A UAV communication method resistant to complex electromagnetic environments and jamming interference

Abstract

This invention discloses a UAV communication method resistant to complex electromagnetic environments and jamming interference, belonging to the field of wireless communication. This invention solves the problems of insufficient frequency hopping anti-interference capability, lag in dynamic spectrum response, limited spatial filtering, and limited processing gain of single spread spectrum technology in strong broadband jamming interference, multi-point intelligent interference, and complex electromagnetic environments. This invention achieves authentication, synchronization, and parameter negotiation during the initial handshake phase through high-precision time synchronization of frequency hopping and direct-spread spectrum (DSS) frequency point anti-interference. When there is no service, it continuously calibrates time and dynamically updates parameters through low duty cycle heartbeat signals, maintaining link synchronization. When data transmission occurs, it transmits and demodulates according to the latest parameters, achieving dual gains from frequency hopping diversity and DSS frequency point anti-interference. Furthermore, it automatically backs down and rebuilds the link after losing synchronization, significantly improving the robustness and survivability of UAVs in complex interference environments.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, specifically to a UAV communication method that resists complex electromagnetic environments and jamming interference. Background Technology

[0002] Unmanned aerial vehicles (UAVs) are widely used in logistics, agricultural plant protection, aerial surveying, and emergency communications, making UAV communication crucial. UAV communication links include uplink / downlink command and control (C&C) links between the ground control station (GCS) and the UAV, as well as airborne relay or data sharing links between UAVs. These primarily rely on wireless communication technologies such as Wi-Fi, 4G / 5G, dedicated data links, or satellite communication. However, the UAV communication environment is complex and susceptible to congestion interference (broadband interference). Congestion interference increases the noise floor by releasing high-power, wide-spectrum noise or pseudo-random signals in the operating frequency band, overwhelming communication signals and causing performance degradation or even interruption of the communication link.

[0003] Existing technologies mainly include frequency hopping, dynamic spectrum access, spatial filtering, and direct sequence spread spectrum. However, these methods all have limitations when facing strong broadband jamming or multi-point intelligent interference: frequency hopping is difficult to cope with full-band jamming; dynamic spectrum access has a delayed response due to sensing and switching delays; spatial filtering performance degrades when interference and signal directions are close or when there are multiple interference sources; and spread spectrum technology has limited processing gain. In addition, the strict platform constraints (size, weight, power consumption) and high maneuverability of UAVs further require anti-jamming technologies to have a high degree of adaptability and real-time performance, which existing solutions often cannot meet, leading to easy interruption of communication links in complex electromagnetic environments.

[0004] Therefore, it does not meet the existing requirements, so we propose a UAV communication method that is resistant to complex electromagnetic environments and jamming interference. Summary of the Invention

[0005] The purpose of this invention is to provide a UAV communication method that resists complex electromagnetic environments and jamming interference. By deeply coordinating high-precision time synchronization, adaptive frequency hopping, and direct sequence spread spectrum, and introducing low duty cycle heartbeat signals for dynamic link maintenance, a multi-dimensional anti-interference mechanism with frequency diversity, time diversity, and coding gain is constructed. This enables rapid establishment, continuous synchronization, and reliable transmission of communication links under strong broadband jamming interference and complex electromagnetic environments, effectively overcoming the limitations of existing single technical solutions in dealing with full-band jamming, response delay, and platform adaptability, and solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a UAV communication method resistant to complex electromagnetic environments and jamming interference, the method comprising:

[0007] Step 1: The command and control system and the UAV conduct an initial communication handshake on one or more pre-agreed initial frequency points. The handshake information includes identity authentication information and completes high-precision time synchronization between the two parties. At the same time, they negotiate and determine the frequency hopping frequency point sequence, frequency hopping timestamp, and pseudo-random code parameters used for direct sequence spread spectrum for the next communication. The pseudo-random code parameters include code pattern, initial phase, and spread spectrum gain.

[0008] Step 2: After the initial communication handshake is completed, if there is no business data transmission, both parties maintain a necessary communication with a low rate and low duty cycle to continuously calibrate the time base of both parties and dynamically update and confirm the frequency hopping pattern and spreading parameters of the next one or more future data frames.

[0009] Step 3: When the command and control system or UAV has business data to send, the data packet to be transmitted is encapsulated in a data frame. The data frame is transmitted at the physical layer following the latest synchronized frequency hopping point in Step 2, and direct sequence spread spectrum modulation is performed on the latest synchronized frequency hopping point using synchronized spread spectrum parameters to realize data exchange.

