CN105307274A - Data receiving and sending method capable of making full use of time resource in underwater sensor network - Google Patents

Abstract

The present invention relates to a data sending and receiving method that makes full use of time resources in an underwater sensor network. There are two pairs of nodes ready for data transmission, respectively a master node pair and a secondary node pair. The data sending and receiving methods of the two pairs of nodes are as follows: The sending node and the receiving node use the RTS-CTS handshake process when transmitting data, and the secondary node pair will also receive the RTS message. According to the location information of the primary node pair in the message, the time occupancy of each node is obtained, and the prohibition is calculated. The time period for the secondary node to send the message should reasonably arrange its own sending time to avoid message conflicts. The present invention makes full use of idle time resources, and under the condition of ensuring no interference to the sending and receiving of messages of other nodes, the nodes in the network can flexibly arrange the sending time of messages according to the position information of each node, so as to improve the efficiency of time resources. utilization rate.

Description

A data sending and receiving method that makes full use of time resources in underwater sensor networks

technical field

The invention belongs to the technical field of underwater sensor networks and relates to a data transmission method.

Background technique

The underwater sensor network is a powerful tool for exploring and developing the ocean at present, and has been widely used in many fields, such as marine environment monitoring, oil resource development, military reconnaissance and so on. The nodes in the underwater sensor network use acoustic signals for data transmission, which face the disadvantages of slow signal propagation, large attenuation, narrow bandwidth, etc., and the deployment of underwater sensor networks is more complicated, and sensor nodes are also limited by energy consumption. In order to ensure that nodes can receive data without conflicts, the existing data sending and receiving process requires nodes that monitor other nodes to send data to enter a back-off state and postpone their own sending process. But in the actual situation, the receiving time of the message only lasts for a few seconds, and the message is transmitted in the channel for the rest of the time, and has not reached the node. Therefore, other nodes can still send data during this idle time, and the current sending and receiving process does not make full use of these times, resulting in a low time utilization rate of the entire network.

Contents of the invention

Aiming at the shortcomings of the current data sending and receiving process in the existing underwater sensor network, the present invention improves on the basis of the RTS-CTS protocol, considers the relative positions of the sending and receiving nodes, and designs a scheme that allows two pairs of nodes to simultaneously send and receive data , the technical scheme of the present invention is as follows:

A data sending and receiving method that makes full use of time resources in an underwater sensor network. Each node sends four types of messages during the communication process, which are RTS, CTS, DATA and ACK messages, and RTS, CTS and ACK messages. The format is fixed, and the duration of these three types of messages is assumed to be equal, all of which are T. The _RTS message contains the coordinate information of the sending node and the receiving node. In the lower sensor network, there are two pairs of nodes ready for data transmission, namely the primary node pair and the secondary node pair. Each pair of nodes can be divided into a sending node and a receiving node. The sending node needs to transmit its own data to the receiving node. , then the data sending and receiving methods of the two pairs of nodes ready for data transmission are:

(1) The position of each node in the underwater sensor network is fixed, and all nodes know their own position coordinates, and the transmission delay between each node is obtained;

(2) The underwater sensor network is synchronized throughout the network, the clocks of all nodes are consistent, and the coverage of the signals sent by each sensor node is the same;

(3) The sending node and the receiving node use the RTS-CTS handshake process when transmitting data. The master node is centered. The sending node first sends an RTS message to request transmission. After receiving the RTS message, the receiving node replies a CTS message and prepares to receive data. ; After that, the sending node puts the data to be sent in the DATA message for sending, and the receiving node that receives the DATA message replies with ACK to confirm the transmission process; at the same time, the secondary node pair will also receive the RTS message, According to the position information of the primary node pair in the message, the time occupation of each node is obtained, and the time period for which the secondary node is prohibited from sending messages is calculated. According to the time period for which the secondary node is prohibited from sending, the secondary node pair reasonably arranges their own sending time. to avoid message collisions.

The present invention makes full use of idle time resources, and under the condition of ensuring no interference to the sending and receiving of messages of other nodes, the nodes in the network can flexibly arrange the sending time of messages according to the position information of each node, so as to improve the efficiency of time resources. utilization rate.

