Hybrid task underwater acoustic network MAC (Media Access Control) method for efficiently responding burst data

Abstract

The invention discloses a hybrid task underwater acoustic network MAC (Media Access Control) method for efficiently responding burst data. According to the method, the sending time of each node in a common transmission period is reasonably arranged, so that interference data of the nodes can arrive at the same time as much as possible, namely, interference aggregation is realized, and the nodes have more idle time. When the node detects an emergency, notification packets are sent twice, so that all sensing nodes can be ensured to be effectively notified and enter a silent state so as to give way to a channel. Meanwhile, when the protocol is used for dealing with burst data communication, channel resources are not reserved in advance, so that the communication efficiency is higher. Based on the idea of interference aggregation, fast response and priority transmission of burst data are ensured while high throughput in a common transmission stage is realized.

Description

Technical Field

[0001] The present invention belongs to the field of underwater acoustic sensor networks, and relates to a MAC method for underwater acoustic networks with efficient response to burst data in a hybrid task scenario. Technical Background

[0002] With the increasing growth of ocean-oriented scientific research and commercial demands, a large number of underwater offshore deployed sensor nodes need to perform long-term sensing and monitoring tasks. In a hybrid task underwater acoustic sensor network, nodes not only perform sensing tasks to collect ordinary data, but also perform detection tasks. Once a detected target is found, burst data needs to be reported to the central node. During the data collection process, multiple underwater nodes need to share access to the underwater acoustic wireless channel, and Medium Access Control (MAC) plays a crucial role in reducing collisions and improving throughput.

[0003] The main characteristic of underwater acoustic MAC is the existence of spatio-temporal coupling characteristics. That is, since the underwater acoustic propagation speed is five orders of magnitude slower than that of radio waves, the arrival time of a data packet is jointly determined by the transmission time and the spatial position between the transmitter and the receiver. In contrast, in radio communication, the time for a data packet to reach the receiver can be approximated as its transmission time. The spatio-temporal coupling characteristics make most MAC protocols in radio networks inapplicable to underwater acoustic networks, and it is necessary to develop underwater acoustic MAC protocols in combination with spatio-temporal coupling characteristics.

[0004] Existing underwater acoustic MAC protocols have made a lot of research on how to utilize spatio-temporal coupling characteristics to improve the throughput of underwater acoustic MAC. However, few studies have focused on how to achieve efficient transmission of ordinary data and preferential transmission of burst data in the scenario of a hybrid task sensor network. Existing underwater acoustic MAC protocols related to emergency response achieve preferential transmission of burst data by pre-reserving certain time or frequency band and other channel resources in advance. However, when emergencies do not occur, it will cause waste of resources, and due to the relatively limited channel resources of underwater acoustic communication, the above approach greatly reduces the communication efficiency of underwater sensor networks.

[0005] In "A TDMA-based MAC Protocol for Underwater Acoustic Sensor Networks", a MAC protocol for underwater acoustic sensor networks based on time slot division is proposed. This protocol can effectively improve the time slot utilization rate, but it is not applicable to scenarios with burst data; "An Implementation Method of Hybrid Task Underwater Acoustic MAC Protocol for Data Collection" discloses an implementation method of a hybrid task underwater acoustic MAC protocol for data collection, which switches the execution task type of nodes according to different network loads and can meet the real-time requirements of burst-type task data packets, but it is not applicable to long-distance underwater acoustic communication scenarios. Summary of the Invention

[0006] The purpose of the present invention is to fill the gaps in the existing technology and provide a MAC method for underwater acoustic networks with efficient response to burst data in a hybrid task scenario.

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

[0008] A MAC method for an underwater acoustic network with efficient response to burst data for hybrid tasks, comprising the following steps:

[0009] S1. Deploy N underwater sensor nodes and a central node in the observation water area to form an underwater acoustic network. The central node is responsible for collecting the data transmitted by the underwater sensor nodes. The underwater sensor nodes detect the detected targets in real time while collecting environmental data. When the underwater sensor nodes collect environmental data, they enter the normal transmission stage and generate normal data packets. When a detected target is detected, they enter the burst transmission stage and generate burst data packets.

