Hybrid multiple access method

Abstract

The invention discloses a hybrid multiple access method which comprises the following steps: constructing an unmanned aerial vehicle cluster networking system which comprises an unmanned aerial vehicle cluster network; an unmanned aerial vehicle sending node in an unmanned aerial vehicle cluster network divides channel resource contention and a data packet receiving and transmitting process according to a unified clock, and channel time domain resources are divided into a control channel time interval (CCHI) stage and a service channel time interval (SCHI) stage through time division multiplexing; wherein in the CCHI stage, service channel resource negotiation is performed according to a preset MAC protocol frame structure, time-frequency multiplexing access is performed on a shared service channel, and preliminary hybrid multiple access is completed; the SCHI stage is used for sending a data packet; the unmanned aerial vehicle sending node increases the length of an avoidance window of the unmanned aerial vehicle sending node in the next round according to a preset backoff process in the service channel access process on the premise that a to-be-sent data packet does not suddenly change if the unmanned aerial vehicle sending node encounters the collision conflict of the data packet on the premise that the to-be-sent data packet does not suddenly change; and if the sending is smooth, reducing the length of the receding window.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and particularly relates to a hybrid multiple access method, which is applicable to multi-user access control with priority differentiation, high throughput, and low latency requirements in high-density networking scenarios. Background Art

[0002] Due to network characteristics such as high mobility, self-organization, flexibility, scalability, and the ability to quickly deploy a network, unmanned aerial vehicle (UAV) cluster networks are widely used in multiple fields, mainly including emergency communication, disaster search, farmland monitoring, remote sensing, wildfire monitoring, traffic monitoring, freight transportation, and relaying. At present, the main problem in the research of UAV cluster network MAC protocols is the reasonable and efficient allocation of channel resources among multiple UAV nodes to ensure normal communication between nodes.

[0003] Through in-depth research on the current UAV MAC layer protocol research field and comparison of the performance of representative protocols, and aiming at the problems of high latency, low network topology robustness, and poor QoS (Quality of Service) support ability existing in current UAV cluster networking, the present invention proposes a task-priority-driven hybrid MAC protocol for UAV networking service scenarios with high-dynamic and high-reliable requirements, so as to ensure high network topology scalability, strong anti-destruction ability, stable throughput, and low average network latency.

[0004] A method to efficiently improve the robustness of UAV cluster networks and achieve service differentiation is to multiplex shared wireless channel slices. Time-division multiple access (TDMA) divides the channel communication time into multiple time slots, and each node accesses the channel in different time slots to achieve conflict-free multi-point communication on the same frequency. Frequency-division multiple access (FDMA) divides the channel communication frequency band into multiple sub-bands, and each node uses different sub-bands for wireless communication to achieve conflict-free multi-point communication at the same time. Different from traditional fixed time-frequency multiplexing, dynamic multi-dimensional communication resource multiplexing improves network throughput and has better processing ability for sudden changes in network traffic. Therefore, the hybrid MAC protocol designed in the present invention aims at the problem of dynamic time-frequency multiplexing access.

[0005] One of the core research points of communication systems is Multiple Access Control (MAC) technology. In the network protocol stack, the MAC protocol acts above the physical layer. By means of channel partitioning, time slot control, frame structure design, etc., it directly determines the allocation of limited communication resources in the communication area and the sending and receiving processes of information. Introducing a multi-dimensional communication resource reuse mechanism into the UAV cluster network can bring a new channel access mechanism to the UAV network. Adding service payload differentiation improves the network's heterogeneous traffic processing ability. At the same time, it is also urgent to design a MAC protocol adapted to it. Compared with existing MAC protocols, the MAC protocol based on multi-dimensional communication resource reuse takes into account the allocation problems of different-dimensional channels. In addition, the MAC with payload differentiation needs to balance the packet service priority and the fairness of self-organizing network nodes, so as to obtain better delay performance than using the DCF mechanism in the UAV cluster communication scenario and improve the communication service quality of users. Summary of the Invention

[0006] The purpose of the present invention is to provide a hybrid multiple access method to further optimize the communication service quality of the QoS support type in the UAV cluster network.

