A Starlink signal simulation method for interference testing

Abstract

The present invention provides a Starlink signal simulation method for interference testing, including: constructing a model of the Starlink communication system based on the communication link of the Starlink system; collecting and integrating the modulation methods and modulation parameters involved in the modulation process of the Starlink system signal; using the modulation information to generate a simulated Starlink modulation signal according to the actual Starlink signal parameters; designing a signal transmission and reception model and inputting the simulated Starlink modulation signal, using the autocorrelation method to perform carrier frequency judgment to obtain a modified signal transmission and reception model; carrying information data in the simulated Starlink modulation signal, so that it is transmitted through the modified signal transmission and reception model for simulation, and obtaining a simulated Starlink signal. The present invention breaks through the difficult problems of uncertain frequency points and unknown modulation parameters in the simulation of Starlink high-frequency band signals, and constructs a complete set of Starlink downlink communication link models, providing a theoretical basis and practical guidance for the effective interference of Starlink signals in the future.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite navigation interference testing, and in particular relates to a Starlink signal simulation method for interference testing. Background Art

[0002] With the rapid development of drone technology, lower manufacturing costs, and greater ease of mission execution, drones are increasingly being used in various fields. For safety reasons, drone jamming is becoming increasingly important. One effective method is to deceiving and jam a drone's navigation system, preventing it from reaching its intended location. Research and development of highly accurate jamming devices can disrupt a drone's satellite navigation system, inertial navigation system, and other systems, preventing it from accurately positioning itself or misleading it to an incorrect location, effectively countering drone attacks.

[0003] Compared to inertial navigation systems, jamming satellite navigation systems is more effective. Most current drones use the Global Navigation Satellite System (GNSS), and numerous methods exist for deceiving and jamming drones using GNSS for navigation. With the development of satellite communications, low-orbit satellites (LEO) are gradually being put into use. Compared to GNSS, they offer unique advantages in navigation and positioning. Their low orbits, altitudes ranging from approximately 500-1200km, higher landing power, and low weight, along with lower satellite manufacturing and launch costs, are a growing trend for drones to use LEO for positioning, making jamming LEO signals particularly important.

[0004] Among the numerous low-orbit satellite systems, SpaceX's Starlink constellation is currently the most mature, with over 3,000 satellites in orbit. Some researchers have begun using the Doppler shift information of Starlink's downlink signals for positioning demonstrations, making interference with Starlink's satellite internet signals particularly important.

[0005] However, compared with the low-frequency signals and known parameters of traditional GNSS systems, Starlink signals are in the high-frequency band and their technical details, such as frequency and modulation methods, are confidential. Therefore, to date, there is no effective way to interfere with Starlink signals. Summary of the Invention

[0006] The present invention aims to address the current lack of an effective method for jamming Starlink signals, as the signals operate in high-frequency bands and their technical details, such as frequency and modulation, are confidential. Instead, it provides a Starlink signal simulation method for jamming testing. This method accurately simulates Starlink signal behavior from system signal generation to final demodulation, providing a powerful tool for understanding Starlink signal characteristics and transmission patterns. More importantly, it lays a solid foundation for subsequent research on how to effectively deceptively jam Starlink signals at different operating frequencies, thereby potentially promoting the development and optimization of related security protection technologies and strategies.

[0007] To achieve the above objectives, the technical solutions provided by the present invention are:

[0008] A Starlink signal simulation method for interference testing includes the following steps:

[0009] Step 1: Based on the communication link of the Starlink system, a model of the Starlink communication system is constructed, which includes a signal source generation module, an encoding module, a modulation module, an up-conversion module, a channel transmission module, a down-conversion module, a demodulation module, and a decoding module.

