The Research And System Implementation Of Multi-carrier Transmission In Millimeter-wave Communication

In the era of mobile internet,with the popularization and rapid growth of smart terminals,the demand for low-latency,high-rate,and large-capacity wireless communication systems has become increasingly strong.The existing wireless communication system is limited by spectrum resources,and it is difficult to improve the transmission rate.Millimeter-wave multicarrier wireless communication systems have become a research hotspot in current wireless communications because of its rich spectrum resources,higher spectrum utilization and Antimultipath capability.The high bandwidth and sampling rate of the millimeter-wave system also brings many challenges to the system implementation.In September 2012,the IEEE established Task Group TGaj to develop next-generation WLAN standards specifically for China's millimeter-wave band.Based on the NI-PXIe millimeter-wave platform,a millimeter-wave OFDM system based on the IEEE 802.11aj(45GHz)standard was designed and built to study and analyze key technologies in the system.Based on the NI-PXIe millimeter-wave platform,a millimeter-wave OFDM system based on the IEEE 802.11aj(45GHz)standard was designed and constructed.The key technologies in the system were studied and analyzed.The main work of the thesis is as follows:1.The background knowledge of millimeter-wave WLAN systems was reviewed,and IEEE 802.11aj(45GHz)physical layer characteristics,system parameters,and baseband processing related technologies were studied.After analyzing and introducing the NI-PXIe millimeter-wave system platform and evaluating the hardware platform resources,including storage capacity,computing capacity,data interaction capability,support bandwidth and clock,etc.,and considering the performance requirements of each module in the millimeter-wave OFDM system the system hardware architecture was designed.In the system hardware implementation,a good system architecture can guarantee the stability and correct operation of the system.2.Millimeter-wave system with ultra-high bandwidth and sampling rate,the traditional Lab VIEW FPGA hardware design method based on serial data stream can not meet the system requirements.In the system design,a parallel processing design scheme for millimeter-wave OFDM systems was proposed.The scheme performed serial-toparallel conversion of the data before baseband processing at the transmitter.After baseband data parallel processing,parallel-to-serial and digital-to-analog conversion were utilized by high speed DAC.The receiver also uses a high-speed ADC to perform serial-to-parallel and analog-to-digital conversion on the data.After baseband data parallel processing,the data is parallel-serial converted,and the original data is recovered.This solution can effectively reduce the baseband processing FPGA clock requirements and improve the system transmission rate.3.In order to solve phase noise and frequency offset sensitivity in millimeter-wave OFDM systems,a T/2 fractional-spaced frequency domain equalization method for millimeterwave OFDM systems is proposed.The data after synchronization is spaceing-extracted and the estimated fractional-spaced channel matrix is used to FS-FDE.The performance of FS-FDE algorithm and common equalization algorithm is compared and analyzed by matlab system simulation.The simulation and hardware measurement results show that FS-FDE can effectively use the system upsampling diversity gain to effectively reduce system phase noise interference and improve system BER performance.4.A phase correction design scheme is proposed for the residual phase deviation of the signal after equalization in the millimeter-wave OFDM system.The phase offset compensation factor was estimated by transmitting and receiving pilot subcarriers to compensate the data.The performance of phase correction algorithm was analyzed through matlab simulation.The comparison of hardware measured data before and after phase correction constellation performance shows that this algorithm can effectively improve the constellation rotation phenomenon caused by residual phase deviation.5.A millimeter-wave OFDM real-time video communication system was designed and developed based on NI-PXIe millimeter-wave platform.With reference to the IEEE 802.11aj(45GHz)standard packet structure and system parallel design scheme,the system frame format was designed.In the system implementation,a Lab VIEW FPGA hardware design scheme based on timing control was proposed.The scheme generated the timing control signal according to the frame header and frame format before transmitting and receiving the baseband processing.The baseband processing module performed the corresponding process by judging the timing control signal.Compared with the traditional FPGA hardware design scheme based on FIFO data storage,the timing control scheme can effectively save FPGA storage resources and improve system reliability.The system baseband processing implemented modules such as scrambling/descrambling,constellation point mapping/demapping,IFFT/FFT,synchronization,channel estimation and equalization,and phase correction.Through real-time video demonstration,the system was tested and analyzed in terms of transmission rate,constellation,bit error rate,EVM,and video clarity.The test results show that the millimeter-wave OFDM system not only has good real-time performance and stability,but also has ultra-high transmission rate and low bit error rate.