A time slot mac method for a non-third-party node access-restricted underwater acoustic network

Abstract

The application discloses a time slot MAC method for an underwater acoustic network with non-self node access restriction. In the method, underwater nodes send data to receiving nodes in parallel by using a time slot access mode, time delay, energy and control packet overhead caused by arranging access time for underwater nodes one by one are avoided, and a relative spatial relationship problem is exposed, meanwhile, the MAC method can still realize maximum access capacity. The application utilizes space-time coupling characteristics of medium access in the underwater acoustic network, and can effectively reduce the number of data packets received by non-self nodes at other positions without collision while realizing maximum throughput of self receiving nodes.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic sensor networks and relates to a time-slot MAC method for underwater acoustic networks with restricted access for non-friendly nodes. Background Technology

[0002] The main characteristic of underwater acoustic MAC is its space-time coupling, meaning that due to the underwater acoustic propagation speed, which is five orders of magnitude slower than radio waves, the arrival time of data packets is determined by both the transmission time and the spatial location between the transmitter and receiver. In contrast, in radio communication, the arrival time of a data packet at the receiver can be approximated by its transmission time. This space-time coupling characteristic makes MAC protocols used in radio networks unsuitable for underwater acoustic networks, necessitating the development of underwater acoustic MAC protocols that incorporate this feature.

[0003] Existing underwater acoustic MAC protocols have conducted extensive research on how to leverage space-time coupling characteristics to improve the throughput of underwater acoustic MAC. However, there are still significant limitations in utilizing space-time coupling characteristics to improve the throughput of friendly nodes while reducing the throughput of non-friendly nodes. From the perspective of media access control, based on space-time coupling characteristics, a set of data packets may be successfully received only at the target receiver, while colliding at non-target receivers. In contrast, since data packets are successfully received at both target and non-target receivers simultaneously without collision, radio networks cannot achieve differentiated control of media access control layer throughput between different nodes.

[0004] Considering the openness and potential risks of the marine environment, while utilizing the spatiotemporal coupling characteristics to achieve high network capacity, the design of underwater acoustic MAC urgently needs to specifically design access strategies and spatial relationships between network nodes to suppress the probability of collision-free reception at non-friendly nodes.

[0005] Existing research on MAC (Macro-Access Control) for data acquisition by a single receiving node in underwater networks is mostly limited to improving the efficiency of MAC access, without considering application scenarios involving non-friendly nodes. During the operation of existing MAC methods, the initialization process requires each receiving node to determine its initial transmission time with the sending node through control signaling. Non-friendly nodes can utilize this initialization information and the topology information of the sending node to reconstruct the relative topology relationship between the receiving and sending nodes, thereby achieving efficient or even perfect collision-free data reception (Chen Weiqi. Reliable Networking and Transmission Technology for Underwater Acoustic Networks [D]. South China University of Technology [2024-01-22].). Summary of the Invention

[0006] The purpose of this invention is to fill the gap in the existing technology and provide a slotted MAC method for underwater acoustic networks with limited access for non-owning nodes.

[0007] The objective of this invention is achieved by at least one of the following technical solutions.

[0008] A time-slot MAC method for restricted access to underwater acoustic networks by non-friendly nodes, characterized by the following steps:

[0009] S1. N underwater nodes are deployed in the observation area to collect underwater data. The collected data will first be stored in the local cache of the underwater nodes. The unmanned underwater vehicle will periodically go to the observation area to collect the data cached by the N underwater nodes through underwater acoustic communication.

[0010] S2. Each underwater node sends data to the unmanned underwater vehicle (UUV) via time-slot access. The UUV sets the size B and time slot length T of the data packets sent by each underwater node for this data acquisition task according to requirements. slot This ensures that data packets are received and aligned only at their positions within the location set P.

[0011] S3. The unmanned underwater vehicle randomly selects a location from the given location set P as its receiving location for this data acquisition task, so as to protect its own location information.

