A location service method for a VBF routing protocol of an underwater acoustic network

Abstract

The application provides a position service method for an underwater acoustic network VBF routing protocol, which realizes local node position coordinate calculation through a distributed ranging and three-side positioning method and designs a deviation elimination mechanism, and finally obtains absolute coordinates of all nodes in the network through network transmission of node position information, fusion and conversion of multiple coordinate systems. The method does not need to deploy positioning beacons and GPS signals, and realizes self-organization of positioning of all nodes in the network, can provide position service for the underwater acoustic network VBF routing protocol, improves routing efficiency and reliability, and has high engineering practical value.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic communication network technology, specifically relating to a location service method for the VBF routing protocol in underwater acoustic networks. Background Technology

[0002] Underwater acoustic networks, as an important means of underwater information transmission, play a crucial role in fields such as marine resource exploration, environmental monitoring, and military security. However, the unique characteristics of the underwater environment pose significant challenges to the design of routing protocols for underwater acoustic networks. Compared with terrestrial wireless communication, underwater acoustic channels are characterized by narrow bandwidth, long propagation delay, severe signal attenuation, and significant multipath effects. These characteristics make traditional terrestrial routing protocols unsuitable for direct application in underwater environments. Vector forwarding (VBF) based routing protocols are among the most widely used routing protocols in underwater acoustic networks. VBF establishes a virtual pipe between the source and destination nodes, limiting the forwarding area of ​​data packets, and offers advantages such as good robustness and relatively controllable energy consumption.

[0003] However, the VBF protocol has the following three problems:

[0004] (1) Strong dependence on location information:

[0005] The VBF protocol requires network nodes to obtain their own location information in advance. However, in actual underwater deployments, GPS signals cannot penetrate the water surface, making it difficult to obtain the node's location. Traditional methods for obtaining their own location information rely on surface buoys or fixed beacon nodes, but beacon deployment is costly, inflexible, and difficult to maintain accurate positioning in dynamic underwater environments.

[0006] (2) Sparse network performance degradation:

[0007] In sparsely populated network environments, insufficient nodes within the routing pipeline can easily lead to routing holes and packet loss. Although the HH-VBF protocol improves packet delivery rates in sparse networks by establishing routing pipelines hop-by-hop, it still does not fundamentally solve the problem of location information acquisition.

[0008] (3) Uneven energy consumption:

[0009] In the VBF protocol, nodes close to the routing vector frequently forward data packets, causing these nodes to rapidly deplete their energy, creating energy holes and shortening network lifetime. Although existing improved protocols consider the remaining energy factor, the uncertainty of location information still limits the effectiveness of energy balancing strategies.

[0010] In summary, existing underwater acoustic network location service methods have the following problems that urgently need to be solved: ① Location information acquisition depends on external beacons, resulting in high deployment costs and poor flexibility; ② The VBF routing protocol requires prior knowledge of node locations, limiting its application in dynamic networks; ③ Existing positioning methods are complex and energy-intensive, making them unsuitable for large-scale distributed networks; ④ There is a lack of distributed positioning schemes that can be seamlessly integrated with the VBF routing protocol. Summary of the Invention

[0011] The technical problem this invention aims to solve is the high dependence of the VBF routing protocol in underwater acoustic networks on node location information, and the issues of existing positioning methods requiring external beacons or GPS signals, resulting in high deployment costs and poor flexibility. To address this, a location service method for the VBF routing protocol in underwater acoustic networks is provided. This method uses distributed ranging, trilateration, and a bias elimination mechanism to calculate local node coordinates. Through networked transmission of node location information, multi-coordinate system fusion, and transformation, the location coordinates of all nodes in the network are obtained, thereby providing location services for the VBF routing protocol in underwater acoustic networks.

