KR100892321B1 - Communication method in the sensor network using variable duty-cycle scheme - Google Patents

Abstract

The present invention discloses a communication method performed on a sensor network. The present invention has the effect of solving both the problem of transmission delay and energy consumption by increasing the duty cycle of the sensor nodes participating in the communication, and reducing the duty cycle of the nodes not participating in the communication. According to the present invention, the longer the time the node does not participate in communication, the longer the cycle time, which is a period of time periodically entering the active state, is gradually extended to the maximum cycle time, thereby reducing unnecessary energy consumption and reducing energy consumption. In addition, there is an effect that the transmission delay can be reduced during the time to participate in communication by drastically shortening the cycle time than the operation of a fixed schedule. In addition, the present invention inserts a communication bit indicating whether or not to communicate with the sync packet, the node receiving the sync packet is immediately inactive if the time interval for receiving the sync packet elapses when the communication bit is not set In this case, the time interval for receiving the transmission request message (RTS) is extended to the active interval only when the communication bit is set. Therefore, according to this method, when communication is not performed, energy consumption during a time interval for receiving a transmission request message can be reduced, thereby extending the overall life of the sensor node.

Description

Communication method in the sensor network using variable duty-cycle scheme

1 is a view for explaining the basic concept of a conventional sensor network according to the prior art.

2 is a diagram for explaining data communication according to a conventional sensor-medium access control (S-MAC) protocol.

3 is a diagram illustrating a form in which communication is performed between nodes according to a Sensor-Medium Access Control (S-MAC) protocol.

4 is a diagram illustrating a method of performing communication on a sensor network by changing an active period and changing a duty cycle according to a preferred embodiment of the present invention.

5A-5C illustrate a method of performing communication on a sensor network by changing the cycle time to change the duty cycle.

The present invention relates to a communication method performed on a sensor network. More particularly, the present invention relates to a communication method on a sensor network that can perform communication more efficiently and reduce unnecessary power consumption of each node on the sensor network.

A general mobile communication system transmits and receives data between a mobile communication terminal and a base station. That is, the mobile terminal and the base station directly transmit and receive data without passing through other mobile communication terminals / nodes. However, since such a conventional mobile communication system depends on an infrastructure called a base station, there is a problem in that communication cannot be performed in an environment and an application area in which the infrastructure is not provided.

In order to solve this problem, Ad-hoc network method and sensor network method have been developed as a technology for configuring a communication network using only mobile communication nodes without relying on infrastructure.

Application cases of sensor network technology that are currently proposed are diverse such as unmanned security, environmental monitoring, remote meter reading, and facility monitoring to monitor the temperature or pollution level in a certain area or water area, and interwork with home network system and Internet network. There are also examples of applications that work.

1 is a view for explaining the basic concept of a conventional sensor network according to the prior art. Referring to FIG. 1, the sensor node collects information about a target set by a user. Target information collected by sensor nodes is increasingly diversified in applications such as ambient temperature, object movement, seismic measurements, tsunami measurements, and unattended monitoring of the battlefield.

The sensor node transmits the collected information to the sink node. The sink node receives the data transmitted by the sensor nodes that make up the sensor network. The sensor node located within a certain distance from the sink node directly transmits data to be transmitted to the sink node. However, a sensor node not located within a certain distance from the sink node transmits the collected data to sensor nodes adjacent to the sink node instead of directly transferring the collected data to the sink node.

As described above, a node that is not located within a certain distance transmits data using nodes adjacent to the sink node in order to minimize power consumption due to data transmission.

That is, the power consumed by the sensor node to transmit data to the sink node is generally proportional to the square of the distance between the sink node and the sensor node. Therefore, the sensor node that is not located within a certain distance from the sink node can minimize the power consumption due to the data transmission by transmitting the collected data using a plurality of sensor nodes. Of course, the relay node that receives data from the other sensor node and delivers the data to the sink also transmits the data collected by the relay node to another sink node or directly.