[0010] Step 4: Repeat steps 2 and 3 to continuously maintain the communication link. If the handshake synchronization signal between the two parties is interrupted for more than the preset time limit due to extreme interference, the two parties shall return to step 1 and try to initiate the handshake again at the agreed initial frequency point to re-establish synchronization and restore the communication link.

[0011] In this method, direct sequence spread spectrum technology is used to extend the signal energy to a frequency band much larger than the original information bandwidth. At the receiving end, despreading is performed to obtain processing gain. Among them, processing gain The bandwidth of the spread spectrum signal With raw information bandwidth The ratio (usually expressed in decibels (dB)) is as follows:

[0012]

[0013] in, The chip rate of the pseudo-random code; Information bit rate;

[0014] The processing gain This is directly reflected in the improved signal-to-interference ratio (SIR) after despreading at the receiving end. Compared to the signal-to-interference ratio before despreading The following relationship exists:

[0015] (dB)

[0016] When the received signal power is much lower than the interference noise power (i.e.) (If it is a negative value), as long as After de-expansion, the true faith is obtained.

[0017] Furthermore, during data transmission in step three, frequency hopping technology enables the communication signal to switch rapidly between multiple frequency points. When some frequency points are interfered with, the communication link quickly switches to an uninterrupted frequency point to continue communication, thus avoiding multi-point blocking interference. The anti-interference capability is enhanced through frequency hopping gain. The characterization is as follows:

[0018] Assume the total number of available frequency points is The number of frequency points that the interfering party can simultaneously interfere with is The probability that a drone communication can successfully avoid interference in one instance is: ;

[0019] For a long time The probability of hopping communication completely avoiding interference is... ;

[0020] Drone communication increases the number of available frequency points and number of jumps This is used to reduce the probability of being continuously interfered with.

[0021] Furthermore, frequency hopping technology and direct sequence spread spectrum technology work together. Frequency hopping provides frequency diversity for the direct sequence spread spectrum system, while direct sequence spread spectrum provides anti-interference redundancy at a single frequency point for the frequency hopping system. The total anti-interference margin of the system is the sum of the gains of the two technologies.

[0022] Furthermore, both the command and control system and the drone terminal include:

[0023] The baseband processing unit is used to generate and process PN codes for spreading, as well as to spread and despread data.

[0024] The microprocessor and control unit are used to run communication protocols, generate and parse frequency hopping / spreading instructions, and manage the synchronization state machine;

[0025] Also includes:

[0026] Frequency hopping synthesizers are used to switch to the frequency specified by a frequency hopping pattern within microseconds.

[0027] A transceiver is used to perform signal modulation, up-conversion, transmission, reception, down-conversion, and demodulation.

[0028] Furthermore, the operating frequency band for the UAV communication is the ISM band, namely 2400-2483.5MHz and 5725-5850MHz, and all frequency points of the frequency hopping pattern must fall within the ISM band.

[0029] Furthermore, the frequency hopping pattern generation adopts a time-based pseudo-random frequency hopping pattern. The command and control system and the UAV use the same seed and encryption algorithm to calculate the next frequency hopping point in real time. The same seed is exchanged or pre-programmed during the initial communication handshake.

[0030] Furthermore, in step two, dynamically updating and confirming the frequency hopping pattern and spreading parameters further includes:

[0031] Based on real-time assessment of current channel quality and interference levels, the number of frequency points and hopping period of the frequency hopping pattern are adaptively adjusted.

[0032] The spreading gain of direct sequence spread spectrum is dynamically adjusted according to changes in interference intensity.

[0033] Furthermore, the frequency hopping pattern and spreading parameters are encrypted and transmitted using a key distribution-based encryption algorithm;

[0034] Meanwhile, during low-rate, low-duty-cycle communication, a differential time synchronization mechanism is introduced to compensate for clock drift by calculating the difference in timestamps between consecutive frames, and to continuously calibrate the time base of both parties.

[0035] Furthermore, in step three, the data frame undergoes forward error correction coding and interleaving before transmission. The forward error correction coding uses adaptive coding and modulation technology, which dynamically selects the error correction code rate and modulation method based on real-time channel state information. The interleaving process uses a hybrid interleaving scheme that combines block interleaving and convolutional interleaving to combat sudden interference.