[0012] The technical solution adopted in this invention is as follows:

[0013] A location service method for the VBF routing protocol in underwater acoustic networks, characterized by the following steps:

[0014] Step S1: Distributed Network Ranging: Nodes within the network use a multi-round ping-echo mechanism to perform underwater acoustic ranging with neighboring nodes within a one-hop range to obtain local distance information. The ping-echo mechanism includes: the initiating node broadcasts a ping frame, neighboring nodes reply with echo frames after random backoff, and the initiating node calculates the distance to each neighboring node based on the response delay. When a ping frame is sent for the first time, the destination address is the broadcast address, and all neighboring nodes must reply. When the ping frame is sent again, the destination address is the set of node addresses that have not yet been successfully ranging, in order to avoid duplicate responses and improve efficiency. After obtaining the distances of all one-hop neighbors, the node broadcasts the ranging results to its neighboring nodes.

[0015] Step S2: Local coordinate system construction and coordinate calculation: Select a local center node, use it as the origin, and establish a local Cartesian coordinate system using the lines connecting it to two specific neighboring nodes as coordinate axes; Based on the distance between nodes obtained in Step S1, use the triangle cosine theorem and the trilateration method to calculate the coordinates of all neighboring nodes within one hop of the center node in the local coordinate system; For node coordinates with mirror ambiguity, calculate the theoretical distance to the third reference node and compare it with the measured distance, discard mirror solutions with large deviations, and determine the unique coordinates;

[0016] Step S3: Global Coordinate System and Location Service: Collect node coordinates in multiple local coordinate systems established by different local central nodes through network flooding; using a certain local coordinate system as the reference global coordinate system, transform the node coordinates in other local coordinate systems to the global coordinate system by calculating the rotation angle and translation vector between the coordinate axes, and finally obtain the absolute coordinates of all nodes in the network; broadcast the unified global coordinates to the entire network by the central node to provide location information services for the VBF routing protocol.

[0017] In step S1, the ping frame and echo frame are network control frames of a specific format; the control frame includes control frame type, control frame length, source address, destination address, and data field; when the control frame type is 0, it represents a ping frame, and the data field is empty; when the control frame type is 1, it represents an echo frame, and the data field is the backoff time; when the control frame type is 2, it represents a frame carrying distance information, and the data field is the set of distance pairs between nodes {(i,j,d)}. i,j )}, where i and j are node addresses, and d i,j The distance between nodes i and j; when the control frame type is 3, it represents a frame carrying location information, and the data field is the set of node coordinates {(x... i y i )}.

[0018] In step S2, the specific method for establishing a local planar rectangular coordinate system is as follows: the coordinate system is established with the local center node as the origin, the direction from the center node to the first neighbor node as the positive x-axis, and the direction perpendicular to the x-axis and pointing to the second neighbor node as the positive y-axis.

[0019] In step S2, the specific process of calculating the coordinates of neighboring nodes includes: for the local center node origin o, node i on the x-axis, and node j to be determined, given the node spacing, the coordinates of nodes i and j are obtained using the cosine theorem and the trilateration method:

[0020] x i =d i,o y i =0,

[0021] x j =d o,j cosα, y j =d o,j sinα,

[0022] ,

[0023] in, for .

[0024] In step S3, the specific mathematical expression of the coordinate system transformation is as follows: for the node coordinates (x, y, z) in the coordinate system to be transformed... ’ ,y ’ Its coordinates (x, y) in the target's global coordinate system are obtained through the following rotation and translation transformations:

[0025] ,

[0026] Where (x0, y0) are the coordinates of the origin of the coordinate system to be transformed in the target global coordinate system, and β is the angle between the x-axis of the two coordinate systems.

[0027] Compared with existing technologies, the beneficial effects of the present invention are as follows:

[0028] 1. It can achieve full network node positioning without the need to deploy external beacons and GPS signals;

[0029] 2. By using coordinate system fusion and deviation elimination mechanisms, the impact of ranging errors on positioning accuracy is reduced;

[0030] 3. Directly provide location information for VBF routing, improving routing efficiency and reliability. Attached Figure Description

[0031] Figure 1 This is a diagram of the network control frame format of the present invention;

[0032] Figure 2 This is a schematic diagram of measuring the distance between nodes within one hop of the entire network according to the present invention, wherein: (a) is a schematic diagram of nodes 3, 8, and 13 obtaining the distance of neighboring nodes by ping-echo; (b) is a schematic diagram of other nodes obtaining the distance of neighboring nodes by ping-echo after nodes 3, 8, and 13 broadcast their distances to neighboring nodes.

