Large-scale low-orbit satellite constellation network access node selection method

Abstract

The invention relates to a large-scale low-orbit satellite constellation network access node selection method, and belongs to the technical field of satellite communication. The method comprises the following steps: firstly, calculating positions and beam coverage conditions of high and low orbit satellites in an earth-fixed coordinate system at each moment through ephemeris, platform and load information of the satellites; secondly, designing an adaptability function according to the position relation between satellites, beam coverage, communication link channel quality and service demand conditions; and finally, a satellite suitable for serving as a network access node is selected from a large-scale low-orbit satellite constellation through a genetic algorithm. The method can be used for realizing efficient dynamic connection node selection in high-orbit and low-orbit satellite combined networking, so that functions of resource coordination, load balancing and the like among satellites are realized, and the deployment efficiency of a large-scale low-orbit satellite constellation is improved.

Description

Technical Field

[0001] The present invention belongs to the field of satellite communication technology, and in particular to a method for selecting network access nodes in a large-scale low-orbit satellite constellation, which is suitable for selecting network access nodes in a large-scale low-orbit satellite constellation. Background Art

[0002] The Starlink plan proposed by SpaceX of the United States is the giant low-orbit satellite constellation with the largest number of satellites to date. The entire plan will deploy about 42,000 small satellites in low-Earth orbit, including satellite constellations at different orbital altitudes and several ground stations. There was no intersatellite link between early Starlink satellites, and communications between satellites had to be relayed through earth stations, which resulted in the Starlink service being unable to cover places where there was no way to establish an earth station. The biggest improvement in the 1.5 version of the Starlink satellite is the ability to provide inter-satellite laser communication. Since the first batch of improved satellites were launched into orbit in September 2021, subsequent satellites have been equipped with laser intersatellite link components, which can realize information transmission and exchange between Starlink satellites in the air, and data can be transmitted directly between satellites. Direct communication between Starlink satellites in orbit greatly reduces dependence on earth stations and improves the low-latency service guarantee capability of the Starlink system.

[0003] Large-scale low-orbit satellite constellations with inter-satellite links are the future development direction of low-orbit satellite communications. At the same time, through the unified networking design of low-orbit satellite constellations and high-orbit satellites, the dependence of satellite constellations on ground stations can be further reduced, and the reliability of the system can be improved. In the unified networking of low-orbit satellite constellations and high-orbit satellites, it is necessary to select a part of low-orbit satellites as large-scale low-orbit satellite constellation network nodes to play the role of business aggregation. However, there is no such solution in the existing technology. Summary of the invention

[0004] The present invention aims at the problem of selecting network access nodes in large-scale low-orbit satellite constellation networking, and proposes a large-scale low-orbit satellite constellation network access node selection method. The method selects satellites suitable as network access nodes in a large-scale low-orbit satellite constellation through a genetic algorithm.

[0005] The technical solution adopted by the present invention is:

[0006] A method for selecting access nodes in a large-scale low-orbit satellite constellation network comprises the following steps:

[0007] Step 1: Calculate the position and beam coverage of high-orbit and low-orbit satellites in the earth-fixed coordinate system at each moment through the satellite's ephemeris, platform and payload information;

[0008] Step 2, designing a fitness function based on the positional relationship between satellites, beam coverage, communication link channel quality, and service demand;

[0009] Step 3: According to the fitness function designed in step 2, a satellite suitable as a network access node is selected from a large-scale low-orbit satellite constellation through a genetic algorithm.

[0010] Furthermore, the specific method of step 1 is:

[0011] Step 1-1, using the satellite ephemeris information, calculate the position of the high-orbit and low-orbit satellites in the earth-fixed coordinate system at each moment; wherein the transponder of the high-orbit satellite is transparent forwarding or processing forwarding, and the transponder of the low-orbit satellite is processing forwarding;

[0012] Step 1-2, through the satellite platform and payload information, calculate the satellite beam coverage of high-orbit and low-orbit satellites at each moment, including the coverage of high-orbit satellites over low-orbit satellites and the ground, and the coverage of low-orbit satellites over the ground, and establish a communication link between high-orbit satellites and low-orbit satellites.

