Jitter-Compensated VHT and Its Application to WSN Clock Synchronization

Abstract

Abstract-Accurate and energy-efficient clock synchronization is an enabler for many applications of Wireless Sensor Networks. A fine-grained synchronization is beneficial both at the system level, for example to favor deterministic radio protocols, and at the application level, when network-wide event timestamping is required. However, there is a tradeoff between the resolution of a WSN node's timekeeping device and its energy consumption. The Virtual High-resolution Timer (VHT) is an innovative solution, that was proposed to overcome this tradeoff. It combines a high-resolution oscillator to a lowpower one, turning off the former when not needed. In this paper we improve VHT by first identifying the jitter of the low-power oscillator as the current limit to the technique, and then proposing an enhanced solution that synchronizes the fast and the slow clock, rejecting the said jitter. The improved VHT is also less demanding than the original technique in terms of hardware resources. Experimental results show the achieved advantages in terms of accuracy.

TDMH-MAC: Real-Time and Multi-hop in the Same Wireless MAC

“…When the data load is exactly zero, for short tile durations and fully connected networks, where in every uplink slot a frame is overheard, the average current consumption can reach 0.72mA. For long tile durations and a sparse network, where in only 10% of uplink slots a frame is overheard, the consumption can be as low as 0.12mA, most of which is due to the FLOPSYNC-VHT timebase [3] necessary to keep synchronization while in deep sleep. When the data slots used grows to just 10%, the average current in the two aforementioned cases becomes 2.69mA and 2.17mA, showing how the dominant part of the consumption is due to data transmission.…”

Clustering-based solutions for energy efficiency, adaptability and resilience in IoT networks

“…The use of grid voltage signals enables the solution to achieve good accuracy as well as scale for long distances. A combination of a high-speed and low-speed clock called VHT (Virtual High-resolution Timer) is used to achieve synchronization of the high-speed clock with the low-speed one [133]. The authors propose to selectively turn o↵ the high-speed clock during sleep and as the low-speed clock is always turned on.…”

“…A failure of the source would lead to the failure of the overall synchronization. Other solutions add to hardware overhead with specialized circuits and timers to reduce the jitter from the existing hardware clocks [133,134].…”