A low-orbit satellite communication and ranging integrated signal generation and analysis method

Abstract

This invention belongs to the field of satellite communication ranging technology, specifically relating to an integrated signal generation and analysis method for low-Earth orbit satellite communication ranging. The method includes: generating pilot signals based on an ideal autocorrelation sequence, then mapping these signals together with modulated constellation symbols onto OFDM resource cells; generating a transmit signal; performing Doppler frequency shift pre-compensation on the received signal at the receiving end; sampling to obtain a discrete signal and generating a local sampling sequence; and performing autocorrelation operations on the received discrete signal and the local sequence in the time and frequency domains respectively to estimate the time delay and obtain the corresponding transmission distance. The method can further establish an optimization function for system communication and ranging performance, minimizing the communication bit error rate and ranging error based on a genetic algorithm to obtain the autocorrelation sequence and pilot distribution matrix. Using this method, the system can achieve ranging functionality while maintaining reliable communication, and a trade-off can be struck between communication performance and ranging performance.

Description

Technical Field

[0001] This invention belongs to the field of satellite communication ranging technology, and more specifically, relates to an integrated signal generation and analysis method for low-orbit satellite communication ranging. Background Technology

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

[0003] Existing communication and navigation satellite systems have maintained independent development due to their different requirements in signal transmission and detection, employing different modulation methods and receiving algorithms. They occupy different frequency bands and bandwidths, resulting in low utilization efficiency of resources such as frequency and orbit. However, both are based on electromagnetic wave propagation, and their respective systems include modules for signal generation, analog-to-digital conversion, power amplification, and digital signal processing. Therefore, the integration of communication and navigation has unique advantages. A communication-navigation fusion system possesses advantages that individual systems lack and provides additional performance gains for the integrated system. Its integrated implementation can improve spectrum utilization, reduce system duplication, and has significant social and economic value.

[0004] To achieve high-speed transmission and high-precision ranging and positioning within limited bandwidth, waveform design plays a crucial role in integrated communication and navigation systems. However, communication signals and navigation signals differ significantly in their signal structures. Communication signals are typically bidirectional, discontinuous digital signals, while navigation signals are usually broadband, continuous broadcast signals. The combination of the two must consider signal compatibility, as well as performance indicators such as peak-to-average power ratio, bit error rate, and ranging accuracy.

[0005] Existing low-Earth orbit satellite communication constellations use segmented pilot signals superimposed on the communication signal, occupying a portion of the OFDM signal subcarriers for transmission, thus ensuring the continuity of the ranging pilot signal in the time and frequency domain. Autocorrelation estimation in the time domain yields the corresponding distance value, determining ranging accuracy and communication resource utilization. However, the superposition of the segmented pilot signals on the communication signal only allows for three configuration options, lacking flexibility and unable to be adjusted according to requirements; performing autocorrelation calculations solely in the time domain is insufficient to accurately estimate delay and thus obtain accurate distance estimates; and the system's ranging accuracy and communication performance are mutually exclusive, making it impossible to adjust their performance to maximize performance based on external needs. Summary of the Invention

[0006] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a signal generation and analysis method for low-orbit satellite communication ranging integration, which aims 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 objectives, according to one aspect of the present invention, a method for generating integrated low-Earth orbit satellite communication ranging transmission signals is provided, comprising:

[0008] A pilot signal is generated based on a preset ideal autocorrelation sequence. The pilot signal and constellation symbols are then mapped onto OFDM resource cells according to a preset distribution method to obtain an OFDM signal. The OFDM signal is then OFDM modulated to generate a transmit signal.

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

[0010] The transmitted signal is used by the receiving end to receive the received signal, and the received signal is subjected to Doppler frequency shift pre-compensation and sampled to obtain the discrete signal y. k ; by y k The data to be transmitted is obtained by parsing, and y k With the known pilot signal sampling sequence s k Perform autocorrelation in the time domain to obtain the integer delay τ1 in the total signal transmission delay; then process the sampled sequence s. k Shift p to get right and y k Perform Fast Fourier Transform (FFT) to obtain frequency domain data S and Y respectively; calculate the autocorrelation W of Z at the q-th subcarrier and the (q+Q)-th subcarrier to obtain the fractional delay τ2 in the total signal transmission delay, where Z is the autocorrelation expression 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.