[0013] Furthermore, the specific method of step 2 is:

[0014] Step 2-1, based on the positional relationship between satellites, in order to make the network access node have as many adjacent low-orbit satellites as possible, the following fitness function is designed:

[0015] f1=n / N

[0016] Where n is the number of adjacent low-orbit satellites of the candidate network access node, and N is the total number of low-orbit satellites;

[0017] Step 2-2, based on the positional relationship between satellites and the coverage of high-orbit satellite beams, in order to make the network access node have more connections with the high-orbit satellites and be as close to the high-orbit satellites as possible, the following fitness function is designed:

[0018] f2=l / L+10 / min(d1 d2 d3…d l )

[0019] Where, l is the number of high-orbit satellites that the alternative network access node can connect to, L is the total number of high-orbit satellites, d1d2 d3…d l The distance from the candidate network access node to each high-orbit satellite that can be connected, in km, min (*) means the minimum value;

[0020] Step 2-3, according to the conditions of high-orbit satellite payloads and low-orbit satellite payloads, considering the signal-to-noise ratio and signal bandwidth of the communication link between the high-orbit satellite and the network access node, the following fitness function is designed:

[0021] f3=SNR1+0.1*BW1+SNR2+0.1*BW2+…SNR l +0.1*BWl

[0022] Wherein, SNR is the signal-to-noise ratio of the communication link between the high-orbit satellite and the alternative network access node, in dB, BW is the signal bandwidth of the communication link between the high-orbit satellite and the alternative network access node, in kHz, and l is the number of high-orbit satellites that the alternative network access node can connect to;

[0023] Step 2-4, considering the service traffic of the network access node, design the following fitness function:

[0024] f4=S0+S1+S2+…S n

[0025] Among them, S0 is the expected traffic volume of the candidate network access node, n is the number of adjacent low-orbit satellites of the candidate network access node, S1, S2, ..., S n is the traffic volume between the candidate network access node and each adjacent low-orbit satellite, in Kbyte;

[0026] Step 2-5, combine various fitness functions to get the final fitness function:

[0027] f=af1+bf2+cf3+df4

[0028] Among them: a, b, c, d are weights.

[0029] Furthermore, the specific method of step 3 is:

[0030] Step 3-1, set the number of low-orbit satellites N, the number of high-orbit satellites L, the population number M of the genetic algorithm, as well as the initial network node probability P, mutation probability Pm, crossover probability Pc, and number of iterations G of the genetic algorithm. The chromosome length is equal to the number of low-orbit satellites N;

[0031] Step 3-2, binary code the population, set the satellite as a network node to "1", and set other satellites to "0". Initially, the position of "1" is randomly set according to probability P;

[0032] Step 3-3, calculate the position of the satellite at a certain moment according to the satellite ephemeris, configure the signal-to-noise ratio and signal bandwidth of the inter-satellite communication link, and the traffic volume of each low-orbit satellite, calculate the fitness f of the node in the individual, and then obtain the current fitness of each individual, and calculate the selection probability;

[0033] Step 3-4, crossover the population with probability Pc and mutation with probability Pm;

[0034] Step 3-5, update the population, select some individuals with the highest fitness to replace some individuals with the lowest fitness;

[0035] Step 3-6, determine whether the number of iterations has been reached. If so, the algorithm ends, and the "1" in the individual represents the location of the network access node. Otherwise, return to step 3-3 to continue iteration.

[0036] Compared with the background technology, the present invention has the following advantages:

[0037] 1. The suitability function designed by the present invention takes into account the number of adjacent satellites, the positional relationship between satellites, beam coverage, communication link channel quality, and the service flow between the node and the adjacent satellites, so as to better select satellites suitable as network nodes.

[0038] 2. The large-scale low-orbit satellite constellation network access nodes selected by the present invention can realize efficient dynamic connection between high-orbit and low-orbit satellites, achieve resource coordination and load balancing among satellites, and improve the deployment efficiency of large-scale low-orbit satellite constellations. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a flow chart of an embodiment of the present invention.

[0040] Figure 2 It is a schematic diagram of an application scenario of the present invention. DETAILED DESCRIPTION

[0041] The present invention is described in detail below with reference to the accompanying drawings.

[0042] A method for selecting network nodes in a large-scale low-orbit satellite constellation. The method first calculates the position and beam coverage of high and low-orbit satellites in the earth-fixed coordinate system at each moment through the satellite's orbit, platform and payload information; then, a fitness function is designed according to the position relationship between satellites, beam coverage, communication link channel quality and service demand; finally, a satellite suitable as a network access node is selected in the large-scale low-orbit satellite constellation through a genetic algorithm.

[0043] like Figure 1 As shown, the method specifically comprises the following steps:

[0044] Step 1: Calculate the position and beam coverage of high and low orbit satellites in the ground-fixed coordinate system at each moment through the satellite's ephemeris, platform and payload information. Application scenarios include Figure 2 shown.

