An improved precision time protocol for industrial WLAN communication systems

In this work, an improved Precision Time Protocol (PTP) used to synchronize clocks in industrial Wireless Local Area Network (WLAN) communication systems is addressed. In order to enhance the accuracy of the PTP synchronization, we first provide an approach to remove the drift factor of frequency of crystal oscillators on the master and slave clocks without any additional message exchanges added to the conventional PTP protocol. Then, we show an approach to reduce the asymmetric delays caused by the imbalanced hardware processing latencies between downlink and uplink paths. The simulation results show that the first and second approaches can improve the synchronization accuracy about 30% and 50%, respectively, as compared with the conventional PTP protocol. In addition, the PTP message exchanges are aggregated to reduce transmission overheads for the fast communication systems.