[0010] Step 2: For the modulation module in the Starlink communication system model constructed in Step 1, collect and integrate the modulation methods and modulation parameters involved in the modulation process of the Starlink system signal;

[0011] Step 3: Using the modulation information obtained in step 2, a simulated Starlink modulation signal is generated according to the actual Starlink signal parameters;

[0012] Step 4: For the down-conversion module in the Starlink communication system model constructed in step 1, establish a signal transmission and reception model, including:

[0013] Step 4.1: Based on the Starlink communication system model constructed in step 1, design the signal transmission and reception model;

[0014] Step 4.2: Input the simulated Starlink modulated signal generated in Step 3 into the signal transmission and reception model designed in Step 4.1. Up-convert the input signal using a random frequency point. After transmission through the channel, use the autocorrelation method to determine the carrier frequency of the signal to determine the operating frequency point of the signal. Then, down-convert the signal according to the determined frequency point to obtain the modified signal transmission and reception model.

[0015] Step 5: Load the information data into the simulated Starlink modulated signal generated in step 3, and then simulate the signal transmission through the modified signal transmission and reception model obtained in step 4.2 to obtain the required simulated Starlink signal.

[0016] Furthermore, the Starlink signal simulation method also includes step 6 of performing simulation verification, which specifically includes the following sub-steps:

[0017] Step 6.1, subjecting the simulated Starlink signal obtained in step 5 to a signal reception simulation using the modified signal transmission and reception model obtained in step 4.2 to obtain a simulated Starlink down-converted signal;

[0018] Step 6.2: Demodulate and decode the obtained simulated Starlink down-converted signal and compare it with the original information data to verify the reliability and accuracy of the Starlink communication system model.

[0019] Furthermore, the signal generation module in the Starlink communication system model uses a random 0-1 sequence to generate the signal source.

[0020] Furthermore, the encoding method used by the encoding module in the Starlink communication system model is convolutional code and re-interleaving.

[0021] Furthermore, the modulation module in the Starlink communication system model adopts high-order modulation technology and OFDM (Orthogonal Frequency Division Multiplexing) modulation technology.

[0022] Furthermore, the demodulation module in the Starlink communication system model uses 16QAM soft demodulation output based on maximum likelihood ratio.

[0023] The advantages of the present invention are:

[0024] 1. The Starlink signal simulation method for interference testing of the present invention first constructs a model of the Starlink communication system. It also integrates the modulation mechanism and key parameters of the Starlink signal and establishes a signal transmission and reception model for the modulation module and downconversion module in the model. Then, the simulated Starlink modulated signal is transmitted through the signal transmission and reception model, and the carrier frequency of the signal is determined by the autocorrelation method to determine the operating frequency of the signal. The simulated Starlink modulated signal carrying information data can be transmitted and simulated through the modified signal transmission and reception model to obtain a simulated Starlink signal. Therefore, the present invention fully utilizes a large amount of collected and analyzed data resources on the actual operation of the Starlink system signal parameters and communication mechanism, breaking through the previous problems of uncertain frequency and unknown modulation parameters in the simulation of Starlink high-frequency band signals, and constructing a complete Starlink downlink communication link model. This provides a theoretical basis and practical guidance for the future implementation of effective interference and deception methods for Starlink signals. It also further enhances the countermeasures and control capabilities of unmanned aerial vehicle systems that rely on Starlink signals for navigation and positioning, ensuring effective management and security protection when necessary.

[0025] 2. The present invention also includes a simulation verification step, which can test the reliability and accuracy of the constructed Starlink communication system model. In this way, the performance of the Starlink communication system model can be quantitatively analyzed and its effective operation can be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The features and advantages of the present invention will become more readily understood through the following description with reference to the accompanying drawings, in which:

[0027] Figure 1 It is a flow chart of the Starlink signal simulation method for interference testing of the present invention;

[0028] Figure 2 is a model diagram of the Starlink communication system constructed in the method of the present invention;

[0029] Figure 3 It is a calculation flow chart of the signal transmission and reception model implemented at the transmitting end in the method of the present invention;

[0030] Figure 4 A flow chart showing carrier frequency determination at the receiving end by the signal transmission and reception model in the method of the present invention;

[0031] Figure 5 This is a diagram of the Starlink simulation software interface used in the examples of the method of the present invention;

[0032] Figure 6 The following is a diagram of the Starlink signal baseband spectrum simulated in an example of the method of the present invention;

[0033] Figure 7 This is a time domain diagram of the Starlink signal transmission signal simulated in an example of the method of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings by means of exemplary embodiments of the present invention. It should be noted that the following detailed description of the present invention is only for the purpose of illustration and is not intended to limit the present invention.

