High-toughness anti-interference satellite communication method based on dual-beam user terminal and multiple satellites

Abstract

The invention provides a high-toughness anti-interference satellite communication method based on a dual-beam user terminal and multiple satellites, and belongs to the field of satellite communication. The high-toughness anti-interference satellite communication method aims at solving the problem that a satellite communication system is easily interfered and attacked due to open channels and relatively fixed satellite orbit information. When a main beam of a user terminal works, a standby beam performs polling detection among available communication resources of a plurality of satellites to obtain a channel state, and when the main beam is interfered and attacked and the communication is interrupted, the standby beam is switched to the main beam in an extremely short time, the communication is recovered and kept smooth, and the main beam is synchronously switched to the standby beam, so that the communication efficiency is improved. And polling is continued among the available communication resources, so that relatively high toughness and relatively strong anti-interference capability of the user satellite communication network are formed. The method is short in anti-interference and communication-keeping processing time after the satellite communication system is interfered, and is suitable for design and development of key user satellite communication systems and user terminals with toughness and anti-interference communication requirements as the main.

Description

Technical Field

[0001] The invention relates to a high-toughness anti-interference satellite communication method based on a dual-beam user terminal and multiple satellites, and belongs to the field of satellite communication. Background Art

[0002] Satellite communication systems have become an important or even the only means of communication assurance for cross-regional joint applications, remote and offshore applications, and other outstanding features, due to their wide communication coverage and flexible networking without relying on ground infrastructure. Because satellite communication channels are open and satellite orbit information is relatively fixed, satellite communication systems are vulnerable to interference attacks from wireless channels. For example, the satellite communication countermeasure system (CCS system) developed and deployed in batches abroad can basically paralyze transparent forwarding satellites or significantly degrade the processing and forwarding satellite capabilities through high-power blocking interference signals. Based on the actual application requirements of strong electromagnetic countermeasures, satellite communication systems used for important tasks or important users are required to have high resilience and strong anti-interference capabilities.

[0003] At present, my country's in-orbit communication satellites are mainly transparent forwarding satellites in geosynchronous orbits, supplemented by a small number of geosynchronous orbit processing forwarding satellites. The satellite communication guarantee plan for key application areas mainly adopts the method of mobilizing multiple satellites and multiple beams to form multiple coverage. When malicious interference is encountered, it takes measures such as replacing transponders and satellites to counter it. However, because various types of satellite communication user terminals mostly use single beam operation, when anti-interference measures are taken after being disturbed, there are deficiencies such as difficulty in coordinating backup communication resources and long satellite switching operations. After being disturbed, it takes a long time from communication interruption to communication restoration, and the communication guarantee resilience and anti-interference ability are insufficient. Summary of the invention

[0004] The present invention aims to solve the problem that it takes too long for a satellite communication user station to restore a communication link after being attacked by interference. A highly resilient and anti-interference satellite communication method based on a dual-beam user terminal and multiple satellites is proposed. By increasing the number of available satellites in the system and considering that it is difficult for an opponent to interfere with and suppress multiple communication satellites at the same time, a multi-satellite communication joint application method with a dual-beam user terminal as the core is designed. This reduces the recovery time of a communication link after interference from hours to seconds, thereby providing key users with a resilient and anti-interference satellite communication guarantee method.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A high-resilience anti-interference satellite communication method based on dual-beam user terminals and multiple satellites, which is implemented based on dual-beam user terminals of user communication station type, multiple communication satellites and central stations / regional stations;

[0007] The dual-beam user terminal of the user communication station type is equipped with two antenna radio frequency units that simultaneously transmit and receive beams in different directions, two channel processing units that simultaneously process beams, a service access and processing unit, and a main control unit. The antenna radio frequency unit and channel processing unit that process one beam are called a channel. The dual-beam user terminal initially selects one channel as the current main channel and the other channel as the backup channel; multiple communication satellites are all geosynchronous orbit communication satellites. Initially, one communication satellite is selected as the main satellite, and the rest are backup satellites; the central station / regional station is equipped with multiple sets of antenna radio frequency units and channel processing units, and a set of service access and processing units;

[0008] The processing process on the dual-beam user terminal side is:

[0009] Step 1: The dual-beam user terminal uses the current main channel to establish a main communication link with the central station / regional station through the main satellite, and performs two-way communication with the central station / regional station through the internal service access and processing unit and the current main channel. During the communication process, the current main channel reports the link status to the main control unit; at the same time, the dual-beam user terminal uses the backup channel to establish a backup communication link with the central station / regional station through the backup satellite. The backup channel periodically polls and detects between multiple different backup satellites to obtain the channel status, and reports the obtained channel status to the main control unit; wherein the link status includes carrier lock indication, decoding lock indication, bit error rate indication and receiving signal-to-noise ratio indication;

[0010] Step 2: The main control unit makes a judgment based on the link status reported by the current main channel. When it is judged that the main satellite is interfered by a high-power interference station, resulting in the interruption or degradation of the communication link exceeding a predetermined threshold, the control service access and processing unit switches the user service data from the current main channel to the backup channel, and selects a backup satellite as the main satellite according to the channel status reported by the backup channel, and uses the backup channel as the current main channel;

[0011] The processing process on the central station / regional station side is:

[0012] Step 3: Multiple antenna radio frequency units and channel processing units in the central station / regional station simultaneously receive wireless signals from multiple communication satellites. The service access and processing unit in the central station / regional station detects user service data, selects the primary channel, and sends the service data to the dual-beam user terminal side via the primary satellite;

[0013] Step 4: When the primary satellite is attacked by interference from a high-power interference station, causing the communication link to be interrupted or degraded beyond a predetermined threshold, and the remote dual-beam user terminal switches the primary channel, the central station / regional station receives and detects that the user service data transmission channel has switched, and then synchronously switches the user service data transmission signal to the channel that matches the received signal;

[0014] Step 5: Continue to maintain the communication status until the communication channel is switched in step 4 when disturbed again. When the user mission is completed, the satellite communication link is dismantled and the communication is terminated.

[0015] Furthermore, in step 2, a judgment is made based on the link status reported by the current main channel. The specific process is: when the carrier lock indication and the decoding lock indication of the original normal communication link are both lost, it means that the communication satellite has been attacked by interference, resulting in communication interruption and link unavailability; when the carrier lock indication and the decoding lock indication are both locked, the bit error rate indication increases beyond a predetermined threshold and the received signal-to-noise ratio decreases beyond a predetermined threshold, it means that the communication satellite has been attacked by interference, resulting in degradation of the communication link capability.

[0016] Furthermore, the selection of multiple communication satellites meets the following requirements:

[0017] ① The satellite beam can cover the user communication station type and meet the requirement that the elevation angle of the dual-beam user terminal antenna beam to the satellite is not less than 15°; ② The satellite beam can cover the communication target of the dual-beam user terminal or can use another communication satellite to cover the communication target via the intersatellite link; ③ The satellite frequency band is consistent with the dual-beam user terminal frequency band and has transponder bandwidth and time slot resources that can meet user communication needs; ④ One of the communication satellites is the main satellite, and the other communication satellites are backup satellites. Both the main satellite and the backup satellite have reserved communication resources for the dual-beam user terminal.

[0018] Furthermore, in step 1, the standby channel periodically polls and detects between multiple standby satellites to obtain channel status, including the following steps:

[0019] Step 1: The dual-beam user terminal uses a backup channel to send a detection signal via a backup satellite;

[0020] Step 2: The central station / regional station receives the detection signal from the remote dual-beam user terminal and estimates the received signal-to-noise ratio and received bit error rate parameters;

[0021] Step 3: The central station / regional station uses the corresponding same backup satellite to send a detection response signal, and carries and sends the locally estimated receive signal-to-noise ratio and receive bit error rate parameters along with the detection response signal;

[0022] Step 4: The remote dual-beam user terminal uses the backup channel to receive the detection response signal from the central station / regional station, estimates the received signal-to-noise ratio and received bit error rate parameters; and simultaneously parses the received signal-to-noise ratio and received bit error rate parameters sent by the central station / regional station;

[0023] Step 5: The standby channel of the remote dual-beam user terminal records the received signal-to-noise ratio and received bit error rate parameters of both ends when using the standby satellite to detect and handshake with the central station / regional station, and reports the parameters to the main control unit;

[0024] Step 6: After completing a detection handshake, the dual-beam user terminal uses the backup channel to adjust the alignment to another backup satellite and repeats steps 1 to 5 until all backup satellites are trained and detected.

