Method and system for controlling network congestion of unmanned aerial vehicle in denial environment based on frequency spectrum detection

Abstract

The invention provides a spectrum detection-based denial environment unmanned aerial vehicle network congestion control method and system, the system is composed of a plurality of unmanned aerial vehicles and a single control station, and the method comprises the following steps: the unmanned aerial vehicles collect and generate interference sensing information and send the interference sensing information to the control station; the control station gathers the information and maintains an interference sensing information pool; the sender unmanned aerial vehicle starts data transmission and sends an interference condition detection request to the control station; the control station generates a detection result according to the information pool and the detection request, and notifies the sender of the unmanned aerial vehicle; and the unmanned aerial vehicle of the sender analyzes the detection result and performs congestion control according to the detection result, so that a congestion window adapts to available bandwidth change caused by frequent interference. According to the method, the cognitive radio technology is combined, control station cooperation is introduced, semi-adaptive congestion control with the interference sensing capacity is achieved, invalid transmission is avoided, the transmissible time period is fully utilized, the reasonable transmission rate is kept, and therefore the higher throughput and the lower packet loss rate are achieved.

Description

Technical Field

[0001] The present invention relates to the field of UAV network congestion control in a denied environment, and in particular to a UAV network congestion control method and system in a denied environment based on spectrum detection. Background Art

[0002] In recent years, drones have been widely used in civil and military fields. In the civil field, drones can be used in aerial photography, agriculture, power inspection and other fields. In the military field, military drones can undertake support tasks such as surveillance, communication, and relay, and gradually shift to undertaking main combat tasks such as firepower strikes. In the drone system roadmap published by the US military in the early 21st century, it was pointed out that drone self-organizing networks, namely drone networks, are an important research direction for future unmanned combat. Drone self-organizing networks are multi-hop, peer-to-peer, and non-central node temporary networks composed of multiple drones. The inherent characteristics and application scenarios of drone networks pose new challenges to protocol design in drone networks. For drones, the available communication resources are not abundant, and electromagnetic interference further exacerbates the problem of resource utilization. In drone networks, especially in military scenarios, due to electromagnetic interference, the frequent changes in available spectrum make it difficult for traditional congestion control methods to provide throughput that matches the actual available bandwidth.

[0003] Congestion control methods, namely congestion control protocols, are an important part of the computer network transmission layer and a key technology for adjusting the data transmission rate, aiming to balance the fairness and efficiency of the network. Traditional congestion control is an adaptive control mechanism that relies on in-band signals. Confirmation signals are necessary in-band signals, and other commonly used in-band signals include packet loss signals and round-trip delays. Traditional congestion control methods are difficult to adapt to the complexity of drone networks. In drone networks, the timeliness and reliability of in-band signals are not always guaranteed, and the assumptions on which the adaptive control mechanism relies may not necessarily hold. Therefore, traditional congestion control may cause lags or even misjudgments, so that changes in available bandwidth cannot be reflected in the sender's congestion window adjustment in a timely manner, resulting in data loss or channel idleness.

[0004] Cognitive radio is a common way to defend against electromagnetic interference attacks. This technology and related equipment are often used in military drones. Based on cognitive radio technology, drones can sense the spectrum conditions and adjust the physical layer or link layer parameters involved in transmitting radio. Cognitive radio equipment is equipped with an anti-interference control channel for transmitting control information such as spectrum sensing information. Although the control channel has limited bandwidth available, it is still reliable under interference. However, high-level protocols, including congestion control protocols, often ignore the capabilities of cognitive radio technology, related equipment, and anti-interference channels. Summary of the invention

[0005] Purpose of the invention: To address the shortcomings of existing congestion control methods, by combining cognitive radio technology and introducing control station collaboration, semi-adaptive congestion control with interference perception capability is implemented, so that the congestion window of the sender in the UAV network under periodic interference scenarios can adapt to the changes in available bandwidth caused by frequent interference.

[0006] Technical solution: To achieve the above-mentioned purpose, the present invention proposes a method and system for controlling congestion of a UAV network in a denied environment based on spectrum detection. The system consists of multiple UAVs and a single control station. The UAVs are responsible for transmitting service data and sending interference perception information and interference situation detection requests to the control station to obtain interference situation detection results, and perform congestion control accordingly. The control station is responsible for receiving interference perception information and interference situation detection requests sent from the UAVs, maintaining an interference perception information pool, detecting interference situations accordingly, and notifying the sending UAV of the detection results to assist it in performing congestion control. Specifically, the following steps are included:

[0007] (1) All drones are equipped with the following hardware modules:

[0008] (11) Wireless communication module, responsible for establishing communication links with other UAVs and control stations; this module supports two channels: a conventional channel, used for communication between UAVs, which cannot work properly when interfered with; and an anti-interference channel, used for communication between UAVs and control stations, which can still work properly when interfered with;

[0009] (12) Spectrum sensing module, responsible for real-time monitoring of the drone’s radio spectrum usage; this module can analyze whether the frequency band used is subject to periodic interference and calculate the duration of a single interference and the time interval between two interferences;

[0010] (2) All drones are equipped with the following software modules:

[0011] (21) a communication control module, responsible for implementing data sending, receiving and forwarding functions based on the wireless communication module;

[0012] (22) an interference perception information generation module, responsible for generating interference perception information based on the spectrum sensing module and the communication control module;

[0013] (23) an interference interval estimation module, responsible for generating an interference interval estimation result by combining the interference situation detection result sent from the control station and the return frame with the confirmation mark sent from the receiving drone;

[0014] (24) a congestion control module, responsible for adjusting the congestion window based on the interference situation detection result sent from the control station and the interference interval estimation result generated by the interference interval estimation module;