[0033] Figure 3 The following is a diagram showing the coordinate positions of the nodes calculated according to the present invention: (a) is a diagram showing the calculation of the coordinates of all nodes within a jump from node 3 in a coordinate system with node 3 as the origin, nodes 3 and 7 as the x-axis, and the direction perpendicular to the x-axis and pointing to node 5 as the positive y-axis; (b) is a diagram showing the calculation of the coordinates of all nodes within a jump from node 8 in a coordinate system with node 8 as the origin, nodes 5 and 8 as the x'-axis, and the direction perpendicular to the x'-axis and pointing to node 10 as the positive y'-axis. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments and accompanying drawings:

[0035] First, the network control frame format involved in this invention is defined, and its structure is as follows: Figure 1As shown. The control frame length field indicates the number of bytes in the entire control frame. When the destination address field is 0, it indicates that the control frame is a broadcast frame; if the destination address field is not 0, it indicates a non-broadcast frame, and the destination address can be a set of multiple addresses. When the control frame is a ping frame, the control frame type is 0, and the data field is empty; when the control frame is an echo frame, the control frame type is 1, and the data field is the backoff time; when the control frame carries distance information, the control frame type is 2, and the data field is the distance between nodes {(i,j,d)}. i,j )}, where i and j are node addresses, and d i，j The distance between nodes i and j can be multiple; when the control frame carries location information, the control frame type is 3, and the data field is the node position {(x i y i )},(x i y i ) represents the coordinates of node i, and there can be multiple node positions.

[0036] Taking 16 nodes as an example, for each node, the total number of nodes in the network is known, but the location of each node is unknown. The method of this invention obtains the location of each node as follows:

[0037] Step 1: Measure the distance between nodes within a one-hop range across the entire network:

[0038] After the nodes are deployed, the spatial relationships are as follows: Figure 2 As shown. Without loss of generality, assume the ping is initiated by node 3. 3 The signal is all nodes within a one-hop range of node 3 (e.g., Figure 2 (a) Nodes 1, 2, 4, 5, 6, and 7 received pings. 3 The signal is emitted via a random backoff mechanism. j Signal. This invention stipulates that all nodes within one hop of node 3 are not allowed to send ping signals until they receive ranging information broadcast by node 3. Node 3 calculates the distance d with its neighboring nodes by measuring the response delay. 3，j , t ping，j It is expressed as follows:

[0039] ,j=1,2,4,5,6,7 (1)

[0040] In equation (1), c is the speed of sound, and t ping，3 Send ping to node 3 3 Signal time, t echo，j For node 3 to receive the echo from node j j Signal time, t back，jLet be the random backoff time for node j. Generally, even with random backoff, sending echo frames may still result in collisions, causing node 3 to fail to receive the echo signal correctly. Multiple ping frames can be sent to ensure correct reception of echo signals from all neighboring nodes. When node 3 has not received an echo frame, it indicates that node 3 has received echo frames from all neighboring nodes, and the ping frame sending ends. This invention specifies that the destination address is 0 when the first ping frame is sent, and all neighboring nodes receiving the ping frame must reply with an echo frame. For subsequent ping frame sending, the destination address set is... At this point, `i` represents the node address corresponding to the measured distance. Only nodes whose own address `j` is not in set `i` will send an echo frame. After obtaining the distances of all neighboring nodes, node 3 broadcasts the distance measurement status to its neighbors. During the distance measurement process between node 3 and its neighbors, nodes 8 and 13, which are outside the one-hop range of node 3, can also synchronously obtain the distances of their neighbors via ping-echo. The process is not described in detail here. Figure 2 As shown in (a).

[0041] After node 3 broadcasts its distance to its neighbors, other nodes initiate a ping-echo process to measure their distance to their own neighbors, such as... Figure 2 As shown in (b), assume that node 2 initiates the ping first. 2 Since the distance between node 2 and node 3 has been measured through the above process, the first ping signal is sent. 2 The destination node field of the frame is 3. Nodes 1 and 4, which are within one hop of node 2, receive the ping. 2 After the first frame, an echo frame is sent back. Node 2 measures its distances to nodes 1 and 4 and broadcasts these distance values ​​to nodes 1, 3, and 4. During the distance measurement process between node 2 and its neighbors, other nodes outside node 2's one-hop range (such as nodes 6, 15, 12, 11, and 5) can initiate a ping-echo process to measure their distances to their neighbors, and then send the measurement results to their neighbors. At this point, every node in the network knows its distance to its neighbors.