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

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

[0013] According to another aspect of the present invention, a low-Earth orbit satellite communication ranging integrated transmission device is provided, comprising: 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-Earth orbit satellite communication ranging integrated transmission signal generation method described above is executed.

[0014] According to another aspect of the present invention, a method for integrated ranging and receiving signal analysis in low-Earth orbit satellite communication is provided, comprising:

[0015] The received signal from the transmitter is pre-compensated for Doppler frequency shift and sampled to obtain the discrete signal y. k ; by y k The data to be transmitted is obtained by parsing, and y k With the known pilot signal sampling sequence s k Perform autocorrelation in the time domain to obtain the integer delay τ1 in the total signal transmission delay; then process the sampled sequence s. k Shift p to get right and y k Perform Fast Fourier Transform (FFT) on each subcarrier to obtain frequency domain data S and Y; calculate the autocorrelation W of Z at the q-th subcarrier and the (q+Q)-th subcarrier to obtain the fractional delay τ2 in the total signal transmission delay, where Z is the autocorrelation expression 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 this with the speed of light to obtain the estimated distance between the satellite and the ground.

[0016] The received signal is derived from the transmitted signal generated and transmitted by the transmitting end, and the transmitted signal is generated in the following manner: a pilot signal is generated according to a preset ideal autocorrelation sequence, and the pilot signal and constellation symbols are mapped together to OFDM resource units according to a preset distribution method to obtain an OFDM signal; the OFDM signal is then OFDM modulated to generate the transmitted signal.

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

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

[0019] According to another aspect of the present invention, a low-Earth orbit satellite communication ranging integrated receiving device is provided, comprising: 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-Earth orbit satellite communication ranging integrated receiving signal analysis method as described above is executed.

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

[0021] According to another aspect of the 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, it controls the device where the storage medium is located to perform the steps of the method described above or the steps of the method described above.

[0022] In summary, compared with the prior art, the solutions conceived by this invention have the following main advantages:

[0023] 1. This invention first proposes a method for generating integrated ranging transmission signals for low-Earth orbit satellite communication based on OFDM. The OFDM pilot signal uses an ideal autocorrelation sequence. Its ideal autocorrelation allows the receiver to calculate the sequence shift by calculating the correlation peak, thus achieving ranging. However, it can only estimate the delay for integer multiples of the sampling interval. Ranging accuracy is related to the sampling frequency. To improve ranging accuracy, phase shift is considered because a fractional delay smaller than the sampling interval (i.e., the sampling duration of a single sample) is reflected in the phase of the subcarrier in the frequency domain. The receiver can determine the fractional delay for the sampling interval by finding the phase difference caused by the delay in the frequency domain. After joint estimation in the time and frequency domains, a more accurate delay estimate can be obtained, thus estimating the satellite-to-ground distance. Therefore, the method of this invention can improve the accuracy of signal transmission delay estimation, thereby solving the technical problem of low ranging accuracy in integrated ranging and communication.

[0024] 2. This invention also proposes to use a genetic algorithm to optimize the communication error rate and ranging accuracy of the system by taking the values ​​of the ideal autocorrelation sequence and the specific distribution of pilot signals and constellation symbols in OFDM. This results in an ideal autocorrelation sequence and distribution that meet the actual communication and ranging performance requirements, thereby achieving the best performance of the system in terms of communication error rate and ranging accuracy. Attached Figure Description

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

[0026] Figure 2 This is a data and pilot resource unit mapping diagram provided in the embodiments of the present invention;

[0027] Figure 3 This is a flowchart of the ranging algorithm based on the TOA algorithm provided in an embodiment of the present invention;

[0028] Figure 4 This is a flowchart of the optimization process based on genetic algorithm provided in an embodiment of the present invention;

[0029] Figure 5 This is a detailed flowchart of an integrated low-orbit satellite communication ranging method provided in an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Example 1

[0032] A method for generating integrated ranging and transmission signals for low-Earth orbit satellite communication includes:

[0033] A pilot signal is generated based on a preset ideal autocorrelation sequence. The pilot signal and constellation symbols are then mapped onto OFDM resource cells according to a preset distribution method to obtain an OFDM signal. The OFDM signal is then OFDM modulated to generate a transmit signal.

