KR101473305B1 - Energy Saving Method for wireless Networks - Google Patents

Abstract

The present invention discloses an energy saving method and node in a wireless network that consumes the least amount of power when communicating with a neighboring node in a wireless network.

Unlike the conventional synchronous MAC (Media Access Control), the present invention provides an asynchronous MAC. When a large amount of data is transmitted, the active period is increased only at the corresponding time, (active) period.

Description

[0001] The present invention relates to an energy saving method for a wireless network,

The present invention relates to a method and a node for minimizing the power consumption of each node on a wireless network, in particular a mesh network.

The present invention was derived from a research conducted as part of the IT growth engine technology development project of the Ministry of Information and Communication and the Institute of Information Technology Advancement [assignment: 2005-S-038-03, title: UHF RF-ID and Ubiquitous Networking Technology Development].

Since sensor nodes operate on a limited energy basis in a wireless sensor network environment, many researches have been made and are being conducted in connection with a scheme for low power operation. Especially, it is the most obstacles to service because it does not support low power in general sensor node which operates with battery. Therefore, studies on low power protocols are actively being carried out.

The zigbee MAC essentially uses a synchronous scheme that communicates with each other in time. This system consists of a normal node, a router node, and a sink node. The general node is the lowest part of the time synchronization, and the router node receives the beacon message from the sink node or the other router node and transmits the beacon to the lower router or the general node, And transmits the policy and time of network synchronization to a general node or a router node as a node that is a subject of time synchronization on the network. This method is disadvantageous in that it is difficult to synchronize and it is difficult to support low power.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an energy saving method of a node that minimizes power consumption by increasing an activation time when there is data to be transmitted by a node in a mesh network and minimizing an activation time when there is no data to be transmitted will be.

Other objects and advantages of the present invention will become apparent from the following description, and it will be understood by those skilled in the art that the present invention is not limited thereto. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

In order to save and minimize power consumption through operation of a mesh network that minimizes an active duration of a node, when a large amount of data is transmitted, the activation period is increased only at the corresponding time, So that the activation period can be flexibly changed.

The energy saving method of a node in a wireless network of the present invention is a method of notifying a wake up at the same interval and detecting a wakeup notice interval of a source node Receiving a wake-up notification from a destination node; And transmitting data within the activation period if the activation period estimated based on the wake-up notification is equal to or larger than the data size.

The energy saving method of a node in a wireless network of the present invention is a method of notifying a wake up at the same interval and detecting a wakeup notice interval of a source node Requesting an activation period extension to a plurality of neighboring nodes; And broadcasting the data to the neighboring nodes after the completion of the request.

A node in a network operating in an energy saving mode of the present invention includes: a receiving unit for receiving a wake-up notification from a first node in the network; And a transmitter for notifying wake-up at the same interval as the first node and for transmitting data in an activation period estimated based on the wake-up notification received from the first node, wherein the wake- And the inactivation period, and the start time of the wakeup period of the nodes are not synchronized with each other.

Preferably, the transmission unit transmits data in the activation period if the estimated activation period of the first node is equal to or greater than the data size, requests activation period extension if the activation period is smaller than the data size, And the data is transmitted within the extended activation period after receiving the response to the activation period extension from the activation period.

Preferably, the receiving unit receives the activation period extension request from the second node, receives data in the activation period extending from the second node, and the transmission unit transmits the response to the activation period extension to the second node .

Preferably, the extended activation period returns to an initial activation period when data reception is completed.

The present invention can provide a computer-readable recording medium storing a program for causing a computer to execute a method of saving energy of a node in a wireless network.

Due to the characteristics of the sensor network, the frequency of data transmission is not frequent or a large amount of data is transmitted, but a small amount of data is transmitted or a data transmission frequency is low. That is, most of the time is kept in a sleep state.

Therefore, in general, the activation period is minimized to save energy, and when a large amount of data is transmitted, the activation period can be increased only at the corresponding time, and the power consumption can be minimized by maintaining the activation period again after the completion of transmission.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the same components of the drawings are denoted by the same reference numerals and signs as possible even if they are shown on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Also, when an element is referred to as "comprising ", it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

The present invention is a scheme in which each node consumes the least amount of power when communicating with a neighboring node in a mesh network. Unlike the conventional synchronous MAC (Media Access Control), the present invention proposes an asynchronous MAC.