[0015] (3) The control station is equipped with a wireless communication module, which is responsible for establishing a communication link with the UAV and supports an anti-jamming channel that can still work normally when interfered;

[0016] (4) The control station deploys the following software modules:

[0017] (41) a communication control module, responsible for supporting data transmission and reception functions based on the wireless communication module;

[0018] (42) an interference perception information aggregation module, responsible for receiving interference perception information generated by the UAV to maintain an interference perception information pool;

[0019] (43) Interference situation detection module, responsible for responding to the interference situation detection request of the sender UAV and maintaining the transmission record table of the interference perception information pool;

[0020] (5) The method and system for controlling congestion of a UAV network in a denial environment based on spectrum detection are implemented as follows:

[0021] (51) The interference perception information generation module of the UAV generates interference perception information in real time and sends the latest interference perception information to the control station every 2 seconds;

[0022] (52) The interference perception information aggregation module of the control station receives the interference perception information and maintains the interference perception information pool to ensure that the data in the interference perception information pool can reflect the real-time status of the UAV network;

[0023] (53) The sending UAV transmits service data to the receiving UAV through the forwarding UAV, and sends an interference detection request to the control station when starting the transmission;

[0024] (54) According to the interference perception information pool and the interference situation detection request, the interference situation detection module of the control station performs interference detection every 2 seconds, maintains the interference perception information pool, and notifies the sending drone of the interference situation detection result;

[0025] (55) According to the interference situation detection result, the interference interval estimation module of the sending UAV generates an interference interval estimation result for use by the congestion control module;

[0026] (56) Based on the interference situation detection results and the interference interval estimation results, the congestion control module of the sending UAV adjusts the congestion window to avoid invalid transmission, make full use of the transmittable time period and maintain a reasonable transmission rate.

[0027] Further, regarding the interference perception information generation module in step (22), the interference perception information includes the drone number, communication participation information and spectrum perception information; the drone number is the unique identifier of the drone device; the communication participation information is the IP address pair of the sender and the receiver of the transmission in which the drone actually participates, and the spectrum perception information includes the single interference duration and the time interval between two interferences of the used frequency band; the module obtains the communication participation information based on the communication control module, and the information is recorded by the communication control module when performing the corresponding operation; the module obtains the spectrum perception information based on the spectrum perception module, and if the available frequency band of the drone is not interfered with, the single interference duration and the time interval between two interferences are set to 0.

[0028] Further, regarding the interference interval estimation module in step (23), the interference interval estimation result generated by the module is an estimation of the latest interference period in the periodic interference, which is used by the congestion control module; the working process of the module is as follows:

[0029] (231) When receiving a return frame marked as confirmation from the receiver, the module records the following time: the time when the last confirmation frame is received, the time when the latest confirmation frame is received, the time when the last largest new confirmation data packet is sent, and the time when the latest smallest lost data packet is sent; wherein the largest new confirmation data packet refers to the data packet with the largest sequence number among one or more newly confirmed data packets, and the latest smallest lost data packet refers to the data packet with the smallest sequence number among one or more recently lost data packets;

[0030] (232) When receiving the interference detection result sent from the control station, the module parses to obtain the interference indication signal and interference parameters, the interference indication signal is divided into JBGN and JEND defined in step (43), and the interference parameters include the duration of a single interference and the time interval between two interferences;

[0031] (233) If the received interference indication signal is the JBGN defined in step (43), and the difference between the receiving time of the latest confirmation frame and the receiving time of the previous confirmation frame is not less than the single interference duration, then initialize JPRD and related parameters, and execute subsequent steps (234), (235) and (236); the related parameters include: the interference start time, which is set to the average of the sending time of the last largest new confirmation data packet and the sending time of the latest minimum lost data packet; the interference end time, which is set to the interference start time plus the single interference duration; the interval minimum deviation, which is set to the difference between the sending time of the last largest new confirmation data packet and the interference start time; the interval maximum deviation, which is set to the difference between the receiving time of the latest confirmation frame and the interference end time; the start time deviation, which is set to 0; the end time deviation, which is set to 0; JPRD is the interference interval estimation result, its left endpoint is the interference start time plus the start time deviation, and its right endpoint is the interference end time plus the end time deviation;

[0032] (234) If the sending time of the latest minimum loss data packet is recorded, the start time deviation and the end time deviation are calculated to adjust the JPRD defined in step (233); the calculation method of the start time deviation and the end time deviation is: if the difference between the sending time of the latest minimum loss data packet and the interference start time is negative and not less than the interval minimum deviation, the start time deviation is set to the difference; if the difference between the sending time of the latest minimum loss data packet and the interference end time is positive and not greater than the interval maximum deviation, the end time deviation is set to the difference; if the start time deviation is not negative, its value is set by the end time deviation; if the end time deviation is not positive, its value is set by the start time deviation;

[0033] (235) If the current time is not less than the interference end time, the interference start time and the interference end time are each increased by a single interference duration to update the JPRD defined in step (233);

[0034] (236) If the received interference indication signal is the JEND defined in step (43), the JPRD and related parameters defined in step (233) are reset.

