Low earth orbit satellite communication ranging integrated signal generation and analysis method

Abstract

The invention belongs to the related technical field of satellite communication ranging, and particularly relates to a low-orbit satellite communication ranging integrated signal generation and analysis method, which comprises the following steps of: generating a pilot signal according to an ideal self-correlation sequence, and mapping the pilot signal and a modulated constellation symbol to an OFDM (Orthogonal Frequency Division Multiplexing) resource unit; generating a transmitting signal, performing Doppler frequency shift pre-compensation on the receiving signal at a receiving end, sampling to obtain a discrete signal, and generating a local sampling sequence; and respectively carrying out self-correlation operation on the received discrete signal and the local sequence in the time domain and the frequency domain to estimate time delay so as to obtain a corresponding transmission distance. According to the method, an optimization function of system communication and ranging performance can be further established, a communication error rate and a ranging error are minimized based on a genetic algorithm, and an autocorrelation sequence and a pilot frequency distribution matrix are obtained. By using the method provided by the invention, the system can realize the distance measurement function while reliable communication is realized, and the communication performance and the distance measurement performance can be balanced.

Description

Technical Field

[0001] The present invention belongs to the technical field related to satellite communication ranging, and more specifically, relates to a low-orbit satellite communication ranging integrated signal generation and analysis method. Background Art

[0002] With the unprecedented development of the Internet of Things and emerging network services, the growth of the number of devices and the scale of data, relying solely on ground communication networks can no longer meet the needs of the Internet of Everything. Satellites, especially low-orbit satellites, have become the key to overcoming geographical and climatic limitations and expanding global network coverage. With its wide coverage, low latency, and large capacity, the low-orbit satellite network has become an important extension, supplement, and backup of the ground backbone network, providing stable and efficient support for global seamless coverage, and playing a unique role in various fields such as economy and national defense.

[0003] The existing communication and navigation satellite systems have different requirements in terms of signal transmission and signal detection, so they have been developing independently and using different modulation methods and receiving algorithms. The two occupy different frequency bands and bandwidths, resulting in low efficiency in the utilization of resources such as frequency and orbit. However, both are based on electromagnetic wave propagation, and their respective systems include modules such as signal generation, digital-to-analog conversion, power amplification, and digital signal processing. Therefore, the fusion of communication and navigation has unique advantages. The communication and navigation fusion system has advantages that a single system does not have and provides additional gains for the performance of the integrated system. Its integrated implementation can improve spectrum utilization and reduce system duplication, which has significant social significance and economic value.

[0004] In order to achieve high-speed transmission and high-precision ranging and positioning under limited bandwidth, the waveform design of the integrated communication and navigation system plays a vital role. However, there are significant differences in the signal systems of communication signals and navigation signals. Communication signals are usually discontinuous digital signals that propagate in both directions, while navigation signals are usually broadband continuous broadcast signals. The combination of the two must consider the compatibility between the signals, as well as indicators such as peak-to-average power ratio, bit error rate and ranging accuracy.

[0005] The existing low-orbit satellite communication constellation block pilot signal is superimposed on the communication signal in a block form, occupying part of the subcarriers of the OFDM signal for transmission, thereby ensuring the continuity of the ranging pilot signal in the time and frequency domain. Autocorrelation estimation is performed in the time domain to obtain the corresponding distance value, determine the ranging accuracy and communication resource utilization. However, there are only three ways to superimpose the block pilot signal on the communication signal, which lacks flexible configuration and cannot be adjusted according to demand; it is difficult to accurately estimate the delay and thus accurately estimate the distance by performing autocorrelation calculations only in the time domain; the ranging accuracy and communication performance of the system are mutually exclusive, and the performance of the two cannot be adjusted according to external needs to maximize performance. Summary of the invention

[0006] In view of the above defects or improvement needs of the prior art, the present invention provides a low-orbit satellite communication and ranging integrated signal generation and analysis method, the purpose of which is to improve the accuracy of signal transmission delay estimation, thereby solving the technical problem of low ranging accuracy in ranging communication integration.

