Low earth orbit constellation navigation and fusion signal generation and reception method

Abstract

The application discloses a low-orbit constellation navigation and communication signal generation and receiving method, and belongs to the technical field of satellite navigation and communication. In the navigation and communication signal generation method, the real-time signal-to-noise ratio of an inter-satellite channel is estimated according to the inter-satellite distance, the power distribution ratio of a communication component and a navigation component is determined according to the real-time signal-to-noise ratio, and the fusion of the communication signal and the navigation signal is realized by adopting a phase modulation mode; in the signal receiving method, the demodulation and separation of the communication component and the navigation component are completed by adopting a directional separation mode. According to the application, the power distribution ratio of the communication component and the navigation component is adaptively distributed according to the inter-satellite distance, the positioning precision of the satellite navigation signal is improved under the premise of meeting the inter-satellite communication error rate requirement, and the autonomous navigation capability of the low-orbit navigation constellation is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of satellite navigation and communication technology, specifically relating to a method for generating and receiving low-Earth orbit constellation communication and navigation fusion signals. Background Technology

[0002] Currently, low-Earth orbit (LEO) constellations typically employ two types of channels: a low-rate omnidirectional telemetry and control (TT&C) channel and a high-rate service data channel, used for navigation and positioning and data transmission respectively. Their core function is to achieve navigation and communication. Navigation and communication signals are transmitted independently via two different frequency points, requiring not only significant bandwidth but also two sets of transmitting and receiving equipment, resulting in high development costs.

[0003] The applicant argues that integrating navigation and communication functions can simplify onboard equipment, reduce power consumption, conserve frequency resources, improve the electromagnetic compatibility of hardware, and integrate ground station resources, thereby reducing the complexity of the management system. Furthermore, using communication links to transmit high-precision satellite time and position information can also calibrate the satellite's own clock, construct a relative position relationship network for the low-Earth orbit constellation, and enhance the autonomous navigation capabilities of the low-Earth orbit constellation.

[0004] However, in the process of realizing communication and navigation integration, how to allocate on-board power resources and improve navigation performance while ensuring the reliability of information transmission remains a problem that researchers in this field urgently need to solve. Summary of the Invention

[0005] In view of the above problems, this invention proposes a method for generating and receiving fused communication and navigation signals for low-Earth orbit constellations. This invention employs phase modulation to fuse communication and navigation signals, and allocates the power ratio of the communication and navigation components according to the inter-satellite link channel state, thereby improving system navigation performance while ensuring communication performance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for generating low-Earth orbit constellation communication and navigation fusion signals, applied to satellite launch, includes the following steps:

[0008] Step 1: Calculate the distance between the launching satellite and the receiving satellite based on the ephemeris information stored in the launching satellite and the position information of the receiving satellite;

[0009] Step 2: Based on the distance between the two satellites and the gain of the onboard antenna, estimate the real-time signal-to-noise ratio of the inter-satellite channel as follows:

[0010]

[0011] Among them, E b Let N0 be the power spectral density of the transmitted signal bit energy, and P be the power spectral density of the noise. tG represents the total power of the transmitter. t For the transmit antenna gain, G r For the receiving antenna gain, R b L is the bit rate of the transmitted signal. fs (dB)=10lg(4πdf / c) 2 For free space transmission loss, d is the distance between the two satellites, f is the carrier frequency, c is the speed of light, and L0 represents the remaining losses including Doppler frequency shift, antenna pointing error, and polarization loss.

[0012] Step 3: Plot the bit error rate curves of the communication-navigation fusion signal under different signal weighting factors using historical satellite measurement data;

[0013] Step 4: Determine the target communication bit error rate required for the service, and divide the signal-to-noise ratio switching interval based on the intersection point of the bit error rate curves of different signal weighting factors and the target bit error rate curve;

[0014] Step 5: Within each signal-to-noise ratio switching interval, determine all signal weighting factors that can meet the target bit error rate requirement, and select the maximum value among them as the selected signal weighting factor;

[0015] Step 6: The communication information to be transmitted is processed by LDPC encoding, level conversion, Gaussian filter, and integrator to generate the phase of the communication component;

[0016] Step 7: After the navigation information to be transmitted is processed by level conversion and shaping filter, it is multiplied by the selected signal weighting factor to obtain the phase of the navigation component;

[0017] Step 8: Add the phase of the communication component to the phase of the navigation component to obtain the communication-navigation fusion phase. After phase modulation, generate the communication-navigation fusion signal based on GMSK+PN.

