A method for implementing a dynamic MAC protocol based on reception alignment

Abstract

The application discloses a kind of based on receiving alignment dynamic MAC protocol implementation method.Compared with land wireless network protocol, underwater acoustic network protocol needs to consider space-time uncertainty.The existing receiving alignment idea proposes to arrange node sending time from the quantitative point of view, to realize high channel utilization, low data collision rate.But this idea has not been put into network protocol, and the low-load scene, dynamic scene and high error code characteristics of underwater acoustic channel are not considered.Aiming at the above problems, the application optimizes the data transmission efficiency in the low-load scene by increasing control information.Through the design of the initialization phase, network nodes can obtain the global information required for operation, and through the design of the restart phase, the protocol can run stably in multiple dynamic scenarios such as node exit or join, node failure or recovery.Aiming at the high error code characteristics in underwater acoustic channel, the protocol increases the Ack feedback mechanism, improves the transmission success rate of the protocol through timeout retransmission and fast retransmission.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of underwater acoustic communication technology, and particularly relates to a dynamic MAC protocol implementation method based on receiving alignment. BACKGROUND

[0002] The research on underwater acoustic communication network has broad application prospect and practical significance, and has been a research hotspot for more than ten years. Among them, the MAC protocol belonging to the data link layer determines the way of multiple nodes accessing the shared channel in the network, which plays an important role in reducing the propagation delay between nodes, improving network throughput, improving the success probability of data packet transmission, and maintaining the fairness of network nodes accessing the shared channel. The long and dynamic propagation delay of underwater acoustic communication, limited bandwidth, low data rate, limited energy, and node mobility make it very difficult for underwater nodes to coordinate with each other. It is necessary to design a reliable and effective MAC protocol suitable for underwater acoustic networks, which plays a crucial role in the overall network performance.

[0003] At present, the MAC protocol of underwater acoustic network mainly has two research branches: one is based on the evolution of RWN (radio wireless network), and the other is a newly designed MAC protocol for the characteristics of underwater acoustic network. The former can be further divided into multiplexing and non-multiplexing types. Common TDMA, CDMA, FDMA types belong to multiplexing, while Aloha, CSMA, MACA, FAMA and other types of protocols belong to non-multiplexing. The above types of protocols are evolved from RWN, although different improvements are made for different characteristics of underwater acoustic network, but the effect is far from ideal in RWN. Therefore, many scholars have begun to study network protocols that are more suitable for underwater acoustic channels. Some scholars have proposed that for the characteristics of underwater acoustic channels, more accurate transmission plans are needed, and scheduling type protocols have emerged. Scheduling type protocols take advantage of the long propagation delay characteristics, shared channel characteristics, etc. in underwater acoustic channels to solve the problems of information collection, scheduling constraint calculation, energy efficiency, etc. in the network. In addition, some people have proposed reservation type protocols, which can reserve medium access opportunities, effectively eliminate reception conflicts, and improve energy utilization efficiency. In addition, network protocols based on cross-layer design idea are also considered by scholars, and cross-layer design can use the technology of other layers to help solve the problems of MAC protocol. In the physical layer, MIMO, OFDM, power control, spectrum sensing and other technologies are used to design adaptive MAC protocols. It can also be combined with routing layer protocols to design a communication system with less redundant transmission and higher overall efficiency. In addition, traffic control technology in the transport layer can also be moved to the MAC layer to improve network performance. SUMMARY

[0004] The application aims to optimize the sending strategy in the low load scene in the receiving alignment thought, to cope with different network dynamic scenes, more flexible and reasonable, better applicable to the underwater acoustic channel, and proposes an implementation method of a dynamic MAC protocol based on receiving alignment. The method has better network performance in the low load scene, can cope with multiple dynamic scenes such as node exit or join, node failure or recovery, and can also realize high sending success rate in the high error code characteristics of the underwater acoustic channel.

[0005] The application can achieve the purpose by adopting the following technical scheme:

[0006] A dynamic MAC protocol implementation method based on receiving alignment is applied to an underwater acoustic communication network, the underwater acoustic communication network includes n sending nodes Node and 1 receiving node Sink located at the center position, all nodes are within the maximum transmission range; the underwater acoustic communication network can accommodate the upper limit of the number of sending nodes Node N MAX ; all nodes of the underwater acoustic communication network have a maximum transmission power P MAX , a maximum propagation delay T MAX , a protection time T Protect ; all nodes in the underwater acoustic communication network have their own set number, wherein the receiving node Sink is numbered 0, and the number value of the sending node Node is 1 to N MAX; the water acoustic communication network, the sending node Node sends information is divided into initial information Node class, control information class, data information class and reset information Node class, the initial information Node class is referred to as Node-Init class below, the data information class is referred to as data below, the reset information Node class is referred to as Node-Reset class below; the receiving node Sink sends information in the water acoustic communication network is divided into initial information Sink class, Ack confirmation information class and reset information Sink class, the initial information Sink class is referred to as Sink-Init class below, the reset information Sink class is referred to as Sink-Reset class below; the water acoustic communication network is divided into initialization phase, running phase and reset phase; the sending node Node has initialization state, idle waiting state, sending state and reset state; the receiving node Sink has initialization state, idle waiting state and reset state; the control information class sent by the sending node Node is divided into Yes class and No class, which respectively represent whether the sending node Node has data to send, and the control information class contains Ack confirmation information part; each sending node Node maintains a Node-Resend resend table for recording the sending and receiving conditions of the data of the node itself; the receiving node Sink maintains a Sink-Resend resend table for recording the sending and receiving conditions of the data of each sending node Node; the receiving node Sink sends Ack confirmation information class to confirm the receiving conditions of the data of the sending node Node; the sending node Node sends Node-Init class in the network initialization phase; the sending node Node sends Node-Reset class in the network reset phase; the receiving node Sink sends Sink-Init class in the network initialization phase; the receiving node Sink sends Sink-Reset class in the network reset phase; for the sending node Node, the dynamic MAC protocol implementation method comprises the following steps:

[0007] S1, all sending nodes Node are placed, N MAX , P MAX , T MAX and T Protect are set, and the node number of the sending node Node is set;

[0008] S2, the water acoustic communication network is started to enter the initialization phase, and all sending nodes Node enter the initialization state; the sending node Node sends the Node-Init class at the corresponding initial information sending time according to the node number of the node itself with the maximum transmission power, the Node-Init class includes the sending time stamp and the distance between the known sending node Node and the node itself, and then the Sink-Init class is received, wherein the Sink-Init class includes the sending time, sending sequence and data sending power P Dataand Received Signal-to-Noise Ratio (SNR) Threshold threshold ;

[0009] S3. The underwater acoustic communication network enters the operational phase, and the transmitting nodes enter an idle waiting state; all transmitting nodes transmit control information and data to the receiving nodes in sequence and cyclically according to the transmission order in the Sink-Init class; the transmitting nodes transmit the signal-to-noise ratio (SNR) threshold according to the receiving Sink-Init class. threshold The system adjusts its own received signal-to-noise ratio threshold; simultaneously, each transmitting node starts a transmission timer. When the current time is equal to or greater than the timer's set time, the transmitting node enters the transmission state. The first timer's set time is set to the transmission time specified for itself in the Sink-Init class. Based on the transmission order in the Sink-Init class, the transmitting node learns the number of the preceding transmitting node in the current network transmission sequence and listens for control information from that preceding node. When the transmitting node is idle... In the waiting state, when a control message class from the previous sending node is received, proceed to S3.1; when the sending node's own sending timer expires in the idle waiting state, proceed to S3.2; when the sending node receives an Ack acknowledgment message class from the receiving node Sink in the idle waiting state, proceed to S3.3; when the sending node receives a Node-Reset class from the sending node in the idle waiting state, proceed to S3.4; when the sending node receives a Sink-Reset class from the receiving node Sink in the idle waiting state, proceed to S3.5.

[0010] S3.1 When a sending node receives a control information class from the previous sending node, the sending node reads the Ack confirmation information part in the control information class and updates its own Node-Resend retransmission table. Then it determines the category of the control information class. If it is a No category, it proceeds to S3.2. If it is a Yes category, the node delays for T1 time and then proceeds to S3.2.