[0036] Furthermore, in step four, the preset time limit is dynamically adjusted based on the reliability of the communication link and environmental interference. The adjustment strategy is based on historical communication success rates and real-time channel estimation, including:

[0037] The preset time limit is adjusted through a controller based on fuzzy logic. The controller's input variables include recent communication success rate, signal-to-noise ratio estimate, and interference detection statistics. The output is the updated synchronization interruption timeout threshold.

[0038] If extreme interference causes the handshake synchronization signal to be interrupted and triggers the process of returning to step one, then when re-initiating the handshake, the scanning and fast handshake protocol will be used preferentially on multiple preset initial frequency points to shorten the link recovery time.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] 1. This invention uses frequency hopping technology to enable communication signals to switch quickly between multiple frequency points. Even if some frequency points are interfered with, the communication link can quickly switch to a clean frequency point that is not interfered with to continue communication, thereby effectively avoiding multi-point blocking interference.

[0041] 2. This invention uses direct sequence spread spectrum technology to uniformly spread the signal energy that was originally concentrated in a narrow band across an extremely wide frequency band, thereby significantly reducing the signal power spectral density per unit frequency band and enabling it to be concealed under environmental noise levels.

[0042] 3. This invention combines frequency hopping technology with direct sequence spread spectrum technology. Frequency hopping provides frequency diversity for direct sequence spread spectrum systems, while direct sequence spread spectrum provides anti-interference redundancy for frequency hopping systems at a single frequency point. The two technologies complement each other, greatly improving the robustness and survivability of the system in complex and unknown interference environments.

[0043] 4. By designing the initial communication handshake and continuous synchronization frames, this invention ensures the accuracy of synchronization while minimizing the overhead of synchronization, and uses most of the bandwidth resources for effective data transmission, thereby improving spectrum utilization. Attached Figure Description

[0044] Figure 1 This is a flowchart of the UAV communication method for resisting complex electromagnetic environments and jamming interference according to the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] To address the technical challenges of existing UAV communication technologies in strong broadband jamming, multi-point intelligent interference, and complex electromagnetic environments, such as insufficient frequency-hopping anti-jamming capability, lag in dynamic spectral response, limited spatial filtering, and limited gain of single spread spectrum techniques, please refer to [link to relevant documentation]. Figure 1 This embodiment provides the following technical solution:

[0047] A UAV communication method resistant to complex electromagnetic environments and jamming interference, the method comprising:

[0048] Step 1: The command and control system and the UAV conduct an initial communication handshake on one or more pre-agreed initial frequency points. The handshake information includes identity authentication information and completes high-precision time synchronization between the two parties. At the same time, they negotiate and determine the frequency hopping frequency point sequence, frequency hopping timestamp, and pseudo-random code parameters used for direct sequence spread spectrum for the next communication. The pseudo-random code parameters include code pattern, initial phase, and spread spectrum gain.

[0049] Step 2: After the initial communication handshake is completed, if there is no business data transmission, both parties maintain a necessary communication with a low rate and low duty cycle to continuously calibrate the time base of both parties and dynamically update and confirm the frequency hopping pattern and spreading parameters of the next one or more future data frames.

[0050] Step 3: When the command and control system or UAV has business data to send, the data packet to be transmitted is encapsulated in a data frame. The data frame is transmitted at the physical layer following the latest synchronized frequency hopping point in Step 2, and direct sequence spread spectrum modulation is performed on the latest synchronized frequency hopping point using synchronized spread spectrum parameters to realize data exchange.

[0051] Step 4: Repeat steps 2 and 3 to continuously maintain the communication link. If the handshake synchronization signal between the two parties is interrupted for more than the preset time limit due to extreme interference, the two parties shall return to step 1 and try to initiate the handshake again at the agreed initial frequency point to re-establish synchronization and restore the communication link.

[0052] The technical effects of the above solution are as follows: A reliable communication foundation is established during the initial handshake phase through high-precision time synchronization and dynamic parameter negotiation mechanisms. Continuous calibration of the time reference and dynamic updates of communication parameters are achieved using low duty cycle heartbeat signals, effectively overcoming the weakness of traditional frequency-hopping systems that are prone to losing synchronization during long periods of no service transmission. Through deep synergy between frequency hopping and direct-sequence spread spectrum (DSSB) technologies, both frequency diversity gain and anti-interference redundancy on a single frequency point are achieved, enabling the system to quickly switch to a clean frequency point and maintain communication continuity when encountering broadband congestion interference. Simultaneously, it possesses autonomous recovery capabilities, automatically reverting to the initial frequency point to rebuild the link after communication interruption caused by extreme interference, thereby significantly improving the communication reliability, real-time performance, and survivability of UAVs in complex electromagnetic environments.