[0007] To achieve the above object, according to one aspect of the present invention, a method for generating a low-orbit satellite communication and ranging integrated transmission signal is provided, comprising:

[0008] Generate a pilot signal according to a preset ideal autocorrelation sequence, map the pilot signal and the constellation symbol to an OFDM resource unit according to a preset distribution method, and obtain an OFDM signal; perform OFDM modulation on the OFDM signal to generate a transmission signal;

[0009] Wherein, if there is a communication task, the constellation symbol is obtained by modulating the data to be transmitted;

[0010] The transmitting signal is used for receiving at the receiving end to obtain a receiving signal, and the receiving signal is pre-compensated for Doppler frequency shift and sampled to obtain a discrete signal y k ; by y k Parse the data to be transmitted and k With the known pilot signal sampling sequence s k Perform autocorrelation calculation in the time domain to obtain the integer delay τ in the total signal transmission delay 1 ; The sampling sequence s k Shift p to get right and k Perform fast Fourier transform to obtain frequency domain data S and Y respectively; calculate the autocorrelation W of Z at the qth subcarrier and the q+Qth subcarrier to obtain the fractional delay τ in the total signal transmission delay 2 , where Z is the autocorrelation equation of S and Y in the frequency domain; the integer delay τ 1 and fractional delay τ 2 The total signal transmission delay τ is added together, and combined with the speed of light, the estimated distance between the satellite and the ground is obtained.

[0011] Furthermore, the ideal autocorrelation sequence is a ZC sequence.

[0012] Furthermore, the ideal autocorrelation sequence and the distribution mode are optimized based on a genetic algorithm with optimal communication and ranging performance.

[0013] According to another aspect of the present invention, a low-orbit satellite communication and ranging integrated transmission device is provided, comprising: a processor, a memory storing instructions executable by the processor, and a data transceiver for data sending and / or receiving; wherein, when the instructions are executed by the processor, the low-orbit satellite communication and ranging integrated transmission signal generation method as described above is executed.

[0014] According to another aspect of the present invention, a method for analyzing received signals of low-orbit satellite communication and ranging integration is provided, comprising:

[0015] The Doppler frequency shift pre-compensation of the received signal from the transmitter is performed and the discrete signal y is obtained by sampling. k ; by y k Parse the data to be transmitted and k With the known pilot signal sampling sequence s k Perform autocorrelation calculation in the time domain to obtain the integer delay τ in the total signal transmission delay 1 ; The sampling sequence s k Shift p to get right and k Perform fast Fourier transform to obtain frequency domain data S and Y respectively; calculate the autocorrelation W of Z at the qth subcarrier and the q+Qth subcarrier to obtain the fractional delay τ in the total signal transmission delay 2 , where Z is the autocorrelation equation of S and Y in the frequency domain; the integer delay τ 1 and fractional delay τ 2 The total signal transmission delay τ is added together, and combined with the speed of light, the estimated distance between the satellite and the ground is obtained;

[0016] Among them, the received signal comes from the transmit signal generated and transmitted by the transmitting end, and the transmit signal is generated in the following manner: a pilot signal is generated according to a preset ideal autocorrelation sequence, and the pilot signal and the constellation symbol are mapped to the OFDM resource unit according to a preset distribution method to obtain an OFDM signal; and the OFDM signal is OFDM modulated to generate a transmit signal.

[0017] Furthermore, the ideal autocorrelation sequence is a ZC sequence.

[0018] Furthermore, the ideal autocorrelation sequence and the distribution mode are optimized based on a genetic algorithm with optimal communication and ranging performance.

[0019] According to another aspect of the present invention, a low-orbit satellite communication and ranging integrated receiving device is provided, comprising: a processor, a memory storing instructions executable by the processor, and a data transceiver for data sending and / or receiving; wherein, when the instructions are executed by the processor, the low-orbit satellite communication and ranging integrated receiving signal analysis method as described above is executed.

[0020] According to another aspect of the present invention, a low-orbit satellite communication and ranging integrated system is provided, comprising the low-orbit satellite communication and ranging integrated transmitting device as described above and the low-orbit satellite communication and ranging integrated receiving device as described above.

[0021] According to another aspect of the present invention, a computer-readable storage medium is provided, the computer-readable storage medium including a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the steps of the method described above or the steps of the method described above.

