A UAV ground-to-air networking collaborative data link communication method

Abstract

The present invention relates to a data link communication method for coordinated ground-to-air networking of unmanned aerial vehicles, and belongs to the technical field of data links of unmanned aerial vehicles. The present invention comprises: dividing time slots into two categories, namely, uplink and downlink; aerial nodes send air-to-ground broadcasts in downlink time slots; ground nodes receive broadcast information to achieve coarse alignment with the time of aerial nodes; each ground node sends a network access application frame to the aerial node in the corresponding uplink time slot; the aerial node calculates the one-way distance delay between the aerial node and the ground node; the aerial node broadcasts the one-way distance delay and the network access application ACK to each ground node; the ground node finely adjusts the local clock, and sends service data to the aerial node after offsetting the corresponding one-way distance delay in the corresponding uplink time slot. The present invention can greatly improve the duty cycle of receiving and transmitting during the coordinated ground-to-air networking of unmanned aerial vehicles, and effectively support large-scale networking and long-distance high-efficiency transmission.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicle data links, and in particular to a method for coordinated data link communication of unmanned aerial vehicle ground-to-air networking. Background Art

[0002] In the ground-to-air collaborative networking of UAV systems, the air nodes and ground nodes in the network are distributed over a wide area, and the topological structure and the relative distance between nodes vary with time. The time division multiple access (TDMA) system is mainly used to ensure conflict-free transmission between nodes in the network. Time division multiple access technology allocates available time slots for active users by a central node, or determines the available time slots of each node through distributed collaboration between nodes, and each user transmits information in its allocated time slot in a cyclic manner. All active users transmit information in different time slots of the same frequency. When an active user finishes transmitting information, it notifies the central node or neighboring node that it no longer needs to occupy the time slot, and the time slot will be reallocated to other active users.

[0003] In the time-division group network, considering that the ground-air coordination nodes are widely distributed, and both the air nodes and the ground nodes are in a mobile state, the distance between nodes is far and the distance varies with time. In this scenario, in order to ensure that multiple nodes do not collide or overlap when sending data to a single node in time-sharing, a protection interval is usually added after each node time slot to shield the transmission delay difference caused by the different distances between multiple nodes. When the scale of nodes in the collaborative data link gradually increases, the number of protection intervals increases synchronously, which ultimately leads to a larger protection interval overhead with more nodes, severe network capacity limitation, and lower network transmission efficiency. Summary of the invention

[0004] In view of this, the present invention proposes a UAV ground-to-air networking collaborative data link communication method. The transmission frame structure of this method is compact and the protection time slot overhead is very low, which solves the problem that the more nodes there are in traditional TDMA networking, the greater the overhead. It can support large-scale networking, long-distance efficient transmission and other application requirements, and has strong engineering practicality.

[0005] The technical solution adopted by the present invention is:

[0006] A method for cooperative data link communication of ground-to-air networking of unmanned aerial vehicles comprises the following steps:

[0007] Step 1: divide the time slots into uplink and downlink time slots. 0 Occupied by aerial nodes, the number is 1; uplink time slot S 1 , S 2 ,……,S n Occupied by ground nodes, the number of time slots is the same as the number of ground nodes, which is n; a transmission protection interval S is set between the downlink time slot and the uplink time slot gapThe uplink working mode is time-sharing point-to-point transmission from multiple ground nodes to the air. The uplink time slot of the ground node is a multi-functional time slot, which can send information on network access application, service transmission, and network exit application to the air node in time-sharing;

[0008] Step 2: The aerial node is in the downlink time slot S 0 Send air-to-ground broadcasts, including broadcast service data, network operation status information, uplink time slot occupancy and allocation information, network entry application ACK, and network exit application ACK;

[0009] Step 3: The ground node receives the information broadcast and distributed by the aerial node in the downlink time slot, obtains the uplink time slot occupancy and allocation information, and adjusts the local time based on the start of the aerial node broadcast time slot frame to achieve coarse alignment with the aerial node time.

[0010] Step 4: Each ground node sends a network access application frame to the air node in the corresponding uplink time slot. The network access application frame adopts a short frame format.

[0011] Step 5: After the aerial node receives the network access application frame from the nth ground node, it calculates the one-way distance delay between the aerial node and the ground node as Δt n =( t n1 +t n2 ) / 2; where t n1 is the downlink propagation delay between the aerial node and the nth ground node, t n2 is the uplink propagation delay between the nth ground node and the aerial node; then it turns to the service transmission process;

[0012] Step 6: The aerial node sends the calculated one-way distance delay and network access request ACK through the downlink time slot S 0 , broadcast to each ground node;

[0013] Step 7: The ground node finely adjusts the local clock according to the one-way distance delay between itself and the aerial node, and sends service data to the aerial node after offsetting the corresponding one-way distance delay in the corresponding uplink time slot.

[0014] Furthermore, it also includes:

[0015] Step 8: The ground node sends a network exit request in the form of a short frame. After receiving the network exit request, the aerial node sends the network exit request in the next time frame cycle through the downlink time slot S 0 Send the network withdrawal request ACK information to the ground node and reclaim the time slot resources of the network withdrawal node.