[0025] Furthermore, in step 2, the main control unit divides multiple channels into three states: standby, emergency and emergency according to channel quality. When the receiving bit error rate meets the mission requirements, the channel states are sorted according to the receiving signal-to-noise ratio; a communication satellite in the standby state is preferentially selected as a standby satellite, and when a communication satellite in the standby state is interrupted by interference, a communication satellite in the emergency state is selected as a standby satellite; when a communication satellite in the emergency state is interrupted by interference, a communication satellite in the emergency state is selected as a standby satellite.

[0026] The advantages of the present invention are:

[0027] 1. High resilience of the communication system. The method proposed in the present invention prepares multiple communication satellite resources for key users. From the basic process of prior reconnaissance before implementing interference, it is difficult to conduct simultaneous reconnaissance and coordinated interference of multiple satellites, and there is currently no public report on this aspect. Therefore, the present invention can provide users with high-resilience communication guarantee capabilities.

[0028] 2. Strong anti-interference capability in communication. The method proposed in the present invention can quickly switch to the backup link after the interfered link is interrupted or the link is degraded to a predetermined threshold. On the basis of the conventional anti-interference means of the original signal layer (frequency hopping or spread spectrum, error correction coding, etc.), a new method of dealing with interference sources with multiple satellites and multiple links is added. The speed of switching interference targets is much faster than that of a single interference station, avoiding interference attacks from opponents, and providing users with anti-interference communication guarantee capabilities, solving the problem of satellite communication network paralysis caused by the failure of a single conventional transparent forwarding communication satellite to block interference attacks.

[0029] 3. The time from interruption to restoration of communication is short. The present invention proposes a method for communication guarantee based on dual-beam user terminals using multiple satellites. The main link and the backup link work simultaneously. The signal switching time is in the nanosecond level and the service recovery time is in the millisecond level, which is compared with the minute level of satellite switching processing of traditional single-beam user terminals (if a resource coordination link is added, the switching time is in the hour level). The time from interruption to restoration of communication is short, and the real-time guarantee for user communication is high.

[0030] 4. Low difficulty in engineering implementation. The dual-beam user terminal proposed in the present invention is based on the mature and common single-beam user terminal. It is easier to expand and improve by adding channel transmission, antenna radio frequency and other processing channels. The R&D cost is relatively low and the engineering implementation technology is less difficult. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of an application scenario of the present invention.

[0032] Figure 2 This is a functional composition diagram of the dual-beam user terminal of the present invention.

[0033] Figure 3 It is a flow chart of the channel quality timing polling detection of the present invention. DETAILED DESCRIPTION

[0034] The following is combined with Figure 1 to Figure 3 It should be noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0035] Figure 1 The figure shows a schematic diagram of the application scenario of the present invention, in which a number of communication satellites are allocated for mission support for a user communication station type planning using a dual-beam user terminal. Figure 1 The main link of China Communications Satellite 2 communicates with the central station / regional station, and the backup beam of the dual-beam user terminal polls and detects the communication link status between backup satellites. When the main link is attacked by a high-power interference station, resulting in the interruption or degradation of the main link communication exceeding the predetermined threshold, the user service data is automatically switched to the backup link for transmission, and the original main beam is switched to the backup beam, and the link status continues to be polled between the multiple assigned satellites. Because the two beams are in working state at the same time, the switching speed is very fast (the service recovery time is in the millisecond level). Because this communication method is configured with multiple communication satellites and uses a newly designed dual-beam user terminal, the system communication guarantee capability is highly resilient and has strong anti-interference ability.

[0036] Figure 2 The figure shows the functional composition diagram of the dual-beam user terminal of the present invention. Compared with the conventional single-beam user terminal, in addition to the service access and processing unit and the main control unit, the design uses two sets of channel processing and antenna radio frequency units. The antenna radio frequency unit and channel processing unit that process one beam are called a channel. Therefore, the dual-beam user terminal can use two communication satellites in different orbits for communication at the same time. Figure 2 The two channels in the system form a master and backup relationship, which is a real-time online hot backup. Its outstanding advantage is the fast switching response speed.

