Control loop optimization - Knowing your environment

Abstract

The variety of applications that require high precision clock synchronization is continuously increasing, and those that traditionally have employed clock synchronization are putting increasingly stringent requirements on the clock synchronization system. This fact necessitates the optimization of all components that counteract the clock drift and timestamp jitter at the slave nodes. This paper focuses on the optimization of the control servo, utilizing oscillator stability measurements. We present a method for oscillator stability measurements with simple sampling instruments and give results for samples of different oscillator classes. We further investigate the oscillator stability under certain adverse environmental conditions. The measurement results are used to calculate optimal control servo parameters, which are verified in real-life measurements of a synchronization system. Constraints like settling time, Packet Delay Variation (PDV), and the physical environment of the oscillator have a major impact on the synchronization quality. Therefore, these constraints have to be carefully evaluated and considered for selecting the optimal oscillator and for designing and tuning the synchronization servo.