KR100779165B1 - Sensor node device for mobility support of mobile node in sensor network and thereof method - Google Patents

Abstract

The present invention provides a sensor node device for supporting mobility of a mobile node in a sensor network, comprising: a sink node, a neighboring sensor node, a network interface unit for communicating with the mobile node, and determining the position of the mobile node, and determining the position of the mobile node. A mobile monitoring unit for determining a sensor node for service of a data packet received through the network interface unit based on the received position, and a transmission method for determining a transmission method according to the position of the mobile node with respect to the data packet received through the network interface unit. A method determination unit and a status reporter for reporting a data packet transmission state through the sensor node device, and when the mobile node moves to a point where the propagation areas of the sensor nodes overlap, the propagation strength of each of the sensor nodes is determined and propagated. Hand the sensor node to a high intensity area To make a can prevent delays caused by the problem, ping pong, or too slow hand-off caused by too frequent handoffs.

Sensor network, sensor node, handoff, mobile node

Description

Sensor node device for mobility support and mobile node in sensor network and its method

1 is a view schematically showing the configuration of a sensor network according to the present invention.

FIG. 2 is a block diagram schematically illustrating a configuration of a sensor node device supporting continuous mobility of a mobile node in a sensor network according to the present invention. FIG.

3 is a view showing the configuration of a routing table according to the present invention, Figure 4 is a view showing the form of a data packet according to the present invention.

5A and 5B are flowcharts illustrating a handoff processing method of a mobile node when the sensor node has mobility according to an embodiment of the present invention.

6A and 6B are flowcharts illustrating a handoff processing method of a mobile node when a sensor node is a fixed node according to another embodiment of the present invention.

7 is a flowchart illustrating a data packet transmission method when a mobile node is handed off according to the present invention.

<Explanation of symbols for the main parts of the drawings>

100: sink node 110: sensor node

120: mobile node 200: network interface unit

210: buffer 220: event handler

230: transmission method determination unit 232: forwarding handler

234: broadcasting handler 240: movement monitoring unit

242: sensor switching management unit 244: position determination unit

246: node information handler 248: routing table

250: position detection unit 260: status report unit

The present invention relates to a sensor node device and a method for supporting mobility of a mobile node in a sensor network that continuously transmits a packet regardless of whether a node moves in a sensor network environment.

In the Internet environment, the Mobile Engineering Task Force (IETF) proposed Mobile IP as a way to support mobility of nodes. Mobile IP uses a method of registering location information through a temporary IP address whenever a node changes its access point.

Handoff of Mobile IP occurs as a result of link-layer handoff between different IP networks. Because of the independence between the layers, the handoff has occurred at the link-layer. Therefore, the mobile IP needs another method for determining the handoff time because the network IP cannot inform the mobile IP of the network-layer. To this end, all mobility agents using Mobile IP periodically broadcast advertisement messages.

The mobile node discovers the mobility agent by receiving a broadcasted advertising message. In addition, the mobile node can determine its relative position using the advertisement message. For example, if the mobile node has not received three advertisement messages in a row from the mobility agent that it has already discovered, it recognizes that it has left the network.

Mobile IP version 6 (MIPv6) proposes Eager Cell Switching (ECS) and Lazy Cell Switching (LCS) techniques to determine when to handoff a mobile node through an advertising message. .

The goal of the Eager Cell Switching technique is to perform Mobile IP handoffs to the new network as quickly as possible, i.e. as soon as the mobile node discovers a new communicable mobility agent (as soon as it receives an advertising message from the new mobility agent), it performs a handoff. Perform.

The Eager Cell Switching technique detects the movement of the mobile node using the address of the agent included in the advertisement message. When communication between the mobile node and the mobility agent is temporarily stopped due to a data transmission failure on the wireless channel, communication with the existing mobility agent is resumed when an advertisement message is received from the currently connected mobility agent.

Since the mobile IP is not aware of the communication disconnection with the existing mobility agent caused by the handoff at the link-layer due to the independence between layers, the mobile node in the Eager Cell Switching scheme uses an advertisement message from the new mobility agent to another network. Recognize the movement of. The mobile node performs a handoff to a new mobility agent whenever an advertisement message is received from another mobility agent except for the currently connected mobility agent.

The goal of the Lazy Cell Switching technique is to avoid performing Mobile IP handoff until absolutely necessary. That is, the mobile node performs a handoff to the new mobility agent only when communication with the mobility agent that is currently connected is lost.

Mobile node in Lazy Cell Switching technique recognizes mobility to other network through lifetime of advertisement message of mobility agent. Each time a mobile node receives an advertising message from a mobility agent, its lifetime is initialized. When the lifetime expires, the mobile node moves to another network to determine that it is no longer able to communicate with the mobility agent it is connected to and performs a handoff. do.

The mobile node maintains a lifetime for all mobility agents that have successfully sent advertising messages. If it is unable to communicate with the currently connected mobility agent, the mobile node registers with another mobility agent whose lifetime has not expired. If there is no other mobility agent whose lifetime has not expired, the mobile node searches for a new mobility agent that can communicate through the agent solicitation process.