[0007] To achieve the above task, the present invention adopts the following technical solutions:

[0008] A hybrid multiple access method includes:

[0009] Construct a UAV cluster networking system, which includes a UAV cluster network;

[0010] UAV sending nodes in the UAV cluster network divide the channel resource contention and the process of packet sending and receiving according to a unified clock, and time-division multiplex the channel time-domain resources into a control channel time interval CCHI stage and a service channel time interval SCHI stage; among them, in the CCHI stage, service channel resource negotiation is carried out according to a preset MAC protocol frame structure, and time-frequency multiplexing access is used to share the service channel to complete preliminary hybrid multiple access; the SCHI stage is used to send packets;

[0011] When the UAV sending node accesses the service channel, according to a preset backoff process, on the premise that the packet to be sent does not change suddenly, if the UAV sending node encounters a collision conflict of the packet, the backoff window length of the UAV sending node is increased in the next round; if the sending is successful, the backoff window length is reduced.

[0012] Furthermore, a dynamic transmission buffer is designed for the UAV sending node: when the UAV sending node needs to send data packets, the data packets are sequentially placed into the finite-length transmission buffer in the internal storage of the UAV sending node; the data queue in the transmission buffer follows the first-in-first-out principle. When there are multiple data packets for the same UAV receiving node, the data queue is dynamically adjusted to arrange these data packets consecutively; among them, when arranging the data packets consecutively, the position of the data packet that is sent to the UAV receiving node first remains unchanged, and the remaining data packets are arranged in order with this data packet as the queue head.

[0013] Furthermore, the preset MAC protocol frame structure includes RTS_CMC frame, CB frame, and CB -1 frame;

[0014] Based on the existing control information frame RTS, the RTS_CMC frame adds a field for the number of data packets to be sent to describe the queuing situation of data packets in the transmission buffer of the UAV sending node. In addition, the information gain describes the task priority and waiting delay of data packets in the transmission buffer of the UAV sending node;

[0015] CB frame and CB -1 frame are used for the CCHI stage announcement of the UAV receiving node; the CB frame structure includes a control frame, duration, CCHI announcement time, UAV receiving node ID, time slot index information, and frame check sequence; the structure of the CB -1 frame is basically the same as that of the CB frame, and the only difference is that the CB -1 frame does not contain the time slot index information field.

[0016] Furthermore, in the CCHI stage, service channel resource negotiation is carried out according to the preset MAC protocol frame structure, and time-frequency multiplexing access is used to share the service channel to complete the preliminary hybrid multiple access, including:

[0017] At the beginning of each CCHI stage, the UAV receiving node broadcasts the CB -1 frame on the control channel, and uses the UAV receiving node ID and CCHI announcement time fields carried in it to ensure that the corresponding UAV sending node receives the CB frame; after receiving the CB -1 frame, the UAV sending node learns the start time of the CCHI stage of the UAV receiving node through the CCHI announcement time, and learns the duration of this CCHI stage through the duration field; the UAV sending node sends an RTS_CMC frame to the UAV receiving node to compete for the corresponding service channel communication resources;

[0018] At the end of the CCHI phase, the UAV receiving node broadcasts and sends a CB frame on the control channel. The time slot index information in the CB frame is used to inform the UAV sending node of the corresponding SCHI time slot allocation. The UAV sending node that obtains the time slot allocation adjusts its transmitter and sends data packets based on the TDMA mechanism in the corresponding time slot; the UAV sending node that does not obtain the time slot allocation adjusts its own waiting delay and turns off the transmitter until the receiver receives the next round of CB frames from the UAV receiving node. -1 frame.

[0019] Furthermore, the UAV sending node sends an RTS_CMC frame to the UAV receiving node through an improved CSMA / CA mechanism to compete for the communication resources of the corresponding service channel; the improved CSMA / CA mechanism is as follows:

[0020] The improved CSMA / CA mechanism abandons the traditional four-step handshake and directly puts the information gain into the handshake request frame, that is, the RTS_CMC frame, simplifying the channel access request process to a request-response two-step handshake;

[0021] In the CCHI phase, all UAV nodes remain in a state of listening and conflict avoidance preparation. Before sending the RTS_CMC frame, a short inter-frame spacing length of channel listening is performed on the control channel. If the control channel is idle during the listening process, the request process is started; if a collision occurs, the backoff process is started;

[0022] If the UAV sending node receives the ACK information sent by the UAV receiving node, it is considered that the competition is successful, and it waits for the CB frame broadcast at the end of the CCHI phase to notify the corresponding time slot;

[0023] The UAV node that competes and successfully obtains the SCHI time slot in the CCHI phase will send data packets in the order of the time slots.