[0016] Furthermore, no guard interval is set between multiple uplink time slots, or a very small guard interval is set.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention is applicable to scenarios where the distance between aerial nodes and ground nodes can change freely. Compared with the traditional method that can only support usage scenarios not exceeding a fixed distance (such as 100 km), the scope of application and flexibility are significantly improved.

[0019] (2) The uplink time slot of the ground node of the present invention is a multifunctional time slot, which can send network access application, service transmission, network exit application and other information to the air node in a time-sharing manner. Compared with the traditional method in which network access application and network exit application occupy independent time slots, the transmission efficiency is maximized after all nodes are connected to the network.

[0020] (3) The transmission frame structure configuration of the present invention adopts a tight time slot arrangement rule without a protection interval (or a small protection interval). Compared with the time slot arrangement rule of the traditional method in which one protection interval is added to each time slot, the duty cycle of the transmission time slot is greatly improved, which directly leads to an increase in the network capacity and transmission efficiency of the networking data link. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a diagram of the transmission frame structure configuration in an embodiment of the present invention.

[0022] Figure 2 Schematic diagram of a downlink time slot in an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram of an uplink network access application in an embodiment of the present invention.

[0024] Figure 4 The figure is a schematic diagram of uplink service transmission in an embodiment of the present invention.

[0025] Figure 5 This is an uplink schematic diagram of a network exit application in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0027] A method for cooperative data link communication of ground-to-air networking of unmanned aerial vehicles, characterized in that it comprises the following steps:

[0028] Step 1: divide the time slots into uplink and downlink time slots. 0 Occupied by aerial nodes, the number is 1; uplink time slot S 1 , S 2 ,……,S n Occupied by ground nodes, the number of time slots is the same as the number of ground nodes, which is n; a transmission protection interval S is set between the downlink time slot and the uplink time slot gap , no protection interval is set between multiple uplink time slots, or it is set much smaller than S gapCompared with the traditional method of adding a protection interval after each node's transmission time slot, the network overhead is greatly reduced; the uplink working mode is time-sharing point-to-point transmission from multiple ground nodes to the air, and the uplink time slot of the ground node is a multi-functional time slot, which can send information on network access application, service transmission, and network exit application to the air node in time-sharing;

[0029] Step 2: The aerial node is in the downlink time slot S 0 Send air-to-ground broadcasts, including broadcast service data, network operation status information, uplink time slot occupancy and allocation information, network entry application ACK, and network exit application ACK;

[0030] Step 3: The ground node receives the information broadcast and distributed by the aerial node in the downlink time slot, obtains the uplink time slot occupancy and allocation information, and adjusts the local time based on the start of the aerial node broadcast time slot frame to achieve coarse alignment with the aerial node time.

[0031] Step 4: Each ground node sends a network access application frame to the air node in the corresponding uplink time slot. The network access application frame adopts a short frame format (the network access application frame occupies a relatively low space in the uplink time slot);

[0032] Step 5: After the aerial node receives the network access application frame from the nth ground node, it calculates the one-way distance delay between the aerial node and the ground node as Δt n =( t n1 +t n2 ) / 2; where t n1 is the downlink propagation delay between the aerial node and the nth ground node, t n2 is the uplink propagation delay between the nth ground node and the aerial node; then it turns to the service transmission process;

[0033] Step 6: The aerial node sends the calculated one-way distance delay and network access request ACK through the downlink time slot S 0 , broadcast to each ground node;

[0034] Step 7: The ground node finely adjusts the local clock according to the one-way distance delay between itself and the aerial node, and sends service data to the aerial node after offsetting the corresponding one-way distance delay in the corresponding uplink time slot;

[0035] Step 8: The ground node sends a network exit request in the form of a short frame (the network exit request frame occupies a relatively low space in the uplink time slot). After receiving the network exit request, the aerial node sends the network exit request in the next time frame cycle through the downlink time slot S 0 Send the network withdrawal request ACK information to the ground node and reclaim the time slot resources of the network withdrawal node.

[0036] Here is a more specific example:

[0037] See also Figure 1 In the transmission frame structure configuration, the data link transmission frame structure adopts a tight time slot arrangement rule with no protection interval (or small protection interval). The time slot type is divided into two categories: uplink and downlink. 0 Occupied by aerial nodes, the number is 1; uplink time slot S 1 , S 2 ,……,S n Occupied by ground nodes, the number of time slots is the same as the number of ground nodes, which is n. There is a transmission protection interval S between the downlink time slot and the uplink time slot gap , multiple uplink time slots are connected at the end, without a protection interval (or much smaller than S gap The transmission duty cycle and transmission efficiency are high. 0 The working mode is air-to-ground broadcast. The broadcast content includes broadcast service data, network operation status information, uplink time slot occupancy and allocation information, network access application ACK, network exit application ACK, etc. The uplink working mode is time-sharing point-to-air transmission by multiple ground nodes. The uplink time slot of the ground node is a multi-functional time slot, which can send network access application, service transmission, network exit application and other information to the air node in a time-sharing manner.