As described above, the most important core technology in the sensor network is to prolong the life of the network by preventing unnecessary power consumption of the sensor nodes and the sink node. Because each node is powered by a relatively small battery because of its small size, it can also be very difficult to change the battery depending on the region where the nodes are installed, so to extend the life of the entire sensor network, the sensors that make up each node Minimizing power consumption is essential.

The medium access control (MAC) protocol of the sensor network directly controls the operation of the radio frequency (RF) module of the nodes, and thus, the efficiency of the nodes has a great influence on the power consumption of the nodes.

FIG. 2 is a diagram for explaining data communication according to a conventional sensor-medium access control (S-MAC) protocol. The S-MAC protocol is a form of a proposed MAC protocol for more efficient communication on a sensor network.

The biggest feature of the S-MAC protocol is that nodes on the sensor network periodically have a sleep time as shown in the figure.

Nodes on the sensor network synchronize the timing of switching the communication state to the active state and perform data communication in the active state only for a certain duty cycle.

The nodes then switch the communication state from the active state to the idle state, and then cut off the power of the RF communication module until the communication state is switched back to the active state, thereby preventing wasteful power consumption.

That is, when the communication state of the nodes is active, it means that data can be transmitted or received from a neighboring node that is one hop away from the neighboring node. Means that.

As shown in the figure, the S-MAC protocol transmits a request message similar to the 802.11 MAC protocol between the transmitting node and the receiving node during the time that the active state of the nodes is switched to the active state. -To-Send: RTS), Clear-To-Send (CTS), Data (DATA), ACK (Acknowledgement) message exchanges the order.

When the transmitting node and the receiving node switch to the active state, after sending and receiving the SYNNC (Synchronization) signal to each other and waiting for some connection time by the carrier sense multiple access (CSMA) method to avoid collision, The RTS signal is transmitted from the transmitting node to the receiving node.

The receiving node receiving the RTS signal transmits the CTS signal to the transmitting node, and receives the data transmitted from the transmitting node.

When the receiving node completes the normal reception of the data transmitted by the transmitting node, the receiving node transmits an ACK message to the transmitting node to indicate that the data transmission is normally completed.

Accordingly, nodes on the sensor network have a time for sending and receiving a SYNC signal and a time for sending and receiving an RTS signal when the communication state is switched to an active state, as shown in the figure.

Nodes that receive or transmit the RTS signal during the period of sending and receiving the RTS signal have a time (dotted box interval) for performing the CTS signal and data transmission, and for the nodes that do not have the RTS signal, Immediately after the period, the communication state is switched to the idle state.

FIG. 3 is a diagram illustrating communication between nodes according to a Sensor-Medium Access Control (S-MAC) protocol. A process of transmitting data from an A node that detects an event to a sink node according to the S-MAC protocol is performed. To show.

As shown in FIG. 3, the B node, which is one hop away from the node A, the C node which is two hops away, and the sink node, which are three hops away, are synchronized to communicate with each other with an active communication time at the same time. The event data detected by the node is transmitted to the sink node through node B, which is the parent node of node A, and node C, which is the node node B node.

Specifically, node B, which is one hop away from node A, receives the message of node A during the communication time in which the communication state is active within one communication period T, and the communication state of the next communication period T is When it is active, it transmits an RTS signal to a C node 1 hop away from its parent. When the B node receives the CTS signal from the C node, the B node transmits the message received from the A node to the C node.

Like node B, node C transmits the message of node A received from node B to the sink node when the communication state of the next communication period is active.

In this way, each sensor node of the sensor network performs communication at each communication period when the communication state is active, and sequentially transmits the message of the lower node to the upper node and transmits the message to the sink node. The node's messages are sent sequentially from the sink node to the lower nodes.

Accordingly, communication delay between nodes according to the S-MAC protocol becomes a big problem. The node with a larger hop distance from the sink node takes more communication period to receive a message from the sink node or to send a message to the sink node.

