An Underwater Acoustic Network Media Access Control Method Based on Recombinant Time Slot Directional Reception

Abstract

A media access control method for an underwater acoustic network based on reorganized time slot directional reception. When multiple underwater nodes simultaneously send DATA data packets to the sink node, it is determined whether the DATA data packet can arrive at the time slot start point of the reorganized time slot of the sink node. If so, it is sent; otherwise, it is sent after a backoff period. After the DATA data packet arrives at the sink node, the sink node determines the position of the sending node based on the DATA data packet and receives the DATA information packet in the DATA data packet through the directional reception method. A media access control method for an underwater acoustic network based on reorganized time slot directional reception can effectively improve the transmission throughput. After a successful channel reservation, the receiving node performs backoff and actively waits for all underwater nodes that need to send to finish sending the DATA data packet, which can effectively reduce the collision of DATA data packets at the sink node. Using the directional reception technology, it is applicable to large-scale data collection-type underwater acoustic sensor networks.

Description

Technical Field

[0001] The present invention belongs to the field of communication technologies, and particularly relates to an underwater acoustic network media access control method based on reorganized time slot directional reception. Background Art

[0002] In recent years, the development of marine resources has been increasingly emphasized by countries around the world. Monitoring marine hydrographic data information including temperature, salinity, etc. is extremely necessary for developing marine resources and safeguarding the security of sea frontiers. The traditional monitoring method is to deploy sensors in seawater to collect data. Every once in a while, the sensors are salvaged, and then the data recorded in the sensors is read and processed. This method has many drawbacks: real-time monitoring of data cannot be achieved; when problems occur in the sensor devices, they cannot be discovered and repaired as soon as possible. To make up for the deficiencies of the traditional monitoring method, an underwater wireless sensor network (UWSNs) has been proposed in the prior art. The data link layer protocol of the underwater wireless sensor network is mainly a media access control (MAC) protocol based on a contention method. The underwater wireless sensor network can transmit the underwater data collected by the sensor nodes to the shore-based control center in real time, realizing the real-time and reliable transmission of underwater observation data, and plays an indispensable role in monitoring hydrographic information and developing marine resources. However, most of the existing underwater acoustic MAC protocols cannot achieve spatial multiplexing of underwater acoustic communication, resulting in waste of underwater acoustic channel resources. Moreover, due to the characteristics of long propagation delay, high bit error rate, and limited transmission bandwidth of the underwater acoustic channel, the existing contention-based MAC protocols are only applicable to point-to-point node communication, and are not applicable to the underwater information collection scenario where multiple nodes need to send a large amount of information to the same target node at the same time. When multiple nodes in the underwater acoustic sensor network need to send data to the sink node, multiple data packets will collide at the sink node, resulting in channel reservation failure and reducing the data reception efficiency. Summary of the Invention

[0003] To solve the problem that the MAC protocol of the underwater acoustic sensor network in the prior art is not applicable to the scenario of multiple sending nodes and a single receiving node, an underwater acoustic network media access control method based on reorganized time slot directional reception is proposed. This method divides reorganized time slots for nodes and uses directional reception to improve the utilization rate in terms of time and space, and realizes stable underwater acoustic communication with space-time multiplexing.

[0004] An underwater acoustic network media access control method based on reorganized time slot directional reception includes:

[0005] Step 1, n underwater nodes i are acoustically connected to the sink node, where i is the serial number of the underwater node, i = {1, 2, 3,..., n}, and n is the number of underwater nodes;

[0006] Step 2: Synchronize the time of underwater node i and the sink node. The underwater node i broadcasts its own location information, and the sink node records the location information of n underwater nodes. Set the time slot length of each node as T slot , and the sink node only receives information at the start point of T slot . Set K consecutive time slots T slot to form a reorganized time slot, where 1 ≤ K < n and K is an integer;

[0007] Step 3: Set the transmission time for the underwater node i to send a DATA data packet to the sink node according to the distance between the underwater node i and the sink node. This transmission time enables the DATA data packet to reach the sink node at the start point of a certain time slot within the reorganized time slot;

[0008] Step 4: The sink node directionally receives the DATA data packet sent by the underwater node i according to the location information of the underwater node i.

