KR101033872B1 - Method for forming Communication protocol for underwater environment, Method for forming Network and Method for communication using the communication protocol - Google Patents

Abstract

The present invention relates to a communication protocol suitable for an underwater environment, a network forming method and a communication method using the same. First, the present invention provides a clustering-based structured network topology having sink nodes s1, s2, s3, and sensor nodes A through F, and an initialization section 10 for performing time synchronization between nodes; The MAC protocol is provided as a superframe section 20 which maintains and repairs the network topology formed in the initialization section 10 and transmits and receives data between nodes. The initialization section 10, the preamble section 12 for measuring the channel state and channel variation between the sink node (s1) (s2) (s3) and the sensor nodes (A to F) to be joined to the cluster A configuration section 14 which determines sensor nodes A to F to form a network topology, and time synchronization with the subscribed sensor nodes A to F and the sink nodes s1 to s3 managing them. It consists of a synchronization section 16 to perform. The MAC protocol forms the best network topology. In the formation of the network topology, not only the distance value due to the propagation delay time between nodes, but also the channel state and various channel variation information are considered together. According to the present invention, there is an advantage in that it is possible to form a network topology that is adaptable to the underwater environment and flexible to node transformation.

 Network topology, protocol, node, channel status, channel variation

Description

Method for forming Communication protocol for underwater environment, Method for forming Network and Method for communication using the communication protocol

The present invention relates to a sensor network, and more particularly, to a method for forming a communication protocol that is adaptive to a change in the state of an underwater channel, is flexible to a change in topology according to the mobility of a node, and enables a low power consumption of energy. It relates to a method and a communication method.

The present specification is described based on a sensor network in an underwater environment.

Underwater sensor networks have a poor communication environment compared to terrestrial sensor networks. Therefore, it is important to design underwater sensor networks considering various environmental factors in the water.

Especially when designing underwater sensor network, research on protocol suitable for underwater communication should be considered. Underwater sensor networks have characteristics such as limited radio bandwidth, high energy cost, long propagation delay and low sound speed of radio transmission media compared to terrestrial sensor networks.

However, research on communication protocols suitable for underwater sensor networks is only just beginning.

Therefore, most of the nodes in the underwater sensor network structure communicate with other nodes or higher nodes in a consistent manner by the communication protocol initially set regardless of the channel change between nodes.

For example, in the case of establishing a communication path between the sink node and the sensor node in the conventional underwater sensor network structure, the sink node first broadcasts a message to a plurality of sensor nodes located within its transmission range in the cluster, and then the sensor The node sends a response message to the sink node in response to the broadcasted message. The sink node then receives the response message and estimates the propagation delay time with the sensor node according to the received result. Based on this, distance information with the sensor node is calculated. As a result, conventionally, only limited information is applied to the network topology configuration.

That is, as described above, the marine environment has various variables, but in the related art, only the propagation delay time between the sink node and the sensor node is estimated and utilized, and the actual channel state or various variables between the sink node and the sensor node are never used. It is not considered.

In this case, time synchronization between the sync node and the sensor node is not matched, which causes a problem that data transmission and reception are not normally performed.

In addition, even if a sensor node that normally operates cannot transmit data detected by itself through an assigned time slot, or if data transmission and reception are impossible due to a collision with another node, the sink node can quickly determine whether or not a failure occurs. There are also problems that cannot be detected.

In addition, the failed sensor node continuously requests the sink node to re-register, but in this case, power consumption provided to the sensor node and the sink node is greatly generated. The generation of power consumption shortens the lifespan of the nodes, resulting in a deterioration of the ability to continuously detect underwater environmental information.

Accordingly, an object of the present invention is to solve the above problems, and to provide a method of forming a communication protocol that actively responds to the conditions of the underwater environment.

Another object of the present invention is to provide a network formation method and communication method to which a communication protocol based on underwater environment information is applied.

