Design And Implementation Of TDMA Protocol On IEEE802.11 Hardware

Along with the development of Internet of things(IoT)and "Internet plus",a group of emerging industries are coming out.This is making our life better,but also bringing us a lot of technical challenges,among them,the network communication technology is most urgent.Traditionary,IEEE802.11 and IEEE802.15.4 protocol is widely used in the short distance communication field.Wi-Fi equipment is the typical product that based on the IEEE802.11,it has high transmission rate and large distance,thus it has been widely used in civilian areas.But the MAC layer of IEEE802.11 adopt the CSMA/CA mechanism,which determines that it can't guarantee real-time of transmission,however it's a key technical indicator of IoT.IEEE802.15.4 protocol guarantee the high reliability of data transmission,but the transmission rate can only reach 250kbps,it's now widely in industrial control field.The data transmission in TDMA protocol of the data is only controlled by clock,so different nodes wouldn't transmit data at the same time,it's widely considered as a good way solve the problem of lack of real-time of Wi-Fi.To meet high speed and high real-time communication demands in the hybrid network,we designed and implanted the TDMA protocol on the IEEE802.11 platform.What's more,most of the data in the network don't have too much need of real-time transmission;so,when taking different transmission type and making full use of the hardware platform in to consideration,we designed a new data transmission scheduling mechanism.According to the current time slot type,this scheduling mechanism can select better way to transmit.The main contributions of this paper are listed in the below:(1)we studied the CSMA/CA mechanism which is defined in the MAC layer of IEEE802.11 protocol,analyzed the problems causing data transmission delay uncertainty,and fixed it in the open source wireless network card driver.On the basis of the above process,we firstly designed the TDMA protocol on IEEE802.11 hardware platform,analyzed the clock synchronization,time slot scheduling,slot size,and other important parameters.Then we compiled the changed driver to the Linux kernel and transplanted onto the development board.In the library environment,we certificated the TDMA protocol on IEEE802.11 hardware,and tested its transmission delay performance,reliability,etc.The experimental results show that 95.4%of short frame and 89.97%of long frame can sent completely within 2ms,transmission delay is much lower than the original IEEE802.11 protocol.(2)There are so many different types of data in hybrid wireless network,they have different transmission requirements,in view of it,we designed a new scheduling mechanism which mixes different transmission mechanism.The new mechanism ensures the timely transmission of real-time data,and can also adopt CSMA/CA mechanism to transfer non-real-time data frames.Experiments showed that the hybrid scheduling mechanism can switch the transmission mechanism according to the time slot type,showing the good performance.