A design method for adaptive rate transmission waveform of UAV measurement and control system

Abstract

The present invention discloses a method for designing an adaptive rate transmission waveform for an unmanned aerial vehicle (UAV) measurement and control system. This method, which belongs to the field of UAV measurement and control technology, addresses the problem that existing widely used wireless networking technologies cannot meet the needs of UAV "swarm" collaborative applications in terms of functionality, performance, reliability, and adaptability to complex electromagnetic environments. The design scheme includes the following steps: Step 1: Decomposing user application indicators into waveform design technical indicators based on user application task requirements; Step 2: Based on the waveform design technical indicators decomposed in Step 1, performing a connectivity analysis on the corresponding user application indicators from three aspects: line-of-sight connectivity judgment, Doppler frequency shift, and link budget, to determine the final waveform technical indicators; Step 3: Designing the waveform frame format based on the determined technical indicators. This method can quickly establish a reliable, high-performance communication transmission link, enabling the UAV "swarm" to possess key information exchange capabilities such as rapid deployment, rapid dynamic access, and adaptive networking transmission.

Description

Technical Field

[0001] The present invention belongs to the technical field of unmanned aerial vehicle (UAV) measurement and control, and in particular relates to a method for designing an adaptive rate transmission waveform for an UAV measurement and control system. Background Art

[0002] Large-scale drone swarms execute missions in complex target environments through real-time sharing and interaction of individual drone intelligence. Autonomous control iterations allow for rapid adaptation to new environments, optimal path planning, and efficient mission completion. Collaborative communication is fundamental to mission completion and also underpins collision avoidance and optimal path planning for large-scale swarms.

[0003] Self-organizing networking technology for unmanned swarm projects is currently booming both domestically and internationally. The U.S. Air Force Laboratory Information Agency (LAI) issued a broad solicitation for a project on autonomous, resilient tactical networks for unmanned swarms, specifically addressing three key areas: dynamic network management, network protocol design, and distributed airborne tactical (DAT) beamforming. Dynamic network management primarily considers communication system performance metrics such as throughput, latency, and reliability, ensuring they meet the operational requirements of the unmanned swarm and achieve dynamic adaptability. These metrics are key to waveform design.

[0004] Existing widely used wireless networking technologies fail to meet the requirements of unmanned swarm collaboration applications due to numerous issues, including functionality, performance, reliability, and adaptability to complex electromagnetic environments. For example, while civilian ad hoc networking protocols like 802.11 / 16 enable adaptive transmission of communication waveforms, the Doppler effect and high dynamics can dramatically reduce waveform reliability under high-speed conditions.

[0005] A method for designing an adaptive waveform for UAV measurement and control systems is studied to establish a fast, dynamic, and reliable high-performance communication transmission link, so that the unmanned "bee swarm" has key information interaction capabilities such as rapid deployment, rapid dynamic access, and adaptive networking transmission. This supports the unmanned "bee swarm" to complete new capabilities such as collaborative detection, cluster action, collaborative tasks, and collaborative evaluation, and has strong application value. Summary of the Invention

[0006] To address the aforementioned issues, the present invention aims to provide a method for designing an adaptive rate transmission waveform for an unmanned aerial vehicle (UAV) measurement and control system. This method designs a suitable data frame format and communication waveform based on the transmitted mission data. The method first quantifies the waveform's user application metrics based on mission requirements. Then, it analyzes connectivity boundary conditions from three perspectives: line-of-sight connectivity, Doppler shift, and link budget. Finally, the adaptive communication waveform is designed. The present invention's adaptive waveform design process primarily involves two aspects: generating an adaptive rate waveform design indicator vector and processing the adaptive rate waveform generation process. Ultimately, the waveform can be adaptively adjusted based on changes in the mission, enabling the receiver to adaptively receive physical layer information without requiring a handshake protocol.

[0007] The technical solution adopted in the present invention is as follows:

[0008] A method for designing an adaptive rate transmission waveform for an unmanned aerial vehicle measurement and control system, the method comprising the following steps:

[0009] Step 1: Decompose the user application indicators into waveform design technical indicators according to the user application task requirements;

[0010] Step 2: Based on the waveform design technical indicators decomposed in Step 1, perform connectivity analysis on the corresponding user application indicators from three aspects: line-of-sight connectivity judgment, Doppler frequency shift, and link budget, and determine the final technical indicators of the waveform;

[0011] Step 3: Design the waveform frame format according to the determined technical indicators.