The synchronous method is a method of communicating with each node synchronously in time, and the node that is the subject of this time synchronization is called a sink node. However, this method should be accurate in terms of time, and communication is possible, and it is difficult to precisely match this time. And, if this method is used decisively, there is a disadvantage that power consumption of each node is consumed.

Therefore, the present invention transmits data using an asynchronous MAC instead of a synchronous method. The command frame used in the energy saving for mesh layer (ESM) of the present invention is a wakeup notification (WN), an extension request (EREQ), and an extension reply (EREP). The WN is sent to notify this state when the node enters the activation period. The EREQ is transmitted to extend the activation period of the receiving node. The EREP is sent for a response to the EREQ.

In accordance with the present invention, the receiving node periodically unicasts its wakeup message, and the transmitting node broadcasts the data. In order for the transmitting node to transmit data, it must analyze the wakeup period of the neighboring node and wait for a wakeup notification from the neighboring node. When a transmitting node receives a wakeup notification from a neighboring node, it sends its own message. For low power, the transmitting node transmits an EREQ (Extension Request) message to the receiving node to minimize the activation period if there is no transmission data and to extend the activation period if there is transmission data. The receiving node transmits an EREP (Extension Reply) message corresponding to the EREQ message to the transmitting node.

The algorithm proposed in the present invention consists of a data transmission method and an activation period adjustment method according to the amount of data.

The energy saving for mesh layer (ESM) of the present invention is an energy (power) saving mode using an asynchronous time schedule. The time structure of a node (device) for ESM includes an active duration and an inactive duration. A wake-up notification WN, which is an instruction frame, is transmitted at the start of the activation period. However, activation periods between nodes are not synchronized with each other.

In data transmission, the ESM of the present invention is divided into two transmission mechanisms: ESM unicasting and ESM broadcasting.

In ESM unicast transmission, the node uses a receiver-oriented mechanism. That is, after the node waits for the activation period of the receiving side, it transmits the data frame within the activation period. In an ESM broadcasting transmission, the node uses a sender-oriented mechanism. That is, the node broadcasts the data frame after waking up all the neighbor nodes by transmitting command frames for a longer time than the wakeup interval.

FIG. 1 shows an example of a time structure of the present invention.

Referring to FIG. 1, a timeline of a node is divided into a wakeup interval. The wakeup interval is again divided into an activation period and a deactivation period. In the activation period, the node transmits a wake-up notification command to indicate that it is the activation period. The node then waits for a possible frame transmission. In the deactivation period, the node turns off the receiver circuit and enters a low power sleep mode.

All nodes have the same value in the wakeup interval, but the value of the activation period can be different. The activation period of the nodes is not synchronized. Each node sends a wake-up notification (WN) command at the beginning of the activation period to notify that it is the activation period. In the WN, the wakeup interval and the activation period are reported. Therefore, when a node receives a WN from a neighbor node, the neighboring node is in the active period and the neighboring node can know the time to go to sleep again.

FIG. 2 and FIG. 3 illustrate a method of transmitting ESM unicast data according to an embodiment of the present invention.

Referring to FIG. 2, if the activation period of the node A is sufficient for data transmission, data is transmitted without adjusting the activation period. Node A (Dev A) and Node B (Dev B) are neighbor nodes. The period of each node is a wakeup interval (WI). The length of this WI is the same for node A and node B, but the start times are different. The WI corresponds to the length of the wakeup notification (WN). The WI is divided into an active period and an inactive period. The activation period is a period during which the node transmits / receives data, and the inactivation period is a period during which the node is kept in a sleep state without transmitting / receiving. Each node is operating with a minimum activation period.

Each node transmits a WN message. When there is data to be transmitted from the node B to the node A (data arrival), the node B waits until it receives the WN transmitted from the node A. When the node B receives the WN from the node A, the node B transmits the data it owns to the node A since the node A is active. Then, you go back to sleep (inactive) again. Node A may send an acknowledgment message (ACK) to Node B after receiving the data.

