A method for UAV access capacity in the 1090 MHz band based on variable channel and mobility prediction

Abstract

This invention discloses a method for UAV access capacity in the 1090 MHz band based on variable channels and mobility prediction. It introduces S-mode and A / C-mode messages in the real-world 1090 MHz band; and allows for the setting of corresponding channel propagation models according to different environments. All aircraft are modeled as mobile devices; and the ADS-B message update cycle can be adjusted according to the UAV's speed. Finally, the continuous packet loss situation and corresponding packet loss rate of civil aircraft and UAVs can be obtained. Under the condition of meeting the minimum message update rate of civil aircraft, i.e., maintaining the normal operation of the civil aviation surveillance system, the method analyzes how many UAVs equipped with ADS-B OUT devices can be added to this frequency band.

Description

Technical Field

[0001] This invention belongs to the field of low-altitude intelligent network technology, specifically, it relates to a method for improving the access capacity of UAVs in the 1090 MHz band based on variable channels and mobility prediction. Background Technology

[0002] Due to their advantages such as small size, high maneuverability, low cost, and convenient deployment, drones are increasingly widely used in both military and civilian fields, including collaborative reconnaissance, precision agriculture, disaster management, and environmental monitoring. During the development of drone technology, it has become increasingly clear that the reliability of a single drone in completing a mission is insufficient, and limitations in its energy, capabilities, and payload make it difficult to accomplish complex tasks. Therefore, multi-drone collaborative operations have become a trend. With the development of technologies such as electronics and communications, drones are trending towards miniaturization, and large-scale drone swarms, represented by swarms, have received widespread attention from industry and academia.

[0003] However, due to the lack of onboard pilots, the flight safety of drones cannot be guaranteed, and they may interfere with the operation of regular civil aircraft; at the same time, they are also detrimental to the air traffic control bureau's management of flight traffic in specific airspaces. How to improve the airspace management of drones and ensure flight safety in controlled areas has become an important issue.

[0004] To acquire aerial situational awareness of unmanned aerial vehicles (UAVs), some UAVs can be equipped with an ADS-B OUT system. ADS-B stands for Automatic Dependent Surveillance-Broadcast, operating in the 1090 MHz band, and can be used to supplement traditional primary and secondary radar surveillance systems. Aircraft equipped with ADS-B OUT can automatically broadcast their own flight-related information to surrounding aircraft, vehicles, and ground stations, including: aircraft position information (POS), aircraft velocity information (VEL), aircraft identification and type information (ID), target status information (TSS), and aircraft operational status information (AOS).

[0005] However, since drones share the 1090 MHz frequency band with civil aircraft, the ADS-B OUT equipment installed on drones will affect the existing civil aviation ADS-B surveillance system. Too many drones accessing this frequency band will cause the collision of data packets in this band to intensify, increasing the interference and packet loss of the civil aviation surveillance system. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for UAV access capacity in the 1090 MHz band based on variable channel and mobility prediction. This method determines the number of UAVs equipped with ADS-B OUT devices that can access the 1090 MHz band while maintaining the normal operation of the civil aviation surveillance system.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for UAV access capacity in the 1090 MHz band based on variable channels and mobility prediction, specifically including the following steps:

[0008] Step 1: Based on the civil aviation aircraft message data collected from different regions, set up S-mode messages and A / C-mode messages as the background message stream for the 1090 MHz band environment;

[0009] Step 2: Set the typical access protocol for civil aircraft and drones accessing the 1090 MHz band to random access, and set the runtime.

[0010] Step 3: Based on the ADS-B message length, use cyclic redundancy coding and set the number of cyclically correctable code elements;

[0011] Step 4: Set the signal transmission power of each aircraft, calculate the propagation loss of each aircraft's message based on the free space line-of-sight propagation loss, and obtain the message success rate by combining the set number of cyclic error-correctable symbols; set a random factor on the aircraft to group the messages.

[0012] Step 5: Various messages propagate in free space. If a message does not collide with other ADS-B messages, nor with the S-mode message or A / C-mode message in step 1, and the error rate is within the allowable range, then the message can be received correctly.