However, the Eager Cell Switching technique responds quickly to the movement of the mobile node, but the following assumptions are required for the type of movement of the mobile node in order to achieve efficient switching. The mobile node must move in a straight line direction and not return to the previous mobility agent immediately after switching is performed. If the movement type of the mobile node does not satisfy the above assumptions, there is a problem that unnecessary handoff occurs frequently (Ping-pong). That is, ECS can perform a fast handoff, but there is a disadvantage in that unnecessary handoff occurs frequently when the mobile node exists in the boundary region of two cells.

The Lazy Cell Switching technique does not require the assumption of the mobile node's movement type to guarantee the switching efficiency and can prevent frequent handoff. However, since the mobile station attempts to handoff to another mobility agent only after disconnection from the existing mobility agent, there is a problem that the mobile node always responds slowly to the movement of the mobile node. That is, there is a disadvantage in that latency occurs during handoff.

In addition, Mobile IP, which supports the mobility of nodes, is suitable for a wireless network based on the Internet protocol, and is inadequate in a sensor network that does not use the Internet protocol.

In addition, in the conventional sensor network, a data transmission scheme sets up a transmission path and transmits data along the path. If the path is changed due to a change in the position of a node, the data transmission is delayed until the transmission path is updated, and There is a disadvantage that loss occurs.

In addition, there is a disadvantage in that data cannot be delivered during the delay time required to update the delivery path, and it acts as a serious factor that lowers the user's satisfaction.

Accordingly, an object of the present invention is to provide a sensor node device and a method for supporting mobility of a mobile node in a sensor network that is suitable for a sensor network environment and minimizes packet loss and supports continuous mobility.

Another object of the present invention is to provide a sensor node device and a method for supporting mobility of a mobile node in a sensor network capable of seamlessly delivering packets to a node moving in the sensor network.

Another object of the present invention is to provide a sensor node device for supporting mobility of a mobile node in a sensor network capable of supporting a seamless communication environment regardless of whether a node is moved or not for accurate delivery of packets in a sensor network environment. To provide a method.

According to an aspect of the present invention to achieve the above object, in the sensor node device for supporting the mobility of the mobile node in the sensor network, a network node for communication with the sink node, neighbor sensor node and the mobile node, A movement monitoring unit for determining a position of the mobile node and determining a sensor node for service of a data packet received through the network interface unit based on the determined position, and the movement with respect to the data packet received through the network interface unit Sensor node device for the mobility support of the mobile node in the sensor network, characterized in that it comprises a transmission method determination unit for determining the transmission method according to the position of the node, a status report unit for reporting the data packet transmission status through the sensor node device Is provided.

According to another aspect of the present invention, the mobile node determines whether the sensor switching is necessary using a threshold value and the signal strength (RSSI) of each sensor node, and if the sensor switching is necessary, the threshold value and each A target sensor node is determined using the signal strength of a sensor node, a handoff is performed to the determined target sensor node, an optimal path through the determined target sensor node is set, and a data packet is configured using the set optimal path. Provided is a method for supporting mobility of a mobile node in a sensor network, which performs transmission and reception.

According to another aspect of the present invention, in a method for processing handoff of a mobile node in a sensor network, RSSI of each neighboring sensor node is measured by using an advertisement message periodically transmitted from a neighboring sensor node, and each measured RSSI Determining that there is a neighbor sensor node that is greater than or equal to a preset threshold value, and if there is a neighbor sensor node that is greater than or equal to a preset threshold value, the RSSI of a source sensor node that performs a current data packet service is measured, and the measured source If the RSSI of the sensor node is not greater than or equal to a threshold value, a pre-forwarding message is transmitted to the source sensor node, and the neighboring sensor node having the highest RSSI among the RSSIs of the neighboring sensor nodes is determined as the target sensor node, and the determined target sensor node is determined. A route change message to the target node, and route from the target sensor node. When the diameter response message is received, the handoff processing method of the target mobile sensor node in the sensor network, characterized in that for performing data send and receive packets through the node is provided.

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

1 is a view schematically showing the configuration of a sensor network according to the present invention.

Referring to FIG. 1, the sensor network includes a sink node 100, one or more sensor nodes 110, and a mobile node 120.

The sink node 100 receives data transmitted by the sensor nodes 110 constituting the sensor network or transmits data to the sensor node 110.

In addition, when the sink node 100 receives a routing request (RREQ) message for the mobile node 100 from the sensor node 110, the sink node 100 sets a routing path using the path on which the RREQ message is transmitted, and the corresponding sensor. The node 110 sends a routing reply (RRP) message.

In addition, when the mobile node 120 is handed off and the sensor switching occurs, the sink node 100 sets an optimal path for communication with the mobile node 120, and sets a data packet through the set optimal path. Perform the transmission and reception.

The sensor node 110 collects information of the mobile node 120 and transmits the information to the sink node 110. The sink node 110 is not fixed but is guaranteed to some extent mobile.