In order to solve this communication delay problem, a method of shortening the communication cycle of the sensor network may be considered, but shortening the communication cycle causes more energy consumption of each sensor node, which shortens the life of each battery operated node. There is a problem.

In addition, the above-described conventional method has a problem that operates according to a fixed communication schedule. That is, the existing scheme is configured such that all nodes on the sensor network enter an active state at the same time for synchronization of the transmitting node and the receiving node. In reality, however, only some nodes on the sensor network participate in the communication, and the remaining nodes waste energy due to unnecessary activities.

The technical problem to be achieved by the present invention is to provide a communication method on a sensor network that minimizes energy consumption of each sensor node and does not cause a communication delay problem between each sensor node.

Before describing the configuration of the present invention, terms used in the present invention are defined as follows.

A cycle is a periodic time interval consisting of an active period and a sleep period. As shown in FIG. 4 to be described later, the active section is divided into SYNC and RTS sections, and each section includes a contention window for reducing collision.

The cycle time is expressed as a multiple of the minimum cycle time T, which is the minimum time that can provide a single data transfer consisting of SYNC, RTS, CTS, DATA and ACK packet exchanges. The minimum cycle time T can be calculated from the size of each packet and the contention window size, transmission delay and RF variables.

In general, the duty cycle refers to the time ratio at which the device or system operates. In the present invention, the duty cycle refers to the ratio of the active period to the total cycle time (communication cycle time), and can be expressed as a percentage. For example, if a sensor node with a cycle time of 1 second has an active period of 200 ms and an inactive period of 800 ms, the duty cycle is 20% or 0.2.

In order to achieve the above technical problem, the present invention provides a communication method in which each node can dynamically control its own communication schedule. The basic concept of the present invention is to maximize performance by having nodes on the transmission path have a high duty cycle, while minimizing energy consumption by other nodes having a low duty cycle.

In order to allow each node to adaptively adjust its duty cycle according to the communication state, the present invention uses the following two methods independently or in combination with each other. The first is to allow each node to adjust the schedule's cycle according to network traffic. That is, a node has a low duty cycle by shortening its communication time period when participating in communication, and extends a communication time period when not participating in communication. That is, not all nodes always enter active or inactive states at the same time.

The second is that each node not only adjusts the period but also adjusts the length of the active period according to the traffic. The transmitting node of the present invention always broadcasts a communication token at the beginning of the active period to inform the transmission. Nodes receiving the communication token adjust their active duration for network control packets. Through this, each node can minimize the active period by eliminating unnecessary intervals for network control packets when there is no traffic.

This dynamic adjustment of the schedule period and the active period allows the duty cycle of each node to be controlled in accordance with network traffic, thereby minimizing energy consumption of inactive nodes that do not participate in transmission and simultaneously participating in transmission. You can maximize the performance of the active node.

The communication method for performing communication between each sensor node in the sensor network of the present invention for achieving the above technical problem, (a) the sensor node is in accordance with a predetermined cycle alignment criteria suitable for synchronization with adjacent sensor nodes Extending the cycle time; And (b) when the sensor nodes detect an event or receive a message from an adjacent node, shorten the cycle time to send the message to the adjacent node, and then perform step (a) again.

In addition, in the above-described step (a), the cycle time may be extended such that the extended cycle time is 2 ⁿ times the minimum cycle time.

In addition, step (a) described above may extend the cycle time by twice the cycle time immediately before extending the cycle time.

In addition, the above-described cycle alignment criterion may allow the cycle time to be extended only to a time in which the cycle time extension is a multiple of the cycle time to be extended.

In addition, in step (b) described above, the cycle time may be changed to the minimum cycle time.

In addition, the step (a) described above, whether the sensor nodes are included in the sync packet received from the adjacent sensor nodes to extend the cycle time according to whether or not a communication bit indicating whether there is a message to be transmitted by the adjacent sensor node is set. Can be determined.

In addition, in the above-described step (a), when the communication bit is not set, enter the inactive section as soon as the active section for receiving the sync packet is finished, it is possible to extend the cycle time according to the cycle alignment criteria.

