Research On Modeling And Communication Simulation Of Relay Communication Channel In Mars Entering Segment

When the fire detection vehicle enters the Martian atmosphere at hypersonic speed,the communication channel environment is complicated.The plasma sheath formed around it will cause a large attenuation of electromagnetic wave signals and even interrupt communication.The Martian dust storm seriously affects the transmission of radio wave signals.In addition,due to the fact that most of the world’s fire detection missions use directto-ground communication during the entry phase,the information transmission rate is low,and the aircraft cannot guarantee efficient and reliable communication during the entire entry,descent,and landing process(EDL segment),resulting in the detector’s failure to follow A safe landing or even a failed landing is expected.In this thesis,based on the complicated channel environment in the atmospheric entry section of Mars exploration,a relay dual-polarization MIMO communication scheme for the Mars entry section is proposed,and the mapping relationship between the Mars rover’s different polarization angles and channel capacity in the EDL section is studied;The segment-relay dual-polarization MIMO communication system evaluates the performance of communication schemes under different modulation and coding methods.The main innovations and work of this paper are as follows:1.Analyzed the detection data of the atmospheric entry section of the current Mars exploration missions in various countries,and analyzed the attenuation of the Martian atmosphere,ionosphere,clouds and Martian dust on the transmission of electric wave signals under different electromagnetic wave bands;the reconstruction data of the entry section of the Mars Pathfinder is used as For example,establish the electron density distribution model of the plasma sheath on the surface of the Mars probe,focusing on the attenuation and phase shift of the time-varying plasma sheath in the EDL section to electromagnetic waves in different communication frequency bands,and the signal interruption time after the Mars probe enters the Martian atmosphere to evaluate;2.For the relay communication scenario between the Mars rover and the orbiter,a dualpolarization MIMO channel model for the Mars entry segment relay was established,and the influence of the Mars entry segment channel environment on the signal power and channel correlation was studied.The simulation of dual-polarization MIMO communication technology is realized,and the mapping relationship between the incident angle of the different polarized waves and the channel capacity of the Mars rover in the entry section of the atmosphere is established.The simulation results show that the relay dual-polarization MIMO communication technology proposed in this article can significantly increase the channel capacity compared with the previous SISO communication in the Mars entry segment;3.Established a dual-polarization MIMO communication system for the Mars entry segment relay,compared the bit error rate of the dual-polarization MIMO communication scheme and SISO communication at a typical entry height,evaluated the carrier communication performance of different frequency bands,and was the best entry segment The selection of the communication frequency band provides a theoretical basis,focusing on the evaluation of the bit error rate under different modulation methods and different encoding methods.The simulation results show that at the flight altitude where the electron density of the plasma sheath in the EDL section is higher,when the carrier frequency is in the Ka band,the MFSK signal with high modulation order is about 4 d B higher than the BPSK signal,and the LDPC code is compared with RS+ Convolutional concatenated codes have a 3 d B increase in coding gain.The dual-polarization MIMO communication scheme proposed in this thesis for the Mars entry segment can effectively increase the channel capacity,improve the communication quality of the EDL segment,and can significantly reduce the short-term communication "black barrier" time of the Mars entry segment,which can provide the communication link capacity for the Mars entry segment The optimization and design of communication system provide reference.