[0035] Further, regarding the congestion control module in step (24), the module is an extension of the BBR2 congestion control algorithm applicable to this system. The congestion control module extends the congestion control state machine of BBR2 into a hierarchical state machine. The original BBR2 congestion control state machine is a low-level state machine responsible for conventional congestion control. The newly extended high-level state machine is responsible for timely intervention in the low-level state machine and covers the operation of the low-level state machine to avoid invalid transmission, make full use of the transmittable time period and maintain a reasonable transmission rate. BBR2 is a classic congestion control algorithm based on a network model. The high-level state machine has three states: NORMAL, JAMMED_SEND and JAMMED_STOP, and its initial state is NORMAL. The state definition and state transition of the high-level state machine of this module are as follows:

[0036] (241) When in the NORMAL state: do not interfere with the BBR2 algorithm; if the received interference indication signal is the JBGN defined in step (43), then enter the JAMMED_SEND state defined in step (242);

[0037] (242) When in the JAMMED_SEND state: intervene in the BBR2 algorithm. If a return frame marked as confirmation is received from the receiver, and the recorded sending time of the latest minimum loss data packet belongs to the JPRD defined in step (233), then the CWND is not reduced, and CWND is the congestion window; if the current time belongs to the JPRD defined in step (233), then enter the JAMMED_STOP state defined in step (243), record LAST_CWND, LAST_CWND is the current congestion window value, and set the CWND in step (242) to 0; if the received interference indication signal is the JEND defined in step (43), then enter the NORMAL state defined in step (241);

[0038] (243) When in the JAMMED_STOP state: intervene in the BBR2 algorithm and keep the CWND defined in step (242) at 0; if the current moment does not belong to the JPRD defined in step (233), enter the JAMMED_SEND state defined in step (242), and set the CWND defined in step (242) to the LAST_CWND defined in step (242); if the received interference indication signal is the JEND defined in step (43), enter the NORMAL state defined in step (241).

[0039] Further, regarding the interference perception information aggregation module in step (42), the interference perception information pool is a database, including three tables: a transmission record table, a communication participation table and a spectrum perception table; the transmission record table includes the following fields: transmission record number, sender IP address, receiver IP address, single interference duration and time interval between two interferences, wherein the transmission record number is the auto-increment primary key of the transmission record table; the communication participation table includes the following fields: communication participation number, transmission record number and drone number, wherein the communication participation number is the auto-increment primary key of the communication participation table, and the transmission record number is a foreign key associated with the primary key of the transmission record table; the spectrum perception table includes the following fields: spectrum perception number, drone number, single interference duration and time interval between two interferences, wherein the spectrum perception number is the auto-increment primary key of the spectrum perception table; the module maintains the interference perception information pool in the following manner: if the interference perception information received by the module is not related to the record in the interference perception information pool, a new record is added, otherwise the relevant record is updated.

[0040] Further, regarding the interference situation detection module in step (43), the interference situation detection request includes an IP address pair of the sender and the receiver of the target transmission; the module detects the interference situation of the target transmission according to the interference perception information pool, generates and sends the interference situation detection result to the sender drone; the interference situation detection result includes an interference indication signal and interference parameters, the interference indication signal is divided into JBGN and JEND, and the interference parameters include a single interference duration and a time interval between two interferences, wherein J3GN is an interference start signal and JEND is an interference end signal; the workflow of the module is as follows:

[0041] (431) According to the IP address pair of the sender and the receiver of the target transmission, the module queries the transmission record table of the interference perception information pool to obtain the transmission record number of the target transmission, the historical value of the duration of a single interference, and the historical value of the time interval between two interferences;

[0042] (432) According to the transmission record number, the module queries the communication participation table of the interference perception information pool, extracts the drone numbers of all drones participating in the target transmission, and forms a drone number list;

[0043] (433) According to the list of drone numbers, the module queries the spectrum sensing table of the interference sensing information pool, extracts the single interference duration and the time interval between two interferences of the corresponding drone, and obtains the current value of the single interference duration and the current value of the time interval between two interferences of the target transmission based on the single interference duration, specifically: initialize the current value of the single interference duration and the time interval between two interferences to 0; if there is a record of a single interference duration that is not 0, set the current value of the single interference duration to the value, and set the current value of the time interval between two interferences accordingly;

[0044] (434) If the historical value of the duration of a single interference is not equal to the current value of the duration of a single interference or the historical value of the time interval between two interferences is not equal to the current value of the time interval between two interferences, then the interference situation detection result is generated and sent to the sending drone, and the transmission record table of the interference perception information pool is updated; the specific method of setting the interference situation detection result is: if the current value of the duration of a single interference is not 0, then the interference indication signal is set to JBGN defined in step (43), and the interference parameters are the current value of the duration of a single interference and the current value of the time interval between two interferences; otherwise, the interference indication signal is set to JEND defined in step (43), and the interference parameters are empty.

[0045] Beneficial effects: The present invention proposes a method and system for congestion control of drone networks in a denied environment based on spectrum detection, which realizes semi-adaptive congestion control with interference perception capability by combining cognitive radio technology and introducing control station collaboration. The present invention enables the congestion window of the sender in the drone network under periodic interference scenarios to adapt to the changes in available bandwidth caused by frequent interference, thereby improving the throughput of the drone network in the target scenario and reducing the packet loss rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the system structure of the present invention.

[0047] Figure 2 This is a flow chart of interference interval estimation of the present invention.

[0048] Figure 3 It is a schematic diagram of the congestion control state machine of the present invention.

[0049] Figure 4 This is a flow chart of interference situation detection of the present invention.

[0050] Figure 5 This is a logic diagram of the semi-physical simulation test environment of the present invention.

[0051] Figure 6 The throughput comparison chart of each method in scenario 1.

[0052] Figure 7 The following is a comparison chart of packet loss rate of each method in scenario 1.

[0053] Figure 8 The throughput comparison chart of each method in scenario 2.

[0054] Fig. 9 The following is a comparison chart of packet loss rate of each method in scenario 2.

[0055] Fig.10 The throughput comparison chart of each method in scenario 3.

[0056] Fig.11 The following is a comparison chart of packet loss rates of various methods in scenario 3. DETAILED DESCRIPTION

[0057] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0058] The specific implementation of the present invention is divided into two aspects: first, system composition; second, implementation method.