According to a feature of the present invention for achieving the above object, the method comprising the steps of: forming an initialization period for the sync node and the plurality of sensor nodes to form a clustering-based structured network topology and to perform time synchronization between the respective nodes; And forming a superframe section in which the sink node and the sensor node maintain and maintain the network topology formed in the initialization section and transmit and receive data between the sink node and the sensor node. The section may include a preamble section forming step of measuring a channel state and channel variation between the sink node and the sensor node, forming a component section forming a network topology by determining a sensor node to join the cluster, and the joined sensor node. And a synchronization section forming step of performing time synchronization with the sink node managing the same.

The preamble section includes a preamble message broadcast by the sink node at predetermined time intervals to measure the channel state and channel variation.

The configuration section includes a join message for requesting the sensor node to join the cluster to which the sensor node wants to join.

The synchronization section may include a beacon frame information generated through the join message, and a response message including list information of sensor nodes that have been approved for subscription so that the sensor node may be subscribed to the selected cloner. The beacon frame includes information of a participating node, time slot allocation information, interval and repetition period of a superframe, and active / inactive information.

The super frame section includes the beacon frame, an active section in which data transmission is performed, and an inactive section in which cluster join failure and resubscription of a sensor node having an error in data transmission are handled.

According to another feature of the invention, the sink node broadcasts the first message to a plurality of sensor nodes at regular time intervals; A second step of the sensor node estimating channel state and channel variation information through an average reception rate and a time interval error of the first message; A third step of receiving, by the sink node, a second message from the sensor node and predicting a transmission delay time of the sensor node based on channel state and channel variation information of the sensor node included in the second message; And determining, by the sink node, a sensor node capable of joining the cluster to which the sink node belongs, based on the channel state, channel variation, and transmission delay time extracted in the second and third steps, and forming a network topology. It consists of four steps.

In the third step, the sensor node selects a cluster to which the sensor node joins, and when the cluster is selected, measuring the virtual distance with the sink node according to the channel state and variation estimated in the second step. Calculating a random backoff time of a sensor node based on the measured virtual distance degree, and transmitting the second message to the sink node according to the calculated random backoff time for predicting the transmission delay time. It is configured to include.

In the fourth step, the information of the sensor nodes subscribed to the cluster, the timeslot allocation information, the interval and repetition period of the superframe, and the superframe are active through the channel state, channel variation, and transmission delay time. Generate a beacon frame including inactive information.

 The first message includes a sequence number, a time interval, a repeat count, and a transmission history information. The second message includes a channel status, a channel. Channel variations and receiving history information are included.

According to another feature of the present invention, information on a node participating in a network topology, time slot allocation information of the node, interval and repetition period of a superframe, active / inactive ) When the beacon frame including the information begins to be transmitted from the sink node to a plurality of sensor nodes within its transmission range, data transmission and reception between the sink node and the sensor node is performed. Transmitting, by the sensor node, the sensor node to the sink node at every superframe transmission period through the allocated time slots during the data transmission and reception; And establishing, by the sink node, the superframe policy of a next period by updating the transmitted information.

The present invention provides a communication protocol including a preamble section in which the sync node broadcasts to a sensor node at regular time intervals in order to measure channel state and channel variation between nodes in the existing MAC protocol. It can form a network topology that is more adaptive to.

In addition, it is possible to reduce the transmission failure rate between the sync node and the sensor node by enabling accurate time synchronization between the sync node and the sensor node using the communication protocol.

In addition, when the inactive section is operated to repair a node that has failed to join the cluster or a data transmission error, only the node has an active state and the other nodes remain in the sleep mode, minimizing the energy consumption of the node. can do.

Hereinafter, a communication protocol suitable for an underwater environment according to the present invention, a network forming method and a communication method applying the same will be described in detail with reference to the preferred embodiments shown in the accompanying drawings.

The present embodiment relates to a protocol for the MAC layer as a communication protocol suitable for aquatic environments, and in particular, to provide an optimal communication scheme suitable for an environment of a sensor network changed by various factors of the underwater environment.

1 is a block diagram of a network topology proposed to illustrate the present invention.

Referring to FIG. 1, it can be seen that a clustering-based structured network topology is formed for explanation of the present invention. In the embodiment, the network topology is provided with three clusters, and each cluster is comprised of sink nodes s1, s2, s3, and sensor nodes A through F. In the drawing, the sensor nodes A to F are provided only in the cluster in which the sink node s1 is located, but a plurality of sensor nodes are also provided in other sink nodes s2 and s3. In the drawing, the sensor node E is a sensor node included in a transmission range of the sink nodes s1 and s2.