[0010] S2. After the underwater acoustic network is deployed, perform initialization. The central node broadcasts an Ini frame with the sending time to all underwater sensor nodes. The underwater sensor nodes send Ini-ack frames as replies. Repeat this process until the central node receives all the Ini-ack frames of the underwater sensor nodes. After initialization, the central node broadcasts a Beacon beacon frame including type, source address, destination address, the sending time schedule [t1, t2,..., t i ,…,t n , the scheduling frame length T F and the start time T0 information to each underwater sensor node.

[0011] S3. In the normal transmission stage, the underwater sensor nodes periodically send normal data packets to the central node according to the start time T0, the sending time schedule [t1, t2,..., t i ,…,t n and the scheduling frame length T F received in the initialization, so that the data packets do not collide at the central node.

[0012] S4. When the i-th underwater sensor node detects a detected target, the underwater sensor node enters the burst transmission stage. The underwater sensor node i first broadcasts and sends a first notification packet Info1 to other underwater sensor nodes. After a retransmission delay T rt , the i-th underwater sensor node broadcasts and sends a second notification packet Info2 to other underwater sensor nodes. After the i-th underwater sensor node sends the second notification packet Info2, it waits for T wi time and then starts to send burst data to the central node.

[0013] S5. After receiving the first notification packet Info1 or the second notification packet Info2, other underwater sensor nodes immediately stop the normal transmission mode and enter the silent state, waiting for a restart notification packet to re-enter the normal transmission stage.

[0014] S6. After the burst data transmission is completed, the i-th underwater sensor node sends a restart notification packet Info-re with the start time T of the normal transmission phase to other underwater sensor nodes; rsi

[0015] S7. Each underwater sensor node periodically sends normal data packets to the central node again according to the start time T of the normal transmission phase in the restart notification packet Info-re rsi and the allocated initialization time t. i

[0016] Furthermore, in step S1, all underwater sensor nodes are deployed equidistantly in a linear chain at the same depth, forming a linear sensor node chain;

[0017] For the three-dimensional coordinates (x1, y1, z d ) and (x2, y2, z d ) of two adjacent underwater sensor nodes, the following conditions need to be met:

[0018] |x1 - x2| = l;

[0019] y1 - y2 = 0;

[0020] where z d represents the depth at which the underwater sensor nodes are deployed, and l represents the distance difference between two adjacent underwater sensor nodes;

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

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

[0023] The central node is located near the midline of the linear sensor node chain where the underwater sensor nodes are located and at a relatively far distance. Its three-dimensional coordinates are:

[0024]

[0025] where β is the distance deviating from the midline of the linear sensor node chain, and D b is the distance between the central node and the linear sensor node chain. Both are determined by the actual situation. β is usually several hundred meters to several kilometers, and in a long-distance underwater acoustic communication network, D b is dozens of kilometers.

[0026] ​​Further, in step S1, the detected target refers to targets such as white dolphins and submersibles that can be detected by passive or active acoustic detection means.

[0027] Further, in step S2, the starting time T0 should ensure that the farthest sensing node receives the Beacon beacon frame, that is, T0 should satisfy:

[0028]

[0029] where t now is the time for the central node to send the Beacon beacon frame, the starting time T0 is the time for the underwater sensing node to start the normal transmission stage, D i is the distance between the i-th underwater sensing node and the central node, v is the underwater acoustic wave velocity, and t bc is the transmission delay of the Beacon beacon frame.

[0030] Further, in step S2, the transmission schedule [t1, t2, …, t i , …, t n in which t i represents the transmission time of the underwater sensing node i, and the transmission schedule and the scheduling frame length T F are determined by the following multi-objective optimization model:

[0031]

[0032] where aims to maximize the throughput of the network, aims to minimize the maximum interference degree of the underwater sensing nodes, Th is the throughput of the network, and the calculation formula is:

[0033]

[0034] where D i is the distance between the i-th underwater sensing node and the central node, v is the underwater acoustic wave velocity; t p is the transmission delay of the ordinary data packet, T F is the length of the scheduling frame, t g is the protection interval between two adjacent ordinary data packets; IR i represents the interference degree of the i-th underwater sensing node, and IR iThe calculation method of IR is the ratio of the duration from the start of the first interfering data packet to the end of the last interfering data packet to the length of the scheduling frame. The first interfering data packet refers to the first ordinary data packet received by the i-th underwater sensor node from other underwater sensor nodes after the start of a scheduling frame, and the last interfering data packet refers to the last ordinary data packet received by the underwater sensor node i from other underwater sensor nodes within the same scheduling frame. Then IR i is:

[0035]

[0036] where d ij is the distance between the i-th underwater sensor node and the j-th underwater sensor node, and the optimization variables of the multi-objective optimization model

[0037] Furthermore, in step S3, after the i-th underwater sensor node receives the Beacon beacon frame, it sets the sending time of the first data packet in the ordinary transmission phase to T0 + t i , and the subsequent periodic sending moments are T0 + t i + kT F , where k belongs to the set of positive integers.

[0038] Furthermore, in step S3, the retransmission delay T rt is calculated as follows:

[0039]

[0040] The sending interval between the first notification packet Info1 and the second notification packet Info2 should be set to the maximum interference time among all underwater sensor nodes. When the underwater sensor nodes perform periodic data transmission following the scheduling in step S3, the interference time of each underwater sensor node is continuous and within a set range. Therefore, it can be proved that when the underwater sensor node that detects an emergency event sends the first notification packet Info1 and the second notification packet Info2 at this interval, at least one notification packet can be accurately received by other underwater sensor nodes.

[0041] Furthermore, in step S3, after the i-th underwater sensor node sends the second notification packet Info2, it must wait for a set time T wi to ensure that the remaining underwater sensor nodes farthest from the underwater sensor node i receive the second notification packet Info2;

[0042] Therefore, for the i-th underwater sensor node that detects the detected target, the waiting time T wi should satisfy:

[0043]

[0044] Among them, t in is the transmission delay of the first notification packet Info1 and the second notification packet Info2.

[0045] Furthermore, in step S6, after the i-th underwater sensor node completes the burst data transmission, it should notify other sensor nodes to re-enter the normal transmission stage, and the start time T of the normal transmission stage rsi should satisfy:

[0046]

[0047] Among them, t in-re is the transmission delay of the restart notification packet Info-re.

[0048] Furthermore, in step S7, the moment when the i-th underwater sensor node sends the first data packet after re-entering the normal transmission stage is T rs +t i , and the subsequent periodic sending moments are T rs +t i +kT F , where k belongs to the set of positive integers.

[0049] Furthermore, N underwater sensor nodes and a central node complete time synchronization during the initialization process.

[0050] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0051] In the present invention, by reasonably arranging the sending time of each node within the normal transmission period, the interference data of the nodes can arrive as simultaneously as possible, that is, interference aggregation is achieved, so that the nodes have more idle time. When a node detects an emergency and sends two notification packets, it can ensure that all sensor nodes are effectively notified and enter the silent state to vacate the channel. At the same time, the protocol in the present invention does not adopt early reservation of channel resources when dealing with burst data communication, so the communication efficiency is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a flowchart of a hybrid task underwater acoustic network MAC method for efficient response to burst data in an embodiment of the present invention.

[0053] Figure 2 is the communication frame structure diagram in an embodiment of the present invention.

[0054] Figure 3 is a schematic diagram of the sending and receiving of data packets in different transmission stages in an embodiment of the present invention.

[0055] Figure 4 This is a schematic diagram of the performance results under 5000s simulation using the NS-3 network emulator in the embodiments of the present invention. Detailed implementation manners

[0056] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. However, the scope of protection required by the present invention is not limited to the scope expressed in the embodiments.

[0057] In one embodiment, a MAC method for a hybrid task underwater acoustic network with efficient response to burst data is as Figure 1 shown, and includes the following steps:

[0058] S1. Deploy N = 5 underwater sensing nodes and a central node in the observation water area to form an underwater acoustic network. The central node is responsible for collecting the data transmitted by the underwater sensing nodes. The underwater sensing nodes detect the detected targets in real time while collecting environmental data. When the underwater sensing nodes collect environmental data, they enter the normal transmission stage and generate normal data packets. When they detect the detected targets, they enter the burst transmission stage and generate burst data packets;

[0059] In one embodiment, all underwater sensing nodes are deployed equidistantly at a depth of 500m in a chain at intervals of 9000m to form a linear sensing node chain;