[0011] S3.2, the sending node Node adjusts the sending power to P1 and enters the sending state; the sending node Node performs information sending operation in the sending state, and the sent information is divided into control information and data, wherein the data is divided into new data which has not been sent before and retransmission data which has been sent before but is notified to be retransmitted by the Ack confirmation information part in the control information of the sending node Node of the previous sending order; in the sending state, the sending node Node first judges whether there is no new data to be sent and no retransmission data to be retransmitted, if yes, the control information of No type is sent, and after the sending is completed, the Node-Resend table of the sending node Node is updated and the timing moment of the sending timer of the sending node Node is updated; if not, the control information of Yes type is sent, and after the sending is completed, the sending power of the sending node Node is adjusted to P2; the sending node Node sends data with the power P2, and after the sending operation is completed, the Node-Resend table of the sending node Node is updated, the timing moment of the sending timer of the sending node Node is updated, and the sending node Node enters the idle waiting state;

[0012] S3.3, after the sending node Node receives the Ack confirmation information from the receiving node Sink, the Node-Resend table of the sending node Node is updated, and the sending node Node enters the idle waiting state;

[0013] S3.4, after the sending node Node receives the Node-Reset class from other sending nodes Node, the sending node Node forwards the Node-Reset class with the maximum sending power and enters the restart state; after the sending node Node receives the Sink-Reset class from the receiving node Sink in the restart state, the sending node Node enters S3.5;

[0014] S3.5, the sending node Node receives the Sink-Reset class from the receiving node Sink and enters the restart state, at this time, the underwater acoustic communication network enters the restart phase; after the sending node Node receives the Sink-Reset class from the receiving node Sink, the next network starting moment in the Sink-Reset class is obtained, the sending node Node backs off to the moment and enters S2;

[0015] For the receiving node Sink, the dynamic MAC protocol implementation method comprises the following steps:

[0016] T1, the receiving node Sink is laid out, N MAX , P MAX , T MAX and T Protect are set, and the self number of the receiving node Sink is set to 0;

[0017] T2, the water acoustic communication network is started into initialization phase, and the receiving node Sink enters initialization state; the receiving node Sink receives the Node-Init class sent by the sending node Node; the distance between the nodes in the water acoustic communication network is calculated, the sending order of the sending node Node and the sending time of each sending node Node are determined, the data sending power and the receiving signal-to-noise ratio threshold are determined, the above information is added into the Sink-Init class, and the Sink-Init class is broadcasted with the maximum sending power;

[0018] T3, the water acoustic communication network is started into running phase, and the receiving node Sink enters idle waiting state; when the receiving node Sink receives the control information class and data transmitted by the sending node Node, T3.1 is entered; meanwhile, the receiving node Sink maintains a down timer for each sending node Node; when the period of time during which the information of a sending node Node is not received is equal to or greater than the timing period of the down timer, the water acoustic communication network enters restart phase, the receiving node Sink enters restart state, and T3.2 is entered; when the receiving node Sink receives the Node-Reset class from the sending node Node, the water acoustic communication network enters restart phase, the receiving node Sink enters restart state, and T3.2 is entered;

[0019] T3.1, the receiving node Sink receives the control information and data from the sending node Node, updates the Sink-Resend table of the receiving node Sink and the down timer corresponding to the sending node Node, and then judges whether the information is from the last node in the sending cycle order; if not, no operation is performed and the idle waiting state is entered; if yes, the Ack confirmation information class is broadcasted with the maximum sending power according to the Sink-Resend table of the receiving node Sink;

[0020] T3.2, the receiving node Sink sets the next network starting time, adds the Sink-Reset class, and broadcasts the Sink-Reset class twice with the maximum sending power, and the interval time is T interual , and then the T2 is entered at the next network starting time.

[0021] Further, the initialization processes of the sending node Node and the receiving node Sink in the steps S2 and T2 are as follows:

[0022] The set of all sending nodes Node in the water acoustic communication network is N, the number of elements in N is n, and N i represents the sending node Node with the number i in the set N, 1≤i≤n, and N (i-1) represents the sending node Node with the first sending order in the set N i .

[0023] The sending node Node sends the Node-Init class at the corresponding initial information sending time point according to the number, including the sending time stamp; the sending node Node and the receiving node Sink that are not the first to send the Node-Init class will obtain the Node-Init class of the sending node Node that sends first, and calculate the distance from the sending node Node according to the sending time stamp in the Node-Init class; the sending node Node that sends the Node-Init class later will attach the collected distance information to the Node-Init class of itself and send it at the maximum transmission power; the interval of sending the Node-Init class between the sending node Node with adjacent number is T MAX +T init-max ; T MAX represents the maximum propagation delay; T init-max represents the transmission time of the Node-Init class in the case of containing the distance information of all sending nodes Node and itself except the node itself; the protocol stipulates that the upper limit of the number of sending nodes Node that can be accommodated in the underwater acoustic communication network is N MAX ; the receiving node Sink calculates the distance between the nodes in the underwater acoustic communication network according to the sending time stamp and the distance information in the collected Node-Init class after N MAX T MAX +Ti nit-max periods after the underwater acoustic communication network is started, decides the sending order of the sending node Node and the sending time point, data sending power and receiving signal-to-noise ratio threshold of N i , adds the above information into the Sink-Init class and broadcasts it at the maximum transmission power;

[0024] The initial information sending time point of N i is calculated as follows:

[0025] T init-send-i = (i-1) × (T MAX +T init-max )

[0026] wherein, T init-send-i represents the initial information sending time point of N i , and T init-max represents the transmission time of the Node-Init class in the case of containing the distance information of all sending nodes Node and itself except the node itself;

[0027] The above method for selecting the initial information sending time point can ensure that there is no conflict between the Node-Init classes and between the Node-Init class and the Sink-Init class in the network initialization stage, and at the same time, the initialization stage is efficiently completed;

[0028] The method for calculating the distance d is as follows: d = (T now -T init -T send )×v

[0029] Among them, T now For the current moment, T init T represents the transmission time of this Node-Init class. send The timestamp for transmission is given, and v is the speed of sound.

[0030] The method for the receiving node (Sink) to select the sending order is as follows:

[0031] The spatial distribution of all sending nodes (Nodes) and receiving nodes (Sinks) in the network is abstracted into a planar graph, and all sending nodes and receiving nodes are abstracted into points on the planar graph G; N i N(i-1) corresponds to points i and (i-1) on the planar graph G; if N (i-1) If no data is sent, then N i The time that can be sent in advance is denoted as W. (i-1)i W (i-1)i Abstracted into a directed edge E between point i and point (i-1) in a planar graph. (i-1)i The weights, W (i-1)i The calculation is as follows:

[0032]

[0033] Where, d (i-1)R N represents (i-1) Distance to the receiving node Sink; d iR N represents i Distance to the receiving node Sink; d (i-1)i N represents (i-1) and N i The distance between them; T Data v is the data transmission time; v is the speed of sound;

[0034] In this planar diagram, a depth-first search is used to find the cycle with the largest sum of weights; the order of the points traversed by the cycle is the network transmission order; in the cycle, the sending node with the smallest node number is set as the first sending node in the transmission cycle order;

[0035] The above method of selecting the transmission order can ensure that when data is transmitted cyclically in this order in the underwater acoustic communication network, the time saved is the greatest, the benefits are the greatest, and the network performance is the best.

[0036] After the receiving node Sink selects the transmission order, the number of receiving nodes Sink is N. i The method for selecting the sending time is as follows:

[0037]

[0038] Where, d (i-1)R N represents (i-1) Distance to the receiving node Sink; d iR N represents i Distance to the receiving node Sink; T send-i N represents i The transmission time; T send-(i-1) N represents (i-1) The transmission time; T Ctrl To control the transmission time of information classes, T Protect To protect time; T Data is the data transmission time; v is the speed of sound; and the transmission time of the first transmitting node in the transmission cycle sequence is set to 0.

[0039] The method of selecting the sending time described above can ensure that the data sent by the sending node will not collide with the data sent by the receiving node, while maximizing channel utilization and efficiency.

[0040] The receiving node Sink is N i Select data transmission power P Data The method is as follows:

[0041] P Data =P max -SNR init +SNR threshold-sink +SNR tolerant

[0042] SNR init The signal-to-noise ratio (SNR) of the Node-Init class received by the receiving node (Sink) from the sending node (Node) is represented by the Node-Init class. threshold-sink SNR represents the signal-to-noise ratio threshold for the sink node to receive any information. tolerant Indicates the fault-tolerant signal-to-noise ratio;

[0043] The method described above for selecting data transmission power can ensure that the data can be correctly received by the receiving node, Sink.

[0044] The receiving node Sink is N i The method for selecting the received signal-to-noise ratio threshold is as follows:

[0045] N (i-x) Represented as N i The first one found by moving forward in the sending order will not be N. i The sending nodes (Nodes) that cause data interference, where 1 ≤ x ≤ n; and the receiving nodes (Sinks) whose sending order is selected are N. i Find N(i-x) , N (i-x) will not cause data interference on N i The condition that will not cause data interference on N

[0046] t (i-1)-Ctrl-i-min t (i-x)-disturb-i-max

[0047] Wherein:

[0048]

[0049] t (i-x)-disturb-i-max = t (i-x)i + T Ctrl + T Data

[0050]

[0051] Wherein, t (i-1)-Ctrl-i-min represents the initial arrival time of the control information class sent by N (i-1) to N i , t (i-x)-disturb-i-max represents the time when the data sent by N (i-x) ends the interference on N i , t (i-x)(i-x+1) represents the propagation time from N (i-x) to N (i-x+1) , t (i-x+1)-wait represents the time that the sending node N (i-x+1) needs to wait after receiving the information of N (i-x) ; T Ctrl is the transmission time of the control information class; T Data is the transmission time of the data; d (i-x)R represents the distance from N (i-x) to the receiving node Sink; d (i-x+1)R represents the distance from N (i-x+1) to the receiving node Sink;

[0052] Therefore, the receiving node Sink selects the receiving signal-to-noise ratio threshold for N i :

[0053] SNR threshold-i = SNR Sum-disturb-i + SNR tolerant

[0054]

[0055] Wherein SNR threshold-i represents the receiving signal-to-noise ratio threshold selected by Sink for N i , SNR m-disturb-i represents the signal-to-noise ratio of N m when sending data at data sending poweri generated signal-to-noise ratio interference; SNR Sum-disturb-i represents the data sending power of the sending node Node in the underwater acoustic communication network when sending data i generated signal-to-noise ratio interference sum;

[0056] The above-mentioned idea of selecting the receiving signal-to-noise ratio is: finding a set of sending nodes Node in the underwater acoustic communication network that can cause data interference to each sending node Node except itself, and then assuming the scenario that all sending nodes Node in the set simultaneously cause interference to the sending node Node, the receiving signal-to-noise ratio that the sending node Node should set;

[0057] Further, in step S3.1, the delay time T1 is calculated as follows:

[0058]

[0059] The set of all sending nodes Node in the underwater acoustic communication network is N, the number of elements in N is n, and N i represents the sending node Node numbered i in the set N, N (i-1) represents the sending node Node with the first 1 sending order of N i ; wherein, d (i-1)R represents the distance from N (i-1) to the receiving node Sink; d iR represents the distance from N i to the receiving node Sink; t (i-1)i represents the propagation time between N (i-1) and N i ; T Data is the transmission time of data; v is the speed of sound; the delay time T1 calculated by the above-mentioned method can ensure that the data of N i and the data of N (i-1) do not cause collision at the receiving node Sink at the same time with the minimum delay time.

