Unmanned aerial vehicle communication relay planning method for underground scene

Abstract

The invention discloses an unmanned aerial vehicle communication relay planning method for an underground scene. An unmanned aerial vehicle group takes off from a ground station to a target position; when the unmanned aerial vehicle group arrives at the boundary of the communication coverage of the ground station, selecting the unmanned aerial vehicle in the communication link with large information throughput as a relay unmanned aerial vehicle; when the unmanned aerial vehicle group encounters the problem that the communication link is disconnected at the relay unmanned aerial vehicle (UAV) p, the relay unmanned aerial vehicle (UAV) q and the unmanned aerial vehicle group far away from the ground station fly back, if the UAVp and the UAVq re-establish the communication link, the original task continues to be executed, and if the communication link is still not re-established at the UAVp, the unmanned aerial vehicle group continues to fly back until the communication link is established between the UAVq and the relay unmanned aerial vehicle UAVp-1, and the UAVq hovers; and executing an original task, selecting an unmanned aerial vehicle in a communication link with large information throughput as a relay unmanned aerial vehicle, hovering all relay unmanned aerial vehicles to form a communication link, and executing the set task when other unmanned aerial vehicle groups arrive at a target position. According to the invention, the problem of communication interruption of the unmanned aerial vehicle caused by terrain influence in an underground scene is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicle communication, and in particular to a unmanned aerial vehicle communication relay planning method for underground scenarios. Background Art

[0002] With the rapid development of the Internet of Things, smart cities and big data technology, wireless communication technology has also developed rapidly. As an emerging communication technology, drone communication has the advantages of flexible deployment, low cost and wide coverage. The drone relay communication system is a long-distance wireless communication system with drones as relay nodes. Drone communication systems are generally divided into two types: direct communication and relay communication. Direct communication refers to the communication between drones and ground users directly, while relay communication uses drones as relay nodes to forward signals from source nodes to target nodes. Relay communication can effectively expand network coverage, significantly suppress the path loss of the wireless channel for message transmission, and improve communication quality.

[0003] In drone communication systems, power and relay drone location are critical to network performance. Transmit power affects transmission distance and energy consumption, while relay drone location determines signal transmission path and network connectivity. For drone swarms, it is very important to balance the load of parallel transmission on multiple links.

[0004] Drones use wireless communications, and the propagation of radio waves is easily affected by various media. When electromagnetic waves propagate in the air, energy loss occurs, reducing power, and multipath effects introduce inter-symbol interference into the transmitted signal.

[0005] The radio signal sent by the drone first propagates in free space. Due to the obstruction and shielding of the signal in the underground environment, the signal will be lost, which will bring additional signal loss to the airspace communication link. Therefore, the path loss of the propagation signal consists of free space propagation loss and additional loss. The incident wave is the main factor of additional loss. They diffract on the obstructions in the underground environment and are reflected or scattered by the obstructions.

[0006] In the UAV relay communication system, the UAV acts as an aerial relay platform, and the relay forwarding protocols mainly include amplify and forward (AF) and decode and forward (DF). Among them, the AF protocol means that the UAV amplifies the received signal before forwarding it to the user; the DF protocol means that the UAV first decodes the received signal, then re-encodes it and forwards it to the user.

[0007] UAV relay communication forms such as Figure 1In underground scenarios, due to the limitation of communication distance and the signal obstruction or even shielding of underground scenarios, the ground station cannot directly contact the drones flying deep underground, so some drones in the drone group need to be assigned to serve as relay drones to assume the responsibility of relaying communication signals.

[0008] There are two common communication relay methods: non-associative forwarding and associative forwarding. The basic methods of these two relay information forwarding are shown in Figure 2. Figure 2 (a) is a non-associative forwarding method. The ground station node sends the relay information to the relay drone node. The relay drone node does not need to perform complex signal demodulation and decoding processes for the relay information. It only needs to simply amplify the received signal and resend it to the target node; Figure 2 (b) is an associative forwarding method. The ground station node packages the information and sends it to the relay drone node. After receiving the information packet, the relay drone decodes the received signal, re-encodes it, and then forwards the information packet to the target drone. The non-associative forwarding method is mainly aimed at simple communication systems. Its main advantages are simplicity and real-time performance. It is suitable for processing communications with strong signal conditions; associative forwarding is aimed at scenarios with high requirements for signal quality and bit error rate.