[0012] S4. After the unmanned underwater vehicle reaches the selected receiving position, it broadcasts an Ini control packet to the underwater node, and the data acquisition task enters the initialization phase. The Ini control packet carries the initial access timestamp T0 and the time slot length T. slot ;

[0013] S5, the unmanned underwater vehicle will wait for a period of time after sending the Ini control packet. To receive ACK packets from underwater nodes;

[0014] S6. After receiving the Ini control packet, the underwater node sets the access policy according to the information in the Ini control packet and waits for a period of time. Then send an ACK confirmation packet to the unmanned underwater vehicle;

[0015] S7, waiting for delay Afterwards, the unmanned underwater vehicle will check whether it has received ACK confirmation packets from N underwater nodes. If less than N ACK confirmation packets are received, the unmanned underwater vehicle will update the initial access timestamp T0 in the Ini control packet to obtain a new Ini control packet, and broadcast the new Ini control packet to the underwater nodes to restart the initialization phase. When it is confirmed that N ACK confirmation packets have been received, the data acquisition task enters the data collection phase, and the unmanned underwater vehicle waits to receive data packets sent by the underwater nodes.

[0016] S8. During the data collection phase, the underwater node starts from time T0 and collects data every T interval... slot Send a data packet of size B.

[0017] Furthermore, in step S1, all underwater nodes are deployed in a chain at equal intervals at the same depth. It is assumed that the three-dimensional coordinates of two adjacent underwater nodes are represented as (x1, y1, z). d ),(x2,y2,z d It should meet the following conditions:

[0018] |x1-x2|=l,

[0019] y1-y2=0

[0020] Where z d The depth at which the sensor nodes are deployed is indicated, and l represents the distance difference between two adjacent underwater nodes.

[0021] Assume the three-dimensional coordinates of the underwater node at one end of the linear underwater node chain are represented as (x0, y0, z). d If the three-dimensional coordinates of the underwater node at the other end are:

[0022] (x0+(N-1)l,y0,z d ).

[0023] Furthermore, in step S2, the formula for calculating the data packet size is as follows:

[0024]

[0025] Where B is in bytes, v represents the speed of sound in water, r represents the transmission rate of the underwater acoustic communication device (in bits per second), and the parameter γ is either 0 or 1, depending on the trade-off between the underwater node's requirement to restrict access from non-friendly nodes and the number of elements in the unmanned underwater vehicle's location set P.

[0026] When γ = 0, fewer data packets can be received without collision by non-friendly nodes, but the number of elements in the location set P provided to the unmanned underwater vehicle is 2.

[0027] When γ = 1, the number of elements in the position set P is 4.

[0028] Furthermore, in step S2, the formula for calculating the time slot length is as follows:

[0029]

[0030] Where r represents the transmission rate of the underwater acoustic communication device.

[0031] Furthermore, in step S5, the waiting delay T set after the unmanned underwater vehicle broadcasts the Ini control packet. D 1 The calculation formula is:

[0032]

[0033] Where τ represents the maximum propagation delay from the underwater node to the unmanned underwater vehicle, and T Ini-pkt T represents the transmission delay of the Ini control packet. ACK-pkt This indicates the transmission delay of the ACK confirmation packet.

[0034] Furthermore, in step S6, after receiving the initial control packet, the underwater node will wait for a certain time delay before sending back a confirmation control packet. The following conditions must be met:

[0035]

[0036] Among them, T Ini-pkt This indicates the transmission delay of the Ini control packet.

[0037] Furthermore, in step S4, the initial access timestamp T0 should meet the following condition:

[0038]

[0039] Among them, T c T represents the time when the unmanned underwater vehicle broadcasts the current Ini control packet, τ represents the maximum propagation delay from the underwater node to the unmanned underwater vehicle, and T represents the maximum propagation delay from the underwater node to the unmanned underwater vehicle. Ini-pkt T represents the transmission delay of the Ini control packet. ACK-pkt This indicates the transmission delay of the ACK confirmation packet.

[0040] Furthermore, in step S8, the formula for calculating the transmission time of the kth time slot of the underwater node is:

[0041]

[0042] in, It is a set of positive integers.

[0043] Furthermore, in step S3, when N mod 2 = 0 and γ = 1, the formula for calculating the position set P is:

[0044]

[0045] When N mod 2 ≠ 0 and γ = 1, the formula for calculating the position set P is:

[0046]

[0047] When N mod 2 = 0 and γ = 0, the formula for calculating the location set P is:

[0048]

[0049] When N mod 2 ≠ 0 and γ = 0, the formula for calculating the position set P is:

[0050]

[0051] Where l represents the distance difference between two adjacent underwater nodes.

[0052] Furthermore, unmanned underwater vehicles should have the ability to self-locate underwater and perceive their surroundings.