[0053] In the data transmission process of step three, frequency hopping technology enables the communication signal to switch rapidly between multiple frequency points. When some frequency points are interfered with, the communication link quickly switches to an uninterrupted frequency point to continue communication, thus avoiding multi-point blocking interference. The anti-interference capability is achieved through frequency hopping gain. The characterization is as follows:

[0054] Assume the total number of available frequency points is The number of frequency points that the interfering party can simultaneously interfere with is The probability that a drone communication can successfully avoid interference in one instance is: ;

[0055] For a long time The probability of hopping communication completely avoiding interference is... ;

[0056] Drone communication increases the number of available frequency points and number of jumps This is used to reduce the probability of being continuously interfered with.

[0057] The technical effects of the above solution are as follows: Frequency hopping technology enables rapid switching of communication signals between multiple frequency points. When some frequency points are interfered with, the signal can quickly switch to an unaffected frequency point to continue communication, effectively avoiding multi-point blocking interference; the anti-interference capability of UAV communication is enhanced through frequency hopping gain. Characterization, in the total number of available frequency points or number of interference frequencies In limited situations, the success rate of avoiding interference with a single hop can be improved, and this can be achieved by increasing the number of communication hops. This can further reduce the probability of continuous interference, thereby significantly enhancing the robustness and continuity of the communication link in a dynamically changing interference environment.

[0058] By using direct sequence spread spectrum (DSS) technology, the signal energy is extended to a frequency band much larger than the original information bandwidth. At the receiving end, despreading is performed to obtain processing gain. Among them, processing gain The bandwidth of the spread spectrum signal With raw information bandwidth The ratio (usually expressed in decibels (dB)) is as follows:

[0059]

[0060] in, The chip rate of the pseudo-random code; Information bit rate;

[0061] The processing gain This is directly reflected in the improved signal-to-interference ratio (SIR) after despreading at the receiving end. Compared to the signal-to-interference ratio before despreading The following relationship exists:

[0062] (dB)

[0063] When the received signal power is much lower than the interference noise power (i.e.) (If it is a negative value), as long as After de-expansion, the true faith is obtained.

[0064] In this embodiment, a direct sequence spread spectrum design is used:

[0065] PN code: Gold code or m-sequence is preferred because it has good autocorrelation and cross-correlation properties, which are beneficial for synchronous acquisition and resistance to multiple access interference;

[0066] Spread spectrum gain: Selected based on the required interference immunity margin and data rate trade-off; for example, if the designed information rate is... =2kbps, the chip rate used When a PN code with a value of 2Mcps is spread, the processing gain is... for:

[0067] The preferred spread spectrum chip rate is 10Mcps to 30Mcps; for 1kbps command and control instructions, its processing gain can reach over 40dB, effectively combating full-band blocking interference. The specific calculation process is as follows:

[0068]

[0069] This gain means that after despreading, the effective signal power of the UAV communication is increased by 1,000 times relative to the interference power; theoretically, it can still work normally when the interference power is nearly 30 dB (about 1,000 times) higher than the signal power.

[0070] Frame structure design:

[0071] Synchronization frame: A very short frame structure containing a frame header, a precise timestamp, and parameters for the next frequency hopping / spreading (such as PN code phase offset, next frequency index, etc.).

[0072] Data frame: Based on the synchronization frame, a data payload field is added. The data can be coded with advanced channel coding (such as LDPC and Turbo codes) before spreading to further increase the gain.

[0073] The technical advantages of the above solution are as follows: by using direct sequence spread spectrum technology, the signal energy can be extended to a frequency band much larger than the original information bandwidth, and extremely high processing gain can be obtained at the receiving end by using correlation despreading. The obtained processing gain This mechanism, numerically equal to the ratio of the spread spectrum signal bandwidth to the original information bandwidth in decibels, ensures that even if the received signal power is lower than the interference noise power, resulting in a lower signal-to-interference ratio than before despreading... It is negative as long as its absolute value is less than the processing gain. Even after de-expansion, one can still obtain the true faith. This enables reliable signal extraction and recovery even in environments with strong broadband interference.

[0074] Frequency hopping and direct sequence spread spectrum (DSSS) technologies work together. Frequency hopping provides frequency diversity for DSS systems, while DSS provides anti-interference redundancy at a single frequency point for frequency hopping systems. The total anti-interference margin of the system is the sum of the gains from the two technologies.

