Fine Time Measurement based Time Synchronization for Multi-AP Wireless Industrial Environments

In Industrial environments, such as factories, equipment are often connected through Ethernet or its complementary Time Sensitive Networking to support critical applications that require low latency and low jitter in the order of milliseconds. To meet these requirements, precise time synchronization across all wired devices is typically achieved using the Precision Time Protocol (PTP) at the Local Area Network (LAN) level. Although PTP can synchronize devices across wireless networks, Wi-Fi has more effective synchronization mechanisms, like Fine Time Measurement (FTM) that can achieve precise and tight synchronization. As new wireless standards like Wi-Fi 6/7 are integrated into industrial networks, the number of wireless devices in these networks is increasing. It is essential to consider new functional-ities, such as multi access point (AP) coordination, which require precise time synchronization. Aiming at contributing to the time synchronization solution across multi-AP industrial internet of things (IIoT) environments, this paper proposes an approach based on multi-level hierarchical methodology to synchronize the devices. It provides a method for selecting the best FTM Responder to distribute time when multiple FTM responders and initiators are present in the network. The evaluation of the proposed methodologies indicates that it successfully synchronizes all devices within the network, and the best FTM responder selection algorithm performs as expected.