High Precision Time Synchronization on Wi-Fi based Multi-Hop Network

Precise time synchronization amongst network devices is a basic requirement for time critical applications. Despite that time synchronization is a well-established functionality in the wired network domain, its wireless counterpart is very basic or even non-existing. This is because commercial off-the-shelf (COTS) wireless chipsets still focus on basic network connectivity for consumer applications, hence no dedicated software/hardware features are required for time-bounded services in professional wireless environments. This work leverages on openwifi - an opensource Wi-Fi chip design based on Software-Defined Radio (SDR), by adding the support of hardware timestamping in openwifi to support precise time protocol (PTP) application. In addition, openwifi Access Point (AP) is connected to nodes in wired network through a TSN capable switch, and synchronization offset between devices in wired and wireless network is measured. Next, the measurement is done with the same setup in wired network but replacing openwifi by COTS Wi-Fi devices. We observe the synchronization offset with COTS is 10(4) fold larger than the offset achieved with openwifi. The experiment setup is in w-iLab.t, an open testbed infrastructure freely accessible for the academic wireless research community.