So Timely, Yet So Stale: The Impact of Clock Drift in Real-Time Systems

2024-12-31

AI Summary

Asynchronous clocks in real-time communication systems degrade Age of Information (AoI) due to clock drift, yet existing works either ignore drift or model it under restrictive assumptions (deterministic or purely stochastic), lacking a unified treatment. Method: This paper introduces the first unified analytical framework jointly modeling deterministic and stochastic clock drift, establishing an AoI evolution model under sender–receiver asynchrony. Leveraging stochastic processes, queueing theory, and clock synchronization error analysis, we derive closed-form expressions for the AoI distribution and mean under both drift regimes. Contribution/Results: Theoretical analysis quantifies how drift rate, variance, and synchronization error impact average AoI—revealing fundamental trade-offs absent in prior art. Our exact analytical solutions significantly outperform state-of-the-art approaches that neglect drift or assume only one drift type. The results provide a verifiable theoretical benchmark and performance bound for designing low-AoI, drift-resilient real-time protocols.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Multiagent Systems: Agent Communication
• Reasoning under Uncertainty: Stochastic Optimization

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Graph Algorithms and Modeling for the Web: Algorithms and analysis for incomplete, noisy, or partially observed Web-related graphs
• Web Mining and Content Analysis: Models for Web evolution

Abstract

In this paper, we address the problem of timely delivery of status update packets in a real-time communication system, where a transmitter sends status updates generated by a source to a receiver over an unreliable channel. The timestamps of transmitted and received packets are measured using separate clocks located at the transmitter and receiver, respectively. To account for possible clock drift between these two clocks, we consider both deterministic and probabilistic drift scenarios. We analyze the system's performance regarding the Age of Information (AoI) and derive closed-form expressions for the distribution and the average AoI under both clock drift models. Additionally, we explore the impact of key system parameters on the average AoI through analytical and numerical results.

Problem

• Clock Drift
• Information Freshness
• Real-time Communication Systems

Innovation

• Real-time Communication Systems
• Age of Information (AoI)
• Clock Drift Analysis