[0022] In general, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

[0023] 1. The present invention first proposes a method for generating a low-orbit satellite communication and ranging integrated transmission signal based on OFDM. The pilot signal of OFDM adopts an ideal autocorrelation sequence. Its ideal autocorrelation allows the receiving end to calculate the correlation peak to obtain the number of sequence shifts to achieve ranging, but can only estimate the delay of integer multiples of the sampling interval. The ranging accuracy is related to the sampling frequency. In order to improve the ranging accuracy, the phase shift is considered. Because the fractional delay less than the sampling interval (that is, the sampling duration of a single sampling) will be reflected in the phase of the frequency domain subcarrier, the receiving end can determine the delay of the fractional multiple of the sampling interval in the frequency domain by finding the phase difference caused by the delay. After joint estimation in the time domain and the frequency domain, a more accurate delay estimate can be obtained to estimate the satellite-to-ground distance. Therefore, the method of the present invention can improve the accuracy of signal transmission delay estimation, thereby solving the technical problem of low ranging accuracy in the integration of ranging communication.

[0024] 2. The present invention also proposes the value of the ideal autocorrelation sequence and the specific distribution mode of the pilot signal and the constellation symbol in OFDM, and uses a genetic algorithm to jointly optimize the communication bit error rate and ranging accuracy of the system as the optimization goal, so as to obtain the ideal autocorrelation sequence and distribution mode that meet the actual communication and ranging performance requirements, so as to achieve the best communication bit error rate and ranging accuracy of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a block diagram of a low-orbit satellite communication and ranging integrated method provided by an embodiment of the present invention;

[0026] Figure 2 is a data and pilot resource unit mapping diagram provided by an embodiment of the present invention;

[0027] Figure 3 is a flow chart of a ranging algorithm based on a TOA algorithm provided by an embodiment of the present invention;

[0028] Figure 4 is a flow chart of optimization based on genetic algorithm provided by an embodiment of the present invention;

[0029] Figure 5 It is a detailed flow chart of a low-orbit satellite communication and ranging integrated method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Embodiment 1

[0032] A method for generating a low-orbit satellite communication and ranging integrated transmission signal, comprising:

[0033] Generate a pilot signal according to a preset ideal autocorrelation sequence, map the pilot signal and the constellation symbol to an OFDM resource unit according to a preset distribution method, and obtain an OFDM signal; perform OFDM modulation on the OFDM signal to generate a transmission signal;

[0034] If there is a communication task, the constellation symbol is obtained by modulating the data to be transmitted;

[0035] The transmitting signal is used for receiving at the receiving end to obtain a receiving signal, and the receiving signal is pre-compensated for Doppler frequency shift and sampled to obtain a discrete signal y k ; by y k Parse the data to be transmitted and k With the known pilot signal sampling sequence s k Perform autocorrelation calculation in the time domain to obtain the integer delay τ in the total signal transmission delay 1 ; The sampling sequence s k Shift p to get right and k Perform fast Fourier transform to obtain frequency domain data S and Y respectively; calculate the autocorrelation W of Z at the qth subcarrier and the q+Qth subcarrier to obtain the fractional delay τ in the total signal transmission delay 2, where Z is the autocorrelation equation of S and Y in the frequency domain; the integer delay τ 1 and fractional delay τ 2 The total signal transmission delay τ is added together, and combined with the speed of light, the estimated distance between the satellite and the ground is obtained.

[0036] The overall approach is Figure 1 As shown. The autocorrelation sequence used to generate the pilot signal is an ideal autocorrelation sequence with an autocorrelation close to 1. The reason is that the ideal autocorrelation allows the receiver to achieve ranging by calculating the correlation peak to obtain the number of sequence shifts, but can only estimate the delay of integer multiples of the sampling interval. The ranging accuracy is related to the sampling frequency. In order to improve the ranging accuracy, the phase shift is considered. Because the fractional delay less than the sampling interval (that is, the sampling duration of a single sampling) will be reflected in the phase of the frequency domain subcarrier, the receiver can determine the delay of the fractional multiple of the sampling interval in the frequency domain by finding the phase difference caused by the delay. After joint estimation in the time domain and the frequency domain, a more accurate delay estimate can be obtained to estimate the satellite-to-ground distance. Therefore, the method of this embodiment can improve the accuracy of signal transmission delay estimation, thereby solving the technical problem of low ranging accuracy in the integration of ranging and communication.

[0037] Specifically, the system model is a broadband satellite communication ranging system based on OFDM, and the data and pilot mapping is as follows: Figure 2 As shown. The OFDM waveform contains N sym symbols and N sc subcarriers, symbol duration is T, subcarrier frequency spacing is Δf, subcarrier center frequency is f c , each OFDM resource unit carries log 2 L communication bits or one pilot data bit, based on which, the pilot signal and the constellation symbol are mapped to the OFDM resource unit according to the preset distribution method. For the nth OFDM symbol and the mth subcarrier, the data sent is a m,n . Build N sym ×N sc The size of the matrix Z, whose elements are either 0 or 1. m,n =0 indicates that the communication signal is transmitted on the OFDM resource unit, z m,n =1 indicates that a pilot signal is transmitted on this OFDM resource unit.