[0013] Step 6: Set up the movement model for each aircraft;

[0014] Step 7: Civil aircraft set the sending end message update cycle according to international standards, and UAVs set the sending end message update cycle according to speed ratio;

[0015] Step 8: Repeat steps 4-7 until the set runtime is reached. The ADS-B ground station will collect statistics on the messages of each aircraft and calculate the continuous packet loss. It will then calculate the message update rate of the ground station for civil aircraft and UAVs. Under the given minimum message update rate for civil aircraft, i.e., to maintain the normal operation of the civil aviation surveillance system, it will calculate the maximum number of UAVs equipped with ADS-B OUT that can be accommodated in a certain airspace.

[0016] Furthermore, step 3 specifically includes the following sub-steps:

[0017] Step 3.1: The ADS-B message length is 112 bits, using (112, 88) cyclic redundancy code. A 24-bit parity check is added after the 88 data bits. The generator polynomial is:

[0018] g(x) = x 24 +x23 +x 22 +x 21 +x 20 +x 19 +x 18 +x 17 +x 15 +x 15 +x 14 +x 13 +x 12 +x 10 +x 3 +1

[0019] Step 3.2: Take the first 88 bits of the 112-bit data as the original code, and perform a modulo-2 operation on the check code m(x) and g(x) corresponding to the original code to obtain the first check code r(x):

[0020] r(x) = x 24 m(x) mod g(x)

[0021] Step 3.3: The codeword c(x) to be transmitted after concatenating the first check code r(x) with the original code is:

[0022] c(x)=x 24 m(x)+r(x)

[0023] Step 3.4: The received codeword is s(x). After performing a modulo-2 operation on s(x) and g(x), the remainder is R(x). If R(x) is 0, then no transmission error has occurred.

[0024] R(x)=s(x)mod g(x)=c(x)mod g(x)={x 24 m(x)+r(x)}mod g(x)={r(x)+r(x)}mod 2=0;

[0025] If R(x) is not 0, then a transmission error has occurred:

[0026] R(x)=s(x)mod g(x)={c(x)+e(x)}mod g(x)=e(x)mod g(x);

[0027] Step 3.6: Set the number of cyclically correctable code elements m with R(x) = 0 as the target.

[0028] Furthermore, step 4 includes the following sub-steps:

[0029] Step 4.1: N aircraft and n drones are randomly distributed within an airspace of diameter D. Each aircraft is set to a random initial position (X). o Y o Zo ), x o ∈(-D / 2, D / 2), Y o ∈(-D / 2, D / 2), we obtain the distance d from the spacecraft to the ground station d=d o for:

[0030]

[0031] Step 4.2: Based on the distance d between the aircraft and the ground station and the signal transmission power f of each aircraft, the propagation loss of the aircraft messages is calculated:

[0032] Loss = 32.44 + 20lg d + 201gf

[0033] Step 4.3: Based on the propagation loss of the aircraft message, obtain the input signal power of the demodulator S = P + A - Loss, and the Gaussian white noise power N = n0 * B, where P is the transmission power of the civil aircraft ADS-B, A is the receiving sensitivity of the ground station located at the two-dimensional geometric center, n0 is the Gaussian white noise power density, and B is the bandwidth. The demodulator input signal-to-noise ratio r = S / N is obtained, and the M-ary PSK bit error rate is:

[0034]

[0035] Step 4.4: After adding cyclic redundancy check (CR). If (112-m) bits out of the 112 bits are correctly received, the message is considered successfully received. The message success rate P is... S-CRC for:

[0036]

[0037] Where i is the index of the number of cyclic error-correctable code elements;

[0038] Step 4.5: Set a random factor v∈(0~1) in the aircraft. If v≥(1-P) S-CRC If v < (1-P), then record it as a "good message" in the message group; S-CRC If a message is detected as a "bad message" in the packet, it will be recorded as such. When a message is propagated in free space, a collision occurs and packet loss occurs, the ground station will remove the "bad message" from the message statistics.

[0039] Furthermore, in step 4.4, the corresponding fading coefficient ρ is set according to different scenarios to obtain the message success rate P under that scenario. SCRC :

[0040] P ScRC =ρ×P S-CR .