[0012] In the above technical solution, the user application indicators described in step 1 include communication distance, user data rate, anti-interference performance, bit error rate, transmission delay, operating frequency, system bandwidth, transmission channel environment, and transmission power.

[0013] In the above technical solution, further, the line-of-sight distance determination process in step 1 uses the following formula to calculate the line-of-sight distance:

[0014]

[0015] Where h1 is the height of the airborne antenna, h2 is the height of the ground station antenna, in meters, d max The unit is kilometers.

[0016] In the above technical solution, further, the Doppler shift in step 1 is calculated using the following formula:

[0017]

[0018] Among them, f is the transmitting carrier frequency, v is the relative motion speed, c is the speed of light, and θ is the angle between the incident direction of the radio wave and the relative motion direction. The ability to resist the Doppler effect is improved by adding a pilot sequence during waveform design.

[0019] In the above technical solution, further, the link budget expression formula in step 1 is determined as follows:

[0020] According to the terminal receiving sensitivity formula and the free space propagation formula, the link margin of the system is analyzed. The sensitivity formula is:

[0021] P rmin =-174+NF+10logR b +E b / N0 (3)

[0022] Where NF is the noise factor, R b is the information rate, E b / N0 is the demodulation signal-to-noise ratio of the communication signal;

[0023] Free space propagation formula: Converted into logarithmic form, the distance a wireless signal propagates in free space is expressed as follows:

[0024] L bf =32.44+20lgd+20lgf (4)

[0025] Among them, G r is the gain of the receiving antenna, G t is the gain of the transmitting antenna, λ is the wavelength of the electromagnetic wave, p t is the transmitter power, p r is the receiving power of the receiver; L bf is the transmission loss in dB; d is the transmission distance in km; f is the frequency in MHz. In summary, the link budget is as follows:

[0026] M(dB)=EIRP(dBW)+G r (dBi)-P rmin (dB)-L s (dB) (5)

[0027] Where, EIRP = P t G t is the isotropic effective radiated power, M is the link margin, and if it is greater than 0, it is feasible.

[0028] In the above technical solution, further, the waveform frame format design process in step 3 includes the following steps:

[0029] Step 301: Determine the transmission protection interval T of the frame format according to the transmission distance p =100+D / c, unit is μs, where D is the transmission distance and c is the electromagnetic wave transmission speed;

[0030] Step 301: Obtain the length constraint value T of the synchronization header pseudocode based on the Doppler frequency shift calculated in the connectivity analysis. c <1 / 2(f d +Δf), where f d is the Doppler frequency value, Δf is the maximum frequency difference of the working clock;

[0031] Step 303: Select an appropriate modulation mode;

[0032] Step 304: According to the user's minimum rate R b1 , maximum rate R b2 and correspond to the interference-to-signal ratio JSR1 and JSR2 respectively, and determine the signal bandwidth. The bandwidth is BW=max(JSR1*R b1 / log2(M), JSR2*R b2 / log2(M)), M is the modulation order;

[0033] Step 305: Based on the signal bandwidth BW and the demodulation signal-to-noise ratio E b / N0, and the sensitivity formula, the lowest synchronizable signal power reaching the antenna aperture under sensitivity conditions is derived, P cmin =17-10log(BW)-E b / N0, the energy accumulation length of the synchronization head is The number of pseudocodes L = K / T c ;

[0034] Step 306: Calculate the residual frequency offset based on the length and number of the synchronization pseudocode. The length and number of the random codes obtained in step 305 are used to calculate the length of the phase compensation pseudocode based on the residual frequency offset, which is L / 2. The insertion interval is no more than 250 μs.