Referring to FIG. 3, data is transmitted by adjusting the activation period of the node A. FIG. The time structure of FIG. 3 has the structure as shown in FIG. When data is transmitted from the node B (Dev B) to the node A (Dev A), it is determined that the data transmission is not completed during the corresponding WI period due to a large amount of data to be transmitted or when the data can not be transmitted due to the activation period being too short, And sends Extension REQuest (EREQ) message to extend activation period to A. When an EREQ message is received, the node A increases its activation period in proportion to the amount of data transmitted from the node B, and transmits an Extension REPly (EREP) message including the extended time in response to the EREQ to the node B. Node B analyzes the received EREP and sends a message to node A during the active period. When the data reception is completed, the node A returns the activation period back to the original minimum time. Node A may send an acknowledgment message (ACK) to Node B after receiving the data.

4 is a view for explaining a method of transmitting ESM broadcast data according to an embodiment of the present invention.

Referring to FIG. 4, node C (Dev C) is connected to neighbor nodes including node A (Dev A) and node B (Dev B) longer than the wakeup period Transmits an EREQ message requesting an activation period, and broadcasts a data frame.

The node A and the node B increase their activation period and receive data when the EREQ message is received.

Hereinafter, node operations of a network to which the ESM mode of the present invention is applied will be described.

For the ESM mode operation of the present invention, a MAC primitive and a PIB (personal area network information base) variable for controlling the MAC layer and a mesh layer timer with 1 ms resolution as a reference clock are required.

ESM uses MAC primitives of MCPS (MAC common part sub-layer) -DATA, MCPS-PURGE, and MAC sub-layer management entity (MLME) -SET. MCPS-DATA is used to transmit or receive command frames. MCPS-PURGE is used to remove pended frames. MLME-SET is used to turn on / off the receiver circuit. By setting the macRxOnWhenIdle attribute to FALSE in the MAC PIB, the mesh layer turns off the receiver circuit. In addition to macRxOnWhenIdle, macMinBE, macMaxCSMABackoff needs to be adjusted by the mesh layer in ESM mode. Immediate response from the MAC is required for maximum energy savings.

In addition, the ESM is defined with meshTimeUnit, with a default time unit of 1 ms, in relation to the mesh layer timer. All timing parameters defined in the ESM use meshTimeUnit as a time unit, and all operations are based on a mesh layer timer.

The time structure in which the wakeup interval is divided into the activation period and the inactivation period can be described by a variable of meshWakeupOrder, meshActiveOrder, and meshBaseActiveDuration. The MESH PIB attribute meshWakeupOrder describes the interval of the periodic wakeup. As an example, the value of the meshWakeupOrder (WO) and the value of the wakeup interval (WI) may have 0? ^WO ? 14 and WI = meshBaseActiveDuration * 2 ^WO ms, respectively. In this case, if WO is equal to 15, the node always indicates the active period state without transmission, and there is no wakeup period. The meshActiveOrder is ignored if WO is equal to 15.

The MESH PIB attribute meshActiveOrder describes the length of the activation period in the wakeup interval. The value of meshActiveOrder (AO) and the activation period AD may have 0? ^AO? WO? 14 and AD = meshBaseActiveDuration * 2 ^AO ms, respectively.

The frame transmission of the ESM is controlled by two variables: mesh ESExpected and mesh ESMOn. meshESMExpected controls the transmission method for the start / join procedure.

If the value of meshESMExpected is TRUE, the node determines that the network is operating in ESM mode. Next, the node performs the ESM initialization procedure. If meshESMExpected is FALSE, initialization is performed without regard to ESM.

meshESMOn determines whether the node is using ESM mode. After binding to the network, if the node's meshESMOn is set to TRUE, the node periodically transmits the WN as defined in meshWakeupOrder. The node also has an activation period and an inactivation period as defined in meshActiveOrder. The activation period of the node may not be synchronized. If meshESMOn is FALSE, all frames are transmitted without ESM consideration.