[0045] The specific steps of step 1 are as follows:

[0046] Step 1-1, using the satellite ephemeris information, calculate the position of the high-orbit and low-orbit satellites in the earth-fixed coordinate system at each moment; wherein the transponder of the high-orbit satellite is transparent forwarding or processing forwarding, and the transponder of the low-orbit satellite is processing forwarding;

[0047] Step 1-2, through the satellite platform and payload information, calculate the satellite beam coverage of high-orbit and low-orbit satellites at each moment, including the coverage of high-orbit satellites over low-orbit satellites and the ground, and the coverage of low-orbit satellites over the ground, and establish a communication link between high-orbit satellites and low-orbit satellites.

[0048] Step 2: Design a fitness function based on the positional relationship between satellites, beam coverage, communication link channel quality, and service demand.

[0049] The specific method of step 2 is as follows:

[0050] Step 2-1, based on the positional relationship between satellites, in order to make the network access node have as many adjacent low-orbit satellites as possible, the following fitness function is designed:

[0051] f1=n / N

[0052] Where n is the number of adjacent low-orbit satellites of the candidate network access node, and N is the total number of low-orbit satellites;

[0053] Step 2-2, based on the positional relationship between satellites and the coverage of high-orbit satellite beams, in order to make the network access node have more connections with the high-orbit satellites and be as close to the high-orbit satellites as possible, the following fitness function is designed:

[0054] f2=l / L+10 / min(d1 d2 d3…d l )

[0055] Where, l is the number of high-orbit satellites that the alternative network access node can connect to, L is the total number of high-orbit satellites, d1d2 d3…d l The distance from the candidate network access node to each high-orbit satellite that can be connected, in km, min (*) means the minimum value;

[0056] Step 2-3, according to the conditions of high-orbit satellite payload and low-orbit satellite payload, considering the signal-to-noise ratio and signal bandwidth of the communication link between the high-orbit satellite and the network access node, the following fitness function is designed:

[0057] f3=SNR1+0.1*BW1+SNR2+0.1*BW2+…SNR l +0.1*BW l

[0058] Wherein, SNR is the signal-to-noise ratio of the communication link between the high-orbit satellite and the alternative network access node, in dB, BW is the signal bandwidth of the communication link between the high-orbit satellite and the alternative network access node, in kHz, and l is the number of high-orbit satellites that the alternative network access node can connect to;

[0059] Step 2-4, considering the service traffic of the network access node, design the following fitness function:

[0060] f4=S0+S1+S2+…S n

[0061] Among them, S0 is the expected traffic volume of the candidate network access node, n is the number of adjacent low-orbit satellites of the candidate network access node, S1, S2, ..., S n is the traffic volume between the candidate network access node and each adjacent low-orbit satellite, in Kbyte;

[0062] Step 2-5, combine various fitness functions to get the final fitness function:

[0063] f=af1+bf2+cf3+df4

[0064] Among them, a, b, c, and d are weights. The purpose of weighting is to make the values ​​of af1, bf2, cf3, and df4 as close as possible. In this example, a=0.8, b=0.6, c=0.001, and d=0.001.

[0065] Step 3: According to the fitness function designed in step 2, a genetic algorithm is used to select satellites suitable as network nodes in a large-scale low-orbit satellite constellation.

[0066] The specific method of step 3 is as follows:

[0067] Step 3-1, assuming that the number of low-orbit satellites N = 1000, the number of high-orbit satellites L = 10, the population size of the genetic algorithm M = 50, the chromosome length is equal to the number of low-orbit satellites N, the mutation probability of the genetic algorithm Pm = 0.05, the crossover probability Pc = 0.8, and the number of iterations G = 200;

[0068] Step 3-2, binary code the population, set the satellite as a network node to "1", otherwise set to "0", and set the position of "1" randomly, with the probability of "1" in an individual being P = 0.1;

[0069] Step 3-3, calculate the position of the satellite at a certain moment according to the satellite ephemeris, configure the signal-to-noise ratio, signal bandwidth, and traffic volume of each low-orbit satellite of the connectable inter-satellite communication link, calculate the fitness f of the node in the individual, and then obtain the current fitness of each individual, and calculate the selection probability;

[0070] Step 3-4, crossover is performed on the population with a probability of Pc = 0.8 and mutation is performed with a probability of Pm = 0.05;

[0071] Step 3-5, update the population and select individuals with high fitness to replace individuals with low fitness;

[0072] Step 3-6, determine whether the number of iterations has been reached. If so, the algorithm ends, and the "1" in the individual represents the location of the network access node. Otherwise, return to step 3-3 to continue iteration.

[0073] The present invention can be used to realize the selection of efficient dynamic connection nodes in the joint networking of high- and low-orbit satellites, thereby realizing functions such as resource coordination and load balancing among satellites, and improving the deployment efficiency of large-scale low-orbit satellite constellations.

