A method and system for generating and broadcasting three-dimensional sub-meter level integrity messages

Abstract

This invention discloses a method and system for generating and broadcasting three-dimensional sub-meter-level integrity messages, addressing the technical bottleneck of the existing ADS-B standard, which only supports a maximum protection level of 7.5 meters and lacks vertical integrity characterization. The method acquires the meter-level and sub-meter-level horizontal protection level (HPL) and vertical protection level (VPL) of the aircraft in real time, mapping them to horizontal (HU-NIC) and vertical (VU-NIC) extended integrity codes. Subsequently, the two sets of codes are combined and written into the reserved data bits of the 1090ES ADS-B test message or status message to generate and broadcast the extended message. The receiving end extracts the reserved bits to decipher the high-precision protection level, constructing a three-dimensional spatial safety envelope. This invention achieves three-dimensional sub-meter-level safety boundary broadcasting and adaptive degradation monitoring of urban low-altitude high-density aircraft without interfering with the existing civil aviation surveillance system.

Description

Technical Field

[0001] This invention belongs to the cross-technical fields of aviation communication, navigation and surveillance (CNS) and low-altitude intelligent traffic management, and in particular relates to a method and system for generating and broadcasting three-dimensional sub-meter level integrity messages. Background Technology

[0002] With the rapid development of the "low-altitude economy," urban air mobility (UAM), electric vertical takeoff and landing (eVTOL) aircraft, and high-density drone logistics delivery are becoming increasingly common. Unlike traditional open high-altitude airspace, low-altitude aircraft often need to navigate through complex electromagnetic and spatial environments such as densely built-up "urban canyons." In these areas, satellite navigation signals are highly susceptible to physical obstruction and multipath interference, leading to unpredictable fluctuations in the accuracy of airborne positioning systems. To ensure flight safety and high-density collision avoidance at extremely close ranges, high-precision position coordinates alone are insufficient to support safety isolation; the monitoring system needs to acquire and broadcast the statistical boundary of the current position error in real time, i.e., the Protection Level (PL).

[0003] In current airborne surveillance systems, Automatic Dependent Surveillance-Broadcast (ADS-B) is the core airborne data link technology. Existing minimum performance standards for 1090MHz Extended Discontinuous Oscillation (1090ES) ADS-B operation (such as RTCA DO-260B) primarily characterize the aircraft's protection radius (Rc) through Navigation Integrity Category (NIC). However, existing standards have significant technical limitations in addressing the requirements of low-altitude, high-precision operations:

[0004] First, the quantization accuracy is severely insufficient. In the existing DO-260B standard, the highest level of NIC is defined as NIC 11 (corresponding to a protection radius Rc < 7.5 meters). This is sufficient for high-altitude commercial airliners that mainly rely on barometric altimeters for vertical spacing and whose horizontal safety separations are often several kilometers. However, for low-altitude aircraft that need to "fly close to the edge" in the complex urban space and require collision avoidance safety separations accurate to the meter or even sub-meter level, the maximum protection level resolution of 7.5 meters is far from meeting the needs of fine-grained spacing control and dynamic safety envelope construction.

[0005] Secondly, there is a lack of a refined broadcasting mechanism for the Vertical Protection Level (VPL). Current standards primarily use the NIC to implicitly represent the Horizontal Protection Level (HPL), while the representation of vertical integrity is extremely weak. In low-altitude three-dimensional transportation networks, especially during eVTOL takeoff, landing, and multi-level crossing operations, vertical collision avoidance is just as important as horizontal collision avoidance.

[0006] Finally, there is a lack of backward-compatible high-precision broadcast extension schemes. Directly modifying the core bit definition of existing ADS-B standard messages to improve NIC accuracy would cause existing civil air traffic control (ATC) radar systems to report errors or experience logical confusion due to their inability to recognize the messages. Existing technology lacks a smooth evolution mechanism for message extension.