[0009] In the actual implementation process, there are three methods, namely, a non-association forwarding method, an association forwarding method and a hybrid forwarding method, as shown in FIG3(a), FIG3(b) and FIG3(c).

[0010] Therefore, the trajectory optimization problem of the relay UAV can be expressed as: during the flight of the relay UAV, find an optimal flight path to ensure the reliability of the UAV relay communication link transmission. Summary of the invention

[0011] The purpose of the present invention is to provide a UAV communication relay planning method for underground scenarios, in view of the fact that in the existing technology, due to the limitation of communication distance and the signal obstruction or even shielding of underground scenes, the ground station cannot directly contact the UAV flying deep underground.

[0012] The technical solution adopted to achieve the purpose of the present invention is:

[0013] A method for planning UAV communication relays for underground scenarios includes the following steps:

[0014] Step 1: After receiving the mission command from the ground station, the drone swarm takes off from the ground station and heads to the target location;

[0015] Step 2: As the drone swarm reaches the boundary of the ground station's communication coverage, if there is only one drone between the ground station and the drone performing the mission, the drone directly serves as a relay drone; if there are multiple optional drones that can form a communication link between the ground station and the drone performing the mission, the drone in the communication link with a large information throughput is selected as the relay drone. If the drone swarm does not encounter a communication link disconnection, it will directly fly to the target location to perform the mission;

[0016] Step 3: After the drone group leaves the communication coverage boundary of the ground station, if the relay drone UAV in the drone group close to the ground station p With the relay UAV near the target location q If the communication link between the UAV p and the drone swarm consisting of relay drones near the ground station remain stationary, the UAV q The drone group far away from the ground station flies towards the ground station while ensuring the normal communication link, that is, flies back;

[0017] If the UAV is flying back p 、UAV q If the communication link is reestablished, the UAV is considered p The situation is normal. The communication link is disconnected due to communication interference or shielding. q Remains motionless when the communication link is reestablished, compared to UAV q The drone group closer to the target location continues to fly towards the target location and continue to perform the original mission;

[0018] If the UAV is flying back q Arrival UAV p When the UAV p 、UAV q If the communication link cannot be reestablished, the UAV is considered p Lost, UAV q And the drone group far away from the ground station continues to fly back. If the UAV q Compared with UAV p The relay UAV is closer to the ground station. p-1 Once a communication link is established, the UAV q Remains motionless once the communication link is established, compared to UAV q The drone group closer to the target location continues to fly towards the target location and continue to perform the original mission. In the process of flying towards the target location, the drone group closer to the target location will continue to fly towards the target location and perform the original mission. q Among the drone groups closer to the target location, a drone in a communication link with a large information throughput is selected as a relay drone;

[0019] Step 4: All relay drones hover from the ground station to the target location to form a communication link, and the rest of the drone group arrives at the target location to perform the given task.

[0020] In the above technical solution, the information throughput R of the communication link in step 2 is expressed as follows according to the Shannon formula:

[0021] R=Blog 2 (1+SINR)

[0022] Where R is the information throughput of the communication link, B is the channel bandwidth, and SINR is the signal-to-noise ratio of the communication link.

[0023] In the above technical solution, when the UAV k As UAV i and UAVs j When relaying between UAVs, the communication process is divided into two stages. The information throughput of the communication link includes UAV i and UAVs k The information throughput R of the communication link between ik and UAV k and UAVs j The information throughput R of the communication link between kj Two parts.

[0024] In the above technical solution, the UAV i and UAVs k The information throughput R of the communication link between ik It is expressed as follows:

[0025] R ik =Blog 2 (1+γ ik )

[0026] In the formula, R ik For UAV i and UAVs k The information throughput of the communication link between them, B is the channel bandwidth, γ ik For UAV i With UAV k The signal-to-noise ratio of the communication link.

