A method for switching feeder links of low-orbit satellites

Abstract

The present invention discloses a low-orbit satellite feed link switching method, which belongs to the field of low-orbit satellite communications. Aiming at the problems of data interruption and loss, large satellite-ground storage resources, and large switching delay during the low-orbit satellite feed switching process, the present invention solves the problem of reliable transmission of satellite-ground feed link data and extension of effective communication time by configuring two sets of independent feed link loads on the satellite and a routing layer switching method for satellite-ground collaboration. The present invention can be applied to various types of low-orbit satellites and low-orbit satellite constellation systems, can ensure reliable interaction of satellite-ground data, and is particularly suitable for autonomous operation after low-orbit satellite networking.

Description

Technical Field

[0001] The invention belongs to the technical field of low-orbit satellite communications, and in particular relates to a low-orbit satellite feeder link switching method. Background Art

[0002] In the context of the development of commercial aerospace and Internet constellations, the development of low-orbit communication constellations has become a consensus. The characteristics of low-orbit satellite ground coverage are global coverage, different orbits have different coverage conditions, and the coverage duration is variable. Taking the satellite orbit altitude of 880km as an example, the satellite's QV band beam width to the ground is 1.5°, and the ground scanning width is ±56°. The direction of the satellite's motion trajectory is "southwest->northeast" or "northwest->southeast", and the low-orbit satellite's ground coverage is simulated as follows:

[0003] The visibility (unit: min) of satellite 01 and satellite 02 to four gateway stations is simulated. (Minimum elevation angle of ground station: 5°; simulation duration: 1 day;)

[0004] 01Simulation results of the visible time between the satellite and the ground station (greater than 10 minutes)

[0005] Beijing Sanya Urumqi Hefei Visible times 3 2 3 2 Minimum time 10.24 10.89 10.18 10.61 Maximum time 11.81 11.30 11.90 11.68 Average time 10.91 11.09 11.067 11.15 Total time 32.74 22.18 33.20 22.29

[0006] 02 Simulation results of the visible time between the satellite and the ground station (greater than 10 minutes)

[0007] Beijing Sanya Urumqi Hefei Visible times 3 2 2 2 Minimum time 10.25 10.73 11.31 10.15 Maximum time 11.81 11.41 11.68 11.75 Average time 10.91 11.07 11.49 10.95 Total time 32.74 22.135 22.98 21.90

[0008] It can be seen that in the one-day simulation cycle, the four locations are visible for more than 10 minutes more than twice a day, and the coverage duration is different each time, with the maximum duration being 11 minutes.

[0009] As the satellite-to-ground channel for communication between low-orbit satellites and ground gateways, the satellite feeder link is responsible for the return and uplink of business data. It is also the uplink and downlink bearer channel for resource allocation, routing calculation, payload management control, and software reconstruction of the ground system. Therefore, taking methods and measures to ensure the reliable transmission between low-orbit satellites and ground gateways and prolong the effective communication time is the main goal of the feeder link design. It is of great practical significance to study the satellite-to-ground reliable communication process based on the feeder link of low-orbit satellites.

[0010] In a low-orbit satellite system, if a single satellite can only see one gateway station in its coverage area, and the feed payload can only establish a feed link with one gateway station in a certain period of time, then after the satellite flies away from the current gateway station, before establishing a link with the next visible station, the link will inevitably be interrupted. If a single satellite can cover more than two gateway stations on the ground at the same time, there is an inter-satellite switching process. The key research focus of the current low-orbit satellite system is to ensure that business data is not lost during the "satellite switching station" process. At present, most low-orbit satellite systems use the "hard switching" process.

[0011] See also Figure 1 When a single satellite performs hard switching between two gateway stations, the low-orbit satellite feed payload is equipped with a set of feed antennas and a set of feed RF channels. The specific process is as follows:

[0012] At T0: the satellite achieves normal communication with gateway station 1 through Q / V antenna 1;

[0013] At T1: the feeder link between the satellite and gateway 1 is interrupted, the satellite payload caches the downlink data, and the ground system stores the uplink data.

[0014] Time T2: The command controls the feed antenna to establish a link with gateway 2.