[0035] The present invention provides a Starlink signal simulation method for interference testing, which aims to overcome the difficulties of frequency uncertainty and unknown modulation methods and parameters in Starlink high-frequency band signal simulation, and build a complete Starlink downlink communication link model.

[0036] First, the overall reference Figure 1 As an exemplary embodiment of the present invention, a Starlink signal simulation method for interference testing includes:

[0037] Step S1: construct a model of the Starlink communication system based on the communication link of the Starlink system. The constructed Starlink communication system model is as follows: Figure 2As shown, it includes a signal source generation module, an encoding module, a modulation module, an up-conversion module, a channel transmission module, a down-conversion module, a demodulation module and a decoding module in sequence;

[0038] Step S2: For the modulation module in the Starlink communication system model constructed in step S1, the modulation modes and modulation parameters involved in the modulation process of the Starlink system signal are collected and integrated;

[0039] Step S3, using the modulation information obtained in step S2, generating a simulated Starlink modulation signal according to the actual Starlink signal parameters;

[0040] Step S4: For the down-conversion module in the Starlink communication system model constructed in step S1, a signal transmission and reception model is established, including:

[0041] Step S4.1: Design a signal transmission and reception model based on the Starlink communication system model constructed in step S1;

[0042] Step S4.2: Input the simulated Starlink modulated signal generated in step S3 into the signal transmission and reception model designed in step S4.1. Up-convert the input signal using a random frequency point. After transmission through the channel, use the autocorrelation method to determine the carrier frequency of the signal to determine the operating frequency point of the signal. Then, down-convert the signal according to the determined frequency point to obtain a modified signal transmission and reception model.

[0043] Step S5: The information data is carried in the simulated Starlink modulated signal generated in step S3, and then the signal transmission simulation is performed through the modified signal transmission and reception model obtained in step S4.2 to obtain the required simulated Starlink signal.

[0044] In step S1, based on existing literature and technical data, the communication link of the Starlink communication system is studied and investigated. After sufficient analysis, a downlink communication link diagram of the Starlink communication system can be constructed as shown in the following figure: Figure 2 shown.

[0045] Reference Figure 2 The signal generation module is the source of the signal. The Starlink signal generation principle is unknown, so a random 0-1 sequence can be used to generate the signal. In other words, a random 0-1 sequence is used for subsequent steps until the 0-1 sequence is demodulated. The demodulated sequence is then compared with the generated sequence to calculate the system's bit error rate.

[0046] Regarding the encoding module, the Starlink constellation's encoding method is also not publicly documented, so any possible encoding method must be used in the encoding part. When designing this simulation system, the encoding method used is convolutional coding and re-interleaving.

[0047] A convolutional code is a linear error-correcting code commonly used in digital communications to encode and decode data and improve data transmission reliability. It is a sequence encoding technique that generates output codewords based on input data and internal states. During the encoding process, each output codeword is a linear combination of a portion of the input sequence and the internal state. In practice, its implementation is based on a finite state machine, typically using one or more hysteresis registers (delay lines) and logic gates. Each hysteresis register stores a portion of the input sequence, and the logic gates generate the output codeword based on the hysteresis register state and certain bits of the input sequence. By continuously shifting the contents of the hysteresis registers and updating the inputs of the logic gates, convolutional codes can continuously generate codewords.

[0048] Reinterleaving is a technique used to mitigate the impact of burst errors during channel transmission. It rearranges the elements in a data sequence, distributing consecutive errors into dispersed ones, thereby improving error performance. Reinterleaving is typically used after convolutional or turbo codes to increase the error tolerance of channel coding. Reinterleaving can be implemented using various methods, including block interleaving and symbol interleaving. Block interleaving divides the input data into blocks and rearranges the data within the blocks according to a specific rule, while symbol interleaving rearranges the data symbols within each block according to a specific rule. Reinterleaving can be performed at both the transmitter and receiver to ensure that errors in the transmitted data channel minimize the impact on the final decoding result.