In addition, in the above-described step (a), when the communication bit is set, the active period may be extended to a time interval for receiving the transmission request message from the transmitting node that sent the sync packet.

On the other hand, the communication method for performing communication between each sensor node on the other sensor network of the present invention for achieving the above-described technical problem, (a) a communication bit included in the sync packet according to the presence of a message to be transmitted by the transmitting node Setting and transmitting a sync packet; And (b) the receiving node receiving the sync packet and examining the communication bit to change the active period according to the setting value of the communication bit.

In addition, step (a) described above sets the communication bit to a predetermined first value when there is a message to be transmitted by the transmitting node, and sets the communication bit to correspond to the first value when there is no message to transmit. The sync packet is transmitted by setting the second value, and in the step (b), when the communication bit is set to the second value, the sync packet may enter the inactive section as soon as the active section for receiving the sync packet ends.

In addition, step (a) described above sets the communication bit to a predetermined first value when there is a message to be transmitted by the transmitting node, and sets the communication bit to correspond to the first value when there is no message to transmit. Set the second value to transmit the sync packet, and in step (b), when the communication bit is set to the first value, the receiving node may extend the active period to a time interval for receiving the transmission request message.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

4 is a diagram illustrating a method of performing communication on a sensor network by changing an active period and changing a duty cycle according to a preferred embodiment of the present invention.

Referring to FIG. 4, the process of changing the duty cycle by changing the active interval, according to the present invention, allows each node to remove an unnecessary RTS interval from its active interval when there is no traffic in a specific cycle. To this end, the present invention inserts a separate additional bit called a communication bit in the header of the SYNC packet. When the communication bit is set to 1, nodes receiving the SYNC packet extend their active period to the RTS receiving period so that they can receive the RTS in the corresponding cycle.

Therefore, when a transmitting node has a data packet to transmit, the node first broadcasts with the communication bit set to 1, and is called a communication SYNC to distinguish this SYNC packet from the clock SYNC which is a regular SYNC for clocking. Therefore, the receiving node checks the SYNC packet and if its communication bit is set to 1, it extends its active interval to the RTS receiving interval. If the communication bit is 0, the receiving nodes enter a sleep state immediately after the SYNC interval ends so that they have a low duty cycle without degrading performance.

In this case, competition for channel acquisition may occur in the SYNC interval due to two types of SYNC packets. Clock synchronization occurs rarely, so collisions are unlikely, but in the worst case, clock synchronization may fail. Therefore, the present invention allows the clock SYNC to have priority over the communication SYNC.

Referring to FIG. 4, a transmitting node to perform communication shown in FIG. 4A transmits a Sync packet in which a communication bit is set to 1 to neighboring nodes (in FIG. 4A, a CS indicates Carrier Sense). ).

The receiving node shown in (b) of FIG. 4 receives the Sync packet with the communication bit set to 1 from the transmitting node, extends the active section to the section for receiving the RTS packet, and then receives the data. 4, the idle receiving node which does not participate in the communication shown in FIG. 4C immediately enters an inactive state if a Sync packet having a communication bit set to 1 is not received during a time interval for receiving the Sync packet.

5A-5C illustrate a method of performing communication on a sensor network by changing the cycle time to change the duty cycle. Referring to FIGS. 5A to 5C, a process of changing a duty cycle by changing a cycle time may be performed. In the present invention, each node may adjust its cycle time according to traffic. This approach requires adjustment of cycle times so that all nodes can easily synchronize with each other. To this end, in the present invention, each node should set the cycle time to 2 ⁿ times the minimum cycle time unit T, and the maximum cycle time of each node is determined according to the delay requirement of the application running on the system.

For example, as shown in FIG. 5A, each node of the present invention increases its cycle time by 2 ⁿ times the minimum cycle time unit T, such as T, 2T, 4T, 8T, 16T. When the cycle time is reached, the longest cycle time (8T in FIG. 5A) is maintained, and the cycle time is reduced to T, the minimum cycle time, when an event occurs or a message is received from another neighboring node to participate in communication. Alternatively, by gradually reducing the maximum cycle time to the minimum cycle time, each node adapts its duty cycle according to the communication environment to minimize energy consumption. However, in the present invention, each node should adjust the cycle time under limited conditions in order to prevent the cycle time from shifting each other.