[0059] The first aspect includes the following steps: Figure 1 As shown:

[0060] The present invention proposes a method and system for controlling congestion in a UAV network in a denial environment based on spectrum detection. The system consists of multiple UAVs and a single control station. The UAV is responsible for transmitting service data and sending interference perception information and interference situation detection requests to the control station to obtain interference situation detection results, and perform congestion control accordingly. The control station is responsible for receiving interference perception information and interference situation detection requests sent from the UAV, maintaining an interference perception information pool, detecting interference situations accordingly, and notifying the sending UAV of the detection results to assist it in performing congestion control.

[0061] (1) All drones are equipped with the following hardware modules:

[0062] (11) Wireless communication module, responsible for establishing communication links with other UAVs and control stations; this module supports two channels: a conventional channel, used for communication between UAVs, which cannot work properly when interfered with; and an anti-interference channel, used for communication between UAVs and control stations, which can still work properly when interfered with;

[0063] (12) Spectrum sensing module, responsible for real-time monitoring of the drone’s radio spectrum usage; this module can analyze whether the frequency band used is subject to periodic interference and calculate the duration of a single interference and the time interval between two interferences;

[0064] (2) All drones are equipped with the following software modules:

[0065] (21) a communication control module, responsible for implementing data sending, receiving and forwarding functions based on the wireless communication module;

[0066] (22) An interference perception information generation module, responsible for generating interference perception information; the interference perception information includes the UAV number, communication participation information and spectrum perception information; the UAV number is the unique identifier of the UAV device; the communication participation information is the IP address pair of the sender and the receiver of the transmission in which the UAV actually participates, and the spectrum perception information includes the single interference duration and the time interval between two interferences of the used frequency band; the module obtains the communication participation information based on the communication control module, and the information is recorded by the communication control module when performing corresponding operations; the module obtains the spectrum perception information based on the spectrum perception module, and if the available frequency band of the UAV is not interfered with, the single interference duration and the time interval between two interferences are set to 0;

[0067] (23) An interference interval estimation module, which is responsible for generating an interference interval estimation result by combining the interference situation detection result sent from the control station and the return frame with the confirmation mark sent from the receiving drone; the result is an estimate of the latest interference period in the periodic interference, which is used by the congestion control module;

[0068] (24) Congestion control module, responsible for adjusting the congestion window in combination with the interference detection result sent from the control station and the interference interval estimation result generated by the interference interval estimation module; this module is an extension of the BBR2 congestion control algorithm applicable to this system. The congestion control module extends the congestion control state machine of BBR2 into a hierarchical state machine. The original BBR2 congestion control state machine is the low-level state machine responsible for conventional congestion control. The newly extended high-level state machine is responsible for timely intervention in the low-level state machine and covers the operation of the low-level state machine to avoid invalid transmission, make full use of the transmittable time period and maintain a reasonable transmission rate; BBR2 is a classic congestion control algorithm based on a network model; the high-level state machine has three states: NORMAL, JAMMED_SEND and JAMMED_STOP, and its initial state is NORMAL;

[0069] (3) The control station is equipped with a wireless communication module, which is responsible for establishing a communication link with the UAV and supports an anti-jamming channel that can still work normally when interfered;

[0070] (4) The control station deploys the following software modules:

[0071] (41) a communication control module, responsible for supporting data transmission and reception functions based on the wireless communication module;

[0072] (42) Interference perception information aggregation module, responsible for receiving interference perception information generated by drones to maintain an interference perception information pool; the interference perception information pool is a database, including three tables: a transmission record table, a communication participation table and a spectrum perception table; the transmission record table contains the following fields: transmission record number, sender IP address, receiver IP address, single interference duration and time interval between two interferences, where the transmission record number is the auto-increment primary key of the transmission record table; the communication participation table contains the following fields: communication participation number, transmission record number and drone number, where the communication participation number is the auto-increment primary key of the communication participation table, and the transmission record number is a foreign key associated with the primary key of the transmission record table; the spectrum perception table contains the following fields: spectrum perception number, drone number, single interference duration and time interval between two interferences, where the spectrum perception number is the auto-increment primary key of the spectrum perception table; the module maintains the interference perception information pool in the following way: if the interference perception information received by the module is irrelevant to the records in the interference perception information pool, a new record is added, otherwise the relevant records are updated;

[0073] (43) An interference situation detection module is responsible for responding to the interference situation detection request of the sending UAV and maintaining the transmission record table of the interference perception information pool; the interference situation detection request contains the IP address pair of the sender and receiver of the target transmission; the module detects the interference situation of the target transmission according to the interference perception information pool, generates and sends the interference situation detection result to the sending UAV; the interference situation detection result includes an interference indication signal and interference parameters, the interference indication signal is divided into JBGN and JEND, and the interference parameters include the duration of a single interference and the time interval between two interferences, where JBGN is the interference start signal and JEND is the interference end signal;

[0074] like Figure 2 As shown, the working process of the interference interval estimation module is as follows:

[0075] (231) When receiving a return frame marked as confirmation from the receiver, the module records the following time: the time when the last confirmation frame is received, the time when the latest confirmation frame is received, the time when the last largest new confirmation data packet is sent, and the time when the latest smallest lost data packet is sent; wherein the largest new confirmation data packet refers to the data packet with the largest sequence number among one or more newly confirmed data packets, and the latest smallest lost data packet refers to the data packet with the smallest sequence number among one or more recently lost data packets;

[0076] (232) When receiving the interference detection result sent from the control station, the module parses to obtain the interference indication signal and interference parameters, the interference indication signal is divided into JBGN and JEND defined in step (43), and the interference parameters include the duration of a single interference and the time interval between two interferences;