[0007] In summary, the industry urgently needs a communication protocol and processing method that can overcome the limitation of the DO-260B standard's maximum 7.5-meter protection level without interfering with the existing civil aviation ADS-B surveillance system, and broadcast three-dimensional (horizontal and vertical) sub-meter protection level parameters to the outside world through standard-compatible extended messages. Summary of the Invention

[0008] In view of this, the present invention aims to overcome the shortcomings of the prior art by proposing a three-dimensional sub-meter level integrity message generation and broadcasting method and system. Addressing the technical problems of the existing 1090ES ADS-B (DO-260B) standard, which can only characterize a maximum protection level of 7.5 meters (NIC 11), lacks an independent vertical integrity characterization mechanism, and causes compatibility failures in existing air traffic control systems due to direct modification of core standard messages, this invention cleverly utilizes reserved data bits in test or status messages of the standard protocol for encoding and transmission by customizing three-dimensional extended navigation integrity categories (HU-NIC and VU-NIC). The aim is to provide a high-precision, backward-compatible three-dimensional sub-meter level safety boundary broadcasting protocol for urban low-altitude aircraft (such as UAM, eVTOL, etc.) without interfering with the existing civil aviation surveillance system.

[0009] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0010] In a first aspect, the present invention provides a method for generating and broadcasting three-dimensional sub-meter level integrity messages, comprising the following steps:

[0011] Step 1: Real-time acquisition of high-precision positioning integrity parameters of the aircraft, including horizontal protection level (HPL) and vertical protection level (VPL), and the numerical accuracy of both HPL and VPL covers the sub-meter range.

[0012] Step 2: Based on the preset high-precision integrity mapping rules, the values ​​of the horizontal protection level HPL are converted into the corresponding horizontal extended integrity category HU-NIC code, and the values ​​of the vertical protection level VPL are converted into the corresponding vertical extended integrity category VU-NIC code; the preset high-precision integrity mapping rules are used to perform sub-meter level quantization and classification of the protection radius less than 7.5 meters in three-dimensional space;

[0013] Step 3: Combine and encode the generated HU-NIC code and VU-NIC code, and write them together into the reserved data bits of the 1090ESADS-B message data extension field to generate an extended ADS-B message containing three-dimensional integrity boundaries;

[0014] Step 4: Broadcast the extended ADS-B message to the outside world through the airborne ADS-B transmitter so that the receiving end can synchronously parse the sub-meter level horizontal protection level (HPL) and vertical protection level (VPL) of the aircraft and construct a three-dimensional spatial security envelope accordingly.

[0015] Furthermore, in step 2, the preset high-precision integrity mapping rules specifically include:

[0016] The protection level range between 0 and 7.5 meters is divided into multiple sub-meter level sub-ranges, and each sub-range is assigned a unique binary HU-NIC code and VU-NIC code.

[0017] The sub-meter level sub-intervals include at least the following: protection levels less than 4.0 meters, less than 2.0 meters, less than 1.0 meter, less than 0.5 meters, and less than 0.2 meters;

[0018] The HU-NIC code and VU-NIC code are independently mapped and encoded to support the monitoring of integrity degradation that is asymmetrical in the horizontal and vertical directions.

[0019] Furthermore, one implementation method of step 3 includes:

[0020] Uses a 112-bit ADS-B message format with downlink format DF=17 or DF=18;

[0021] Define bits 33 to 88 of the message as a 56-bit message data extension field;

[0022] Set the type code of bits 1 through 5 of the message data extension field to 23 to identify the test message;

[0023] The 9th to 12th bits of the message data extension field are designated as the high-precision horizontal integrity payload area for writing the HU-NIC code;

[0024] The 13th to 16th bits of the message data extension field are designated as the high-precision vertical integrity load area for writing the VU-NIC code.

[0025] Furthermore, one implementation method of step 3 includes:

[0026] Construct an ADS-B runtime status message with type code 31;

[0027] Extract specific reserved bits that are not allocated by the current DO-260B standard from the extended field of the message data of the running status message, and redefine them as high-precision integrity supplement bits. The high-precision integrity supplement bits are divided into horizontal integrity supplement bits and vertical integrity supplement bits.