[0009] Beneficial effects

[0010] For a media access control method for an underwater acoustic network based on reorganized time slot directional reception in this application, when multiple underwater nodes simultaneously send DATA data packets to the sink node, it is determined whether the DATA data packet can reach the sink node at the start point of the time slot of the reorganized time slot of the sink node. If so, it is sent; if not, it is sent after a period of backoff, ensuring that the DATA data packet reaches the start point of the time slot within the reorganized time slot of the sink node. After the DATA data packet reaches the sink node, the sink node determines the location of the sending node according to the DATA data packet, rotates the vector hydrophone to receive the DATA information packet in the DATA data packet, and after the sink node receives the DATA data packet, it sends an acknowledgment message to the sending node. A media access control method for an underwater acoustic network based on reorganized time slot directional reception in this application can effectively improve the transmission throughput. After a successful channel reservation, the receiving node performs backoff and actively waits for all underwater nodes that need to send to finish sending DATA data packets, which can effectively reduce the collision of DATA data packets at the sink node. Using the directional reception technology, it is applicable to large-scale data collection type underwater acoustic sensor networks. Description of the drawings

[0011] Figure 1 It is a schematic flowchart of the specific implementation manner of a media access control method for an underwater acoustic network based on reorganized time slot directional reception in this application;

[0012] Figure 2 It is a topological model of an underwater acoustic data collection network for the specific implementation manner of a media access control method for an underwater acoustic network based on reorganized time slot directional reception in this application;

[0013] Figure 3Specific implementation manner network throughput comparison diagram a of an underwater acoustic network media access control method based on reorganized slot directional reception of the present application;

[0014] Figure 4 Specific implementation manner network throughput comparison diagram b of an underwater acoustic network media access control method based on reorganized slot directional reception of the present application;

[0015] Figure 5 Specific implementation manner network packet sending success rate comparison diagram of an underwater acoustic network media access control method based on reorganized slot directional reception of the present application;

[0016] Figure 6 Specific implementation manner end - to - end delay comparison diagram of an underwater acoustic network media access control method based on reorganized slot directional reception of the present application;

[0017] Figure 7 Specific implementation manner network total simulation time comparison diagram of an underwater acoustic network media access control method based on reorganized slot directional reception of the present application;

[0018] Figure 8 Specific implementation manner schematic diagram of the vector directional reception method of an underwater acoustic network media access control method based on reorganized slot directional reception of the present application. Specific implementation manner

[0019] Combined with Figures 1 to 8 Describe this implementation manner. An underwater acoustic network media access control method based on reorganized slot directional reception includes:

[0020] Step 1: n underwater nodes i are acoustically connected to the sink node, where i is the serial number of the underwater node, i = {1, 2, 3,..., n}, and n is the number of underwater nodes;

[0021] Step 2: Synchronize the time of underwater node i and the sink node. Underwater node i broadcasts its own location information, and the sink node records the location information of n underwater nodes; set the slot length of each node to T slot , the sink node only receives information at the start of T slot , set K consecutive slots T slot to form a reorganized slot, 1 ≤ K < n, and K is an integer;

[0022] Step 3: According to the distance between underwater node i and the sink node, set the sending time for underwater node i to send a DATA data packet to the sink node, and this sending time enables the DATA data packet to reach the sink node at the start of a certain slot within the reorganized slot;

[0023] Step 4: The sink node directionally receives the DATA data packet sent by the underwater node i according to the location information of the underwater node i.

[0024] Specifically, as Figures 1 to 2 shown, first, network initialization is performed to establish the network node topology information. Connect n underwater nodes and 1 sink node through underwater acoustic connections, where the positions of all nodes are fixed, forming a centralized network. i is the serial number of the underwater node, i = {1, 2, 3,..., n}, and n is the number of underwater nodes. Secondly, network parameters are set. All nodes use OFDM modulation to transmit information, with a bandwidth of 6 kHz and a communication rate of 1220 bps. The time synchronization is achieved among all nodes, and T slot is set as the slot length. Each node will start receiving the DATA data packet only at multiples of T slot . Set K consecutive time slots T slot to form a reorganized time slot. The underwater node i broadcasts its own location information, and the sink node records the location information of n underwater nodes. Each node receives information at the starting point of each time slot within the reorganized time slot. The underwater node i sends the DATA data packet to the sink node so that the DATA data packet can reach the sink node at the starting point of a certain time slot within the reorganized time slot. Data reception: The sink node directionally receives the DATA data packet sent by the underwater node i.