[0049] In step S2, for the modulation module, according to the analysis of some researchers, the Starlink signal may adopt a high peak-to-average ratio modulation method. Some people believe that Starlink may use high-order modulation technology, such as 16QAM modulation, and may be combined with OFDM modulation. In 16QAM modulation, each symbol can represent 16 different states, so 4 bits of information can be transmitted in one symbol period. The real and imaginary parts of the signal use 4 discrete amplitude levels to represent different information, and then the modulated signals of these two parts are combined into a constellation diagram with 16 different amplitudes and phases. The present invention adopts high-order modulation technology and OFDM modulation technology to improve the efficiency and anti-interference ability of signal transmission, which is suitable for signal transmission of the Starlink system. Through this modulation method, the Starlink system can achieve high-speed data transmission and the ability to resist noise interference.

[0050] OFDM is a multicarrier modulation technology used to simultaneously transmit multiple subcarriers in digital communication systems. It divides a high-speed data stream into multiple lower-speed substreams, mapping each substream to a different orthogonal subcarrier for transmission. In OFDM modulation, the data stream first undergoes a series of transformations, such as the discrete Fourier transform (DFT), to convert the time-domain signal into a frequency-domain signal. The frequency-domain signal is then mapped onto different orthogonal subcarriers. These subcarriers are orthogonal, meaning their frequency-domain waveforms are orthogonal across the entire frequency spectrum. This orthogonality eliminates interference between subcarriers, enabling OFDM transmission over wideband channels.

[0051] After collecting and studying existing academic literature and technical documents, the OFDM parameters used by the Starlink signal in this invention are shown in Table 1.

[0052] Table 1 Starlink signal OFDM parameters

[0053]

[0054] In step S3, a modulated Starlink signal that conforms to reality can be generated according to the modulation mode of the Starlink signal determined above and the specific signal parameters in the modulation mode, based on the actual Starlink signal parameters.

[0055] The signal transmission and reception model established in step S4 is designed to accurately decode the analog signal and has the ability to parse the analog data to determine the operating frequency used, ensuring that the output results accurately reflect the characteristics of the actual Starlink signal, as follows:

[0056] Up-conversion: Up-conversion is to increase the signal frequency to the carrier frequency to facilitate signal transmission. The process at the transmitter is as follows Figure 3 As shown in the figure, after OFDM modulation, the signal is a complex baseband signal. In practical applications, real signals are transmitted, so it is necessary to convert the complex signal into a real signal. Assume that the modulated OFDM signal is as follows.

[0057] y=a+bj (1)

[0058] Where y is the OFDM modulated signal, a is the real part of the signal, b is the imaginary part of the signal, and j is the imaginary unit of the complex number. Up-conversion is an operation that needs to convert the signal into a real signal, so it needs to be multiplied by e. j2πf , where the frequency f can be one of the eight Starlink frequencies. The result after multiplying the complex signal and the complex carrier is as follows:

[0059] y=(acos2πf-bsin2πf)+j(asin2πf+bcos2πf) (2)

[0060] When transmitting, the real part is taken, that is, the transmitted signal is expressed as follows:

[0061] y=acos2πf-bsin2πf (3)

[0062] Carrier frequency determination: The flow chart for determining the carrier frequency is as follows: Figure 4 As shown in the figure, down-conversion converts the received signal back into a baseband signal. As mentioned above, the carrier frequency may be one of eight carrier frequencies, but the specific carrier frequency is unknown to the receiver. Therefore, the receiver needs to determine the carrier frequency to determine the transmitted carrier frequency.

[0063] When receiving a signal, regardless of the carrier frequency, it is necessary to perform a signal down-conversion operation. First, assume that the received signal is as shown in the above formula. When demodulating, it is necessary to demodulate a and b in the formula. Here, the demodulation of a is shown as follows:

[0064]

[0065] The above formula can be used to obtain the desired real part of the signal through a low-pass filter. Similarly, similar operations can also obtain the imaginary part of the signal.