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

[0035] The transmitted signal is used by the receiving end to receive the received signal, and the received signal is subjected to Doppler frequency shift pre-compensation and sampled to obtain the discrete signal y. k ; by y k The data to be transmitted is obtained by parsing, and y k With the known pilot signal sampling sequence s k Perform autocorrelation in the time domain to obtain the integer delay τ1 in the total signal transmission delay; then process the sampled sequence s. k Shift p to get right and y k Perform Fast Fourier Transform (FFT) to obtain frequency domain data S and Y respectively; calculate the autocorrelation W of Z at the q-th subcarrier and the (q+Q)-th subcarrier to obtain the fractional delay τ2 in the total signal transmission delay, where Z is the autocorrelation expression 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.

[0036] Overall approach such as Figure 1As 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 calculate the sequence shift by calculating the correlation peak and thus achieve ranging, but it can only estimate the delay of integer multiples of the sampling interval. The ranging accuracy is related to the sampling frequency. To improve the ranging accuracy, the phase shift is considered because the fractional delay smaller than the sampling interval (i.e., the sampling duration of a single sample) will be reflected in the phase of the subcarrier in the frequency domain. The receiver can determine the delay of fractional multiples of the sampling interval by finding the phase difference caused by the delay in the frequency domain. After joint estimation in the time and frequency domains, a more accurate delay estimate can be obtained, thereby estimating the satellite-to-ground distance. Therefore, the method in 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 There are 1 subcarrier, the symbol duration is T, the subcarrier frequency interval is Δf, and the subcarrier center frequency is f. c Each OFDM resource element carries log₂L communication bits or one pilot data bit. Based on this, the pilot signal and constellation symbols are mapped onto the OFDM resource element according to a preset distribution. For the nth OFDM symbol and the mth subcarrier transmitting data a m,n Establish N sym ×N sc A matrix Z of size Z, whose elements take values ​​of 0 or 1. When z m,n =0 indicates that communication signals are transmitted on this OFDM resource unit, z m,n =1 indicates that pilot signals are transmitted on this OFDM resource unit.

[0038] Preferably, the ZC sequence belongs to the Constant Amplitude Zero Auto-Corelation (CAZAC) sequence, possessing a low peak-to-average power ratio, ideal periodic autocorrelation characteristics, and good cross-correlation properties. Furthermore, it remains a CAZAC sequence after FFT, making it a suitable candidate for an ideal autocorrelation sequence. The root index of the ZC sequence is R, and its length is N. When N is odd, the sequence expression is: When N is even, 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 coprime.

[0039] However, the strong Doppler shift effect of high-speed low-Earth orbit satellites can lead to signal transmission delay, thereby impairing the perfect correlation characteristics of the ideal autocorrelation sequence. This embodiment utilizes the perfect correlation characteristics of the ZC sequence for signal transmission delay estimation. Furthermore, the degree of impairment of correlation characteristics under the same Doppler shift effect is related to the root index value, which is also related to the ideal autocorrelation sequence. Therefore, as a preferred implementation method, the ideal autocorrelation sequence is optimized based on a genetic algorithm to achieve optimal communication and ranging performance.

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

[0041] OFDM modulation is applied to the OFDM signal to generate a transmit signal. This transmit signal is used at the receiver to obtain the receive signal. Doppler frequency shift pre-compensation is performed on the receive signal, and it is then sampled to obtain the discrete signal y. k And generate a local sampling sequence (i.e., the sampling sequence of the pilot signal in the transmitted signal).

[0042] Specifically, due to the high speed of low-Earth orbit satellites, each subcarrier in the OFDM waveform experiences a significant Doppler shift, affecting the orthogonality of the subcarriers. Adding a processing unit at the receiver to estimate and compensate for the Doppler shift of each subcarrier reduces the impact of the Doppler shift on system performance.