The sensor nodes A to F periodically collect various sensing data in the underwater environment, and transmit them to the sink nodes s1, s2, and s3 located in the cluster to which the sensor nodes A to F belong.

The sink nodes s1, s2, and s3 serve as cluster heads. In addition, the underwater environment information collected by the sensor nodes (A to F) is periodically collected and the underwater environment information base (ML-UEIB: MAC Layer-Underwater Enviroment Information Base, hereinafter referred to as 'database (DB)') It also plays a role in creating and updating. In addition, on the basis of the information stored in the database DB, a collision phenomenon that may occur during data transmission between the sync node (s1) (s2) (s3), the sensor nodes (A to F), the sensor nodes (A to F) It also controls the operation to prevent this.

In such a network topology structure, a communication protocol suitable for an underwater environment is provided to perform data communication between nodes. The above-mentioned communication protocol is an adaptive and dynamic MAC (MAC) protocol suitable for an underwater environment, and is called 'P-MAC (Preamble-MAC)'. Hereinafter, the 'P-MAC (Preamble-MAC)' will be referred to as a 'Mac protocol'.

2 is a structural diagram of the MAC protocol.

The MAC protocol is an interval for initial topology formation and time synchronization, and the sink nodes s1, s2, and s3 generate and update the database DB, and perform a time synchronization operation based on this. The sensor nodes A to F may include an initialization period 10 to join an appropriate cluster, and a superframe period for data transmission and maintenance of a network topology formed by the initialization period ( 20).

The initialization period 10 is further divided into a preamble period 12, an organization period 14, and a synchronization period 16.

The preamble section 12 generates an adaptive MAC protocol based message (hereinafter, referred to as a 'first message'), and the sink nodes s1, s2, and s3 have a predetermined time interval. This is a section for broadcasting. The first message includes information such as a sequence number, a time interval, a repeat count, a transmission history, and the like. According to the broadcasting of the first message, the sensor nodes A to F may measure information such as channel status and channel variations, which is the sink node s1 (s2). (s3) is used as information that dynamically constructs the cluster to which it belongs.

The configuration section 14 is a section for forming a network topology based on the information collected by the preamble section 12. In this section 14, the sensor nodes A to F select a cluster to join their own, and join a message (hereinafter referred to as a 'second message') that wishes to join the selected cluster. send. The second message includes information such as channel status, channel variations, receiving history, and the like. The sink nodes s1, s2, and s3 may predict a propagation delay time of the sensor nodes A through F through the content of the second message.

The synchronization section 16, time synchronization of nodes participating in the network topology formed by the configuration section 14 and the sink node (s1) (s2) (s3) transmitted from the sensor nodes (A to F) A section for generating a beacon frame 26 to be described below through the received second message. In the beacon frame 26, information of sensor nodes A to F participating in the cluster, time slot allocation information, interval and repetition interval of a super frame, active / inactive Information). In addition, the sink nodes s1, s2, and s3 broadcast response-messages (hereinafter referred to as 'third messages') including list information of the sensor nodes A to F approved to join. It is also a section.

Next, the superframe section 20. The super frame section 20 is a section starting to drive when the beacon frame 26 generated in the sync node s1, s2, and s3 is transmitted. There are a plurality of timeslots S ₁ to S _n in this section, and one timeslot is divided into an active period 22 and an inactive period 24. The active period 22 transmits data through timeslots assigned to the sensor nodes A through F according to the transmission of the beacon frame 26, and continuously updates the state and transition information of the channel continuously updated. This section generates a data message (hereinafter referred to as a 'fourth message') along with the sensing data and provides the data message to the sink nodes s1, s2, and s3. On the other hand, the inactive section 24 is a section for resubscribing to a sensor node in which cluster join failure or data transmission error occurs among the sensor nodes A to F, and other normal sensor nodes are in a sleep node state. .

