A wireless optical network neighbor discovery method

Abstract

The present application belongs to the field of underwater wireless optical communication and network, and proposes a wireless optical network neighbor discovery method. The method utilizes the unique characteristics of two gears with coprime number of teeth, wherein each tooth on one gear periodically engages with each tooth on the other gear, thereby ensuring the alignment of the directional optical transmitter and the directional optical receiver between adjacent nodes. In addition, this characteristic can also ensure the successful transmission and reception of messages between nodes in the case of message collision and interference. Through the wireless optical network neighbor discovery method provided by the present application, distributed directional neighbor discovery can be achieved within a limited delay without any prior information, centralized cooperation and time synchronization.

Description

Technical Field

[0001] This invention belongs to the field of wireless optical communication and network technology, and particularly relates to a method for discovering neighbors in a wireless optical network. Background Technology

[0002] Wireless optical communication uses visible light as its carrier, offering advantages such as high transmission rate, high bandwidth, and high security. A wireless optical network consists of multiple wireless optical communication nodes. Nodes whose wireless signals are reachable within a node's single-hop communication range are called neighbors. During network initialization, two neighboring nodes are unaware of each other's communication range and therefore need to confirm each other's existence through information exchange; this process is called neighbor discovery, which is fundamental to establishing communication between nodes in the network, and its efficiency directly impacts network performance.

[0003] Due to the unique physical characteristics of wireless optical communication, such as the directionality of light beams and line-of-sight communication, when realizing neighbor discovery in a wireless optical network, it is necessary to ensure that the directional light transmitters and receivers of adjacent nodes are aligned. That is, the directional light transmitters and receivers of adjacent nodes should be within the transmission and reception range of each other; at the same time, when one node sends a signal, the other node must be in the receiving state.

[0004] While some neighbor discovery methods related to wireless optical communication exist (e.g., patents CN108834042A and CN110380782A), these methods require omnidirectional transmitting / receiving devices. This not only limits the scope of application but may also reduce security, increase energy consumption, and cause signal interference. Although some neighbor discovery methods employing directional transceivers exist (e.g., patents CN115915086A, CN114845353A, CN114125870A, and CN113453210A), these methods require prior information, centralized cooperation, and time synchronization, which may be difficult to meet in practical applications.

[0005] Therefore, we urgently need a neighbor discovery method for distributed wireless optical networks that is suitable for directional transceivers, requires no prior information, and does not require time synchronization. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention proposes a neighbor discovery method for wireless optical networks. This method utilizes the unique characteristic of two gears with coprime tooth counts, where each tooth on one gear periodically meshes with each tooth on the other. Based on this principle, this method ensures that directional optical transmitters and receivers between adjacent nodes can achieve alignment without any prior information, through centralized cooperation, and with time synchronization. Simultaneously, this characteristic also ensures successful message transmission and reception between nodes in the event of message collisions and interference.

[0007] The technical solution of this invention:

[0008] A method for discovering neighbors in a wireless optical network includes the following steps:

[0009] S1. Each node has a unique identification code ID and is equipped with a directional light transmitter and a directional light receiver for data transmission and reception; the communication radius of the directional light transmitter is R, and the coverage angle is α∈(0). ° 360 ° Within this range, it can send data to other nodes; the coverage angle of the directional optical receiver is β∈(0). ° 360 ° Within this range, it can receive data transmitted from other nodes; each node is equipped with a rotary motor to rotate its directional light transmitter and receiver, and an electronic compass to determine the orientation angle γ∈[0, 1] of its directional light transmitter and receiver relative to the geomagnetic north pole. ° 360 ° Furthermore, each node has the same set of prime numbers, denoted as set P, where each prime number p satisfies 360... ° / p≥min(α,β);

[0010] S2. The node matches a prime number q from set P based on its ID; then, starting from the magnetic north pole, the two-dimensional plane containing the node is divided into q sectors in a clockwise direction, numbered sequentially.

[0011] S3. Starting from any sector, the node continuously rotates its directional light emitter and receiver clockwise or counterclockwise. Each rotation aligns the directions of the node's directional light emitter and receiver with the center direction of its sector. That is, when the node starts rotating from sector a, the angle between the node's rotation and the magnetic north pole is...

