Differential optimization method of data link communication system

Abstract

The invention discloses a differential optimization method for a data link communication system, which comprises the following steps: S1, in the uplink communication process of the data link communication system, ground equipment sends Beidou ground-based enhancement information to an air unit at a repetition frequency of 5 times / s; s2, based on the received Beidou ground-based enhancement information and the position information and the time information output by the guide and control device, the air unit adopts an improved optimization algorithm to output a differential positioning signal to the guide and control device; s3, in the downlink communication process of the data chain communication system, after differential positioning is realized by the guide and control device, downlink information carrying a differential positioning mark is output to the air unit; and S4, the air unit feeds back differential positioning information to the ground equipment in downlink communication. According to the differential optimization method of the data chain communication system, a plurality of optimization formulas are used, and one path of optimal differential signal with the highest precision is selected from multiple paths of differential signals, so that the purposes of ensuring the reliability of data transmission, reducing transmission error codes and realizing accurate positioning are achieved.

Description

Technical Field

[0001] The present invention relates to the field of data link communication, and more particularly to a differential optimization method for a data link communication system. Background Art

[0002] At present, the differential optimization of data link communication systems generally adopts a separate distance optimization method or a signal-to-noise ratio optimization method. However, as the communication distance of the data link communication system increases, this communication optimization method needs to continuously increase the number of ground equipment monitoring points to achieve the purpose of its communication effect meeting the needs of use.

[0003] In the prior art, for example, a flight trajectory planning method for a UAV data acquisition system, patent application number 202410908880.6, optimizes its flight trajectory to maximize data collection. The method plans its flight trajectory by obtaining the position coordinates of a ground data source and measuring the received signal-to-noise ratio at a reference distance of 1 meter.

[0004] Another example is a patent application number: 202311064485.6, which is a rapid on-the-spot reconstruction collaborative navigation system and method based on data link ranging. The system includes an aerial unmanned subsystem, a ground unmanned subsystem and a communication data link. The aerial unmanned subsystem includes an aerial unmanned flight network composed of multiple aerial unmanned platforms, and the ground unmanned subsystem includes a ground collaborative communication network composed of multiple ground unmanned platforms. The communication data link is connected to each unmanned platform. The method is as follows: the aerial unmanned platform is equipped with an onboard sensor to obtain navigation and positioning data to assist the unmanned platform in navigation and positioning. When the aerial unmanned platform enters the communication range of the ground unmanned platform, the navigation position information of the ground unmanned platform is used to correct the positioning error of the aerial unmanned platform. The data transmitted by each unmanned platform through the communication data link is calculated using a two-way one-way measurement method to obtain the relative distance between the unmanned platforms. That is, the invention adopts a distance optimization method to communicate between the aerial unmanned subsystem and the ground unmanned subsystem.

[0005] From the above content, it can be seen that the current data link communication systems all use a single optimization method, which cannot achieve the effect of precise positioning. Therefore, it is necessary to adopt an optimization algorithm that combines multiple optimization methods to output the optimal differential signal correction positioning to achieve the purpose of precise positioning. Summary of the Invention

[0006] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0007] In order to achieve these objectives and other advantages of the present invention, a differential optimization method for a data link communication system is provided, comprising:

[0008] S1. During the uplink communication process of the data link communication system, the ground equipment sends BeiDou ground-based augmentation information to the air unit at a repetition frequency of 5 times / s;

[0009] S2. The airborne unit uses an improved optimization algorithm based on the received Beidou ground-based augmentation information and the position and time information output by the guidance and control device to output a differential positioning signal to the guidance and control device.

[0010] S3. During the downlink communication process of the data link communication system, after the guidance and control device realizes differential positioning, it outputs downlink information carrying a differential positioning flag to the air unit;

[0011] S4. The air unit feeds back differential positioning information to the ground equipment in downlink communication;

[0012] The improved optimization algorithm is a fusion of noise ratio optimization, distance optimization, and threshold optimization. It selects the highest precision signal from multiple differential signals as the differential positioning signal, and introduces the hysteresis threshold η and the distance threshold correction factor K in the threshold optimization. d To reduce the number of switching times.