[0041] Furthermore, step 6 includes the following sub-steps:

[0042] Step 6.1: Set the flight speed V of the aircraft. Generate a random heading vector (α, β, γ) for each aircraft, where α∈(-1, 1), β∈(-1, 1), and γ∈(-1, 1). Then, the velocity components V of the aircraft in each direction are... X V Y V Z for:

[0043]

[0044]

[0045]

[0046] Step 6.2: After time f, each time the ground station successfully receives a message, the simulation iteratively updates the position of each aircraft. The updated aircraft positions (X, Y, Z) are:

[0047] X = X o +V X ×T

[0048] Y = Y o +V Y ×T

[0049] Z = Z o +V Z ×f

[0050] The updated distance d between the spacecraft and the ground station is:

[0051]

[0052] Furthermore, the message update cycle for the sending end of the civil aircraft is set as follows:

[0053] The update cycle of civil aircraft air position messages is a random jitter interval of (0.5-δ, 0.5+δ), where δ is the random jitter factor of the air position message;

[0054] The update cycle for civil aircraft identification and type messages is a random jitter interval of (5-ε, 5+ε), where ε is the random jitter factor of the aircraft identification and type messages.

[0055] The update cycle for civil aircraft speed messages is a random jitter interval of (0.5-∈, 0.5+∈), where ∈ is the random jitter factor of the aircraft speed message;

[0056] The update cycle for the target status message of civil aircraft is a random jitter interval of (1.25-μ, 1.25+μ), where μ is the random jitter factor of the target status message;

[0057] The update cycle for civil aviation aircraft operation status messages is a random jitter interval of (2.5-τ, 2.5+τ), where τ is the random jitter factor of the aircraft operation status message.

[0058] Furthermore, the message update period for the sending end of the UAV, set according to the speed ratio, is as follows:

[0059] The drone airborne location message update cycle is

[0060] The update cycle for drone identification and type messages is:

[0061] The drone speed message update cycle is

[0062] The update cycle for UAV target status messages is:

[0063] The drone operation status message update cycle is

[0064] Where ω is the speed ratio of the civil aircraft to the drone.

[0065] Compared with existing technologies, this invention has the following beneficial effects: The analysis method for UAV access capacity in the 1090 MHz band based on variable channels and mobility prediction aims to improve flight safety for UAVs and enhance air traffic control management by acquiring UAV flight status data. It analyzes the impact of UAVs equipped with ADS-B OUT devices on the civil aviation surveillance system in the 1090 MHz band, introducing S-mode and A / C-mode messages in the real-world 1090 MHz band. Furthermore, it allows for setting corresponding channel propagation models based on different environments; all aircraft are modeled as mobile devices; and the ADS-B message update cycle can be adjusted according to the UAV's speed. Finally, it obtains the continuous packet loss situation and corresponding packet loss rate for civil aircraft and UAVs. Under the condition of meeting the minimum message update rate for civil aircraft, i.e., maintaining the normal operation of the civil aviation surveillance system, it analyzes how many UAVs equipped with ADS-B OUT devices can be added to this frequency band. Attached Figure Description

[0066] Figure 1 This is a schematic diagram of the airspace for civil aircraft and unmanned aerial vehicles involved in this invention;

[0067] Figure 2 This is a simulation flowchart of the UAV access capacity method based on variable channel and mobility prediction in the 1090 MHz band according to the present invention. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0069] This invention provides a method for UAV capacity estimation in the 1090 MHz band based on variable channels and mobility prediction, such as... Figure 1 As shown, within an airspace of diameter D, N civil aircraft and n drones are randomly distributed. The ground station is located at the geometric center of the ground corresponding to the airspace. The civil aircraft and drones send five types of ADS-B messages and mode S messages to the ground station, while the drones send five types of ADS-B messages. Both types of aircraft update their position status according to their respective flight speeds. Messages generated by both types of aircraft experience propagation loss in free space, resulting in a decrease in the received signal-to-noise ratio upon reaching the ground station demodulator, thus generating certain bit errors and leading to packet loss. The civil aircraft and drones share the 1090 MHz frequency band. Due to limited frequency resources, various messages will collide in free space, causing collision-induced packet loss. A message can be correctly received by the ground station if it does not collide with messages from other aircraft, nor with mode S or mode A / C messages in the background message stream, and its bit error rate is within the ground station's acceptable reception range. Finally, the ground station will compile statistics on the message reception rate of each civil aircraft and drone, as well as the continuous packet loss of various types of messages.

[0070] like Figure 2 The UAV capacity method based on variable channel and mobility prediction in the 1090 MHz band of this invention specifically includes the following steps:

[0071] Step 1: Based on the civil aviation aircraft message data collected from different regions, set up S-mode messages and A / C-mode messages as background message streams in the 1090 MHz band environment, and participate in the collision of subsequent ADS-B messages propagating in free space, thereby simulating the real 1090 MHz band environment.