[0024] Furthermore, the information gain of the UAV sending node in the CCHI phase is defined as G I , and for all UAV sending nodes competing for the service channel in one round of the SCHI phase, time slot allocation is performed according to the size of the corresponding information gain; that is, the larger the information gain, the more time slots are allocated;

[0025] The specific calculation method of the information gain is as follows:

[0026] G I =σP + θT wait +λF contin

[0027] In the above formula, P represents the packet task priority, T wait represents the packet waiting time, F contin represents the number of data packets to be sent by the node, and σ, θ, and λ respectively represent P, Twait and F contin The corresponding weight factor.

[0028] Furthermore, the priority of the data packet task is as follows: two types of task priorities, high and low, are set for the data packet. The high priority represents the dynamic information collected by the UAV and the data packet supported by the QoS specified by the upper-layer service, while the low priority represents the static data collected by the UAV and the data packet without QoS support specified by the upper-layer service; the high priority is 1 and the low priority is 0.

[0029] The waiting time of the data packet is as follows: when the data packet enters the sending buffer of the UAV sending node, a waiting timer is started; if there are multiple data packets, the waiting timer points to the first data packet to be sent; if the data packet is successfully sent, the corresponding waiting timer is reset to zero. If the data packet still fails to be sent after passing through the corresponding time slots in the i-th round of the CCHI phase, the waiting timer counts the waiting round i as the waiting time of the data packet.

[0030] The number of data packets to be sent by the node is the number of data packets in the sending buffer of the UAV sending node.

[0031] Furthermore, according to the preset backoff process, on the premise that the data packet to be sent does not mutate, if the UAV sending node encounters a collision conflict of the data packet, the backoff window length of the UAV sending node is increased in the next round; if the data packet is successfully sent, the backoff window length is decreased, including:

[0032] Assign an initial value to the backoff window of the UAV node; if a collision occurs, the backoff window length of the UAV node is doubled in the next round; if the data packet is successfully sent and the current backoff window length is greater than or equal to twice the initial backoff window length, the backoff window length of the UAV node is halved in the next round; if it is less than twice the initial backoff window length, the backoff window length of the UAV node is decreased by 1 in the next round.

[0033] A terminal device, including a processor, a memory, and a computer program stored in the memory; when the processor executes the computer program, the hybrid multiple access method is implemented.

[0034] A computer-readable storage medium, in which a computer program is stored; when the computer program is executed by a processor, the hybrid multiple access method is implemented.

[0035] Compared with the prior art, the present invention has the following technical features:

[0036] In the solution of the present invention, by designing the MAC time frame structure and protocol process, service differentiation and channel multiplexing are completed, the channel utilization rate is improved, and the probability of data packet collision is reduced, thereby realizing the improvement of the communication service quality of the QoS support type in the UAV cluster network. Description of the Drawings

[0037] Figure 1 It is a model diagram of the UAV cluster networking system;

[0038] Figure 2 It is a schematic diagram of link conflict;

[0039] Figure 3 It is a schematic diagram of the dynamic transmission buffer;

[0040] Figure 4 It is the RTS_CMC frame structure diagram;

[0041] Figure 5 It is the CB frame structure diagram;

[0042] Figure 6 It is the CCHI phase time diagram;

[0043] Figure 7 It is the SCHI time slot allocation diagram;

[0044] Figure 8 It is the general protocol flow chart;

[0045] Figure 9 It is the comparison of the average delay of data packets in the network with the existing protocol in an embodiment of the present invention;

[0046] Figure 10 It is the comparison of the network normalized throughput with the existing protocol in an embodiment of the present invention. Specific implementation manners

[0047] The present invention provides a hybrid multiple access method, which is a task priority-driven multi-channel hybrid multiple access control (MAC) protocol for a UAV (Unmanned Arial Vehicle, UAV) cluster network; first, a UAV cluster networking system is established, then a corresponding MAC time frame structure and time slot allocation scheme are designed, and the CSMA / CA mechanism backoff window is adjusted during the operation of the access method to complete adaptive backoff; simulation verification is carried out according to the delay and throughput calculation methods in the networking system. This application is applicable to high-density UAV cluster networking and has good QoS support, delay performance, and throughput performance.