[0013] Preferably, the optimization process of the improved optimization algorithm is configured to include:

[0014] S20: Determine whether the airborne unit has received the real-time position and time information output by the guidance and control device. If so, proceed to S21; otherwise, obtain a differential positioning signal using a signal-to-noise ratio optimization method.

[0015] S21. Among all the ground devices and airborne units that can be monitored, find Channel I with the minimum distance using a distance optimization method, and determine whether there is a previously preferred channel. If not, use Channel I as the current preferred channel. Otherwise, proceed to S22.

[0016] S22. In the threshold optimization, it is determined whether to switch to the preferred channel by judging whether the distances of all non-preferred channels II, channel I, and the preferred channel exceed the distance switching threshold.

[0017] Preferably, in S21, the distance optimization is performed by obtaining the distance L between the ground equipment and the aerial unit that can be monitored by the following formula: n :

[0018]

[0019] In the above formula, K h is the environmental factor, X Dn 、Y Dn 、Z Dn are the three-dimensional coordinates of the nth ground equipment; X K 、Y K、Z K are the three-dimensional coordinates of the aerial equipment respectively;

[0020] Among them, the K h Environmental factor K h Obtained by the following formula:

[0021] K h =K m ×K r ×K r

[0022] In the above formula, K m is the multipath factor, K r is the atmospheric refraction factor, K r is the obstacle occlusion factor.

[0023] Preferably, the multipath factor K m Obtained by the following formula:

[0024]

[0025] In the above formula, A i The strength of the i-th multipath signal, τ i is the delay time of the i-th multipath signal, A0 is the intensity of the direct signal, τ0 is the propagation time of the direct signal, and α is the multipath effect weight coefficient;

[0026] Atmospheric refraction factor K r Obtained by the following formula:

[0027]

[0028] In the above formula, P is the atmospheric pressure, T is the absolute temperature, e is the water vapor partial pressure, β and μ are empirical coefficients,

[0029] Obstacle occlusion factor K r Obtained by the following formula:

[0030]

[0031] In the above formula, L j is the occlusion loss of the j-th obstacle, L0 is the reference occlusion loss, and γ is the weight coefficient of the occlusion effect.

[0032] Preferably, in S21, the threshold optimization is performed to obtain the distance difference L by the following formula: 差 :

[0033] L 差 =k d ×|L 优选 -L 非优选 |×(1+η)

[0034] In the above formula, L 优选 is the distance between the ground equipment and the aerial unit in the first optimized channel, L 非优选 The distance between the ground equipment and the aerial unit outside the preferred channel.

[0035] Preferably, the distance threshold correction factor K d Obtained by the following formula:

[0036]

[0037] In the above formula, ε is the signal-to-noise ratio factor, SNR i is the received signal-to-noise ratio of the i-th channel, is the GDOP factor, GDOP is the geometric dilution factor of positioning accuracy, and σ is the intrinsic error constant.

[0038] Preferably, in the data link communication system, a TDD time division system is used for uplink and downlink communications;

[0039] In the TDD time division system, a minimum unit of 100ms time slot cycle includes one 10ms uplink data and nine 10ms downlink data.

[0040] Preferably, the structures of the uplink data and the downlink data both include: a preamble part, a data part, and a pilot part;

[0041] The spreading factor of the uplink data is 16, and the spreading factor of the downlink data is 64.

[0042] The present invention has at least the following beneficial effects:

[0043] First, the present invention effectively integrates multiple optimization methods such as signal-to-noise ratio optimization, distance optimization, and threshold optimization to obtain the optimal differential signal by controlling the number of handoffs based on whether the data link system's air unit equipment has received the location information and time information output by the control device, as well as whether there is an optimized channel in the link.

[0044] Secondly, the present invention uses multiple optimization formulas, such as the signal-to-noise ratio optimization formula, the distance optimization formula, and the threshold optimization formula, to select the optimal differential signal with the highest accuracy from multiple differential signals, thereby ensuring the reliability of data transmission, reducing transmission errors, improving the performance of the communication system, and achieving the purpose of precise positioning;

[0045] Thirdly, the data link system of the present invention realizes the function of preparing to receive uplink differential information by repeatedly sending uplink Beidou ground-based augmentation information mechanism;

[0046] Fourthly, the data link system of the present invention has a link feedback function, which transmits feedback information through the downlink, so that the real-time positioning status of the air unit equipment can be known;

[0047] Fifth, the data link system of the present invention adopts the TDD time division system to achieve 5 Hz transmission in the uplink and 90 Hz transmission in the downlink;

[0048] Sixth, the invention adopts spread spectrum communication in both uplink and downlink data structures, which can achieve 16 times spread spectrum in uplink and 64 times spread spectrum in downlink.