[0028] Write the HU-NIC code and VU-NIC code into the corresponding high-precision integrity supplement bits respectively;

[0029] The high-precision integrity supplement bit is concatenated and jointly decoded with the basic NIC parameters in the received recent air position message to jointly calculate the sub-meter level horizontal protection level and vertical protection level of the aircraft.

[0030] Furthermore, in step 4, the extended ADS-B message is broadcast externally via an airborne ADS-B transmitter using a 1090MHz radio frequency signal.

[0031] Furthermore, the method also includes an adaptive broadcast switching step based on a protection level threshold:

[0032] Real-time monitoring of the values ​​of the horizontal protection level HPL and the vertical protection level VPL;

[0033] When the horizontal protection level (HPL) or vertical protection level (VPL) is greater than or equal to the 7.5-meter threshold, the corresponding integrity category code is stopped from being written to the reserved data bits, and the system reverts to the standard DO-260B protocol mechanism to generate and broadcast a regular ADS-B message containing standard NIC parameters.

[0034] When both the horizontal protection level (HPL) and the vertical protection level (VPL) are less than the 7.5-meter threshold, steps 2 and 3 are automatically triggered to generate and broadcast an extended ADS-B message containing HU-NIC and VU-NIC codes.

[0035] Furthermore, step 4 includes:

[0036] The receiver receives ADS-B messages in the space radio frequency link;

[0037] Extract the first 5 bits of the type code from the extended field of the ADS-B message data and determine the message type;

[0038] When it is determined that the received message is an extended ADS-B message containing the horizontal extended integrity category HU-NIC code and the vertical extended integrity category VU-NIC code, the binary HU-NIC code and VU-NIC code in the corresponding reserved data bits are extracted;

[0039] Based on the preset high-precision integrity mapping rules, the sub-meter level horizontal protection level (HPL) and vertical protection level (VPL) values ​​of the aircraft are obtained by reverse lookup table.

[0040] Secondly, the present invention provides a three-dimensional sub-meter level integrity message generation and broadcasting system, comprising:

[0041] Airborne subsystem: includes a completeness parameter acquisition module, a message mapping and encoding module, and an ADS-B transmission module;

[0042] Ground surveillance subsystem: includes radio frequency receiving module, type identification and payload extraction module, protection level inverse kinematics module and low-altitude traffic situation processing console;

[0043] The integrity parameter acquisition module is used to acquire the high-precision positioning integrity parameters of the aircraft in real time, including the horizontal protection level (HPL) and the vertical protection level (VPL).

[0044] The message mapping and encoding module is connected to the integrity parameter acquisition module, and is used to convert the horizontal protection level (HPL) into the corresponding horizontal extended integrity category (HU-NIC) code, convert the vertical protection level (VPL) into the corresponding vertical extended integrity category (VU-NIC) code, and write the HU-NIC code and VU-NIC code together into the reserved data bits of the 1090ESADS-B message data extension field to generate an extended ADS-B message; the ADS-B transmission module is connected to the message mapping and encoding module, and is used to modulate the extended ADS-B message into a 1090MHz radio frequency signal and broadcast it externally;

[0045] The radio frequency receiving module is used to receive ADS-B messages in the space radio frequency link; the type identification and payload extraction module is connected to the radio frequency receiving module and is used to extract the type code of the first 5 bits of the extended field of the ADS-B message data, and when it is determined to be an extended ADS-B message, extract the binary HU-NIC code and VU-NIC code in the corresponding reserved data bits; the protection level inverse solution module is connected to the type identification and payload extraction module and is used to reverse look up the table based on the preset high-precision integrity mapping rules to obtain the sub-meter level horizontal protection level (HPL) and vertical protection level (VPL) values ​​of the aircraft; the low-altitude traffic situation processing console is connected to the protection level inverse solution module and is used to construct a three-dimensional space safety envelope based on the parsed sub-meter level horizontal protection level (HPL) and vertical protection level (VPL) values.