[0015] During the entire switching process of hard switching, the communication between antenna 1 and gateway 1 is interrupted first, and then the communication between antenna 1 and gateway 2 is established. Information storage is required to ensure that data is not lost; the link establishment process will cause users to feel interrupted. In addition, this method has different requirements for on-board storage space depending on the length of the switching link establishment. Summary of the invention

[0016] In view of this, the present invention proposes a low-orbit satellite feed link switching method. The method configures two feed antennas and two sets of radio frequency channels for each low-orbit satellite, and the ground gateway is equipped with multiple sets of antennas, radio frequency channels and ground receiving systems. The use of this switching method can ensure that the data of each satellite switching gateway is not lost, solves the problems of short communication time between low-orbit satellites and ground gateways, link interruption, and unreliable transmission of business data, and can meet the autonomous operation and autonomous link establishment requirements of the low-orbit constellation system.

[0017] In order to achieve the above object, the technical solution adopted by the present invention is:

[0018] A low-orbit satellite feeder link switching method comprises the following steps:

[0019] Step 1: The operation control center plans the low-orbit satellite operation plan and determines the satellite cross-gateway feed switching time and the gateway station location;

[0020] Step 2: The low-orbit satellite covers gateway station A. The first feed link of the low-orbit satellite establishes a link with gateway station A, establishes normal communication, and maintains the gaze tracking state. According to the mission plan, gateway station A notes the parameters of each gateway station and the start time and switching time of the low-orbit satellite tracking the gateway station through the feed link. At the same time, the low-orbit satellite feed antenna parameters, feed switching time, and gateway station feed beam pointing information are sent to each gateway station through the ground system.

[0021] Step 3: The low-orbit satellite maintains communication with gateway station A. When the low-orbit satellite can simultaneously cover gateway station B at time T0, the feed switching process is started;

[0022] Step 4: The second feeder link tracks and points to gateway station B. The second feeder link of the low-orbit satellite successfully establishes a link with gateway station B and maintains a staring tracking state.

[0023] Step 5: The ground system completes the system routing calculation and routing table update according to the establishment of the second feeder link. The satellite-to-ground routing of the low-orbit satellite system switches all paths of gateway station A to gateway station B.

[0024] Step 6: After the time constraint for establishing a link between the second feeder link of the low-orbit satellite and the gateway station B is met, the first feeder link of the low-orbit satellite is disconnected from the gateway station A, completing the feeder link switching;

[0025] Step 7: The low-orbit satellite maintains communication with gateway station B. When the low-orbit satellite can cover gateway station C, the feeder link tracking is started to point to gateway station C, and the feeder link switching is performed according to steps 3 to 6.

[0026] Furthermore, the low-orbit satellite is equipped with two sets of feed link payloads, including two Q / V band feed link antennas, two sets of feed microwave channels, two sets of baseband signal processing units and two sets of on-board routing switching units. The feed microwave channels include radio frequency and channel power amplifiers; the two sets of feed link payloads are independently controllable and support simultaneous pointing and tracking of two gateway stations.

[0027] Furthermore, the operation and control center records the latitude and longitude parameters and enabling status parameters of the earliest gateway station that is visible and linked after each low-orbit satellite enters the orbit, and the low-orbit satellite stores and calls the recorded parameters.

[0028] Furthermore, it is characterized in that the specific manner of maintaining the gaze tracking state in step 2 and step 4 is:

[0029] (2-1) At the start of the mission, the payload management unit of the low-orbit satellite issues a speed mode command. In the speed mode, the antenna moves from the current position to the target angle at the speed specified in the command.

[0030] (2-2) When the ground gateway station enters the beam range of the antenna unit, the payload management unit issues a tracking mode command. After receiving the tracking mode command, the antenna unit points from the current position to the target angle at the speed specified in the command; the antenna achieves staring at the ground gateway station.

[0031] Furthermore, the specific method of step (5) is:

[0032] (5-1) Gateway B successfully establishes the second feeder link with the satellite;

[0033] (5-2) Gateway B reports the satellite-ground topology changes to the ground system space-based network controller;

[0034] (5-3) The space-based network controller performs satellite-to-ground routing calculations and configures the latest forwarding tables for gateway stations A and B, completing routing diffusion across the entire network;

[0035] (5-4) The space-based network controller pushes mapping update messages to the gateway station B and to each satellite terminal;

[0036] (5-5) The satellite terminal and gateway B reply with a mapping update response;

[0037] (5-6) All paths of gateway station A are switched to gateway station B.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] 1. The present invention introduces a "soft switching" method for low-orbit satellite power feeding and proposes a process for soft switching of satellite-to-ground power feeding.

[0040] 2. The entire process does not require the use of cache, ensuring that user communications are not interrupted and data is not lost.

[0041] 3. By configuring two sets of independent feeder link loads, routing layer switching is supported, and the routing layer switching delay is 0ms.