[0038] As a preferred embodiment, the ZC sequence belongs to the constant amplitude zero autocorrelation sequence (CAZAC), which has a low peak-to-average power ratio, ideal periodic autocorrelation characteristics and good cross-correlation characteristics, and is still a CAZAC sequence after FFT, which can be used as an ideal autocorrelation sequence. The root index of the ZC sequence is R, and the length is N. When N is an odd number, the sequence expression is When N is an even number, the sequence expression is The root index R of the ZC sequence satisfies 1≤R<N, and gcd(R,N)=1, that is, R and N are relatively prime.

[0039] However, the strong Doppler frequency shift effect of the high-speed low-orbit satellite will cause signal transmission delay, thereby damaging the perfect correlation characteristics of the ideal autocorrelation sequence. The method of this embodiment uses the perfect correlation characteristics of the ZC sequence to estimate the signal transmission delay. In addition, the degree of damage to its correlation characteristics under the same Doppler frequency shift effect is related to the root index value, that is, it is related to the ideal autocorrelation sequence. Therefore, it can be used as a preferred implementation method. The ideal autocorrelation sequence is optimized based on the genetic algorithm with the best communication and ranging performance.

[0040] First, regarding the transmission delay estimation at the receiving end, the estimation process involves signal reception, as follows:

[0041] OFDM modulation is performed on the OFDM signal to generate a transmit signal, which is used by the receiving end to receive the received signal. The received signal is pre-compensated for Doppler frequency shift and sampled to obtain a discrete signal y k , and generates a local sampling sequence (ie, the sampling sequence of the pilot signal in the transmitted signal).

[0042] Specifically, due to the high speed of low-orbit satellites, each subcarrier in the OFDM waveform will produce a large Doppler frequency shift, affecting the orthogonality of the subcarriers in the OFDM waveform. A processing unit is added to the receiving end to estimate and compensate for the Doppler frequency shift of each subcarrier, thereby reducing the impact of the Doppler frequency shift on system performance.

[0043] Low-orbit satellites usually revolve around the earth at a constant speed in an orbit of 400 to 2000 kilometers. Assuming that the satellite orbit is circular, the Doppler frequency shift at the ground receiver (i.e., the receiving end) is calculated based on the spherical geometry. The calculation formula is:

[0044] Medium E is the radius of the earth, r is the orbital radius, is the estimated angular distance from the Earth’s surface along the satellite’s orbit, θmax is the maximum visible elevation angle of the satellite, and ω F (t) is the angular velocity of the satellite, which is approximately a constant and is expressed as ω F (t)≈ω S -ω E cosi, where ω S is the average angular velocity of the satellite, ω E is the angular velocity of the Earth’s rotation, and i is the inclination of the satellite’s orbit.

[0045] Low-orbit communication satellites mostly operate in the Ku band (12-18GHz) and Ka band (27-40GHz). Taking the Starlink signal downlink operating frequency of 11.325GHz as an example, the radius of the earth is 6370km, the orbit radius is 6920km, the maximum elevation angle of the satellite is 30°, the satellite movement speed is 7.5km / s, and the maximum Doppler frequency shift caused by position changes is about 232.56kHz.

[0046] The transmitted signal obtained by OFDM modulation is expressed as After the satellite-to-ground channel transmission distance d, the frequency offset compensation is performed according to the calculated Doppler frequency shift, and the received signal is Among them, A is the signal amplitude received after the transmitted signal is transmitted through the channel, τ is the transmission delay, The mean is 0 and the variance is σ 2 Gaussian white noise. The sampling time of a single sampling is T s =T / N sc Sample y(t) to get the sampling sequence y of the received signal k (i.e. discrete signal), Since the pilot sequence information is known to the transmitter and the receiver, the sampling sequence of the local transmission signal is It should be noted that, k Parse and obtain the data to be transmitted, completing the signal transmission task.

[0047] Next, the sampled y k Autocorrelation operations are performed between the local sampling sequence in the time domain and frequency domain respectively to estimate the delay, obtain the corresponding transmission distance, and complete the ranging task.