[0018]

[0019] Among them, P t ω is the total transmitter power, and ω is the carrier frequency. The phase of the communication component, The phase of the navigation component.

[0020] A method for receiving fused communication and navigation signals from a low-Earth orbit constellation, applied to receiving satellites, is used to receive and separate the fused communication and navigation signals generated by the above method, and includes the following steps:

[0021] Step 1: Perform GMSK demodulation on the received GMSK+PN conduction fusion signal to obtain the phase of the communication component;

[0022] Step 2: Perform GMSK remodulation on the phase of the obtained communication component to obtain the phase of the regenerated communication signal;

[0023] Step 3: After conjugating the phase of the regenerated communication signal, perform a complex domain correlation with the received GMSK+PN conduction fusion signal to obtain:

[0024]

[0025] in, For the low-pass equivalent of the received signal in the complex domain, To regenerate the phase of the communication signal, The phase of the communication component, Let n(t) be the phase of the navigation component, and n(t) be the noise during transmission.

[0026] Step 4: Take the imaginary part of the complex correlation result to obtain the navigation component separated from the GMSK+PN conduction fusion signal:

[0027]

[0028] in, To separate the noise carried in the navigation components;

[0029] Step 5: Capture and track the separated navigation components to achieve synchronous demodulation of the navigation signal;

[0030] Step 6: Calculate the position information of the launched satellite based on the synchronization demodulation results;

[0031] Step 7: Update the ephemeris information of the receiving satellite and the location information of the launching satellite.

[0032] Compared with existing low-Earth orbit constellation communication and navigation link technologies, this invention has the following advantages:

[0033] (1) This invention is applicable to inter-satellite links of low-Earth orbit satellites and can enhance the autonomous navigation capability of low-Earth orbit navigation constellations;

[0034] (2) The present invention adopts a communication and navigation fusion method based on GMSK+PN, which can improve the system bandwidth utilization and realize the synchronous transmission of high code rate communication data and high precision navigation information;

[0035] (3) The present invention adopts a power allocation method based on signal-to-noise ratio, which can adaptively allocate the power of communication components and navigation components according to the inter-satellite distance, thereby improving the utilization rate of satellite resources;

[0036] (4) The present invention adopts a directional separation method, which can separate the communication component and the navigation component in the communication-navigation fusion signal, reduce mutual interference between signal components, and improve the demodulation performance of the system.

[0037] In summary, this invention adaptively allocates the power ratio of communication and navigation components based on inter-satellite distance, which can improve the positioning accuracy of satellite navigation signals and enhance the autonomous navigation capability of low-Earth orbit navigation constellations while meeting the requirements of inter-satellite communication bit error rate. Attached Figure Description

[0038] Figure 1 This is a schematic diagram illustrating the principle of signal generation based on GMSK+PN in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram illustrating the principle of directional separation based on GMSK+PN in an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of signal transmission between the launching satellite and the receiving satellite in an embodiment of the present invention. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] A method for generating low-Earth orbit constellation communication and navigation fusion signals, applied to satellite launch, such as... Figure 1 As shown, it includes the following steps:

[0043] Step 1: Calculate the distance between the launching satellite and the receiving satellite based on the ephemeris information stored in the launching satellite and the position information of the receiving satellite;

[0044] Step 2: Based on the distance between the two satellites and the gain of the onboard antenna, estimate the real-time signal-to-noise ratio of the inter-satellite channel as follows:

[0045]

[0046] Among them, E b Let N0 be the power spectral density of the transmitted signal bit energy, and P be the power spectral density of the noise. t G represents the total power of the transmitter. t For the transmit antenna gain, G r For the receiving antenna gain, R b L is the bit rate of the transmitted signal. fs (dB)=10lg(4πdf / c) 2 For free space transmission loss, d is the distance between the two satellites, f is the carrier frequency, c is the speed of light, and L0 represents the remaining losses including Doppler frequency shift, antenna pointing error, and polarization loss.