[0027] In the above technical solution, the UAV k and UAVs j The information throughput R of the communication link between kj It is expressed as follows:

[0028] R kj =Blog 2 (1+γ kj )

[0029] In the formula, R kj For UAV k and UAVs j The information throughput of the communication link between them, B is the channel bandwidth, γ kj For UAV k and UAVs j The signal-to-noise ratio of the communication link.

[0030] In the above technical solution, UAV i With UAV k The signal-to-noise ratio of the communication link between ik The calculation formula is as follows:

[0031]

[0032] In the formula, γ ik For UAV i With UAV k The signal-to-noise ratio of the communication link between UAV k The number of all drones within communication range, For UAV i The transmission power, For UAV k The transmission power of the lth UAV node within the communication range, During each relay message transmission, other UAV nodes in the communication link send messages to the target node UAV. k The total amount of interference, τ is the path loss constant, h ik For UAV i With UAV k The channel gain between lk For UAV l With UAV k The channel gain between 0 is the power of the noise, ε lk Represents UAV k UAV within the communication range l Interference with UAV k coefficient, when UAV l To the target node UAV k When there is interference, ε lk is 1, when UAV l To the target node UAV k When there is no interference, ε lk is 0, λ l is the number of relay messages transmitted in the communication link.

[0033] In the above technical solution, UAV k With UAV j The signal-to-noise ratio of the communication link betweenkj The calculation formula is as follows:

[0034]

[0035] In the formula, γ kj For UAV k With UAV j The signal-to-noise ratio of the communication link between UAV j The number of all drones within communication range, For UAV k The transmission power, For UAV j The transmission power of the sth UAV node within the communication radius, During each relay message transmission, other UAV nodes in the communication link send messages to the target node UAV. j The total amount of interference, τ is the path loss constant, h kj For UAV k With UAV j The channel gain between sj For UAV s With UAV j The channel gain between 0 is the power of the noise, ε sj Represents UAV j UAV within the communication range s Interference with UAV j coefficient, when UAV s To the target node UAV j When there is interference, ε sj is 1, when UAV s To the target node UAV j When there is no interference, ε sj is 0, λ s is the number of relay messages transmitted in the communication link.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The UAV communication relay planning method of the present invention can ensure the reliability of UAV relay communication link transmission. UAVs within the mutual communication radius can communicate directly, and appropriate UAVs are selected to relay information for UAVs outside the communication range, thereby ensuring communication transmission between the UAV and the ground station. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The figure shows a schematic diagram of the UAV relay communication form in the prior art.

[0039] FIG. 2( a ) is a schematic diagram showing a common non-associative relay information forwarding method.

[0040] FIG2( b ) is a schematic diagram showing a common method for forwarding associated relay information.

[0041] FIG3( a ) is a schematic diagram showing a common non-associative relay information forwarding method.

[0042] FIG3( b ) is a schematic diagram showing a common method for forwarding associated relay information.

[0043] FIG3( c ) is a schematic diagram showing a common hybrid relay information forwarding method.

[0044] Figure 4 Shown is an example diagram of the communication range of the drone of the present invention.

[0045] Figure 5 Shown is a schematic diagram of a multi-relay UAV communication link of the present invention.

[0046] Figure 6 Shown is a schematic diagram of the UAV communication relay planning of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] Reference Figure 6 ,A UAV communication relay planning method for underground scenarios includes the following steps:

[0049] Step 1: After receiving the mission command from the ground station, the drone swarm takes off from the ground station and heads to the target location;

[0050] Step 2: As the drone swarm reaches the boundary of the ground station's communication coverage, if there is only one drone between the ground station and the drone performing the mission, the drone directly serves as a relay drone; if there are multiple optional drones that can form a communication link between the ground station and the drone performing the mission, the drone in the communication link with a large information throughput is selected as the relay drone. If the drone swarm does not encounter a communication link disconnection, it will directly fly to the target location to perform the mission;

[0051] Step 3: After the drone group leaves the communication coverage boundary of the ground station, if the relay drone UAV in the drone group close to the ground station p With the relay UAV near the target location q If the communication link between the UAV p and the drone swarm consisting of relay drones near the ground station remain stationary, the UAV qThe drone group far away from the ground station flies towards the ground station while ensuring the normal communication link, that is, flies back;