If all nodes start their operation at time zero after synchronization and can change their cycle time after every T time, any A node has its own cycle time when the time is an odd number of T's. If T is changed from T to 2T and the other node B changes its cycle time from T to 2T when the time is an even multiple of T, the two nodes are not synchronized.

In order to prevent the cycle times of the nodes from shifting to each other and incapable of communicating with each other in this manner, each node must change its cycle time according to an appropriate cycle alignment boundary.

The cycle sorting criteria may be variously applied, but the present invention is an example of the cycle sorting criteria, in which each node has its own cycle time in its cycle time only at a time that is a multiple of the cycle time they want to change from the first synchronized time. To change.

For example, if any one node currently has a cycle time of 8T and wants to increase its cycle time to 16T, which is twice the number of 8T, the node will increase the cycle time when the cycle time is a multiple of 16T from the first synchronized time. Should be increased to 16T.

In this way, nodes with short cycle times can always synchronize with nodes with long cycle times. As shown in FIG. 5B, a node having a cycle time of 2T is synchronized with nodes having a cycle time of T, 4T, 8T, and the like.

In addition, referring to FIG. 5C, (a) of FIG. 5C shows a synchronization timing of a node whose time period is T, and FIG. 5C (B) shows a cycle alignment in which the cycle time is described above when the cycle time is repeated four times. FIG. 5C (c) shows the synchronization timing of the node changing the cycle time whenever it is possible to change the cycle time in accordance with the above-described cycle alignment criteria. .

As illustrated in FIG. 5C, the node (c) of FIG. 5C may also be synchronized with the node (b) of FIG. 5C, in which the cycle time is changed at a time different from that of the node (c) of FIG. 5C.

In the present invention, the cycle time adjustment is determined according to the traffic. If there is no traffic, no communication SYNC packets will be sent at that cycle time, and all nodes will double the cycle time to reduce their duty cycle at the appropriate cycle alignment reference time. As shown in FIG. 5A, this method is called automatic doubling. Thus, if the network has been idle for a long time, all nodes will eventually have maximum cycle times, at which point the nodes will be in maximum energy savings.

In a preferred embodiment of the invention, the reduction in cycle time occurs when an event occurs. The receiving node specified in the RTS packet transmitted by the transmitting node reduces its cycle time to the minimum cycle time T. This method of maximizing network performance is called minimum reduction. On the other hand, if you use a method that gradually reduces the cycle time, it increases the message delay, but can be more energy efficient.

On the other hand, in the present invention, like the above-described S-MAC, each node must synchronize its clock with its neighboring nodes. Clock synchronization is used for two different purposes. The first is for synchronization between nodes. Like the S-MAC, the present invention may use a scheme in which all nodes compete to become SYNC packet originating nodes, and this method is suitable when a sink node cannot be used in a network initialization step. However, this method is time consuming, and there is a problem in that virtual clusters are generated due to generation of multiple schedules in a single network. As a result, nodes at cluster boundaries must operate according to the schedules of the two clusters and become less energy efficient due to more idle listening and overhearing.

In order to solve this problem, the present invention takes a centralized manner. In the network initialization phase, the sink node initiates network synchronization by sending a SYNC packet to its neighbors. All nodes start a periodic wakeup / sleep after receiving a SYNC packet from at least one of their neighbors.

The node receiving the SYNC packet synchronizes its timer with the schedule included in the SYNC packet and transmits the SYNC packet including the schedule and time information in the next wakeup period. That is, all nodes in the network receive the SYNC packet from the sink node, and accordingly reconstruct the SYNC packet and transmit the SYNC packet to its neighbor nodes. In this case, the method of broadcasting the SYNC packet follows a general competition process.

