A neighbor discovery method with adjustable beam width suitable for unmanned aerial vehicle ad hoc network

Abstract

This invention discloses a neighbor discovery method with adjustable beamwidth suitable for UAV ad hoc networks. The method first adjusts the scanning beamwidth to a wider beam and uses a random scanning algorithm to coarsely scan the neighbor information of a node. Then, based on the wide-beam scanning results, a probability distribution for narrow-beam scanning is generated. Finally, the beamwidth is adjusted to the beamwidth used for data transmission (narrow beam), and the neighbor discovery scanning process is performed according to the probability distribution. The probability distribution is adjusted based on the discovery process until the neighbor discovery process is complete. This method utilizes wide-beam scanning to quickly obtain coarse neighbor information, guiding the subsequent narrow-beam scanning process, greatly reducing the complexity of narrow-beam scanning and shortening the time required for the neighbor discovery process. Furthermore, the method protected by this application has good practicality and versatility.

Description

Technical Field

[0001] This invention belongs to the field of UAV wireless network communication technology, and particularly relates to a neighbor discovery method with adjustable beamwidth suitable for UAV self-organizing networks. Background Technology

[0002] Directional antennas have been widely used in UAV ad hoc networks due to their advantages such as increased spatial reuse, longer transmission distance, strong anti-interference capability, and strong concealment. Neighbor discovery is a crucial step in UAV ad hoc networks. User data transmission can only occur after nodes have discovered each other. Because directional antennas have narrow beams, beam alignment is required for mutual discovery. Therefore, it is necessary to design suitable neighbor discovery algorithms to minimize the time required for neighbor discovery in UAV ad hoc networks.

[0003] Existing neighbor discovery algorithms are mainly divided into two categories: The first category is deterministic scanning sequence neighbor discovery algorithms, where nodes scan according to a pre-designed sequence. This method can guarantee that all nodes complete network entry within a finite time, but this time is often very long, and generally requires prior network structure information to design the sequence. This method is not suitable for highly mobile UAV networks. The other category is random scanning neighbor discovery algorithms, which generally select the transmit / receive state and the scan sector sequence randomly according to a certain probability. This probability can be a fixed probability or it can be adaptively adjusted using algorithms such as automatic learning machines or Q-Learning based on collision or historical scan results. This method is suitable for purely distributed systems with little network information and is highly robust. However, as the number of node sectors increases, the time consumption increases exponentially. For highly mobile UAV networks, directional antennas need to consider three-dimensional direction and should use the narrowest beam possible to improve data transmission stability. In this scenario, a high neighbor discovery delay will not meet the mobility requirements of UAV networks (i.e., by the time neighbor discovery is completed, the network topology may have changed significantly, and the neighbor relationships between nodes may have also changed). Summary of the Invention

[0004] In view of this, the present invention proposes a neighbor discovery method with adjustable beamwidth suitable for UAV ad hoc networks. This method uses wide beams to quickly scan and obtain coarse neighbor information to guide the subsequent narrow beam scanning process, which greatly reduces the complexity of narrow beam scanning and shortens the time required for the neighbor discovery process.

[0005] To achieve this objective, the present invention proposes the following technical solution: a neighbor discovery method with adjustable beamwidth suitable for UAV ad hoc networks, the method comprising:

[0006] S401: Based on the beamwidth (BW) required for data link transmission N Calculate the broadband scanning beamwidth BWW (BW W >>BW N );

[0007] S402: Beamwidth BW W The UAV is divided into sectors and numbered, neighbor discovery is performed, and the beamwidth (BW) is obtained. W The following is a table of neighbor relationships, N;

[0008] S403: Adjust beamwidth to BW N With beamwidth BW N The UAV is divided into sectors and numbered, and the beamwidth BW is generated based on the neighbor relationship table N. N The probability distribution P of the number of neighbors in each sector;

[0009] S404: Determine the beamwidth BW based on the probability distribution P. N The node's transmit / receive mode and scanning direction;

[0010] S405: Send or listen for handshake packets according to the determined node transmission and reception mode and scanning direction, and use a two-step handshake for interaction;

[0011] S406: When a new neighbor is discovered, adjust the probability distribution P according to the discovered neighbor relationships and write the neighbor relationship into the neighbor relationship table;

[0012] S407: Determine whether all neighboring nodes have been discovered. If there are still undiscovered neighbors, proceed to step 404; if all neighbors have been discovered, proceed to step S408.