Next, a network topology is formed by applying the MAC protocol as described above, and an inter-node communication method in the formed network topology will be described with reference to FIG. 3. 3 is a flowchart illustrating a network topology formation and communication method using a MAC protocol according to an embodiment of the present invention. The process of FIG. 3 is divided into an initialization process and a data transmission section.

Initialization process

Initialization is the process of forming a network topology. The initialization process is first started by applying power to the randomly arranged sink nodes s1, s2, s3, and sensor nodes A through F.

In the preamble section 12, the sink nodes s1, s2, and s3 have a sequence number, a time interval, a repeat count, and a transmission history. A first message including information such as transmitting history is generated (s100) and broadcasted to the sensor node (actually more sensor nodes than A to F) for a predetermined number of times for a predetermined time interval (s102). ).

The broadcast first message is delivered to sensor nodes A to F located within the transmission range of the sink nodes s1, s2, and s3.

The sensor nodes A to F receive the broadcasted first message (s104), calculate the deviation of the average reception rate and time interval of the first message through this, and then calculate channel state and channel variation information. It measures (s106).

Once the information on the channel state, channel variation, etc. is measured in step 106, in the configuration section 14, the sensor nodes A to F select a cluster to which they join through the measured information. (S110). That is, the sensor nodes A to F refer to the first message transmitted from the sink nodes s1, s2, and s3, and select the cluster most suitable for the subscription. For example, in FIG. 1, the sensor node B joins a cluster in which a sink node s3 close to itself is located. The distance between nodes is too long to join the cluster where the sink nodes s2 and s3 are located, which increases the probability of data transmission failure.

When the cluster to be subscribed to is selected, the sensor nodes A to F estimate a virtual distance level according to the measured channel state and channel variation (S112).

Then, each of the sensor nodes A to F calculates a differentiated random backoff time according to the estimated virtual distance degree (S114).

When the differential random backoff time is calculated, the sensor nodes A to F maintain their random backoff time and, after a predetermined time, transmit a second message to their sync node s1 (s2) ( s3) (s116). The second message includes channel state and channel variation information measured by the sensor nodes A to F, reception history information when the first message is received, and participation in the selected cluster. Information, and the like.

Accordingly, in the configuration section 14, the sink nodes s1, s2, and s3 analyze the second message transmitted by the sensor nodes A to F, and channel with each sensor node A to F. Check the status and channel variation information (s118). In addition, the transmission delay time of each sensor node (A to F) is predicted based on the channel state and channel variation information of each sensor node (A to F) (S120). In addition, the sink nodes s1, s2, and s3 continuously accumulate and update information, such as channel state, channel variation, and transmission delay time, of each sensor node A to F in the database (s122).

According to the above process, the sink nodes s1, s2, and s3 may determine sensor nodes (ie, A to F) having a good channel state and short propagation delay time among the sensor nodes (A to F). Will be. The determination is used as the data that can best configure the network topology according to the channel change.

Accordingly, the sink nodes s1, s2, and s3 may determine the sensor nodes A to F that can join the cluster to which the second node sends the second message among the plurality of sensor nodes A to F. do. As a result, it is possible to form the network topology as shown in Figure 1 (s124). Of course, the network topology of FIG. 1 is just one example, and may be configured in other forms. The formation of such a network topology is because not only the propagation delay time but also the distance between nodes, channel state and channel variation information can be analyzed as a whole.

As such, when the network topology is formed, the sync nodes s1, s2, and s3 perform time synchronization with the sensor nodes A to F approved for subscription. The time synchronization is performed in the synchronization section 16, in which the sensor nodes (A to F) should be checked whether or not to join the cluster selected by the member in the configuration section (14).

To this end, the sink nodes s1, s2, and s3 broadcast a third message including list information of sensor nodes A to F approved to be subscribed to (s130). Then, the sensor nodes (A to F) may check whether the cluster is joined to the cluster through the third message (S132).

When the cluster subscription confirmation process is completed, the sink nodes s1, s2, and s3 perform a series of actions, such as allocating timeslots to allow data transmission of the approved sensor nodes A to F. do. That is, in detail, the sink nodes s1, s2, and s3 may include channel status, channel variations, receiving history information, and transmission information included in the second message. The super frame interval and the repetition period of each sensor node (A to F) are determined through the delay time, and a beacon frame 26 including the super frame related policy established based on this is generated (S134). The beacon frame 26 includes information on participating nodes, time slot allocation information, intervals and repetition periods of superframes, and active / inactive information.