[0046] Compared with existing technologies, the three-dimensional sub-meter level integrity message generation and broadcasting method and system described in this invention has the following advantages:

[0047] This invention completely breaks the limitation of the existing DO-260B standard, which can only characterize a protection level of up to 7.5 meters (NIC 11), and smoothly extends the quantization accuracy to the sub-meter range of 4 meters, 2 meters and even 0.2 meters. The innovative introduction of the independent dual encoding mechanism for horizontal and vertical (HPL / VPL) is in line with the physical reality of the asymmetry between vertical and horizontal multipath interference in urban low-altitude environments.

[0048] This invention cleverly utilizes the legally reserved data bits in test or status messages in standard protocols for expansion. Traditional civil air traffic control radars automatically discard or treat such messages as undefined when they are received, thus achieving "physical co-frequency and logical isolation" between the low-altitude fine-grained surveillance network and the large air traffic control network.

[0049] The 7.5-meter threshold switching logic designed in this invention enables the airborne communication system to intelligently determine the signal environment. In open high altitudes (error > 7.5 meters), it degrades to a standard message, while in complex low altitudes (error < 7.5 meters), it upgrades to a high-precision message, ensuring the continuity of surveillance across the entire airspace. Attached Figure Description

[0050] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0051] Figure 1 This is a schematic flowchart of a method for generating and broadcasting three-dimensional sub-meter level integrity messages, provided by an embodiment of the present invention.

[0052] Figure 2 This is a schematic diagram of the data bit allocation and bitmap redefinition structure of the extended ADS-B message (Type Code=23) provided in an embodiment of the present invention;

[0053] Figure 3 A schematic diagram illustrating a scenario where the receiver constructs a three-dimensional spatial security envelope based on the resolved meter-level / sub-meter-level protection level, as provided in an embodiment of the present invention.

[0054] Figure 4 This is a schematic diagram of a three-dimensional sub-meter level integrity message generation and broadcasting system architecture provided in an embodiment of the present invention. Detailed Implementation

[0055] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0056] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0057] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0058] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0059] Example 1

[0060] like Figure 1 As shown, this invention provides a method for generating and broadcasting three-dimensional sub-meter level integrity messages, mainly applied to the monitoring of high-density aircraft (such as UAM, eVTOL, etc.) in complex electromagnetic and space environments at low altitudes in urban areas. Specifically, it includes the following steps:

[0061] Step 1: Real-time acquisition of high-precision positioning completeness parameters

[0062] The aircraft's onboard navigation calculation unit acquires the current Horizontal Protection Level (HPL) and Vertical Protection Level (VPL) in real time. For example, during flight in a city canyon, due to obstruction from surrounding tall buildings, although the horizontal satellite geometry is acceptable, the vertical visible satellites are few. In this case, the upper bound of the system's high-precision error statistics is: HPL = 0.8 meters, VPL = 1.5 meters. Since both values ​​are less than 7.5 meters, falling into the meter-level and sub-meter-level range, the system triggers the extended ADS-B message generation logic.

[0063] Step 2: Perform U-NIC code conversion based on preset mapping rules

[0064] This embodiment pre-defines a high-precision integrity mapping dictionary that surpasses the DO-260B standard. The protection level range of 0 to 7.5 meters is subdivided into multiple high-precision quantization sub-ranges. The mapping rules for the horizontal extended integrity category (HU-NIC) and the vertical extended integrity category (VU-NIC) in this embodiment are shown in Table 1:

[0065] Table 1

[0066]

[0067] Step 3: Combine encoding and reserved bit writing to generate extended message.

[0068] Combination Figure 2 The message structure shown is used to construct a 112-bit ADS-B message with downlink format DF=17. The first 5 bits (ME 1-5) of the message data extension field (ME field, i.e., bits 33 to 88) are set to 10111 (decimal 23) to identify it as a test message.