[0053] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0054] In this invention, underwater nodes send data to the receiving point in parallel using a time-slot access method, avoiding the latency, energy and control packet overhead caused by scheduling access time for each underwater node individually, and avoiding the exposure of relative spatial relationship problems. At the same time, this MAC method can still achieve the maximum access capacity.

[0055] This invention fully utilizes the spatiotemporal coupling characteristics of underwater acoustic network media access. When the receiving node is in a given location, it can achieve the maximum access capacity, while non-receiving nodes in other locations will experience a large number of data packet collisions, thereby restricting access to the target to non-receiving nodes. Attached Figure Description

[0056] Figure 1 This is a time-slot MAC flowchart of a non-self node access restricted underwater acoustic network according to the present invention;

[0057] Figure 2 This is a schematic diagram illustrating the workflow of a slotted MAC method for restricted access to underwater acoustic networks by non-friendly nodes in one embodiment of the present invention.

[0058] Figure 3 This is a schematic diagram of the spatial relationship between nodes in a time-slotted MAC method for restricted access to underwater acoustic networks by non-friendly nodes in one embodiment of the present invention.

[0059] Figure 4 The average performance result of the slotted MAC method for underwater acoustic networks with restricted access for non-friendly nodes in one embodiment of the present invention was obtained by performing 1000 simulations using the NS-3 network simulator. Detailed Implementation

[0060] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the scope of the embodiments described.

[0061] Example:

[0062] A slotted MAC method for accessing restricted underwater acoustic networks by non-friendly nodes, such as... Figure 1 As shown, it includes the following steps:

[0063] S1. Three underwater nodes are deployed in the observation area to collect underwater data. The collected data will first be stored in the local cache of the underwater nodes. The unmanned underwater vehicle will periodically go to the observation area to collect the data cached by the three underwater nodes through underwater acoustic communication.

[0064] In one embodiment, the unmanned underwater vehicle has the ability to self-locate underwater and perceive its surroundings.

[0065] In one embodiment, the underwater acoustic communication rate between the unmanned underwater vehicle and the underwater node is 4kbps, and the underwater node is deployed at a depth of 500m.

[0066] All underwater nodes are deployed in a chain at equal intervals at the same depth. Assume the three-dimensional coordinates of two adjacent underwater nodes are represented as (x1, y1, z). d ), (x2, y2, z d It should meet the following conditions:

[0067] |x1-x2|=l,

[0068] y1-y2=0

[0069] In one embodiment, z d =500m represents the depth at which the sensor node is deployed, and l=1500m represents the distance difference between two adjacent underwater nodes;

[0070] Assume the three-dimensional coordinates of the underwater node at one end of the linear underwater node chain are represented as (x0, y0, z0). d If the three-dimensional coordinates of the underwater node at the other end are:

[0071] (x0+(N-1)l,y0,z d ).

[0072] In one embodiment, if the three-dimensional coordinates of the underwater node at one end of the linear underwater node chain are represented as (0, 0, 500), then the three-dimensional coordinates of the underwater node at the other end are:

[0073] (3000, 0, 500).

[0074] S2. Each underwater node sends data to the unmanned underwater vehicle (UUV) via time-slot access. The UUV sets the size B and time slot length T of the data packets sent by each underwater node for this data acquisition task according to requirements. slot This is to achieve reception alignment by realizing the position of data packets in the location set P;

[0075] The formula for calculating the data packet size is as follows:

[0076]

[0077] In one embodiment, v = 1500 m / s represents the speed of sound in water, r = 4000 bps represents the transmission rate of the underwater acoustic communication device, and the parameter γ is set to 0. Therefore, B = 250 Bytes can be obtained from the above formula.

[0078] The formula for calculating the time slot length is as follows:

[0079]

[0080] Where r represents the transmission rate of the underwater acoustic communication device.

[0081] In one embodiment, T slot =1.5s.

[0082] S3. The unmanned underwater vehicle randomly selects a location from the given location set P as its receiving location for this data acquisition task, so as to protect its own location information.

[0083] When N mod 2 = 0 and γ = 1, the formula for calculating the location set P is:

[0084]

[0085] When N mod 2 ≠ 0 and γ = 1, the formula for calculating the position set P is:

[0086]

[0087] When N mod 2 = 0 and γ = 0, the formula for calculating the location set P is:

[0088]

[0089] When N mod 2 ≠ 0 and γ = 0, the formula for calculating the position set P is:

[0090]

[0091] Where l represents the distance difference between two adjacent underwater nodes.