[0077] (233) If the received interference indication signal is the JBGN defined in step (43), and the difference between the receiving time of the latest confirmation frame and the receiving time of the previous confirmation frame is not less than the single interference duration, then initialize JPRD and related parameters, and execute subsequent steps (234), (235) and (236); the related parameters include: the interference start time, which is set to the average of the sending time of the last largest new confirmation data packet and the sending time of the latest minimum lost data packet; the interference end time, which is set to the interference start time plus the single interference duration; the interval minimum deviation, which is set to the difference between the sending time of the last largest new confirmation data packet and the interference start time; the interval maximum deviation, which is set to the difference between the receiving time of the latest confirmation frame and the interference end time; the start time deviation, which is set to 0; the end time deviation, which is set to 0; JPRD is the interference interval estimation result, its left endpoint is the interference start time plus the start time deviation, and its right endpoint is the interference end time plus the end time deviation;

[0078] (234) If the sending time of the latest minimum loss data packet is recorded, the start time deviation and the end time deviation are calculated to adjust the JPRD defined in step (233); the calculation method of the start time deviation and the end time deviation is: if the difference between the sending time of the latest minimum loss data packet and the interference start time is negative and not less than the interval minimum deviation, the start time deviation is set to the difference; if the difference between the sending time of the latest minimum loss data packet and the interference end time is positive and not greater than the interval maximum deviation, the end time deviation is set to the difference; if the start time deviation is not negative, its value is set by the end time deviation; if the end time deviation is not positive, its value is set by the start time deviation;

[0079] (235) If the current time is not less than the interference end time, the interference start time and the interference end time are each increased by a single interference duration to update the JPRD defined in step (233);

[0080] (236) If the received interference indication signal is the JEND defined in step (43), the JPRD and related parameters defined in step (233) are reset.

[0081] like Figure 3 As shown, the state definition and state transition of the high-level state machine of the congestion control module are as follows:

[0082] (241) When in the NORMAL state: do not interfere with the BBR2 algorithm; if the received interference indication signal is the JBGN defined in step (43), then enter the JAMMED_SEND state defined in step (242);

[0083] (242) When in the JAMMED_SEND state: intervene in the BBR2 algorithm. If a return frame marked as confirmation is received from the receiver, and the recorded sending time of the latest minimum loss data packet belongs to the JPRD defined in step (233), then the CWND is not reduced, and CWND is the congestion window; if the current time belongs to the JPRD defined in step (233), then enter the JAMMED_STOP state defined in step (243), record LAST_CWND, LAST_CWND is the current congestion window value, and set the CWND in step (242) to 0; if the received interference indication signal is the JEND defined in step (43), then enter the NORMAL state defined in step (241);

[0084] (243) When in the JAMMED_STOP state: intervene in the BBR2 algorithm and keep the CWND defined in step (242) as 0; if the current moment does not belong to the JPRD defined in step (233), enter the JAMMED_SEND state defined in step (242), and set the CWND defined in step (242) to the LAST_CWND defined in step (242); if the received interference indication signal is the JEND defined in step (43), enter the NORMAL state defined in step (241);

[0085] like Figure 4 As shown, the working process of the interference detection module is as follows:

[0086] (431) According to the IP address pair of the sender and the receiver of the target transmission, the module queries the transmission record table of the interference perception information pool to obtain the transmission record number of the target transmission, the historical value of the duration of a single interference, and the historical value of the time interval between two interferences;

[0087] (432) According to the transmission record number, the module queries the communication participation table of the interference perception information pool, extracts the drone numbers of all drones participating in the target transmission, and forms a drone number list;

[0088] (433) According to the list of drone numbers, the module queries the spectrum sensing table of the interference sensing information pool, extracts the single interference duration and the time interval between two interferences of the corresponding drone, and obtains the current value of the single interference duration and the current value of the time interval between two interferences of the target transmission based on the single interference duration, specifically: initialize the current value of the single interference duration and the time interval between two interferences to 0; if there is a record of a single interference duration that is not 0, set the current value of the single interference duration to the value, and set the current value of the time interval between two interferences accordingly;

[0089] (434) If the historical value of the duration of a single interference is not equal to the current value of the duration of a single interference or the historical value of the time interval between two interferences is not equal to the current value of the time interval between two interferences, then the interference situation detection result is generated and sent to the sending drone, and the transmission record table of the interference perception information pool is updated; the specific method of setting the interference situation detection result is: if the current value of the duration of a single interference is not 0, then the interference indication signal is set to JBGN defined in step (43), and the interference parameters are the current value of the duration of a single interference and the current value of the time interval between two interferences; otherwise, the interference indication signal is set to JEND defined in step (43), and the interference parameters are empty.

[0090] The second aspect includes the following steps:

[0091] (5) The method and system for controlling congestion of a UAV network in a denial environment based on spectrum detection are implemented as follows:

[0092] (51) The interference perception information generation module of the UAV generates interference perception information in real time and sends the latest interference perception information to the control station every 2 seconds;

[0093] (52) The interference perception information aggregation module of the control station receives the interference perception information and maintains the interference perception information pool to ensure that the data in the interference perception information pool can reflect the real-time status of the UAV network;

[0094] (53) The sending UAV transmits service data to the receiving UAV through the forwarding UAV, and sends an interference detection request to the control station when starting the transmission;

[0095] (54) According to the interference perception information pool and the interference situation detection request, the interference situation detection module of the control station performs interference detection every 2 seconds, maintains the interference perception information pool, and notifies the sending drone of the interference situation detection result;

[0096] (55) According to the interference situation detection result, the interference interval estimation module of the sending UAV generates an interference interval estimation result for use by the congestion control module;

[0097] (56) Based on the interference situation detection results and the interference interval estimation results, the congestion control module of the sending UAV adjusts the congestion window to avoid invalid transmission, make full use of the transmittable time period and maintain a reasonable transmission rate.

[0098] The effects of the present invention are further analyzed below based on the results of semi-physical simulation tests.