[0069] Subsequently, bits 9 to 12 of the ME field are designated as the high-precision horizontal integrity load area and written into the aforementioned HU-NIC code 1011; bits 13 to 16 of the ME field are designated as the high-precision vertical integrity load area and written into the aforementioned VU-NIC code 1010. The remaining reserved bits are padded with zeros or loaded with custom status information according to the rules, and finally a check code is generated to complete the framing.

[0070] Step 4: Broadcast the generated message.

[0071] The airborne ADS-B transmitter modulates the encapsulated 112-bit extended message onto a 1090MHz radio frequency carrier and broadcasts it omnidirectionally to the surrounding airspace and ground stations.

[0072] Combination Figure 3 When the ground-based low-altitude surveillance terminal or nearby aircraft receives the radio frequency signal broadcast in Example 1, the following parsing steps are performed:

[0073] First, the message was demodulated and the first 5 digits of the ME field were extracted. The Type Code=23 was identified, indicating that the message was not an ordinary civil aviation position message, but an extended message carrying high-precision integrity parameters.

[0074] Subsequently, the processor precisely extracts the code 1011 from the 9th to the 12th bits of the ME field and the code 1010 from the 13th to the 16th bits.

[0075] By looking up Table 1 (mapping dictionary) in reverse, it can be deduced that the current upper limit of the horizontal protection level of the target aircraft is 1.0 meter and the upper limit of the vertical protection level is 2.0 meters.

[0076] Finally, centered on the aircraft's three-dimensional coordinates (longitude, latitude, and altitude) parsed from the message or adjacent messages, a dynamic ellipsoidal safety envelope with a horizontal half-axis of 1.0 meter and a vertical half-axis of 2.0 meters is rendered in real time. Once this safety envelope is detected to overlap in three-dimensional space with a preset low-altitude geographic fence (such as the boundary of a high-voltage power line corridor or a no-fly zone) or the safety envelope of another aircraft, a high-priority collision avoidance alarm is immediately triggered.

[0077] To balance system bandwidth and monitoring requirements in different airspaces, this embodiment further incorporates an adaptive broadcast switching mechanism.

[0078] When the aircraft leaves the urban canyon and enters open low- or mid-to-high-altitude airspace, its GNSS positioning signal is good. If, at some moment, due to unknown external interference, the calculated HPL deteriorates to 8.0 meters, then HPL ≥ 7.5 meters, triggering the degradation condition.

[0079] The onboard system immediately ceases broadcasting the U-NIC using Type Code 23 messages and seamlessly switches to the standard DO-260B protocol. This involves generating standard air position messages with Type Codes 9 to 18 and broadcasting the corresponding integrity level (e.g., broadcasting NIC=4, indicating Rc<2.0NM) through the standard NIC parameter fields. This mechanism ensures that the aircraft maintains backward compatibility with the major air traffic control network throughout its all-airspace flight operations.

[0080] Example 2

[0081] like Figure 4 As shown, the present invention provides a system for generating and broadcasting three-dimensional sub-meter level integrity messages, comprising:

[0082] Airborne subsystem: includes a completeness parameter acquisition module, a message mapping and encoding module, and an ADS-B transmission module;

[0083] Ground surveillance subsystem: includes radio frequency receiving module, type identification and payload extraction module, protection level inverse kinematics module and low-altitude traffic situation processing console;

[0084] The integrity parameter acquisition module is used to acquire the high-precision positioning integrity parameters of the aircraft in real time, including the horizontal protection level (HPL) and the vertical protection level (VPL).

