| In this paper,the scheme design of the adaptive wireless transmission system for uhd video is carried out,which is based on the Multi-Input Multi-Output?MIMO?technology and Orthogonal Frequency Division Multiplexing?OFDM?technology,combined with wireless technologies such as time-frequency synchronization,signal detection,channel estimation and SNR estimation.The research is carried out as follows.Firstly,the application scenes of large performance venues are introduced,and the uhd video parameters are analyzed based on 4K and 8K videos,at the same time,the output video code rate range of AVS2 video encoder is determined to be 36Mbps50Mbps,which is used as the transmission rate index.Then,based on the channel model of application scenarios,the discussion and analysis of MIMO and OFDM technologies are introduced,and the frame format and OFDM parameters are analyzed and designed in detail.Secondly,the influence of time-frequency unsynchronization on system performance in OFDM system is analyzed,three classical synchronization algorithms for OFDM systems are studied and simulated,then the characteristics of Constant Amplitude Zero Autocorrelation Code?CAZAC?were analyzed,and for the OFDM and MIMO-OFDM system models,the related training sequence structure was designed based on CAZAC sequence and the corresponding synchronization scheme was designed.The simulation results of MIMO-OFDM synchronization scheme based on CAZAC sequence show that when the signal-to-noise ratio is-6dB,the stable symbol timing can be achieved,when the signal-to-noise ratio is 0dB,the acquisition probability of integer frequency-doubling bias is 1,when the signal-to-noise ratio is 10dB,the mean square error of fractional frequency-doubling bias estimation is less than10-5,the validity of the design scheme is verified.Then,the MIMO model of the system is analyzed in combination with the application scenarios,according to the different number of users,the MIMO model of the system can be equivalent to 2?4 and 4?4 MIMO system,then the complexity analysis and program simulation of MIMO signal detection algorithm are carried out,and the ZF detection algorithm is selected as the system MIMO signal detection algorithm,the channel estimation scheme of 2?4 and 4?4 MIMO systems is designed based on block pilot frequency and orthogonal matrix,simulation results show that the performance loss of ZF detection using channel state information obtained by channel estimation algorithm and complete channel state information is only 2.5dB,the validity of the design scheme is verified.Finally,the adaptive scheme of uhd wireless video transmission system is designed,focusing on the code rate adaptation module and the SNR estimation module,and the simulation model is established based on Matlab to complete the simulation of the whole system under the application scene channel model,according to the simulation results,the adaptive parameter table is determined.According to the adaptive parameter table,when the total system has access users of 10 and 20,the reliability transmission that meets the transmission rate requirement can be completed under the channel conditions of SNR?14dB and SNR?17dB respectively. |
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