[0099] In order to evaluate the performance of the system and method proposed in the present invention in the target scenario, a semi-physical simulation test was performed using the EXata 5.1 simulator and a Raspberry Pi 4B computer. The physical equipment involved in the semi-physical simulation test includes: a general-purpose computer, two Raspberry Pi 4B computers and a switch. The three computers are connected to each other through the switch. The general-purpose computer is used to: run the EXata 5.1 simulator to provide a virtual communication environment for the Raspberry Pi computer; serve as the control station of the system, implement and deploy corresponding modules. The Raspberry Pi 4B computers are used to: one of them serves as the sender to implement and deploy corresponding modules; the other serves as the receiver to implement and deploy corresponding modules. Figure 5 As shown in the figure, two Raspberry Pi 4B computers are mapped as drones in the EXata 5.1 simulator, and data is transmitted using the virtual communication environment provided by the EXata 5.1 simulator. The interference detection module deployed in the control station directly sends the detection results to the sender through the switch. The main parameter settings involved in the semi-physical simulation test are shown in Table 1:

[0100] Table 1

[0101] parameter set up Distance between nodes 700m Number of hops between nodes 2～6 Physical layer channel frequency 2.4GHz Physical layer transmission protocol 802.11a Physical layer transmit power 33dBm Physical layer transmission data rate 48Mbps Physical layer receiving protocol 802.16 Physical layer received power -69dBm Link layer protocol 802.11 Network layer routing protocols Bellman-Ford Application layer communication time 30s

[0102] For the convenience of expression, the method and system for congestion control of UAV network in a denied environment based on spectrum detection proposed in the present invention will be referred to as JAM_CCA. The congestion control methods compared in the semi-physical simulation test include JAM_CCA, NewReno, Cubic, BBR2 and Copa. The performance indicators compared in the test are throughput and packet loss rate. The throughput is the amount of data successfully transmitted per unit time, and the packet loss rate is the proportion of data lost during the communication time to the amount of data sent. The factors considered in the test include interference duty cycle, single interference duration and number of routing hops, corresponding to three scenarios respectively.

[0103] In scenario 1, the duration of a single interference is fixed at 200 milliseconds, the number of routing hops is fixed at 4, and the interference duty cycle is 20%, 30%, 40%, 50%, and 60%. Figure 6The throughput of each method was compared. Compared with BBR2, JAM_CCA achieved 13%, 18% and 42% improvements when the interference duty cycle was 20%, 30% and 40%, respectively. Compared with JAM_CCA, BBR2 caused 68% and 77% losses when the interference duty cycle was 50% and 60%, respectively. Except for JAM_CCA, other algorithms all experienced a sharp drop in throughput after the interference duty cycle exceeded 40%. This means that JAM_CCA can achieve higher throughput under different interference duty cycles and is less affected by the increase in interference duty cycle. Figure 7 The packet loss rates of various methods are compared, and the curves of different methods all show an upward trend; although JAM_CCA also shows an upward trend, it always remains at a low level. In addition to JAM_CCA, only Copa has a relatively low packet loss rate, but there is still a certain gap with JAM_CCA; this means that JAM_CCA does not increase throughput at the cost of a higher packet loss rate, but improves throughput by making full use of communication resources.

[0104] In scenario 2, the interference duty cycle is fixed at 40%, the number of routing hops is fixed at 4, and the duration of a single interference is 200 ms, 250 ms, 300 ms, 350 ms, and 400 ms. Figure 8 The throughput of each method was compared. Compared with BBR2, JAM_CCA achieved 42%, 39%, 59%, 65% and 46% improvements when the single interference duration was 200 milliseconds, 250 milliseconds, 300 milliseconds, 350 milliseconds and 400 milliseconds, respectively; compared with other methods, JAM_CCA also has certain advantages in this scenario; this means that JAM_CCA can achieve higher throughput under different single interference durations. Fig. 9 By comparing the packet loss rates of various methods, JAM_CCA shows a certain volatility, but it is always at a low level; the curves of other methods show a downward trend, but there is always a certain gap with JAM_CCA; this means that JAMCCA can achieve a lower packet loss rate under different single interference durations.

[0105] In scenario 3, the interference duty cycle is fixed at 40%, the single interference duration is fixed at 200 milliseconds, and the number of routing hops is 2, 3, 4, 5, and 6. Fig.10 The throughput of each method was compared. Compared with BBR2, JAM_CCA achieved 23%, 22% and 42% improvement when the number of hops was 2, 3 and 4 respectively. Compared with JAM_CCA, BBR2 caused 56% and 46% loss when the number of hops was 5 and 6 respectively. When the number of hops was 2, only Copa had a slight advantage over JAM_CCA. In other cases, JAM_CCA had certain advantages over other methods. This shows that JAM_CCA can provide higher throughput at different hop numbers. Fig.11The packet loss rates of various methods are compared. The curves of NewReno and Cubic show a certain degree of volatility. The curves of BBR2, Copa, and JAM_CCA all show an upward trend. Although the curve of JAM_CCA shows an upward trend, it is always at a low level. This means that the packet loss rate achieved by JAM_CCA at different hop counts is still relatively low.