[0075] The technical effects of the above-mentioned technical solution are as follows: the combination of frequency hopping and direct-sequence spread spectrum (DSSS) can produce a 1+1>2 effect. Frequency hopping can provide frequency diversity for the DSSS system, while DSSS provides anti-interference redundancy for the frequency hopping system at a single frequency point. Through the mutual complementarity of the two technologies, the robustness and survivability of UAV communication in complex and unknown interference environments are greatly improved. The total anti-interference tolerance of UAV communication can be approximately regarded as the superposition of the gains of the two technologies. When encountering the worst-case local broadband interference (simultaneous interference of J frequency hopping points), the UAV communication enjoys the full gain at the uninterrupted frequency points. At the interfered frequency points, although the effective gain will decrease, the frequency hopping mechanism will quickly escape the frequency point, so that the overall bit error rate performance of UAV communication is greatly improved compared with the single technology.

[0076] Both the command and control system and the drone terminal include:

[0077] The baseband processing unit is used to generate and process PN codes for spreading, as well as to spread and despread data.

[0078] The microprocessor and control unit are used to run communication protocols, generate and parse frequency hopping / spreading instructions, and manage the synchronization state machine;

[0079] Also includes:

[0080] A frequency-hopping synthesizer is a frequency-sensitive, fast-switching RF local oscillator used to switch to the frequency point specified by the frequency-hopping pattern within microseconds.

[0081] A transceiver is used to perform signal modulation, up-conversion, transmission, reception, down-conversion, and demodulation.

[0082] The operating frequency band for UAV communication is the ISM band, namely 2400-2483.5MHz and 5725-5850MHz. All frequency points of the frequency hopping pattern must fall within the ISM band. It should be noted that the ISM band may be slightly adjusted according to the regulations of different countries. The ISM band used in this solution is a commonly used range.

[0083] The technical advantages of the above solution are as follows: Efficient spread spectrum and despreading processing is achieved through the baseband processing unit; precise management of frequency hopping patterns and synchronization states by the microprocessor and control unit ensures the real-time performance and reliability of the communication link; the microsecond-level fast frequency switching capability provided by the frequency hopping synthesizer enables UAV communication to effectively avoid interference frequencies; the transceiver's flexible operation within the ISM band, combined with the frequency hopping pattern design strictly limited to the ISM band, meets regulatory requirements while fully utilizing available spectrum resources. Based on this design, a balance between anti-interference capability, environmental adaptability, and cost feasibility can be achieved with limited power consumption and hardware complexity, thereby significantly improving the communication survivability of UAVs in complex electromagnetic environments.

[0084] The frequency hopping pattern generation adopts a time-based pseudo-random frequency hopping pattern. The command and control system and the UAV use the same seed and encryption algorithm to calculate the next frequency hopping point in real time. The same seed is exchanged or pre-programmed during the initial communication handshake, and the frequency hopping rate can be adaptively adjusted according to the interference environment, with a preferred range of 500 hops / second to 2000 hops / second.

[0085] The technical effects of the above solution are as follows: by using a time-based pseudo-random frequency hopping pattern and through sharing a seed and encryption algorithm, strict synchronization and high randomness of the frequency hopping sequence are achieved, which not only ensures the accurate matching of the frequency hopping patterns of the two communicating parties, but also greatly improves the unpredictability and anti-interception capability of the frequency hopping pattern.

[0086] Step two, dynamically updating and confirming the frequency hopping pattern and spreading parameters, further includes:

[0087] Based on real-time assessment of current channel quality and interference levels, the number of frequency points and hopping period of the frequency hopping pattern are adaptively adjusted.

[0088] The spreading gain of direct sequence spread spectrum is dynamically adjusted according to changes in interference intensity.

[0089] Furthermore, by employing a key distribution-based encryption algorithm to encrypt the transmission of frequency hopping patterns and spreading parameters, the security of the parameter update process is ensured.

[0090] Meanwhile, during low-rate, low-duty-cycle communication, a differential time synchronization mechanism is introduced to compensate for clock drift by calculating the difference in timestamps between consecutive frames, and to continuously calibrate the time base of both parties.