[0048] Specifically, the ranging algorithm process based on the TOA algorithm is as follows: Figure 3 As shown. k With s k Perform autocorrelation calculation to obtain the sampling time shift number with the largest autocorrelation peak value The corresponding delay is τ 1 =pT s , the superscript * indicates conjugation.

[0049] Since only integer delays can be estimated in the time domain, fractional delays are estimated in the frequency domain. k Shift p to get For the time domain sampling sequence and k Perform FFT respectively to obtain frequency domain data S and Y. S and Y have a phase difference Δθ caused by fractional delay at the same subcarrier number in the frequency domain, so the fractional delay is estimated based on the generated phase difference.

[0050] The phase difference of the qth subcarrier is Δθ 1 =2π(q / T)·τ 2 , the phase difference of the q+Qth subcarrier is Δθ 2 =2π((q+Q) / T)·τ 2 , then Δθ 2 -Δθ 1 =2π(Q / T)·τ 2 . Autocorrelation processing of frequency domain data is The phase difference between Q subcarriers is estimated as angle(W), where Q is the frequency domain correlation interval and can be adjusted randomly. The fractional delay is τ 2 =angle(W)·T / (2πQ).

[0051] Delay the integer τ 1 and fractional delay τ 2 Add together the total signal transmission delay τ = τ 1 +τ 2 , multiplied by the speed of light c, we get the estimated distance between the star and the ground:

[0052] This method generates a pilot signal through a ZC sequence and measures the distance between the satellite and the receiver based on the Time of Arrival (TOA) ranging method, thus providing a prerequisite for satellite three-point positioning.

[0053] Secondly, regarding the optimization of the ideal autocorrelation sequence, since the distribution mode of the pilot signal in the OFDM waveform also affects the ranging and communication performance, the joint optimization of the ideal autocorrelation sequence and the above distribution mode can be achieved through simulation at the receiving end.

[0054] By establishing an optimization function for the system communication and ranging performance, the communication bit error rate and ranging error are minimized based on a genetic algorithm, and the root index value of the ZC sequence and the pilot distribution matrix are obtained, so as to determine the optimal ZC sequence and the distribution of the pilot signal and the modulated constellation symbol in the OFDM waveform. Based on the optimal ZC sequence and distribution method, communication and ranging tasks are performed.

[0055] The following takes the root index value of the ZC sequence and the pilot distribution matrix as an example for detailed description.

[0056] Establish the optimization function f = wf com +(1-w)f loc ,0≤w≤1Optimize the root index value of the ZC sequence and the distribution of the pilot on the OFDM resource element (RE), minimize the communication bit error rate and ranging error, and the purpose of the optimization function is Among them, the communication bit error rate is That is, the ratio of the number of received erroneous data bits to the total number of transmitted bits; the ranging error is That is, the relative error of the measured distance, where d is the actual distance between the satellite and the receiver.

[0057] The variables of this model are the root index value R of the ZC sequence and the pilot distribution, which can be expressed as is the coordinate of the pilot on RE, the number of variables is N pilot +1. The constraints are 1≤R<N, gcd(R,N)=1, 1≤l 1 ≤N sc , 1≤l 2 ≤N sym 、x g ≠x l .

[0058] The genetic algorithm-based process is as follows Figure 4 Assume that the ZC sequence root index value and the pilot distribution coordinates are selected as N GA =5, ZC sequence length N = 65, OFDM subcarrier number N sc =1024, number of symbols N sym = 10, the root index value and the pilot distribution coordinates are constructed using binary coding, and the encoded variable R is a 6-bit binary string (2 6 =64), each pilot frequency abscissa is a 10-bit binary string (2 10 =1024), ordinate is a 4-bit binary string (2 3 =8<10<16=2 4 ), a random number generator is used to generate the root index value and the pilot distribution coordinates and satisfy the constraints to obtain the binary code string C 1 ,…,C 5 .

[0059] The fitness function is set to According to the fitness f′, the fitness value of each encoding string is calculated to obtain Eval(C 1 )、…、Eval(C 5 ), compare and get the best code string fitness value and the corresponding code string, assuming that Eval(C 3 ) and C 3 .

[0060] Use the roulette wheel selection algorithm to calculate the total fitness value Eval all =Eval(C 1 )+…+Eval(C 5), calculate the ratio of the fitness value of each code string to the total fitness value, and get the new code string C based on the [0,1] random numbers generated 5 times and the selected code string 1 ′, …, C 5 ′.