[0048] The specific steps of the method of the present invention are as follows:

[0049] Step 1, construct a UAV cluster networking system; the system includes a ground base station, a UAV cluster network, and a data center; among them, the UAV cluster network is formed based on the OSI seven-layer model.

[0050] Considering the important roles of the UAV cluster network in information collection and communication relay in the field of Internet of Things applications in actual production, the present invention proposes a high-dynamic UAV cluster networking system:

[0051] In the system, the UAVs have the data transceiver capabilities of communicating with the ground base station and with the UAVs within the UAV network. They obtain time synchronization through the GPS positioning system carried on the UAVs and upload data such as coordinates, speed, and direction information to the data center; the system model is as Figure 1 shown.

[0052] As the density of the UAV network increases and the data packet traffic increases, data packet collisions, that is, link conflicts, will inevitably occur; the link conflict is as Figure 2 shown. In the same time slot, the UAV node C needs to receive two data packets sent by the UAV nodes B and D, while B needs to send different data packets to the two UAV nodes A and C, so data packet collision problems will inevitably occur. Denote the UAV node that sends data packets as the UAV sending node, and the UAV node that receives data packets as the UAV receiving node.

[0053] To solve the transmission conflict, the present invention designs a dynamic transmission buffer for the UAV sending node: when the UAV sending node needs to send a data packet, the data packet is sequentially placed in the limited-length transmission buffer in the internal storage of the UAV sending node; the data queue in the transmission buffer adopts the first-in-first-out (FIFO) method. When there are data packets for the same UAV receiving node, the data queue is dynamically adjusted to arrange these data packets continuously together, so that the data packets for the same UAV receiving node are sent continuously, avoiding repeated channel resource requests; among them, when arranging the data packets continuously, the position of the data packet that is sent to the UAV receiving node first remains unchanged, and the remaining data packets are arranged in order with this data packet as the head of the queue.

[0054] As Figure 3 shown, before the adjustment, a certain UAV sending node needs to make two channel resource requests when sending two data packets to the UAV receiving node A; after the adjustment using the strategy of the present invention, the UAV sending node can negotiate the channel resources for two data packets at one time, reducing the network channel resource negotiation time. The limited length of the transmission buffer avoids the problem that the data packets for different UAV receiving nodes are blocked and cannot be sent.

[0055] Step 2: The drone sending nodes in the drone cluster network divide the channel resource contention and the data packet transceiver process according to a unified clock, and time-division multiplex the channel time domain resources into a control channel time interval CCHI phase and a service channel time interval SCHI phase. Among them, in the CCHI phase, service channel resource negotiation is carried out according to the preset MAC protocol frame structure, and time-frequency multiplexing access is used to share the service channel to complete the initial hybrid multiple access. The SCHI phase is used to send data packets.

[0056] The present invention adopts a hybrid protocol structure to divide the channel resource contention and the data packet transceiver process, that is, the control channel time interval (CCHI, Control Channel Interval) phase is used to transmit control information, and the service channel time interval (SCHI, Service Channel Interval) phase is used to transmit data packets.

[0057] (1) RTS_CMC frame.

[0058] Considering the service differentiation characteristics of data packets with different task priorities, the present invention constructs an RTS_CMC frame, which is applicable to the drone sending node to initiate a service channel resource application to the drone receiving node. As Figure 4 shown, the RTS_CMC frame structure includes: a control frame, a duration, a receiving address, a sending address, the number of data packets to be sent, an information gain, and a frame check sequence.