[0066] When a signal is received, the above equation is applied to each carrier frequency, resulting in eight distinct signal values. These values ​​are then autocorrelated, and the signal with the largest autocorrelation value is taken to determine which signal is the real one and which uses the incorrect carrier frequency. This process helps ensure that valid information is correctly identified and extracted.

[0067] In step S5, information data can be randomly generated and carried using the constructed Starlink signal modulation technology. Then, the signal transmission process is simulated through the modified transmission and reception model to obtain the required simulated Starlink signal, that is, the simulated Starlink up-conversion signal.

[0068] In an exemplary embodiment of the present invention, the Starlink signal simulation method for interference testing further includes a step S6 of performing simulation verification, which specifically includes the following sub-steps:

[0069] Step S6.1, subjecting the simulated Starlink signal obtained in step S5 to a signal reception simulation using the modified signal transmission and reception model obtained in step S4.2 to obtain a simulated Starlink down-converted signal;

[0070] Step S6.2: Demodulate and decode the obtained simulated Starlink down-converted signal and compare it with the original information data to verify the reliability and accuracy of the Starlink communication system model.

[0071] Through the simulation process of steps S5 and S6, a high-fidelity simulation of the Starlink signal can be achieved from the signal modulation stage to the demodulation stage, and the reliability and accuracy of the constructed Starlink communication system model can be tested. In this way, the performance of the Starlink communication system model can be quantitatively analyzed and its effective operation can be ensured.

[0072] When demodulating, 16QAM soft demodulation output based on maximum likelihood ratio can be used. Log-Likelihood Ratio (LLR) is a commonly used soft demodulation method for QAM. Assuming the received signal is r, the formula for the i-th bit after demodulation is as follows:

[0073]

[0074] Where L represents the ratio of conditional probabilities, P represents the received signal r and the sent signal b i The conditional probability of .

[0075] This is a ratio of conditional probabilities, that is, when the received signal is r, it can be inferred based on the information of the received signal whether the probability of the transmitted signal being 1 or 0 is greater.

[0076] To simplify the formula, the demodulation is derived using a channel with Gaussian noise added.

[0077] The signal plus noise is as follows:

[0078] r(t)=s(t)+n(t) (6)

[0079] Where r(t) is the received signal, s(t) is the transmitted signal, and n(t) is Gaussian random noise. The conditional probability of the received signal is as follows:

[0080]

[0081] Where e represents a natural constant and σ represents the standard deviation of Gaussian random noise.

[0082] The Bayesian formula is as follows:

[0083]

[0084] Substituting the above formula into the original probability ratio formula, we can get the calculation formula of LLR:

[0085]

[0086] When b0 is 1, the constellation corresponding to the received data contains only 1 and -1. Then, according to formula (8), the conditional probability of the received signal when b0 = 1 can be expressed as:

[0087]

[0088] When b0 is 0, the constellation corresponding to the received data only contains 3 and -3. Then, according to formula (8), the conditional probability of the received signal when b0 = 0 can be expressed as:

[0089]

[0090] When receiving the imaginary part of the data r im In different ranges, there are obvious differences between the various index parts, and segmented analysis can be carried out.

[0091] The final analysis results are as follows:

[0092]

[0093] As described above, the present invention makes full use of a large amount of data resources collected and analyzed about the signal parameters and communication mechanisms of the actual operation of the Starlink system, breaking through the previous problems of uncertain frequency points and unknown modulation parameters in the simulation of Starlink high-frequency band signals, and constructing a complete Starlink downlink communication link model, providing a theoretical basis and practical guidance for the effective interference and deception of Starlink signals in the future, and further enhancing the countermeasures and control capabilities of drone systems that rely on Starlink signals for navigation and positioning, ensuring their effective management and security protection when necessary.

[0094] Next, the Starlink signal simulation method for interference testing provided by the present invention is further explained with reference to examples.