[0072] Step 2: Set the typical access protocol for civil aircraft and drones accessing the 1090 MHz band to random access, that is, the link layer protocol adopts the ALOHA protocol, and set the runtime.

[0073] Step 3: Based on the ADS-B message length, employ cyclic redundancy coding (CRCC) and set the number of cyclic error-correctable code elements. CRCC is used to verify the correctness and integrity of the message content during communication. This involves adding a verification data segment after the normal binary data, creating a constraint relationship between the verification data and the original data. Upon receiving the message, verifying the relationship between the original data and the verification data determines whether the original data is correct or complete. This includes the following sub-steps:

[0074] Step 3.1: The ADS-B message length is 112 bits, using (112, 88) cyclic redundancy code. A 24-bit parity check is added after the 88 data bits. The generator polynomial is:

[0075] g(x) = x 24 +x 23 +x 22 +x 21 +x 20 +x 19 +x 18 +x 17 +x 15 +x 15 +x 14 +x 13 +x 12 +x 10 +x 3 +1

[0076] Step 3.2: Take the first 88 bits of the 112-bit data as the original code, and perform a modulo-2 operation on the check code m(x) and g(x) corresponding to the original code to obtain the first check code r(x):

[0077] r(x) = x 24 m(x) mod g(x)

[0078] Step 3.3: The codeword c(x) to be transmitted after concatenating the first check code r(x) with the original code is:

[0079] c(x)=x 24 m(x)+r(x)

[0080] Step 3.4: The received codeword is s(x). After performing a modulo-2 operation on s(x) and g(x), the remainder is R(x). If R(x) is 0, then no transmission error has occurred.

[0081] R(x)=s(x)mod g(x)=c(x)mod g(x)={x 24 m(x)+r(x)}mod g(x)={r(x)+r(x)}mod 2=0;

[0082] If R(x) is not 0, then a transmission error has occurred:

[0083] R(x)=s(x)mod g(x)={c(x)+e(x)}mod g(x)=e(x)mod g(x);

[0084] Step 3.6: With R(x) = 0 as the target, set the number of cyclic error-correctable code elements m so that the message has a certain degree of error correction capability and improves the message success rate.

[0085] Step 4: Set the signal transmission power of each aircraft. Based on the free-space line-of-sight propagation loss, calculate the propagation loss of each aircraft's messages. Combine this with the set number of cyclic error-correctable symbols to obtain the message success rate. Set a random factor on each aircraft to group the messages. This includes the following sub-steps:

[0086] Step 4.1: N aircraft and n drones are randomly distributed within an airspace of diameter D. Each aircraft is set to a random initial position (X). o Y o Z o ), x o ∈(-D / 2, D / 2), Y o ∈(-D / 2, D / 2), since the flight altitude of civil aircraft is between 6 km and 9.6 km, then Z o =Z o1 ∈(6, 9.6). If the drone's flight altitude is limited to within 0.5 kilometers, then Z o =Z o2 ∈(0, 0.5), based on this, the distance d between the spacecraft and the ground station is obtained as d = d o for:

[0087]

[0088] Step 4.2: Based on the distance d between the aircraft and the ground station and the signal transmission power f of each aircraft, the propagation loss of the aircraft messages is calculated:

[0089] Loss = 32.44 + 201g d + 20lgf

[0090] Step 4.3: Based on the propagation loss of the aircraft message, obtain the demodulator's input signal power S = P + A - Loss, and the Gaussian white noise power N = n0 * B, where P is the transmit power of the civil aircraft ADS-B, A is the receiving sensitivity of the ground station located at the two-dimensional geometric center, n0 is the Gaussian white noise power density, and B is the bandwidth. Since the ADS-B system operates at 1090 MHz, this frequency band belongs to the ultra-high frequency band. In the civil aviation system, 962 MHz to 1213 MHz is used for the onboard ranging system, with a channel spacing of 1 MHz. The 1090 MHz band is reserved for the ADS-B system, so the signal bandwidth B = 1 MHz. Therefore, the demodulator input signal-to-noise ratio r = S / N, and the M-ary PSK bit error rate is:

[0091]

[0092] Step 4.4, when M=8, the bit error rate formula is approximately:

[0093]