[0060] For the three-dimensional coordinates (x1, y1, z d ) and (x2, y2, z d ) of two adjacent underwater sensing nodes, the following conditions need to be satisfied:

[0061] |x1 - x2| = l;

[0062] y1 - y2 = 0;

[0063] In one embodiment, z d = 500m represents the deployment depth of the underwater sensing nodes, and l = 9000m represents the distance difference between two adjacent underwater sensing nodes;

[0064] Assume that the three-dimensional coordinates of an underwater sensing node at one end of the linear sensing node chain are represented as (x0, y0, z d ), then the three-dimensional coordinates of the underwater sensing node at the other end of the linear sensing node chain are:

[0065] (x0 + (N - 1)l, y0, z d );

[0066] The central node is located near the midline of the linear sensing node chain where the underwater sensing nodes are located and at a relatively far distance. Its three-dimensional coordinates are:

[0067]

[0068] Among them, β is the distance deviating from the midline of the linear sensing node chain, and D b is the distance from the central node to the linear sensing node chain, both of which are determined by the actual situation. β is usually several hundred meters to several kilometers, and D b is dozens of kilometers in the long-distance underwater acoustic communication network.

[0069] In one embodiment, the three-dimensional coordinates of the sensing node at one end of the linear sensing node chain are (0, 0, 500), then the three-dimensional coordinates of the sensing node at the other end are (36000, 0, 500).

[0070] In one embodiment, the central node is located near the midline of the straight line where the sensing nodes are located and 50 km away from the straight line, and its three-dimensional coordinates are:

[0071] (19700, 50000, 500).

[0072] The detected target refers to targets such as white dolphins and submersibles that can be detected by passive or active acoustic detection means.

[0073] S2. After the underwater acoustic network is deployed, initialize. The central node broadcasts the Ini frame with the sending time to all underwater sensing nodes, and the underwater sensing nodes send the Ini-ack frame as a reply. Repeat this process until the central node receives all the Ini-ack frames of the underwater sensing nodes. After initialization, the central node broadcasts the Beacon beacon frame including type, source address, destination address, the sending time schedule [t1, t2,..., t i ,..., t n , scheduling frame length T F and the starting time T0 information to each underwater sensing node;

[0074] In one embodiment, the communication frame structure diagram is as Figure 2 shown.

[0075] In one embodiment, N underwater sensing nodes and a central node complete time synchronization during the initialization process.

[0076] The starting time T0 should ensure that the farthest sensing node receives the Beacon beacon frame, that is, T0 should satisfy:

[0077]

[0078] In one embodiment, t now is the time when the central node sends the Beacon beacon frame, and t now= 0, the starting time T0 is the time when the underwater sensor node starts the normal transmission phase, D i is the distance between the i-th underwater sensor node and the central node, v is the underwater acoustic wave velocity, t bc is the transmission delay of the Beacon beacon frame.

[0079] In one embodiment, the length of the Beacon beacon frame is 32 bytes, and the transmission rate of the sensor node is 2 kbps, then the transmission delay of the Beacon beacon frame In one embodiment, the underwater acoustic wave velocity v = 1500 m / s, then T0 can be taken as 35.955 s.

[0080] The transmission schedule [t1, t2, …, t i , …, t n The t in i represents the transmission time of the i-th underwater sensor node. The transmission schedule and the scheduling frame length T F are determined by the following multi-objective optimization model:

[0081]

[0082] Among them, The purpose of is to maximize the throughput of the network, The purpose of is to minimize the maximum interference degree of the underwater sensor node. Th is the throughput of the network, and the calculation formula is:

[0083]

[0084] Among them, D i is the distance between the i-th underwater sensor node and the central node, v is the underwater acoustic wave velocity; t g = 0.02 s is the transmission delay of the ordinary data packet, T F is the length of the scheduling frame, t g is the protection interval between two adjacent ordinary data packets; IR i represents the interference degree of the i-th underwater sensor node. IR i The calculation method of is the ratio of the duration from the start of the first interfering data packet to the end of the last interfering data packet to the length of the scheduling frame. The first interfering data packet refers to the first ordinary data packet received by the i-th underwater sensor node from other underwater sensor nodes after the start of a scheduling frame. The last interfering data packet refers to the last ordinary data packet received by the underwater sensor node i from other underwater sensor nodes within the same scheduling frame. Then IR i is:

[0085]

[0086] where d ij is the distance between the i-th underwater sensing node and the j-th underwater sensing node, and the optimization variables of the multi-objective optimization model

[0087] In one embodiment, after solving the model,

[0088] S3. In the normal transmission stage, the underwater sensing nodes send normal data packets to the central node periodically according to the starting time T0, the transmission schedule [t1, t2, …, t i , …, t n , …, t F and the scheduling frame length T received in the initialization Beacon beacon frame, so that the data packets do not collide at the central node;

[0089] In one embodiment, the calculation method of the retransmission delay T rt is as follows:

[0090]

[0091] The sending interval between the first notification packet Info1 and the second notification packet Info2 should be set to the maximum interference time among all underwater sensing nodes. When the underwater sensing nodes send data periodically following the schedule in step S3, the interference time of each underwater sensing node is continuous and within the set range. Therefore, it can be proved that when the underwater sensing node detecting the emergency event sends the first notification packet Info1 and the second notification packet Info2 at this interval, at least one notification packet can be accurately received by other underwater sensing nodes.

[0092] In one embodiment, T rt = 1.3605 s.

[0093] After the i-th underwater sensing node sends the second notification packet Info2, it must wait for the set time T wi to ensure that the remaining underwater sensing nodes farthest from the underwater sensing node i receive the second notification packet Info2;

[0094] Therefore, for the i-th underwater sensing node detecting the detected target, the waiting time T wi should satisfy:

[0095]

[0096] where t in is the transmission delay of the first notification packet Info1 and the second notification packet Info2.

[0097] In one embodiment, the sizes of the first notification packet Info1 and the second notification packet Info2 are both 6 bytes, and the transmission delay t in = 0.024 s. For nodes 1 and 5, T w1 = T w5 = 24.024 s. For nodes 2 and 4, T w2 = T w4 = 18.024 s. For node 3, T w3 = 12.024 s.

[0098] S4. When the i-th underwater sensing node detects the detected target, the underwater sensing node enters the burst transmission stage. The underwater sensing node i first broadcasts and sends the first notification packet Info1 to other underwater sensing nodes; after the retransmission delay T rt of the i-th underwater sensing node, it broadcasts and sends the second notification packet Info2 to other underwater sensing nodes. After sending the second notification packet Info2, the i-th underwater sensing node waits for T wi time and then starts to send burst data to the central node;

[0099] S5. After receiving the first notification packet Info1 or the second notification packet Info2, other underwater sensing nodes immediately stop the normal transmission mode and enter the silent state, waiting for the restart notification packet to re-enter the normal transmission stage;

[0100] S6. After the burst data is sent, the i-th underwater sensing node sends a restart notification packet Info-re with the start time T rsi of the normal transmission stage to other underwater sensing nodes;

[0101] After the i-th underwater sensing node completes the burst data transmission, it should notify other sensing nodes to re-enter the normal transmission stage. The start time T rsi of the normal transmission stage should satisfy:

[0102]

[0103] where t in-re is the transmission delay of the restart notification packet Info-re.

[0104] In one embodiment, the size of the restart notification packet Info-re is 6 bytes, and the transmission delay t in-re = 0.024 s. For nodes 1 and 5, T rs1 = T rs5 = t now + 24.024 s. For nodes 2 and 4, T rs2 = T rs4 = t now+18.024 s, for node 3, T rs3 = t now +12.024 s.

[0105] S7. Each underwater sensing node, according to the start time T of the normal transmission phase in the restart notification packet Info-re rsi and the initialized assigned time t i periodically sends normal data packets to the central node again;

[0106] The time when the i-th underwater sensing node sends the first data packet after re-entering the normal transmission phase is T rs + t i , and the subsequent periodic sending time is T rs + t i + kT F , where k belongs to the set of positive integers.

[0107] In one embodiment, the sending and receiving of data packets in the normal transmission phase and the burst transmission phase are as Figure 3 shown.