[0061] Probability P c The value is generally 0.4-0.99. Generate a [0,1] random number for each new code string to determine whether the new code string participates in the exchange. If the random number is less than P c Then the code string is exchanged. When each pair of code strings is exchanged, a natural number is randomly generated as the exchange bit. The new code string after the exchange is C 1 ″, …, C 5 ″.

[0062] Probability P m The value is generally 0.001-0.1. Generate a [0,1] random number for the root index value and pilot distribution coordinates of each transformed new code string. If the random number is less than P m , then change the root index value and the pilot distribution coordinate value, otherwise do not change the value, and get the new code string C 1 ″′, …, C 5 ″′. Recalculate the code string fitness value, update the best code string fitness value and the corresponding code string, assuming that Eval(C 1 ″′) and C 1 ″′.

[0063] The number of iterations is increased by 1 and the above process is continued until the termination condition is met, the binary code string is decoded, and the optimal value of the ZC sequence root index and the optimal distribution of the pilot on the OFDM resource unit are obtained.

[0064] The preferred solution of this embodiment balances the communication performance and ranging performance of the system. In the optimization function, weight factors are assigned to the communication performance and ranging performance, and the weight factors are adjusted according to different requirements. Then, the genetic algorithm is optimized to obtain the optimal solution of the system, so that the system can adapt to different requirements.

[0065] In general, the optimization using genetic algorithm includes the following steps:

[0066] S1. Establish an optimization function for system communication and ranging performance, assign corresponding weights to communication bit error rate and ranging error respectively, and the sum of the weights is 1;

[0067] S2, establishing an optimization model based on genetic algorithm according to system parameters and optimization function;

[0068] S3. Output the ZC sequence root index value and pilot distribution matrix according to the genetic algorithm.

[0069] Wherein, step S1 comprises:

[0070] The number of pilots and the length of the ZC sequence are fixed, and the optimization function is the weighted sum of the communication bit error rate and the ranging error. The communication bit error rate is given a weight of w and the ranging error a weight of 1-w.

[0071] Step S2 includes:

[0072] S21, searching for a root index value according to the ZC sequence root index value being less than the sequence length and being coprime with the sequence length;

[0073] S22, pilot distribution indicates that from N sym ·N sc Select N from the positions pilot positions, the number of possible choices is Moreover, the size increases exponentially as the parameters increase, and a genetic algorithm is used for fast search.

[0074] Step S3 includes:

[0075] S31, Initialize N GA A ZC sequence root index value and pilot distribution coordinates are selected, and their initial values ​​are generated by a random number generator and meet the constraints;

[0076] S32, taking the inverse of the optimization function to obtain a fitness function, respectively calculating the function value of each ZC sequence root index value and pilot distribution coordinate, and saving the maximum value and its corresponding root index value and pilot distribution coordinate;

[0077] S33, using the roulette wheel selection algorithm to select the ZC sequence root index value and the pilot distribution coordinates, and regenerate N GA ZC sequence root index values ​​and pilot distribution coordinates;

[0078] S34. According to the probability P c The exchanged parts of the root index value and the pilot distribution coordinate of the ZC sequence are taken to generate two new root index values ​​and pilot distribution coordinates, which are selected and replaced with the original values, and the unexchanged parts are retained;

[0079] S35. According to probability P m The root index value and the pilot distribution coordinates are numerically changed and the original values ​​are replaced, and the unchanged parts are retained;

[0080] S36, recalculating the function values ​​of each ZC sequence root index value and pilot distribution coordinate, if the maximum value is greater than the original maximum value, replacing the original value with the ZC sequence root index value and pilot distribution coordinate corresponding to the maximum value;

[0081] S37, the number of iterations is increased by one. When the number of iterations reaches the maximum number of iterations, the algorithm ends and outputs the optimal value of the current ZC sequence root index and the optimal pilot distribution. Otherwise, it returns to S433.

[0082] This embodiment uses a genetic algorithm to obtain a ZC sequence root index value, so that when the ZC sequence length is fixed, the influence of Doppler frequency shift on the autocorrelation characteristic of the ZC pilot sequence is minimized, thereby achieving good communication and ranging performance of the system.

[0083] In OFDM system, ideal autocorrelation sequence is used for communication and ranging, and ideal autocorrelation sequence acts as a pilot for channel estimation; autocorrelation estimation delay ranging is performed in time domain and frequency domain, because ZC sequence is a constant amplitude zero autocorrelation sequence, and has good autocorrelation in both time domain and frequency domain; two-step autocorrelation in time domain and frequency domain can accurately measure transmission delay and thus estimate transmission distance. In addition, signal compatibility can be improved: ZC sequence is superimposed on OFDM as the minimum resource unit, and the two will not interfere with each other, and the signal has good compatibility.

