Local Clock Modeling in Discrete-Event Simulation
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Solution Overview
Problem
Existing discrete-event simulators fail to accurately model local clocks across independent systems due to clock drift and offset, limiting their ability to simulate tasks requiring precise clock synchronization and protocol design in sensor networks, as they assume a shared common logical clock reference that does not reflect real-world clock variations.
Innovation Solution
A clock modeling layer is introduced between the discrete event scheduler and other modules, generating a one-to-one relationship between local and logical time using analytical models or empirical data, allowing for the simulation of clock skew and providing utilities for time conversions to maintain causality, which can be implemented in existing simulators like QualNet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shared common logical clock reference is used in discrete-event simulators, then causality of events is maintained, but clock drift and offset between independent systems cannot be modeled accurately
Solution Approach 1:
The patent divides the unified logical clock into separate local clocks for each system, allowing each system to maintain its own independent time reference. This segmentation enables modeling of clock drift and offset between systems while preserving event causality through the mapping layer that translates local clock times to simulation logical time.
Solution Approach 2:
The patent introduces a clock mapping utility as an intermediary layer between local clocks and the simulation logical time. This intermediary performs time conversions and mappings, allowing independent local clocks with drift and offset to be reconciled with the unified simulation timeline, thus maintaining causality while enabling accurate clock modeling.
2Measurement precision
If real hardware platforms are used for clock synchronization experiments, then accurate clock modeling is achieved, but resource consumption and time requirements increase significantly
Solution Approach 1:
The patent creates virtual copies of local clocks within the simulation environment that replicate the behavior of real hardware clocks, including drift and offset characteristics. These virtual clocks are modeled using analytical expressions based on empirical data, enabling accurate clock synchronization simulation without requiring physical hardware platforms.
Solution Approach 2:
The patent uses analytical models with adjustable parameters to represent clock drift and offset behavior. By changing these parameters, the simulation can accurately model different clock characteristics and synchronization scenarios, providing hardware-independent but realistic clock behavior simulation.
3Measurement precision
If independent local clock sources are used for each system, then clock drift and offset can be modeled, but event causality may be violated due to clock inaccuracies
Solution Approach 1:
The patent implements a feedback mechanism through the clock mapping utility that continuously monitors and adjusts the relationship between local clocks and simulation logical time. This feedback ensures that even though local clocks have independent drift and offset, the mapping layer corrects for these variations to maintain proper event causality in the simulation.
Solution Approach 2:
The patent creates a composite time reference system that combines multiple independent local clocks with the unified simulation logical time. The clock mapping utility acts as the binding agent that integrates these separate time references, allowing clock variations to be modeled while ensuring overall causality consistency through the mapping relationship.
Data Source
AI summary
Local clock modeling for a discrete event simulator is described. A local clock generator provides realistic clock characteristics in terms of clock precision and clock drift and clock mapping utilities provide API for other modules and/or protocols in the discrete event simulator to schedule events on local clocks instead of global clock of the simulator.