[0012] S4. Neighbor discovery is accomplished by nodes exchanging Hello and ACK messages containing node ID and direction information. During rotation, nodes remain in receive mode, continuously receiving data using a directional light receiver. When a node receives an ACK message, it indicates that a neighbor has been successfully discovered and is recorded in the neighbor set. Every q time intervals, nodes switch to transmit mode and send Hello messages using a directional light transmitter. If a node receives a Hello message in receive mode, it will also send an ACK message in response.

[0013] S5, the node rotates by 2(max(P)). 2 After this process, the node stops and is able to successfully discover all neighboring nodes within its communication range.

[0014] The beneficial effects of this invention are:

[0015] 1) The wireless optical network neighbor discovery method provided by this invention can ensure distributed directional neighbor discovery without any prior information, centralized cooperation, or time synchronization.

[0016] 2) The wireless optical network neighbor discovery method provided by this invention can guarantee that any node can be rotated at most 2 (max(P)). 2 Within one time, it can discover all neighboring nodes within its communication range, that is, it can achieve targeted neighbor discovery within a limited delay;

[0017] 3) The wireless optical network neighbor discovery method provided by the present invention can avoid neighbor discovery failure caused by message conflicts and interference. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the node model provided in an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of a three-node wireless optical network provided in an embodiment of the present invention, including its node sector division, node alignment area, and the sectors where the directional light transmitters and receivers of the nodes are located; wherein, (a) shows the relative positions of nodes A, B, and C provided in the embodiment of the present invention, (b) shows the sector division of nodes A, B, and C, (c) shows the alignment area of ​​nodes A and B, (d) shows the alignment area of ​​nodes B and C, and (e) shows the initial direction of the directional light transmitters and receivers of nodes A, B, and C and their respective sectors;

[0020] Figure 3This is a schematic diagram illustrating the alignment of directional light transmitters and receivers between nodes during the wireless optical network neighbor discovery process of three nodes according to an embodiment of the present invention; wherein, (a) is the initial direction of the directional light transmitters and receivers of nodes A, B, and C, (b) is the direction after the first rotation of the directional light transmitters and receivers of nodes A, B, and C, (c) is the direction after the second rotation of the directional light transmitters and receivers of nodes A, B, and C, and (d) is the directional light transmitter of nodes A, B, and C. (e) shows the direction of the directional light emitter and receiver at nodes A, B, and C after the third rotation; (f) shows the direction of the directional light emitter and receiver at nodes A, B, and C after the fourth rotation; (g) shows the direction of the directional light emitter and receiver at nodes A, B, and C after the fifth rotation; (h) shows the direction of the directional light emitter and receiver at nodes A, B, and C after the sixth rotation; (h) shows the direction of the directional light emitter and receiver at nodes A, B, and C after the seventh rotation; and (i) shows the direction of the directional light emitter and receiver at nodes A, B, and C after the seventh rotation. The directions of the light emitter and directional light receiver after the 8th rotation, (j) is the direction of the directional light emitter and directional light receiver of nodes A, B, and C after the 9th rotation, (k) is the direction of the directional light emitter and directional light receiver of nodes A, B, and C after the 10th rotation, (l) is the direction of the directional light emitter and directional light receiver of nodes A, B, and C after the 11th rotation, (m) is the direction of the directional light emitter and directional light receiver of nodes A, B, and C after the 12th rotation, and (n) is the direction of the directional light emitter and directional light receiver of nodes A, B, and C after the 8th rotation. The directions of the directional light emitters and receivers of nodes B and C after the 13th rotation are shown in (o), (p), (q), and (r).

[0021] Figure 4 This is a schematic diagram illustrating the successful sending and receiving of messages between nodes during the wireless optical network neighbor discovery process of three nodes provided in this embodiment of the invention, under conditions of message collision and interference; wherein, (a) shows the time intervals from time t0 to t... 29 A schematic diagram of sending and receiving messages within time t, (b) shows nodes A, B, and C at time t. 30 To t 59 A schematic diagram of sending and receiving messages within time t, where (c) represents nodes A, B, and C at time t. 60 To t 89 A schematic diagram of sending and receiving messages within time t, where (d) represents nodes A, B, and C at time t. 90 To t 119 A diagram illustrating the sending and receiving of messages within the context;

[0022] In the diagram: 1 represents a node, 2 represents the coverage area of ​​the directional light receiver, 3 represents the coverage area of ​​the directional light transmitter, 4 represents the direction of the directional light transmitter and receiver, 5 represents the sectors numbered sequentially after the node divides the two-dimensional plane into equal parts, 6 represents the alignment area between node A and node B, 7 represents the alignment area between node B and node C, 8 represents the sector where the directional light transmitter and receiver of the node are located, 9 represents a node in receiving mode, 10 represents a node in transmitting mode, and 11 represents successful message transmission and reception between nodes. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and technical solutions.