[0049] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of data transmission for uplink communication in the data link system of the present invention;

[0051] Figure 2 This is a schematic diagram of the working principle of the air unit in the data link system of the present invention;

[0052] Figure 3 This is a schematic diagram of the principle of the preferred differential signal output by the ground equipment in the data link system of the present invention;

[0053] Figure 4 Schematic diagram of the process of improving the differential optimization algorithm in the data link system of the present invention;

[0054] Figure 5 Schematic diagram of optimizing the signal-to-noise ratio in the data link system of the present invention;

[0055] Figure 6 Schematic diagram of distance optimization in the data link system of the present invention;

[0056] Figure 7 A schematic diagram of downlink transmission performed by an aerial unit in the data link system of the present invention;

[0057] Figure 8 This is a schematic diagram of the working principle of the ground equipment in the data link system of the present invention;

[0058] Figure 9 Schematic diagram of uplink and downlink TDD time slot allocation in the data link system of the present invention;

[0059] Figure 10 This is a schematic diagram of the data structure distribution of the uplink 10ms in the data link system of the present invention;

[0060] Figure 11 Schematic diagram of data structure distribution in the data link system of the present invention for the downlink 10ms. DETAILED DESCRIPTION

[0061] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0062] The present invention discloses a data link communication system and a differential optimization method thereof. The system involves a ground Beidou receiver (the ground Beidou receiver of the present invention adopts a model SB-S100, receives Beidou information through a Beidou antenna, and outputs it to a ground device), a ground device (the ground device of the present invention adopts a model SD-S300 ground device, which realizes two-way communication with an aerial unit and simultaneously receives signals from the ground Beidou receiver), an aerial unit (the aerial unit of the present invention adopts a model SK-S200, which receives uplink information from the SD-S200 ground device and simultaneously transmits differential positioning information, runs a differential optimization algorithm, and outputs differential optimization information), a guidance and control device, and other equipment. The method integrates three differential optimization methods: signal-to-noise ratio optimization, distance optimization, and threshold optimization. The optimization algorithm is used to determine whether the aerial unit device of the data link system receives position information and time information output by the guidance and control device. Determine whether to use signal-to-noise ratio optimization or distance optimization to obtain the preferred differential signal; based on whether there is an optimized channel in the link and the number of switching times, determine whether to use distance optimization or threshold optimization to obtain the preferred differential signal; this method uses the signal-to-noise ratio optimization formula, the distance optimization formula, and the threshold optimization formula to select the preferred differential signal with the highest accuracy from multiple differential signals, and the aerial unit of the data link system outputs the preferred differential signal to the guidance and control device, which positions itself through differential deviation correction to achieve the purpose of precise positioning. In this solution, the data link communication system realizes the differential positioning function through the preferred differential signal received by the guidance and control device and its own positioning information, and the structure and working principle of the guidance and control device belong to the existing technology (the guidance and control device in the present invention uses the S-DK-S400 model, which can output positioning information and time information, and output downlink information to the ground equipment after differential positioning), so it will not be elaborated on here.

[0063] The present invention discloses a data link communication system and a differential optimization method thereof, and the specific operation process is as follows:

[0064] 1. Uplink communication to obtain Beidou ground-based augmentation information

[0065] This invention obtains BeiDou ground-based augmentation information through uplink communication of the data link communication system. The uplink communication transmission block diagram is shown in the figure. Figure 1 shown.

[0066] The ground-based Beidou receiver receives Beidou satellite signals through the Beidou antenna connected to it. After positioning is achieved, it broadcasts Beidou ground-based augmentation information to ground equipment at a frequency of 1HZ.