[0094] The bit error rate of each message is calculated using the above formula. Without cyclic redundancy check (CRC), a message is considered successfully received only if all 112 bits are correctly received. The message success rate P... S for:

[0095] P S =(1-P e ) 112 ;

[0096] With the addition of cyclic redundancy check (CR). If (112-m) bits out of the 112 bits are correctly received, the message is considered successfully received, and the message success rate P... S-CRC for:

[0097]

[0098] Where i is the index of the number of cyclic error-correctable code elements;

[0099] In urban scenarios, the propagation of electromagnetic waves in mobile communication is mainly affected by multipath effects. Additionally, base stations are densely distributed, and electromagnetic waves are amplified after passing through them. In mountainous scenarios, due to the blocking effect of mountains, electromagnetic wave propagation is primarily affected by shadowing effects, and there are fewer base stations in mountainous areas compared to urban areas. In marine scenarios, the propagation distance of electromagnetic waves is limited due to the lack of relay base stations, mainly affected by path loss. Therefore, by setting the corresponding fading coefficient ρ for different scenarios, the message success rate P under those scenarios can be obtained. SCRC =ρ×P S-CRC ,

[0100] Step 4.5: In practice, message reception failure has the following three possibilities:

[0101] (1) A message collision occurred;

[0102] (2) Too many errors were generated in the message;

[0103] (3) The message generates a bit error and then conflicts with the complete message;

[0104] Even if a message contains a bit error, it may still reach the ground station and collide with other normal messages, resulting in packet loss. Therefore, it's not feasible to simply set a random factor in the aircraft to determine if a message has a bit error and discard it directly; similarly, it's not feasible to set a random factor in the ground station to determine if a message has a bit error and discard it directly, as this would compromise fairness for all messages. Considering these factors, this invention sets a random factor v∈(0~1) in the aircraft. If v≥(1-P) S-CRC If v < (1-P), then record it as a "good message" in the message group; S-CRC If a message is detected as a "bad message" in the packet, it will be recorded as such. When a message is propagated in free space, a collision occurs and packet loss occurs, the ground station will remove the "bad message" from the message statistics.

[0105] Step 5: Various messages propagate in free space. If a message does not collide with other ADS-B messages, nor with the S-mode message or A / C-mode message in Step 1, and the error rate is within the allowable range, then the message can be received correctly.

[0106] Step 6, set up the movement model for each aircraft; including the following sub-steps:

[0107] Step 6.1: Set the flight speed V of the aircraft. Generate a random heading vector (α, β, γ) for each aircraft, where α∈(-1, 1), β∈(-1, 1), and γ∈(-1, 1). Then, the velocity components V of the aircraft in each direction are... X V Y V Z for:

[0108]

[0109]

[0110]

[0111] Step 6.2: After time T, each time the ground station successfully receives a message, the simulation iteratively updates the position of each aircraft. The updated aircraft positions (X, Y, Z) are:

[0112] X = X o +VX ×T

[0113] Y = Y o +V Y ×f

[0114] Z = Z o +V Z ×T

[0115] The updated distance d between the spacecraft and the ground station is:

[0116]

[0117] Step 7: Civil aircraft set the sender message update cycle according to international standards, while UAVs set the sender message update cycle according to their speed ratio; specifically,

[0118] An ADS-B message is 112 bits long. Since the ADS-B message header includes an 8-bit control field, the total message length is 120 bits, and the duration is 120 microseconds. There are five main message types in the ADS-B system: air position message, aircraft identification and type message, aircraft speed message, target status message, and aircraft operational status message. To avoid conflicts between different message types, the update interval for each message type is not fixed but uses random jitter. The update interval for civil aviation aircraft messages is as follows: the update interval for civil aviation aircraft air position messages is a random jitter interval of (0.5-δ, 0.5+δ), where δ is the random jitter factor for the air position message.

[0119] The update cycle for civil aircraft identification and type messages is a random jitter interval of (5-ε, 5+ε), where ε is the random jitter factor of the aircraft identification and type messages.

[0120] The update cycle for civil aircraft speed messages is a random jitter interval of (0.5-∈, 0.5+∈), where ∈ is the random jitter factor of the aircraft speed message;

[0121] The update cycle for the target status message of civil aircraft is a random jitter interval of (1.25-μ, 1.25+μ), where μ is the random jitter factor of the target status message;

[0122] The update cycle for civil aviation aircraft operation status messages is a random jitter interval of (2.5-τ, 2.5+τ), where τ is the random jitter factor of the aircraft operation status message.