[0059] Based on the existing control information frame RTS, the RTS_CMC frame adds a field of the number of data packets to be sent with a length of 1 byte to describe the queuing situation of data packets in the sending buffer of the drone sending node, so as to facilitate the drone sending node to allocate continuous SCHI time slots for continuous data packet sending on the premise that the service channel capacity is sufficient. In addition, the added information gain with a length of 1 byte describes the task priority and waiting delay of the data packets in the sending buffer of the drone sending node, so as to facilitate the drone sending node to arrange the data packets with high task priority and large waiting delay to be sent first in the SCHI phase.

[0060] (2) CB frame and CB -1 frame.

[0061] In this solution, a CB frame and a CB -1 frame are designed for the announcement of the drone receiving node in the CCHI phase. As Figure 5 shown in the CB frame structure, the CB frame structure includes a control frame, a duration, a CCHI announcement time, a drone receiving node ID, time slot index information, and a frame check sequence.

[0062] CB -1The structure of the frame is basically the same as that of the CB frame, except that -1 The frame does not contain the "time slot index information" field.

[0063] (3) Channel access mechanism.

[0064] At the beginning of each CCHI phase, the drone receiving node performs CB on the control channel. -1 The frame is broadcasted, and the drone receiving node ID and CCHI announcement time field carried in it are used to ensure that the corresponding drone sending node receives the CB frame; the drone sending node receives the CB -1 After the frame, the start time of the CCHI phase of the drone receiving node is known through the CCHI announcement time, and the duration of the CCHI phase is known through the "duration" field; the drone sending node sends the RTS_CMC frame to the drone receiving node through the improved CSMA / CA mechanism to compete for the corresponding service channel communication resources.

[0065] At the end of the CCHI phase, the drone receiving node broadcasts the CB frame on the control channel. The time slot index information in the CB frame is used to inform the drone sending node of the corresponding SCHI time slot allocation. The drone sending node that obtains the time slot allocation adjusts the transmitter and sends data packets based on the TDMA mechanism in the corresponding time slot; the drone sending node that does not obtain the time slot allocation adjusts its own waiting delay and turns off the transmitter until the receiver receives the next round of CB from the drone receiving node. -1 Frame, such as Figure 6 shown.

[0066] Among them, the improved CSMA / CA mechanism abandons the traditional four-step handshake and directly puts the information gain into the handshake request frame, namely the RTS_CMC frame, simplifying the channel access request process into a request-response two-step handshake.

[0067] In the CCHI phase, all drone nodes maintain a monitoring and conflict avoidance preparation state. Before sending the RTS_CMC frame, they monitor the control channel for a short inter-frame interval (SIFS) length. If the control channel is idle during the monitoring process, the request process is started. If there is a collision, the backoff process is started, thereby requesting channel resources with minimal overhead while avoiding collisions in requesting data packets.

[0068] If the drone sending node receives the ACK information sent by the drone receiving node, it is considered that the competition is successful and waits for the corresponding time slot of the CB frame broadcast notification at the end of the CCHI stage.

[0069] The length of the SCHI stage is determined by the number of transmitting nodes that have successfully competed in the CCHI stage. The UAV nodes that have competed and successfully obtained SCHI time slots in the CCHI stage will send data packets according to the time slot sequence as Figure 7 shown in the process and receive ACK acknowledgments; the complete protocol process of the present invention is as Figure 8 shown.

[0070] (4) Time slot allocation scheme.

[0071] The information gain reserved in the RTS_CMC frame takes the maximization of the information gain within the range of neighbor nodes as the optimization function, and the calculation of the information gain involves factors such as the task priority corresponding to the data packet, the waiting time of the data packet, and the number of data packets to be sent by the node.

[0072] Data packet task priority: For the UAV network topology based on high-dynamic networking and the service scenario oriented to information collection, two types of task priorities, high and low, are set for the data packets. High priority represents the dynamic information collected by the UAV and the data packets supported by QoS specified by the upper-layer service, while low priority represents the static data collected by the UAV and the data packets without QoS support specified by the upper-layer service; the numerical representation corresponding to the task priority: high priority is 1, low priority is 0. In the present invention, the expansion of the types of task priorities is supported, that is, changing the priority factor to enter the information gain calculation; the present invention incorporates the task priority into the channel resource allocation standard, and preferentially allocates the limited channel resources to the high-priority data packets for data transmission.