[0067] After the ground equipment receives the Beidou ground-based augmentation information broadcast by the ground Beidou receiver, it transmits the Beidou ground-based augmentation information from the ground equipment to the air unit of the data link system through the uplink wireless link by wireless means through the data link system. The air unit equipment receives the RF signal sent by the ground equipment through the microstrip antenna, and transforms it into an uplink intermediate frequency signal through filtering, low-noise amplification and filtering processing. Then, it uses RF ADC sampling to down-convert the intermediate frequency signal, move the intermediate frequency signal to the baseband signal and send it to the signal processing module, and then demodulate and decode the baseband data to restore the Beidou ground-based augmentation information. The principle block diagram of the air unit is as follows: Figure 2 shown.

[0068] In order to ensure that every broadcast Beidou ground-based augmentation information can be received by the aerial unit, the ground equipment adopts a mechanism of repeatedly sending Beidou ground-based augmentation information with a repetition frequency of 5 times / s, which effectively ensures that it can communicate with the aerial unit equipment multiple times within 1S, reducing the possibility of not being able to receive or receiving erroneous Beidou ground-based augmentation information, and realizing accurate reception of ground Beidou ground-based augmentation information.

[0069] 2. The empty order unit adopts the optimization algorithm to output the optimal differential signal

[0070] The aerial unit equipment of the data link system obtains the position information and time information of the guidance and control device through the RS422 serial port 1 of the guidance and control device. The guidance and control device receives the Beidou satellite signal through the Beidou antenna, and after positioning is achieved, it outputs the position information and time information to the aerial unit equipment.

[0071] The aerial unit equipment of the data link system combines the uplink received Beidou ground-based augmentation information and the guidance and control device to output position information and time information, and uses the optimization algorithm to output the optimal differential signal. The output process is as follows: Figure 3 As shown in Figure 3, the algorithm combines three differential optimization methods: signal-to-noise ratio optimization, distance optimization, and threshold optimization.

[0072] 1. Perform differential optimization based on the signal-to-noise ratio of each channel

[0073] When the air unit of the data link system does not receive the real-time position and time information output by the guidance and control device, it is impossible to calculate the distance between the air unit and the ground equipment of the observable data link system. In this case, the differential optimization can be achieved by using the signal-to-noise ratio optimization formula; for example Figure 5 As shown in FIG, the signal-to-noise ratio of the ground equipment of different channels received by the air unit of the data link system is compared, and the channel with the best signal-to-noise ratio is selected as the preferred channel by the following formula.

[0074] max n (SNR1, SNR2, ..., SNR n ) (1)

[0075] Signal-to-noise ratio (SNR) = 10log10(Psignal / Pnoise), where Psignal represents signal power and Pnoise represents noise power. The SNR is expressed in decibels (dB). The SNR is the ratio of signal power to noise power, measuring the relative strength of the useful signal and noise. A higher SNR indicates a clearer signal despite noise interference; a lower SNR indicates a more susceptible signal to noise. The SNR is a key indicator of signal quality.

[0076] To improve the signal-to-noise ratio of the airborne unit, that is, to enhance the useful signal and suppress noise, increasing the transmit power can effectively enhance the signal. This design uses shielding grounding, filtering, differential transmission and other methods to suppress noise generation and interference.

[0077] In terms of protocol, redundant design and confirmation mechanism are adopted to improve the reliability of data transmission and thus improve communication performance.

[0078] 2. Perform differential optimization based on the minimum distance principle

[0079] When the aerial unit equipment of the data link system receives the real-time position and time information output by the guidance and control device, the geometric calculation formula in three-dimensional space is used to comprehensively consider the influence of the environment in the actual use of the data link system (such as signal transmission affected by multipath effect, atmospheric refraction, obstacle obstruction, etc.), and introduce the environmental factor K h , use the following distance calculation formula to calculate:

[0080]

[0081] The environmental sub-formula is as follows:

[0082] K h =K m ×K r ×K r (3)

[0083] Among them: K m It is the multipath factor. The multipath effect is caused by signal transmission, refraction and scattering, resulting in signal delay and intensity fluctuation.