[0035] Step 307: Determine the frame format length based on the user rate, synchronization header length, number of synchronization pseudo codes, number and interval of phase compensation pseudo codes, and guard interval;

[0036] Step 308: Determine the channel coding method according to the user rate;

[0037] Step 309: Determine the coding efficiency;

[0038] Step 310: Rate matching, matching with the frame format data by puncturing or padding with zeros at the end;

[0039] Step 311: interleave the frame format data after rate matching;

[0040] Step 312: Scrambling, which is divided into a modulation system with a modulation order of 2 and a modulation system with a modulation order of 4 or above;

[0041] Step 313: Determine the signal sampling rate according to the signal bandwidth, the sampling rate f s >2BW, generally choose f s =4R B , where R B =BW / γ rcc The baud rate designed for the waveform, γ rcc is the raised cosine roll-off coefficient, which is generally taken as 0.22.

[0042] In the above technical solution, further, the modulation mode in step 303 is generally selected as BPSK, QPSK, MSK, and 16QAM. The selection principle is: BPSK modulation mode is preferred. If the maximum bandwidth is limited, QPSK and 16QAM are selected in turn; when the BPSK modulation system transmits a large signal power and requires the power amplifier to work in a nonlinear region, MSK modulation mode is selected; among which, the MSK and BPSK modulation order M=2, the QPSK modulation order M=4; the 16QAM modulation order M=16.

[0043] In the above technical solution, further, in step 308, when the channel rate is higher than 30 Mbps, the LDPC coding mode is selected, and when the channel rate is lower than 30 Mbps, the Turbo code coding mode is selected.

[0044] In the above technical solution, further, in a modulation system with a modulation order of 2, the spread spectrum data is scrambled by a basic scrambling code of length K, and the scrambling method is to multiply the modulated data by the basic scrambling code at the corresponding position in chip order;

[0045] Modulation system with a modulation order of 4 or more: The modulated data is scrambled by a complex scrambling code of length K. The complex scrambling code is generated from the basic scrambling code. The process is as follows:

[0046] v i =(j) i ·v i v i ∈{1,-1},i=1,...,16

[0047] Where v is the basic scrambling code and j represents the complex factor.

[0048] Compared with the prior art, the present invention has the following advantages:

[0049] The present invention proposes a method for designing an adaptive rate transmission waveform for an unmanned aerial vehicle (UAV) measurement and control system, which can quickly establish a dynamic, reliable, and high-performance communication transmission link, enabling the unmanned "bee swarm" to have key information interaction capabilities such as rapid deployment, rapid dynamic access, and adaptive networking transmission. This method supports the unmanned "bee swarm" to complete new capabilities such as collaborative detection, cluster action, collaborative tasks, and collaborative evaluation, and has strong application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Design a flow chart for the adaptive waveform of the UAV measurement and control system;

[0051] Figure 2 Decomposition of indicator system for communication waveform design;

[0052] Figure 3 Design a schematic diagram for the frame format. DETAILED DESCRIPTION

[0053] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0054] like Figure 1 As shown, this embodiment provides a method for designing an adaptive rate transmission waveform for a UAV measurement and control system. The present invention designs a reasonable data frame format and communication waveform based on the transmitted mission data. First, the user application indicators of the waveform are quantified according to the mission requirements. Then, the boundary conditions of connectivity are analyzed from three aspects, namely, line-of-sight connectivity judgment, Doppler frequency shift, and link budget. Finally, the design of the adaptive communication waveform is completed.

[0055] Phase 1: User Application Index Decomposition

[0056] The indicator system of the communication system can constrain the waveform design of the communication system, such as Figure 2 As shown in Figure 2, the communication system indicator system can be divided into two categories: user application indicators and waveform technical indicators. User application indicators mainly include communication distance, user data rate, anti-interference performance, bit error rate, transmission delay, operating frequency, system bandwidth, transmission channel environment, and transmit power, and serve as inputs for communication waveform design. Further decomposition of user application indicators yields a waveform technical indicator system; this waveform indicator system is divided into a primary waveform indicator system and a secondary indicator system.

[0057] The first-level technical indicators of the waveform mainly include sensitivity, antenna gain, dynamic range, symbol rate, modulation method, coding efficiency, spread spectrum method, interference elimination method, interleaving method, scrambling method, demodulation method, channel coding method, frame format, decoding method, mixing method, clock configuration, filter parameters, sampling rate setting, carrier method, diversity reception method, synchronization method, power control method, etc.