[0052] If the UAV is flying back p 、UAV q If the communication link is reestablished, the UAV is considered p The situation is normal. The communication link is disconnected due to communication interference or shielding. q Remains motionless when the communication link is reestablished, compared to UAV q The drone group closer to the target location continues to fly towards the target location and continue to perform the original mission;

[0053] If the UAV is flying back q Arrival UAV p When the UAV p 、UAV q If the communication link cannot be reestablished, the UAV is considered p Lost, UAV q And the drone group far away from the ground station continues to fly back. If the UAV q Compared with UAV p The relay UAV is closer to the ground station. p-1 Once a communication link is established, the UAV q Remains motionless once the communication link is established, compared to UAV q The drone group closer to the target location continues to fly towards the target location and continue to perform the original mission. In the process of flying towards the target location, the drone group closer to the target location will continue to fly towards the target location and perform the original mission. q Among the drone groups closer to the target location, a drone in a communication link with a large information throughput is selected as a relay drone;

[0054] Step 4: All relay drones hover from the ground station to the target location to form a communication link, and the rest of the drone group arrives at the target location to perform the given task.

[0055] Reference Figure 4 , assuming that the UAV is out of communication range i and UAVs j Communication is required for information transfer, UAV i and UAVs j The communication coverage area of ​​UAV is defined as area1. i The communication coverage of UAV is defined as area2. j The communication coverage area is defined as area3, UAV i and UAVs jA communication link must be established between them for information transmission. If there is a UAV in area 1 k , then the UAV k Acting as a relay UAV, get the communication link UAV i –UAV k –UAV j .

[0056] If there are multiple drones in area1, a drone in a communication link with a large information throughput is selected as a relay drone; if there is no drone in area1, a drone in a communication link with a large information throughput is selected as a relay drone in the area of ​​the communication link receiver and moved to area1 as a relay drone.

[0057] If the drone swarm encounters the problem of communication link being disconnected at the relay drone, then compared with the relay drone, the drone swarm close to the ground station remains motionless, and the drone swarm far away from the ground station flies towards the ground station while ensuring the normal communication link, that is, flies back.

[0058] Reference Figure 5 Starting from the side close to the ground station, the communication link is distributed with relay UAVs in sequence. i 、UAV 1 、UAV 2 and UAVs j , UAV in UAV communication link 2 With UAV 1 If the communication connection is disconnected, the UAV 2 In-Security with UAV j Same as UAV when the connection is normal j Together, they fly in the opposite direction along the path they came from. If the UAV 2 Can be reconnected with UAV 1 To form a communication link, the UAV j etc. UAV swarms behind (compared to UAV j The drone group near the target location continues to perform the original flight mission. 2 Hover where the communication link is established; if the UAV 2 In-Security with UAV j If the connection is normal, fly to the UAV in the opposite direction along the path you came from. 1 The location of the UAV 1 If a communication link is formed, the UAV is considered 1 lost, in which case the drone swarm, far from the ground, flies back until the UAV 2 With the relay UAV parked ahead i Establishing a communication link, UAV2 Hovering where the communication link is established, the UAV j Wait for the drone group in the rear to continue the original flight mission.

[0059] The information throughput R of the drone in step 2 is expressed according to the Shannon formula:

[0060] R=Blog 2 (1+SINR)

[0061] Where R is the information throughput of the UAV, B is the channel bandwidth, and SINR is the signal-to-noise ratio of the communication link.

[0062] The UAV i With UAV j The signal-to-noise ratio SINR of the communication link between ij , γ ij The calculation of is as follows:

[0063]

[0064] In the formula, γ ij For UAV i With UAV j The signal-to-noise ratio of the communication link between UAV j The number of all drones within the communication range, For UAV i The transmission power, For UAV j The transmission power of the kth UAV node within the communication radius, During each relay message transmission, other UAV nodes in the communication link send messages to the target node UAV. j The total amount of interference, τ is the path loss constant, h ij For UAV i With UAV j The channel gain between kj For UAV i With UAV j The channel gain between 0 is the power of the noise, ε kj Represents UAV j UAV within the communication range k Interference with UAV j coefficient, when UAV k To the target node UAV j When there is interference, ε kj is 1, when UAV k To the target node UAV j When there is no interference, ε kj is 0, λ kis the number of relay messages transmitted in the communication link.