[0092] In one embodiment, 3 mod 2 = 0, γ = 0, and the formula for calculating the position set P is:

[0093] P={(1125,0,500),(1875,0,500)}.

[0094] S4. After the unmanned underwater vehicle reaches the selected receiving location, if Figure 2 As shown, the unmanned underwater vehicle broadcasts an Ini control packet to the underwater node, initiating the data acquisition task into the initialization phase. The Ini control packet carries the initial access timestamp T0 and the timeslot length T. slot;

[0095] The initial access timestamp T0 should meet the following conditions:

[0096] Among them, T c T represents the time when the unmanned underwater vehicle broadcasts the current Ini control packet, τ represents the maximum propagation delay from the underwater node to the unmanned underwater vehicle, and T represents the maximum propagation delay from the underwater node to the unmanned underwater vehicle. Ini-pkt T represents the transmission delay of the Ini control packet. ACK-pkt This indicates the transmission delay of the ACK confirmation packet.

[0097] S5, the unmanned underwater vehicle will wait for a period of time after sending the Ini control packet. To receive ACK packets from underwater nodes;

[0098] Waiting delay set after the unmanned underwater vehicle broadcasts the Ini control packet The calculation formula is:

[0099]

[0100] In one embodiment, τ = 1.25s represents the maximum propagation delay from the underwater node to the unmanned underwater vehicle, T Ini-pkt =0.038s represents the transmission delay of the Ini control packet, T ACK-pkt =0.008s indicates the transmission delay of the ACK confirmation packet.

[0101] S6, such as Figure 2 As shown, after receiving the Ini control packet, the underwater node sets the access policy according to the information in the Ini control packet and waits for a certain delay. Then send an ACK confirmation packet to the unmanned underwater vehicle;

[0102] After receiving the initial control packet, the underwater node will wait for a certain time delay before sending back a confirmation control packet. The following conditions must be met:

[0103]

[0104] Among them, T Ini-pkt This indicates the transmission delay of the Ini control packet.

[0105] In one embodiment, let have

[0106] S7, waiting for delay Afterwards, the unmanned underwater vehicle will check whether it has received ACK confirmation packets from the three underwater nodes, such as... Figure 2As shown, when fewer than 3 ACK confirmation packets are received, the unmanned underwater vehicle will update the initial access timestamp T0 in the Ini control packet to obtain a new Ini control packet, and broadcast the new Ini control packet to the underwater node to restart the initialization phase. When 3 ACK confirmation packets are received, the data acquisition task enters the data collection phase, and the unmanned underwater vehicle waits to receive data packets sent by the underwater node.

[0107] In one embodiment, the time T when the underwater cruiser first begins broadcasting the Ini control packet c =0s, let T0 = 5s.

[0108] S8. During the data collection phase, the underwater node starts from time T0 and collects data every T interval... slot Send a data packet of size B;

[0109] The formula for calculating the transmission time of the k-th time slot of an underwater node is:

[0110]

[0111] in, It is a set of positive integers.

[0112] In one embodiment, the network simulator NS-3 is used to perform 1000 simulations of the scenario described in this example. Let the coordinates of non-friendly nodes be (x... e ,y e ,z e In 1000 simulations, coordinate values ​​of nodes other than our own were randomly selected, with the following selection range:

[0113] x e ∈[750,2250],y e ∈[-750,750],z e ∈[0,1000]

[0114] The spatial relationship between underwater nodes and unmanned underwater vehicles is as follows: Figure 3 As shown.

[0115] Figure 4 The average number of data packets sent by the sending node, the average number of data packets successfully received by the receiving node, and the average number of data packets successfully received by non-friendly nodes are given in 1000 simulations.

[0116] 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. The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the scope of protection of the present invention.