[0037] The present invention describes a high-toughness anti-interference satellite communication method based on a dual-beam user terminal and multiple satellites. It is assumed that three communication satellites that can simultaneously cover the user's use location are planned and allocated for communication guarantee. The three communication satellites are respectively recorded as Satellite 1, Satellite 2 and Satellite 3. The elevation angle of the user station communication beam to the three satellites is not less than 15°. The three satellite beams can cover the user's communication target, such as the central station / regional station. The three satellites are allocated with communication resources such as frequency, time slot and power that can be used by the user. However, only one of the communication satellites is used as the main satellite at the same time, and the remaining communication satellites are used as backup satellites. The communication task requires that the channel bit error rate is better than 1E-7. The user communication station type is configured with a dual-beam user terminal that can simultaneously transmit and receive satellite beams in two different directions. The central station / regional station is configured with multiple sets of antenna radio frequency units and channel processing units and a set of service access and processing units that can simultaneously transmit and receive three communication satellites. The specific implementation method is given as follows:

[0038] The processing process on the dual-beam user terminal side is:

[0039] Step 1: The dual-beam user terminal uses the current main channel as channel A, uses satellite 2 as the main satellite, establishes a main communication link with the central station / regional station through the main satellite, and performs two-way communication with the central station / regional station through the internal service access and processing unit and the current main channel. During the communication process, the current main channel reports the link status to the main control unit; at the same time, satellite 1 and satellite 3 are used as backup satellites, and the dual-beam user terminal uses the backup channel to establish a backup communication link with the central station / regional station through the backup satellite. The backup channel periodically polls and detects between satellite 1 and satellite 3 to obtain the channel status, and reports the obtained channel status to the main control unit; wherein the link status includes carrier lock indication, decoding lock indication, bit error rate indication and receiving signal-to-noise ratio indication;

[0040] Step 2: The main control unit makes a judgment based on the link status reported by the current main channel. When it is judged that satellite 2 is interfered by a high-power interference station, resulting in the interruption or degradation of the communication link exceeding a predetermined threshold, the control service access and processing unit switches the user service data from the current main channel to the backup channel. At the same time, according to the channel status reported by the backup channel, satellite 1 is selected as the main satellite, and the backup channel is used as the current main channel.

[0041] The processing process on the central station / regional station side is:

[0042] Step 3: The three antenna radio frequency units and channel processing units in the central station / regional station simultaneously receive the wireless signals from satellite 1, satellite 2 and satellite 3. The service access and processing unit in the central station / regional station detects the user service data, selects the main channel and sends the service data to the dual-beam user terminal side via the main satellite 2;

[0043] Step 4: When the primary satellite 2 is attacked by interference from a high-power interference station, causing the communication link to be interrupted or degraded beyond a predetermined threshold, and the remote dual-beam user terminal switches the primary channel, the central station / regional station receives and detects that the user service data transmission channel has been switched, and then synchronously switches the user service data transmission signal to the channel that matches the received signal;

[0044] Step 5: Continue to maintain the communication status until the communication channel is switched in step 4 when disturbed again. When the user mission is completed, the satellite communication link is dismantled and the communication is terminated.

[0045] In step 2, the link status reported by the current active channel is judged, and the specific process is as follows:

[0046] When the carrier lock indication and the decoding lock indication of the original normal communication link are both lost, it means that the communication satellite has been attacked by interference, resulting in communication interruption and link unavailability; when the carrier lock indication and the decoding lock indication are both locked, the bit error rate indication increases beyond the preset threshold and the received signal-to-noise ratio decreases beyond the preset threshold, it means that the communication satellite has been attacked by interference, resulting in degradation of the communication link capability.

[0047] like Figure 3 As shown, a specific implementation method of the central station / regional station cooperating with the remote dual-beam user terminal to complete the channel quality timing polling detection to obtain the channel status is given as follows:

[0048] Step 1: The dual-beam user terminal uses channel B to send a detection signal to the backup satellite 1;

[0049] Step 2: The central station / regional station receives the detection signal from the backup satellite 1, and estimates the received signal-to-noise ratio and the received bit error rate parameters. Assume that the received signal-to-noise ratio is 10 dB and the received bit error rate parameter is 1.5E-8.