Claims

1. A method for selecting access nodes in a large-scale low-orbit satellite constellation network, characterized in that: The steps include: Step 1: Calculate the position and beam coverage of high-orbit and low-orbit satellites in the earth-fixed coordinate system at each moment through the satellite's ephemeris, platform and payload information; Step 2, designing a fitness function based on the positional relationship between satellites, beam coverage, communication link channel quality, and service demand; Step 3: According to the fitness function designed in step 2, a satellite suitable as a network access node is selected from a large-scale low-orbit satellite constellation through a genetic algorithm.

2. A method for selecting access nodes in a large-scale low-orbit satellite constellation network according to claim 1, characterized in that: The specific method of step 1 is: Step 1-1, using the satellite ephemeris information, calculate the position of the high-orbit and low-orbit satellites in the earth-fixed coordinate system at each moment; wherein the transponder of the high-orbit satellite is transparent forwarding or processing forwarding, and the transponder of the low-orbit satellite is processing forwarding; Step 1-2, through the satellite platform and payload information, calculate the satellite beam coverage of high-orbit and low-orbit satellites at each moment, including the coverage of high-orbit satellites over low-orbit satellites and the ground, and the coverage of low-orbit satellites over the ground, and establish a communication link between high-orbit satellites and low-orbit satellites.

3. The method for selecting access nodes of a large-scale low-orbit satellite constellation network according to claim 1, characterized in that: The specific method of step 2 is: Step 2-1, based on the positional relationship between satellites, in order to make the network access node have as many adjacent low-orbit satellites as possible, the following fitness function is designed: f1=n / N Where n is the number of adjacent low-orbit satellites of the candidate network access node, and N is the total number of low-orbit satellites; Step 2-2, based on the positional relationship between satellites and the coverage of high-orbit satellite beams, in order to make the network access node have more connections with the high-orbit satellites and be as close to the high-orbit satellites as possible, the following fitness function is designed: <h2 style=";text-align:left;direction:ltr">f2 = l / L + 10 / min(d1 d2 d3…d<h2 style=";text-align:left;direction:ltr"> l <h2 style=";text-align:left;direction:ltr"> ) Where l is the number of high-orbit satellites that the alternative network access node can connect to, L is the total number of high-orbit satellites, d1 d2d3…d l The distance from the candidate network access node to each high-orbit satellite that can be connected, in km, min (*) means the minimum value; Step 2-3, according to the conditions of high-orbit satellite payloads and low-orbit satellite payloads, considering the signal-to-noise ratio and signal bandwidth of the communication link between the high-orbit satellite and the network access node, the following fitness function is designed: f3=SNR1+0.1*BW1+SNR2+0.1*BW2+…SNR l +0.1*BW l Wherein, SNR is the signal-to-noise ratio of the communication link between the high-orbit satellite and the alternative network access node, in dB, BW is the signal bandwidth of the communication link between the high-orbit satellite and the alternative network access node, in kHz, and l is the number of high-orbit satellites that the alternative network access node can connect to; Step 2-4, considering the service traffic of the network access node, design the following fitness function: f4=S0+S1+S2+…S n Among them, S0 is the expected traffic volume of the candidate network access node, n is the number of adjacent low-orbit satellites of the candidate network access node, S1, S2, ..., S n is the traffic volume between the candidate network access node and each adjacent low-orbit satellite, in Kbyte; Step 2-5, combine various fitness functions to get the final fitness function: f=af1+bf2+cf3+df4 Among them, a, b, c, and d are weights.

4. The method for selecting access nodes of a large-scale low-orbit satellite constellation network according to claim 1, characterized in that: The specific method of step 3 is: Step 3-1, set the number of low-orbit satellites N, the number of high-orbit satellites L, the population number M of the genetic algorithm, as well as the initial network node probability P, mutation probability Pm, crossover probability Pc, and number of iterations G of the genetic algorithm. The chromosome length is equal to the number of low-orbit satellites N; Step 3-2, binary code the population, set the satellite as a network node to "1", and other satellites to "0". Initially, the position of "1" is randomly set according to probability P; Step 3-3, calculate the position of the satellite at a certain moment according to the satellite ephemeris, configure the signal-to-noise ratio and signal bandwidth of the inter-satellite communication link, and the traffic volume of each low-orbit satellite, calculate the fitness f of the node in the individual, and then obtain the current fitness of each individual, and calculate the selection probability; Step 3-4, crossover the population with probability Pc and mutation with probability Pm; Step 3-5, update the population, select some individuals with the highest fitness to replace some individuals with the lowest fitness; Step 3-6, determine whether the number of iterations has been reached. If so, the algorithm ends, and the "1" in the individual represents the location of the network access node. Otherwise, return to step 3-3 and continue iterating.

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