Research And Verification Of The Key Technology For Signal Detection Of 4×4 IEEE802.11ac

The development of wireless communication technology has always been devoted to maximizing the transmission rate and achieving the best transmission reliability in the harsh channel environment and limited spectrum resources.With the galloping development of wireless LAN technology in the last few years,IEEE working group developed the IEEE802.11 ac protocol standard as the fifth generation of WiFi standard in 2013 to improve the data transmission rate to meet the user's demand for throughput.Based on the protocol,the signal detection technology that supports up to four transceiver antennas has been researched and verified in this thesis.The main contents are as follows:Firstly,the research background of the thesis and the research status of MIMO-OFDM signal detection technology are introduced.It is pointed out that the accuracy of channel estimation and the performance of the detection algorithm are the key factors affecting the system performance.Then,the advantages and disadvantages of the MIMO signal detection technology applied to 802.11 ac are clarified intensively,and the theme of this thesis is elicited.Secondly,the impact of the insufficient accuracy of the channel estimation algorithms on system performance is analyzed,which without phase tracking only via the Very High Throughput-Long Training Feild(VHT-LTF)under non-flat and slow fading channels.Then,considering the characteristics of the VHT-LTF preamble and pilot signals of Data Feild in 802.11 ac frame,after the channel estimation value of VHT-LTF is obtained,residual phase tracking and compensation are accomplished using the pilot signal inserted in the Data Feild to obtain the channel estimation value of the Data Field.The above two channel estimation algorithms are simulated and compared follow.The simulation results show that the improved residual phase tracking algorithm improved the overall performance of the system.Thirdly,the zero forcing linear detection algorithm and the minimum mean square error linear algorithm are simulated,followed by their performance of analysis and comparision.It shows the minimum mean square error detection algorithm has good performance at low signal-to-noise ratio and converges to zero forcing linear detection at high signal-to-noise ratio.But considering the high implementation complexity,the zero-forcing detection is choosen as initial detection algorithm.Finally,based on the design of the 4×4 IEEE802.11 ac Wi Fi prototype,the signal detection scheme and the logic implement with FPGA are designed.On the hardware platform with 4 transmit and 4 receive 802.11 ac transceiving systems,the function of signal detection module is verifiedwe,and the packet error performance of link of QPSK,64 QAM,256QAM modulation is tested under different scenarios.The improved residual phase tracking channel estimation combined with the zero forcing linear detection algorithm can be applied to the design of 4 ×4 IEEE802.11 ac WiFi prototype to complete MIMO signal detection,and achieve performance requirements in the test of cable direct connection and antenna point-to point scenarios,which provides a theoretical and engineering reference for the research and promotion of the next generation wireless LAN based on IEEE802.11 ac protocol.