A time-frequency modulation and demodulation method, system, device and medium for meteor trail communication

Abstract

A time-frequency modulation and demodulation method, system, device and medium for meteor trail communication. The method comprises: constructing a meteor trail communication system channel model, selecting a corresponding TFSK modulation mode according to the meteor trail communication system channel model, modulating a signal generated in the communication to obtain a meteor trail TFSK modulation signal, selecting a sub-channel corresponding to the meteor trail TFSK modulation signal for signal transmission, and receiving and demodulating the meteor trail TFSK modulation signal; the system, device and medium are used to implement a time-frequency modulation and demodulation method for meteor trail communication; the present invention has the advantages of good signal processing effect, improved communication effect, wide application range and high reliability.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a time-frequency modulation and demodulation method, system, equipment and medium for meteor trail communication. Background Art

[0002] Meteor Burst Communication (MBC) is a long-distance burst communication method that uses the ionized trails formed at high altitudes after meteoroids enter the upper atmosphere due to friction and combustion, and the forward scattering of VHEF radio waves. However, the natural phenomenon of meteors determines that this channel has its own particularity. First, the occurrence time of meteors in nature is unevenly distributed, the direction of the trails is random, and there are a huge number of small meteors that cannot be used. This makes it difficult to improve the utilization rate of meteors and the communication waiting time is long. Secondly, according to the difference in electron line density, meteor trails can be divided into two types: over-dense meteor trails and under-dense meteor trails. The trail lifetime varies from hundreds of milliseconds to several seconds. This meteor trail communication is also a burst communication; further, the meteor trail channel can be divided into multiple sub-channels such as sparse and underdense meteor trail channels, underdense multipath meteor trail channels, meteor cluster channels and sparse and overdense meteor trail channels. Each sub-channel has different channel fading characteristics and is accompanied by random scattering, which makes the communication transmission rate lower; existing meteor trail communication systems mostly use BPSK binary phase shift keying or QPSK orthogonal phase shift keying modulation technology, but since the available meteor trail channel is usually a multipath fading channel accompanied by noise and interference, and BPSK signals are easily affected by noise interference and multipath fading during transmission, affecting the communication effect.

[0003] The invention patent application with publication number CN113745852A discloses a communication method and conformal array antenna for a meteor trail communication system. The conformal array antenna is used to pre-process the received signal to obtain multiple groups of digital signals, and digital beamforming and demodulation are performed on the multiple groups of digital signals to obtain received signals. When the signal is transmitted, signal modulation and power division are performed to obtain multiple groups of digital signals. After digital beamforming is performed on the multiple groups of digital signals, the transmitted signal is pre-processed to obtain the transmitted signal corresponding to each patch array antenna, and the signal is transmitted through multiple patch array antennas of the conformal antenna array. However, since this method obtains signals through antennas, it is impossible to avoid the influence of multipath fading in meteor trail communication, which in turn affects the signal modulation effect, and it is impossible to modulate multiple meteor trail channels separately, so the scope of application is relatively small. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a time-frequency modulation and demodulation method, system, equipment and medium for meteor trail communication. By constructing multiple meteor trail sub-channels and synthesizing them according to statistical probability, a channel model of the meteor trail communication system is constructed, and the corresponding TFSK modulation mode is selected for modulation according to the signal generated in the communication, and the TFSK modulated signal is then transmitted to the receiving end through different methods for demodulation. It has the advantages of good signal processing effect, improved communication effect, wide application range and high reliability.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A time-frequency modulation and demodulation method for meteor trail communication comprises the following steps:

[0007] Step 1: Construct a meteor trail communication system channel model, specifically:

[0008] In combination with the attenuation characteristics of natural meteors, subchannels are constructed according to set parameters, including different meteor trail electron line densities, the presence of multipath effects, and the number of meteors. The subchannels include sparse and underdense meteor trail subchannels, underdense meteor trail multipath subchannels, underdense meteor cluster subchannels, meteor shower subchannels, sparse and overdense meteor trail subchannels without Rayleigh fading, and sparse and overdense meteor trail subchannels with Rayleigh fading. The above subchannels are then synthesized according to the statistical probability of subchannel occurrence to construct a meteor trail communication system channel model.

