularity errors. This periodic approach balances the processing overhead with the need for accurate synchronization, maintaining time-stamp accuracy while managing computational resources efficiently through regular rather than continuous processing
Solution Approach 2:
The patent applies partial randomization to only the time-stamp clock rate rather than randomizing all clock signals in the system. This selective approach reduces the overall processing overhead while still achieving the goal of eliminating systematic granularity errors in time-stamps, improving time-stamp accuracy without excessive computational burden
Data Source
AI summary
Systems and methods are disclosed for utilizing slave (receive) time-stamp clock rates that are different from master (sender) time-stamp clock rates to randomize and thereby reduce systematic time-stamp granularity errors in the communication of network packets. The slave (receive) time-stamp clock rate for some embodiments is set to be a fixed value that has a relationship with the master (sender) time-stamp clock rate such that the ratio of the slave (receive) clock rate to the master (sender) clock rate is a rational number. Other embodiments use a time-varying frequency for the slave (receive) time-stamp clock rate to randomize the slave (receive) time-stamp clock with respect to the master (sender) time-stamp clock. Additional time-stamps can also be generated using a slave (receive) time-stamp clock having a rate set to equal the rate of the master (sender) time-stamp clock signal. Further spread spectrum and/or delta-sigma modulation techniques can be applied to effectively randomize the slave (receive) time-stamp clock.