[0043] Low Earth orbit (LEO) satellites typically orbit the Earth at a constant speed in orbits between 400 and 2000 kilometers. Assuming the satellite orbit is circular, the Doppler shift at the ground receiver (i.e., the receiving end) can be calculated using the following formula:

[0044] Chinese r E r is the Earth's radius, and r is the orbital radius. θmax is the estimated angular distance from the Earth's surface along the satellite's orbit, θmax is the satellite's maximum visible elevation angle, and ω is the angular distance from the Earth's surface along the satellite's orbit. F (t) represents the angular velocity of the satellite, which is approximately constant and denoted as ω. F (t)≈ω S -ω E cosi, where ω S Let ω be the average angular velocity of the satellite's motion. E Let ω be the angular velocity of Earth's rotation, and i be the inclination of the satellite's orbit.

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

[0046] The transmitted signal obtained by OFDM modulation is represented as After a transmission distance d via the satellite-to-ground channel, frequency offset compensation is performed based on the calculated Doppler frequency shift, and the received signal is... Where A is the amplitude of the received signal after the transmitted signal has passed through the channel, and τ is the transmission delay. To conform to a mean of 0 and a variance of σ 2 Gaussian white noise. The sampling duration T for a single sample. s =T / N sc The sampled sequence y of the received signal is obtained by sampling y(t). k (i.e., discrete signal) Since the pilot sequence information is known at both the transmitter and receiver, the sampling sequence of the locally transmitted signal is: It should be noted that, by y k The data to be transmitted is parsed to complete the signal transmission task.

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

[0048] Specifically, the ranging algorithm based on the TOA algorithm is as follows: Figure 3 As shown. y k With s k Perform autocorrelation calculations to obtain the sampling duration shift that maximizes the autocorrelation peak. The corresponding time delay is τ1 = pT s The superscript * indicates taking the conjugate.

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

[0050] The phase difference of the q-th subcarrier is Δθ1 = 2π(q / T)·τ2, and the phase difference of the (q+Q)-th subcarrier is Δθ2 = 2π((q+Q) / T)·τ2. Therefore, Δθ2 - Δθ1 = 2π(Q / T)·τ2. Autocorrelation processing is then performed on the frequency domain data. The estimated value of the phase difference separated by Q subcarriers is angle(W), where Q is the frequency domain correlation interval that can be randomly adjusted. The fractional time delay is τ2 = angle(W)·T / (2πQ).

[0051] Adding the integer delay τ1 and the fractional delay τ2 gives the total signal transmission delay τ = τ1 + τ2. Multiplying this by the speed of light c gives the estimated distance between the satellite and the Earth.

[0052] This method generates pilot signals using ZC sequences and uses Time of Arrival (TOA) ranging to measure the distance between the satellite and the receiver, providing a prerequisite for satellite three-point positioning.

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

[0054] By establishing an optimization function for system communication and ranging performance, and minimizing the communication bit error rate and ranging error based on a genetic algorithm, the root index value of the ZC sequence and the pilot distribution matrix are obtained, thereby determining the optimal ZC sequence and the distribution of pilot signals and modulated constellation symbols in the OFDM waveform. Based on the optimal ZC sequence and distribution, communication and ranging tasks are performed.

[0055] The following section will use the root index value and pilot distribution matrix of the ZC sequence as an example for a detailed explanation.

[0056] Establish the optimization function f = wf com +(1-w)f loc Optimize the ZC sequence root index values ​​and pilot distribution on OFDM resource elements (REs) to minimize the communication bit error rate and ranging error. The optimization function aims to achieve the following: (0≤w≤1) 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; ranging error is... This refers to the relative error in distance measurement, where d is the actual distance between the satellite and the receiver.

[0057] For the variables in this model, which are the root index value R of the ZC sequence and the pilot distribution, it is expressed as follows: Let N be the coordinates of the pilot on RE, with N variables. pilot +1. The constraints are 1≤R<N, gcd(R,N)=1, 1≤l1≤N sc 1≤l2≤N sym x g ≠x l .