Thus, when the synchronization process is performed, the sink nodes s1, s2, and s3 smoothly communicate between nodes in the network topology as shown in FIG. 1 according to the state of the sensor nodes A to F. It can be done.

As described above, the best network topology is formed by an initialization process according to each function of the preamble section 12-the configuration section 14-the synchronization section 16, and each cluster forming the network topology. The time synchronization between the sync nodes s1, s2, and s3 arranged in the sensor nodes A to F is completed (s136).

Next, the data communication method in the network topology formed by the initialization process will be described with reference to FIG. 3.

Data transfer process

The data transmission process is performed in the active section 22 of the superframe section 20 of the Mac protocol. The data transmission process for the data transmission is started by the beacon frame 26 generated in the synchronization section 16 is transmitted in the sync node (s1) (s2) (s3).

When the beacon frame 26 is transmitted, the sensor nodes A to F start performing data transmission through the time slot allocated by the beacon frame 26 (S142). In this case, the sensor nodes A through F generate a fourth message including channel state, channel variation and reception information, and sensing data sensed by the sensor nodes A through F, and the sink node s1 ( S2) (s3) is transmitted (s144).

Then, the sink nodes s1, s2, and s3 update and store the information included in the fourth message in a database (s146). In addition, the sink nodes s1, s2, and s3 monitor the overall state of the sensor nodes A through F through the information included in the fourth message (s148). The monitored result is reflected in the next frame superframe policy.

As such, the present embodiment can form an appropriate network topology through the initialization section 10 of the MAC protocol, and whether the sensor nodes A to F are normal / abnormal while performing inter-node communication in the network topology. You can check it.

Meanwhile, a failure may occur during network topology formation and time synchronization in the initialization section 10. The occurrence of a failure can be described as follows.

First, the sensor nodes A to F have failed to join the cluster in the initialization period when the network topology is formed. In this case, the sensor nodes A to F request to join again during the inactive section 24 of the superframe section 20.

Second, the sink nodes s1, s2, and s3 cannot receive data from the corresponding sensor nodes A through F through the designated timeslot. In this case, the sink nodes s1, s2, and s3 first exclude the allocation of timeslots of the corresponding sensor nodes A to F from the next superframe period. Then, the sensor nodes A to F may recognize that data transmitted by the previous node in the previous period was not normally transmitted. As in the first case, the sensor nodes A to F may be connected to the superframe interval ( The subscription request is made again during the period of inactivity 22 of 20). At this time, if the sink node (s1) (s2) (s3) does not receive data from the sensor nodes (A to F) a predetermined number of times, the sink node (s1) (s2) (s3) is a node failure (node failure) The sensor nodes A to F may be withdrawn from the cluster. In this case, if the detached sensor nodes A to F wish to join the cluster, they may request to join again during the inactive section 22 of the superframe section 20.

When the subscription request occurs during the inactive section 22 as described above, the sync node (s1) (s2) (s3) performs the procedure in the configuration section 14 and the synchronization section 16 described above, and whether or not to join Determine.

Meanwhile, as another example of a failure, data collision between nodes may occur. That is, the sensor nodes A to F simultaneously receive data from the sink node s1 of the cluster to which they belong and other sensor nodes. For example, it may be the sensor node E in FIG. The sensor node E is simultaneously receiving data from the sync node s1 and the sensor node F. In this case, data transmission and reception fail due to a data collision.

Accordingly, the sink node s1 may expect a collision to occur in the same time slot even when the sensor node E having a collision occurs in the next period. Therefore, the sink node s1 changes the timeslot of the sensor node in the collision. Take action.

When the above-mentioned failure occurs, the processing is performed in the inactive section of the MAC protocol, thereby minimizing the consumption of the energy source of the node.