[0060] Further, in step S3.2, the calculation of the power P1 of the sending control information class of the sending node Node and the power P2 of the sending data is as follows:

[0061] P1=P MAX

[0062] P2=P Data

[0063] wherein, P MAX represents the maximum transmission power, and the sending node Node obtains the data sending power P DataP1 is the maximum transmit power to ensure that the control information can be correctly received, and P2 is selected to ensure that the data can be correctly received by the sink node.

[0064] Further, the Node-Resend table for the sending node Node and the Sink-Resend table for the sink node Sink are updated as follows:

[0065] The Node-Resend table for the sending node Node records the packet sequence number and the sending time of each new data sent by the sending node Node and stores them in the Node-Resend table. When the sending node Node receives the Ack confirmation information from the sink, the information is attached to the control information to be sent next time, and the Node-Resend table of the sending node Node is updated. When the sending node Node receives the control information from the sending node Node in the previous sending order, the Ack confirmation information part is obtained, and the Node-Resend table of the sending node Node is updated. The updating method of the Node-Resend table of the sending node Node is as follows: the Node-Resend table is traversed, and the corresponding table entry in the table with a packet sequence number less than the Ack confirmation information or the Ack confirmation sequence number for the node is deleted.

[0066] The sink node Sink maintains an Ack confirmation sequence number variable for each sending node Node, which indicates the packet sequence number of the next packet that the sink node Sink expects the node to send. For the sink node Sink, the node number of the sending node Node that sends the data and the packet sequence number of the data are recorded each time the data is successfully received. Then, the sink node Sink updates the Sink-Resend table for itself, and the updating method is as follows: the Sink-Resend table is checked for the data reception of the sending node Node, and it is checked whether the packet sequence number is the Ack confirmation sequence number of the sending node Node. If yes, the Ack confirmation sequence number of the sending node Node is updated to the latest one of the successfully received consecutive packet sequence numbers in the table entry of the sending node Node in the Sink-Resend table, and the table entries before the new Ack confirmation sequence number are deleted. If no, the packet sequence number is recorded in the table entry of the sending node Node in the Sink-Resend table.

[0067] After the sending node Node enters the sending state, it checks the Node-Resend table of itself. If it finds that the sending node Node has received the same acknowledgement serial number for three or more times in succession and the data represented by the acknowledgement serial number is stored in the Node-Resend table of itself, the fast retransmission mechanism is triggered, the data is retransmitted, the sending time of the data is updated after the transmission is completed, and the retransmission time limit becomes twice the original time limit. In the case where no data triggers the fast retransmission mechanism, if it is found that the difference between the sending time of the data and the current time is equal to or greater than the retransmission time limit T time-out of the data, the timeout retransmission mechanism is triggered, the data is retransmitted, and the sending time of the data is updated, and the retransmission time limit becomes twice the original time limit. The first retransmission time limit is calculated as follows:

[0068] T ftrst-time-out = 2 · T Round

[0069] T Round = n × (T Ctrl + T Data + T Protect )

[0070] wherein the set of all sending nodes Node in the underwater acoustic communication network is N, the number of N is n, T Round represents the total time consumed by each sending node Node for completing one control information transmission, one data transmission and waiting for the protection time under the condition that n sending nodes Node have data to send; T Ctrl is the transmission time of the control information, T Protect is the protection time, and T Data is the transmission time of the data.

[0071] The flexible combination of the fast retransmission mechanism and the timeout retransmission mechanism can ensure the reliability of the data while minimizing the time delay of the data and optimizing the network performance.

[0072] Further, the method for the receiving node Sink to send the Ack acknowledgement information class in step T3.1 is as follows:

[0073] When the sink receives the data or the No type control information from the last node in the sending order, the sink sends the Ack confirmation information, the content of which is the confirmation sequence number of each sending node, and the meaning is that the sink expects the packet sequence number of the next data sent by the sending node; in the normal scenario, the sink only receives the data or the No type control information from the last node in the sending order, and then sends the Ack confirmation information; however, when the underwater acoustic environment deteriorates, the risk of loss of the Ack confirmation information increases, and the sink can send the Ack confirmation information when it receives the data or the No type control information from other sending nodes, send more Ack confirmation information in one transmission cycle, and improve the anti-interference ability of the underwater acoustic communication network.

[0074] When the sending node receives the control information from the sending node in the previous sending order, the node updates the Node-Resend table after reading the Ack confirmation information part, and sends the Ack confirmation information part in the control information when it is time for the node to send the control information. In addition, when the sending node receives the Ack confirmation information from the sink, the sending node updates the Node-Resend table and ignores the Ack confirmation information part in the control information from the sending node in the previous sending order, and sends the content of the Ack confirmation information in the control information when it is time for the node to send the control information, so as to ensure that the content of the Ack information in the network can be updated in time.

[0075] Further, the method for updating the timing time of the sending timer of the sending node in step S3.2 is as follows:

[0076] When the current time is equal to or greater than the timing time of the sending timer, the sending node enters the sending state; when the sending node receives the control information from the sending node in the previous sending order before entering the sending state, the sending node enters the sending state; when the sending state of the sending node ends, the sending node updates the timing time of the sending timer; the timing time of the first sending timer is specified by the sink from the Sink-Init; the method for updating the timing time of the timer is as follows:

[0077]

[0078] wherein, T next-send-time represents the timing time of the next sending timer, T send-time represents the timing time of the current sending timer, and the planned sending time of the first round is T send-i , T Now represents the current time.

[0079] The method of updating the timer can ensure that the underwater acoustic communication network can operate normally and no conflict occurs in the case of loss of any control information class or data in the running stage of the underwater acoustic communication network.

[0080] Further, the use method of the sending node Node for the Node-Reset class and the receiving node Sink for the Sink-Reset class in steps S3.4, S3.5 and T3.2 is as follows:

[0081] For the sending node Node newly joining or exiting the underwater acoustic communication network, the Node-Reset class is broadcast to the underwater acoustic communication network, and the remaining sending nodes Node hear and turn from the current state to the restart state and forward the Node-Reset class after hearing the Node-Reset class; the receiving node Sink hears the Node-Reset class and turns from the current state to the restart state and broadcasts the Sink-Reset class twice after 2 times of maximum propagation delay; the interval T interval The calculation is as follows: T interval = T Ctrl + T Data + T Protect

[0082] Wherein, T Ctrl is the transmission time of the control information class, T Protect is the protection time; T Data is the transmission time of the data, and after twice broadcasting, all sending nodes Node can receive the Sink-Reset class from the receiving node Sink; the next network starting time is specified in the Sink-Reset class, and all nodes in the underwater acoustic communication network enter the initialization state at the next network starting time, and turn to S2;

[0083] Wherein, the next network starting time is: T Restart = T interval + 2·T MAX

[0084] Wherein, T MAX is the maximum propagation delay, and after 2 times of the maximum propagation delay, it can be ensured that all information in the underwater acoustic communication network has been emptied, and the next underwater acoustic communication network operation is ensured not to be disturbed by extra interference.

[0085] The use method of the sending node Node for the Node-Reset class and the receiving node Sink for the Sink-Reset class can ensure that the Node-Reset class can be correctly received by the receiving node Sink, the Sink-Reset class can be correctly received by the sending node Node, and the next network starting time will not be disturbed by the residual information of the last network.

[0086] Further, the method for using the down timer in the receiving node Sink in step T3.2 is as follows:

[0087] The receiving node Sink maintains a down timer for each sending node Node, when the period of not receiving information of a sending node Node within 10 min is equal to or greater than the timing period of the down timer, it is judged that the sending node Node is invalid, the topology of the underwater acoustic communication network changes, and the underwater acoustic communication network enters a restart phase, broadcasts the Sink-Reset class 2 times, and notifies the next network starting time of the underwater acoustic communication network; when the information of a sending node Node is received within 10 min, the down timer of the corresponding sending node Node is restarted.

[0088] The above-mentioned method for using the down timer can ensure that the receiving node Sink will not misjudge that the sending node Node has been down due to the deterioration of the underwater acoustic communication network operating environment.

[0089] The present application has the following advantages and effects relative to the prior art:

[0090] 1. The dynamic MAC protocol proposed in the present application has higher channel utilization, less end-to-end delay, higher throughput and transmission efficiency in a low-load scenario.

[0091] 2. The dynamic MAC protocol proposed in the present application realizes collision-free through accurate scheduling, and has a 100% success rate of sending without considering the interference of the high error code characteristics of the underwater acoustic channel.

[0092] 3. The dynamic MAC protocol proposed in the present application can cope with multiple dynamic scenarios such as node exit or joining, node failure or recovery, and ensure normal operation of the network.