[0108] In one embodiment, the network emulator NS-3 is used to simulate the scenario described in this example. The detected target moves near the underwater sensor network at a speed of 10 m / s. The detection distance of the underwater sensor node is 5 km, that is, when the target enters the spherical space centered on the sensor node with a radius of 5 km, the underwater sensor node detects the detected target. Figure 4 The normalized throughput of the network in the normal transmission phase and the average burst data access delay after detecting an emergency are given after 5000 s of simulation in the NS-3 emulator.

[0109] Those of ordinary skill in the art will realize that the embodiments described herein are to assist the reader in understanding the principles of the present invention, and it should be understood that the protection scope of the invention is not limited to such specific statements and embodiments. The above embodiments are preferred implementation schemes of the present invention, but the implementation schemes of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A MAC method for an underwater acoustic network with hybrid tasks for efficient response to burst data, characterized in that, It includes the following steps: S1. Deploy N underwater sensing nodes and a central node in the observed water area to form an underwater acoustic network. The central node is responsible for collecting the data transmitted by the underwater sensing nodes. The underwater sensing nodes detect the target to be detected in real time while collecting environmental data. When the underwater sensing nodes collect environmental data, they enter the normal transmission phase and generate normal data packets. When they detect the target to be detected, they enter the burst transmission phase and generate burst data packets. S2. After the underwater acoustic network is deployed, perform initialization. The central node broadcasts an Ini frame with the sending time to all underwater sensor nodes. The underwater sensor nodes send Ini-ack frames as responses. Repeat this process until the central node receives all the Ini-ack frames from the underwater sensor nodes. After initialization, the central node broadcasts a Beacon beacon frame to each underwater sensor node, including information such as type, source address, destination address, the sending time schedule [t1, t2, …, t i , …, t n , the scheduling frame length T F and the start time T0 information; S3. In the normal transmission stage, the underwater sensing nodes send ordinary data packets to the central node periodically according to the starting time T0, the transmission schedule [t1, t2, …, t i , …, t n , and the scheduling frame length T F received in the initialization, so that the data packets do not collide at the central node; S4. When the i-th underwater sensing node detects the target to be detected, the underwater sensing node enters the burst transmission stage. The underwater sensing node i first broadcasts and sends the first notification packet Info1 to other underwater sensing nodes; after the retransmission delay T of the i-th underwater sensing node rt it broadcasts and sends the second notification packet Info2 to other underwater sensing nodes. After the i-th underwater sensing node sends the second notification packet Info2, it waits for T wi time and then starts to send burst data to the central node; S5. After receiving the first notification packet Info1 or the second notification packet Info2, other underwater sensing nodes immediately stop the normal transmission mode and enter the silent state, waiting for the restart notification packet to re-enter the normal transmission phase. S6. After the burst data transmission is completed, the i-th underwater sensor node sends a restart notification packet Info-re with the start time T of the normal transmission phase to other underwater sensor nodes rsi to other underwater sensor nodes; S7, each underwater sensor node restarts according to the normal transmission phase start time T in the notification packet Info-re rsi and the time t at which the allocation is initialized i Resend normal data packets to the central node periodically.

2. The hybrid task underwater acoustic network MAC method for efficient response to burst data according to claim 1, wherein, In step S1, all underwater sensing nodes are deployed in a chain at equal intervals in a straight line at the same depth to form a linear sensing node chain. For the three-dimensional coordinates (x1, y1, z d ) and (x2, y2, z d ) of two adjacent underwater sensing nodes, the following conditions need to be satisfied: |x1 - x2| = l; y1 - y2 = 0; Among them, z d represents the depth at which the underwater sensing nodes are deployed, and l represents the distance difference between two adjacent underwater sensing nodes; Suppose the three-dimensional coordinates of the underwater sensing node at one end of the linear sensing node chain are represented as (x0, y0, z d ), then the three-dimensional coordinates of the underwater sensing node at the other end of the linear sensing node chain are: (x0+(N-1)l,y0,z d ); The central node is located near the midline of the linear sensing node chain where the underwater sensing nodes are located and at a relatively far distance. Its three-dimensional coordinates are: Among them, β is the distance deviating from the midline of the linear sensor node chain, and D b is the distance from the central node to the linear sensor node chain. Both are determined by the actual situation. β is usually several hundred meters to several kilometers. In a long-distance underwater acoustic communication network, D b is dozens of kilometers.