[0084] Embodiment 2

[0085] A low-orbit satellite communication and ranging integrated transmission device comprises: a processor, a memory storing instructions executable by the processor, and a data transceiver for data transmission and / or reception; wherein, when the instructions are executed by the processor, the low-orbit satellite communication and ranging integrated transmission signal generation method as described above is executed.

[0086] The relevant technical solution is the same as the previous embodiment and will not be described again here.

[0087] Embodiment 3

[0088] A low-orbit satellite communication ranging integrated receiving signal analysis method, comprising:

[0089] The Doppler frequency shift pre-compensation of the received signal from the transmitter is performed and the discrete signal y is obtained by sampling. k ; by y k Parse the data to be transmitted and k With the known pilot signal sampling sequence s k Perform autocorrelation calculation in the time domain to obtain the integer delay τ in the total signal transmission delay 1 ; The sampling sequence s k Shift p to get right and k Perform fast Fourier transform to obtain frequency domain data S and Y respectively; calculate the autocorrelation W of Z at the qth subcarrier and the q+Qth subcarrier to obtain the fractional delay τ in the total signal transmission delay 2 , where Z is the autocorrelation equation of S and Y in the frequency domain; the integer delay τ 1 and fractional delay τ 2 The total signal transmission delay τ is added together, and combined with the speed of light, the estimated distance between the satellite and the ground is obtained;

[0090] Among them, the received signal comes from the transmit signal generated and transmitted by the transmitter, and the transmit signal is generated in the following manner: a pilot signal is generated according to a preset ideal autocorrelation sequence, the pilot signal and the constellation symbol are mapped to the OFDM resource unit according to a preset distribution method to obtain an OFDM signal; and the OFDM signal is OFDM modulated to generate a transmit signal.

[0091] Preferably, the ideal autocorrelation sequence is a ZC sequence.

[0092] Preferably, the ideal autocorrelation sequence and distribution are optimized based on a genetic algorithm with the best communication and ranging performance.

[0093] The relevant technical solution is the same as the previous embodiment and will not be described again here.

[0094] Embodiment 4

[0095] A low-orbit satellite communication and ranging integrated receiving device comprises: a processor, a memory storing instructions executable by the processor, and a data transceiver for data transmission and / or reception; wherein, when the instructions are executed by the processor, the low-orbit satellite communication and ranging integrated receiving signal analysis method as described above is executed.

[0096] The relevant technical solution is the same as the aforementioned embodiment and will not be described again here.

[0097] Embodiment 5

[0098] A low-orbit satellite communication and ranging integrated system comprises the low-orbit satellite communication and ranging integrated transmitting device as described above and the low-orbit satellite communication and ranging integrated receiving device as described above.

[0099] The relevant technical solution is the same as the aforementioned embodiment and will not be described again here.

[0100] Embodiment 6

[0101] A computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the steps of the method described above or the steps of the method described above.

[0102] Specifically, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as a hard disk, an internal memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0103] The relevant technical solution is the same as the aforementioned embodiment and will not be described again here.

[0104] In general, the present invention discloses a low-orbit satellite communication and ranging integrated method and system, which belongs to the field of satellite communication and ranging, such as Figure 5 As shown, the method mainly includes the following steps: generate a pilot signal according to an ideal autocorrelation sequence, and then map it together with the modulated constellation symbol to an OFDM resource element (RE); generate a transmit signal, perform Doppler frequency shift pre-compensation on the received signal at the receiving end, sample to obtain a discrete signal and generate a local sampling sequence; perform autocorrelation operations on the received discrete signal and the local sequence in the time domain and frequency domain respectively to estimate the delay and obtain the corresponding transmission distance. In addition, it is proposed to establish an optimization function for the communication and ranging performance of the system, minimize the communication bit error rate and ranging error based on a genetic algorithm, and obtain the optimal ideal autocorrelation sequence and pilot distribution matrix. Using the method of the present invention, the system makes full use of time and frequency resources, can realize the ranging function while providing reliable communication, and can balance the communication performance and ranging performance, greatly promoting the development of integrated communication and positioning. It should be noted that Figure 5 The dotted box part is the relevant processing steps of OFDM modulation.