[0093] 4. Under the interference of the high error code characteristics of the underwater acoustic channel, the dynamic MAC protocol proposed in the present application effectively avoids data loss by increasing the Ack confirmation feedback mechanism, and realizes high sending success rate. DETAILED DESCRIPTION

[0094] The accompanying drawings, which are included to provide a further understanding of the present application and constitute a part of this application, illustrate certain illustrative embodiments of the present application and are used to explain the present application, but do not limit the present application. In the drawings:

[0095] Figure 1 is a flowchart of a receiving alignment-based dynamic MAC protocol for a sending node Node disclosed in the present application;

[0096] Figure 2is a flow chart about the receiving node Sink in the dynamic MAC protocol based on receiving alignment disclosed by the application;

[0097] Figure 3 is a network model graph of the dynamic MAC protocol based on receiving alignment disclosed by the application.

[0098] Figure 4 is a result graph about the normalized throughput in the network performance measurement index of the dynamic MAC protocol based on receiving alignment disclosed by the application.

[0099] Figure 5 is a result graph about the end-to-end average delay in the network performance measurement index of the dynamic MAC protocol based on receiving alignment disclosed by the application.

[0100] Figure 6 is a result graph about the sending success rate in the network performance measurement index of the dynamic MAC protocol based on receiving alignment disclosed by the application.

[0101] Figure 7 is a result graph about the average energy consumption in the network performance measurement index of the dynamic MAC protocol based on receiving alignment disclosed by the application.

[0102] Figure 8 is a result graph about the fairness index in the network performance measurement index of the dynamic MAC protocol based on receiving alignment disclosed by the application. DETAILED DESCRIPTION

[0103] In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are some of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0104] EMBODIMENT

[0105] A network model suitable for the implementation method of the dynamic MAC protocol based on receiving alignment in the underwater acoustic communication network in the embodiment is as shown in Figure 3As shown, there are two types of nodes in the underwater acoustic communication network, which are: sending nodes Node located around the underwater acoustic communication network and receiving nodes Sink located in the center of the underwater acoustic communication network; the underwater acoustic communication network contains a plurality of sending nodes Node and a receiving node Sink; all nodes are within the maximum transmission range; the propagation speed of underwater acoustic is 1500m / s, the data packet size is 2048 bytes, the modulation rate of underwater acoustic modem is 9600bps, the guard time is 0.05s, the fault tolerance power is 0.001dB, the minimum signal-to-noise ratio for correct data reception is 10dB, the maximum propagation delay is 3s; the maximum transmission power is 190dB; the upper limit of the number of sending nodes Node that the underwater acoustic communication network can accommodate is 20; the set of sending nodes Node in the underwater acoustic communication network is N={N1, N2, N3, N4, N5, N6, N7, N8}; specifically, the whole method comprises the following steps:

[0106] S1, all sending nodes Node are laid out, and the upper limit of the number of sending nodes Node that the underwater acoustic communication network can accommodate is set to 20, the maximum transmission power is set to 190dB, the maximum propagation delay is set to 3s, and the guard time is set to 0.05s, the self-number N1 of the sending node Node is set to 1, N2 is set to 2, N3 is set to 3, N4 is set to 4, N5 is set to 5, N6 is set to 6, N7 is set to 7, and N8 is set to 8.

[0107] S2, start the underwater acoustic communication network to enter the initialization phase, and all sending nodes Node enter the initialization state; the sending node Node sends its own Node-Init class at the maximum transmission power at the corresponding initial information sending time according to its own node number, and the Node-Init class includes the sending timestamp and the known distance between the sending node Node and the node itself, and then receives the Sink-Init class, which includes the sending time, sending order, data sending power P Data , the receiving signal-to-noise ratio threshold SNR threshold of each sending node Node.

[0108] S3, the underwater acoustic communication network enters the running phase, and the sending node Node enters the idle waiting state; all sending nodes Node transmit control information class and data to the receiving node Sink in order and circularly according to the sending order in the Sink-Init class; the sending node Node transmits the control information class and data to the receiving node Sink according to the receiving signal-to-noise ratio threshold SNR threshold, adjust its own receiving signal-to-noise ratio threshold value; at the same time, all sending nodes Node each start a sending timer, when the current time is equal to or greater than the timing time of the sending timer, the sending node Node enters the sending state, the first timing time of the sending timer is set as the sending time specified for the node in the Sink-Init class; the sending node Node learns the number of the sending node Node of the previous sending order in the current network operation sending order according to the sending order in the Sink-Init class, and listens to the control information class from the sending node Node of the previous sending order; when the sending node Node is in the idle waiting state, receives the control information class from the sending node Node of the previous sending order, and goes to S3.1; when the sending node Node is in the idle waiting state, the sending timer of the sending node Node expires, and goes to S3.2; when the sending node Node is in the idle waiting state, receives the Ack confirmation information class from the receiving node Sink, and goes to S3.3; when the sending node Node is in the idle waiting state, receives the Node-Reset class from the sending node Node, and goes to S3.4; when the sending node Node is in the idle waiting state, receives the Sink-Reset class from the receiving node Sink, and goes to S3.5;

[0109] S3.1, when the sending node Node receives the control information class from the sending node Node of the previous sending order, the sending node Node reads the Ack confirmation information part in the control information class and updates its own Node-Resend resend table, then judges the class of the control information class, if it is No class, go to S3.2, if it is Yes class, the node delays T1 time and goes to S3.2;

[0110] S3.2, the sending node Node adjusts the sending power to P1 and enters the sending state; the sending node Node performs information sending work in the sending state, and the sent information is divided into control information and data, wherein the data is divided into new data not sent before and retransmission data which has been sent before but is notified to be retransmitted by the Ack confirmation information part in the control information of the sending node Node of the previous sending order; in the sending state, the sending node Node first judges whether there is no new data to be sent and no retransmission data to be retransmitted, if yes, the control information of No type is sent, and after the sending is completed, the Node-Resend table of the sending node Node is updated, and the timing time of the sending timer of the sending node Node is updated; if not, the control message of Yes type is sent, and after the sending is completed, the sending power of the sending node Node is adjusted to P2; the sending node Node sends data at the power P2, updates the Node-Resend table of the sending node Node after the sending operation is completed, updates the timing time of the sending timer of the sending node Node, and enters the idle waiting state;

[0111] S3.3, after the sending node Node receives the Ack confirmation information from the receiving node Sink, the Node-Resend table of the sending node Node is updated, and the sending node Node enters the idle waiting state;

[0112] S3.4, after the sending node Node receives the Node-Reset class from other sending nodes Node, the sending node Node forwards the operation at the maximum sending power, and enters the restart state; after the receiving node Sink receives the Sink-Reset class, the sending node Node enters S3.5 in the restart state;

[0113] S3.5, the sending node Node receives the Sink-Reset class from the receiving node Sink, enters the restart state, and at this time the underwater acoustic communication network enters the restart phase; after the sending node Node receives the Sink-Reset class from the receiving node Sink, the next network starting time in the Sink-Reset class is obtained, the sending node Node backs off to the time and enters S2;

[0114] T1, the receiving node Sink is laid, the upper limit of the number of sending nodes Node that can be accommodated by the underwater acoustic communication network is set to 20, the maximum sending power is set to 190 dB, the maximum propagation delay is set to 3 s, and the protection time is set to 0.05 s, and the self number of the receiving node Sink is set to 0;

[0115] T2, the water acoustic communication network is started into initialization phase, and the receiving node Sink enters initialization state; the receiving node Sink receives the Node-Init class sent by the sending node Node; the distance between the nodes in the water acoustic communication network is calculated, the sending order of the sending node Node and the sending time of each sending node Node are determined, the data sending power and the receiving signal-to-noise ratio threshold are determined, the above information is added into the Sink-Init class, and the Sink-Init class is broadcasted with the maximum transmission power;

[0116] T3, the water acoustic communication network enters running phase, and the receiving node Sink enters idle waiting state; when the receiving node Sink receives the control information class and data transmitted by the sending node Node, T3.1 is entered; meanwhile, the receiving node Sink maintains a down timer for each sending node Node; when the period of time during which the information of a sending node Node is not received is equal to or greater than the timing period of the down timer, the water acoustic communication network enters restart phase, the receiving node Sink enters restart state, and T3.2 is entered; when the receiving node Sink receives the Node-Reset class from the sending node Node, the water acoustic communication network enters restart phase, the receiving node Sink enters restart state, and T3.2 is entered;

[0117] T3.1, the receiving node Sink receives the control information and data from the sending node Node, updates the Sink-Resend table of the receiving node Sink and the down timer corresponding to the sending node Node, and then judges whether the information is from the last node in the sending cycle order; if not, no operation is performed and the idle waiting state is entered; if yes, the Ack confirmation information class is broadcasted with the maximum transmission power according to the Sink-Resend table of the receiving node Sink;

[0118] T3.2, the receiving node Sink sets the next network starting time, adds the Sink-Reset class, and broadcasts the Sink-Reset class twice with the maximum transmission power, and the interval time is T interval , and then the process is transferred to T2 at the next network starting time.

