Hardware Implementation And Multi-user Precoding Technology Of Ultra-high-speed WLAN

Since the establishment of wireless local network(WLAN)in 1997,it has grown rapidly in recent years and has played an increasingly important role in daily life.At the same time,requirement for its transmission rate is getting higher and higher.As a result,many new technologies have been introduced into WLAN.The new WLAN standard,IEEE 802.11 ac,can achieve a transmission rate of 1 to 7 Gbps on wireless media.To a large extent,it meets people's daily needs.With the increasing demand of wireless LAN devices,the research on ultra-high speed wireless LAN has important practical significance.This thesis studies and designs the precoding module of the ultra-high speed wireless LAN multi-user system from the perspective of hardware implementation based on the IEEE 802.11 ac standard.Furthermore,this thesis realizes a downlink multi-user WLAN system with 80 MHz transmitting bandwidth which has two transmission antennas and two users on the NI-USRP RIO hardware platform.The main work of the dissertation is as follows.Firstly,the multi-user physical layer technology of the IEEE 802.11 ac standard is studied.Taking 80 MHz transmission bandwidth as an example,the physical layer frame structure,baseband data processing flow,and receiver flow for each user are specifically introduced.Secondly,the multi-user linear precoding technology applicable to the IEEE 802.11 ac standard is studied,and different precoding techniques are simulated and compared.The hardware implementation method of block diagonalized precoding is studied in detail,and a method for diagonalizing precoding of QR decomposition block based on Givens rotation matrix multiplexing is proposed,which reduces the hardware implementation complexity and saves the hardware resources.The low-complexity block diagonalized pre-coding module is implemented on the NI-USRP RIO platform,and its correctness is verified by simulation tests.Thirdly,for the optimized precoding module in multi-user precoding applicable to IEEE802.11 ac standard,the hardware implementation method of the geometric mean value decomposition precoding module is studied.The method of geometric mean value decomposition based on double diagonalization is mainly studied.Based on this,an improved dual-diagonalization method based on the Hermitian matrix is proposed to reduce the use of the angle calculation module and the matrix multiplication module and reduce the implementation complexity.At the same time,the hardware design and implementation of the geometric mean decomposition precoding module based on NI-USRP RIO platform are verified and verified by simulation tests.Finally,the NI-USRP RIO platform was introduced.Based on the IEEE 802.11 ac standard,an 80 MHz downlink multi-user system prototype was implemented on the USRP RIO platform with two transmitting antennas and two receiving users per user.Emphasis was placed on the design of the system architecture,the important modules in the system design,and the data communication process.Finally,the constellation test results and the video stream transmission results under the 16 QAM modulation method are shown.