[0073] Data packet waiting time: When a data packet enters the transmission buffer of the UAV transmitting node, a waiting timer is started (if there are multiple data packets, the waiting timer points to the first data packet to be sent). If the data packet is successfully sent, the corresponding waiting timer is reset to zero. If the data packet still has not been completely sent after passing through the corresponding time slots in the i-th CCHI stage, the waiting timer counts the waiting round i as the data packet waiting time; when the UAV receiving node makes a channel resource allocation decision, SCHI time slots should be preferentially allocated to the data packets with a larger waiting delay to ensure the rapid transmission of the data packet and avoid timeout of the corresponding upper-layer service, thereby affecting the overall service quality.

[0074] Number of data packets to be sent by the node: It is found that when there are multiple data packets with an immediate transmission requirement at the same UAV transmitting node, without interrupting the UAV channel access, the MAC protocol that continuously sends data packets has relatively excellent throughput and delay performance during operation; therefore, the number of data packets to be sent is incorporated into the information gain calculation. On the premise that the channel capacity allows and the channel competition in the CCHI is successful, multiple data packets of the same node are continuously sent in multiple consecutive time slots in a round of the SCHI stage.

[0075] In summary, the information gain in the CCHI phase of the UAV sending node is defined as G I , and in one round of the SCHI phase, for all UAV sending nodes competing for service channels, time slots are allocated according to the magnitude of the corresponding information gain; that is, the greater the information gain, the higher the task priority of the data packets in the sending buffer of the corresponding sending node and the longer the waiting delay, so the more time slots are allocated. The specific calculation method of the information gain is as follows:

[0076] G I =σP + θT wait +λF contin

[0077] In the above formula, P represents the data packet task priority, T wait represents the data packet waiting time, F contin represents the number of data packets to be sent by the node, and σ, θ, and λ respectively represent the weight factors corresponding to P, T wait and F contin corresponding.

[0078] After experimental parameter tuning, σ = 0.6, θ = 0.3, λ = 0.1, and the high-dynamic UAV network with task priority differentiation has better delay and throughput performance.

[0079] Step 3, the UAV sending node follows the backoff process in the improved CSMA / CA mechanism during the service channel access process. On the premise that the data packets to be sent do not mutate, if the UAV node encounters a collision of data packets, the UAV node predicts that the collision probability of the next time slot is relatively large, and thus increases the backoff window maximum value to increase the backoff time of the UAV node; if the UAV node successfully sends, the UAV node predicts that the collision probability of the next time slot is relatively small, and thus reduces the backoff window maximum value to reduce the backoff time of the node; this mechanism improves the channel utilization rate and the throughput of the UAV cluster network without increasing the node collision probability.

[0080] The present invention completes the data packet transceiver by competing for channel resources in the improved CSMA / CA mechanism; the maximum value of the backoff window in the improved CSMA / CA mechanism changes elastically, and an adaptive multiplicative decrease backoff strategy is added on the basis of referring to the MIAD (Multiplicative Increase Additive Decrease) algorithm to adapt to the sharp increase or decrease in the total number of free nodes during the operation of the protocol due to dynamic factors such as the access of UAVs outside the network, the withdrawal of UAVs inside the network, and free nodes becoming cluster-related nodes, and adapts to the high-dynamic characteristics of the network.

[0081] Assign an initial value to the backoff window of the UAV node; if a collision occurs, the length of the backoff window of the UAV node doubles in the next round; if the transmission is successful and the current backoff window length is greater than or equal to twice the initial backoff window length, the length of the backoff window of the UAV node is halved in the next round; if it is less than twice the initial backoff window length, the length of the backoff window of the UAV node decreases by 1 in the next round.

[0082]

[0083] In the above formula, the backoff window length of the node in the i-th round is CW max_i , and the initial value of the backoff window is CW max_init ; collision indicates the existence of a conflict, and send successfully indicates a successful transmission.

[0084] While ensuring the elastic change of the backoff window to adapt to the high dynamic characteristics of the network traffic load, the adaptive backoff window length design avoids the excessive contraction or expansion of the backoff window due to traffic mutations, thereby causing unnecessary backoff waiting time or collision conflicts, and ensuring the stability of the overall network operation.