[0119] The initialization processes of the sending node Node and the receiving node Sink in steps S2 and T2 are as follows:

[0120] The sending node Node sends the Node-Init class at the corresponding initial information sending moment according to the number, including the sending time stamp; the sending node Node and the receiving node Sink that are not the first to send the Node-Init class will obtain the Node-Init class of the sending node Node that sends first, and calculate the distance from the sending node Node according to the sending time stamp in the Node-Init class; the sending node Node that sends the Node-Init class later will attach the collected distance information to the Node-Init class of itself and send it at the maximum transmission power; the interval of sending the Node-Init class between the sending node Node with adjacent numbers is T MAX + T init-max ; T MAX represents the maximum propagation delay, and the value is 3 s; T init-max represents the transmission time of the Node-Init class in the case of containing the distance information of all sending nodes Node and itself except the node itself, and the value is 0.16 s; the protocol stipulates that the upper limit of the number of sending nodes Node that can be accommodated in the underwater acoustic communication network is N MAX , and the value is 20; the receiving node Sink calculates the distance between the nodes in the underwater acoustic communication network according to the sending time stamp and the distance information in the collected Node-Init class after 20 periods of 3 s+0.16 s after the underwater acoustic communication network is started, and determines the sending order of the sending nodes Node and the sending moment, data sending power and receiving signal-to-noise ratio threshold value of N i , 1≤i≤8, and broadcasts the Sink-Init class with the above information and at the maximum transmission power;

[0121] wherein, the initial information sending moment calculation method of N i is as follows:

[0122] T init-send-i = (i-1) × (T MAx + T init-max )

[0123] wherein, Ti nit-send-i represents the initial information sending moment of N i , 1≤i≤8; T MAX represents the maximum propagation delay, and the value is 3 s; T init-max represents the transmission time of the Node-Init class in the case of containing the distance information of all sending nodes Node and itself except the node itself, and the value is 0.16 s;

[0124] wherein, the distance d calculation method is as follows: d = (T now -T init -T send ) × v

[0125] Among them, T now For the current moment, T init T represents the transmission time of this Node-Init class. send The timestamp for transmission is given, and v is the speed of sound, with a value of 1500 m / s.

[0126] The method for the receiving node (Sink) to select the sending order is as follows:

[0127] The spatial distribution of all sending nodes (Nodes) and receiving nodes (Sinks) in the network is abstracted into a planar graph, and all sending nodes and receiving nodes are abstracted into points on the planar graph G; N i and N (i-1) The corresponding points on the planar graph G are point i and point (i-1); if N (i-1) If no data is sent, then N i The time that can be sent in advance is denoted as W. (i-1)i W (i-1)i Abstracted into a directed edge E between point i and point (i-1) in a planar graph. (i-1)i The weights, W (i-1)i The calculation is as follows:

[0128]

[0129] Where, d (i-1)R N represents (i-1) Distance to the receiving node Sink; d iR N represents i Distance to the receiving node Sink; d (i-1)i N represents (i-1) and N i The distance between them; T Data The data transmission time is 1.712s; v is the speed of sound, which is 1500m / s.

[0130] In this planar diagram, a depth-first search is used to find the cycle with the largest weight sum; the order of the points traversed by the cycle is the network transmission order; in the cycle, the transmitting node with the smallest node number is set as the first transmitting node in the transmission cycle order; the transmission order is selected as: N1→N2→N3→N4→N5→N6→N7→N8;

[0131] After the receiving node Sink selects the transmission order, the number of receiving nodes Sink is N. i The method for selecting the sending time is as follows:

[0132] Where, d (i-1)R N represents (i-1)Distance to receiving node Sink; d iR N i Distance to receiving node Sink; T send-i N i Transmission time of N send-(i-1) N (i-1) Transmission time of N Ctrl Transmission time of control information, 0.04s, T Protect Protection time, 0.05s; T Data Transmission time of data, 1.712s; v is sound speed, 1500m / s; the first transmission node in the sending cycle sequence is set to 0; T send-i =0s, 1.802s, 3.603s, 5.407s, 7.205s, 9.009s, 10.808s, 12.61s. 1≤i≤8.

[0133] Receiving node Sink is N i Select data transmission power P Data The method is as follows:

[0134] P Data =P max -SNR init +SNR threshold - sink +SNR tolerant

[0135] Where P MAX represents the maximum transmission power, 190dB; SNR init represents the signal-to-noise ratio of the receiving node Sink receiving the Node-Init class from the sending node Node, SNR threshold-sink represents the signal-to-noise ratio threshold of the receiving node Sink receiving any information, SNR tolerant represents the fault tolerance signal-to-noise ratio; for N i , the data transmission power P Data is 128dB, 1≤i≤8;

[0136] Receiving node Sink is N i The method for selecting the receiving signal-to-noise ratio threshold is as follows:

[0137] N (i-x) represents the first sending node Node found along the sending sequence that does not cause data interference to N i , where 1≤x≤n; after the receiving node Sink selects the sending sequence, N i finds N i , N (i-x) , N (i-x)Will not affect N i The condition that causes data interference is: t (i-1)-Ctrl-i-min >t (i-x)-disturb-i-max

[0138] in:

[0139]

[0140] t (i-x)-disturb-i-max =t (i-x)i +T Ctrl +T Data

[0141]

[0142] Among them, t (i-1)-Ctrl-i-min N represents (i-1) To N i The initial arrival time of the control message class sent, t (i-x)-disturb-i-max N represents (i-x) The data sent to N i The moment the interference ends, t (i-x)(i-x+1) N represents (i-x) To N (i-x+1) The propagation time, t (i-x+1)-wait Indicates sending node N (i-x+1) After receiving N (i-x) The waiting time after receiving the information; T Ctrl To control the transmission time of information classes, a value of 0.004s is set; T Data The data transmission time is 1.712 seconds; d (i-x)R N represents (i-x) Distance to the receiving node Sink; d (i-x+1)R N represents (i-x+1) Distance to the receiving node Sink;

[0143] Therefore, the sink node is N. i Select the receive signal-to-noise ratio threshold as follows:

[0144] SNR threshold-i =SNR Sum-disturb-i +SNR tolerant

[0145]

[0146] SNR threshold-i Indicates Sink is N i Select the receive signal-to-noise ratio (SNR) threshold. m-disturb-i N represents m When transmitting data at data transmission power, for N i The resulting signal-to-noise ratio interference; SNR Sum-disturb-iN represents the sending node Node in the underwater acoustic communication network, and the sending node Node sends data at a data sending power i The generated signal-to-noise ratio sum of interference, for N i , the received signal-to-noise ratio threshold SNR threshold-i is 10dB, and 1≤i≤8.

[0147] In step S3.1, the delay time T1 is calculated as follows:

[0148] The set of all sending nodes Node in the underwater acoustic communication network is N, the number of elements in N is n, N i represents the sending node Node numbered i in the set N, N (i-1) represents the sending node Node with the first 1 sending order in N i ; wherein d (i-1)R represents the distance from N (i-1) to the receiving node Sink; d iR represents the distance from N i to the receiving node Sink; t (i-1)i represents the propagation time between N (i-1) and N i ; T Data is the transmission time of data, and the value is 1.712s; v is the speed of sound, and the value is 1500m / s; for N i , T1=1.355s, 1.355s, 1.354s, 1.357s, 1.354s, 1.356s, 1.356s, 1.356s; 1≤i≤8.

[0149] In step S3.2, the calculation of the power P1 of the sending control information class of the sending node Node and the power P2 of the sending data is as follows: P1=P MAX ; P2=P Data .

[0150] Wherein, P MAX represents the maximum transmission power, and the value is 190dB, the sending node Node obtains the data sending power P Data of its own node in the Sink-Init class received in S2, and the value is 128dB.

[0151] In steps S3.1, S3.2, S3.3 and T3.1, the updating method of the Node-Resend resend table for the sending node Node itself and the Sink-Resend resend table for the receiving node Sink itself is as follows:

[0152] For the Node-Resend resend table of the sending node Node itself, the sending node Node records the packet sequence number and sending time and stores them in the Node-Resend resend table every time it sends new data; when the sending node Node receives the Ack confirmation information from the Sink, it will attach this information to the control information to be sent next time, and then update the Node-Resend resend table of the sending node Node; when the sending node Node receives the control information from the sending node Node in the previous sending order, it acquires the Ack confirmation information part, and then updates the Node-Resend resend table of the sending node Node; the updating method of the Node-Resend resend table of the sending node Node is: traversing the Node-Resend resend table, deleting the corresponding table entry in the table whose packet sequence number is less than the Ack confirmation information or the Ack confirmation sequence number for the node;

[0153] The receiving node Sink maintains an Ack confirmation sequence number variable for each sending node Node, which indicates the packet sequence number of the next packet that the receiving node Sink expects the node to send to it; for the receiving node Sink, every time it successfully receives data, it records the node number of the sending node Node that sends the data and the packet sequence number of the data; then the receiving node Sink updates the Sink-Resend resend table of the receiving node Sink, and the updating method is: checking the data reception of the sending node Node in the Sink-Resend resend table, checking whether the packet sequence number is the Ack confirmation sequence number of the sending node Node, if yes, updating the Ack confirmation sequence number of the sending node Node to the latest one in the successfully received continuous packet sequence numbers in the table entry of the sending node Node in the Sink-Resend resend table, and deleting the table entries before the new Ack confirmation sequence number; if not, recording the packet sequence number in the table entry of the sending node Node in the Sink-Resend resend table;

[0154] After the sending node Node enters the sending state, it checks the Node-Resend resend table of the sending node Node, and if it finds that the sending node Node has received the same Ack confirmation sequence number for 3 times or more and the data represented by the Ack confirmation sequence number is stored in the Node-Resend resend table of the sending node Node, it triggers the fast retransmission mechanism, retransmits the data, updates the sending time of the data after the sending is completed, and sets the retransmission time limit to twice the original value; in the case where no data triggers the fast retransmission mechanism, if it finds that the difference between the sending time of the data and the current time is equal to or greater than the retransmission time limit T time-out of the data, it triggers the timeout retransmission mechanism, retransmits the data, and updates the sending time of the data, and sets the retransmission time limit to twice the original value; the first retransmission time limit is calculated as follows: T first-time-out= 2*T Round

[0155] T Round = n x (T Ctrl + T Data + T Protect )

[0156] wherein the set of all sending nodes Node in the underwater acoustic communication network is N, the number of N is n, the value is 8, T Round represents the total time consumed by each sending node Node to complete one control information class transmission, one data transmission and waiting protection time in the case that all n sending nodes Node have data to send, the value is 14.614s; T Ctrl is the transmission time of the control information class, the value is 0.04s, T Protect is the protection time, the value is 0.05s; T Data is the transmission time of the data, the value is 1.712s; T first-time-out the value is 29.229s.