[0106] The above are only specific implementation cases of the present invention. The protection scope of the present invention includes but is not limited to the above implementation cases. All technical solutions that conform to the design ideas of the present invention belong to the protection scope of the present invention. It should be pointed out that for engineers and technicians in this technical field, several improvements and optimizations made without departing from the principles of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method and system for controlling congestion of drone networks in a denial environment based on spectrum detection, characterized in that: The system consists of multiple drones and a single control station; the drones are responsible for transmitting business data and sending interference perception information and interference situation detection requests to the control station to obtain interference situation detection results and perform congestion control accordingly; the control station is responsible for receiving interference perception information and interference situation detection requests sent from the drones, maintaining an interference perception information pool, detecting interference situations accordingly, and notifying the sending drone of the detection results to assist it in congestion control; the specific steps include: (1) All drones are equipped with the following hardware modules: (11) Wireless communication module, responsible for establishing communication links with other UAVs and control stations; this module supports two channels: a conventional channel, used for communication between UAVs, which cannot work properly when interfered with; and an anti-interference channel, used for communication between UAVs and control stations, which can still work properly when interfered with; (12) Spectrum sensing module, responsible for real-time monitoring of the drone’s radio spectrum usage; this module can analyze whether the frequency band used is subject to periodic interference and calculate the duration of a single interference and the time interval between two interferences; (2) All drones are equipped with the following software modules: (21) a communication control module, responsible for implementing data sending, receiving and forwarding functions based on the wireless communication module; (22) an interference perception information generation module, responsible for generating interference perception information based on the spectrum sensing module and the communication control module; (23) an interference interval estimation module, responsible for generating an interference interval estimation result by combining the interference situation detection result sent from the control station and the return frame with the confirmation mark sent from the receiving drone; (24) a congestion control module, responsible for adjusting the congestion window based on the interference situation detection result sent from the control station and the interference interval estimation result generated by the interference interval estimation module; (3) The control station is equipped with a wireless communication module, which is responsible for establishing a communication link with the UAV and supports an anti-jamming channel that can still work normally when interfered; (4) The control station deploys the following software modules: (41) a communication control module, responsible for supporting data transmission and reception functions based on the wireless communication module; (42) an interference perception information aggregation module, responsible for receiving interference perception information generated by the UAV to maintain an interference perception information pool; (43) Interference situation detection module, responsible for responding to the interference situation detection request of the sender UAV and maintaining the transmission record table of the interference perception information pool; (5) The method and system for controlling congestion of a UAV network in a denial environment based on spectrum detection are implemented as follows: (51) The interference perception information generation module of the UAV generates interference perception information in real time and sends the latest interference perception information to the control station every 2 seconds; (52) The interference perception information aggregation module of the control station receives the interference perception information and maintains the interference perception information pool to ensure that the data in the interference perception information pool can reflect the real-time status of the UAV network; (53) The sending UAV transmits service data to the receiving UAV through the forwarding UAV, and sends an interference detection request to the control station when starting the transmission; (54) According to the interference perception information pool and the interference situation detection request, the interference situation detection module of the control station performs interference detection every 2 seconds, maintains the interference perception information pool, and notifies the sending drone of the interference situation detection result; (55) According to the interference situation detection result, the interference interval estimation module of the sending UAV generates an interference interval estimation result for use by the congestion control module; (56) Based on the interference situation detection results and the interference interval estimation results, the congestion control module of the sending UAV adjusts the congestion window to avoid invalid transmission, make full use of the transmittable time period and maintain a reasonable transmission rate.

2. The method and system for controlling network congestion of unmanned aerial vehicles in a denied environment based on spectrum detection according to claim 1, characterized in that: Regarding the interference perception information generation module in step (22), the interference perception information includes a drone number, communication participation information, and spectrum perception information; the drone number is a unique identifier of the drone device; The communication participation information is the IP address pair of the sender and receiver of the transmission in which the drone actually participates. The spectrum sensing information includes the duration of a single interference and the time interval between two interferences in the frequency band used. This module obtains the communication participation information based on the communication control module, and the information is recorded by the communication control module when performing corresponding operations. This module obtains the spectrum sensing information based on the spectrum sensing module. If the available frequency band of the drone is not interfered with, the duration of a single interference and the time interval between two interferences are set to 0.

3. The method and system for controlling network congestion of unmanned aerial vehicles in a denied environment based on spectrum detection according to claim 1, characterized in that: Regarding the interference situation detection module in step (43), the interference situation detection request includes the IP address pair of the sender and the receiver of the target transmission; the module detects the interference situation of the target transmission according to the interference perception information pool, generates and sends the interference situation detection result to the sender drone; the interference situation detection result includes an interference indication signal and interference parameters, the interference indication signal is divided into JBGN and JEND, and the interference parameters include the duration of a single interference and the time interval between two interferences, wherein JBGN is the interference start signal and JEND is the interference end signal; the workflow of the module is as follows: (431) According to the IP address pair of the sender and the receiver of the target transmission, the module queries the transmission record table of the interference perception information pool to obtain the transmission record number of the target transmission, the historical value of the duration of a single interference, and the historical value of the time interval between two interferences; (432) According to the transmission record number, the module queries the communication participation table of the interference perception information pool, extracts the drone numbers of all drones participating in the target transmission, and forms a drone number list; (433) According to the list of drone numbers, the module queries the spectrum sensing table of the interference sensing information pool, extracts the single interference duration and the time interval between two interferences of the corresponding drone, and obtains the current value of the single interference duration and the current value of the time interval between two interferences of the target transmission based on the single interference duration, specifically: initialize the current value of the single interference duration and the time interval between two interferences to 0; if there is a record of a single interference duration that is not 0, set the current value of the single interference duration to the value, and set the current value of the time interval between two interferences accordingly; (434) If the historical value of the duration of a single interference is not equal to the current value of the duration of a single interference or the historical value of the time interval between two interferences is not equal to the current value of the time interval between two interferences, then the interference situation detection result is generated and sent to the sending drone, and the transmission record table of the interference perception information pool is updated; the specific method of setting the interference situation detection result is: if the current value of the duration of a single interference is not 0, then the interference indication signal is set to JBGN defined in step (43), and the interference parameters are the current value of the duration of a single interference and the current value of the time interval between two interferences; otherwise, the interference indication signal is set to JEND defined in step (43), and the interference parameters are empty.