[0085] Example:

[0086] Regarding the system delay performance, this scheme defines T delay to represent the average delay of data packets in the UAV cluster network, and the specific calculation method is as follows:

[0087]

[0088] In the above formula, N data represents the total number of data packets sent during the operation of the UAV cluster network, T Send_ready_i represents the time when the i-th (1 ≤ i ≤ N data ) data packet enters the internal buffer of the corresponding UAV sending node, and T Ack_i represents the reception confirmation time when the UAV sending node receives the i-th data packet.

[0089] Regarding the system throughput, this scheme defines Th as the normalized throughput of the UAV cluster network, and the specific calculation method is as follows:

[0090]

[0091] In the above formula, N CH represents the total number of channels in the UAV cluster network, T data_i (1 ≤ i ≤ N CH ) represents the total duration of the i-th channel in the data packet transmission state, and T running_i (1 ≤ i ≤ N CH ) represents the total operation duration of the i-th channel.

[0092] See Figure 9 , through simulation verification, by isolating channel resource contention and data packet transmission and reception, the method realizes that the average delay T of data packets in the network delay is always less than one-third of that of the classical ad hoc network MAC access method, i.e., 802.11DCF. And by avoiding the accumulation of collision conflicts and the long-term backoff waiting of nodes, the additive growth of network data packet delay is reduced, improving the communication efficiency of network nodes.

[0093] See Figure 10 , through simulation verification, by means of a new control frame structure, the method realizes that the normalized throughput Th of the network is greater than that of 802.11DCF by about 8%, improving the utilization efficiency of channel resources.

[0094] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A hybrid multiple access method, characterized in that: include: Build a drone cluster networking system, which includes a drone cluster network; The sending nodes of drones in the drone cluster network separate the channel resource contention from the data packet sending and receiving process according to the unified clock, and time-division multiplex the channel time domain resources into the control channel time interval CCHI phase and the service channel time interval SCHI phase; In the CCHI stage, service channel resource negotiation is performed according to the preset MAC protocol frame structure, and time-frequency multiplexing is used to access the shared service channel to complete the initial hybrid multiple access; the SCHI stage is used to send data packets; During the service channel access process, the drone sending node follows the preset backoff process. Under the premise that the data packet to be sent does not mutate, if the drone sending node encounters a collision conflict of the data packet, the backoff window length of the drone sending node will be increased in the next round; if the transmission is successful, the backoff window length will be reduced.

2. The hybrid multiple access method according to claim 1, characterized in that: A dynamic sending buffer is designed for the drone sending node: when the drone sending node needs to send data packets, the data packets are sequentially placed in a finite-length sending buffer in the internal storage of the drone sending node; the data queue in the sending buffer adopts first-in-first-out, and when there are multiple data packets from the same drone receiving node, the data queue is dynamically adjusted to arrange these data packets together continuously; among them, when the data packets are arranged continuously, the position of the data packet first sent to the drone receiving node remains unchanged, and the remaining data packets are arranged in order with this data packet as the head of the queue.

3. The hybrid multiple access method according to claim 1, characterized in that: The preset MAC protocol frame structure includes RTS_CMC frame, CB frame and CB -1 frame; The RTS_CMC frame is based on the existing control information frame RTS, and adds a field for the number of packets to be sent to describe the queuing of packets in the sending buffer of the drone sending node. In addition, the information gain describes the task priority and waiting delay of the packets in the sending buffer of the drone sending node. CB frame and CB -1 The frame is used for the drone receiving node CCHI phase announcement; The CB frame structure includes control frame, duration, CCHI announcement time, drone receiving node ID, time slot index information and frame check sequence; CB -1 The structure of the frame is basically the same as that of the CB frame, except that -1 The frame does not contain a slot index information field.