[0009] Step 2: Select a corresponding TFSK modulation mode according to the meteor trail communication system channel model constructed in step 1, and modulate the signal generated in the communication to obtain a meteor trail TFSK modulated signal;

[0010] Step 3: From the meteor trail communication system channel model constructed in step 1, select the sub-channel corresponding to the meteor trail TFSK modulated signal obtained in step 2 for signal transmission, and receive and demodulate the meteor trail TFSK modulated signal.

[0011] The step 1 of constructing a meteor trail communication system channel model specifically includes the following steps:

[0012] Step 1.1, construct a sparse and under-dense meteor trail sub-channel. Specifically, there is only one available under-dense meteor trail in a communication. That is, before the trail fades to the point where communication cannot be maintained, no other available meteor trail appears. The communication system needs to wait until the next available meteor trail appears and communication is resumed. The received signal power of the sparse and under-dense meteor channel is Attenuation factor τ and initial received signal power P R(0) are shown in formulas (1), (2) and (3) respectively:

[0013]

[0014]

[0015]

[0016] Among them, P T Indicates the power of the transmitted signal, G T Indicates the transmit antenna gain, G R represents the receiving antenna gain, λ represents the wavelength, and t represents the time;

[0017] Step 1.2: Construct the under-dense meteor trail multipath subchannel, specifically: according to the received signal power P of the sparse under-dense meteor trail subchannel in step 1.1 R (t) S_U , adjust the delay size Δt of each multipath i and attenuation coefficient a i , under the control of multipath delay and attenuation coefficient, the received signal power P of the under-dense sub-channel containing multipath phenomenon is generated R (t) M , as shown in formula (4):

[0018]

[0019] Where N1 represents the number of simulated multipaths, satisfying 1≤i≤N1;

[0020] Step 1.3: Construct an under-dense meteor cluster-like sub-channel, where the received signal power P of the under-dense meteor cluster-like sub-channel is R (t) G As shown in formula (5):

[0021]

[0022] Among them, N2 represents the number of meteors, Δτ i represents the delay of each path;

[0023] Step 1.4: Construct a meteor shower sub-channel, the received signal power P of the meteor shower sub-channel R (t) Sh As shown in formula (6):

[0024]

[0025] Among them, N3 represents the number of meteors, and N3 is much larger than the value of N2 in formula (5);

[0026] Step 1.5: Construct the sparse and dense meteor trail subchannel without Rayleigh fading. The received signal power P of the sparse and dense meteor trail subchannel without Rayleigh fading is R (t) S_O And the initial power P of the received signal R (0) S_O As shown in formula (7) and formula (8):

[0027]

[0028]

[0029] Step 1.6: Construct a sparse and dense meteor trail subchannel with Rayleigh fading. Generate a random signal M(t) that obeys the Rayleigh fading distribution to calculate the received signal power P of the sparse and dense meteor trail subchannel without Rayleigh fading in step 1.5. R (t) S_O Adjust the received signal power P of the sparse and dense meteor trail subchannel containing Rayleigh fading to obtain R (t) R_O , as shown in formula (9):

[0030]

[0031] Step 1.7: synthesize the sub-channels constructed in steps 1.1 to 1.6 to form a meteor trail communication system channel model.

[0032] In step 2, the corresponding TFSK modulation mode is selected according to the meteor trail communication system channel model constructed in step 1, and the signal generated in the communication is modulated, specifically:

[0033] Step 2.1, setting parameters for the meteor trail TFSK signal, specifically: according to the requirements of meteor trail communication, setting the bandwidth of the meteor trail TFSK signal to between 30 and 50 MHz, and setting the bit rate of the meteor trail TFSK signal to between 64 and 256 kbps;

[0034] Step 2.2: Take K bit symbols b = {b1, ..., b K}, mapped to a sending symbol S i , 1≤i≤2 K , the symbol length T symbol Divided into N time slots, each time slot length is T slot To achieve time domain diversity, suppose there are M orthogonal carrier frequencies in the meteor trail TFSK system, and the frequency set is F = {f1, ...f M}, in each time slot T slot Within, different frequencies satisfy formula (10):

[0035]

[0036] Step 2.3: According to the characteristics of the meteor trail TFSK signal, select the corresponding sub-channel from the meteor trail communication system channel model established in step 1. The transmitting end modulates the meteor trail TFSK signal with the code element in the manner of step 2.2 and adds white noise, and sends it to the signal receiving module.

