Research On Synchronization Mechanism In Wireless Lan

With the process oriented industry standard wireless communication applications,"China Manufacturing 2025" and "Internet +" is put forward,the industrial process automation wireless network has aroused widespread concern in academia and industry.At present,in the design of industrial communication systems,a common design scheme is to use "hybrid wired wireless industrial network,wired networks usually use real-time Ethernet,wireless communication technology and the existing,including three industrial process automation wireless communication standards,is only applicable to industrial automation process low,unable to meet the real time high speed wireless network factory automation and high sampling rate.Therefore,in the application of factory automation for high speed control,wireless communication technology is still facing huge technical challenges.The wireless LAN based on the IEEE 802.11 protocol is comparable to the transmission speed of Ethernet,and the Wi-Fi device can provide high sampling rate guarantee.However,due to the randomness of the transmission delay in the MAC layer of the IEEE 802.11 protocol,it does not have the ability to operate in real time.The purpose of this study is in the IEEE 802.11 on the basis of the hardware,complete the design and implementation of MAC layer TDMA mechanism based on MAC layer transmission delay guarantee deterministic clock synchronization algorithm,and put forward a new implementation of the wireless LAN,Station clock and AP clock,to ensure the accuracy of the TDMA time slot scheduling,so as to meet the real-time high speed wireless factory automation the requirements of the network.In order to achieve the purpose of this paper,based on the full analysis of the research on data transmission real-time and clock synchronization technology in WLAN,we have completed the following works:(1)In this paper,the synchronization module is added to the MAC layer of the TDMA mechanism.The module ensures the Station clock in the WLAN is aligned with the AP clock,and provides accurate time information to the TDMA slot scheduling.(2)Aiming at the low synchronization accuracy of TSF mode in wireless LAN,a clock synchronization algorithm based on improved local weighted linear regression(CS-ILWLR)is proposed.The algorithm is characterized by reduced matrix operation and other measures to reduce the clock conditioning consumption Time.Experimental results show that the synchronization accuracy of CS-ILWLR algorithm is higher than TSF mode,and the synchronization error can be reduced to 27 microseconds.(3)This paper presents a two-phase clock synchronization algorithm(TSCSA),that is,the data acquisition phase synchronization and least-squares linear regression synchronization.TSCSA algorithm dynamically updates the sample data during operation,and selects the latest data for fitting calculation.Experiments have been conducted on the real-time Wi-Fi platform and the results show that the TSCSA algorithm has less than 23 microseconds of synchronization error.(4)Because of the drift of the local clock at Station during the two clock calibration intervals,this paper proposes a clock drift compensation algorithm(CDCA)based on the TSCSA algorithm and uses an exponential smoothing method to predict the clock drift in the next cycle,To compensate for the purpose of drift from the clock.TSCSA algorithm combined with the CDCA algorithm to obtain a multi-phase compensation based on the clock synchronization algorithm(CS-MSC).By testing the CS-MSC algorithm,the results show that the CS-MSC algorithm achieves synchronization errors below 21 microseconds.