ESM unicast data transmission starts when MESH-DATA.request occurs. If meshESMOn is TRUE, the mesh sublayer of the source node to which data is to be transmitted will turn on the receiver circuit and wait until it receives a WN from the destination node. Upon receiving the WN, the source node copies the payload's meshActiveOrder value to meshDestActiveOrder (DO). After receiving the WN, the source node estimates whether the destination node is in an active period. At this time, if the expiration time of the mesh timer is shorter than the time determined by the meshBaseActiveDuration * 2 ^DO , the source node can estimate whether the destination node is the activation period.

If the receiver of the destination node is within the activation period, one of the two transmission methods is selected and used according to the remaining activation period of the receiver. If the receiver of the destination node is in the activation period and the remaining activation period of the receiver is sufficient time to transmit the data frame, the source node's transmitter transmits the data frame. At this time, MCPS-DATA.request is used. If the remaining activation period of the destination node is not sufficient to transmit a long data frame, the source node's transmitter transmits an extension request (EREQ) command frame. In addition to the above conditions, if the remaining activation period of the destination node is not sufficient to transmit a long data frame but is greater than 3 * meshTimeUnit, the source node's transmitter may transmit an extension request (EREQ) command frame. EREQ is an instruction frame for extending the activation period of the destination node receiving unit. If the EREQ is an instruction frame broadcast at the MAC layer, the destination address is included in the mesh payload.

The destination node identifies the destination address as soon as it receives the EREQ. If the address matches its own mesh address or 0xffff, the destination node extends the activation period by the time period defined in meshEREQTime. Next, the destination node responds by sending an extended reply command (EREP) to the source node that transmitted the EREQ if the source node address exists in the EREQ. The sender of the source node that transmitted the EREQ transmits the data frame after receiving the EREP.

As an example, a node may have a minimum activation period, meshBaseActiveDuration, without considering possible long data frames to achieve maximum power savings. To transmit a long data frame to a neighboring node, the node 's transmitter must request an activation time extension. Therefore, handshaking between EREQ and EREP can be a representative method for nodes with AO set to 0.

When the MAC layer confirms SUCCESS, the mesh layer sends MESH-DARA.confirm to the upper layer to inform SUCCESS.

FIG. 5 illustrates a message flow used by a node in an ESM unicast according to this embodiment.

Referring to FIG. 5, when the MESH_DATA.request is transmitted from the upper layer of the transmitting unit of the node B having the data to be transmitted to the mesh layer, the mesh sublayer turns on the receiving unit. The node A notifies the node B of the wakeup state (Wakeup Notification), and the node B requests extension of the activation period to the node A (Extension Request). Node A responds to the extension request to the Node B. Node B transmits a data frame to node A, and node A transmits an ACK to node B.

In the node A and the node B, MCPS_DATA.request is transmitted to the mesh sublayer (MCPS) in a command frame such as a wake-up notification, an extension request, an extended response, and a mesh layer before transmission of a data frame, ), MCPS_DATA.confirm is sent to the mesh layer. In node A and node B, MCPS_DATA.indication is transmitted to the mesh layer in the mesh sublayer (MCPS) after receiving the command frame.

When ACK is transmitted from node A to node B after completion of data frame transmission, MCPS_DATA.confirm is transmitted from the mesh sublayer (MCPS) to the mesh layer, and MESH_DATA.confirm is transmitted from the mesh layer to the mesh upper layer.

On the other hand, when the node does not normally receive the frame, each node can operate as follows.

- Wake-up notification (WN) not received: If the node's mesh layer has a data frame to transmit, it turns its receiver circuit on to receive the WN of the destination node. At this time, the node sets a timer that expires after one wakeup period. If the timer expires before receiving the WN, the node increments the ESM Retry Counter (ERC) by one. If the ERC is less than the maximum number of retries, meshMAXNumESMRetries, the mesh layer retries to wait for WN reception. If the ERC is equal to or greater than meshMAXNumESMRetries, the mesh layer transmits MESH_DATA.confirm as TRANSACTION_EXPIRED state to terminate data transmission and ERC is initialized.