[0058] The process based on genetic algorithms is as follows: Figure 4 As shown. Assume the ZC sequence root index and pilot distribution coordinates are chosen as N. GA =5, ZC sequence length N=65, OFDM subcarrier number N sc =1024, the sign number N sym =10, using binary encoding to construct the root index value and pilot distribution coordinates, the encoded variable R is a 6-bit binary string (2 6 =64), the x-axis of each pilot is For a 10-bit binary string (2 10 =1024), ordinate For a 4-bit binary string (2 3 =8 < 10 < 16 = 2 4 The root index value and pilot distribution coordinates are generated using a random number generator and the constraints are satisfied to obtain the binary encoded strings C1, ..., C5.

[0059] The fitness function is set to The fitness values ​​of each encoded string are calculated based on the fitness f′, resulting in Eval(C1), ..., Eval(C5). The fitness values ​​of the best encoded string and the corresponding encoded strings are then compared, assuming they are Eval(C3) and C3.

[0060] The roulette wheel selection algorithm is used to calculate the sum of fitness values, Eval. all =Eval(C1)+…+Eval(C5), calculate the ratio of the fitness value of each encoded string to the sum of the fitness values, and obtain the new encoded strings C1′, …, C5′ based on the five generated [0,1] random numbers and the selected encoded strings.

[0061] probability P c The value typically ranges from 0.4 to 0.99. For each new encoded string, a random number in the range [0,1] is generated to determine whether the new encoded string participates in the swap. If this random number is less than P... c Then, the swaps are performed. When swapping each pair of encoded strings, a natural number is randomly generated as the swap bit. The new encoded strings after the swap are C1″, ..., C5″.

[0062] probability P mThe value typically ranges from 0.001 to 0.1. For each transformed new encoded string, a random number in the range [0,1] is generated based on the root index and pilot distribution coordinates. If this random number is less than P... m If the root index value and pilot distribution coordinates are changed, then the values ​​are changed; otherwise, the values ​​are not changed, resulting in new encoded strings C1″′, ..., C5″′. The fitness values ​​of the encoded strings are recalculated, and the optimal fitness values ​​and corresponding encoded strings are updated, assuming they are Eval(C1″′) and C1″′.

[0063] Increment the iteration count by 1 and continue the above process until the termination condition is met. Decode the binary encoded string to obtain the optimal value of the ZC sequence root index and the optimal distribution of the pilot on the OFDM resource unit.

[0064] This embodiment prioritizes a balance between system communication performance and ranging performance. Weighting factors are assigned to communication and ranging performance in the optimization function, and these factors are adjusted according to different requirements. A genetic algorithm is then used to optimize the system and obtain the optimal solution, enabling the system to adapt to different needs.

[0065] In summary, the optimization process using genetic algorithms includes the following steps:

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

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

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

[0069] Step S1 includes:

[0070] With a fixed number of pilots and ZC sequence length, the optimization function is the weighted sum of the communication error rate and the ranging error, with the communication error rate weighted by w and the ranging error weighted by 1-w.

[0071] Step S2 includes:

[0072] S21. Based on the fact that the root index value of the ZC sequence is less than the sequence length and coprime to the sequence length, search for the root index value;

[0073] S22, Pilot distribution indicates from N sym ·N sc N positions are selected from the given positions. pilot There are positions, and the number of possible choices is . Furthermore, its size increases exponentially with the increase of parameters, and a genetic algorithm is used for fast search.

[0074] Step S3 includes:

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

[0076] S32. Take the reciprocal of the optimization function to obtain the fitness function. Calculate the function value of the root index and pilot distribution coordinates for each ZC sequence, and save the maximum value and its corresponding root index and pilot distribution coordinates.

[0077] S33. The roulette wheel selection algorithm is used to select the root index value and pilot distribution coordinates of the ZC sequence, and N is regenerated. GA Root index values ​​of each ZC sequence and pilot distribution coordinates;

[0078] S34, according to probability P c Two new root index values ​​and pilot distribution coordinates are generated by exchanging the root index values ​​and pilot distribution coordinates of the ZC sequence. The new values ​​are selected and replaced by the original values, while the unexchanged parts are retained.