[0050] Step 3: The central station / regional station sends a detection response signal via satellite 1, and the detection response signal carries the locally estimated received signal-to-noise ratio (10 dB) and received bit error rate parameter (1.5E-8);

[0051] Step 4: The remote dual-beam user terminal receives the detection response signal from the central station / regional station, and estimates the received signal-to-noise ratio and received bit error rate parameters based on it. Assuming that the received signal-to-noise ratio is 8dB, the received bit error rate parameter is 3.3E-8; synchronously parse the received signal-to-noise ratio (10dB) and received bit error rate parameter (1.5E-8) sent by the central station / regional station, and report the received signal-to-noise ratio and received bit error rate parameters of both ends to the main control unit;

[0052] Step 5: After completing a detection handshake, the dual-beam user terminal adjusts the backup beam to align with satellite 3. The detection process is the same as steps 1 to 4. Assuming that when using satellite 3 for detection polling, the central station / regional station receiving signal-to-noise ratio is 7dB, the receiving bit error rate parameter is 6.5E-8, and the dual-beam user terminal receiving signal-to-noise ratio is 5dB, and the receiving bit error rate parameter is 8.2E-8.

[0053] The main control unit divides multiple channels into standby, emergency and emergency states according to the current channel quality (link status reported by the standby channel). In this embodiment, after completing a polling detection of the quality of all planned standby communication satellite channels, the receiving bit error rates of satellite 1 and satellite 3 meet the mission requirements (better than 1E-7), and the receiving signal-to-noise ratio of the satellite 1 link is higher than that of the satellite 3 link. Therefore, the satellite 1 link can be marked as "standby" and the satellite 3 link can be marked as "emergency". When the main satellite 2 link is disturbed and interrupted, the satellite 1 "standby" link is used first. When the satellite 1 "standby" link is disturbed and interrupted, it is switched to the satellite 3 "emergency" link.

[0054] In the embodiment, the process from normal communication to interruption due to interference, and then from interruption due to interference to restoration of communication when using the dual-beam user terminal proposed by the present invention to communicate with multiple satellites is intuitively demonstrated, demonstrating the high system resilience and strong anti-interference ability of the method. In actual use, when more satellite resources are invested, the system can obtain higher resilience and anti-interference ability. When multiple user stations are used at the same time, the backup links except the main link can be used as resource pools for anti-interference backup protection of multiple user stations at the same time.

[0055] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any equivalent replacement or change made by a person skilled in the art based on the technical solution and inventive concept of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-resilience anti-interference satellite communication method based on dual-beam user terminals and multiple satellites, characterized in that: Dual-beam user terminals based on user communication stations, multiple communication satellites, and central / regional stations; The dual-beam user terminal of the user communication station type is configured with two antenna radio frequency units for simultaneously transmitting and receiving beams in different directions, two channel processing units for simultaneously processing beams, a service access and processing unit, and a main control unit. The antenna radio frequency unit and the channel processing unit for processing one beam are called a channel. The dual-beam user terminal initially selects one channel as the current main channel and the other channel as the backup channel. The multiple communication satellites are all geosynchronous orbit communication satellites. Initially, one communication satellite is selected as the main satellite and the rest are backup satellites. The central station / regional station is configured with multiple sets of antenna radio frequency units and channel processing units, and one set of service access and processing units. The processing process on the dual-beam user terminal side is: Step 1: The dual-beam user terminal uses the current main channel to establish a main communication link with the central station / regional station through the main satellite, and performs two-way communication with the central station / regional station through the internal service access and processing unit and the current main channel. During the communication process, the current main channel reports the link status to the main control unit; at the same time, the dual-beam user terminal uses the backup channel to establish a backup communication link with the central station / regional station through the backup satellite. The backup channel periodically polls and detects between multiple different backup satellites to obtain the channel status, and reports the obtained channel status to the main control unit; wherein the link status includes carrier lock indication, decoding lock indication, bit error rate indication and receiving signal-to-noise ratio indication; Step 2: The main control unit makes a judgment based on the link status reported by the current main channel. When it is judged that the main satellite is interfered by a high-power interference station, resulting in the interruption or degradation of the communication link exceeding a predetermined threshold, the control service access and processing unit switches the user service data from the current main channel to the backup channel, and selects a backup satellite as the main satellite according to the channel status reported by the backup channel, and uses the backup channel as the current main channel; The processing process on the central station / regional station side is: Step 3: Multiple antenna radio frequency units and channel processing units in the central station / regional station simultaneously receive wireless signals from multiple communication satellites. The service access and processing unit in the central station / regional station detects user service data, selects the primary channel, and sends the service data to the dual-beam user terminal side via the primary satellite; Step 4: When the primary satellite is attacked by interference from a high-power interference station, causing the communication link to be interrupted or degraded beyond a predetermined threshold, and the remote dual-beam user terminal switches the primary channel, the central station / regional station receives and detects that the user service data transmission channel has switched, and then synchronously switches the user service data transmission signal to the channel that matches the received signal; Step 5: Continue to maintain the communication status until the communication channel is switched in step 4 when disturbed again. When the user mission is completed, the satellite communication link is dismantled and the communication is terminated.

