Analysis And Optimization Of The Access Mechanism On The IEEE802.11 MAC

Since the 21st century,with the rapid development of wireless communication technology,WLAN which is a kind of high throughput,low cost communication technology has been widely used in our daily life.As the standard of WLAN,IEEE802.11 standard has evolved over the years,and the latest version 802.11ac can reach a speed of 6.9Gbit/s.But with the continuously increasing demand for supermassive data businesses,the performance of the existing system is unable to keep up with the demand.The multiple access technology of MAC layer is one of the key technologies related to improving system performance.The multiple access protocol of the WLAN should be easy to implement,and with high throughput,low latency and fairness.The access protocol of the IEEE802.11ac includes two mechanisms:DCF and PCF.In order to catch the growing demand for data,the access mode of the original standard needs to be improved to promote system throughput.At the same time,new MAC layer access technology requires to be researched for the new WLAN standard 802.11 ax to improve system performance.Firstly,the basic knowledge of IEEE802.11 MAC layer is elaborated in this thesis which including IEEE network topology,frame structure and frame interval.Then the DCF access mechanism based on CSMA/CA is introduced in details.The EDCA and PCF are also briefly introduced.Secondly,the performance of the DCF access mechanism is analyzed and simulated with MATLAB.The result shows that the collision of the site is the biggest factor limiting the system performance under the condition of site dense deployment.And then four improving DCF algorithms based on competition Window updating is simulated,and the pros and cons of each improving algorithm are analyzed.Besides,according to the way that the site judges whether the channel is busy or not in the CCA process,the improving DCF scheme is put forward based on CCA,and simulation results prove that it can effectively reduce the collision probability of site and promote the system throughput.Finally,the packet access method based on RSSI is proposed after the research of 802.11ax.And the implementation of packet access scheme based on RSSI is introduced in detail.which proves that the scheme can effectively reduce the collision probability of the site,increase the system performance through the simulation.