[0084] The multipath factor is as follows:

[0085]

[0086] Among them, A i is the strength of the i-th multipath signal, τ i is the delay time of the i-th multipath signal, A0 is the intensity of the direct signal, τ0 is the propagation time of the direct signal, and α is the multipath effect weight coefficient, which is generally set to 0.2;

[0087] K r It is the atmospheric refraction factor. Atmospheric refraction will change the signal propagation path, especially in long-distance or high-altitude scenarios. The atmospheric refraction factor helps correct the propagation path error of electromagnetic waves by quantifying the refractive index and tropospheric delay. The atmospheric refraction factor formula is

[0088]

[0089] Where P is the atmospheric pressure, T is the absolute temperature, e is the water vapor partial pressure, β and μ are empirical coefficients, and β = 7.76*10 - 5 K / hPa, μ=0.622;

[0090] K O is the obstacle blocking factor. Obstacles (such as buildings and trees) will block the signal, causing the signal strength to decrease. The obstacle factor formula is:

[0091]

[0092] Among them L j is the occlusion loss of the j-th obstacle (dB), L0 is the reference occlusion loss (usually 10 dB), and γ is the weight coefficient of the occlusion effect (usually 0.2);

[0093] Substitute formulas (4), (5), and (6) into formula (3) to obtain the environmental factor shown below:

[0094]

[0095] When the data link system is communicating in an open area, without any obstacles, Lj = 0, then K O =1, Formula 7 can be simplified to

[0096]

[0097] The coordinate position information of the aerial unit equipment of the data link system is K(X K, Y K, Z K ), the location coordinates of the ground equipment 1 of the data link system are D1(X D1, Y D1, Z D1 ), the location coordinates of the ground equipment 2 of the data link system D2 (X D2, Y D2, Z D2 ), the location coordinates of the ground equipment n of the data link system Dn(X Dn, Y Dn, Z Dn ),like Figure 6 shown.

[0098] Formula 9 and Formula 10 are derived from Formula 2 to calculate the distance between the ground equipment 1 and ground equipment 2 of the data link system and the air unit of the data link system.

[0099]

[0100] Formula for calculating the distance between the ground equipment 2 of the data link system and the air unit of the data link system

[0101]

[0102] After calculating the distance between all ground equipment and air units that can monitor data links, use the distance optimization formula: min n (L1, L2, ..., L n )(11), find the ground equipment closest to the air unit of the data link system.

[0103] According to Formula 11, when n=0, it means that the air unit has not received the uplink differential signal. At this time, it is necessary to determine whether the air unit has never received a differential signal or has received a differential signal but the signal was later interrupted. If the air unit has never received a differential signal, it returns to the air unit and continues to wait for receiving the differential signal. If the air unit has received a differential signal before but the signal was suddenly interrupted, the last packet of data before the signal was interrupted is used as the preferred differential signal.

[0104] When n = 1, Formula 11 is transformed into min1(L1 / L2 / … / Ln). In particular, when the airborne unit of the data link system can only receive the differential signal from any one of the ground observation stations in (L1 / L2 / … / Ln), the channel of the current ground device is used as the preferred channel.

[0105] When n>1, when the air unit of the data link system receives a differential signal greater than that of one ground observation station, it performs optimization in two cases to obtain the optimal differential signal;

[0106] Case 1: There is no preferred channel, so min is used directly n (L1, L2, ..., L n ) formula to calculate the channel with the minimum distance, and take the channel with the minimum distance as the preferred channel;

[0107] Case 2: If there is a preferred channel, the distance optimization formula cannot be used directly for optimization. Instead, the distance switching threshold is used for optimization.

[0108] 3. Perform differential optimization according to the distance switching threshold

[0109] The preferred channel is switched by judging whether the distance between the data link system ground equipment and the data link system air unit of all non-preferred channels and preferred channels exceeds the distance switching threshold. In order to minimize the number of switches and ensure that the received differential signal can achieve the effect of differential positioning, the design introduces a hysteresis threshold and a distance correction factor K. d , distance difference formula

[0110] L 差 =k d ×|L 优选 -L 非优选 |×(1+η) (12)

[0111] Among them, K d is the distance correction factor; L 优选 The distance between the data link ground equipment and the data link system air unit is the preferred channel; L 非优选 is the distance between the data link ground equipment of other non-preferred channels and the data link system air unit; η is the hysteresis threshold, generally set to 10% to prevent small fluctuations from causing switching;

[0112] The distance correction factor formula is as follows:

[0113]