[0058] The secondary indicators that can be decomposed are: sensitivity includes demodulation signal-to-noise ratio and noise figure; dynamic range includes AGC control range and limiting filtering; modulation mode includes modulation parameters and modulation style; spread spectrum mode includes spread spectrum length and pseudo code hopping; frequency hopping mode includes frequency set, frequency hopping pattern and hopping rate; interference elimination includes time domain elimination, frequency domain elimination and spatial domain elimination; frame format includes frame length, synchronization length, interleaving length and coding length; multi-carrier mode includes subcarrier spacing, multi-carrier symbol length and CP length; diversity reception includes time domain multi-pulse diversity, frequency domain multi-hop diversity and spatial domain multi-channel diversity; synchronization mode includes synchronization bit code selection and synchronization bit code length, etc.

[0059] The aforementioned indicators are designed in a hierarchical and categorized manner, and a design process for indicator decomposition is outlined. For example, indicators related to communication distance can be decomposed into waveform technical indicators: receive sensitivity, antenna gain, and dynamic range. In reality, this indicator is also related to transmit power and operating frequency. Therefore, in addition to mapping to waveform indicators, the indicator decomposition process also needs to consider the interactions between user application indicators.

[0060] It's important to note that the above mapping relationship is only a general description. Each specific communication system will differ based on mission requirements and may not necessarily include all of the above elements. During design, specific analysis should be conducted based on the above indicator design process, and adaptive trade-offs should be made.

[0061] Phase 2: Connectivity Analysis

[0062] Connectivity analysis mainly includes line-of-sight link analysis, channel Doppler effect, and link budget, as follows:

[0063] (1) Line-of-sight link analysis

[0064] The unmanned "bee swarm" data link under study is intended to operate in the microwave band. Due to its high operating frequency and short wavelength, it is mainly transmitted by direct space waves. Calculate the line-of-sight distance:

[0065]

[0066] Where h1 is the height of the airborne antenna, h2 is the height of the ground station antenna, in meters, d max The unit is kilometers.

[0067] For ground-to-ground communication, assuming that the height of the transmitting and receiving antennas is 2m, the formula shows that the line-of-sight distance is 12km>5km. Therefore, when the ground station antenna height is 2m, the maximum communication distance is 12km.

[0068] (2) Doppler effect

[0069] Doppler shift has a significant impact on the spectrum of the received signal, directly causing a decrease in the system's error rate performance. Due to the relative motion between the drone and the ground station, the frequency of the received signal carrier will change compared to the transmitted signal. This change is called Doppler shift:

[0070]

[0071] Among them, f is the transmitting carrier frequency, v is the relative motion speed, c is the speed of light, and θ is the angle between the incident direction of the radio wave and the relative motion direction.

[0072] In a multipath environment, different Doppler frequency shifts occur in the received signal spectrum, causing Doppler spread. This reduces the receiver input signal-to-noise ratio, which in turn increases the bit error rate. Therefore, the ability to resist the Doppler effect is improved by adding pilot sequences during waveform design.

[0073] (3) Link budget analysis

[0074] The following is an analysis of the system's link margin based on the terminal's receiver sensitivity formula and the free space propagation formula. The following is an analysis of the system's link margin based on the terminal's receiver sensitivity formula and the free space propagation formula. Sensitivity formula:

[0075] P rmin =-174+NF+10logR b +E b / N0 (3)

[0076] Where NF is the noise factor, R b is the information rate, E b / N0 is the demodulation signal-to-noise ratio of the communication signal;

[0077] Free space propagation formula: Converted into logarithmic form, the distance a wireless signal propagates in free space is expressed as follows:

[0078] L bf =32.44+20lgd+20lgf (4)

[0079] Among them, G r is the gain of the receiving antenna, G t is the gain of the transmitting antenna, λ is the wavelength of the electromagnetic wave, pt is the transmitter power, p r is the receiving power of the receiver; L bf is the transmission loss in dB; d is the transmission distance in km; f is the frequency in MHz. In summary, the link budget is as follows:

[0080] M(dB)=EIRP(dBW)+G r (dBi)-P rmin (dB)-L s (dB) (5)

[0081] Where, EIRP = P t G t is the isotropic effective radiated power, M is the link margin, and if it is greater than 0, it is feasible.

[0082] After completing the connectivity analysis, first select the appropriate modulation method, coding method, and coding rate, determine the reasonable baud rate, time slot length, synchronization, scrambling code, spread spectrum code length, frequency hopping pattern, etc., and design a reasonable frame format through optimization combination.