[0065] When the UAV k As UAV i and UAVs j When relaying between UAVs, the communication process is divided into two stages. The information throughput of the communication link includes i and UAVs k The information throughput R of the communication link between ik and UAV k and UAVs j The information throughput R of the communication link between kj Two parts.

[0066] Wherein, the UAV i and UAVs k The information throughput R of the communication link between ik It is expressed as follows:

[0067] R ik =Blog 2 (1+γ ik )

[0068] In the formula, R ik For UAV i and UAVs k The information throughput of the communication link between them, B is the channel bandwidth, γ ik For UAV i With UAV k The signal-to-noise ratio of the communication link.

[0069] The UAV k and UAVs j The information throughput R of the communication link between kj It is expressed as follows:

[0070] R kj =Blog 2 (1+γ kj )

[0071] In the formula, R kj For UAV k and UAVs j The information throughput of the communication link between them, B is the channel bandwidth, γ kj For UAV k and UAVs j The signal-to-noise ratio of the communication link.

[0072] UAV i With UAV k The signal-to-noise ratio of the communication link between ik The calculation formula is as follows:

[0073]

[0074] In the formula, γ ik For UAV i With UAV k The signal-to-noise ratio of the communication link between UAV k The number of all drones within communication range, For UAV i The transmission power, For UAV k The transmission power of the lth UAV node within the communication range, During each relay message transmission, other UAV nodes in the communication link send messages to the target node UAV. k The total amount of interference, τ is the path loss constant, h ik For UAV i With UAV k The channel gain between lk For UAV l With UAV k The channel gain between 0 is the power of the noise, ε lk Represents UAV k UAV within the communication range l Interference with UAV k coefficient, when UAV l To the target node UAV k When there is interference, ε lk is 1, when UAV l To the target node UAV k When there is no interference, ε lk is 0, λ l is the number of relay messages transmitted in the communication link.

[0075] UAV k With UAV j The signal-to-noise ratio of the communication link between kj The calculation formula is as follows:

[0076]

[0077] In the formula, γ kj For UAV k With UAV j The signal-to-noise ratio of the communication link between UAV j The number of all drones within communication range, For UAV k The transmission power, For UAV jThe transmission power of the sth UAV node within the communication radius, During each relay message transmission, other UAV nodes in the communication link send messages to the target node UAV. j The total amount of interference, τ is the path loss constant, h kj For UAV k With UAV j The channel gain between sj For UAV s With UAV j The channel gain between 0 is the power of the noise, ε sj UAV in display j UAV within the communication range s Interference with UAV j coefficient, when UAV s To the target node UAV j When there is interference, ε sj is 1, when UAV s To the target node UAV j When there is no interference, ε sj is 0, λ s is the number of relay messages transmitted in the communication link.

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A UAV communication relay planning method for underground scenarios, characterized in that: The following steps are involved: Step 1: After receiving the mission command from the ground station, the drone swarm takes off from the ground station and heads to the target location; Step 2: As the drone group reaches the boundary of the ground station's communication coverage, if there is only one drone between the ground station and the drone performing the mission, the drone directly serves as a relay drone. If there are multiple optional drones that can form a communication link between the ground station and the drone performing the mission, the drone in the communication link with large information throughput is selected as the relay drone. If the drone group does not encounter a communication link disconnection, it will directly fly to the target location to perform the mission; Step 3: After the drone group leaves the communication coverage boundary of the ground station, if the relay drone UAV in the drone group close to the ground station p With the relay UAV near the target location q If the communication link between the UAV p and the drone swarm consisting of relay drones near the ground station remain stationary, the UAV q The drone group far away from the ground station flies towards the ground station while ensuring the normal communication link, that is, flies back; If the UAV is flying back p 、UAV q If the communication link is reestablished, the UAV is considered p The situation is normal. The communication link is disconnected due to communication interference or shielding. q Remains motionless when the communication link is reestablished, compared to UAV q The drone group closer to the target location continues to fly towards the target location and continue to perform the original mission; If the UAV is flying back q Arrival UAV p When the UAV p 、UAV q If the communication link cannot be reestablished, the UAV is considered p Lost, UAV q And the drone group far away from the ground station continues to fly back. If the UAV q Compared with UAV p The relay UAV is closer to the ground station. p-1 Once a communication link is established, the UAV q Remains motionless once the communication link is established, compared to UAV q The drone group closer to the target location continues to fly towards the target location and continue to perform the original mission. In the process of flying towards the target location, the drone group closer to the target location will continue to fly towards the target location and perform the original mission. q Among the drone groups closer to the target location, a drone in a communication link with a large information throughput is selected as a relay drone; Step 4: All relay drones hover from the ground station to the target location to form a communication link, and the rest of the drone group arrives at the target location to perform the given task.