[0114] Among them, the ε signal-to-noise ratio factor has a value range of (5, 10], and is generally set to 5; SNR i is the received signal-to-noise ratio of the i-th channel; is the GDOP factor, with a range of [0.25, 1] and a general value of 0.5; GDOP is the geometric dilution factor of positioning accuracy, and is generally 1 to 2 in the data link system; σ is the inherent error constant, with a range of (0.2, 0.5] and a general value of 0.2;

[0115] Distance threshold correction factor K d It is a function of SNR, GDOP, and distance difference. A high SNR corresponds to a smaller correction factor, and a low SNR requires a larger correction factor. When GDOP is high, the positioning error is large, and the correction factor requires a larger adjustment. When GDOP is low, the positioning error is small, and the correction factor is small.

[0116] By setting the distance switching threshold, the distance switching threshold symbol is set to L m , unit is km.

[0117] When L 差 <L m ,Although the preferred channel is not the one with the smallest distance, the distance difference does not reach the switching threshold distance, so the current preferred channel is maintained and the preferred difference information is output;

[0118] When L 差 ≥L m , triggering the distance threshold, the optimal channel is switched to the channel of the ground equipment closest to the data link air unit, and the optimal differential information is output;

[0119] The value of the distance threshold needs to take into account factors such as signal-to-noise ratio and positioning effect.

[0120] According to the above three fusion optimization algorithms, the aerial unit of the data link system of the present invention outputs the optimal differential signal to the guidance and control device, and the guidance and control device positions itself through differential deviation correction to achieve the purpose of precise positioning.

[0121] 3. Downlink communication, returning differential positioning information

[0122] This invention transmits differential positioning information of aerial equipment back through downlink communication. The downlink backhaul block diagram is as follows: Figure 7 After achieving differential positioning, the guidance and control device outputs downlink information to the air unit of the data link system through serial port 3. The downlink information carries the differential positioning flag. The air unit then wirelessly transmits the downlink information from the air unit air interface to the ground equipment of the data link via the downlink of the data link system.

[0123] The ground equipment of the data link system adopts AD broadband sampling + baseband processing architecture. The downlink signal (S-band signal) at the RF end passes through the RF transceiver chip and is sent to the AD sampling. The baseband processing module performs digital down-conversion (DDC) on the AD signal to the baseband, performs low-pass filtering, obtains the broadband baseband signal, and then performs filtering extraction, matched filtering, timing synchronization, frequency synchronization, channel estimation, equalization, demodulation, decoding, and obtains the original data after CRC check. The monitoring software is used to display the differential positioning mark to confirm that the guidance and control device has achieved differential positioning. The working principle of the ground equipment of the data link system is as follows: Figure 8 shown.

[0124] It should be noted that in data link communication, the uplink and downlink time slots are allocated as follows:

[0125] In order to achieve the transmission of BeiDou ground-based augmentation information at 5Hz uplink and 90Hz downlink, in the minimum unit time slot cycle of 100ms, one uplink 10ms sends data and nine 10ms downlink data; the uplink information has a cycle of 200ms, and the uplink information consists of two 10ms and two 90ms to form a frame of information. In TDD mode half-duplex, the uplink and downlink time within 200ms is distributed as follows Figure 9 shown.

[0126] In addition, in the data link communication, the uplink and downlink data structure layout is as follows: Figure 10-11As shown, the uplink and downlink data are sent with a period of 10ms, and the basic structure of preamble, data and pilot is adopted. The uplink spreading factor is 16, and the downlink spreading factor is 64. In the present invention, different spreading factors are used for uplink and downlink to meet different uplink and downlink data rate requirements and different services. Corresponding to the time slot distribution described above, in the smallest unit, the downlink transmission is 90ms and the uplink transmission is 10ms. Using a larger spreading factor for the downlink can obtain a higher processing gain.

[0127] The above solution is only an illustration of a preferred embodiment, but is not limited thereto. When implementing the present invention, appropriate replacements and / or modifications can be made according to user needs.

[0128] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and exemplary embodiments. They can be applied to a variety of fields suitable for the present invention. Further modifications will be readily apparent to those skilled in the art. Therefore, the present invention is not limited to the specific details and illustrations shown and described herein without departing from the general concept defined by the claims and their equivalents.