4. The hybrid multiple access method according to claim 1, characterized in that: The CCHI stage performs service channel resource negotiation according to the preset MAC protocol frame structure, accesses the shared service channel using time-frequency multiplexing, and completes preliminary hybrid multiple access, including: At the beginning of each CCHI phase, the drone receiving node performs CB on the control channel. -1 The frame is broadcasted, and the drone receiving node ID and CCHI announcement time field carried in it are used to ensure that the corresponding drone sending node receives the CB frame; the drone sending node receives the CB -1 After the frame, the start time of the CCHI phase of the drone receiving node is known through the CCHI announcement time, and the duration of the CCHI phase is known through the duration field; the drone sending node sends an RTS_CMC frame to the drone receiving node to compete for the corresponding service channel communication resources; At the end of the CCHI phase, the drone receiving node broadcasts the CB frame on the control channel. The time slot index information in the CB frame is used to inform the drone sending node of the corresponding SCHI time slot allocation. The drone sending node that obtains the time slot allocation adjusts the transmitter and sends data packets based on the TDMA mechanism in the corresponding time slot; the drone sending node that does not obtain the time slot allocation adjusts its own waiting delay and turns off the transmitter until the receiver receives the next round of CB from the drone receiving node. -1 frame.

5. The hybrid multiple access method according to claim 4, characterized in that: The UAV sending node sends an RTS_CMC frame to the UAV receiving node through an improved CSMA / CA mechanism to compete for the corresponding service channel communication resources; wherein the improved CSMA / CA mechanism is: The improved CSMA / CA mechanism abandons the traditional four-step handshake and directly puts the information gain into the handshake request frame, namely the RTS_CMC frame, simplifying the channel access request process into a request-response two-step handshake; In the CCHI phase, all drone nodes maintain monitoring and conflict avoidance preparation states. Before sending the RTS_CMC frame, they monitor the control channel for a short interframe interval length. If the control channel is idle during the monitoring process, the request process is started. If there is a collision, the backoff process is started. If the sending node of the drone receives the ACK information sent by the receiving node of the drone, it is considered that the competition is successful and waits for the corresponding time slot of the CB frame broadcast notification at the end of the CCHI phase; The drone nodes that compete in the CCHI phase and successfully obtain the SCHI time slot will send data packets in the order of the time slots.

6. The hybrid multiple access method according to claim 1, characterized in that: The information gain in the CCHI phase of the drone sending node is defined as G I ,In a round of SCHI phase, for all UAV sending nodes competing for the service channel, time slots are allocated according to the corresponding information gain;,that the greater the information gain, the more time slots are allocated; The specific calculation method of information gain is as follows: G I =σP+θT wait +λF contin In the above formula, P represents the packet task priority, T wait Indicates the packet waiting time, F contin represents the number of packets to be sent by the node, σ, θ and λ represent P, T respectively. wait and F contin The corresponding weight factor.

7. The hybrid multiple access method according to claim 6, characterized in that: The data packet task priority is: setting two types of task priorities for data packets, high and low. The high priority represents the dynamic information collected by the drone and the data packets with QoS support specified by the upper-layer business, and the low priority represents the static data collected by the drone and the data packets without QoS support specified by the upper-layer business; the high priority is 1 and the low priority is 0; The data packet waiting time is as follows: when the data packet enters the sending buffer of the sending node of the drone, a waiting timer is started; if there are multiple data packets, the waiting timer points to the first data packet sent; if the data packet is sent successfully, the corresponding waiting timer is reset to zero; if the data packet has not been sent after the corresponding time slot of the i-th CCHI stage, the waiting timer is counted into the waiting round i as the data packet waiting time; The number of packets to be sent by the node is the number of packets in the sending buffer of the drone sending node.

8. The hybrid multiple access method according to claim 1, characterized in that: According to the preset backoff process, under the premise that the data packet to be sent does not suddenly change, if the drone sending node encounters a collision conflict of the data packet, the backoff window length of the drone sending node is increased in the next round; if the transmission is successful, the backoff window length is reduced, including: Assign an initial value to the drone node backoff window; if a collision occurs, the backoff window length of the drone node will be doubled in the next round; if the sending is successful and the current backoff window length is greater than or equal to twice the initial backoff window length, the backoff window length of the drone node in the next round will be halved; if it is less than twice the initial backoff window length, the backoff window length of the drone node in the next round will be reduced by 1.

9. A terminal device comprising a processor, a memory and a computer program stored in the memory; characterized in that: When the processor executes the computer program, the hybrid multiple access method according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium, wherein a computer program is stored in the medium; characterized in that: When the computer program is executed by a processor, the hybrid multiple access method according to any one of claims 1 to 8 is implemented.

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