- Activation Extension Response (EREP) Not Received: When a mesh layer sends an EREQ, the node sets a timer to expire after the meshEREPTime. If the timer expires before receiving the EREP, the node increases the ERC by one. If the ERC is less than meshMAXNumESMRetries, the mesh layer waits for the next WN reception with the receiver circuit on, or turns off the receiver circuit until the next estimated WN time. If ERC is greater than meshMAXNumESMRetries, the mesh layer sends MESH_DATA.confirm with CHANNEL_ACCESS_FAILURE status.

- Acknowledgment message (ACK) not received: When the mesh layer issues a MAC primitive for data transmission, the execution of the primitive depends on MAC layer operation. The mesh layer must wait for confirmation from the MAC layer. If the MAC layer returns MCPS_DATA.confirm within the activation period of the destination node receiver or the extended activation period, the mesh layer sends the same status MESH_DATA.confirm to the upper layer. However, if the activation period or extended activation period of the destination node receiver expires before receiving confirmation from the MAC layer, the mesh layer may cancel the MAC layer transmission by sending MCPS_PURGE.request. Otherwise, the MAC layer can send MESH_DATA.confirm in the NO_ACK state. In either case, the mesh layer increments the ERC by 1 and follows the retry procedure described above.

- Data not received: When the mesh layer of the destination node receiver receives the EREQ, the destination node sets a timer so that the timer expires after meshEREPTime. If the timer expires before receiving the data frame or another EREQ and the activation period of the destination node receiver ends, the receiver can enter the deactivation period.

Broadcast transmissions are initiated when a MESH_DATA.request is sent for broadcast, reliable broadcast or multicast. If meshESMOn is TRUE, the mesh sublayer (MCPS) of the source node to which data is to be transmitted turns on the receiver and transmits multiple EREQs over a longer period of time than one wakeup interval. The destination address in the mesh payload of the EREQ may be 0xffff. The sender of the source node then broadcasts the data frame.

If the source node's transmitter receives an EREQ for broadcasting while transmitting an EREQ, the source node stops transmitting the EREQ and starts receiving the EREQ to receive the data frame. At this time, the source node transmission unit increments the ESM retry counter (ERC) by one. If ERC is greater than meshMAXNumESMRetries, the mesh layer sends MESH_DATA.confirm with CHANNEL_ACCESS_FAILURE status. After receiving the data frame or when no data frame is received, the source node transmitter retries the ESM broadcasting. If the ERC is less than meshMAXNumESMRetries, the mesh layer retries ESM broadcasting.

If the MAC layer confirms SUCCESS and it is a broadcast transmission, the mesh layer sends the MESH_DATA.confirm of SUCCESS to the upper layer. For reliable broadcast or multicast transmission, the mesh layer follows the decision by the corresponding transmission method.

FIG. 6 illustrates a message flow used by a node in an ESM broadcast according to this embodiment.

Referring to FIG. 6, when the MESH_DATA.request is transmitted from the upper layer of the transmitting unit of the node B having the data to be transmitted to the mesh layer, the mesh sublayer turns on the receiving unit. The node B requests extension of the activation period to the neighbor nodes including the node A (Extension Request). The node A notifies the node B of the wakeup state (Wakeup Notification), and the node B which has made the extension request transmits the data frame to the node A.

In the node A and the node B, MCPS_DATA.request is transmitted to the mesh sublayer (MCPS) in the command frame such as a wake-up notification, an extension request, and the mesh layer before transmission of the data frame, MCPS_DATA.confirm is sent to the layer. In node A and node B, MCPS_DATA.indication is transmitted to the mesh layer in the mesh sublayer (MCPS) after receiving the command frame.

After the data frame transmission is completed, MCPS_DATA.confirm is transmitted from the mesh sublayer (MCPS) to the mesh layer, and MESH_DATA.confirm is transmitted from the mesh layer to the mesh upper layer.

On the other hand, the ESM of the present invention can be started in two ways.

First, if meshESMExpected is set to FALSE, the node starts the network or binds it to the network without considering the ESM mode. After building the mesh layer address, the node can start the ESM by setting meshESMOn to TRUE. Since all connection procedures are performed before the ESM starts, beacon requests, connection requests, and data request frames can be transmitted without considering the ESM mode. The beacon frame and the connection response frame may also be received in the same manner.