[0025] In Step 3, the method for setting the sending time when the underwater node i sends the DATA data packet to the sink node is as follows:

[0026] Obtain the initial time t i when the underwater node i needs to send the DATA data packet; judge whether the DATA data packet sent by the underwater node i at the initial time t i can reach the sink node at the starting point of a certain time slot within the reorganized time slot of the sink node. If so, the underwater node i sends the DATA data packet to the sink node at the initial time t i . If not, calculate the sending time T plansend_UNDER-i , and the underwater node i backs off to send the DATA data packet to the sink node at the moment of T plansend_UNDER-i ;

[0027] The calculation formula for the sending time T plansend_UNDER-i is as follows:

[0028]

[0029] where m i is a randomly obtained positive integer, 0 ≤ m i ≤ K - 1, T dealy_SINK-i is the propagation delay of the underwater node i, S i is the distance between the underwater node i and the sink node, v is the speed of sound propagation in water, is for Round up.

[0030] Specifically, underwater node i needs to send a DATA data packet at time t i to determine whether the DATA data packet sent by underwater node i can reach the starting point of the sink node's time slot at time t i If it can, the DATA data packet is sent at time t i If not, underwater node i backs off to transmission time T plansend_UNDER-i and then sends the DATA data packet to the sink node; calculate the propagation delay T dealy_SINK-i The propagation delay of each underwater node is the ratio of the distance between the underwater node and the sink node to the speed of sound in water: According to the propagation delay T dealy_SINK-i and time slot T slot calculate the transmission time T plansend_UNDER-i , and the DATA data packet sent by underwater node i at time T plansend_UNDER-i can reach the starting point of a certain time slot within the recombined time slot of the sink node;

[0031] The DATA data packet includes a DATA data packet header and a DATA information packet. The method for the sink node to directionally receive the DATA data packet sent by underwater node i is as follows: The sink node obtains the sending node serial number according to the received DATA data packet header of underwater node i; determines the position information of underwater node i according to the serial number of underwater node i, and directionally receives the DATA information packet sent by underwater node i according to the position information of underwater node i; The method for directionally receiving the DATA information packet sent by an underwater node according to the sending node position is as follows: Rotate the vector hydrophone according to the sending node position, and point the maximum directivity point of the vector hydrophone to the sending node position. The vector hydrophone is used to receive the DATA information packet.

[0032] Specifically, when the sink node receives the DATA data packet sent by underwater node i, it obtains the sending node position by analyzing the DATA data packet header; when receiving the signal of the underwater node, the directivity 0° of the vector hydrophone points to the position of underwater node i to receive the DATA information packet sent by underwater node i. As Figure 8 shown, the directivity 0° signal of the vector hydrophone has the best reception effect; when the DATA data packets sent by two underwater nodes on both sides of the sink node reach the sink node at the same time, the directivity 0° of the vector hydrophone points to one of the underwater nodes to receive the DATA information packet it sends, and the interference caused by the DATA data packet sent by the other underwater node will be reduced by the directional reception method. After receiving the DATA information packet of one underwater node, rotate the directivity 0° of the vector hydrophone to point to the other underwater node to receive the DATA information packet sent by the other underwater node;

[0033] The sink node determines whether it has received the information sent by underwater node i. If so, it sends an ACK confirmation packet to underwater node i; otherwise, it sends a NACK confirmation packet to underwater node i.

[0034] A media access control method for an underwater acoustic network based on recombined time slot directional reception further includes: Step Five: The sink node sends confirmation information to underwater node i according to the received DATA data packet;

[0035] The method for the sink node to send confirmation information to underwater node i according to the received DATA data packet is: The sink node determines whether it has received the information sent by underwater node i according to the obtained sending node serial number. If so, it sends an ACK confirmation packet to underwater node i; otherwise, it sends a NACK confirmation packet to underwater node i.

[0036] The method for the sink node to determine whether it has received the information sent by underwater node i according to the obtained sending node serial number is: After the sink node receives a DATA data packet sent by a certain underwater node, it starts silent timing. If the sink node receives a DATA data packet sent by another underwater node before the end of the silent timing, it restarts the silent timing until the silent timing duration reaches Δt, and records the moment when the silent timing duration reaches Δt as t e ;

[0037] After the silent timing duration reaches Δt, the sink node determines whether it has successfully demodulated the DATA data packet sent by underwater node i according to the obtained sending node serial number. If so, it sends an ACK confirmation packet to underwater node i at time T plansend_SINK-i ; otherwise, it sends a NACK confirmation packet to underwater node i at time T plansend_SINK-i ;