[0157] The method for sending Ack confirmation information class by the receiving node Sink in step T3.1 is as follows:

[0158] When the receiving node Sink receives the data or No class control information class of the last node in the sending cycle sequence, it sends the Ack confirmation information class, the content of which is the confirmation sequence number of each sending node Node, which means the packet sequence number expected by the sending node Node to send data next time; in the usual scenario, the receiving node Sink will only receive the data or No class control information class of the last node in the sending cycle sequence, and then send the Ack confirmation information class; but when the underwater acoustic environment is poor, the risk of loss of the Ack confirmation information class increases, and the Sink can send the Ack confirmation information class when it receives the data or No class control information class of other sending nodes Node, send more Ack confirmation information classes in one transmission cycle, and improve the anti-interference ability of the underwater acoustic communication network;

[0159] When the sending node Node receives the control information class from the sending node Node in the previous sending order, the node reads the Ack confirmation information part, updates the Node-Resend table of itself, and when it is the turn of the sending node Node to send the control information class, it puts the Ack confirmation information part into the control information class and then sends it. In addition, when the sending node Node receives the Ack confirmation information class from the Sink, it updates the Node-Resend table of itself, ignores the Ack confirmation information part in the control information class from the sending node Node in the previous sending order, and when it is the turn of the sending node Node to send the control information class, it puts the content of the Ack confirmation information class into the control information class and then sends it, so as to ensure that the content of the Ack information in the network can be updated in time.

[0160] In step S3.2, the method for updating the timing moment of the sending timer of the sending node Node is as follows:

[0161] When the current time is equal to or greater than the timing moment of the sending timer, the sending node Node enters the sending state; when the sending node Node receives the control information class from the sending node Node in the previous sending order before entering the sending state, it enters the sending state; when the sending state of the sending node Node ends, the sending node Node updates the timing moment of the sending timer; the timing moment of the sending timer is specified by the receiving node Sink from the Sink-Init class for the first time; the method for updating the timing moment of the timer is as follows:

[0162]

[0163] Wherein, T next-send-time represents the timing moment of the next sending timer, T send-time represents the timing moment of the current sending timer, T Now represents the current time, and the planned sending time of the first round is T send-i , T send-i = 0s, 1.802s, 3.603s, 5.407s, 7.205s, 9.009s, 10.808s, 12.61s. 1≤i≤8.

[0164] In steps S3.4, S3.5 and T3.2, the use method of the sending node Node for the Node-Reset class and the use method of the receiving node Sink for the Sink-Reset class are as follows:

[0165] For a newly joined or withdrawn transmitting node in the underwater acoustic communication network, it broadcasts a Node-Reset class to the network. Upon hearing this, other transmitting nodes transition from their current state to a restart state and forward the Node-Reset class. Upon hearing the Node-Reset class, the receiving node transitions from its current state to a restart state and broadcasts a Sink-Reset class twice after twice the maximum propagation delay. The interval T between the two broadcasts is... interval The calculation is as follows:

[0166] T interval =T Ctrl +T Data +T Protect

[0167] Among them, T Ctrl To control the transmission time of information classes, a value of 0.04s is set for T. Prottec The protection time is set to 0.05s; T Data T represents the data transmission time, with a value of 1.712s. interval The value is 1.802s; after two broadcasts, it can be guaranteed that all sending nodes receive the Sink-Reset class from the receiving node; the Sink-Reset class specifies the next network startup time, and all nodes in the underwater acoustic communication network enter the initialization state at the next network startup time and switch to S2;

[0168] The next network startup time is: T Restart =T interval +2·T MAX .

[0169] Where T MAX T represents the maximum propagation delay, with a value of 3 seconds. interval The value is 1.802s; T Restart The value is 7.802s.

[0170] The usage of the sink's crash timer in step T3.2 is as follows:

[0171] The receiving node (Sink) maintains a crash timer for each sending node (Node). If the period during which no information is received from a sending node within 10 minutes is equal to or greater than the timeout period of the crash timer, the sending node is considered to have failed, the topology of the underwater acoustic communication network has changed, and the underwater acoustic communication network enters the restart phase. The Sink-Reset class is broadcast twice to notify the underwater acoustic communication network of the next network startup time. When information is received from a sending node within 10 minutes, the corresponding crash timer for that sending node is reset.

[0172] The simulation results of the embodiment will be given as follows:

[0173] The network performance measurement indexes, normalized throughput, end-to-end average delay, transmission success rate, average energy consumption and fairness index are defined as follows:

[0174]

[0175]

[0176]

[0177]

[0178]

[0179] wherein, m i represents the total number of data packets transmitted by node N i in a period of time; the network simulation parameters are as follows:

[0180] Table 1. Network simulation parameter table

[0181] Parameter Parameter value Parameter Parameter value Simulation time 10000s Poisson arrival rate λ∈[0, 1] Number of sending nodes 8 Number of central nodes 1 Modulation rate 9.6 kbps Carrier frequency 20 kHz Data packet size 2048 bytes Guard time 0.05s Maximum transmit power 190 dB Sound speed 1500 m / s

[0182] The network performance of the dynamic MAC protocol based on reception alignment includes: normalized throughput, end-to-end average delay, transmission success rate, average energy consumption and fairness index, respectively as shown in Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 : wherein DRA-MAC is the dynamic MAC protocol based on reception alignment described in the application; Aloha is ALOHA protocol; MR-SFAMA is S-FAMA protocol based on multi-receiver mechanism; DQA-MAC is adaptive scheduling MAC protocol based on delay and queue perception.

[0183] The above embodiment is the preferred embodiment of the application, but the embodiment of the application is not limited by the above embodiment, any change, modification, replacement, combination, simplification made without departing from the spirit and principle of the application, should be equivalent to the replacement mode, and all are included in the protection scope of the application.