[0123] Since the flight speed of a drone is less than that of a commercial aircraft, its message update cycle does not need to be set according to the standard for commercial aircraft. This also reduces the frequency band resources occupied by the drone. The message update cycle of the drone is set according to the speed ratio ω between the commercial aircraft speed and the drone speed.

[0124] The message update cycle for the drone's transmitter, set according to the speed ratio, is as follows:

[0125] The drone airborne location message update cycle is

[0126] The update cycle for drone identification and type messages is:

[0127] The drone speed message update cycle is

[0128] The update cycle for UAV target status messages is:

[0129] The drone operation status message update cycle is

[0130] Where ω is the speed ratio of the civil aircraft to the drone.

[0131] Step 8: Repeat steps 4-7 until the set runtime is reached. The ADS-B ground station will statistically analyze the messages from each aircraft and calculate the continuous packet loss. It will then calculate the message update rate of the ground station for civil aircraft and UAVs. Under the given minimum message update rate for civil aircraft, i.e., while maintaining the normal operation of the civil aviation surveillance system, it will calculate the maximum number of UAVs equipped with ADS-B OUT that can be accommodated in a certain airspace, thereby improving the flight safety of UAVs.

[0132] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for UAV access capacity in the 1090 MHz band based on variable channel and mobility prediction, characterized in that, Specifically, the steps include the following: Step 1: Based on the civil aviation aircraft message data collected from different regions, set up S-mode messages and A / C-mode messages as the background message stream for the 1090 MHz band environment; Step 2: Set the typical access protocol for civil aircraft and drones accessing the 1090 MHz band to random access, and set the runtime. Step 3: Based on the ADS-B message length, use cyclic redundancy coding and set the number of cyclically correctable code elements; Step 4: Set the signal transmission power of each aircraft, calculate the propagation loss of each aircraft's message based on the free space line-of-sight propagation loss, and obtain the message success rate by combining the set number of cyclic error-correctable symbols; set a random factor in the aircraft to group the messages. Step 5: Various messages propagate in free space. If a message does not collide with other ADS-B messages, nor with the S-mode message or A / C-mode message in Step 1, and the error rate is within the allowable range, then the message can be received correctly. Step 6: Set up the movement model for each aircraft; Step 7: Civil aircraft set the sending end message update cycle according to international standards, and UAVs set the sending end message update cycle according to speed ratio; Step 8: Repeat steps 4-7 until the set runtime is reached. The ADS-B ground station will collect statistics on the messages of each aircraft and calculate the continuous packet loss. It will then calculate the message update rate of the ground station for civil aircraft and UAVs. Under the given minimum message update rate for civil aircraft, i.e., to maintain the normal operation of the civil aviation surveillance system, it will calculate the maximum number of UAVs equipped with ADS-B OUT that can be accommodated in a certain airspace.

2. The method for UAV access capacity in the 1090 MHz band based on variable channel and mobility prediction according to claim 1, characterized in that, Step 3 specifically includes the following sub-steps: Step 3.1: The ADS-B message length is 112 bits, using (112, 88) cyclic redundancy code. A 24-bit parity check is added after the 88 data bits. The generator polynomial is: g(x) = x 24 + 1 23 + 1 22 + 1 21 + 1 20 + 1 19 + 1 18 + 1 17 + 1 15 + 1 15 + 1 14 + 1 13 + 1 12 + 1 10 + 1 3 + 1 Step 3.2: Take the first 88 bits of the 112-bit data as the original code, and perform a modulo-2 operation on the check code m(x) and g(x) corresponding to the original code to obtain the first check code r(x): r(x)=x 24 m(x)mod g(x) Step 3.3: The codeword c(x) to be transmitted after concatenating the first check code r(x) with the original code is: c(x)=x 24 m(x)+r(x) Step 3.4: The received codeword is s(x). After performing a modulo-2 operation on s(x) and g(x), the remainder is R(x). If R(x) is 0, then no transmission error has occurred. R(x)=s(x)mod g(x)=c(x)mod g(x)={x 24 m(x)+r(x)}mod g(x)={r(x)+r(x)}mod 2=0; If R(x) is not 0, then a transmission error has occurred: R(x)=s(x)mod g(x)={c(x)+e(x)}mod g(x)=e(x)mod g(x); Step 3.6: Set the number of cyclically correctable code elements m with R(x) = 0 as the target.