[0079] S35, according to probability P m The root index value and pilot distribution coordinates are numerically modified and replaced with the original values, while the unchanged parts are retained.

[0080] S36. Recalculate the function values ​​of the root index values ​​and pilot distribution coordinates of each ZC sequence. If the maximum value is greater than the original maximum value, replace the original values ​​with the root index values ​​and pilot distribution coordinates of the ZC sequence corresponding to the maximum value.

[0081] S37. Increment the iteration count by one. When the iteration count reaches the maximum iteration count, the algorithm ends and outputs the optimal value of the root index of the current ZC sequence and the optimal distribution of the pilot. Otherwise, return to S433.

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

[0083] In OFDM systems, communication and ranging are performed using an ideal autocorrelation sequence. The ideal autocorrelation sequence acts as a pilot for channel estimation. Autocorrelation estimation in the time and frequency domains is used for delay ranging because the ZC sequence is a constant-amplitude, zero-autocorrelation sequence with good autocorrelation in both the time and frequency domains. These two-step autocorrelation steps in the time and frequency domains can accurately measure the transmission delay and thus estimate the transmission distance. Furthermore, it improves signal compatibility: the ZC sequence, as the smallest resource unit superimposed on OFDM, does not interfere with each other, resulting in good signal compatibility.

[0084] Example 2

[0085] A low-Earth orbit (LEO) satellite communication ranging integrated transmission device includes: 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 LEO satellite communication ranging integrated transmission signal generation method described above is executed.

[0086] The relevant technical solutions are the same as those in the previous embodiments, and will not be repeated here.

[0087] Example 3

[0088] A method for analyzing integrated ranging and receiving signals in low-Earth orbit satellite communication includes:

[0089] The received signal from the transmitter is pre-compensated for Doppler frequency shift and sampled to obtain the discrete signal y. k ; by y k The data to be transmitted is obtained by parsing, and y k With the known pilot signal sampling sequence s k Perform autocorrelation in the time domain to obtain the integer delay τ1 in the total signal transmission delay; then process the sampled sequence s. k Shift p to get right and y k Perform Fast Fourier Transform (FFT) on each subcarrier to obtain frequency domain data S and Y; calculate the autocorrelation W of Z at the q-th subcarrier and the (q+Q)-th subcarrier to obtain the fractional delay τ2 in the total signal transmission delay, where Z is the autocorrelation expression 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 this with the speed of light to obtain the estimated distance between the satellite and the ground.

[0090] The received signal comes from the transmitted signal generated and transmitted by the transmitting end, and the transmitted signal is generated in the following way: a pilot signal is generated according to a preset ideal autocorrelation sequence, the pilot signal and constellation symbols are mapped together to OFDM resource units according to a preset distribution method to obtain an OFDM signal; the OFDM signal is modulated by OFDM to generate the transmitted signal.

[0091] The ZC sequence is the preferred and ideal autocorrelation sequence.

[0092] The preferred ideal autocorrelation sequence and distribution pattern can be obtained by optimizing the genetic algorithm to achieve optimal communication and ranging performance.

[0093] The relevant technical solutions are the same as those in the previous embodiments, and will not be repeated here.

[0094] Example 4

[0095] A low-Earth orbit (LEO) satellite communication ranging integrated receiving device includes: 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 LEO satellite communication ranging integrated receiving signal analysis method as described above is executed.

[0096] The relevant technical solutions are the same as those in the aforementioned embodiments, and will not be repeated here.

[0097] Example 5

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

[0099] The relevant technical solutions are the same as those in the aforementioned embodiments, and will not be repeated here.

[0100] Example 6

[0101] A computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, it controls the device on which the storage medium is located to perform the steps of the method described above or the steps of the method described above.

[0102] Specifically, the memory may include high-speed random access memory, as well as non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital cards (SD), flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0103] The relevant technical solutions are the same as those in the aforementioned embodiments, and will not be repeated here.

