Research On MIMO Fading Channel Of Near Space High Altitude Platform

The near-space high-altitude platform communication system combines the advantages of terrestrial and satellite communication systems,has many advantages such as large coverage,low delay,and easy device update,and has broad application prospects in the fields of emergency communications,scientific research,and military.Therefore,in the context of higher and higher communication capacity requirements,near-space high-altitude platform MIMO systems have become the most potential complementary or collaborative solution for deploying the next-generation high-capacity communication systems.Due to the different channel propagation conditions and the limitation of platform size,the performance of MIMO technology in high-altitude platform communications can't be inferred directly from the performance of MIMO in traditional terrestrial communications.Therefore,the application of MIMO technology in high altitude platforms remains to be studied.The establishment of the channel model is the basis for the research of high-altitude platform MIMO systems.Therefore,the development of a more accurate and efficient HAP-MIMO channel simulation model remains an important research topic.For the problem of the inaccurate description of the channel environment,the lack of correlation considerations and the need for more effective resistance measures for shadowing in low elevation angle regions existing in the high-altitude platform MIMO channel modeling,This paper further studies the applicability and effectiveness of MIMO technology in high altitude platform communication system based on the modeling of high altitude platform channel.The main contents and contributions of this paper are as follows:Aiming at the problem of the inaccurate description channel of the channel environment and the lack of correlation considerations of the existing near space high-altitude platform MIMO fading channel models,a high-altitude platform spatial diversity MIMO channel simulation model that fully considers the sub-channel correlation is proposed.Based on the spatial correlation function given by the statistical model based on three-dimensional geometric distribution of high-altitude platform,a calculation method for the spatial correlation coefficient of Rice channel is proposed.Combined with the channel spatial correlation function,the effect of channel propagation parameters on the channel spatial correlation is simulated and analyzed.The simulation results can provide guidance for selecting the parameters for engineering applications.Through simulation,the channel capacity of the spatial diversity MIMO channel model in three typical environments and the effect of changing the antenna spacing on the channel capacity under the same environment are evaluated,and the antenna spacing of the transmitting end needed to obtain a good spatial diversity gain is given.Aiming at the problem of the existence of severe shadowing in the low elevation region and the problem that the existing model can not describe the high altitude platform channel accurately,a dual antenna diversity strategy is proposed.Combined with the advantages of the deterministic channel model and the statistical channel model,a new dual antenna diversity of high-altitude platform MIMO channel model is proposed.First,a multi-state large-scale fading model and a small-scale fading model are generated by using two-state Markov state transition model and Loo model.Second,use the existing channel measurement data and theoretical models to calculate polarization diversity and spatial diversity correlation coefficients.Aiming at the problem of the lack of correlation coefficient in the existing dual diversity channel,a channel correlation coefficient extension method that can effectively reduce the computational complexity and the actual measurement cost is proposed.Then,the calculated correlation coefficients are superimposed on the large-scale and the small-scale fading model to generate the correlation between the sub-channels,and the related high-altitude platform dual antenna diversity MIMO channel model is obtained.Finally,the correctness and effectiveness of the proposed model are verified by simulation.The effects of polarization correlation and spatial correlation on the channel model are fully evaluated.The simulation results of the channel capacity of the proposed channel model in three typical environments are given.The new dual antenna diversity of high-altitude platform MIMO channel model proposed in this paper combines the advantages of deterministic model and statistical model,has the advantages of universality and parameter tunability,which can describe the high-altitude platform channel environment and the correlation of sub-channel accurately.Through the dual antenna diversity strategy,it can compensate for the severe shadowing problem in the low elevation area effectively,and effectively improves the reliability of the transmission link and improves the transmission data rate of the channel.