[0013] S408: End the neighbor discovery process.

[0014] Preferably, the broadband scanning beamwidth BW W The calculation method is as follows:

[0015] BW W =2π / K1

[0016] in, K2 = 2π / BW N K1 is the beamwidth BW W The number of sectors, K2 refers to the beamwidth BW. N The number of sectors to be divided, where α is a positive integer, if there exist multiple satisfying... If α is less than 10, then K1 takes the value closest to 10, and N... + Represents a positive integer.

[0017] Preferably, the process of generating the probability distribution P of the number of neighbors in each sector is as follows:

[0018] Let node i have a beamwidth BWW The neighbor relationships obtained from the scan are as follows:

[0019]

[0020] Where N i Here is the neighbor table for node i, and 0, ..., k1, ..., K1-1 is the beamwidth BW. W The sector numbers below, These refer to the number of neighbors of sector 0, ..., k1, ..., K1-1 of node i, respectively;

[0021] i-node at beamwidth BW W The probability distribution of the number of neighbors in each sector is as follows:

[0022]

[0023] in, It rounds down, where j represents the beamwidth BW. W The j-th sector, j∈[0,K1-1], This represents the number of neighbors of node i in sector j. Indicates that node i is at the 1st rank. The number of neighbors in each sector; For beamwidth BW N The selection probability of the k2th sector.

[0024] Preferably, in S406, when the beamwidth BW N After a new neighbor is discovered during the scan, the probability distribution P of the number of neighbors is updated as follows: Suppose a new neighbor is discovered in the k1-th sector, then the probability distribution after discovering a new neighbor is updated as follows:

[0025]

[0026] Preferably, in step S405, the neighbor discovery two-step handshake process is as follows:

[0027] A node in sending mode sends a handshake packet with its own node ID in the first sub-time slot and listens in the second time slot;

[0028] The node in the receiving mode listens in the first sub-time slot. If it correctly receives the handshake packet from another node in the first time slot, it replies with an acknowledgment handshake packet in the second time slot. If a conflicting handshake packet is detected in the second time slot, it does not take any action in the second time slot.

[0029] The beneficial effects of this invention are as follows: The neighbor discovery method with adjustable beamwidth suitable for UAV ad hoc networks disclosed in this invention proposes a two-round scanning mechanism for the first time. It obtains coarse neighbor information through fast wide-beam scanning, effectively reducing the time consumption caused by the increase in the number of sectors. Furthermore, the information obtained by the wide-beam scanning can provide an effective termination criterion and probability distribution adjustment basis for narrow-beam scanning, avoiding the time consumption required to determine whether the neighbor discovery process can end, and also avoiding the omission of neighbor relationships, thus making it more practical. The method proposed in this application is not limited to specific scanning methods and can be well applied to various scenarios, exhibiting good versatility. The wide-beam selection method and probability distribution acquisition and update method designed in the method proposed in this invention can effectively reduce the complexity of narrow-beam scanning and accelerate the neighbor discovery process. Attached Figure Description

[0030] Figure 1 This is a flowchart of a beamwidth-adjustable neighbor discovery method applicable to UAV ad hoc networks in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram illustrating the sector division using wide and narrow beams in the embodiment;

[0032] Figure 3 This is a performance comparison chart between the method proposed in this invention and the neighbor discovery method based on random scanning. Detailed Implementation

[0033] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

[0034] This invention proposes an efficient neighbor discovery method for directional antennas with adjustable beamwidth, suitable for UAV ad hoc networks. First, the beam is adjusted to a wider beamwidth, and a random scanning algorithm is used to coarsely scan the neighbor information of a node. Then, a probability distribution for narrow-beam scanning is generated based on the wide-beam scanning results. Finally, the beamwidth is adjusted to the beamwidth used for data transmission (narrow beamwidth), and the neighbor discovery scanning process is performed according to the probability distribution. The probability distribution is adjusted based on the discovery process until the neighbor discovery process is complete. This method significantly reduces the complexity of narrow-beam scanning and shortens the time required for neighbor discovery by using wide-beam scanning to quickly obtain coarse neighbor information and guide the subsequent narrow-beam scanning process. Furthermore, this method can also be incorporated into the random scanning algorithm to utilize algorithms such as automatic learning machines and Q-Learning to adaptively adjust the scanning probability, further optimizing the neighbor discovery time consumption.