Any carrier sense interval reduces the probability of collision of SYNC packets, and this competition process is repeated until all sensor nodes receive SYNC packets. In wireless communication, each node needs only one SYNC packet transmission to synchronize from the sink node to the entire network node due to the characteristics of the medium.

Another function of the SYNC packet in the present invention is to provide a neighbor discovery service. When a node receives a SYNC packet from its neighbor node, it records the address of the transmitting node as one of its neighbor nodes. Every node in the network transmits the SYNC node at least once, so during the clock synchronization phase each node can get information about all its neighbors. Information about neighbor nodes obtained through this is used for scheduling adjustment of each node.

Since clock drift of each node may cause inter-node synchronization errors, clock synchronization should be performed periodically. However, clock synchronization is rarely performed because the clock drift of a typical clock generator used in sensor nodes is very small. Assuming that the clock deviation ratio is 5us per second and the synchronization interval is 1 minute, the maximum clock deviation between the transmitting and receiving nodes becomes 600 us, which transmits about 1 to 1/2 bytes over 20Kbps of transmission bandwidth of a typical sensor node. It's just time. This means that a coarse-grained control scheme is required compared to the precise synchronization scheme used in TDMA-based schemes.

If the SYNC packet cannot reach the sensor node from the sink node, the sensor node cannot wait indefinitely for the SYNC packet. To prevent the node's energy consumption, the sensor node can be programmed to wait only long enough for the SYNC packet to be delivered, and if it does not receive the SYNC packet, it will give up synchronization and operate at a low duty cycle. However, the node periodically returns to the synchronization phase and waits for a SYNC packet to synchronize its schedule.

One of the issues with the adaptive cycle time of the present invention is how a node will synchronize its wakeup interval with its neighbors. To this end, the SYNC packet of the present invention has schedule information representing the current cycle time of the transmitting node as a multiple of the minimum cycle time T. Initially, it is set to the minimum cycle time T value for fast clock synchronization. Therefore, SYNC packets provide clock, communication, and schedule synchronization.

In addition, every node maintains a schedule table that records cycle time information of its neighboring nodes. Each node records the cycle time for each node by sniffing the SYNC packets of neighbor nodes in the initial network synchronization phase. Each node then updates the schedule table independently every cycle. If there is no communication SYNC packet, all neighbor nodes are assumed to be idle and the schedule table is updated. This allows each node to predict and manage the schedules of neighboring nodes without requesting separate schedule information.

If the neighbor node is idle and the cycle time of the neighbor node is in the proper cycle alignment criterion of the node, the node may double the cycle time of the neighbor node. If receiving the communication SYNC packet, all receiving nodes change the value of the schedule table of the transmitting node to the minimum cycle time T. In addition, since communication SYNC packet receiving nodes overhear the RTS packet, the schedule information of the target node of the RTS packet is changed to the minimum value.

In this way, each node can manage schedule information of neighboring nodes independently without generating traffic. The implementation of the adaptive cycle time function does not require extra overhead except for the additional communication bits and schedule information in the SYNC packet header. Such simple tuning can dramatically improve energy efficiency and network performance.

Meanwhile, in the preferred embodiment of the present invention, the above-described adaptive active interval changing technique and the adaptive cycle time changing technique may be applied together. In this case, each node of the sensor node extends its cycle time as described above, and performs synchronization while exchanging sync packets with adjacent nodes at each extended period, thereby receiving the sync packets. Investigates whether the communication bit is set to 1 internally, and if the communication bit is not set, enters an inactive state when the time for sync packet exchange expires and extends the cycle time according to the above-described cycle alignment criteria. .

However, when the communication bit of the received sync packet is set to 1, the node extends the active interval to the interval for receiving the transmission request message (RTS), and upon receiving the transmission request message, the CTS packet and the data packet according to the conventional method. Communication is performed by exchanging, and ACK packets, and the cycle time is changed to the minimum time. In addition, the node performs communication with a minimum cycle time until the communication is terminated, and gradually extends the cycle time according to the above-described manner when the communication is terminated.