[0037] In step 3, the meteor trail TFSK modulated signal is received and demodulated, specifically:

[0038] After modulating the meteor trail TFSK signal and adding white noise in step 2, the modulated meteor trail TFSK signal r(t) is obtained through the receiving end and demodulated by the TFSK receiver. Specifically, the modulated meteor trail TFSK signal r(t) is first converted from serial to parallel to separate the waveforms in different time slots. Then, multi-carrier non-coherent reception is performed on the waveforms in each time slot respectively. The received results are then transmitted to the corresponding combiner for comparison and judgment, and finally the demodulation result is obtained.

[0039] A time-frequency modulation and demodulation system for meteor trail communication, comprising:

[0040] A signal generation module is used to generate a meteor trail TFSK signal and send it to the meteor trail communication system channel model constructed in step 1;

[0041] A signal modulation module is used to select a corresponding TFSK modulation mode based on the meteor trail communication system channel model constructed in step 1 to modulate the signal generated in the communication, obtain a meteor trail TFSK modulated signal, and send it to the signal receiving module;

[0042] A signal receiving module is used to receive the meteor trail TFSK modulated signal sent by the signal modulation module;

[0043] The signal demodulation module is used to demodulate the meteor trail TFSK modulated signal received by the signal receiving module.

[0044] A time-frequency modulation and demodulation device for meteor trail communication, comprising:

[0045] memory for storing computer programs;

[0046] A processor is used to implement the time-frequency modulation and demodulation method for meteor trail communication when executing the computer program.

[0047] A computer-readable medium stores a computer program, and when the computer program is executed by a processor, it can implement the time-frequency modulation and demodulation method of meteor trail communication.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. The present invention constructs a channel model of the meteor trail communication system by constructing multiple meteor trail sub-channels and synthesizing them according to statistical probability. It also selects the corresponding TFSK modulation mode for modulation according to the signal generated in the communication, and then transmits the TFSK modulated signal to the receiving end through different channels for demodulation, which has the advantage of good signal processing effect.

[0050] 2. The present invention analyzes the channel characteristics unique to meteor trail communication in step 2 and utilizes the good channel anti-fading capability of the TFSK signal to avoid noise interference in communication and the influence of multipath fading of natural meteor trails, thereby improving the communication effect of the method of the present invention.

[0051] 3. By selecting the corresponding TFSK modulation mode through the meteor trail sub-channel in the meteor trail communication system channel model constructed in step 1, it is applicable to various types of signals appearing in communication. Therefore, the present invention has the advantage of a wide range of applications.

[0052] 4. The meteor trail channel modeling parameters constructed by the present invention are flexible and adjustable, and the TFSK modulation modes are diverse. It can simulate the physical characteristics of the actual meteor channel with high precision, and specifically test the performance of different modulation modes, making it closer to the actual situation. Therefore, the present invention has the advantage of high reliability of the communication solution.

[0053] In summary, the present invention constructs a channel model of the meteor trail communication system by constructing multiple meteor trail sub-channels and synthesizing them according to statistical probability, and selects the corresponding TFSK modulation mode for modulation according to the signal generated in the communication, and then transmits the TFSK modulated signal to the receiving end through different transmissions for demodulation. It has the advantages of good signal processing effect, improved communication effect, wide application range and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Flow chart of the method of the present invention.

[0055] Figure 2 The figure is a schematic diagram of the process of constructing a channel model of a meteor trail communication system in an embodiment of the present invention.

[0056] Figure 3 This is a time-frequency diagram of the symbol mapping of the 00 bit group of the quaternary four-time four-frequency system in an embodiment of the present invention.

[0057] Figure 4 This is a block diagram of time slot non-coherent reception based on a quaternary four-time four-frequency system in an embodiment of the present invention.

[0058] Figure 5 1 is a comparison chart of the bit error rates of TFSK and BPSK under the less dense multi-path residual sub-channel in an embodiment of the present invention.

[0059] Figure 6 1 is a comparison chart of TFSK bit error rates under different meteor trail sub-channels in an embodiment of the present invention. DETAILED DESCRIPTION

[0060] The present invention will be described in detail below with reference to the accompanying drawings.