[0105] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for generating a low-orbit satellite communication and ranging integrated transmission signal, characterized in that: include: Generate a pilot signal according to a preset ideal autocorrelation sequence, and map the pilot signal and the constellation symbol to an OFDM resource unit according to a preset distribution method to obtain an OFDM signal; Performing OFDM modulation on the OFDM signal to generate a transmission signal; Wherein, if there is a communication task, the constellation symbol is obtained by modulating the data to be transmitted; The transmitting signal is used for receiving at the receiving end to obtain a receiving signal, and the receiving signal is pre-compensated for Doppler frequency shift and sampled to obtain a discrete signal y k ; by y k Parse the data to be transmitted and k With the known pilot signal sampling sequence s k Perform autocorrelation operation in the time domain to obtain the integer delay τ1 in the total signal transmission delay; convert the sampling sequence s k Shift p to get right and k Perform fast Fourier transform respectively to obtain frequency domain data S and Y; calculate the autocorrelation W of Z at the qth subcarrier and the q+Qth subcarrier to obtain the fractional delay τ2 in the total signal transmission delay, where Z is the autocorrelation operation formula of S and Y in the frequency domain; add the integer delay τ1 and the fractional delay τ2 to obtain the total signal transmission delay τ, and combine it with the speed of light to obtain the estimated distance between the satellite and the ground.

2. The method for generating a low-orbit satellite communication and ranging integrated transmission signal according to claim 1, characterized in that: The ideal autocorrelation sequence is a ZC sequence.

3. The method for generating a low-orbit satellite communication and ranging integrated transmission signal according to claim 1, wherein: The ideal autocorrelation sequence and the distribution mode are optimized based on a genetic algorithm with the best communication and ranging performance.

4. A low-orbit satellite communication and ranging integrated transmitting device, characterized in that: include: A processor, a memory storing instructions executable by the processor, and a data transceiver for sending and / or receiving data; wherein, when the instructions are executed by the processor, the method for generating a low-orbit satellite communication and ranging integrated transmission signal as described in any one of claims 1 to 3 is executed.

5. A low-orbit satellite communication and ranging integrated receiving signal analysis method, characterized in that: include: The Doppler frequency shift pre-compensation of the received signal from the transmitter is performed and the discrete signal y is obtained by sampling. k ; by y k Parse the data to be transmitted and k With the known pilot signal sampling sequence s k Perform autocorrelation operation in the time domain to obtain the integer delay τ1 in the total signal transmission delay; convert the sampling sequence s k Shift p to get right and k Perform fast Fourier transform respectively to obtain frequency domain data S and Y; calculate the autocorrelation W of Z at the qth subcarrier and the q+Qth subcarrier to obtain the fractional delay τ2 in the total signal transmission delay, where Z is the autocorrelation operation formula of S and Y in the frequency domain; add the integer delay τ1 and the fractional delay τ2 to obtain the total signal transmission delay τ, and combine it with the speed of light to obtain the estimated distance between the satellite and the ground; Among them, the received signal comes from the transmit signal generated and transmitted by the transmitting end, and the transmit signal is generated in the following manner: a pilot signal is generated according to a preset ideal autocorrelation sequence, and the pilot signal and the constellation symbol are mapped to the OFDM resource unit according to a preset distribution method to obtain an OFDM signal; and the OFDM signal is OFDM modulated to generate a transmit signal.

6. The low-orbit satellite communication and ranging integrated received signal analysis method according to claim 5, characterized in that: The ideal autocorrelation sequence is a ZC sequence.

7. The low-orbit satellite communication and ranging integrated received signal analysis method according to claim 5, characterized in that: The ideal autocorrelation sequence and the distribution mode are optimized based on a genetic algorithm with the best communication and ranging performance.

8. A low-orbit satellite communication and ranging integrated receiving device, characterized in that: include: A processor, a memory storing instructions executable by the processor, and a data transceiver for sending and / or receiving data; wherein, when the instructions are executed by the processor, the low-orbit satellite communication and ranging integrated receiving signal analysis method as described in any one of claims 5 to 7 is executed.

9. A low-orbit satellite communication and ranging integrated system, characterized in that: It includes the low-orbit satellite communication and ranging integrated transmitting device as described in claim 4 and the low-orbit satellite communication and ranging integrated receiving device as described in claim 8.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to perform the steps of the method according to any one of claims 1 to 3 or the steps of the method according to any one of claims 5 to 7.

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