[0085] The message mapping and encoding module is connected to the integrity parameter acquisition module, and is used to convert the horizontal protection level (HPL) into the corresponding horizontal extended integrity category (HU-NIC) code, convert the vertical protection level (VPL) into the corresponding vertical extended integrity category (VU-NIC) code, and write the HU-NIC code and VU-NIC code together into the reserved data bits of the 1090ESADS-B message data extension field to generate an extended ADS-B message; the ADS-B transmission module is connected to the message mapping and encoding module, and is used to modulate the extended ADS-B message into a 1090MHz radio frequency signal and broadcast it externally;

[0086] The radio frequency receiving module is used to receive ADS-B messages in the space radio frequency link; the type identification and payload extraction module is connected to the radio frequency receiving module and is used to extract the type code of the first 5 bits of the extended field of the ADS-B message data, and when it is determined to be an extended ADS-B message, extract the binary HU-NIC code and VU-NIC code in the corresponding reserved data bits; the protection level inverse solution module is connected to the type identification and payload extraction module and is used to reverse look up the table based on the preset high-precision integrity mapping rules to obtain the sub-meter level horizontal protection level (HPL) and vertical protection level (VPL) values ​​of the aircraft; the low-altitude traffic situation processing console is connected to the protection level inverse solution module and is used to construct a three-dimensional space safety envelope based on the parsed sub-meter level horizontal protection level (HPL) and vertical protection level (VPL) values.

[0087] Matters not covered in this invention are common knowledge.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for generating and broadcasting three-dimensional sub-meter level integrity messages, characterized in that: Includes the following steps: Step 1: Real-time acquisition of high-precision positioning integrity parameters of the aircraft, including horizontal protection level (HPL) and vertical protection level (VPL), and the numerical accuracy of both HPL and VPL covers the sub-meter range. Step 2: Based on the preset high-precision integrity mapping rules, the values ​​of the horizontal protection level HPL are converted into the corresponding horizontal extended integrity category HU-NIC code, and the values ​​of the vertical protection level VPL are converted into the corresponding vertical extended integrity category VU-NIC code; the preset high-precision integrity mapping rules are used to perform sub-meter level quantization and classification of the protection radius less than 7.5 meters in three-dimensional space; Step 3: Combine and encode the generated HU-NIC code and VU-NIC code, and write them together into the reserved data bits of the 1090ES ADS-B message data extension field to generate an extended ADS-B message containing the three-dimensional integrity boundary. Step 4: Broadcast the extended ADS-B message to the outside world through the airborne ADS-B transmitter so that the receiving end can synchronously parse the sub-meter level horizontal protection level (HPL) and vertical protection level (VPL) of the aircraft and construct a three-dimensional spatial security envelope accordingly.

2. The method for generating and broadcasting a three-dimensional sub-meter level integrity message according to claim 1, characterized in that: In step 2, the preset high-precision integrity mapping rules specifically include: The protection level range between 0 and 7.5 meters is divided into multiple sub-meter level sub-ranges, and each sub-range is assigned a unique binary HU-NIC code and VU-NIC code. The sub-meter level sub-intervals include at least the following: protection levels less than 4.0 meters, less than 2.0 meters, less than 1.0 meter, less than 0.5 meters, and less than 0.2 meters; The HU-NIC code and VU-NIC code are independently mapped and encoded to support the monitoring of integrity degradation that is asymmetrical in the horizontal and vertical directions.

3. The method for generating and broadcasting three-dimensional sub-meter level integrity messages according to claim 1, characterized in that: One method for implementing step 3 includes: Uses a 112-bit ADS-B message format with downlink format DF=17 or DF=18; Define bits 33 to 88 of the message as a 56-bit message data extension field; Set the type code of bits 1 through 5 of the message data extension field to 23 to identify the test message; The 9th to 12th bits of the message data extension field are designated as the high-precision horizontal integrity payload area for writing the HU-NIC code; The 13th to 16th bits of the message data extension field are designated as the high-precision vertical integrity load area for writing the VU-NIC code.

4. The method for generating and broadcasting a three-dimensional sub-meter level integrity message according to claim 1, characterized in that: One method for implementing step 3 includes: Construct an ADS-B runtime status message with type code 31; Extract specific reserved bits that are not allocated by the current DO-260B standard from the extended field of the message data of the running status message, and redefine them as high-precision integrity supplement bits. The high-precision integrity supplement bits are divided into horizontal integrity supplement bits and vertical integrity supplement bits. Write the HU-NIC code and VU-NIC code into the corresponding high-precision integrity supplement bits respectively; The high-precision integrity supplement bit is concatenated and jointly decoded with the basic NIC parameters in the received recent air position message to jointly calculate the sub-meter level horizontal protection level and vertical protection level of the aircraft.

