A secure and fast industrial WLAN system with zero-delay roaming

In this paper, an industrial Wireless Local Area Network (iWLAN) solution to control industrial robots (iRBs) in large-scale factory automation (FA) environment is addressed. In the large-scale industrial network composed of multiple access points (APs), a delay time during roaming from one AP to another AP causes a discontinuation of the control of the iRBs. This roaming delay is usually induced by two processes; 1) scanning for a new AP and 2) authentication at the new AP. In order to avoid roaming delay, we propose a novel access scheme using pre-registration and time-synchronization. In this scheme, all APs operate in same channel with time-synchronization, and each iRBs are pre-registered to every AP before control. The analysis results show that the proposed scheme realizes zero delay, zero communication cost and low storage requirements for roaming.