Second, if meshESMExpected is set to TRUE, the node assumes that the other nodes are operating in ESM mode. A node chooses one channel before generating MLME_SCAN.request by MHSME_DISCOVER_MESH.request, MHSME_START_MESH_NETWORK.request, or MHSME_START_MESH_DEVICE.request. The node then initiates the ESM broadcast transmission method described above. The mesh layer transmits multiple EREQs for longer than one wakeup interval and generates MLME_SCAN requests for only one channel. Since the node does not yet have a mesh address, the source address of the EREQ is set to, for example, 0xffff. ScanDuration is defined as the EREQ transmission time for the MAC layer timer, and its value should be interpreted as meshTimeUnit. If the mesh layer primitive requires more than one channel, you can create a temporary list for the channels to be scanned. Next, scan each channel in the list in the same way. After the scan procedure, the node selects one channel to use. This operation may be performed by a mesh layer determination or by a parameter of MHSME_START_MESH_DEVICE.request. The node transmits a connection request frame by starting a new mesh or by the above-described ESM unicast transmission method. After receiving the WN after waiting for the WN, the node transmits the request frame. If the node successfully receives a connection response, the node sets meshESMOn to TRUE. The node initiates the WN transmission and schedules the activation and deactivation periods. ScanDuration can be used to set the timer for the WN.

Upon receiving the connection request frame, the node operating in the ESM mode turns on the receiver circuit for a predetermined time, for example, 2 * macResponseWaitTime. During this time, the node sends the WN. All data transmission is the same as the ESM transmission method described above.

7 is a flowchart illustrating an ESM data transmission method according to an embodiment of the present invention. At each step, detailed description of the contents overlapping with the above-mentioned contents will be omitted.

Referring to FIG. 7, it is determined whether the source node of the ESM mode to which data is to be transmitted is an ESM unicast transmission or an ESM broadcast transmission (S701).

In case of ESM unicast transmission, the source node waits for the WN from the destination node for data transmission and receives it (S702). The source node in the inactivity period is activated if there is data to be transmitted and waits for a wake-up notification (WN) from the destination node. The nodes in the network notify wakeup at the same interval, and the wake-up notification interval is the same as the wake-up interval composed of the active period and the inactivation period. The wake-up notification is made at the start of the activation period, and the wake-up interval start times between the nodes are not synchronized with each other.

After receiving the WN, it is determined whether the activation period of the destination node is sufficient for data transmission (S703).

If the activation period is sufficient for data transmission, the data frame is transmitted within the activation period (S704). If the activation period estimated based on WN is equal to or greater than the data size (data amount), it can be determined that data transmission is sufficient.

If the activation period is not sufficient, the EREQ is transmitted to request the activation period extension (S705). If the activation period estimated based on N is smaller than the data size (data amount), it can be determined that data transmission is insufficient.

It is determined whether the EREP is received from the destination node for the extension of the activation period (S706).

If the EREP is received, the data frame is transmitted within the extended activation period of the destination node (S704). If the EREP is not received, the WN is again received (S702). When the data transmission is completed, the destination node transmits an ACK, and the extended activation period returns to the initial activation period. When the data transfer is completed, the source node returns to the inactivation period.

On the other hand, in case of ESM broadcast transmission, the source node broadcasts the EREQ to the neighbor nodes (S707), and broadcasts the data frame after completing the request (S708). The source node requests the neighbor node to extend the activation period longer than the wakeup period.

8 is a simplified diagram illustrating message flow between nodes operating in ESM mode within a network according to an embodiment of the present invention. A detailed description of the contents overlapping with those described above will be omitted.

Referring to FIG. 8, each node (i, j) includes a receiving unit 10, 50 and a transmitting unit 30, 80. In the present embodiment, it is assumed that the node i is a data transmission node and the node j is a data reception node. In the opposite case, the same applies to the case where the node i is the data receiving node and the node j is the data transmitting node .