5. The method for generating and broadcasting three-dimensional sub-meter level integrity messages according to claim 1, characterized in that: In step 4, the extended ADS-B message is broadcast to the outside world via an airborne ADS-B transmitter using a 1090MHz radio frequency signal.

6. The method for generating and broadcasting three-dimensional sub-meter level integrity messages according to claim 1, characterized in that: The method also includes an adaptive broadcast switching step based on a protection level threshold: Real-time monitoring of the values ​​of the horizontal protection level HPL and the vertical protection level VPL; When the horizontal protection level (HPL) or vertical protection level (VPL) is greater than or equal to the 7.5-meter threshold, the corresponding integrity category code is stopped from being written to the reserved data bits, and the system reverts to the standard DO-260B protocol mechanism to generate and broadcast a regular ADS-B message containing standard NIC parameters. When both the horizontal protection level (HPL) and the vertical protection level (VPL) are less than the 7.5-meter threshold, steps 2 and 3 are automatically triggered to generate and broadcast an extended ADS-B message containing HU-NIC and VU-NIC codes.

7. The method for generating and broadcasting a three-dimensional sub-meter level integrity message according to claim 1, characterized in that: Step 4 includes: The receiver receives ADS-B messages in the space radio frequency link; Extract the first 5 bits of the type code from the extended field of the ADS-B message data and determine the message type; When it is determined that the received message is an extended ADS-B message containing the horizontal extended integrity category HU-NIC code and the vertical extended integrity category VU-NIC code, the binary HU-NIC code and VU-NIC code in the corresponding reserved data bits are extracted; Based on the preset high-precision integrity mapping rules, the sub-meter level horizontal protection level (HPL) and vertical protection level (VPL) values ​​of the aircraft are obtained by reverse lookup table.

8. A system for executing the three-dimensional sub-meter integrity message generation and broadcasting method according to any one of claims 1-7, characterized in that: include: Airborne subsystem: includes a completeness parameter acquisition module, a message mapping and encoding module, and an ADS-B transmission module; Ground surveillance subsystem: includes radio frequency receiving module, type identification and payload extraction module, protection level inverse kinematics module and low-altitude traffic situation processing console; The integrity parameter acquisition module is used to acquire the high-precision positioning integrity parameters of the aircraft in real time, including the horizontal protection level (HPL) and the vertical protection level (VPL). The message mapping and encoding module is connected to the integrity parameter acquisition module, and is used to convert the horizontal protection level (HPL) into the corresponding horizontal extended integrity category (HU-NIC) code, convert the vertical protection level (VPL) into the corresponding vertical extended integrity category (VU-NIC) code, and write the HU-NIC code and VU-NIC code together into the reserved data bits of the 1090ESADS-B message data extension field to generate an extended ADS-B message; the ADS-B transmission module is connected to the message mapping and encoding module, and is used to modulate the extended ADS-B message into a 1090MHz radio frequency signal and broadcast it externally; The radio frequency receiving module is used to receive ADS-B messages in the space radio frequency link; the type identification and payload extraction module is connected to the radio frequency receiving module and is used to extract the type code of the first 5 bits of the extended field of the ADS-B message data, and when it is determined to be an extended ADS-B message, extract the binary HU-NIC code and VU-NIC code in the corresponding reserved data bits; the protection level inverse solution module is connected to the type identification and payload extraction module and is used to reverse look up the table based on the preset high-precision integrity mapping rules to obtain the sub-meter level horizontal protection level (HPL) and vertical protection level (VPL) values ​​of the aircraft; the low-altitude traffic situation processing console is connected to the protection level inverse solution module and is used to construct a three-dimensional space safety envelope based on the parsed sub-meter level horizontal protection level (HPL) and vertical protection level (VPL) values.

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