[0024] Example

[0025] A method for discovering neighbors in a wireless optical network includes the following steps:

[0026] S1, such as Figure 1 As shown, each node has a unique identifier (ID) A and is equipped with a directional light transmitter and a directional light receiver for data transmission and reception. The communication radius of the directional light transmitter is R, and the coverage angle is α = 120°. ° Within this range, data can be sent to other nodes. The coverage angle of the directional optical receiver is β = 150°. ° Within this range, data can be received from other nodes. Each node is equipped with a rotary motor to rotate its directional light transmitter and receiver, and an electronic compass to determine the azimuth angle γ of its directional light transmitter and receiver relative to the geomagnetic north pole. Furthermore, all nodes share the same set of prime numbers, denoted as P = {3, 5, 7}, where each prime number p satisfies 360°. ° / p≥120 ° .

[0027] S2, a wireless optical network consisting of nodes A, B, and C, such as Figure 2 As shown in (a). Each node matches a prime number q from set P based on its ID; node A matches the prime number 5, node B matches the prime number 3, and node C matches the prime number 7. Then, as... Figure 2 As shown in (b), each node starts from the geomagnetic north pole and divides the two-dimensional plane in which the node is located into sequentially numbered sectors in a clockwise direction; node A divides the plane into 5 sequentially numbered sectors, node B divides the plane into 3 sequentially numbered sectors, and node C divides the plane into 7 sequentially numbered sectors.

[0028] S3, the relative positions of nodes A, B, and C are as follows: Figure 2As shown in (a), node B is located within the single-hop communication range of node A, and node C is located within the single-hop communication range of node B. From a relative positional perspective, nodes A and B, and nodes B and C, are neighbors. Due to the unique physical characteristics of wireless optical communication, such as the high directionality of the light beam and the line-of-sight communication requirements, when realizing neighbor discovery in a wireless optical network, it is necessary to ensure that the directional light transmitters and receivers of adjacent nodes are aligned; that is, the directional light transmitters and receivers of adjacent nodes should be within each other's transmission and reception range. Therefore, the directional range that satisfies the alignment of the directional light transmitter and receiver is called the alignment area, such as... Figure 2 (c) and Figure 2 As shown in (d), this region is the smallest overlapping area of ​​the coverage of two nodes when their directional light transmitters and receivers are oriented towards each other. Two nodes can be aligned when their directional light transmitters and receivers are simultaneously within this alignment region. Using the neighbor discovery method provided by this invention, nodes can achieve alignment of their directional light transmitters and receivers without any prior information, centralized cooperation, or time synchronization. Figure 2 As shown in (e), the initial directions of the directional light transmitters and receivers at nodes A, B, and C are located in their respective sectors (1st, 2nd, and 3rd), with orientation angles relative to the geomagnetic north pole of respectively. Then, as Figure 3 As shown, nodes A, B, and C continuously rotate their directional light emitters and receivers clockwise. Each rotation aligns the directions of the node's directional light emitters and receivers with the center direction of the node's sector. That is, when the node starts rotating from sector a, the direction angle between the node's b-th rotation and the magnetic north pole is... like Figure 3 As shown in (c), after the second rotation, the directional light emitters and receivers of nodes A and B are simultaneously located within the alignment area, and nodes A and B are aligned; Figure 3 As shown in (r), after the 17th rotation, the directions of the directional light emitters and receivers of nodes A and B are once again simultaneously within the alignment region, and nodes A and B are aligned again; simultaneously, the directions of the directional light emitters and receivers of nodes B and C are also simultaneously within the alignment region, and nodes B and C are aligned; by Figure 3It is known that two nodes can align once within the number of rotations equal to the least common multiple of their matching prime numbers. That is, nodes A and B align once every 15 rotations, and nodes B and C align once every 21 rotations. Therefore, even in the absence of prior information and centralized cooperation among nodes A, B, and C, they can align within the number of rotations equal to the least common multiple of their matching prime numbers. Even in the case of time asynchrony, they can still align the optical transmitter and receiver through multiple rotations.

