Transformed EPA protocol on WLAN

As a member of real-time Ethernet family, EPA is the first independent intellectual property field bus national standard of China and listed as Common Profile Family 14(CPF14) of IEC 61784-2 real-time Ethernet application principles. It has been applied in many automation control fields successfully such as medicine and chemical industry. On the other hand, the wireless LAN standards IEEE802.11 have been established for several years and after fast growing, it is now the recognized standard around the world and has been expanded so as to include important features to ensure its compatibility in industrial applications. How to combine EPA with WLAN is important so that we can extend EPA to some applications where it is not convenient to layout. The deterministic communication mechanism of EPA is on the assumption that the data communication has no disturbance and no one data package will be lost. This is not suitable in wireless environment. So a master-slave mode is introduced to realize deterministic scheduling, which is proved to be reliable and robust in practice. Instead of IEEE1588, an upgraded method basing on TSF is used to achieve clock synchronization. Not only can it cut the shortage of TSF but also it needn´t extra message to increase network payload. A test and the test result are shown in article at last and the reason of error is also analyzed.