Design And Implementation Of Industrial Wireless Communica-tion Protocol Stack Based On IEEE802.11 Physical Layer

In recent years, wireless technology has been widely used in industrial field.Especially in industrial process control field, there have been mature international standards. At the same time, with the introduction of the German "Industry 4.0" concept,and the formation of the China and Germany "industry 4.0 Promotion Union”, whether in domestic or international, we have the concept of the digital factory and smart manufacturing advanced to the hot point. In the context, combining the performance requirements that factory automation need for high speed, high real-time, high reliability and other properties, we developed and implemented a high-speed real-time wireless communication protocol stack based on IEEE802.11 physical layer.Based on the needs analysis of wireless communication network of factory automation, we determine the industrial wireless communication protocol stack’s structure.The structure is divided into five layers, from bottom to top in turn is the physical layer,data link layer, network layer, transport layer and application layer. Wherein, in order to meet the high-speed performance of industrial wireless communication, we use the IEEE802.11 physical layer in physical layer. Meanwhile, to meet the industrial real-time communication and reliability requirements, we use the TDMA channel access technology and automatic ACK mechanism in data link layer. Then, based on the characteristics of TDMA channel access technology, we determine three key technologies that need to be considered in the implementation process of the industrial wireless communication protocol stack: MAC delay control, high precision time synchronization algorithm, and TDMA scheduling implementation. In the MAC delay control implementation, in order to ensure the communication delay’s certainty, we disabled the mechanisms thar affect MAC delay, including physical carrier sensing mechanism, virtual carrier sense mechanism,backoff mechanism, adaptive rate mechanism, etc. In terms of high-precision time synchronization algorithm, we proposed a one-way time synchronization algorithm based on linear regression, the actual test results show that the synchronized algorithm’s accuracy can be controlled within the 25 us. In TDMA scheduling algorithm implementation, weproposes a TDMA scheduling algorithm based on dynamic timeslot allocation, and the algorithm was realized in the Linux kernel.The industrial wireless communication protocol stack was ported to the wifi wireless router development board, and built a single-hop star topology network. Based on the test platform, function and performance of the protocol stack were tested respectively. The test results show that the protocol stack’s performance is better.