[0042] 4. A single satellite can reliably switch between two gateway stations, effectively increasing the communication time between a single satellite and the gateway station and the amount of satellite-ground information exchange data, providing effective guarantee for the reliable operation of the system and improving the quality of user service.

[0043] 5. Satellite feed “soft switching” is applicable to autonomous operation after low-orbit satellite networking.

[0044] In summary, the present invention solves the problems of interruption, data loss, large satellite and ground storage resource requirements, and large switching delay during the switching of satellite feeder links by configuring two sets of independent feeder link loads on the satellite and switching the routing layer through satellite-ground coordination. The present invention can be applied to low-orbit satellite networking systems to achieve reliable satellite-ground data interaction, and is particularly suitable for autonomous operation after low-orbit satellite networking. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of conventional feeder link hard switching in the prior art.

[0046] Figure 2 It is a feeder link composition diagram of the present invention.

[0047] Figure 3 It is a schematic diagram of the switching principle of the present invention.

[0048] Figure 4 It is a flow chart of the present invention.

[0049] Figure 5It is a schematic diagram of the routing layer switching process of the present invention. DETAILED DESCRIPTION

[0050] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0051] A low-orbit satellite feeder link switching method comprises the following steps:

[0052] Step 1: The operation control center plans the low-orbit satellite operation plan and determines the satellite cross-gateway feed switching time and the gateway station location;

[0053] Step 2: The low-orbit satellite enters the territory and covers gateway station A. The first feed link of the low-orbit satellite establishes a link with gateway station A, establishes normal communication, and maintains the gaze tracking state. According to the mission plan, gateway station A notes the parameters of each gateway station and the start and switching time of the low-orbit satellite tracking the gateway station through the feed link. At the same time, it sends the low-orbit satellite feed antenna parameters, feed switching time, and gateway station feed beam pointing information to each gateway station through the ground system;

[0054] Step 3: The satellite maintains communication with gateway station A. According to the mission plan, the satellite can simultaneously cover gateway station B at time T0 and start the feed switching process.

[0055] Step 4: The second feeder link tracks and points to gateway station B. The satellite's second feeder link successfully establishes a link with gateway station B and maintains a staring tracking state.

[0056] Step 5: The ground system completes the system route calculation and routing table update based on the establishment of the second feeder link. All paths of gateway station A are switched to gateway station B.

[0057] Step 6: According to the time constraint (20 seconds after the second feeder link establishes a link with gateway B), the first feeder link is disconnected from gateway A, completing the feeder link switching.

[0058] Step 7: The satellite maintains communication with gateway station B. The satellite can cover gateway station C, start feeder link tracking to point to gateway station C, and repeat steps 3 to 6.

[0059] The entire process does not require the use of cache, ensuring reliable data transmission without interrupting user communications.

[0060] Furthermore, the low-orbit satellite is equipped with two sets of feed link payloads, including two Q / V band feed link antennas, two sets of feed microwave channels (including RF and channel power amplifiers) and two sets of signal processing units; the two sets of feed links are independently controllable, supporting the pointing tracking of two signal gateways at the same time, and quickly realizing the switching of a single satellite between signal gateways through routing layer switching.

[0061] In the further step 2, the operation control center records the latitude and longitude parameters and enabling status parameters of all ground gateway stations (see Table 1), the order of gateway stations visible after each orbit of the satellite enters, and the tracking start time (see Table 2), which are then stored and called by the satellite.

[0062] Table 1 Gateway parameter information

[0063]

[0064] Since the feed link load is configured with two independent loads (including baseband processing, transceiver channels, power amplifier, antenna, etc.), the two feed links can be controlled independently, and switching can be achieved by simply planning the time.

[0065] Table 2 Link building table (configuration of the first feeder link and the second feeder link)

[0066]

[0067] The specific methods of antenna pointing tracking and staring in steps (2) and (4) are as follows:

[0068] (2-1) When the satellite flies to point A (the remaining ΔT = TB-TA time from entering the antenna beam range, such as ΔT = 3 minutes), the payload management unit issues a speed mode command. In the speed mode, the antenna points from the current position to the target angle (X-axis target angle, Y-axis target angle) at the speed in the command;

[0069] (2-2) When ΔT = 3 min, that is, when the satellite flies to point B, the ground gateway station enters the beam range of the antenna unit, and the payload management unit issues a tracking mode command. After receiving the tracking mode command, the antenna unit points from the current position to the target angle (X-axis target angle, Y-axis target angle) at the speed specified in the command;

[0070] The specific method of step (5) is:

[0071] (5-1) Gateway B detects the target satellite feed beam;

[0072] (5-2) Gateway B reports the satellite-ground topology changes to the space-based network controller;

[0073] (5-3) The space-based network controller performs satellite-to-ground routing calculations and configures forwarding tables for gateways A and B;

[0074] (5-4) The base network controller pushes a mapping update message to the gateway station B and the satellite terminal;

[0075] (5-5) The satellite terminal and gateway B reply with a mapping update response;

[0076] (5-6) All paths of gateway station A are switched to gateway station B.