2. According to claim 1, a high-resilience anti-interference satellite communication method based on dual-beam user terminals and multiple satellites is characterized in that: In step 2, the link status reported by the current active channel is judged. The specific process is as follows: When the carrier lock indication and the decoding lock indication of the original normal communication link are both lost, it means that the communication satellite has been attacked by interference, resulting in communication interruption and link unavailability; when the carrier lock indication and the decoding lock indication are both locked, the bit error rate indication increases beyond the preset threshold and the received signal-to-noise ratio decreases beyond the preset threshold, it means that the communication satellite has been attacked by interference, resulting in degradation of the communication link capability.

3. According to claim 1, a high-resilience anti-interference satellite communication method based on dual-beam user terminals and multiple satellites is characterized in that: The selection of multiple communication satellites meets the following requirements: ① The satellite beam can cover the user communication station type and meet the requirement that the elevation angle of the dual-beam user terminal antenna beam to the satellite is not less than 15°; ② The satellite beam can cover the communication target of the dual-beam user terminal or can use another communication satellite to cover the communication target via the intersatellite link; ③ The satellite frequency band is consistent with the dual-beam user terminal frequency band and has transponder bandwidth and time slot resources that can meet user communication needs; ④ One of the communication satellites is the main satellite, and the other communication satellites are backup satellites. Both the main satellite and the backup satellite have reserved communication resources for the dual-beam user terminal.

4. According to claim 1, a high-resilience anti-interference satellite communication method based on dual-beam user terminals and multiple satellites is characterized in that: In step 1, the standby channel periodically polls and detects between multiple standby satellites to obtain channel status, including the following steps: Step 1: The dual-beam user terminal uses a backup channel to send a detection signal via a backup satellite; Step 2: The central station / regional station receives the detection signal from the remote dual-beam user terminal and estimates the received signal-to-noise ratio and received bit error rate parameters; Step 3: The central station / regional station uses the corresponding same backup satellite to send a detection response signal, and carries and sends the locally estimated receive signal-to-noise ratio and receive bit error rate parameters along with the detection response signal; Step 4: The remote dual-beam user terminal uses the backup channel to receive the detection response signal from the central station / regional station, estimates the received signal-to-noise ratio and received bit error rate parameters; and simultaneously parses the received signal-to-noise ratio and received bit error rate parameters sent by the central station / regional station; Step 5: The standby channel of the remote dual-beam user terminal records the received signal-to-noise ratio and received bit error rate parameters of both ends when using the standby satellite to detect and handshake with the central station / regional station, and reports the parameters to the main control unit; Step 6: After completing a detection handshake, the dual-beam user terminal uses the backup channel to adjust the alignment to another backup satellite and repeats steps 1 to 5 until all backup satellites are trained and detected.

5. According to claim 4, a high-resilience anti-interference satellite communication method based on dual-beam user terminals and multiple satellites is characterized in that: In step 2, the main control unit divides multiple channels into three states: standby, emergency and emergency according to the channel quality. When the receiving bit error rate meets the mission requirements, the channel states are sorted according to the receiving signal-to-noise ratio; the communication satellite in the standby state is preferentially selected as the standby satellite, and when the communication satellite in the standby state is interrupted by interference, the communication satellite in the emergency state is selected as the standby satellite; when the communication satellite in the emergency state is interrupted by interference, the communication satellite in the emergency state is selected as the standby satellite.

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