[0061] refer to Figure 1 The present invention provides an embodiment of a time-frequency modulation and demodulation method for meteor trail communication, comprising the following steps:

[0062] Step 1: Construct a meteor trail communication system channel model, specifically:

[0063] The propagation mechanism of meteor trail radio waves is analyzed, and the propagation mechanism of under-dense and over-dense meteor trail radio waves in the mathematical model of meteor trail channels is studied, as well as the statistical characteristics of natural meteor types in nature. Figure 2 , adopting a design method combining partial implementation with overall synthesis, combining the attenuation characteristics of natural meteors, and constructing subchannels according to set parameters, the parameters including the following three items: different meteor trail electron line densities, the presence of multipath effects, and the number of meteors; the subchannels include the following six types: sparse and underdense meteor trail subchannels, underdense meteor trail multipath subchannels, underdense meteor cluster subchannels, meteor shower subchannels, sparse and overdense meteor trail subchannels without Rayleigh fading, and sparse and overdense meteor trail subchannels with Rayleigh fading; the above six subchannels are then synthesized according to the statistical probability of subchannel occurrence to construct a meteor trail communication system channel model;

[0064] Step 2: Select a corresponding TFSK modulation mode according to the meteor trail communication system channel model constructed in step 1, and modulate the signal generated in the communication to obtain a meteor trail TFSK modulated signal;

[0065] Step 3: From the meteor trail communication system channel model constructed in step 1, select the sub-channel corresponding to the meteor trail TFSK modulated signal obtained in step 2 for signal transmission, and receive and demodulate the meteor trail TFSK modulated signal; by constructing multiple meteor trail sub-channels and synthesizing them according to statistical probability to construct the meteor trail communication system channel model, and select the corresponding TFSK modulation mode for modulation according to the signal generated in the communication, and then transmit the TFSK modulated signal to the receiving end through different methods for demodulation, which has the advantage of good signal processing effect.

[0066] The step 1 of constructing a meteor trail communication system channel model specifically includes the following steps:

[0067] Step 1.1: Construct a sparse and under-dense meteor trail sub-channel. Specifically, if only one available under-dense meteor trail appears in one communication, that is, before the trail fades to the point where communication cannot be maintained, no other available meteor trail appears. The communication system needs to wait until the next available meteor trail appears before communication is resumed. The received signal power P of the sparse and under-dense meteor channel is R (t) SU , attenuation factor τ and initial received signal power P R (0) are shown in formulas (1), (2) and (3) respectively:

[0068]

[0069]

[0070]

[0071] Among them, P T Indicates the power of the transmitted signal, G T Indicates the transmit antenna gain, G R represents the receiving antenna gain, λ represents the wavelength, and t represents the time;

[0072] Step 1.2: Construct the under-dense meteor trail multipath subchannel, specifically: according to the received signal power P of the sparse under-dense meteor trail subchannel in step 1.1 R (t) S_U , adjust the delay size Δt of each multipath i and attenuation coefficient a i , under the control of multipath delay and attenuation coefficient, the received signal power P of the under-dense sub-channel containing multipath phenomenon is generated R (t) M , as shown in formula (4):

[0073]

[0074] Where N1 represents the number of simulated multipaths, satisfying 1≤i≤N1;

[0075] Step 1.3: Construct an under-dense meteor cluster-like sub-channel, where the received signal power P of the under-dense meteor cluster-like sub-channel is R (t) G As shown in formula (5):

[0076]

[0077] Among them, N2 represents the number of meteors, Δτ i represents the delay of each path;

[0078] Step 1.4: Construct a meteor shower sub-channel, the received signal power P of the meteor shower sub-channel R (t) Sh As shown in formula (6):

[0079]

[0080] Among them, N3 represents the number of meteors, and N3 is much larger than the value of N2 in formula (5);

[0081] Step 1.5: Construct the sparse and dense meteor trail subchannel without Rayleigh fading. The received signal power P of the sparse and dense meteor trail subchannel without Rayleigh fading is R (t) S_O And the initial power P of the received signal R (0) S_O As shown in formula (7) and formula (8):

[0082]

[0083]

[0084] Step 1.6: Construct a sparse and dense meteor trail subchannel with Rayleigh fading. Generate a random signal M(t) that obeys the Rayleigh fading distribution to calculate the received signal power P of the sparse and dense meteor trail subchannel without Rayleigh fading in step 1.5. R (t) S_O Adjust the received signal power P of the sparse and dense meteor trail subchannel containing Rayleigh fading to obtain R (t) R_O , as shown in formula (9):

[0085]

[0086] Step 1.7: The sub-channels constructed in steps 1.1 to 1.6 are synthesized into a meteor trail communication system channel model. By constructing the meteor trail communication system channel model, different types of meteor trail TFSK signals are combined for modulation and demodulation, which has the advantage of good signal processing effect.