Claims

1. A slotted MAC method for restricted access to underwater acoustic networks by non-self nodes, characterized in that, Includes the following steps: S1, Deployment of Observation Water Area Each underwater node is responsible for collecting underwater data. The collected data is first stored in the local cache of the underwater node, and the unmanned underwater vehicle periodically goes to the observation area to collect data through underwater acoustic communication. Data cached by each underwater node; All underwater nodes are deployed in a chain at equal intervals at the same depth. Assume the three-dimensional coordinates of two adjacent underwater nodes are represented as follows: , It should meet the following conditions: in Indicates the depth of sensor node deployment. This represents the distance difference between two adjacent underwater nodes; Assume the three-dimensional coordinates of the underwater node at one end of the linear underwater node chain are represented as follows: Then the three-dimensional coordinates of the underwater node at the other end are: ; S2. Each underwater node sends data to the unmanned underwater vehicle (UUV) via time-slot access. The UUV sets the size of the data packets sent by each underwater node for this data acquisition mission according to its requirements. Time slot length To ensure that data packets are only stored in the location set The position in the data packet is used to achieve receive alignment; the formula for calculating the data packet size is as follows: in, The unit is bytes. This indicates the speed at which sound waves travel in water. This indicates the transmission rate of the underwater acoustic communication device, measured in bits per second. (Parameter) Based on the requirement of underwater nodes to restrict access from non-friendly nodes and the location set of unmanned underwater vehicles The tradeoff value for the number of elements in the middle is either 0 or 1; when At that time, non-friendly nodes can receive fewer data packets without collision, but provide the unmanned underwater vehicle with a set of location data. The number of elements in the middle is 2; when At that time, location set The number of elements in the middle is 4; The formula for calculating the time slot length is as follows: in, Indicates the transmission rate of the underwater acoustic communication device; S3, Unmanned underwater vehicles randomly select from a given set of locations. Choose a location as the receiving location for this data collection task to protect your own location information; S4. After the unmanned underwater vehicle reaches the selected receiving position, it broadcasts an Ini control packet to the underwater node, and the data acquisition task enters the initialization phase. The Ini control packet carries the initial access timestamp. and time slot length ; S5, the unmanned underwater vehicle will wait for a period of time after sending the Ini control packet. To receive ACK packets from underwater nodes; S6. After receiving the Ini control packet, the underwater node sets the access policy according to the information in the Ini control packet and waits for a period of time. Then send an ACK confirmation packet to the unmanned underwater vehicle; S7, waiting for delay Afterwards, the unmanned underwater vehicle will check whether it has received a signal from... The number of ACK acknowledgment packets received by the underwater nodes is less than [number missing]. The unmanned underwater vehicle will update the initial access timestamp in the Ini control package. The new Ini control packet is received and broadcast to the underwater node to restart the initialization phase. Upon confirmation of receipt... With the arrival of an ACK confirmation packet, the data acquisition task enters the data collection phase, and the unmanned underwater vehicle waits to receive data packets sent by the underwater node. S8. During the data collection phase, the underwater node automatically... Time starts every interval Send a size of Data packets.

2. The time-slot MAC method for restricted access to underwater acoustic networks by non-self nodes according to claim 1, characterized in that, In step S5, the unmanned underwater vehicle sets a waiting delay after broadcasting the Ini control packet. The calculation formula is: in, This represents the maximum propagation delay from the underwater node to the unmanned underwater vehicle. This indicates the transmission delay of the Ini control packet. This indicates the transmission delay of the ACK confirmation packet.

3. The time-slot MAC method for restricted access to underwater acoustic networks by non-self nodes according to claim 1, characterized in that, In step S6, after receiving the initial control packet, the underwater node will wait for a certain time delay before sending back a confirmation control packet. The following conditions must be met: in, This indicates the transmission delay of the Ini control packet.

4. The time-slot MAC method for restricted access to underwater acoustic networks by non-self nodes according to claim 1, characterized in that, In step S4, the initial access timestamp The following conditions must be met: in, This indicates the time when the unmanned underwater vehicle broadcasts the current Ini control packet. This represents the maximum propagation delay from the underwater node to the unmanned underwater vehicle. This indicates the transmission delay of the Ini control packet. This indicates the transmission delay of the ACK confirmation packet.

5. The time-slot MAC method for restricted access to underwater acoustic networks by non-self nodes according to claim 1, characterized in that, In step S8, the underwater node's first The formula for calculating the transmission time of each time slot is: in, It is a set of positive integers.

6. The time-slot MAC method for restricted access to underwater acoustic networks by non-self nodes according to claim 1, characterized in that, In step S3, when At that time, location set The calculation formula is: when At that time, location set The calculation formula is: when At that time, location set The calculation formula is: when At that time, location set The calculation formula is: in, This represents the distance difference between two adjacent underwater nodes.

7. The time-slot MAC method for restricted access to underwater acoustic networks by non-self nodes according to claim 1, characterized in that, Unmanned underwater vehicles should have the ability to self-locate underwater and perceive their surroundings.

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