[0077] The specific method of step (6) is:

[0078] (6-1) Task planning: 20 seconds after the second feeder link establishes a link with gateway station B, the first feeder link is disconnected from gateway station A.

[0079] (6-2) When the load management unit issues an instruction, after receiving the standby instruction, antenna 1 stops at the current beam pointing position and resets the beam pointing of antenna 1 to zero.

[0080] Figure 1 The figure shows the process of hard switching of a low-orbit satellite between two gateways, in which the low-orbit satellite feed payload is equipped with a set of feed antennas and a set of feed RF channels. The specific method is:

[0081] At T0: the satellite achieves normal communication with gateway station 1 through Q / V antenna 1;

[0082] At T1: the feeder link between the satellite and gateway 1 is interrupted, the satellite payload caches the downlink data, and the ground system stores the uplink data.

[0083] Time T2: The command controls the feed antenna to establish a link with gateway 2.

[0084] During the entire switching process of hard switching, the communication between antenna 1 and gateway 1 is interrupted first, and then the communication between antenna 1 and gateway 2 is established. Information storage is required to ensure that data is not lost; the link establishment process will cause user-perceived interruption. Different degrees of storage space are required on the satellite depending on the switching link establishment time.

[0085] like Figure 2 The figure shows the composition diagram of the feeder link of a low-orbit satellite communication system, which includes the integrated processing load and feeder load of the low-orbit satellite payload system.

[0086] Among them, the feeding load includes 2 sets of feeding link RF channels, 1 set of feeding antenna controller, and 2 sets of feeding antennas.

[0087] The main functions of the integrated processing payload include two sets of feeder link baseband processing units, a system routing interaction unit, and a payload management control unit.

[0088] Figure 3 Based on Figure 2 The schematic diagram of the feeding switching principle of the feeding link is shown, where:

[0089] At time T0, the satellite communicates normally with gateway station 1 through Q / V antenna 1, and Q / V antenna 2 points to gateway station B in advance;

[0090] At time T1, antenna 2 establishes a link with gateway B and the routing table is updated;

[0091] At time T2: according to the time constraint (20 seconds after antenna 2 establishes a link with gateway B), antenna 1 disconnects from the gateway, completing the feeder link switching. The entire process does not require the use of cache, ensuring that user communications are not interrupted.

[0092] Figure 4 The specific process of feed switching is as follows:

[0093] (1) The operation and control center plans the low-orbit satellite operation plan and determines the satellite cross-gateway feed switching time and the gateway station location;

[0094] (2) The low-orbit satellite enters the territory of the country and covers gateway station A. The first feed link of the low-orbit satellite establishes a link with gateway station A, establishes normal communication, and maintains the gaze tracking state. According to the mission plan, gateway station A notes the parameters of each gateway station and the start and switch time of the low-orbit satellite tracking the gateway station through the feed link. At the same time, it sends the low-orbit satellite feed antenna parameters, feed switch time, and gateway station feed beam pointing information to each gateway station through the ground system;

[0095] (3) The satellite maintains communication with gateway station A. According to the mission plan, the satellite can simultaneously cover gateway station B at time T0 and start the feed switching process.

[0096] (4) The second feeder link tracks and points to gateway station B. The satellite's second feeder link successfully establishes a link with gateway station B and maintains a staring tracking state.

[0097] (5) The ground system completes the system routing calculation and routing table update based on the establishment of the second feeder link. All paths of gateway station A are switched to gateway station B.

[0098] (6) According to the time constraint (20 seconds after the second feeder link establishes a link with gateway B), the first feeder link is disconnected from gateway A, completing the feeder link switching.

[0099] (7) The satellite maintains communication with gateway B. The satellite can cover gateway C. The feeder link tracking is started to point to gateway C. Steps 3 to 6 are repeated.