[0029] S4. Due to the unique physical characteristics of wireless optical communication, when implementing neighbor discovery in a wireless optical network, it is necessary to ensure that when one node sends a signal, the other node is in a receiving state to successfully receive or send a message; in addition, such as Figure 3 As shown in (r), node B is aligned with nodes A and C simultaneously. When nodes A and C send messages to node B at the same time, message collisions and interference occur. Using the neighbor discovery method provided by this invention, nodes can successfully receive and send messages even under message collision and interference conditions. Neighbor discovery is accomplished by nodes exchanging Hello and ACK messages, which contain node IDs and direction information. Throughout the rotation, all nodes remain in receive mode, continuously receiving data using directional light receivers. When a node receives an ACK message, it indicates that a neighbor has been successfully discovered and is recorded in the neighbor set. Nodes A, B, and C switch to transmit mode every 5, 3, and 7 time intervals, respectively, and send Hello messages using directional light transmitters; if a node receives a Hello message in receive mode, it will also send an ACK message in response. Figure 4 As shown, message collisions and interference between any two nodes occur only when their respective time intervals are common multiples; within the least common multiple period of all node time intervals, i.e., from t0 to t... 104 In 105 time intervals, node A sent 21 messages, node B sent 35 messages, and node C sent 15 messages. Even with message conflicts and interference, node B was still able to successfully send and receive messages with node A 36 times and with node C 32 times. Therefore, even with message conflicts and interference, lack of prior information, lack of centralized cooperation, and lack of time synchronization among nodes A, B, and C, they can still successfully send and receive messages within the least common multiple of all node time intervals.

[0030] S5, nodes A, B, and C rotate by 2(max(P)). 2=After 98 rotations, the process stops. During these 98 rotations, node A and node B achieve alignment once every 15 rotations, and node B and node C achieve alignment once every 21 rotations. Throughout the rotation process, nodes A, B, and C are able to successfully receive and send messages despite message conflicts and interference. Therefore, nodes A, B, and C successfully discover all neighboring nodes within their communication range.

Claims

1. A method for neighbor discovery in a wireless optical network, characterized in that, Includes the following steps: S1. Each node has a unique identification code ID and is equipped with a directional light transmitter and a directional light receiver for data transmission and reception; the communication radius of the directional light transmitter is R, and the coverage angle is α∈(0). ° 360 ° Within this range, it can send data to other nodes; the coverage angle of the directional optical receiver is β∈(0). ° 360 ° Within this range, it can receive data transmitted from other nodes; each node is equipped with a rotary motor to rotate its directional light transmitter and receiver, and an electronic compass to determine the orientation angle γ∈[0, 1] of its directional light transmitter and receiver relative to the geomagnetic north pole. ° 360 ° Furthermore, each node has the same set of prime numbers, denoted as set P, where each prime number p satisfies 360... ° / p≥min(α,β); S2. The node matches a prime number q from set P based on its ID; then, starting from the magnetic north pole, the two-dimensional plane containing the node is divided into q sectors in a clockwise direction, numbered sequentially. S3. Starting from any sector, the node continuously rotates its directional light emitter and receiver clockwise or counterclockwise. Each rotation aligns the directions of the node's directional light emitter and receiver with the center direction of its sector. That is, when the node starts rotating from sector a, the angle between the node's rotation and the magnetic north pole is... S4. Neighbor discovery is accomplished by exchanging Hello and ACK messages containing node ID and direction information between nodes. During rotation, the node remains in receive mode and continuously receives data using a directional light receiver. When a node receives an ACK message, it indicates that it has successfully discovered a neighbor and records it in the neighbor set. Every q time interval, the node switches to transmission mode and sends a Hello message using a directional light transmitter; if the node receives a Hello message in receive mode, it will also send an ACK message in response. S5, the node rotates by 2(max(P)). 2 After this process, the node stops and is able to successfully discover all neighboring nodes within its communication range.

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