[0083] Phase 3: Adaptive Rate Transmission Waveform Design

[0084] The steps for designing an adaptive waveform based on user metrics and connectivity analysis are as follows:

[0085] a) Determine the transmission protection interval T of the frame format based on the transmission distance p =100+D / c, unit is μs, where D is the transmission distance and c is the electromagnetic wave transmission speed;

[0086] b) According to the Doppler frequency shift obtained in the connectivity calculation, the length constraint value T of the synchronization header pseudocode is obtained c <1 / 2(f d +Δf), where f d is the Doppler frequency value, Δf is the maximum frequency difference of the working clock;

[0087] c) Select an appropriate modulation method. Common options include BPSK, QPSK, MSK, and 16QAM. The principle of selection is to prioritize BPSK modulation. If the maximum bandwidth is limited, QPSK and 16QAM should be selected in that order. When the BPSK modulation system transmits a high signal power and requires the power amplifier to operate in a nonlinear region, MSK modulation should be selected. The modulation order M for MSK and BPSK is 2, the modulation order M for QPSK is 4, and the modulation order M for 16QAM is 16.

[0088] d) Based on the user's minimum rate R b1 , maximum rate R b2and correspond to the interference-to-signal ratio JSR1 and JSR2 respectively, and determine the signal bandwidth. The bandwidth is BW=max(JSR1*R b1 / log2(M), JSR2*R b 2 / log2(M)), M is the modulation order;

[0089] e) According to the signal bandwidth BW and demodulation signal-to-noise ratio E b / N0, and the sensitivity formula, we can deduce the minimum synchronizable signal power reaching the antenna aperture under sensitivity conditions, P cmin =17-10log(BW)-E b / N0(dBm), then the energy accumulation length of the synchronization head is The number of pseudocodes L = K / T c R B .

[0090] f) calculating the residual frequency offset based on the length and number of the synchronization pseudocodes, where the length and number of the random codes obtained in step e) are the lengths and number of the random codes, the residual error of the carrier estimation within the demodulation range is no greater than 1 kHz, the length of the phase compensation pseudocode calculated based on the residual frequency offset is L / 2, and the insertion interval is no greater than 250 μs;

[0091] g) Determine the frame format length based on the user rate, synchronization header length, number of synchronization pseudo codes, number and interval of phase compensation pseudo codes, and guard interval, such as Figure 3 As shown. After the frame format is determined, the upper limit of the service data carrying capacity of each frame of data will also be determined; the synchronization capture 0~m burst consists of L synchronization sequences of length K to achieve signal capture and synchronization; data burst m+1 to burst n consists of three parts: data segment 0 (L0 chips), phase pilot sequence (H chips), data segment 1 (L0 chips). The data segment is used to carry all types of services provided by the system. The bit transmission order is low bit first and high bit last. The phase pilot sequence is used to estimate and correct the phase offset;

[0092] h) Determine the channel coding method based on the user rate. When the channel rate is higher than 30 Mbps, select the LDPC coding method. When the channel rate is lower than 30 Mbps, select the Turbo code coding method.

[0093] i) Determine the coding efficiency, which is generally between 1 / 15 and 3 / 4. The coding efficiency and the spreading length should be considered together. The principle is to use a coding method with a low bit rate as much as possible. If the bit rate is the lowest and there is still room for improvement, consider the spreading length. For example, between a scheme with 1 / 4 coding efficiency and 2x spreading and a scheme with 1 / 8 coding efficiency and 1x spreading, the former is preferred.

[0094] j) Rate matching: puncturing or trailing zero padding is used to match frame format data. The puncturing algorithm refers to 3GPP 25.213. It removes some redundant information in the code while ensuring correct decoding to achieve rate matching.

[0095] k) Interleaving: After rate matching, the frame format data is interleaved to prevent continuous errors and improve the system's anti-interference capability. The interleaving method is random interleaving, and the interleaving length is the service data length in the data frame (after coding and puncturing);

[0096] l) Scrambling: For a modulation system with a modulation order of 2, the spread data is scrambled by a basic scrambling code of length K. The scrambling method is to multiply the modulated data by the basic scrambling code at the corresponding position in chip order.