[0104] In summary, this invention discloses an integrated method and system for low-Earth orbit satellite communication and ranging, belonging to the field of satellite communication and ranging. Figure 5As shown, this method mainly includes the following steps: generating pilot signals based on ideal autocorrelation sequences, and then mapping them together with modulated constellation symbols to OFDM resource elements (REs); generating transmit signals, performing Doppler frequency shift pre-compensation on the received signals at the receiving end, sampling to obtain discrete signals and generating local sampling sequences; performing autocorrelation operations on the received discrete signals and local sequences in the time and frequency domains respectively to estimate the time delay and obtain the corresponding transmission distance. Furthermore, an optimization function for system communication and ranging performance is proposed, minimizing the communication bit error rate and ranging error based on a genetic algorithm to obtain the optimal ideal autocorrelation sequence and pilot distribution matrix. Using this method, the system fully utilizes time and frequency resources, enabling reliable communication while achieving ranging functionality, and allowing for a trade-off between communication and ranging performance, greatly promoting the development of integrated communication and positioning. It should be noted that... Figure 5 The dashed box in the middle represents the relevant processing steps for OFDM modulation.

[0105] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. A method for generating integrated ranging and transmission signals for low-Earth orbit satellite communication, characterized in that, include: A pilot signal is generated based on a preset ideal autocorrelation sequence. The pilot signal and constellation symbols are then mapped together onto OFDM resource cells according to a preset distribution method to obtain an OFDM signal. OFDM modulation is applied to the OFDM signal to generate the transmit signal; If there is a communication task, the constellation symbol is obtained by modulating the data to be transmitted; The transmitted signal is used by the receiving end to receive the received signal, and the received signal is subjected to Doppler frequency shift pre-compensation and sampled to obtain a discrete signal. ;Depend on The data to be transmitted is parsed and then... With known pilot signal sampling sequence Perform autocorrelation in the time domain to obtain the integer delay in the total signal propagation delay. ; Sample sequence shift get ,right and Perform Fast Fourier Transform to obtain frequency domain data. and ;calculate In the At the subcarrier position and the first Autocorrelation at each subcarrier The fractional delay in the total signal transmission delay is obtained. ,in, for and Autocorrelation expression in the frequency domain; integer time delay and decimal delay The sum gives the total signal transmission delay. By combining the speed of light, we can obtain an estimated distance between the star and the Earth; The ideal autocorrelation sequence is a ZC sequence; the ideal autocorrelation sequence and the distribution mode are jointly optimized at the receiving end through simulation based on a genetic algorithm to achieve optimal communication and ranging performance, specifically: Establish optimization function Optimize the ZC sequence root index values ​​and pilot distribution on OFDM resource cells to minimize the communication bit error rate and ranging error. The optimization objective function is: ,in, For communication bit error rate; The distance measurement error; for this model, the variable is the root index value of the ZC sequence. And pilot distribution, expressed as , Let the coordinates of the pilot on RE be , and the number of variables be . The constraints are , , , , ; The length of the ZC sequence; The number of OFDM subcarriers, The number is a signed number; the root index value and pilot distribution coordinates are constructed using binary encoding. A random number generator is used to generate the root index value and pilot distribution coordinates while satisfying the constraints, resulting in a binary encoded string. … ; initialization The root index value of the ZC sequence and the pilot distribution coordinates are selected. Their initial values ​​are generated by a random number generator and meet the constraints. Based on the initial values, the transmission signal is generated at the transmitting end. At the receiving end, with the objective function as the target, based on the fact that the root index value of the ZC sequence is less than the sequence length and coprime to the sequence length, the root index value is searched, and the pilot distribution represents the sequence from... Select from the positions There are positions, and the number of selections is . Furthermore, the size increases exponentially with the increase of parameters, and a genetic algorithm is used for fast search. The number of iterations is incremented by one, and the new ZC sequence and distribution corresponding to the search are sent to the transmitter. The transmitter regenerates the transmission signal. When the number of iterations reaches the maximum number of iterations, the optimal value of the root index of the current ZC sequence and the optimal distribution of the pilot are output. The receiver obtains the final data to be transmitted and the estimated distance between the satellite and the ground under the optimal value of the root index of the current ZC sequence and the optimal distribution of the pilot.