[0047] Step 3: Plot the bit error rate curves of the communication-navigation fusion signal under different signal weighting factors using historical satellite measurement data;

[0048] Step 4: Determine the target communication bit error rate required for the service, and divide the signal-to-noise ratio switching interval based on the intersection point of the bit error rate curves of different signal weighting factors and the target bit error rate curve;

[0049] Step 5: Within each signal-to-noise ratio switching interval, determine all signal weighting factors that can meet the target bit error rate requirement, and select the maximum value among them as the selected signal weighting factor;

[0050] Step 6: The communication information to be transmitted is processed by LDPC encoding, level conversion, Gaussian filter, and integrator to generate the phase of the communication component;

[0051] Step 7: After the navigation information to be transmitted is processed by level conversion and shaping filter, it is multiplied by the selected signal weighting factor to obtain the phase of the navigation component;

[0052] Step 8: Add the phase of the communication component to the phase of the navigation component to obtain the communication-navigation fusion phase. After phase modulation, generate the communication-navigation fusion signal based on GMSK+PN.

[0053]

[0054] Among them, P t ω is the total transmitter power, and ω is the carrier frequency. The phase of the communication component, The phase of the navigation component.

[0055] A method for receiving fused communication and navigation signals from a low-Earth orbit constellation is proposed, applied to receiving satellites, for receiving and separating the fused communication and navigation signals generated by the aforementioned method, such as... Figure 2 As shown, it includes the following steps:

[0056] Step 1: Perform GMSK demodulation on the received GMSK+PN conduction fusion signal to obtain the phase of the communication component;

[0057] Step 2: Perform GMSK remodulation on the phase of the obtained communication component to obtain the phase of the regenerated communication signal;

[0058] Step 3: After conjugating the phase of the regenerated communication signal, perform a complex domain correlation with the received GMSK+PN conduction fusion signal to obtain:

[0059]

[0060] in, For the low-pass equivalent of the received signal in the complex domain, To regenerate the phase of the communication signal, The phase of the communication component, Let n(t) be the phase of the navigation component, and n(t) be the noise during transmission.

[0061] Step 4: Take the imaginary part of the complex correlation result to obtain the navigation component separated from the GMSK+PN conduction fusion signal:

[0062]

[0063] in, To separate the noise carried in the navigation components;

[0064] Step 5: Capture and track the separated navigation components to achieve synchronous demodulation of the navigation signal;

[0065] Step 6: Calculate the position information of the launched satellite based on the synchronization demodulation results;

[0066] Step 7: Update the ephemeris information of the receiving satellite and the location information of the launching satellite.

[0067] In the method for receiving communication and navigation fusion signals in low-Earth orbit constellations, the navigation signal component accounts for a relatively small proportion of the fused signal and can be regarded as a small phase shift of the communication component. The navigation signal component is treated as "noise" in the transmission process, and the received communication and navigation fusion signal is directly demodulated by GMSK to obtain the restored communication signal. The restored communication signal is then remodulated by GMSK to obtain the phase of the regenerated communication signal. The phase of the regenerated communication signal is then complex correlated with the received signal to complete the separation of the communication and navigation fusion signal, obtain the restored navigation signal, and send it to the navigation signal synchronization module to calculate the satellite position and inter-satellite distance information.

[0068] In the method for generating communication and navigation fusion signals for low-Earth orbit constellations, power allocation between communication and navigation components is achieved through a power allocation method based on real-time signal-to-noise ratio, such as... Figure 3 As shown.

[0069] The receiving satellite forwards the calculated satellite position and inter-satellite distance information to the launching satellite. The launching satellite then estimates the real-time signal-to-noise ratio based on the inter-satellite distance and the gain of the onboard antenna:

[0070]

[0071] Among them, E b Let N0 be the power spectral density of the transmitted signal bit energy, and P be the power spectral density of the noise. t G represents the total power of the transmitter. t For the transmit antenna gain, G r For the receiving antenna gain, R b L is the bit rate of the transmitted signal. fs (dB)=10lg(4πdf / c) 2For free space transmission loss, d is the distance between the two satellites, f is the carrier frequency, c is the speed of light, and L0 represents the remaining losses including Doppler shift, antenna pointing error, and polarization loss.

[0072] The power ratio of the communication and navigation components is determined based on the real-time signal-to-noise ratio, using a signal weighting factor h. c Control. h c The larger the value of h, the more navigation components are contained in the fused communication and navigation signal, resulting in better navigation performance and a lower communication error rate. In special cases, when h... c When the value is 0, the signal no longer contains navigation components, and the transmitted signal will become a regular communication signal.

[0073] The power control principle for communication and navigation components is "to maximize the system's navigation performance while meeting the target communication bit error rate." Specifically:

[0074] Step 101: Using simulation or measured data, plot the signal based on the conduction-pass fusion signal under different weighting factors h. c Bit error rate curves at (e.g., 0.1, 0.2, 0.3, 0.4...)