[0097] For modulation systems with a modulation order of 4 or more, the modulated data is scrambled by a complex scrambling code of length K. The complex scrambling code is generated from the basic scrambling code. The process is as follows:

[0098] v i =(j) i ·v i v i ∈{1,-1},i=1,...,16

[0099] Where v is the basic scrambling code and j represents the complex factor.

[0100] Note: If the number of chips is greater than K, the scrambling code is used cyclically.

[0101] m) Determine the signal sampling rate according to the signal bandwidth, sampling rate f s >2BW, generally choose f s =4R B , where R B =BW / γ rcc The baud rate designed for the waveform, γ rcc is the raised cosine roll-off coefficient, which is generally taken as 0.22.

[0102] Adaptive Waveform Design Example

[0103] (1) Adaptive rate waveform design index vector generation

[0104] The user application index input of the UAV measurement and control system in the present invention is shown in Table 1.

[0105] Table 1. User application indicators of UAV measurement and control system

[0106]

[0107] Since the operating frequency is L-band, electromagnetic wave propagation belongs to line-of-sight propagation, the aircraft's flight altitude is 500m, and the communication distance is 100km. According to formula (4-1), the height of the ground antenna is 3.98m. When in use, the ground antenna is erected at a height of more than 4m. From the perspective of line of sight, no relay is required, which is feasible.

[0108] The maximum moving speed of the UAV is 100m / s. According to formula (4-2), the maximum Doppler frequency deviation is 667Hz. Considering that the clock accuracy is generally 0.1ppm and the maximum frequency error is less than 1kHz, the bit code correlation time should not exceed 0.5ms when designing the synchronization head.

[0109] In order to achieve a transmission distance of 100km under the condition of a transmission power of 33dBm, according to formula (4-5), it can be obtained that the gain of the transmitting and receiving antennas is assumed to be 0dB. Taking into account the link margin of 5dB, the sensitivity should be better than -110dBm. According to the Shannon formula, it is feasible to achieve a sensitivity of -110dBm under 64kbps conditions.

[0110] Through the above analysis, the user index is feasible. When designing, the user rate is used as the classification standard to design the index vector of the communication waveform. Figure 2 The mapping relationship is used to obtain the index vector representation of the waveform design. The specific design parameters are shown in Table 2.

[0111] Table 2. Vector representation of waveform design index of UAV measurement and control system

[0112]

[0113] According to Table 2, four transmission rates can be obtained. The parameter settings for each transmission rate are unified symbol rate of 2Mbps, QPSK modulation mode, frequency hopping rate of 2500 hops / s, QPSK modulation, 0.35 shaping factor, different modulation modes use different mutually orthogonal pseudo-random sequences, data field length is 6.4ms, guard interval is 1.4125ms, each time slot length is 7.8125ms, there are 16 bursts in total, and there are two burst structures: synchronous capture burst and data burst.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for designing an adaptive rate transmission waveform for an unmanned aerial vehicle measurement and control system, characterized in that: The design approach includes the following steps: Step 1: Decompose the user application indicators into waveform design technical indicators according to the user application task requirements; Step 2: Based on the waveform design technical indicators decomposed in Step 1, perform connectivity analysis on the corresponding user application indicators from three aspects: line-of-sight connectivity judgment, Doppler frequency shift, and link budget, and determine the final technical indicators of the waveform; Step 3: Design the waveform frame format according to the determined technical indicators; The user application indicators described in step 1 include communication distance, user data rate, anti-interference performance, bit error rate, transmission delay, operating frequency, system bandwidth, transmission channel environment, and transmission power; In step 1, the line-of-sight distance determination process uses the following formula to calculate the line-of-sight distance: （1） in, h 1 is the height of the airborne antenna, h 2 is the height of the ground station antenna in meters, d max The unit is kilometers; The Doppler shift in step 1 is calculated using the following formula: （2） in, f is the transmitting carrier frequency, v is the relative motion speed, c is the electromagnetic wave transmission speed, θ It is the angle between the incident direction of the radio wave and the relative motion direction. The ability to resist the Doppler effect is improved by adding a pilot sequence during waveform design. The link budget expression formula in step 1 is determined as follows: According to the terminal receiving sensitivity formula and the free space propagation formula, the link margin of the system is analyzed. The sensitivity formula is: （3） Where NF is the noise factor, R b is the information rate, E b / N0 is the demodulation signal-to-noise ratio of the communication signal; Free space propagation formula: , converted into logarithmic form, the distance that a wireless signal propagates in free space is expressed as follows: （4） in, is the gain of the receiving antenna, is the gain of the transmitting antenna, is the wavelength of electromagnetic waves, is the transmitter power, is the receiving power of the receiver; is the transmission loss, in dB; d is the transmission distance in km; f is the frequency in MHz; in summary, the link budget is as follows: （5） in, is the isotropic effective radiated power, If the link margin is greater than 0, the link is feasible.