2. The method for planning underground drone communication relays according to claim 1, characterized in that: The information throughput R of the communication link in step 2 is expressed according to Shannon's formula as follows: R = Blog2(1+SINR) Where R is the information throughput of the communication link, B is the channel bandwidth, and SINR is the signal-to-noise ratio of the communication link.

3. The method for planning underground drone communication relays according to claim 2, characterized in that: When UAV k As UAV i and UAVs j When relaying between UAVs, the communication process is divided into two stages. The information throughput of the communication link includes UAV i and UAVs k The information throughput R of the communication link between ik and UAV k and UAVs j The information throughput R of the communication link between kj Two parts.

4. The method for planning underground drone communication relays according to claim 3, characterized in that: The UAV i and UAVs k The information throughput R of the communication link between ik It is expressed as follows: R ik =Blog2(1+γ ik ) In the formula, R ik For UAV i and UAVs k The information throughput of the communication link between them, B is the channel bandwidth, γ ik For UAV i With UAV k The signal-to-noise ratio of the communication link.

5. The method for planning underground drone communication relays according to claim 3, characterized in that: The UAV k and UAVs j The information throughput R of the communication link between kj It is expressed as follows: R kj =Blog2(1+γ kj ) In the formula, R kj For UAV k and UAVs j The information throughput of the communication link between them, B is the channel bandwidth, γ kj For UAV k and UAVs j The signal-to-noise ratio of the communication link.

6. The underground scene-oriented UAV communication relay planning method according to claim 4, characterized in that: UAV i With UAV k The signal-to-noise ratio of the communication link between ik The calculation formula is as follows: In the formula, γ ik For UAV i With UAV k The signal-to-noise ratio of the communication link between UAV k The number of all drones within communication range, For UAV i The transmission power, For UAV k The transmission power of the lth UAV node within the communication range, During each relay message transmission, other UAV nodes in the communication link send messages to the target node UAV. k The total amount of interference, τ is the path loss constant, h ik For UAV i With UAV k The channel gain between lk For UAV l With UAV k The channel gain between them, N0 is the power of the noise, ε lk Represents UAV k UAV within the communication range l Interference with UAV k coefficient, when UAV l To the target node UAV k When there is interference, ε lk is 1, when UAV l To the target node UAV k When there is no interference, ε lk is 0, λ l is the number of relay messages transmitted in the communication link.

7. The underground scene-oriented UAV communication relay planning method according to claim 5, characterized in that: UAV k With UAV j The signal-to-noise ratio of the communication link between kj The calculation formula is as follows: In the formula, γ kj For UAV k With UAV j The signal-to-noise ratio of the communication link between UAV j The number of all drones within communication range, For UAV k The transmission power, For UAV j The transmission power of the sth UAV node within the communication radius, During each relay message transmission, other UAV nodes in the communication link send messages to the target node UAV. j The total amount of interference, τ is the path loss constant, h kj For UAV k With UAV j The channel gain between sj For UAV s With UAV j The channel gain between them, N0 is the power of the noise, ε sj Represents UAV j UAV within the communication range s Interference with UAV j coefficient, when UAV s To the target node UAV j When there is interference, ε sj is 1, when UAV s To the target node UAV j When there is no interference, ε sj is 0, λ s is the number of relay messages transmitted in the communication link.

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