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0036] A beamwidth-adjustable neighbor discovery method suitable for UAV ad hoc networks, the process of which is as follows: Figure 1 As shown, it includes:

[0037] S401: Based on the beamwidth (BW) required for data link transmission N Calculate the broadband scanning beamwidth BW W (BW W >>BW N );

[0038] S402: Beamwidth BW W The UAV is divided into sectors and numbered, neighbor discovery is performed, and the beamwidth (BW) is obtained. W The following is a table of neighbor relationships, N;

[0039] S403: Adjust beamwidth to BW N With beamwidth BW N The UAV is divided into sectors and numbered, and the beamwidth BW is generated based on the neighbor relationship table N. N The probability distribution P of the number of neighbors in each sector;

[0040] S404: Determine the beamwidth BW based on the probability distribution P. N The node's transmit / receive mode and scanning direction;

[0041] S405: Send or listen for handshake packets according to the determined node transmission and reception mode and scanning direction, and use a two-step handshake for interaction;

[0042] S406: When a new neighbor is discovered, adjust the probability distribution P according to the discovered neighbor relationships and write the neighbor relationship into the neighbor relationship table;

[0043] S407: Determine whether all neighboring nodes have been discovered. If there are still undiscovered neighbors, proceed to step 404; if all neighbors have been discovered, proceed to step S408.

[0044] S408: End the neighbor discovery process.

[0045] As an example, the broadband scanning beamwidth BW W The calculation method is as follows:

[0046] BW W =2π / K1

[0047] in, K2 = 2π / BW N K1 is the beamwidth BW W The number of sectors, K2 refers to the beamwidth BW. N The number of sectors to be divided, where α is a positive integer, if there exist multiple satisfying... If α is less than 10, then K1 takes the value closest to 10, and N... + Represents a positive integer.

[0048] As an example, the process of generating the probability distribution P of the number of neighbors in each sector is as follows:

[0049] Let node i have a beamwidth BW W The neighbor relationships obtained from the scan are as follows:

[0050]

[0051] Where N i Here is the neighbor table for node i, and 0, ..., k1, ..., K1-1 is the beamwidth BW. W The sector numbers below, These refer to the number of neighbors of sector 0, ..., k1, ..., K1-1 of node i, respectively;

[0052] i-node at beamwidth BW W The probability distribution of the number of neighbors in each sector is as follows:

[0053]

[0054] in, It rounds down, where j represents the beamwidth BW. W The j-th sector, j∈[0,K1-1], This represents the number of neighbors of node i in sector j. Indicates that node i is at the 1st rank. The number of neighbors in each sector; For beamwidth BWN The selection probability of the k2th sector.

[0055] As an example, in S406, when the beamwidth BW N After a new neighbor is discovered during the scan, the probability distribution P of the number of neighbors is updated as follows: Suppose a new neighbor is discovered in the k1-th sector, then the probability distribution after discovering a new neighbor is updated as follows:

[0056]

[0057] As an example, in S405, the neighbor discovery two-step handshake process is as follows:

[0058] A node in send mode sends a handshake packet with its own node ID in the first sub-time slot and listens in the second time slot; a node in receive mode listens in the first sub-time slot. If it correctly receives a handshake packet from another node in the first time slot, it sends a reply acknowledgment handshake packet in the second time slot. If it detects a conflicting handshake packet in the second time slot, it does not take any action in the second time slot.