As described above, the embodiment of the present invention periodically forms not only the distance value due to propagation delay time between nodes but also channel state and various channel variation information when forming a clustering-based structured network topology using the MAC protocol. Collected, stored and considered together. This also performs time synchronization between the sync node and the sensor node. Therefore, it can be seen that the network topology suitable for the underwater environment can be formed.

Although described with reference to the illustrated embodiment of the present invention as described above, this is merely exemplary, those skilled in the art to which the present invention pertains various modifications without departing from the spirit and scope of the present invention. It will be apparent that other embodiments may be modified and equivalent. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a schematic diagram of a network topology proposed to illustrate the present invention.

2 is a structural diagram of a Mac protocol according to a preferred embodiment of the present invention

3 is a flowchart illustrating a network topology formation and communication method using a MAC protocol according to an embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

10: initialization section 12: preamble section

14: configuration section 16: synchronization section

20: super frame section 22: active section

24: inactive section 26: beacon frame

s1, s2, s3: Sync node A to F: Sensor node

Claims (10)

Forming an initialization section in which a sink node and a plurality of sensor nodes form a clustering-based structured network topology and perform time synchronization between each node; And And forming a superframe section in which the sink node and the sensor node maintain and maintain the network topology formed in the initialization section and transmit and receive data between the sink node and the sensor node. The initializing section forming step includes a preamble section forming step of measuring channel state and channel variation between the sink node and the sensor node, and a forming section forming step of determining a sensor node to join the cluster to form a network topology. And a synchronization section forming step of performing time synchronization between the sensor node and the sink node managing the same. The method of claim 1, The preamble section includes a preamble message broadcasted by the sink node at a predetermined time interval to measure the channel state and channel variation. The method of claim 1, The configuration section is a communication protocol forming method characterized in that the sensor node includes a join message for requesting to join the cluster to be subscribed to. The method of claim 3, wherein The synchronization section may include a beacon frame information generated through the join message, and a response message including list information of sensor nodes that have been approved for subscription so that the sensor node may be subscribed to the selected cloner. Including, The beacon frame is a communication protocol comprising the information of the participating node, time slot (time slot) allocation information, the interval (interval) and repetition period of the super frame, active / inactive (inactive) information Formation method. The method of claim 4, wherein The super frame section includes the beacon frame, an active section in which data is transmitted, and an inactive section in which cluster join failure and reactivation of a sensor node having an error in data transmission are performed. . A first step of the sink node broadcasting the first message to the plurality of sensor nodes at regular time intervals; A second step of the sensor node estimating channel state and channel variation information through an average reception rate and a time interval error of the first message; A third step of receiving, by the sink node, a second message from the sensor node and predicting a transmission delay time of the sensor node based on channel state and channel variation information of the sensor node included in the second message; And A fourth node for determining a sensor node capable of joining the cluster to which the sink node belongs, based on the channel state, channel variation, and transmission delay time extracted by the sink node in the second and third steps; and forming a network topology. Network topology formation method characterized in that it comprises a step. The method of claim 6, wherein the third step, Selecting, by the sensor node, a cluster to which the sensor node joins; When the cluster is selected, measuring a virtual distance with the sink node according to the channel state and variation estimated in the second step; Calculating a random backoff time of the sensor node based on the measured virtual distance degree, and And transmitting the second message to the sink node according to the calculated random backoff time to predict the transmission delay time. The method of claim 6, wherein the fourth step The information of the sensor nodes joined to the cluster, the timeslot allocation information, the interval and repetition interval of the superframe, and the active / inactive of the superframe through the channel state, channel variation, and transmission delay time. The method of claim 1, further comprising generating a beacon frame including information. The method of claim 6, The first message includes a sequence number, a time interval, a repeat count, and transmission history information.  And the second message includes channel status, channel variations, and receiving history information. A beacon frame including information of a node participating in a network topology, time slot allocation information of the node, an interval and repetition period of a superframe, and active / inactive information is synchronized. Performing data transmission / reception between the sink node and the sensor node when the node starts to be transmitted to a plurality of sensor nodes within its transmission range; Transmitting, by the sensor node, the sensor node to the sink node at every superframe transmission period through the allocated time slots during the data transmission and reception; And And the sink node updating the transmitted information to establish a next frame superframe policy.

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