Claims

1. A method for implementing a dynamic MAC protocol based on receiving alignment, applied to an underwater acoustic communication network, the underwater acoustic communication network comprising n sending nodes Node and 1 receiving node Sink located at the center, all nodes being within the maximum transmission range; the underwater acoustic communication network can accommodate a maximum of N sending nodes Node MAX , all nodes having a maximum transmission power P MAX , a maximum propagation delay T MAX , a guard time T Protect , all nodes in the underwater acoustic communication network having a self-set number, wherein the receiving node Sink is numbered 0, and the sending nodes Node are numbered between 1 and N MAX ; the sending nodes Node send information, which is divided into initial information Node class, control information class, data information class, and restart information Node class, the initial information Node class being referred to as Node-Init class, the data information class being referred to as data, and the restart information Node class being referred to as Node-Reset class; the receiving node Sink sends information, which is divided into initial information Sink class, Ack confirmation information class, and restart information Sink class, the initial information Sink class being referred to as Sink-Init class, and the restart information Sink class being referred to as Sink-Reset class; the underwater acoustic communication network is divided into an initialization phase, a running phase, and a restart phase; the sending nodes Node have an initialization state, an idle waiting state, a sending state, and a restart state; the receiving node Sink has an initialization state, an idle waiting state, and a restart state; the control information class sent by the sending nodes Node is divided into Yes class and No class, indicating whether the sending nodes Node have data to send, and the control information class contains an Ack confirmation information part; each sending node Node maintains a Node-Resend resend table for recording the sending and receiving of the data of the node; the receiving node Sink maintains a Sink-Resend resend table for recording the sending and receiving of the data of each sending node Node; the receiving node Sink sends the Ack confirmation information class to confirm the receiving of the data of the sending nodes Node; the sending nodes Node send the Node-Init class in the network initialization phase; the sending nodes Node send the Node-Reset class in the network restart phase; the receiving node Sink sends the Sink-Init class in the network initialization phase; the receiving node Sink sends the Sink-Reset class in the network restart phase; for the sending nodes Node, the method for implementing the dynamic MAC protocol comprises the following steps: S1, place all sending nodes Node, set N MAX , P MAX , T MAX and T Protect , set the own number of sending nodes Node; S2, start the underwater acoustic communication network into the initialization phase, all sending nodes Node enter the initialization state; sending nodes Node according to its own node number in the corresponding initial information sending moment with maximum transmission power to send its own Node-Init class, Node-Init class includes sending time stamp and known sending node Node and its own node distance, then receive Sink-Init class, the Sink-Init class includes the sending time, sending order, data sending power P Data and receiving signal-to-noise ratio threshold SNR threshold ; S3, the underwater acoustic communication network enters a running phase, and a sending node Node enters an idle waiting state; all sending nodes Node transmit control information classes and data to a receiving node Sink in sequence and cyclically according to a sending sequence in the Sink-Init class; the sending nodes Node adjust their own receiving signal-to-noise ratio thresholds according to a receiving signal-to-noise ratio threshold SNR in the Sink-Init class; meanwhile, all sending nodes Node each start a sending timer, and when a current time is equal to or greater than a timing time of the sending timer, the sending node Node enters a sending state, and a first timing time of the sending timer is set as a sending time specified for the node itself in the Sink-Init class; the sending nodes Node know a number of a sending node Node of a previous sending order in a current network running sending sequence according to the sending sequence in the Sink-Init class, and listen to a control information class from the sending node Node of the previous sending order; when the sending node Node receives the control information class from the sending node Node of the previous sending order in the idle waiting state, S3.1 is entered; when the sending node Node receives the control information class from the sending node Node of the previous sending order in the idle waiting state, S3.2 is entered; when the sending node Node receives an Ack confirmation information class from the receiving node Sink in the idle waiting state, S3.3 is entered; when the sending node Node receives a Node-Reset class from the sending node Node in the idle waiting state, S3.4 is entered; and when the sending node Node receives a Sink-Reset class from the receiving node Sink in the idle waiting state, S3.5 is entered. threshold , the underwater acoustic communication network enters a running phase, and a sending node Node enters an idle waiting state; all sending nodes Node transmit control information classes and data to a receiving node Sink in sequence and cyclically according to a sending sequence in the Sink-Init class; the sending nodes Node adjust their own receiving signal-to-noise ratio thresholds according to a receiving signal-to-noise ratio threshold SNR in the Sink-Init class; meanwhile, all sending nodes Node each start a sending timer, and when a current time is equal to or greater than a timing time of the sending timer, the sending node Node enters a sending state, and a first timing time of the sending timer is set as a sending time specified for the node itself in the Sink-Init class; the sending nodes Node know a number of a sending node Node of a previous sending order in a current network running sending sequence according to the sending sequence in the Sink-Init class, and listen to a control information class from the sending node Node of the previous sending order; when the sending node Node receives the control information class from the sending node Node of the previous sending order in the idle waiting state, S3.1 is entered; when the sending node Node receives the control information class from the sending node Node of the previous sending order in the idle waiting state, S3.2 is entered; when the sending node Node receives an Ack confirmation information class from the receiving node Sink in the idle waiting state, S3.3 is entered; when the sending node Node receives a Node-Reset class from the sending node Node in the idle waiting state, S3.4 is entered; and when the sending node Node receives a Sink-Reset class from the receiving node Sink in the idle waiting state, S3.5 is entered. S3.1, when the sending node Node receives the control information class from the sending node Node of the previous sending order, the sending node Node reads the Ack confirmation information part in the control information class and updates its Node-Resend table, and then judges the category of the control information class, if it is No category, it goes to S3.2, if it is Yes category, the node delays T1 time and then goes to S3.2; S3.2, the sending node Node adjusts the sending power to P1 and enters the sending state; the sending node Node performs information sending work in the sending state, and the sent information is divided into control information class and data, wherein the data is divided into new data which has not been sent before and retransmission data which has been sent before but is informed by the Ack confirmation information class or the Ack confirmation information part in the control information class of the sending node Node of the previous sending order that the data needs to be retransmitted; the sending node Node in the sending state first judges whether the node has no new data to send and no retransmission data to retransmit, if yes, it sends the control information class of No category, updates the Node-Resend table and the timing time of the sending timer after sending; if not, it sends the control message class of Yes category, and adjusts the sending power of the sending node Node to P2 after sending; the sending node Node sends data with power P2, updates the Node-Resend table and the timing time of the sending timer after sending, and enters the idle waiting state; S3.3, after the sending node Node receives the Ack confirmation information class from the receiving node Sink, it updates the Node-Resend table and enters the idle waiting state; S3.4, after the sending node Node receives the Node-Reset class from other sending nodes Node, it forwards with the maximum sending power and enters the restart state; After the sending node Node receives the Sink-Reset class from the receiving node Sink in the restart state, it goes to S3.5; S3.5, the sending node Node receives the Sink-Reset class from the receiving node Sink and enters the restart state, at this time the underwater acoustic communication network enters the restart phase; after the sending node Node receives the Sink-Reset class from the receiving node Sink, it obtains the next network starting time in the Sink-Reset class, backs off to the time and goes to S2; For the receiving node Sink, the dynamic MAC protocol implementation method comprises the following steps: T1, set N for the receiving node Sink MAX , P MAX , T MAX and T Protect , set the own number of the receiving node Sink as 0; T2, the underwater acoustic communication network enters the initialization phase, and the receiving node Sink enters the initialization state; the receiving node Sink receives the Node-Init class sent by the sending node Node; the distance between nodes in the underwater acoustic communication network is calculated, the sending order of the sending node Node and the sending time of each sending node Node, the data sending power and the receiving signal-to-noise ratio threshold are determined, and the above information is added to the Sink-Init class and broadcasted at the maximum transmission power; T3, the underwater acoustic communication network enters the running phase, and the receiving node Sink enters the idle waiting state; when the receiving node Sink receives the control information class and data transmitted by the sending node Node, it enters T3.1; at the same time, the receiving node Sink maintains a down timer for each sending node Node; when the period of not receiving information from a sending node Node is equal to or greater than the timing period of the down timer, the underwater acoustic communication network enters the restart phase, the receiving node Sink enters the restart state, and enters T3.2; when the receiving node Sink receives the Node-Reset class from the sending node Node, the underwater acoustic communication network enters the restart phase, the receiving node Sink enters the restart state, and enters T3.2; T3.1, the receiving node Sink receives control information and data from the sending node Node, updates its own Sink-Resend table and the down timer corresponding to the sending node Node, and then judges whether the information is from the last node in the sending cycle order; if not, no operation is performed and the idle waiting state is entered; if yes, the Ack confirmation information class is broadcasted at the maximum transmission power according to the Sink-Resend table of the receiving node Sink; T3.2, the sink node Sink sets the next network start time and adds it into the Sink-Reset class, and broadcasts the Sink-Reset class twice with the maximum transmission power, with an interval of T interval , and then goes to T2 at the next network start time.

2. The dynamic MAC protocol based on reception alignment according to claim 1, characterized in that, In steps S2 and T2, the initialization process of the sending node Node and the receiving node Sink is as follows: The set of all sending nodes Node in the underwater acoustic communication network is N, the number of elements in N is n, N i represents the sending node Node numbered i in the set N, 1≤i≤n, N (i-1) represents the sending node Node with the first sending order in N i ; The sending node Node sends the Node-Init class at the corresponding initial information sending moment according to the number, including the sending time stamp; the sending node Node and the receiving node Sink of the non-first sending Node-Init class will obtain the Node-Init class of the sending node Node sent first, and calculate the distance from the sending node Node according to the sending time stamp in the Node-Init class; the sending node Node of the later sending Node-Init class will attach the collected distance information to the Node-Init class of itself and send it at the maximum transmission power; the interval of sending the Node-Init class between the sending node Node with adjacent number is T MAX +T init-max ; T MAX represents the maximum propagation delay; T init-max represents the transmission time of the Node-Init class in the case of containing the distance information of all sending nodes Node except itself and itself; the receiving node Sink will calculate the distance between the nodes in the underwater acoustic communication network according to the sending time stamp and the distance information in the collected Node-Init class after N MAX T MAX +T init-max periods after the underwater acoustic communication network is started, determine the sending order of the sending node Node and the sending moment of N i , the data sending power and the receiving signal-to-noise ratio threshold value, add the above information into the Sink-Init class and broadcast it at the maximum transmission power; where N i The initial information transmission time point calculation method is as follows: T init-send-i = (i-1) x (T MAX + T init-max ) wherein T init-send-i represents the initial information sending time of N i represents the transmission time of the Node-Init class in the case of containing distance information from all sending nodes Node except the self node init-max to the self node wherein the distance d is calculated as follows: d = (T now -T init -T send ) x v where T now is the current time, T init is the transmission time of the Node-Init class, T send is the sending timestamp, and v is the speed of sound. Wherein, the receiving node Sink selects the sending order method as follows: The spatial distribution of all sending nodes Node and receiving nodes Sink in the network is abstracted into a planar graph, all sending nodes Node and receiving nodes Sink are abstracted as points on the planar graph G; N i and N (i-1) correspond to points i and (i-1) on the planar graph G; if N (i-1) no data is sent, then N i the time that can be sent in advance is recorded as W (i-1)i , W (i-1)i is abstracted as the weight of the directed edge E (i-1)i between point i and point (i-1) in the planar graph, W (i-1)i is calculated as follows: where d (i-1)R represents N (i-1) the distance to the receiving node Sink, d iR represents N i the distance to the receiving node Sink, d (i-1)i represents N (i-1) and N i the distance between, T Data is the transmission time of the data; Under this planar graph, the depth-first search is used to find the ring with the maximum weight value; the order of the nodes passed through in the ring is the network sending order; in the ring, the sending node Node with the smallest node number is set as the first sending node in the sending cycle order; After the sink node Sink selects the sending order, the sink node Sink selects the sending time for N i The method for selecting the sending time is as follows: wherein d (i-1)R represents N (i-1) the distance to the receiving node Sink, d iR represents N i the distance to the receiving node Sink, T send-i represents N i the sending time of N send-(i-1) represents N (i-1) the sending time of N Ctrl is the transmission time of the control information type, T Protect is the protection time, T Data is the transmission time of the data, and the sending time of the first sending node in the sending cycle sequence is set to 0; The receiving node Sink is N i Selecting the data transmission power P Data The method is as follows: P Data = P MAX - SNR init + SNR threshold-sink + SNR tolerant where SNR init represents the signal-to-noise ratio of the receiving node Sink receiving the Node-Init class from the sending node Node, SNR threshold-sink represents the signal-to-noise ratio threshold of the receiving node Sink receiving any information, SNR tolerant represents the fault-tolerant signal-to-noise ratio; The receiving node Sink is N i The receiving signal-to-noise ratio threshold value is selected as follows: N (i-x) indicated as N i The first sending node Node found along the sending order that does not cause data interference to N i , where 1≤x≤n; the receiving node Sink selects the sending order for N i The first sending node Node found along the sending order that does not cause data interference to N (i-x) , N (i-x) The condition that N i does not cause data interference to N (i-1)-Ctrl-i-min t (i-x)-disturb-i-max Wherein: t (i-x)-disturb-i-max = t (i-x)i + T Ctrl + T Data where t (i-1)-Ctrl-i-min denotes the time of arrival of the control information class at N (i-1) where t i denotes the time of arrival of the data at N (i-x)-disturb-i-max where t (i-x) denotes the time of end of interference at N i where t (i-x)(i-x+1) denotes the propagation time from N (i-x) to N (i-x+1) where t (i-x+1)-wait denotes the time that the sending node N (i-x+1) has to wait after receiving the information from N (i-x) ; T Ctrl is the transmission time of the control information class; T Data is the transmission time of the data; d (i-x)r denotes the distance from N (i-x) to the receiving node Sink; d (i-x+1)R denotes the distance from N (i-x+1) to the receiving node Sink; Thus the receiving node Sink is N i The receiving signal-to-noise ratio threshold is selected as: SNR threshold-i = SNR Sum-disturb-i + SNR tolerant where SNR threshold-i represents the Sink for N i selecting a receive signal-to-noise ratio threshold, SNR m-disturb-i represents N m generated by N i generated by N Sum-disturb-i represents the sum of the signal-to-noise ratio interference generated by N i generated by N 3. The dynamic MAC protocol based on reception alignment according to claim 1, characterized in that, In step S3.1, the delay time T1 is calculated as follows: The set of all sending nodes Node in the underwater acoustic communication network is N, the number of elements in N is n, N i represents the sending node Node with the number i in the set N, N (i-1) represents the sending node Node with the number i in the set N, N i represents the sending node Node with the first sending order in the set N; wherein, d (i-1)R represents the distance from the set N (i-1) to the receiving node Sink; d iR represents the distance from the set N i to the receiving node Sink; t (i-1)i represents the propagation time between the set N (i-1) and the set N i ; T Data is the transmission time of data; and v is the sound speed.