[0091] The technical effects of the above solution are as follows: By real-time evaluation of channel quality and interference levels, the number of frequency points and hopping period of the frequency hopping pattern are adaptively adjusted, significantly improving the dynamic anti-interference capability and spectrum utilization efficiency of UAV communication in complex electromagnetic environments; the spreading gain of direct sequence spread spectrum is dynamically adjusted based on interference intensity, realizing an intelligent balance between communication resources and anti-interference requirements, ensuring link reliability under strong interference while avoiding resource waste; the use of a key distribution-based encryption algorithm to encrypt the transmission of the frequency hopping pattern and spreading parameters eliminates the possibility of parameters being stolen or tampered with, providing the highest level of security for the anti-interference strategy itself; at the same time, by introducing a differential time synchronization mechanism, the clock reference is continuously calibrated using the difference in timestamps between consecutive frames, effectively overcoming the impact of crystal oscillator drift on synchronization accuracy, ensuring long-term accurate synchronization between the frequency hopping pattern and spreading modulation, thus laying a solid time foundation for the entire anti-interference communication system while maintaining low power consumption.

[0092] In step three, the data frame undergoes forward error correction coding and interleaving before transmission. The forward error correction coding uses adaptive coding and modulation techniques to dynamically select the error correction code rate and modulation method based on real-time channel state information. The interleaving process uses a hybrid interleaving scheme that combines block interleaving and convolutional interleaving to combat sudden interference.

[0093] The technical effects of the above-mentioned technical solution are as follows: By adopting adaptive coding and modulation technology based on real-time channel state information, the error correction code rate and modulation method are dynamically selected, enabling UAV communication to intelligently balance transmission efficiency and reliability under time-varying channel conditions. This ensures high spectral efficiency under excellent channels and maintains link connectivity by enhancing error correction capabilities when the channel deteriorates. At the same time, the hybrid interleaving scheme combining block interleaving and convolutional interleaving can effectively disperse and reconstruct the distribution of various sudden errors, significantly improving the resistance to typical sudden interference.

[0094] In step four, the preset time limit is dynamically adjusted based on the reliability of the communication link and environmental interference. The adjustment strategy is based on historical communication success rates and real-time channel estimation, including:

[0095] The preset time limit is adjusted through a controller based on fuzzy logic. The controller's input variables include recent communication success rate, signal-to-noise ratio estimate, and interference detection statistics. The output is the updated synchronization interruption timeout threshold.

[0096] If extreme interference causes the handshake synchronization signal to be interrupted and triggers the process of returning to step one, then when re-initiating the handshake, the scanning and fast handshake protocol will be used preferentially on multiple preset initial frequency points to shorten the link recovery time.

[0097] The technical effects of the above solution are as follows: By using an intelligent decision-making mechanism based on a fuzzy logic controller, and integrating multi-dimensional information such as recent communication success rate, real-time signal-to-noise ratio estimation, and interference detection statistics, the preset time limit for synchronization interruption is dynamically adjusted. This enables UAV communication to accurately distinguish between transient interference and permanent link interruption, avoiding unnecessary link reconstruction overhead under instantaneous strong interference and enabling timely initiation of recovery procedures when the external environment continues to deteriorate, significantly improving the intelligence and decision-making efficiency of the communication link. At the same time, when link reconstruction is triggered by extreme interference, by using scanning and listening and fast handshake protocols on multiple preset initial frequency points, the system achieves rapid search for available channels and instantaneous locking of the optimal handshake frequency point, greatly shortening the link recovery time. Thus, even under the strongest interference environment, the system can still maintain the resilience and service continuity of communication.

[0098] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, those skilled in the art have obtained them without creative effort.

[0099] Example 1

[0100] Taking a specific command instruction issuance process as an example, the specific communication process is as follows:

[0101] 1. Initial Connection (corresponding to Step 1): After the drone is powered on, connect to the preset initial frequency. Listening on (e.g., 2412MHz). The command and control system is... Send a handshake request frame containing the current GPS time. The PN code ID used in this test, and a random number. The drone responded with a reply frame, containing... , confirmed PN code ID, and by Frequency index of the derived next synchronization frame (e.g., 2480MHz) and transition time ( +100ms). At this point, both sides... Time synchronization is completed at all times, and it is agreed that... Switching to The next communication will take place on the same frequency.

[0102] 2. Maintain synchronization (corresponding to step two): In At that moment, both sides jumped to... Frequency point. The command and control system sends a very short synchronization frame containing a new timestamp. (For fine-tuning synchronization), next random number and by The next frequency point derived from it and time This cycle continues, maintaining and updating synchronization even when there is no data.

[0103] 3. Data transmission (corresponding to step three): at a certain synchronization moment The command and control system has remote control commands to be sent. Following the current synchronization frame, it uses the current frequency within the same frequency hopping dwell time. Upon receiving the current spread spectrum parameters, the UAV immediately sends a data frame. This data frame is continuous with the synchronization frame at the physical layer and carries the actual command data. After successfully receiving, despreading, and demodulating the data, the UAV sends a data frame with acknowledgment information as a reply.

