Research On MU-MIMO Transmission Access Technology In WiFi System

Wireless communication is almost ubiquitous in people's lives.Wifi is playing an irreplaceable role in human life.In 2004,MIMO technique was introduced to the IEEE 802.11n standard.The detection of receiving signals is an important part to the performance of MIMO system.And good detection algorithms have the characteristics of low computational complexity and good error rate performance.Thus how to improve the performance has become particularly important.In the IEEE 802.11 standard,another important factor affecting the performance of wireless LAN is access technology.Therefore,the research of access technology plays a key role in improving the performance of wireless network.In this thesis,we first introduce several existing MIMO detection algorithms in detail,and analyze and simulate the existing multi-feedback MIMO detection algorithm based on SIC(successive interference cancellation)in the literature.In the MF-SIC algorithm with shadow area constraints(SAC),an interference cancellation is achieved by introducing constellation points to combat the error propagation in decision feedback loops.On the basis of multi-feedback algorithm,this thesis studies a multi-feedback improved algorithm,which uses a recursive method to reduce the error propagation and improve the error performance.Secondly,for multi-user access,we study the multiuser MIMO access scheme,and analyze the scheme in theory.The corresponding control frame is improved,based on Markov chains is proposed to evaluate the performance of the proposed protocol.Obtained results show notable system performance compared to Single User transmission.On the basis of CSMA/CA,an asynchronous multiuser access scheme is studied.The scheme allows multiple users to be accessed simultaneously in one channel by improving the frame format.The throughput performance of the scheme is simulated.Comparing the performance of asynchronous multiuser access scheme and multiuser MIMO access scheme,it is revealed that the performance of asynchronous access scheme is better than that of multiuser MIMO transmission scheme.