[0087] In step 2, the corresponding TFSK modulation mode is selected according to the meteor trail communication system channel model constructed in step 1, and the signal generated in the communication is modulated, specifically:

[0088] Step 2.1, setting parameters for the meteor trail TFSK signal, specifically: according to the requirements of meteor trail communication, setting the bandwidth of the meteor trail TFSK signal to between 30 and 50 MHz, and setting the bit rate of the meteor trail TFSK signal to between 64 and 256 kbps;

[0089] Step 2.2: Take K bit symbols b = {b1, ..., b K}, mapped to a sending symbol S i , 1≤i≤2 K , the symbol length T symbol Divided into N time slots, each time slot length is T slot To achieve time domain diversity, suppose there are M orthogonal carrier frequencies in the meteor trail TFSK system, and the frequency set is F = {f1, ...f M}, in each time slot T slot Within, different frequencies satisfy formula (10):

[0090]

[0091] Step 2.3: According to the characteristics of the meteor trail TFSK signal, select the corresponding sub-channel from the meteor trail communication system channel model established in step 1, modulate the meteor trail TFSK signal with the code element in the manner of step 2.2 through the transmitter, add white noise, and send it to the signal receiving module; Due to the different parameters K, N, M, TFSK modulation has many signal modes, namely 2 KThe commonly used modes are two-time two-tone, four-time two-tone, four-time four-tone, three-time nine-tone, etc. Different signal modes can be selected for different types of meteor trail sub-channels. For example, in sparse and overdense meteor trail channels without Rayleigh fading with a long channel duration and stable attenuation process, an octal four-time four-tone signal mode is used to obtain a higher transmission rate and spectrum utilization; for sparse and underdense meteor trail channels with rapid attenuation and short channel duration, a quaternary four-time four-tone signal mode can be used; the longer the channel duration and the more stable the channel attenuation, the higher the transmission rate and the greater the spectrum utilization is selected to pursue an increase in the transmission rate; conversely, the shorter the channel duration and the more irregular the channel attenuation, the lower the transmission rate and the lower the spectrum utilization is selected to pursue communication stability.

[0092] In step 3, the meteor trail TFSK modulated signal in step 2 is received and demodulated, specifically:

[0093] After the meteor trail TFSK signal is modulated and white noise is added in step 2, the modulated meteor trail TFSK signal r(t) is obtained through the receiving end and demodulated by the TFSK receiver. Specifically, the modulated meteor trail TFSK signal r(t) is first converted from serial to parallel to separate the waveforms in different time slots. Then, the waveforms in each time slot are received by multi-carrier incoherent reception. The received results are then transmitted to the corresponding combiner for comparison and judgment, and finally the demodulation result is obtained, such as Figure 4 , which is a block diagram of time slot-based non-coherent reception taking a quaternary four-time four-frequency system as an example in an embodiment of the present invention.

[0094] A time-frequency modulation and demodulation system for meteor trail communication, comprising:

[0095] A signal generation module is used to generate a meteor trail TFSK signal and send it to the meteor trail communication system channel model constructed in step 1;

[0096] A signal modulation module is used to select a corresponding TFSK modulation mode based on the meteor trail communication system channel model constructed in step 1 to modulate the signal generated in the communication, obtain a meteor trail TFSK modulated signal, and send it to the signal receiving module;

[0097] A signal receiving module is used to receive the meteor trail TFSK modulated signal sent by the signal modulation module;

[0098] The signal demodulation module is used to demodulate the meteor trail TFSK modulated signal received by the signal receiving module.

[0099] A time-frequency modulation and demodulation device for meteor trail communication, comprising:

[0100] memory for storing computer programs;

[0101] A processor is used to implement the time-frequency modulation and demodulation method for meteor trail communication when executing the computer program.

[0102] A computer-readable medium stores a computer program, and when the computer program is executed by a processor, it can implement the time-frequency modulation and demodulation method of meteor trail communication.

