Hybrid Network Time Protocol for Clock Synchronization
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Solution Overview
Problem
Existing clock synchronization methods in distributed networks face challenges with robustness, stability, and convergence speed, especially under asynchronous communication and varying network topologies, and are not effective in handling noise and hardware tolerances.
Innovation Solution
A distributed hybrid algorithm using hybrid state-feedback that synchronizes clocks by estimating skew parameters and adjusting clock rates, ensuring exponential convergence and robustness even with intermittent information, and is adaptable to both synchronous and asynchronous communication protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional NTP or reference-based clock synchronization algorithms are used, then clock synchronization can be achieved in ideal settings, but robustness deteriorates when communication delay, noise, or jitter is present
Solution Approach 1:
The patent implements a feedback mechanism where each node continuously monitors its clock skew relative to neighbors and adjusts its clock rate accordingly. The hybrid algorithm uses feedback from both synchronous periodic exchanges and asynchronous event-triggered communications to maintain synchronization despite delays and noise, making the system robust against communication imperfections
Solution Approach 2:
The patent employs dynamic clock adjustment where nodes adaptively change their clock rates based on real-time skew measurements. The algorithm transitions between synchronous and asynchronous communication modes dynamically, adjusting the synchronization strategy based on current network conditions to maintain robustness under varying delay and noise conditions
2Productivity
If simple reference-based synchronization algorithms are used, then implementation is straightforward, but convergence speed deteriorates and exponential convergence cannot be guaranteed
Solution Approach 1:
The hybrid algorithm uses continuous feedback from clock skew measurements to drive exponential convergence. By combining periodic synchronous feedback with event-triggered asynchronous feedback, the system achieves faster convergence than traditional methods while maintaining exponential convergence guarantees through adaptive rate adjustment based on real-time skew information
Solution Approach 2:
The patent implements preliminary clock rate adjustment based on predicted skew trends before actual synchronization events occur. Nodes proactively adjust their clock rates based on historical skew data and neighbor information, reducing the time required to achieve synchronization and accelerating convergence
3Adaptability or versatility
If centralized NTP algorithms are used, then clock synchronization can be maintained, but adaptability deteriorates when network topology changes or communication is lost
Solution Approach 1:
The patent segments the centralized NTP architecture into distributed autonomous nodes that each independently maintain synchronization. Instead of relying on a central server, each node runs the hybrid algorithm locally, using segmented feedback from neighboring nodes to adjust its clock. This segmentation provides adaptability to topology changes while maintaining synchronization stability through distributed consensus
Solution Approach 2:
Each node in the network performs self-service synchronization by autonomously measuring its skew, calculating adjustments, and modifying its clock rate without external intervention. The hybrid algorithm enables nodes to self-adjust based on local observations and neighbor communications, providing adaptability to topology changes while maintaining reliability through decentralized decision-making
4Ease of operation
If hardware clocks with quartz-crystal or MEMS oscillators are used, then portable and distributed clocking is enabled, but manufacturing precision deteriorates due to oscillator frequency variability
Solution Approach 1:
The hybrid algorithm compensates for manufacturing variations in oscillator frequency through continuous feedback from clock skew measurements. Each node monitors its drift relative to neighbors and adjusts its clock rate dynamically, eliminating the need for precise manufacturing while maintaining synchronization across distributed hardware clocks
Solution Approach 2:
The patent dynamically changes the operational parameter of clock rate for each node based on measured skew. By allowing each hardware clock to operate at a slightly adjusted rate rather than a fixed manufactured rate, the system compensates for manufacturing imprecision and achieves synchronization across diverse oscillator implementations
Data Source
AI summary
A distributed hybrid algorithm that synchronizes the time and rate of a set of clocks connected over a network. Clock measurements of the nodes are given at aperiodic time instants and the controller at each node uses these measurements to achieve synchronization. Due to the continuous and impulsive nature of the clocks and the network, we introduce a hybrid system model to effectively capture the dynamics of the system and the proposed hybrid algorithm. Moreover, the hybrid algorithm allows each agent to estimate the skew of its internal clock in order to allow for synchronization to a common timer rate. We provide sufficient conditions guaranteeing synchronization of the timers, exponentially fast. Numerical results illustrate the synchronization property induced by the algorithm as well as its performance against comparable algorithms from the literature.