Research On Channel Estimation And Signal Detection Of Satellite OTFS Communication System

The 6th generation mobile communication system(6G)needs to meet higher performance targets than the 5G(5th generation)mobile communication system in application scenarios,transmission performance,and other aspects.To cope with high mobility scenarios such as satellites,unmanned aerial vehicles and high-speed trains,one of the challenges of 6G is to be able to meet the communication needs of scenarios with speeds up to 1000 km/h.Orthogonal time frequency space(OTFS)modulation multiplexes information symbols in delay-Doppler domain to transmission,which can achieve full diversity in time and frequency domain.Compared to orthogonal frequency division multiplexing(OFDM)technique,the OTFS modulation offers significant performance improvements in high-speed mobile scenarios.OTFS technology has higher spectral efficiency and lower Peak to Average Power Ratio(PAPR),which makes OTFS modulation more suitable for satellite-to-ground communication with high mobility than OFDM technology.However,the channel estimation and signal detection algorithm design for OTFS system is more challenging than OFDM system.Therefore,in this paper,we study the channel estimation and signal detection algorithms and improvement strategies for the satellite-to-ground OTFS communication system,and carry out in-depth simulation analysis and verification under typical scenarios,which is of guidance for the development of related technologies and system design.Firstly,this paper introduces the satellite-to-ground channel characteristics and the typical channel models.Then,we introduce the basic principle and implementation of the OTFS modulation.Then,we discuss the advantages and shortcomings of various channel estimation and signal detection schemes,and analyze the reasons why OTFS modulation is suitable for communication in satellite-to-ground high-speed mobile scenarios.Next,this paper investigates the channel estimation scheme for the OTFS system.The channel estimation problem can be transformed into a sparse signal recovery problem by exploiting the sparse characteristics of the delay-Doppler domain channel.A single measurement vector-based(SMV)channel estimation scheme is designed in this paper.On this basis,this paper proposes a multiple measurement vector-based(MMV)channel estimation scheme that can exploit the temporal correlation and the joint sparsity property of the channel,so that the accuracy of channel estimation can be improved.Besides,this paper simplifies the computational complexity of performing least squares(LS)channel estimation by taking advantage of the block circulant matrix with circulant blocks nature of the OTFS system pilot matrix.The simulation results show that the channel estimation schemes proposed in this paper have better performance and the lowcomplexity LS channel estimation scheme does not lead to loss of accuracy in channel estimation.Finally,this paper investigates the transmission performance of OTFS modulation applied in satellite-to-ground communication and the signal detection algorithm of the OTFS system.The minimum mean squared error with successive detection(MMSE-SD)algorithm based on successive interference cancellation is applied to the signal detection of the OTFS system to improve the performance,and a low-complexity successive interference cancellation based signal detection algorithm is given to address the high computational complexity of MMSE-SD.The simulation results show that improved signal detection algorithm proposed in this paper can achieve a trade-off between complexity and performance compared with the conventional signal detection algorithm,and the OTFS modulation is more suitable for satellite-to-ground communication with high mobility than the OFDM modulation.