[0038] T plansend_SINK-i The calculation method of is:

[0039] Specifically, the silent timing and sending ACK or NACK confirmation packets can prevent missing DATA data packets sent by underwater nodes; calculate the time for the sink node to send ACK or NACK confirmation packets to underwater nodes so that the ACK or NACK confirmation packets arrive at the time slot start point of the underwater nodes. Specific embodiment:

[0041] As Figures 1 to 2 shown, 4 underwater nodes, underwater node 1, underwater node 2, underwater node 3 and underwater node 4 are respectively connected to 1 sink node through underwater acoustic connections, where all node positions are fixed, forming a centralized network; set network parameters, all nodes use OFDM modulation to transmit information, the bandwidth is 6 kHz, the communication rate is 1220 bps, and the time between each node is synchronized, Tslot is the slot length, and each node will only start receiving DATA packets at multiples of T slot . Set 3 consecutive time slots T slot to form a recombined time slot; assume that underwater node 1, underwater node 2, underwater node 3, and underwater node 4 need to send DATA packets at times t1, t2, t3, and t4 respectively; after judgment, it is found that the DATA packets sent by underwater node 1, underwater node 2, underwater node 3, and underwater node 4 at times t1, t2, t3, and t4 cannot reach the starting point of a certain time slot of the recombined time slot at the sink node; according to the distances S1, S2, S3, and S4 between the sink node and the 4 underwater nodes, calculate the propagation delays T dealy_SINK-1 、T dealy_SINK-2 、T dealy_SINK-3 and T dealy_SINK-4 ;

[0042]

[0043] According to the propagation delays T dealy_SINK-1 、T dealy_SINK-2 、T dealy_SINK-3 and T dealy_SINK-4 and the times t1, t2, t3, and t4 when the 4 underwater nodes all need to send information, calculate the transmission times T plansend_UNDER-1 、T plansend_UNDER-2 、T plansend_UNDER-3 and T plansend_UNDER-4 ;

[0044]

[0045] where m1, m2, m3, m4 are random integers uniformly distributed in [0, K - 1], 0 ≤ m1 ≤ K - 1, 0 ≤ m2 ≤ K - 1, 0 ≤ m3 ≤ K - 1, 0 ≤ m4 ≤ K - 1;

[0046] As Figure 1 shown, underwater node 1 sends a DATA packet to the sink node at time T plansend_UNDER-1 , underwater node 2 sends a DATA packet to the sink node at time T plansend_UNDER-2 , underwater node 3 sends a DATA packet to the sink node at time T plansend_UNDER-3 , and underwater node 4 sends a DATA packet to the sink node at time T plansend_UNDER-4 ;

[0047] The DATA data packet includes a DATA data packet header and a DATA information packet. The sink node first receives the DATA data packet sent by underwater node 2, determines the location of the sending node by analyzing the DATA data packet header, and the directivity of the rotational vector hydrophone points to the location of underwater node 2 at 0° to receive the DATA information packet sent by underwater node 2. After the rotational vector hydrophone receives the DATA information packet sent by underwater node 2, it starts silent timing. Before the silent timing ends, it receives the DATA data packet sent by underwater node 4, and the directivity of the rotational vector hydrophone points to the location of underwater node 4 at 0° to receive the DATA information packet sent by underwater node 4. Similarly, it receives the DATA data packets sent by underwater node 1 and underwater node 3; in the packet time slot, the DATA data packets sent by underwater node 1 and underwater node 3 overlap. When receiving the signal of underwater node 1, the maximum directivity point of the electronic rotational vector hydrophone points to the location of sending node 1. At this time, since underwater node 3 and underwater node 1 are on both sides of the sink node, as Figure 8 shown, the directivity of the vector hydrophone points to underwater node 1 at 0° and to underwater node 3 at 180°. The interference caused by the DATA data packet sent by underwater node 3 to the DATA data packet sent by underwater node 1 will be reduced by the vector hydrophone's directional reception method;

[0048] After the sink node finishes receiving the DATA data packet sent by underwater node 3, the silent timing duration reaches Δt, and the moment when the silent timing duration reaches Δt is recorded as t e , the sink node determines that it has received the DATA data packets sent by underwater node 1, underwater node 2, underwater node 3, and underwater node 4, and sends ACK confirmation packets to underwater node 1, underwater node 2, underwater node 3, and underwater node 4. The times for sending the ACK confirmation packets are:

[0049]

[0050] Underwater node 1, underwater node 2, underwater node 3, and underwater node 4 respectively receive the ACK confirmation packets sent by the sink node at the starting points of their respective time slots.