In the transmitting node i, the receiving unit 10 of the node i receives the EREP in response to the WN and the EREQ from the transmitting unit 80 of the node j. The transmitting unit 30 transmits data to the receiving unit 50 of the node j within the estimated active period based on the WN, and transmits the EREQ if necessary. If the estimated activation period is equal to or greater than the data size (or the period corresponding to the amount of data), the transmitter 30 transmits the data within the activation period. If the activation period is smaller than the data size, the transmitter 30 transmits the EREQ. Data is transmitted within the period. In the case of broadcast transmission, the transmitter 30 transmits the EREQ to a plurality of neighbor nodes, and broadcasts the data when the transmission is completed. In this case, the EREQ is a message requesting a longer activation period than the wakeup period.

In the receiving node j, the transmitting unit 80 of the node j periodically notifies the receiving unit 10 of the node i of the WN at the same intervals as the other nodes, the receiving unit 50 receives the data in the active period, In one case, the data is received within the extended activation period. The transmitter 80 transmits the EREP and transmits an ACK when the data reception is completed. When the data reception is completed, the extended activation period of node j returns to the original minimum activation period.

FIGS. 9A and 9B are graphs showing comparison of activation rates through simulations and experiments of data transmission and reception in LPE (Long Preamble Emulation), LPEA (Long Preamble Emulation with Acknowledgment), and ESM mode of the present invention.

The data frame used in the simulation and experiment was set to 50 bytes, the WN to 28 bytes, the EREQ / EREP to 27 bytes, the arrival rate to 0.01-0.00125fr / s and the experiment time to 600-800s. The active ratio was calculated as turn on time / time spent.

The simulation result (Anal) is indicated by a dotted line and the experimental result (Exp) is indicated by a solid line. FIG. 9A shows a case where r _b = 0, and FIG. 9B shows a case where r _b is 0.00125. Here, r _b represents the probability of receiving a broadcasting frame.

Referring to FIGS. 9A and 9B, in the case of data transmission / reception by the ESM mode of the present invention, the activation rate of the node is lower than that of LPE and LPEA. Therefore, energy savings can be achieved by shortening the activation period by the present invention in which the activation period is varied flexibly.

The present invention can also be embodied as computer-readable codes on a computer-readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and may be implemented in the form of a carrier wave (for example, transmission via the Internet) . The computer-readable recording medium may also be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the present invention can be easily inferred by programmers of the technical field to which the present invention belongs.

The present invention has been described with reference to preferred embodiments. Although specific terms have been employed herein, they are used for purposes of illustration only and are not intended to limit the scope of the invention as defined in the claims or the claims.

It will be understood by those of ordinary skill in the art that the present invention may be embodied in various other forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

1 is a diagram showing a time structure according to an embodiment of the present invention.

FIG. 2 and FIG. 3 illustrate a method of transmitting ESM unicast data according to an embodiment of the present invention.

4 is a view for explaining a method of transmitting ESM broadcast data according to an embodiment of the present invention.

5 illustrates a message flow used by a node in an ESM unicast in accordance with an embodiment of the present invention.

6 illustrates a message flow used by a node in an ESM broadcast in accordance with an embodiment of the present invention.

7 is a flowchart illustrating an ESM data transmission method according to an embodiment of the present invention.

Figure 8 is a simplified diagram illustrating message flow between nodes operating in ESM mode within a network according to an embodiment of the present invention.

FIGS. 9A and 9B are graphs showing comparison of activation rates through simulation and experiment of data transmission / reception in the conventional LPE (Long Preamble Emulation), LPEA (Long Preamble Emulation with Acknowledgment) and the ESM mode of the present invention.

Claims (12)

A node energy saving method in a wireless network composed of nodes having a wake up period composed of an activation period and a deactivation period, The first node sending a wake-up notification command including a wake-up interval and an activation period at the start of the activation period; When the first node receives the wake-up notification command from the second node, if the activation period of the second node is smaller than the size of the data to be transmitted, transmitting the extension request of the activation period to the second node; And When the first node receives a response to the extension of the activation period from the second node, transmitting data during the extended activation period of the second node, Wherein the start time of the first node and the start time of the wakeup interval of the second node are different from each other. delete delete delete delete delete delete delete delete delete delete delete

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