4. The dynamic MAC protocol based on reception alignment according to claim 1, characterized in that, In step S3.2, the power P1 of the sending control information class and the power P2 of the sending data of the sending node Node are calculated as follows: P1 = P MAX P2 = P Data where P MAX represents the maximum transmission power, the data transmission power P Data of the own node is obtained by the sending node Node in the Sink-Init class received in S2.

5. The dynamic MAC protocol based on reception alignment according to claim 1, characterized in that, In steps S3.1, S3.2, S3.3 and T3.1, the updating method of the Node-Resend resend table of the sending node Node itself and the Sink-Resend resend table of the receiving node Sink itself is as follows: For the Node-Resend resend table of the sending node Node itself, the sending node Node records the packet sequence number and the sending time every time it sends new data and stores it in the Node-Resend resend table; when the sending node Node receives the Ack confirmation information class from the Sink, it will attach this information to the control information class to be sent next time, and then update the Node-Resend resend table of itself; when the sending node Node receives the control information class from the sending node Node in the previous sending order, it obtains the Ack confirmation information part, and then updates the Node-Resend resend table of itself; the updating method of the sending node Node for the Node-Resend resend table of itself is: traversing the Node-Resend resend table, deleting the corresponding table entry in the table whose packet sequence number is less than the Ack confirmation information class or the Ack confirmation information part for the confirmation sequence number of the node; The receiving node Sink maintains a confirmation sequence number variable for each sending node Node, and the confirmation sequence number represents the packet sequence number of the next packet that the receiving node Sink expects the node to send to it; for the receiving node Sink, every time it successfully receives data, it records the node number of the sending node Node that sends the data and the packet sequence number of the data; then the receiving node Sink updates the Sink-Resend resend table of itself, and the updating method is: checking the data reception of the sending node Node in the Sink-Resend resend table, checking whether the packet sequence number is the confirmation sequence number of the sending node Node, if yes, updating the confirmation sequence number of the sending node Node to the latest one in the successfully received continuous packet sequence numbers in the table entry of the sending node Node in the Sink-Resend resend table, and deleting the table entries before the new confirmation sequence number; if not, record the packet sequence number in the table entry of the sending node Node in the Sink-Resend resend table; After the sending node Node enters the sending state, it checks the Node-Resend table of itself. If it finds that the sending node Node has received the same acknowledgement serial number for three or more times in succession and that the data represented by the acknowledgement serial number is stored in the Node-Resend table of itself, it triggers the fast retransmission mechanism, retransmits the data, updates the sending time of the data after the sending is completed, and makes the retransmission time limit twice the original value. In the case where no data triggers the fast retransmission mechanism, if it finds that the difference between the sending time of the data and the current time is equal to or greater than the retransmission time limit T of the data itself time-out , it triggers the timeout retransmission mechanism, retransmits the data, and updates the sending time of the data, making the retransmission time limit twice the original value. The first retransmission time limit is calculated as follows: first-time-out T Round T Round = n x (T Ctrl + T Data + T Protect ) Wherein, the set of all sending nodes Node in the underwater acoustic communication network is N, the number of N is n, T Round represents the total time consumed by each sending node Node to complete one control information class transmission, one data transmission and the waiting protection time in the case that all the n sending nodes Node have data to send; T Ctrl is the transmission time of the control information class, T Protect is the protection time; T Data is the transmission time of the data.

6. The dynamic MAC protocol based on reception alignment according to claim 1, characterized in that, The method for the receiving node Sink to send the Ack confirmation information class in step T3.1 is as follows: When the receiving node Sink receives the data or the No type control information class of the last node in the sending cycle sequence, it sends the Ack confirmation information class, the content of which is the confirmation sequence number of each sending node Node, and the meaning is the packet sequence number of the next data sent by the sending node Node; in the usual scenario, the receiving node Sink will only receive the data or the No type control information class of the last node in the sending cycle sequence, and then send the Ack confirmation information class; but when the underwater acoustic environment deteriorates, the risk of loss of the Ack confirmation information class increases, and the Sink can send the Ack confirmation information class when it receives the data or the No type control information class of other sending nodes Node, send more Ack confirmation information classes in a transmission cycle, and improve the anti-interference ability of the underwater acoustic communication network; When the sending node Node receives the control information class from the sending node Node in the previous sending order, the node reads the Ack confirmation information part, updates the Node-Resend retransmission table of itself, and when it is the turn of the sending node Node to send the control information class, it puts the Ack confirmation information part into the control information class and then sends it; in addition, when the sending node Node receives the Ack confirmation information class from the Sink, it updates the Node-Resend retransmission table of itself, and ignores the Ack confirmation information part in the control information class from the sending node Node in the previous sending order, when it is the turn of the sending node Node to send the control information class, it puts the content of the Ack confirmation information class into the control information class and then sends it.

7. A dynamic MAC protocol based on reception alignment according to claim 5, characterized in that, The method for updating the timing moment of the sending timer of the sending node Node in step S3.2 is as follows: When the current time is equal to or greater than the timing moment of the sending timer, the sending node Node enters the sending state; when the sending node Node receives the control information class from the sending node Node in the previous sending order before entering the sending state, it enters the sending state; when the sending state of the sending node Node ends, the sending node Node updates the timing moment of the sending timer; the timing moment of the sending timer is specified by the receiving node Sink from the Sink-Init class for the first time; the method for updating the timing moment of the timer is as follows: wherein T next-send-time represents the timing moment of the next transmission timer, T send-time represents the timing moment of the current transmission timer, the first round planned transmission timing is T send-i , T Now represents the current timing moment.

8. The dynamic MAC protocol based on reception alignment according to claim 1, characterized in that, The use method of the sending node Node for the Node-Reset class and the use method of the receiving node Sink for the Sink-Reset class in steps S3.4, S3.5 and T3.2 are as follows: For a sending node Node newly joining or exiting the underwater acoustic communication network, a Node-Reset class is broadcast to the underwater acoustic communication network, the rest of the sending nodes Node hear and transfer into a restart state from a current state after hearing the Node-Reset class, and forward the Node-Reset class; a receiving node Sink hears the Node-Reset class and transfers into a restart state from a current state, and broadcasts a Sink-Reset class twice after 2 times of maximum propagation delay; the interval T of the twice broadcasting interval The calculation is as follows: T interval = T Ctrl + T Data + T Protect wherein T Ctrl is the transmission time of the control information class, T Protect is the guard time; T Data is the transmission time of the data, after 2 broadcasts all sending nodes Node receive Sink-Reset class from the receiving node Sink, which guarantees that all nodes in the underwater acoustic communication network enter the initialization state at the next network start time specified in the Sink-Reset class, and go to S2. where the next network start time is: T Restart = T interval + 2 · T MAX .

9. The dynamic MAC protocol based on reception alignment according to claim 1, characterized in that, The use method of the receiving node Sink for the down-time timer in step T3.2 is as follows: The receiving node Sink maintains a down-time timer for each sending node Node, when the period of time in which it does not receive the information of a sending node Node within 10 min is equal to or greater than the timing period of the down-time timer, it is judged that the sending node Node is invalid, the topology of the underwater acoustic communication network changes, and the underwater acoustic communication network enters the restart stage, broadcasts the Sink-Reset class twice, and notifies the next network starting moment of the underwater acoustic communication network; when the information of a sending node Node is received within 10 min, the down-time timer of the corresponding sending node Node is restarted.

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