Feedforward temperature compensation in sub-microsecond wireless clock synchronisation

Tight clock synchronisation is vital for timecritical distributed systems, as can be wireless controls in modern industrial settings. There are many approaches to the problem, but the disturbances to reject come invariantly from two sources: the employed communication channel, and the physics of the clocks themselves. We here focus on the latter, and specifically on counteracting the effects of temperature on crystal oscillators—a relevant issue in harsh-environment applications. We present an extension to the FLOPSYNC-2 clock synchronisation scheme, complementing its communicationbased feedback mechanism with a feedforward compensation capable of reducing the maximum synchronisation error during temperature transients by 87% exploiting a temperature to frequency model. Besides helping in heavy-duty applications, the proposed extension allows to reduce the use of the radio channel, thus being useful also when the environment is not an issue but communication is expensive in any sense, most typically as for battery duration.