[0103] refer to Figure 3 , Figure 3 This is a time-frequency diagram of the symbol mapping of the 00 bit group of the quaternary four-time four-frequency system in an embodiment of the present invention. Taking the quaternary four-time four-frequency TFSK modulation as an example, this TFSK modulation signal mode has complete orthogonality. The quaternary four-time four-frequency TFSK modulation symbol combination is shown in Table 1:

[0104]

[0105] Table 1

[0106] refer to Figure 3 , a transmission symbol S1 is mapped by the bit combination 00, the time length of the time slot allocator is adjusted to 0.5T, and the switch matrix is ​​changed within the time of 2T to transmit the cosine signal with frequencies of f1 to f4 in sequence, and the carrier frequency f is set. c =40MHz, the frequency interval is 0.2MHz, so: f1=39.6MHz, f2=39.8MHz, f3=40.2MHz, f4=40.4MHz; by evenly dividing each bit combination into four time slots, different frequencies are used to transmit signals in these four time slots, and finally a meteor trail TFSK signal is obtained. The code element is modulated by the above TFSK to generate a TFSK signal, which is transmitted to the signal receiving module through the established different types of meteor trail channel models.

[0107] The effect of the present invention can be further illustrated by simulation:

[0108] Set the simulation conditions, use quaternary four-time four-frequency TFSK signal modulation, set the bit rate to 100kbps, and the carrier frequencies are: f1 = 39.6MHz, f2 = 39.8MHz, f3 = 40.2MHz, f4 = 40.4MHz.

[0109] refer to Figure 5In an embodiment of the present invention, simulation is performed to compare the bit error rates of TFSK signals and BPSK signals in an underdense multipath residual channel. It can be seen from the figure that the bit error rate of TFSK signal is lower than that of BPSK signal, and the performance is better; it is proved that compared with BPSK modulation, the meteor trail time-frequency modulation and demodulation method proposed in the present invention can effectively overcome the multipath interference problem existing in the residual channel in a short time.

[0110] refer to Figure 6 , Figure 6 A comparison diagram of TFSK bit error rates under different meteor trail subchannels in an embodiment of the present invention is shown. Four meteor trail subchannels are selected: sparse and underdense subchannels, underdense multipath subchannels, underdense meteor cluster subchannels, and sparse overdense subchannels without Rayleigh fading. TFSK signals are transmitted through the above subchannels. The figure shows how the bit error rate at the receiver output changes with the signal-to-noise ratio. It can be found from the figure that the meteor trail time-frequency modulation and demodulation method proposed in the present invention can effectively communicate in sparse and underdense subchannels, underdense multipath subchannels, and sparse overdense subchannels without Rayleigh fading; for strongly random subchannels such as meteor cluster channels, it also has a good signal modulation effect, which meets the communication needs under normal circumstances.

Claims

1. A time-frequency modulation and demodulation method for meteor trail communication, characterized in that: The following steps are involved: Step 1: Construct a meteor trail communication system channel model, specifically: In combination with the attenuation characteristics of natural meteors, subchannels are constructed according to set parameters, including different meteor trail electron line densities, the presence of multipath effects, and the number of meteors. The subchannels include sparse and underdense meteor trail subchannels, underdense meteor trail multipath subchannels, underdense meteor cluster subchannels, meteor shower subchannels, sparse and overdense meteor trail subchannels without Rayleigh fading, and sparse and overdense meteor trail subchannels with Rayleigh fading. The above subchannels are then synthesized according to the statistical probability of subchannel occurrence to construct a meteor trail communication system channel model. The step 1 of constructing a meteor trail communication system channel model specifically includes the following steps: Step 1.1, construct a sparse and under-dense meteor trail sub-channel. Specifically, there is only one available under-dense meteor trail in a communication. That is, before the trail fades to the point where communication cannot be maintained, no other available meteor trail appears. The communication system needs to wait until the next available meteor trail appears and communication is resumed. The received signal power of the sparse and under-dense meteor channel is Attenuation factor τ and initial received signal power P R (0) are shown in formulas (1), (2) and (3) respectively: Among them, P T Indicates the power of the transmitted signal, G T Indicates the transmit antenna gain, G R represents the receiving antenna gain, λ represents the wavelength, and t represents the time; Step 1.2: Construct the under-dense meteor trail multipath subchannel, specifically: according to the received signal power P of the sparse under-dense meteor trail subchannel in step 1.1 R (t) S_U , adjust the delay size Δt of each multipath i and attenuation coefficient a i , under the control of multipath delay and attenuation coefficient, the received signal power P of the under-dense sub-channel containing multipath phenomenon is generated R (t) M , as shown in formula (4): Where N1 represents the number of simulated multipaths, satisfying 1≤i≤N1; Step 1.3: Construct an under-dense meteor cluster-like sub-channel, where the received signal power P of the under-dense meteor cluster-like sub-channel is R (t) G As shown in formula (5): Among them, N2 represents the number of meteors, Δτ i represents the delay of each path; Step 1.4: Construct a meteor shower sub-channel, the received signal power P of the meteor shower sub-channel R (t) Sh As shown in formula (6): Among them, N3 represents the number of meteors, and N3 is much larger than the value of N2 in formula (5); Step 1.5: Construct the sparse and dense meteor trail subchannel without Rayleigh fading. The received signal power P of the sparse and dense meteor trail subchannel without Rayleigh fading is R (t) S_O And the initial power P of the received signal R (0) S_O As shown in formula (7) and formula (8): Step 1.6: Construct a sparse and dense meteor trail subchannel with Rayleigh fading. Generate a random signal M(t) that obeys the Rayleigh fading distribution to calculate the received signal power P of the sparse and dense meteor trail subchannel without Rayleigh fading in step 1.