Description of drawings

Figure 1. Time resources are not fully utilized in existing transceiver solutions

Figure 2. The relative positional relationship between the primary node pair and the secondary node pair, (1)-(7) are each a relative positional relationship diagram

Figure 3. The communication between the primary node pair (A, B) occupies four time periods of the secondary node pair (C, D) respectively

Figure 4. Example of a new scheme

detailed description

The scheme designed by the present invention requires the nodes to send four types of messages during the communication process, namely RTS, CTS, DATA and ACK messages. Since the message formats of the RTS, CTS and ACK messages are fixed, the durations of these three types of messages in the underwater channel are also fixed, and it can be assumed that the durations of these three types of messages are equal, T. The RTS message contains information such as the coordinate information of the sending node and the receiving node, and the duration T _DATA of the DATA message during the current round of sending.

The method involved in the present invention will now be described by taking nodes A and B as the primary node pair and nodes C and D as the secondary nodes as an example. In the primary node pair, node A is the sending node, and node B is the receiving node; in the secondary node pair, node C is the sending node, and node D is the receiving node.

In wireless communication, the area covered by a wireless signal forms a collision domain. In the conflict domain, the signal strength is relatively high and can be received by other nodes, which will affect the sending and receiving of other signals; while outside the conflict domain, the signal strength is small, so it can be considered that the signal of the sending node will not interfere with the reception of other signals. The collision domain can be approximated as a sphere in three-dimensional space. The collision domain can be simplified as a circle in a two-dimensional plane. The analysis process in three-dimensional space is similar to that in two-dimensional space, and the following will be explained with a two-dimensional plane. As shown in FIG. 1 , it is assumed that the conflict domains of the nodes involved in the present invention have the same size, which are all represented by a circle with a radius R.

The collision domain of node A and node B divides the entire two-dimensional plane into four parts, and node C is in the collision domain of node A, so it can receive the RTS message sent by node A. From which node C can obtain the addresses of sending node A and receiving node B and the duration t _DATA of the DATA message, so as to know the entire process of data transmission between A and B, that is, the time when each message starts to be sent and the time when the message arrives time. The specific moment can be represented by t. The subscript of t consists of three parts. The first part indicates the sending node and the receiving node of the message. The second part indicates the moment when the message arrives at which node. The third part indicates the type of message. There are RTS, CTS, DATA, ACK four types. Taking the DATA message sent by the sending node A to the receiving node B as an example, the time when the DATA message arrives at the node B can be expressed as t _AB,B,DATA . The sending process between nodes A and B has been determined, and the transition time between sending and receiving nodes is also fixed, so these times will not change. If nodes C and D want to make full use of the idle time between A and B, they must avoid these determined time periods, otherwise message conflicts will occur, which will affect the communication performance of the network.

Nodes C and D are at different locations, and the signal between C and D may interfere with A and B. As shown in Figure 2, there are several situations as follows:

(1) A and C nodes will affect each other

(2) A, C nodes and B, C nodes influence each other

(3) A, C nodes and A, D nodes will affect each other

(4) A, C nodes, B, C nodes, B, D nodes will all affect each other

(5) A, C nodes, B, C nodes, A, D nodes will all affect each other

(6) A, C nodes, A, D nodes, B, D nodes will all affect each other

(7) A, C nodes, A, D nodes, B, C nodes and B, D nodes will all affect each other

When nodes C and D are in different locations, the factors to be considered in utilizing the idle time between nodes A and B are also slightly different. When nodes A, C, nodes A, D, nodes B, C, and nodes B, D all affect each other, the situation is the most complicated, and this situation will be further explained now. As shown in Figure 3, the messages sent between nodes A and B will reach nodes C and D, so four time periods have been occupied on the time axis of nodes C and D respectively; similarly, nodes C, Messages sent between D will also reach nodes A and B. In order to avoid message conflicts, node C needs to obtain the occupied time period of each node, as shown in Table 1. The RTS message sent by node A will not conflict with the message between C and D, so it is not listed in the table.