[0104] 4. Anti-interference performance:

[0105] Scenario 1 (Multi-point interference):

[0106] Assume the system is With 100 frequency hopping points, the jammer can only jam simultaneously. =20 frequency points. Therefore, the probability of single-hop communication successfully avoiding interference is 0.8. Continuous The probability of succeeding in all 5 jumps is (0.8). 5 ≈0.328, meaning there is approximately a 32.8% probability that the device is completely unaffected by these 5 jumps; while the probability of being affected by interference in all 5 consecutive jumps is extremely low, at (0.2). 5 ≈0.00032, which indicates that frequency hopping technology can effectively break continuous interference.

[0107] Scenario 2 (Full-band interference): Use the above parameters ( =30dB). Signal power before despreading. =-100dBm, interference power spectral density across the entire frequency band This makes the total interference power at the receiver... =-70dBm, then the signal-to-interference ratio before despreading is:

[0108]

[0109] The signal-to-interference ratio improved after despreading is as follows:

[0110]

[0111] Although the signal-to-interference ratio is low at 0dB, the system can still achieve low bit error rate communication by combining powerful channel coding (such as LDPC codes). This shows that the present invention can maintain the link even when the interference power is 1000 times stronger than the signal power.

[0112] 5. Link Interruption and Reconnection (corresponding to step four): If, due to extreme circumstances, N consecutive synchronization frames (N is configurable, such as 5) are lost, both parties determine that the link is interrupted. Both the control system and the UAV actively revert to their initial frequency. Then restart the initial handshake process from step one and attempt to rebuild the link.

[0113] Working principle: The initial communication handshake enables authentication and high-precision time synchronization between the command and control system and the UAV, and dynamically negotiates the frequency hopping sequence and spreading parameters, thus laying the foundation for anti-interference communication. During the no-service transmission phase, it can continuously calibrate the time reference with low-speed, low-duty-cycle communication and dynamically update the frequency hopping pattern and spreading parameters to effectively cope with clock drift and environmental changes. When there is a data transmission requirement, it sends data frames based on the latest synchronized frequency hopping point and spreading parameters using direct sequence spread spectrum modulation technology. The combination of frequency hopping and spreading mechanisms can significantly improve the anti-interference, anti-interception, and anti-detection capabilities of communication. Even in the event of communication interruption due to extreme interference, both parties can return to the initial frequency point to re-handshake, thereby quickly restoring the link and achieving highly reliable and secure UAV communication in complex electromagnetic environments.

[0114] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0115] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A UAV communication method resistant to complex electromagnetic environments and jamming interference, characterized in that, The method includes: Step 1: The command and control system and the UAV conduct an initial communication handshake on one or more pre-agreed initial frequency points. The handshake information includes identity authentication information and completes high-precision time synchronization between the two parties. At the same time, they negotiate and determine the frequency hopping frequency point sequence, frequency hopping timestamp, and pseudo-random code parameters used for direct sequence spread spectrum for the next communication. The pseudo-random code parameters include code pattern, initial phase, and spread spectrum gain. Step 2: After the initial communication handshake is completed, if there is no business data transmission, both parties maintain a necessary communication with a low rate and low duty cycle to continuously calibrate the time base of both parties and dynamically update and confirm the frequency hopping pattern and spreading parameters of the next one or more future data frames. Step 3: When the command and control system or UAV has business data to send, the data packet to be transmitted is encapsulated in a data frame. The data frame is transmitted at the physical layer following the latest synchronized frequency hopping point in Step 2, and direct sequence spread spectrum modulation is performed on the latest synchronized frequency hopping point using synchronized spread spectrum parameters to realize data exchange. Step 4: Repeat steps 2 and 3 to continuously maintain the communication link. If the handshake synchronization signal between the two parties is interrupted for more than the preset time limit due to extreme interference, the two parties shall return to step 1 and try to initiate the handshake again at the agreed initial frequency point to re-establish synchronization and restore the communication link. In this method, direct sequence spread spectrum technology is used to extend the signal energy to a frequency band much larger than the original information bandwidth. At the receiving end, despreading is performed to obtain processing gain. Among them, processing gain The bandwidth of the spread spectrum signal With raw information bandwidth The ratio is shown below: ； in, The chip rate of the pseudo-random code; Information bit rate; The processing gain This is directly reflected in the improved signal-to-interference ratio (SIR) after despreading at the receiving end. Compared to the signal-to-interference ratio before despreading The following relationship exists: (dB); When the received signal power is much lower than the interference noise power, as long as After de-expansion, the true faith is obtained.