2. The method for designing an adaptive rate transmission waveform for an unmanned aerial vehicle measurement and control system according to claim 1, characterized in that: The frame format design process of the waveform in step 3 includes the following steps: Step 301: Determine the transmission protection interval of the frame format according to the transmission distance , the unit is us, where is the transmission distance, is the electromagnetic wave transmission speed; Step 301: Obtain the length constraint value of the synchronization header pseudocode based on the Doppler frequency shift calculated in the connectivity analysis ,in is the Doppler frequency value, is the maximum frequency difference of the working clock; Step 303: Select an appropriate modulation mode; Step 304: According to the user's minimum rate R b1 , maximum rate R b2 and correspond to the interference-to-signal ratio JSR1 and JSR2 respectively, and determine the signal bandwidth. The bandwidth is BW=max(JSR1* R b1 / log2(M), JSR2* R b2 / log2(M)), M is the modulation order; Step 305: Based on the signal bandwidth BW and the demodulation signal-to-noise ratio E b / N0, and the sensitivity formula, the lowest synchronizable signal power reaching the antenna aperture under sensitivity conditions is derived. P cmin = 17- 10log(BW)-E b / N0, the energy accumulation length of the synchronization head is , the number of pseudocodes ; Step 306: Calculate the residual frequency deviation based on the length and number of the synchronization pseudocode. The length and number of the random code are obtained in step 305. The length of the phase compensation pseudocode is calculated based on the residual frequency deviation. , the insertion interval is no more than 250us; Step 307: Determine the frame format length based on the user rate, synchronization header length, number of synchronization pseudo codes, number and interval of phase compensation pseudo codes, and guard interval; Step 308: Determine the channel coding method according to the user rate; Step 309: Determine the coding efficiency; Step 310: Rate matching, matching with the frame format data by puncturing or padding with zeros at the end; Step 311: interleave the frame format data after rate matching; Step 312: Scrambling, which is divided into a modulation system with a modulation order of 2 and a modulation system with a modulation order of 4 or above; Step 313: Determine the signal sampling rate according to the signal bandwidth. ,choose ,in The baud rate designed for the waveform, is the raised cosine roll-off coefficient, which is 0.

22.

3. The method for designing an adaptive rate transmission waveform for an unmanned aerial vehicle measurement and control system according to claim 2, characterized in that: In step 303, the modulation mode is selected as BPSK, QPSK, MSK, and 16QAM. The selection principle is: BPSK modulation is preferred. If the maximum bandwidth is limited, QPSK and 16QAM are selected in sequence; when the BPSK modulation system transmits a large signal power and requires the power amplifier to operate in a nonlinear region, MSK modulation is selected; among which, the MSK and BPSK modulation order M=2, the QPSK modulation order M=4; and the 16QAM modulation order M=16.

4. The method for designing an adaptive rate transmission waveform for an unmanned aerial vehicle measurement and control system according to claim 2, wherein: In step 308, when the channel rate is higher than 30 Mbps, the LDPC coding mode is selected, and when the channel rate is lower than 30 Mbps, the Turbo code coding mode is selected.

5. The method for designing an adaptive rate transmission waveform for an unmanned aerial vehicle measurement and control system according to claim 2, wherein: Modulation order 2: The spread data is scrambled by a basic scrambling code of length K. The scrambling method is to multiply the modulated data with the basic scrambling code at the corresponding position in chip order. Modulation system with a modulation order of 4 or more: The modulated data is scrambled by a complex scrambling code of length K. The complex scrambling code is generated from the basic scrambling code. The process is as follows: Where, v is the basic scrambling code, and j represents the complex factor.

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