[0038] See also Figure 2 and Figure 3 , consider the case of two ground nodes, ground node 1, ground node 2 and the aerial node at different relative distances. In the process of network access application, ground node 1 and ground node 2 first receive the information broadcast and distributed by the aerial node in the downlink time slot, obtain the uplink time slot occupancy and allocation information, and use the start of the aerial node broadcast time slot frame as a reference to adjust the local time and roughly align with the aerial node time. Ground node 1 and ground node 2 are respectively configured according to the above-mentioned transmission frame structure, and send network access application frames to the aerial node in the corresponding time slot. The network access application frame adopts the short frame form (the network access application frame occupies a relatively low space in the uplink time slot). The timing when the aerial node receives the network access application frame from ground node 1 is related to the downlink propagation delay t 11 and the upstream propagation delay t 12 The air node receives the network access application frame compared to the uplink time slot S 1 The starting position is delayed by t 11 +t 12 , from which we can get the one-way distance delay between the aerial node and the ground node 1 is Δt 1 =( t 11 +t 12 ) / 2; Similarly, the one-way distance delay between the aerial node and the ground node 2 is Δt 2 =( t 21 +t 22 ) / 2. Then it enters the business transmission process.

[0039] See also Figure 2 and Figure 4 During the service transmission process, the aerial node will calculate the Δt 1 , Δt 2 Value, network application ACK through the downlink time slot S 0 , broadcast to ground node 1 and ground node 2. Ground node 1 and ground node 2 are based on Δt 1 , Δt 2 The local clock is fine-tuned and the uplink timeslot S 1 , Uplink time slot S 2 Bias Δt 1 , Δt 2 Send business data to the air node.

[0040] See also Figure 2 and Figure 5 The network withdrawal application process is similar to the network access application process, using a short frame format (the network withdrawal application frame occupies a relatively low space in the uplink time slot). After the aerial node receives the network withdrawal application from the ground node, it sends the network withdrawal application to the ground node in the next round of time frame cycle through the downlink time slot S 0 Send the network withdrawal request ACK information to the ground node and reclaim the time slot resources of the network withdrawal node.

[0041] In summary, the present invention achieves significant improvement in the duty cycle of receiving and transmitting during ground-to-ground collaborative networking of UAVs by enabling collaboration between aerial nodes and ground nodes, and adopting a tight time slot arrangement rule with no protection interval (or small protection interval) in the data link transmission frame structure, combined with the optimized design of network access application, service transmission, network exit application, and resource release processes, which can effectively support large-scale networking and long-distance high-efficiency transmission.

Claims

1. A UAV ground-to-air networking collaborative data link communication method, characterized in that: The following steps are involved: Step 1: divide the time slots into uplink and downlink. The downlink time slot S0 is occupied by the aerial node, and the number is 1; the uplink time slots S1, S2, ..., S n Occupied by ground nodes, the number of time slots is the same as the number of ground nodes, which is n; a transmission protection interval S is set between the downlink time slot and the uplink time slot gap The uplink working mode is time-sharing point-to-point transmission from multiple ground nodes to the air. The uplink time slot of the ground node is a multi-functional time slot, which can send information on network access application, service transmission, and network exit application to the air node in time-sharing; Step 2: The aerial node sends an air-to-ground broadcast in the downlink time slot S0. The broadcast content includes broadcast service data, network operation status information, uplink time slot occupancy and allocation information, network entry application ACK, and network exit application ACK. Step 3: The ground node receives the information broadcast and distributed by the aerial node in the downlink time slot, obtains the uplink time slot occupancy and allocation information, and adjusts the local time based on the start of the aerial node broadcast time slot frame to achieve coarse alignment with the aerial node time. Step 4: Each ground node sends a network access application frame to the air node in the corresponding uplink time slot. The network access application frame adopts a short frame format. Step 5: After the aerial node receives the network access application frame from the nth ground node, it calculates the one-way distance delay between the aerial node and the ground node as Δt n =( t n1 +t n2 ) / 2; where t n1 is the downlink propagation delay between the aerial node and the nth ground node, t n2 is the uplink propagation delay between the nth ground node and the aerial node; Then it turns to the business transmission process; Step 6: The aerial node broadcasts the calculated one-way distance delay and network access application ACK to each ground node through the downlink time slot S0; Step 7: The ground node finely adjusts the local clock according to the one-way distance delay between itself and the aerial node, and sends service data to the aerial node after offsetting the corresponding one-way distance delay in the corresponding uplink time slot.

2. The method for cooperative data link communication of ground-to-air networking of unmanned aerial vehicles according to claim 1 is characterized in that: Also includes: Step 8: The ground node sends a network withdrawal application in the form of a short frame. After receiving the network withdrawal application, the aerial node sends a network withdrawal application ACK information to the ground node through the downlink time slot S0 in the next time frame cycle, and reclaims the network withdrawal node time slot resources.

3. The method for cooperative data link communication of ground-to-air networking of unmanned aerial vehicles according to claim 1 is characterized in that: No guard interval is set between multiple uplink time slots.

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