[0059] Example

[0060] The system discovered by the neighbor is as follows: 32 nodes are evenly distributed in a square area with sides of 16 km. Each node is equipped with an adjustable beam antenna, which can transmit and receive signals, but can only transmit or receive signals at any given time. The transmission distance of the antenna is fixed at 5 km, and the time for the antenna to switch between transmit and receive states and perform a handshake is 200 μs. The communication beamwidth between nodes is 6° (i.e., each node has 60 communication sectors). According to the method of this application, the wide beamwidth for node pre-scanning is selected as 36°. Figure 2 As shown. For each node, the antenna beam is first adjusted to 36°, and a neighbor discovery process is performed by randomly selecting transmit / receive states and scanning sectors to generate neighbor relationships N. i Then, based on the neighbor relationship N i Generate sector scan probability distribution P i Then, the antenna beamwidth was adjusted to 6°, and transmit / receive states were randomly selected. Scanning sectors were randomly selected according to the sector scanning probability distribution until the probability distribution decreased to 0. The algorithm was run multiple times, with an average time consumption of 1.33 seconds. To compare the performance of this method, the number of nodes was set between 10 and 150, and this method was compared with a purely random scanning method. The comparison results are as follows. Figure 3 As can be seen, this method can effectively improve the efficiency of neighbor discovery.

Claims

1. A method for neighbor discovery with adjustable beam width for unmanned aerial vehicle ad hoc networks, characterized in that, The method comprises: S401: According to the beam width BW required for data link transmission N Calculate the wideband scanning beam width BW W , BW W >> BW N ; S402: divide and number the sectors of the UAV, discover neighbors, and obtain the beam width BW W S402: divide and number the sectors of the UAV, discover neighbors, and obtain the beam width BW W S402: divide and number the sectors of the UAV, discover neighbors, and obtain the beam width BW S403: adjust the beam width to BW N , the beam width BW N , the beam width BW N , the beam width BW S404: Determine the beam width BW according to the probability distribution P N of the node transceiving mode and the scanning direction; S405: sending or listening to the handshake packet according to the determined node transceiving mode and scanning direction, and interacting by using two-step handshake; S406: when a new neighbor is found, adjusting the probability distribution P according to the found neighbor relationship, and writing the neighbor relationship into a neighbor relationship table; S407: judging whether all neighbor nodes have been found, if there are still some neighbors not found, entering 404; if all neighbors have been found, entering step S408; S408: ending the neighbor discovery process; The wideband scanning beamwidth BW W The calculation method is as follows: BW W = 2π / K1 wherein, K2 = 2π / BW N K1 is the number of sectors divided by the beam width BW W K2 refers to the number of sectors divided by the beam width BW N α is a positive integer, and if there are multiple αs satisfying K1 takes the value closest to 10, N + represents a positive integer; The process of generating the probability distribution P of the number of neighbors in each sector is as follows: Let i node with beam width BW W The scanned neighbor relationship is: where N i is the neighbor list of node i, 0,... k1,..., K1-1 are the numbers of sectors under the beam width BW W of node i, respectively. are the numbers of neighbors of the 0,... k1,..., K1-1 sectors of node i, respectively. The i-nodes have a probability distribution of the number of sector neighbors under a beam width BW W of: wherein, is rounded down, j represents a beam width BW W of the i node in the jth sector, j e [0, K1-1], represents the number of neighbors of the i node in the jth sector, represents the number of neighbors of the i node in the jth sector; is a selection probability of the k2th sector under a beam width BW N .​ In the S406, when the beam width BW N After the scanning discovers the new neighbor, the updating method of the neighbor number probability distribution P is as follows: supposing that a new neighbor is discovered in the k1th sector, the probability distribution is updated after the new neighbor is discovered as follows: 2.The method of claim 1, wherein, In the S405, the two-step handshake process of neighbor discovery is as follows: The node in the sending mode sends a handshake packet with the node ID in the first sub-time slot, and listens in the second time slot; The node in the receiving mode listens in the first sub-time slot, if the handshake packet of other nodes is correctly received in the first time slot, a reply confirmation handshake packet is sent in the second time slot, if a collision handshake packet is detected in the second time slot, no action is taken in the second time slot.

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