3. The method for UAV access capacity in the 1090 MHz band based on variable channel and mobility prediction according to claim 1, characterized in that, Step 4 specifically includes the following sub-steps: Step 4.1: N aircraft and n drones are randomly distributed within an airspace of diameter D. Each aircraft is set to a random initial position (X). o Y o Z o ), X o ∈(-D / 2, D / 2), Y o ∈(-D / 2, D / 2), we obtain the distance d from the spacecraft to the ground station d=d o for: Step 4.2: Based on the distance d between the aircraft and the ground station and the signal transmission power f of each aircraft, the propagation loss of the aircraft messages is calculated: Loss = 32.44 + 20lg d + 201g f Step 4.3: Based on the propagation loss of the aircraft message, obtain the input signal power of the demodulator S = P + A - Loss, and the Gaussian white noise power N = n o *B, where P is the transmit power of the civil aircraft ADS-B, A is the receiver sensitivity of the ground station located at the two-dimensional geometric center, n0 is the Gaussian white noise power density, and B is the bandwidth. The demodulator input signal-to-noise ratio r = S / N is obtained, and the M-ary PSK bit error rate is: Step 4.4: After adding cyclic redundancy check (CR). If (112-m) bits out of the 112 bits are correctly received, the message is considered successfully received. The message success rate P is... S-CRC for: Where i is the index of the number of cyclic error-correctable code elements; Step 4.5: Set a random factor v∈(0~1) in the aircraft. If v≥(1-P) S-CR If v < (1-P), then record it as a "good message" in the message group; if v < (1-P) S-C If a message is detected as a "bad message" in the packet, it will be recorded as such. When a message is propagated in free space, a collision occurs and packet loss occurs, the ground station will remove the "bad message" from the message statistics.

4. The method for UAV access capacity in the 1090 MHz band based on variable channel and mobility prediction according to claim 3, characterized in that, Step 4.4 Set the corresponding fading coefficient ρ according to different scenarios, and obtain the message success rate P under that scenario. SCRC : P SCRC =ρ×P S-CRC 。 5. The method for UAV access capacity in the 1090 MHz band based on variable channel and mobility prediction according to claim 1, characterized in that, Step 6 includes the following sub-steps: Step 6.1: Set the flight speed V of the aircraft. Generate a random heading vector (α, β, γ) for each aircraft, where α∈(-1,1), β∈(-1,1), and γ∈(-1,1). Then, the velocity components V of the aircraft in each direction are... X V Y V Z for: Step 6.2: After time T, each time the ground station successfully receives a message, the simulation iteratively updates the position of each aircraft. The updated aircraft positions (X, Y, Z) are: X=X o +V X ×T Y / Y o +V Y ×T Z=Z o +V Z ×T The updated distance d between the spacecraft and the ground station is:

6. The method for UAV access capacity in the 1090 MHz band based on variable channel and mobility prediction according to claim 1, characterized in that, The message update cycle for the sending end of the civil aircraft is as follows: The update cycle of civil aircraft air position messages is a random jitter interval of (0.5-δ, 0.5+δ), where δ is the random jitter factor of the air position message; The update cycle for civil aircraft identification and type messages is a random jitter interval of (5-ε, 5+ε), where ε is the random jitter factor of the aircraft identification and type messages. The update cycle for civil aircraft speed messages is a random jitter interval of (0.5-∈, 0.5+∈), where ∈ is the random jitter factor of the aircraft speed message; The update cycle for the target status message of civil aircraft is a random jitter interval of (1.25-μ, 1.25+μ), where μ is the random jitter factor of the target status message; The update cycle for civil aviation aircraft operation status messages is a random jitter interval of (2.5-τ, 2.5+τ), where τ is the random jitter factor of the aircraft operation status message.

7. A method for UAV access capacity in the 1090 MHz band based on variable channel and mobility prediction according to claim 6, characterized in that, The message update cycle for the sending end of the UAV, set according to the speed ratio, is as follows: The drone airborne location message update cycle is The update cycle for drone identification and type messages is: The drone speed message update cycle is The update cycle for the UAV target status message is: The drone operation status message update cycle is Where ω is the speed ratio of the civil aircraft to the drone.

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