3. The MAC method for an underwater acoustic network with hybrid tasks for efficient response to burst data according to claim 1, wherein, In step S2, the starting time T0 should ensure that the farthest sensing node receives the Beacon beacon frame, that is, T0 should satisfy: where t now is the time for the central node to send a Beacon beacon frame, and the starting time T0 is the time when the underwater sensor node starts the normal transmission phase. D i is the distance between the i-th underwater sensor node and the central node, v is the underwater acoustic wave velocity, and t bc is the transmission delay of the Beacon beacon frame.

4. A MAC method for an underwater acoustic network with hybrid tasks for efficient response to burst data according to claim 1, characterized in that, In step S2, the transmission schedule [t1, t2, …, t i , …, t n where t i represents the transmission time of the underwater sensing node i. The transmission schedule and the scheduling frame length T F are determined by the following multi-objective optimization model: Among them, the purpose is to obtain the maximum throughput of the network, the purpose is to minimize the maximum degree of interference suffered by underwater sensor nodes. Th is the throughput of the network, and the calculation formula is: Among them, D i is the distance between the i-th underwater sensing node and the central node, v is the underwater acoustic wave velocity; t p is the transmission delay of the ordinary data packet, T F is the length of the scheduling frame, t g is the guard interval between two adjacent ordinary data packets; IR i represents the degree of interference of the i-th underwater sensing node, and the calculation method of IR i is the ratio of the duration from the start of the first interfering data packet to the end of the last interfering data packet to the length of the scheduling frame. The first interfering data packet refers to the first ordinary data packet received by the i-th underwater sensing node from other underwater sensing nodes after the start of a scheduling frame, and the last interfering data packet refers to the last ordinary data packet received by the underwater sensing node i from other underwater sensing nodes within the same scheduling frame. Then IR i is: where d ij is the distance between the i-th and j-th underwater sensor nodes, and the optimization variables of the multi-objective optimization model 5. The MAC method for an underwater acoustic network with hybrid tasks for efficient response to burst data according to claim 1, characterized in that, In step S3, after the i-th underwater sensing node receives the Beacon beacon frame, it sets the transmission time of the first data packet in the normal transmission phase to T0 + t i , and the subsequent periodic transmission times are where is a set of positive integers.

6. The MAC method for an underwater acoustic network with hybrid tasks for efficient response to burst data according to claim 1, wherein In step S3, the retransmission delay T rt is calculated as follows: The sending interval between the first notification packet Info1 and the second notification packet Info2 should be set as the maximum interference time among all underwater sensing nodes. When the underwater sensing nodes send data periodically following the scheduling in step S3, the interference time of each underwater sensing node is continuous and within the set range. Therefore, it can be proved that when the underwater sensing node that detects the emergency sends the first notification packet Info1 and the second notification packet Info2 at this interval, at least one notification packet can be accurately received by other underwater sensing nodes.

7. A MAC method for an underwater acoustic network with hybrid tasks for efficient response to burst data according to claim 1, characterized in that, In step S3, after the i-th underwater sensing node sends the second notification packet Info2, it must wait for a set time T wi , to ensure that the remaining underwater sensing nodes farthest from the underwater sensing node i receive the second notification packet Info2; Therefore, for the i-th underwater sensing node that detects the detected target, the waiting time T wi should satisfy: where t in is the transmission delay of the first notification packet Info1 and the second notification packet Info2.

8. A MAC method for an underwater acoustic network with hybrid tasks for efficient response to burst data according to claim 1, characterized in that In step S6, after the i-th underwater sensing node completes the burst data transmission, it should notify other sensing nodes to re-enter the normal transmission phase, and the start time T of the normal transmission phase rsi should satisfy: Among them, t in-re is the transmission delay of the restart notification packet Info-re.

9. The MAC method for an underwater acoustic network with hybrid tasks for efficient response to burst data according to claim 1, characterized in that, In step S7, the moment when the i-th underwater sensing node sends the first data packet after re-entering the normal transmission phase is T rs +t i , and the moments of subsequent periodic transmissions are where is a set of positive integers.

10. A MAC method for an underwater acoustic network with hybrid tasks for efficient response to burst data according to claim 1, characterized in that, The N underwater sensing nodes and a central node complete time synchronization during the initialization process.

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