The invention can also be embodied as computer readable code on a computer readable recording medium. Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

As described above, the present invention has the effect of solving both transmission delay and energy consumption problems by increasing the duty cycle of the sensor nodes participating in the communication and reducing the duty cycle not participating in the communication.

In particular, the present invention provides two schemes for adaptively changing the duty cycle of each sensor node according to the communication environment. The first scheme is to periodically activate the active state as the time not to participate in the communication increases. It gradually extends the cycle time, which is the entering time period, to the maximum cycle time, and shortens the cycle time to the minimum time period when the node participates in communication. In addition to reducing the energy consumption by reducing the active period, there is an effect that can reduce the transmission delay than the operation of a fixed schedule by significantly reducing the cycle time during the time to participate in the communication.

In addition, the second method of adaptively changing the duty cycle inserts a communication bit indicating whether or not to communicate in a sync packet and sets a communication bit to transmit a sync packet by setting a communication bit. If the communication bit is not set, the node that receives the sync packet enters the inactive section immediately after the time interval for receiving the sync packet has elapsed, and receives the transmission request message (RTS) only when the communication bit is set. Extend the time interval to the active interval. Therefore, according to this method, when communication is not performed, energy consumption during the time interval for receiving the transmission request message can be reduced, thereby extending the overall life of the sensor node.

Claims (12)

A communication method for performing communication between sensor nodes on a sensor network, (a) extending its cycle time if the sensor nodes do not communicate with adjacent sensor nodes; And (b) when the sensor nodes detect an event or receive a message from an adjacent node, shorten its cycle time to send a message to a higher node on the path to the sink node, and then repeat step (a). Performing the steps, In step (a), the sensor nodes are included in the sync packet received from the adjacent sensor nodes to determine whether to extend the cycle time depending on whether a communication bit indicating whether a message exists for the adjacent sensor node to be transmitted is set. Communication method characterized in that. The method of claim 1, wherein step (a) Extending said cycle time such that an extended cycle time is 2 ⁿ times (n is a natural number) the minimum cycle time that can transmit a single data. The method of claim 2, wherein step (a) Extending the cycle time by twice the cycle time immediately before extending the cycle time. The method of claim 1, wherein step (a) And extending the cycle time so that the cycle time can be extended only to a time that is a multiple of the cycle time to be extended. The method of claim 1, wherein step (b) A method of communication comprising changing a cycle time to a minimum cycle time that can transmit a single data. delete The method of claim 1, wherein step (a) And when the communication bit is not set, enters an inactive section as soon as the active section for receiving the sync packet ends and extends the cycle time according to the cycle alignment criteria. The method of claim 1, wherein step (a) And when the communication bit is set, extending the active period to a time interval for receiving a transmission request message from a transmitting node that has transmitted the sync packet. A communication method for performing communication between sensor nodes on a sensor network, (a) a transmitting node transmitting the sync packet by setting a communication bit included in the sync packet according to whether a message to be transmitted exists; And (b) a receiving node receiving the sync packet, examining the communication bit and changing an active section according to a setting value of the communication bit. The method of claim 9, Step (a) sets the communication bit to a predetermined first value when there is a message to be transmitted by the transmitting node, and sets the communication bit to correspond to the first value when there is no message to transmit. Transmit the sync packet by setting the second value of The step (b) is characterized in that, when the communication bit is set to the second value, entering the inactive section as soon as the active section for receiving the sync packet is finished. The method of claim 9, Step (a) sets the communication bit to a predetermined first value when there is a message to be transmitted by the transmitting node, and sets the communication bit to correspond to the first value when there is no message to transmit. Transmit the sync packet by setting the second value of In the step (b), when the communication bit is set to the first value, the receiving node extends the active period until a time interval for receiving a transmission request message. 12. A recording medium in which the communication method of any one of claims 1 to 5 and 7 to 11 is recorded with a program code that can be read by a computer and executable.

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