[0042] Step 2: Calculate the coordinates of nodes within one hop range:

[0043] like Figure 3 As shown in (a), a coordinate system (x, y) is established with node 3 as the origin, nodes 3 and 7 as the x-axis, and the direction perpendicular to the x-axis and pointing towards node 5 as the positive y-axis. Through step 1, the distances between nodes 3 and 5, nodes 3 and 7, and nodes 5 and 7 are known to be d. 3,5 d 3,7 d 5,7 In this coordinate system, the coordinate positions of the three nodes are calculated as follows:

[0044] x3=0; y3=0; (2)

[0045] x7=d 3,7 ;y7=0;(3)

[0046] x5=d 3,5 cosα;y5=d 3,5 sinα; (4)

[0047] (5)

[0048] In this coordinate system, following the same method as equations (5) and (6), the coordinates of all nodes (nodes 1, 2, 4, 5, 6, 8) within a one-hop range from node 3 can also be calculated. Without loss of generality, taking node 1 as an example, the coordinates of node 1 are:

[0049] x1=d 3,1 cosα ’ y1=±d 3,1 sinα ’ (6)

[0050] (7)

[0051] At this point, there should be two calculated y-axis values ​​for node 1. These can be determined by calculating the distance between node 1 and node 5.

[0052] (8)

[0053] Distance d measured 1,5 The deviation is used to eliminate those that are excluded; the larger the deviation, the more likely they are to be excluded (assuming...). Figure 3 Solution of the mirror coordinates of node 1 in (a) If the positional deviation from 5 is large, then the node (Removed).

[0054] like Figure 3 As shown in (b), with node 8 as the origin and nodes 5 and 8 as the x-axis, ’ The axis, perpendicular to x ’ The axis and the direction pointing to node 10 is y ’ Establish a coordinate system in the positive direction of the x-axis (x-axis) ’ ,y ’ Following the same calculation method described above, the coordinates (x, y) of all nodes within a one-hop range of node 8 can be calculated. i ’ y i ’ ), i=7, 5, 10, 11, 9, 12.

[0055] With node 13 as the origin and nodes 6 and 13 as the coordinate origin... Axis, perpendicular to The axis and the direction pointing to node 7 are Establish a coordinate system in the positive direction of the axis ( , Following the same calculation method described above, the coordinates of all nodes within a one-hop range of node 13 can be calculated. , ), i=6, 7, 12, 14, 15, 16.

[0056] Step 3: Calculate the coordinates of all nodes in the network:

[0057] Since each node is unaware of the coordinates of other nodes after deployment, and cannot access nodes outside its one-hop range via geolocation routing protocols, nodes 3, 8, and 13 can use a flooding routing protocol to broadcast the coordinates of their respective neighboring nodes. Without loss of generality, assuming node 3 first collects the coordinates of the neighboring nodes of nodes 8 and 13, calculating the coordinates of all nodes in the entire network centered on node 3 becomes a process of converting the coordinate system (x...)... ’ ,y ’ The process of transforming all nodes of a coordinate system (x, y) into coordinates of the coordinate system is calculated using the following formula:

[0058] (9)

[0059] (10)

[0060] Equation (10) β is x ’ The angle between the axis and the x-axis (e.g.) Figure 3 As shown in (b), i = 10, 11, 9, 12.

[0061] coordinate system ( , Transform all nodes of ) into coordinates of coordinate system (x, y), and calculate the coordinates using the following formula:

[0062] (11)

[0063] (12)

[0064] In equation (12), γ is The angle between the axis and the x-axis (e.g.) Figure 3 (as shown in (b)), k=14, 15, 16.

[0065] Finally, node 3 broadcasts the calculated coordinates of all nodes in the unified coordinate system to all other nodes in the network. All nodes in the network then know the coordinates of other nodes, thus achieving the goal of providing location services for the underwater acoustic network VBF routing protocol.