[0100] Figure 5 The specific process of routing switching is as follows:

[0101] (5-1) Gateway B (destination gateway) detects the destination satellite feed beam;

[0102] (5-2) Gateway B (destination gateway) reports the satellite-ground topology changes to the space-based network controller;

[0103] (5-3) The space-based network controller performs satellite-to-ground routing calculations and configures forwarding tables for gateways A and B;

[0104] (5-4) Gateway B (destination gateway) pushes a mapping update message to the satellite terminal;

[0105] (5-5) The satellite terminal sends a mapping update response to gateway B (destination gateway);

[0106] (5-6) All paths of gateway station A are switched to gateway station B.

[0107] In summary, the present invention solves the problems of interruption, data loss, large satellite and ground storage resource requirements, and large switching delay during the switching of satellite feeder links by configuring two sets of independent feeder link loads on the satellite and switching the routing layer through satellite-ground coordination. The present invention can be applied to low-orbit satellite networking systems to achieve reliable satellite-ground data interaction, and is particularly suitable for autonomous operation after low-orbit satellite networking.

[0108] Those skilled in the art should understand that any modification or equivalent replacement based on the technical solution of the present invention does not deviate from the spirit and scope of the design method and technical solution of the present invention, and should be included in the protection scope of the present invention. At the same time, some parts not described in detail in the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A low-orbit satellite feeder link switching method, characterized in that: The following steps are involved: Step 1: The operation control center plans the low-orbit satellite operation plan and determines the satellite cross-gateway feed switching time and the gateway station location; Step 2: The low-orbit satellite covers gateway station A. The first feed link of the low-orbit satellite establishes a link with gateway station A, establishes normal communication, and maintains the gaze tracking state. According to the mission plan, gateway station A notes the parameters of each gateway station and the start time and switching time of the low-orbit satellite tracking the gateway station through the feed link. At the same time, the low-orbit satellite feed antenna parameters, feed switching time, and gateway station feed beam pointing information are sent to each gateway station through the ground system. Step 3: The low-orbit satellite maintains communication with gateway station A. When the low-orbit satellite can simultaneously cover gateway station B at time T0, the feed switching process is started; Step 4: The second feeder link tracks and points to gateway station B. The second feeder link of the low-orbit satellite successfully establishes a link with gateway station B and maintains a staring tracking state. Step 5: The ground system completes the system routing calculation and routing table update according to the establishment of the second feeder link. The satellite-to-ground routing of the low-orbit satellite system switches all paths of gateway station A to gateway station B. The specific method is as follows: (5-1) Gateway B successfully establishes the second feeder link with the satellite; (5-2) Gateway B reports the satellite-ground topology changes to the ground system space-based network controller; (5-3) The space-based network controller performs satellite-to-ground routing calculations and configures the latest forwarding tables for gateway stations A and B, completing routing diffusion across the entire network; (5-4) The space-based network controller pushes mapping update messages to the gateway station B and to each satellite terminal; (5-5) The satellite terminal and gateway B reply with a mapping update response; (5-6) All paths of gateway station A are switched to gateway station B; Step 6: After the time constraint for establishing a link between the second feeder link of the low-orbit satellite and the gateway station B is met, the first feeder link of the low-orbit satellite is disconnected from the gateway station A, completing the feeder link switching; Step 7: The low-orbit satellite maintains communication with gateway station B. When the low-orbit satellite can cover gateway station C, the feeder link tracking is started to point to gateway station C, and the feeder link switching is performed according to steps 3 to 6; The low-orbit satellite is equipped with two sets of feed link payloads, including two Q / V band feed link antennas, two sets of feed microwave channels, two sets of baseband signal processing units and two sets of onboard routing switching units, and the feed microwave channels include radio frequency and channel power amplifiers; The two sets of feeder link payloads are independently controllable and support simultaneous pointing and tracking of two gateway stations.

2. A low-orbit satellite feeder link switching method as claimed in claim 1, characterized in that: The operation and control center records the latitude and longitude parameters and enabling status parameters of the earliest gateway station that is visible and linked to the low-orbit satellite after each orbit enters the low-orbit satellite, and the low-orbit satellite stores and calls the recorded parameters.

3. A low-orbit satellite feeder link switching method as claimed in claim 1, characterized in that: The specific way to maintain gaze tracking in steps 2 and 4 is as follows: (2-1) At the start of the mission, the payload management unit of the low-orbit satellite issues a speed mode command. In the speed mode, the antenna moves from the current position to the target angle at the speed specified in the command. (2-2) When the ground gateway station enters the beam range of the antenna, the payload management unit issues a tracking mode command. After receiving the tracking mode command, the antenna points from the current position to the target angle at the speed specified in the command. The antenna realizes staring at the ground gateway station.

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