2. A low-orbit satellite communication ranging integrated transmitting device, characterized in that, include: The processor includes a memory storing processor-executable instructions and a data transceiver for data transmission and / or reception; wherein, when the instructions are executed by the processor, the low-orbit satellite communication ranging integrated transmission signal generation method as described in claim 1 is executed.

3. A method for analyzing integrated ranging and receiving signals in low-Earth orbit satellite communication, characterized in that, include: The received signal from the transmitter is pre-compensated for Doppler frequency shift and sampled to obtain a discrete signal. ;Depend on The data to be transmitted is parsed and then... With known pilot signal sampling sequence Perform autocorrelation in the time domain to obtain the integer delay in the total signal propagation delay. ; Sample sequence shift get ,right and Perform Fast Fourier Transform to obtain frequency domain data. and ;calculate In the At the subcarrier position and the first Autocorrelation at each subcarrier The fractional delay in the total signal transmission delay is obtained. ,in, for and Autocorrelation expression in the frequency domain; integer time delay and decimal delay The sum gives the total signal transmission delay. By combining the speed of light, we can obtain an estimated distance between the star and the Earth; The received signal originates from a transmitted signal generated and transmitted by the transmitting end, and the transmitted signal is generated in the following manner: a pilot signal is generated according to a preset ideal autocorrelation sequence; the pilot signal and constellation symbols are mapped together to OFDM resource cells according to a preset distribution method to obtain an OFDM signal; the OFDM signal is then OFDM modulated to generate the transmitted signal. The ideal autocorrelation sequence is a ZC sequence; the ideal autocorrelation sequence and the distribution mode are jointly optimized at the receiving end through simulation based on a genetic algorithm to achieve optimal communication and ranging performance, specifically: Establish optimization function Optimize the ZC sequence root index values ​​and pilot distribution on OFDM resource cells to minimize the communication bit error rate and ranging error. The optimization objective function is: ,in, For communication bit error rate; The distance measurement error; for this model, the variable is the root index value of the ZC sequence. And pilot distribution, expressed as , Let the coordinates of the pilot on RE be , and the number of variables be . The constraints are , , , , ; The length of the ZC sequence; The number of OFDM subcarriers, The number is a signed number; the root index value and pilot distribution coordinates are constructed using binary encoding. A random number generator is used to generate the root index value and pilot distribution coordinates while satisfying the constraints, resulting in a binary encoded string. … ; initialization The root index value of the ZC sequence and the pilot distribution coordinates are selected. Their initial values ​​are generated by a random number generator and meet the constraints. Based on the initial values, the transmission signal is generated at the transmitting end. At the receiving end, with the objective function as the target, based on the fact that the root index value of the ZC sequence is less than the sequence length and coprime to the sequence length, the root index value is searched, and the pilot distribution represents the sequence from... Select from the positions There are positions, and the number of selections is . Furthermore, the size increases exponentially with the increase of parameters, and a genetic algorithm is used for fast search. The number of iterations is incremented by one, and the new ZC sequence and distribution corresponding to the search are sent to the transmitter. The transmitter regenerates the transmission signal. When the number of iterations reaches the maximum number of iterations, the optimal value of the root index of the current ZC sequence and the optimal distribution of the pilot are output. The receiver obtains the final data to be transmitted and the estimated distance between the satellite and the ground under the optimal value of the root index of the current ZC sequence and the optimal distribution of the pilot.

4. A low-orbit satellite communication ranging integrated receiving device, characterized in that, include: The processor includes a memory storing processor-executable instructions and a data transceiver for data transmission and / or reception; wherein, when the instructions are executed by the processor, the low-orbit satellite communication ranging integrated receiving signal analysis method as described in claim 3 is executed.

5. A low-orbit satellite communication ranging integrated system, characterized in that, It includes the low-orbit satellite communication ranging integrated transmitting device as described in claim 2 and the low-orbit satellite communication ranging integrated receiving device as described in claim 4.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein when the computer program is run by a processor, it controls the device on which the storage medium is located to perform the steps of the method as claimed in claim 1 or the steps of the method as claimed in claim 3.

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