Claims

1. A differential optimization method for a data link communication system, characterized in that: include: S1. During the uplink communication process of the data link communication system, the ground equipment sends BeiDou ground-based augmentation information to the air unit at a repetition frequency of 5 times / s; S2. The airborne unit uses an improved optimization algorithm based on the received Beidou ground-based augmentation information and the position and time information output by the guidance and control device to output a differential positioning signal to the guidance and control device. S3. During the downlink communication process of the data link communication system, after the guidance and control device realizes differential positioning, it outputs downlink information carrying a differential positioning flag to the air unit; S4. The air unit feeds back differential positioning information to the ground equipment in downlink communication; The improved optimization algorithm is a fusion of noise ratio optimization, distance optimization, and threshold optimization. It selects the highest precision signal from multiple differential signals as the differential positioning signal, and introduces the hysteresis threshold η and the distance threshold correction factor K in the threshold optimization. d To reduce the number of switching times.

2. The differential optimization method for a data link communication system according to claim 1, wherein: The optimization process of the improved optimization algorithm is configured to include: S20: Determine whether the airborne unit has received the real-time position and time information output by the guidance and control device. If so, proceed to S21; otherwise, obtain a differential positioning signal using a signal-to-noise ratio optimization method. S21. Among all the ground devices and airborne units that can be monitored, find Channel I with the minimum distance using a distance optimization method, and determine whether there is a previously preferred channel. If not, use Channel I as the current preferred channel. Otherwise, proceed to S22. S22. In the threshold optimization, it is determined whether to switch to the preferred channel by judging whether the distances of all non-preferred channels II, channel I, and the preferred channel exceed the distance switching threshold.

3. The differential optimization method for a data link communication system according to claim 2, wherein: In S21, the distance optimization is to obtain the distance L between the ground equipment and the air unit that can be monitored by the following formula: n : In the above formula, K h is the environmental factor, X Dn 、Y Dn 、Z Dn are the three-dimensional coordinates of the nth ground equipment; X K 、Y K 、Z K are the three-dimensional coordinates of the aerial equipment respectively; Among them, the K h Environmental factor K h Obtained by the following formula: K h =K m ×K r ×K r In the above formula, K m is the multipath factor, K r is the atmospheric refraction factor, K r is the obstacle occlusion factor.

4. The differential optimization method for a data link communication system according to claim 3, wherein: Multipath factor K m Obtained by the following formula: In the above formula, A i The strength of the i-th multipath signal, τ i is the delay time of the i-th multipath signal, A0 is the intensity of the direct signal, τ0 is the propagation time of the direct signal, and α is the multipath effect weight coefficient; Atmospheric refraction factor K r Obtained by the following formula: In the above formula, P is the atmospheric pressure, T is the absolute temperature, e is the water vapor partial pressure, β and μ are empirical coefficients, and the obstacle blocking factor K is r Obtained by the following formula: In the above formula, L j is the occlusion loss of the j-th obstacle, L0 is the reference occlusion loss, and γ is the weight coefficient of the occlusion effect.

5. The differential optimization method for a data link communication system according to claim 1, wherein: In S21, the threshold optimization is performed to obtain the distance difference L by the following formula: 差 : L 差 =k d ×|L 优选 -L 非优选 |×(1+n) In the above formula, L 优选 is the distance between the ground equipment and the aerial unit in the first optimized channel, L 非优选 The distance between the ground equipment and the aerial unit outside the preferred channel.

6. The differential optimization method for a data link communication system according to claim 5, wherein: Distance threshold correction factor K d Obtained by the following formula: In the above formula, ε is the signal-to-noise ratio factor, SNR i is the received signal-to-noise ratio of the i-th channel, is the GDOP factor, GDOP is the geometric dilution factor of positioning accuracy, and σ is the intrinsic error constant.

7. The differential optimization method for a data link communication system according to claim 1, wherein: In the data link communication system, TDD time division system is used for uplink and downlink communication; In the TDD time division system, a minimum unit of 100ms time slot cycle includes one 10ms uplink data and nine 10ms downlink data.

8. The differential optimization method for a data link communication system according to claim 4, wherein: The structures of the uplink data and the downlink data both include: a preamble part, a data part, and a pilot part; The spreading factor of the uplink data is 16, and the spreading factor of the downlink data is 64.

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