4. The method and system for controlling the network congestion of unmanned aerial vehicles in a denied environment based on spectrum detection and the interference detection module thereof according to claim 1 and claim 3 are characterized in that: Regarding the interference interval estimation module in step (23), the interference interval estimation result generated by the module is an estimation of the latest interference period in the periodic interference, which is used by the congestion control module; the working process of the module is as follows: (231) When receiving a return frame marked as confirmation from the receiver, the module records the following time: the time when the last confirmation frame is received, the time when the latest confirmation frame is received, the time when the last largest new confirmation data packet is sent, and the time when the latest smallest lost data packet is sent; wherein the largest new confirmation data packet refers to the data packet with the largest sequence number among one or more newly confirmed data packets, and the latest smallest lost data packet refers to the data packet with the smallest sequence number among one or more recently lost data packets; (232) When receiving the interference detection result sent from the control station, the module parses to obtain the interference indication signal and interference parameters, the interference indication signal is divided into JBGN and JEND defined in step (43), and the interference parameters include the duration of a single interference and the time interval between two interferences; (233) If the received interference indication signal is the JBGN defined in step (43), and the difference between the receiving time of the latest confirmation frame and the receiving time of the previous confirmation frame is not less than the single interference duration, then initialize JPRD and related parameters, and execute subsequent steps (234), (235) and (236); the related parameters include: the interference start time, which is set to the average of the sending time of the last largest new confirmation data packet and the sending time of the latest minimum lost data packet; the interference end time, which is set to the interference start time plus the single interference duration; the interval minimum deviation, which is set to the difference between the sending time of the last largest new confirmation data packet and the interference start time; the interval maximum deviation, which is set to the difference between the receiving time of the latest confirmation frame and the interference end time; the start time deviation, which is set to 0; the end time deviation, which is set to 0; JPRD is the interference interval estimation result, its left endpoint is the interference start time plus the start time deviation, and its right endpoint is the interference end time plus the end time deviation; (234) If the sending time of the latest minimum loss data packet is newly recorded, the start time deviation and the end time deviation are calculated to adjust the JPRD defined in step (233); the calculation method of the start time deviation and the end time deviation is: if the difference between the sending time of the latest minimum loss data packet and the interference start time is negative and not less than the interval minimum deviation, the start time deviation is set to the difference; if the difference between the sending time of the latest minimum loss data packet and the interference end time is positive and not greater than the interval maximum deviation, the end time deviation is set to the difference; if the start time deviation is not negative, its value is set by the end time deviation; if the end time deviation is not positive, its value is set by the start time deviation; (235) If the current time is not less than the interference end time, the interference start time and the interference end time are each increased by a single interference duration to update the JPRD defined in step (233); (236) If the received interference indication signal is the JEND defined in step (43), the JPRD and related parameters defined in step (233) are reset.

5. The method and system for controlling network congestion of unmanned aerial vehicles in a denied environment based on spectrum detection according to claim 1, characterized in that: Regarding the congestion control module in step (24), this module is an extension of the BBR2 congestion control algorithm applicable to this system. The congestion control module extends the congestion control state machine of BBR2 into a hierarchical state machine. The original BBR2 congestion control state machine is a low-level state machine responsible for conventional congestion control. The newly extended high-level state machine is responsible for timely intervention in the low-level state machine and covers the operation of the low-level state machine to avoid invalid transmission, make full use of the transmittable time period and maintain a reasonable transmission rate. BBR2 is a classic congestion control algorithm based on a network model. The high-level state machine has three states: NORMAL, JAMMED_SEND and JAMMED_STOP, and its initial state is NORMAL. The state definition and state transition of the high-level state machine of this module are as follows: (241) When in the NORMAL state: do not interfere with the BBR2 algorithm; if the received interference indication signal is the JBGN defined in step (43), then enter the JAMMED_SEND state defined in step (242); (242) When in the JAMMED_SEND state: intervene in the BBR2 algorithm. If a return frame marked as confirmation is received from the receiver, and the recorded sending time of the latest minimum loss data packet belongs to the JPRD defined in step (233), then the CWND is not reduced, and CWND is the congestion window; if the current time belongs to the JPRD defined in step (233), then enter the JAMMED_STOP state defined in step (243), record LAST_CWND, LAST_CWND is the current congestion window value, and set the CWND in step (242) to 0; if the received interference indication signal is the JEND defined in step (43), then enter the NORMAL state defined in step (241); (243) When in the JAMMED_STOP state: intervene in the BBR2 algorithm and keep the CWND defined in step (242) at 0; if the current moment does not belong to the JPRD defined in step (233), enter the JAMMED_SEND state defined in step (242), and set the CWND defined in step (242) to the LAST_CWND defined in step (242); if the received interference indication signal is the JEND defined in step (43), enter the NORMAL state defined in step (241).

6. The method and system for controlling network congestion of unmanned aerial vehicles in a denied environment based on spectrum detection according to claim 1, characterized in that: Regarding the interference perception information aggregation module in step (42), the interference perception information pool is a database, including three tables: a transmission record table, a communication participation table and a spectrum perception table; the transmission record table includes the following fields: transmission record number, sender IP address, receiver IP address, single interference duration and time interval between two interferences, wherein the transmission record number is the auto-increment primary key of the transmission record table; the communication participation table includes the following fields: communication participation number, transmission record number and drone number, wherein the communication participation number is the auto-increment primary key of the communication participation table, and the transmission record number is a foreign key associated with the primary key of the transmission record table; the spectrum perception table includes the following fields: spectrum perception number, drone number, single interference duration and time interval between two interferences, wherein the spectrum perception number is the auto-increment primary key of the spectrum perception table; the module maintains the interference perception information pool in the following manner: if the interference perception information received by the module is irrelevant to the record in the interference perception information pool, a new record is added, otherwise the relevant record is updated.

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