[0095] In this example, a random 0-1 information sequence is used as input, and Matlab software is used to simulate the system and finally form the Matlab simulation software. The simulation software is shown in the figure Figure 5 As shown, it includes three parts. In the signal parameter setting area, the digital sampling rate means an integer multiple of the baseband system bandwidth, and the default is 4; there are a total of 8 carrier frequency points to choose from; the cyclic prefix length refers to the cyclic prefix length of OFDM, which is generally 0.15-0.25 times the OFDM symbol. The simulation software provides 0.15, 0.2 and 0.25 times for selection. In the channel parameter setting area, the signal-to-noise ratio and Doppler shift of the signal can be set through the channel. The default settings are 20dB and 0. After the above parameters are set, click the Start Simulation button and wait for the simulation to complete. After the simulation is completed, the demodulated carrier frequency and bit error rate will be displayed in the digital box at the bottom, and two frames will pop up, showing the spectrum diagram of the baseband signal and the time domain diagram of the transmitted signal. The baseband spectrum diagram of the simulated Starlink signal is shown below. Figure 5 As shown, the time domain diagram is Figure 6shown.

[0096] This example illustrates that the Starlink signal simulation method provided by the present invention is effective.

[0097] The features mentioned and / or illustrated in the above description of the exemplary embodiments of the present invention may be incorporated into one or more other embodiments in the same or similar manner, combined with the features in other embodiments, or substituted for the corresponding features in other embodiments. The technical solutions obtained by such combination or substitution shall also be deemed to be included in the scope of protection of the present invention.

Claims

1. A Starlink signal simulation method for interference testing, characterized in that: The following steps are involved: Step 1: Based on the communication link of the Starlink system, a model of the Starlink communication system is constructed, which includes a signal source generation module, an encoding module, a modulation module, an up-conversion module, a channel transmission module, a down-conversion module, a demodulation module, and a decoding module. Step 2: For the modulation module in the Starlink communication system model constructed in Step 1, collect and integrate the modulation methods and specific signal parameters involved in the modulation process of the Starlink system signal; Step 3: Generate a simulated Starlink modulation signal based on the actual Starlink signal parameters using the modulation mode and signal specific parameters in the modulation mode obtained in step 2; Step 4: For the down-conversion module in the Starlink communication system model constructed in step 1, establish a signal transmission and reception model, including: Step 4.1: Based on the Starlink communication system model constructed in step 1, design the signal transmission and reception model; Step 4.2: Input the simulated Starlink modulated signal generated in Step 3 into the signal transmission and reception model designed in Step 4.

1. Up-convert the input signal using a random frequency point. After transmission through the channel, use the autocorrelation method to determine the carrier frequency of the signal to determine the operating frequency point of the signal. Then, down-convert the signal according to the determined frequency point to obtain the modified signal transmission and reception model. Step 5: Load the information data into the simulated Starlink modulated signal generated in step 3, and then simulate the signal transmission through the modified signal transmission and reception model obtained in step 4.2 to obtain the required simulated Starlink signal.

2. The Starlink signal simulation method for interference testing according to claim 1, characterized in that: The step 6 of performing simulation verification is also included, which specifically includes the following sub-steps: Step 6.1, subjecting the simulated Starlink signal obtained in step 5 to a signal reception simulation using the modified signal transmission and reception model obtained in step 4.2 to obtain a simulated Starlink down-converted signal; Step 6.2: Demodulate and decode the obtained simulated Starlink down-converted signal and compare it with the original information data to verify the reliability and accuracy of the Starlink communication system model.

3. The Starlink signal simulation method for interference testing according to claim 1 or 2, characterized in that: The signal generation module in the Starlink communication system model uses a random 0-1 sequence to generate the signal source.

4. The Starlink signal simulation method for interference testing according to claim 1 or 2, characterized in that: The encoding method used by the encoding module in the Starlink communication system model is convolutional code and re-interleaving.

5. The Starlink signal simulation method for interference testing according to claim 1 or 2, characterized in that: The modulation module in the Starlink communication system model adopts high-order modulation technology and OFDM modulation technology.

6. The Starlink signal simulation method for interference testing according to claim 5, characterized in that: The demodulation module in the Starlink communication system model uses 16QAM soft demodulation output based on maximum likelihood ratio.

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