5. R (t) S_O Adjust the received signal power P of the sparse and dense meteor trail subchannel containing Rayleigh fading to obtain R (t) R_O , as shown in formula (9): P R (t) R_O =P R (t) S_O ·M(t) (9) Step 1.7: synthesize the sub-channels constructed in steps 1.1 to 1.6 to form a meteor trail communication system channel model; Step 2: Select a corresponding TFSK modulation mode according to the meteor trail communication system channel model constructed in step 1, and modulate the signal generated in the communication to obtain a meteor trail TFSK modulated signal; In step 2, the corresponding TFSK modulation mode is selected according to the meteor trail communication system channel model constructed in step 1, and the signal generated in the communication is modulated, specifically: Step 2.1, setting parameters for the meteor trail TFSK signal, specifically: according to the requirements of meteor trail communication, setting the bandwidth of the meteor trail TFSK signal to between 30 and 50 MHz, and setting the bit rate of the meteor trail TFSK signal to between 64 and 256 kbps; Step 2.2: Take K bit symbols b = {b1, ..., b K }, mapped to a sending symbol S i , 1≤i≤2 K , the symbol length T synbol Divided into N time slots, each time slot length is T slot To achieve time domain diversity, suppose there are M orthogonal carrier frequencies in the meteor trail TFSK system, and the frequency set is F = {f1, ...f M }, in each time slot T slot Within, different frequencies satisfy formula (10): Step 2.3: Based on the characteristics of the meteor trail TFSK signal, select the corresponding subchannel from the meteor trail communication system channel model established in step 1. The transmitting end modulates the meteor trail TFSK signal with the code element according to the method of step 2.2 and adds white noise, and then sends it to the signal receiving module; Step 3: From the meteor trail communication system channel model constructed in step 1, select a subchannel corresponding to the meteor trail TFSK modulated signal obtained in step 2 for signal transmission, and receive and demodulate the meteor trail TFSK modulated signal; In step 3, the meteor trail TFSK modulated signal is received and demodulated, specifically: After modulating the meteor trail TFSK signal and adding white noise in step 2, the modulated meteor trail TFSK signal r(t) is obtained through the receiving end and demodulated by the TFSK receiver. Specifically, the modulated meteor trail TFSK signal r(t) is first converted from serial to parallel to separate the waveforms in different time slots. Then, multi-carrier non-coherent reception is performed on the waveforms in each time slot respectively. The received results are then transmitted to the corresponding combiner for comparison and judgment, and finally the demodulation result is obtained.

2. A time-frequency modulation and demodulation system for meteor trail communication based on the method of claim 1, characterized in that: include: A signal generation module is used to generate a meteor trail TFSK signal and send it to the meteor trail communication system channel model constructed in step 1; A signal modulation module is used to select a corresponding TFSK modulation mode based on the meteor trail communication system channel model constructed in step 1 to modulate the signal generated in the communication, obtain a meteor trail TFSK modulated signal, and send it to the signal receiving module; A signal receiving module is used to receive the meteor trail TFSK modulated signal sent by the signal modulation module; The signal demodulation module is used to demodulate the meteor trail TFSK modulated signal received by the signal receiving module.

3. A time-frequency modulation and demodulation device for meteor trail communication, characterized in that: include: memory for storing computer programs; A processor is configured to implement the time-frequency modulation and demodulation method for meteor trail communication according to claim 1 when executing the computer program.

4. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, it can implement the time-frequency modulation and demodulation method for meteor trail communication described in claim 1.

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