Table 1. The time period each node has been occupied

point time period 1 time period 2 time period 3 A(t _AB,A,CTS ,t _AB,A,CTS +T) (t _BA,A,ACK ,t _BA,A,ACK +T) B(t _AB,B,DATA ,t _AB,B,DATA +T _DATA ) C(t _BA,C,CTS ,t _BA,C,CTS +T) (t _AB,C,DATA ,t _AB,C,DATA +T _DATA ) (t _BA,C,ACK ,t _BA,C,ACK +T) D(t _BA,D,CTS ,t _BA,D,CTS +T) (t _AB,D,DATA ,t _AB,D,DATA +T _DATA ) (t _BA,D,ACK ,t _BA,D,ACK +T)

In wireless communication, if multiple signals arrive at a certain node at the same time, the waveforms at the node will be superimposed, so that any signal cannot be received correctly. Therefore, if node C and node D want to use the idle time during the transmission of nodes A and B without affecting their normal communication, the time for the signal sent by node C to reach nodes A and B cannot be used by nodes A and B for reception The time of the message coincides, and the time when the signal sent by node C arrives at node D cannot coincide with the time when the signal sent by nodes A and B arrives at node D.

On the basis of knowing the information in Table 1, according to the transmission delay between nodes, the time period during which node C is prohibited from sending messages can be calculated, as shown in Table 2. Take node B receiving the DATA message from node A as an example, from the time t _{AB, B, DATA} to the time t _{AB, B, DATA} + T _DATA , node B will receive the DATA message from node A, if the message from node C Also arriving at node B from time t _{AB, B, DATA} to time t _{AB, B, DATA} + T _DATA will cause a conflict. Therefore, from time t _AB,B,DATA -τ _BC to time t _AB,B,DATA +T _DATA -τ _BC , node C should be prohibited from sending messages, where τ _BC is the transmission delay between nodes B and C. The calculation method of other time periods during which node C is prohibited from sending messages is similar to this. Similarly, the time period during which node D is prohibited from sending messages can also be calculated.

Table 2. Periods during which node C and node D are prohibited from sending

After obtaining the information in Table 2, node C preparing to transmit data needs to set the time t _RTS for sending RTS messages and t _DATA for sending DATA messages, and at the same time set the time for node D to send CTS messages The sending time t _CTS of the message, and at the same time put t _CTS in the RTS message and send it to node D. The settings of t _RTS , t _DATA and t _CTS cannot coincide with the time periods in Table 2.

Through the above arrangements, node C and node D can make full use of the time gap between node A and node B for data transmission, and at the same time, the communication between A and B will not be affected. Figure 4 is an example of nodes C and D using the space and time when nodes A and B transmit data to communicate. During the period between receiving node B sending the CTS message and receiving the DATA message, nodes C and D successfully transmit data without causing interference to the communication between A and B. In the existing communication process, this period of time will not be available to other nodes. The new scheme improves the utilization efficiency of time resources and also improves the throughput of the network.

Claims (2)

1. A data sending and receiving method that makes full use of time resources in an underwater sensor network. Each node sends four types of messages during the communication process, which are respectively RTS, CTS, DATA and ACK messages, and RTS, CTS and ACK messages. The format of the message is fixed, and the duration of these three types of messages is assumed to be equal. The _RTS message contains the coordinate information of the sending node and the receiving node. There are two pairs of nodes ready for data transmission in the network, namely the primary node pair and the secondary node pair. Each pair of nodes can be divided into a sending node and a receiving node. The sending node needs to transmit its own data to the receiving node, then The data sending and receiving methods of these two pairs of nodes ready for data transmission are: (1) The position of each node in the underwater sensor network is fixed, and all nodes know their own position coordinates, and the transmission delay between each node is obtained; (2) The underwater sensor network is synchronized throughout the network, the clocks of all nodes are consistent, and the coverage of the signals sent by each sensor node is the same; (3) The sending node and the receiving node use the RTS-CTS handshake process when transmitting data. The master node is centered. The sending node first sends an RTS message to request transmission. After receiving the RTS message, the receiving node replies a CTS message and prepares to receive data. ; After that, the sending node places the data to be sent in the DATA message for sending, and the receiving node that receives the DATA message replies with an ACK to confirm the transmission process. At the same time, the secondary node pair will also receive the RTS message. According to the position information of the primary node pair in the message, the time occupancy of each node is obtained, and the time period for which the secondary node is prohibited from sending messages is calculated. During the period of time, the secondary node pairs reasonably arrange their sending time to avoid message conflicts. 2. The data sending and receiving method according to claim 1, wherein the sending node of the secondary node pair calculates the time period for which the secondary node pair is prohibited from sending messages, and sets itself to send the RTS according to the time period forbidding sending The time t _RTS of the message and the time t _DATA of sending the DATA message, and at the same time set the sending time t _CTS of the CTS message for the corresponding receiving node, and put t _CTS in the RTS message and send it to the corresponding receiving node.