[0075] Step 102, based on different weighting factors h c The bit error rate curve and the target bit error rate (e.g., 10) -5 The intersection points of the curves define the signal-to-noise ratio switching intervals;

[0076] Step 103: Within each signal-to-noise ratio switching interval, determine the weighting factor h that meets the target bit error rate requirement. c The largest h c This refers to the selected weighting factor;

[0077] Step 104, based on the selected weighting factor h c Determine the communication component power P s and navigation component power P c for:

[0078]

[0079] Among them, J n (×) is a Bessel function of the first kind, order n.

[0080] In summary, this invention can be used for the generation and reception of communication and navigation fusion signals in low-Earth orbit (LEO) constellations. By adopting a method based on inter-satellite distance and real-time signal-to-noise ratio (SNR), it adaptively selects signal weighting factors to complete the power allocation of communication and navigation components. Under the premise of meeting the bit error rate requirements of inter-satellite communication, it can improve the positioning accuracy of LEO satellite navigation and enhance the autonomous navigation capability of LEO navigation constellations. This invention is of great significance to the construction, operation, and service of LEO navigation constellations.

Claims

1. A method for generating a low-Earth orbit constellation communication and navigation fusion signal, characterized in that, The application is applied to a transmitting satellite, and comprises the following steps: Step 1, according to the ephemeris information stored in the transmitting satellite and the position information of the receiving satellite, the distance between the transmitting satellite and the receiving satellite is calculated; Step 2, according to the distance between the two satellites and the antenna gain, the real-time signal-to-noise ratio of the inter-satellite channel is estimated as: where E b is the transmitted signal bit energy, N0is the power spectral density of noise, P t is the total power of the transmitter, G t is the gain of the transmitting antenna, G r is the gain of the receiving antenna, R b is the transmitted signal bit rate, L fs (dB) = 10lg(4πdf / c) 2 is the free space transmission loss, d is the distance between two satellites, f is the carrier frequency, c is the speed of light, and L0represents the remaining loss including Doppler shift, antenna pointing error and polarization loss. Step 3, the historical measurement data of the satellite is used to draw the bit error rate curve of the combined navigation and communication signal under different signal weighting factors; Step 4, the target communication bit error rate required by the service is determined, and according to the intersection point of the bit error rate curve of the different signal weighting factors and the target bit error rate curve, the signal-to-noise ratio switching interval is divided; Step 5, in each signal-to-noise ratio switching interval, all the signal weighting factors that can meet the target bit error rate requirement are determined, and the maximum value is selected as the selected signal weighting factor; Step 6, the communication information to be transmitted is subjected to LDPC encoding, level conversion, Gaussian filter and integrator to generate the phase of the communication component; Step 7, the navigation information to be transmitted is subjected to level conversion and shaping filter, and then multiplied by the selected signal weighting factor to obtain the phase of the navigation component; Step 8, the phase of the communication component and the phase of the navigation component are added to obtain the combined navigation and communication phase, and after phase modulation, the combined navigation and communication signal based on GMSK+PN is generated: where P is the total power of the transmitter, ω is the carrier frequency, t is the phase of the communication component, is the phase of the navigation component.​ 2.A method for receiving a low earth orbit constellation integrated navigation and communication signal, characterized in that, The application is applied to a receiving satellite, and is used for receiving and signal separation of the combined navigation and communication signal generated by claim 1, and comprises the following steps: Step 1, the received GMSK+PN combined navigation and communication signal is subjected to GMSK demodulation to obtain the phase of the communication component; Step 2, the obtained phase of the communication component is subjected to GMSK re-modulation to obtain the phase of the regenerated communication signal; Step 3, after the conjugate of the regenerated communication signal phase is taken, the complex domain correlation is performed with the received GMSK+PN combined navigation and communication signal to obtain: wherein is the low pass equivalent of the received signal in the complex domain, is the regenerated communication signal phase, is the phase of the communication component, is the phase of the navigation component, n(t) is noise during transmission; Step 4, the imaginary part of the complex correlation result is taken to obtain the navigation component separated from the GMSK+PN combined navigation and communication signal: wherein to separate the noise carried in the navigation component; Step 5, the separated navigation component is subjected to acquisition and tracking to realize the synchronous demodulation of the navigation signal; Step 6, the position information of the transmitting satellite is calculated according to the synchronous demodulation result; Step 7, the ephemeris information of the receiving satellite itself and the position information of the transmitting satellite are updated.

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