Claims

1. An underwater acoustic network media access control method based on recombinant time slot directional reception, characterized in that: including Step 1: n underwater nodes i are acoustically connected to the sink node, where i is the serial number of the underwater node, i = {1, 2, 3,..., n}, and n is the number of underwater nodes; Step 2: Synchronize the time of underwater node i and the sink node. The underwater node i broadcasts its own location information, and the sink node records the location information of n underwater nodes i. Set the slot length of each node to T slot , and the sink node only receives information at the start of T slot . Set K consecutive time slots T slot to form a reorganized time slot, where 1 ≤ K < n and K is an integer; Step 3: According to the distance between the underwater node i and the sink node, set the transmission time for the underwater node i to send the DATA data packet to the sink node, and this transmission time enables the DATA data packet to reach the sink node at the start of a certain time slot within the recombination time slot; Step 4: The sink node directionally receives the DATA data packet sent by the underwater node i according to the position information of the underwater node i; In Step 3, the method for setting the transmission time for the underwater node i to send the DATA data packet to the sink node is as follows: Obtain the initial time t when the underwater node i needs to send a DATA data packet i ; Determine whether the underwater node i can reach a certain time slot start point within the recombination time slot of the sink node when sending the DATA data packet at the initial time t i If so, the underwater node i sends the DATA data packet to the sink node at the initial time t i If not, calculate the transmission time T plansend_UNDER-i , and the underwater node i backs off to T plansend_UNDER-i and sends the DATA data packet to the sink node at that moment; Transmission time T plansend_UNDER-i The calculation formula is as follows: where m i is a randomly obtained positive integer, 0 ≤ m i ≤ K - 1, T dealy_SINK-i is the propagation delay of underwater node i, S i is the distance between underwater node i and the sink node obtained according to the location information of underwater node i, v is the speed of sound propagation in water, is for rounding up.

2. The media access control method for an underwater acoustic network based on reorganized time slot directional reception according to claim 1, wherein: The DATA data packet includes a DATA data packet header and a DATA information packet; the method for the sink node to directionally receive the DATA data packet sent by the underwater node i is: the sink node obtains the serial number of the underwater node i according to the received DATA data packet header of the underwater node i; and directionally receives the DATA information packet sent by the underwater node i according to the position information of the underwater node i.

3. The MAC method for an underwater acoustic network based on reorganized time slot directional reception according to claim 2, wherein: The method for directionally receiving the DATA information packet sent by the underwater node according to the position information of the underwater node i is: according to the position information of the underwater node i, electronically rotate the vector hydrophone, and point the maximum directivity point of the vector hydrophone to the underwater node i, and the vector hydrophone is used to receive the DATA information packet.

4. The media access control method for an underwater acoustic network based on reorganized time slot directional reception according to claim 3, characterized in that: This method further includes: Step 5: The sink node sends an acknowledgment message to the underwater node i according to the received DATA data packet.

5. The media access control method for an underwater acoustic network based on recombinant time slot directional reception according to claim 4, wherein: The method for the sink node to send an acknowledgment message to the underwater node i according to the received DATA data packet is: the sink node determines whether it has received the information sent by the underwater node i according to the obtained serial number of the sending node. If so, it sends an ACK acknowledgment packet to the underwater node i; if not, it sends a NACK acknowledgment packet to the underwater node i.

6. The media access control method for an underwater acoustic network based on reorganized time slot directional reception according to claim 5, wherein: The method for the sink node to determine whether to receive the information sent by the underwater node i according to the obtained sending node number is as follows: When the sink node receives a DATA data packet sent by a certain underwater node, it starts silent timing. If the sink node receives a DATA data packet sent by other underwater nodes before the end of the silent timing, it starts silent timing again until the silent timing duration reaches Δt, and the moment when the silent timing duration reaches Δt is denoted as t e ; After the silent timing duration reaches Δt, the aggregation node determines whether to receive the DATA packet sent by the underwater node i according to the obtained sending node serial number. If so, it sends an ACK confirmation packet to the underwater node i at time T plansend_SINK-i ; otherwise, it sends a NACK confirmation packet to the underwater node i at time T plansend_SINK-i ; T plansend_SINK-i The calculation method is as follows:

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