Claims

1. A location service method for the VBF routing protocol in underwater acoustic networks, characterized in that: Includes the following steps: Step S1: Distributed network ranging: Nodes within the network use a multi-round ping-echo mechanism to perform underwater acoustic ranging with neighboring nodes within a one-hop range to obtain local distance information; Step S2: Local coordinate system construction and coordinate calculation: Select a local center node, take it as the origin, and use the lines connecting it to two specific neighboring nodes as coordinate axes to establish a local Cartesian coordinate system; Step S3: Global Coordinate System and Location Service: Collect node coordinates in multiple local coordinate systems established by different local central nodes through network flooding; using a certain local coordinate system as the reference global coordinate system, transform the node coordinates in other local coordinate systems to the global coordinate system by calculating the rotation angle and translation vector between the coordinate axes, and finally obtain the absolute coordinates of all nodes in the network; broadcast the unified global coordinates to the entire network by the central node to provide location information services for the VBF routing protocol.

2. The location service method for VBF routing protocol in underwater acoustic networks according to claim 1, characterized in that: The ping-echo mechanism includes: the initiating node broadcasts a ping frame, neighboring nodes reply with an echo frame after random backoff, and the initiating node calculates the distance to each neighboring node based on the response delay; when sending a ping frame for the first time, the destination address is the broadcast address, and all neighboring nodes must reply; when sending a ping frame for the second time, the destination address is the set of node addresses that have not yet been successfully distanced, in order to avoid duplicate responses and improve efficiency; after obtaining the distances of all one-hop neighbors, the node broadcasts the distance measurement results to notify the neighboring nodes.

3. The location service method for the VBF routing protocol in underwater acoustic networks according to claim 2, characterized in that: In step S1, the ping frame and echo frame are network control frames of a specific format; the control frame includes control frame type, control frame length, source address, destination address, and data field; when the control frame type is 0, it represents a ping frame, and the data field is empty; when the control frame type is 1, it represents an echo frame, and the data field is the backoff time; when the control frame type is 2, it represents a frame carrying distance information, and the data field is the set of distance pairs between nodes {(i,j,d)}. i,j )}, where i and j are node addresses, and d i,j The distance between nodes i and j; when the control frame type is 3, it represents a frame carrying location information, and the data field is the set of node coordinates {(x... i y i )}.

4. The location service method for the VBF routing protocol in underwater acoustic networks according to claim 3, characterized in that, Based on the distance between nodes obtained in step S1, the coordinates of all neighboring nodes within one hop of the central node in the local coordinate system are calculated using the triangle cosine theorem and the trilateration method. For node coordinates with mirror ambiguity, the theoretical distance between the node and the third reference node is calculated and compared with the measured distance. Mirror solutions with large deviations are eliminated to determine the unique coordinates.

5. The location service method for the VBF routing protocol in underwater acoustic networks according to claim 4, characterized in that, In step S2, the specific method for establishing a local planar rectangular coordinate system is as follows: the coordinate system is established with the local center node as the origin, the direction from the center node to the first neighbor node as the positive x-axis, and the direction perpendicular to the x-axis and pointing to the second neighbor node as the positive y-axis.

6. The location service method for the VBF routing protocol in underwater acoustic networks according to claim 5, characterized in that, In step S2, the specific process of calculating the coordinates of neighboring nodes includes: for the local center node origin o, node i on the x-axis, and node j to be determined, given the node spacing, the coordinates of nodes i and j are obtained using the cosine theorem and the trilateration method: x i =d i,o ,y i =0, x j =d o,j cosα,y j =d o,j sinα, ， Where α is .

7. The location service method for VBF routing protocol in underwater acoustic networks according to any one of claims 1-6, characterized in that, In step S3, the specific mathematical expression of the coordinate system transformation is as follows: for the node coordinates (x, y, z) in the coordinate system to be transformed... ， y ， Its coordinates (x, y) in the target's global coordinate system are obtained through the following rotation and translation transformations: ， Where (x0, y0) are the coordinates of the origin of the coordinate system to be transformed in the target global coordinate system, and β is the angle between the x-axis of the two coordinate systems.

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