2. The UAV communication method for resisting complex electromagnetic environments and jamming interference according to claim 1, characterized in that, In the data transmission process of step three, frequency hopping technology enables the communication signal to switch rapidly between multiple frequency points. When some frequency points are interfered with, the communication link quickly switches to an uninterrupted frequency point to continue communication, thus avoiding multi-point blocking interference. The anti-interference capability is achieved through frequency hopping gain. The characterization is as follows: Assume the total number of available frequency points is The number of frequency points that the interfering party can simultaneously interfere with is The probability that a drone communication can successfully avoid interference in one instance is: ; For a long time The probability of hopping communication completely avoiding interference is... ; Drone communication increases the number of available frequency points and number of jumps This is used to reduce the probability of being continuously interfered with.

3. The UAV communication method for resisting complex electromagnetic environments and jamming interference according to claim 1, characterized in that, Frequency hopping and direct sequence spread spectrum (DSSS) technologies work together. Frequency hopping provides frequency diversity for DSS systems, while DSS provides anti-interference redundancy at a single frequency point for frequency hopping systems. The total anti-interference margin of the system is the sum of the gains from the two technologies.

4. The UAV communication method for resisting complex electromagnetic environments and jamming interference according to claim 1, characterized in that, Both the command and control system and the drone terminal include: The baseband processing unit is used to generate and process PN codes for spreading, as well as to spread and despread data. The microprocessor and control unit are used to run communication protocols, generate and parse frequency hopping / spreading instructions, and manage the synchronization state machine; Also includes: Frequency hopping synthesizers are used to switch to the frequency specified by a frequency hopping pattern within microseconds. A transceiver is used to perform signal modulation, up-conversion, transmission, reception, down-conversion, and demodulation.

5. The UAV communication method for resisting complex electromagnetic environments and jamming interference according to claim 1, characterized in that, The operating frequency band for the UAV communication is the ISM band, namely 2400-2483.5MHz and 5725-5850MHz, and all frequency points of the frequency hopping pattern must fall within the ISM band.

6. The UAV communication method for resisting complex electromagnetic environments and jamming interference according to claim 1, characterized in that, The frequency hopping pattern generation adopts a time-based pseudo-random frequency hopping pattern. The command and control system and the UAV use the same seed and encryption algorithm to calculate the next frequency hopping point in real time. The same seed is exchanged or pre-programmed during the initial communication handshake.

7. The UAV communication method for resisting complex electromagnetic environments and jamming interference according to claim 1, characterized in that, Step two, dynamically updating and confirming the frequency hopping pattern and spreading parameters, further includes: Based on real-time assessment of current channel quality and interference levels, the number of frequency points and hopping period of the frequency hopping pattern are adaptively adjusted. The spreading gain of direct sequence spread spectrum is dynamically adjusted according to changes in interference intensity. Furthermore, the frequency hopping pattern and spreading parameters are encrypted and transmitted using a key distribution-based encryption algorithm; Meanwhile, during low-rate, low-duty-cycle communication, a differential time synchronization mechanism is introduced to compensate for clock drift by calculating the difference in timestamps between consecutive frames, and to continuously calibrate the time base of both parties.

8. The UAV communication method for resisting complex electromagnetic environments and jamming interference according to claim 1, characterized in that, In step three, the data frame undergoes forward error correction coding and interleaving before transmission. The forward error correction coding uses adaptive coding and modulation techniques to dynamically select the error correction code rate and modulation method based on real-time channel state information. The interleaving process uses a hybrid interleaving scheme that combines block interleaving and convolutional interleaving to combat sudden interference.

9. A UAV communication method resistant to complex electromagnetic environments and jamming interference according to claim 1, characterized in that, In step four, the preset time limit is dynamically adjusted based on the reliability of the communication link and environmental interference. The adjustment strategy is based on historical communication success rates and real-time channel estimation, including: The preset time limit is adjusted through a controller based on fuzzy logic. The controller's input variables include recent communication success rate, signal-to-noise ratio estimate, and interference detection statistics. The output is the updated synchronization interruption timeout threshold. If extreme interference causes the handshake synchronization signal to be interrupted and triggers the process of returning to step one, when re-initiating the handshake, the scanning and fast handshake protocol will be used preferentially on multiple preset initial frequency points to shorten the link recovery time.

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