Key Technologies Research Of LEO Satellite Telemetry Link Channel Simulation

The low-orbit satellite communication makes up for the shortcomings of the terrestrial cellular system such as small capacity and poor flexibility,and meets the communication needs of global coverage with the characteristics of large-scale and highcapacity communication.Satellite channel simulation research is an important part in the development of LEO satellite communication system.In the existing satellite channel simulation research,most of them focus on the static simulation of satellites by ground stations,without considering the dynamic characteristics of mobile satellites,and ignoring the application scenarios of sea satellite observation stations,which are not suitable for the simulation of maritime telemetry links.For the application scenario of sea-surface satellite observatories to mobile satellites,the attitude analysis of sea-surface satellite observatories,the analysis of atmospheric satellite channel characteristics and the orbit calculation of mobile satellites are considered.Then a simulation scheme suitable for maritime satellite telemetry is proposed and tested.The main work is as follows:Firstly,the satellite orbit and atmospheric attenuation model are established,and the main parameters of satellite channel simulation are analyzed to provide reference for subsequent design.The functional requirements and performance indicators of the loworbit satellite channel simulation based on the sea surface satellite observation station are given,and the feasibility analysis is carried out from the perspectives of signal processing algorithm and route parameter calculation.Second,the overall scheme design of LEO satellite channel simulation is completed,and the functional requirements are divided from the perspective of combining software and hardware design methods.In the host computer,the orbit calculation of the mobile satellite,the calculation and transformation of the channel parameters,and the ship rocking model are completed.The effect of real-time channel parameters on the IF signal is realized in the IF signal processing unit,including the processing of large-scale delay,high-precision fractional delay,and Doppler frequency shift.A dynamic smoothing processing structure of integer delay and fractional delay is designed to simulate the signal changes of mobile satellites under dynamic conditions,which solves the sudden change of phase caused by the sudden loss of data caused by the update of configuration parameters.Third,the implementation and test verification of the intermediate frequency signal processing link was completed on the FPGA.The design is optimized for the balanced use of onboard resources on the FPGA implementation platform,and the resource consumption of the DSP48 E after the optimized implementation is reduced by 19%.The test results have reached the simulation indicators of the delay range of 5 s,the delay accuracy of 1 ns and the frequency offset range of 2 MHz,which verifies the feasibility of the design scheme.The low-orbit satellite channel simulation scheme designed in this paper provides a method for the design verification of the maritime telemetry link,and has reference significance for the FPGA design and engineering implementation of the low-orbit satellite channel dynamic simulation.