The sensor node 110 located within a certain distance from the sink node 100 directly transmits data to be transmitted to the sink node 100. However, the sensor nodes 110b, 110d, 110f, and 110d, which are not located within a certain distance from the sink node 100, transmit the data to be transmitted to the sink node 100 instead of directly transmitting the data to the sink node 100. It transmits to the nodes 110a, 110c, and 110e, and finally delivers them to the sink node 100.

As described above, the reason why the sensor node 110 which is not located within a certain distance transmits data using adjacent sensor nodes is to minimize power consumption due to data transmission. That is, the distance between the sink node 100 and the sensor node 110 and the power consumed by the sensor node 110 to transmit data to the sink node 100 are generally proportional to each other.

Accordingly, the sensor nodes 110b, 110d, 110f, and 110d which are not located within a predetermined distance from the sink node 100 transmit data using the plurality of sensor nodes 110a, 110c, and 110e. It is possible to minimize the power consumption.

In addition, the sensor node 110 periodically transmits an advertisement message to the mobile node 120 so that the mobile node 120 can detect the neighboring node.

In addition, when the reroute message is received from the mobile node 120, the sensor node 110 generates a RREQ message and broadcasts it to be delivered to the sink node 100, and then broadcasts the RREP from the sink node 100. When the message is received, the mobile node 120 transmits a path change response message.

In addition, the sensor node 110 sets a distance smaller than its transmission radius as a threshold value, and if the mobile node 120 is further away from the threshold value, the sensor node 110 transmits a packet to the mobile node 120 to transmit to the mobile node 120. In addition to 120, it transmits to neighbor sensor nodes.

That is, when the mobile node 120 is farther than the threshold, the sensor node 110 determines that the mobile node 120 will soon enter the transmission radius of another sensor node to switch the sensor, and The packet is transmitted to neighboring sensor nodes as well as the mobile node 120. Received Signal Strength Indication (RSSI) is used to set a threshold for the distance between the mobile node 120 and the sensor node 110.

When the sensor node 110 receives a pre-forwarding message from the mobile node 120, the sensor node 110 transmits a packet to the mobile node 120 to the mobile node 120 and neighboring sensor nodes. .

That is, the sensor node 110 receiving the pre-forwarding message transmits the data to be transmitted to the corresponding mobile node 120 and also to the neighboring sensor nodes so that the mobile node 120 is out of the transmission range. So that it can be delivered without interruption. Since the sensor node 110 does not know which sensor node the mobile node 120 will switch to, the sensor node 110 simply transmits a packet to all neighboring sensor nodes that manage a region adjacent to its transmission range.

As described above, the neighbor sensor node receiving the packet from the sensor node 110 broadcasts the received packet at its transmission radius. That is, the neighboring sensor node does not know when the mobile node 120 will enter into its transmission range and switch the sensor. Therefore, the neighboring sensor node simply broadcasts the received packet to its transmission radius, Minimize packet loss.

In addition, when a packet is received from the sink node 100 or a neighbor sensor node, the sensor node 110 checks the information of the mobile node in the routing table using the mobile node ID included in the received packet. If the mobile node ID does not exist in the routing table (ie, a new approach within the transmission radius of the sensor node), the sensor node 110 registers the mobile node information in the routing table.

If the mobile node ID exists in the routing table, the sensor node 110 determines whether the corresponding mobile node exists within its transmission range. If the mobile node 120 does not exist within its transmission range as a result of the determination, the sensor node 110 transmits the packet to the next sensor node on the data transmission path.

A description of the sensor node 110 that performs the above role will be described with reference to FIG. 2.

The mobile node 120 continuously receives the advertisement message from the neighbor sensor node and measures the RSSI of the neighbor sensor node using the received advertisement message. The mobile node 120 then uses the measured RSSI to determine the sensor switching time and sensor node 110.

The sensor network configured as described above continuously monitors the movement of the mobile node 120 in order to reduce the delay and packet loss that may occur when switching the sensor so that the mobile node 120 transmits other sensor nodes out of the current radius of the sensor node. It should be possible to recognize in real time that it has entered the radius.

Therefore, each sensor node 110 broadcasts an advertisement message periodically. Then, the mobile node 120 measures the RSSI of the neighbor sensor node using the advertisement message, and determines the appropriate sensor switching time point and the target sensor node using the measured value. That is, the mobile node 120 performs sensor switching when the RSSI of the neighboring sensor node is greater than or equal to a threshold value as it moves away from the source sensor node currently being serviced.

That is, the mobile node 120 transmits a pre-forwarding message to the source sensor node when the RSSI of the source sensor node is not greater than or equal to a threshold value. Then, the source sensor node predicts the sensor switching of the mobile node 120 in advance and determines that the sensor switching will be performed soon, and delivers the packet to neighboring sensor nodes.

Through the method of determining the sensor switching time using the advertisement message and the packet pre-forwarding method using the threshold value, delay and packet loss that may occur during sensor switching of the mobile node 120 may be reduced. However, the path for delivering packets to the mobile node 120 causes many problems after sensor switching because it simply adds a new sensor node 110 to the existing packet forwarding path.

In addition, as the number of sensor switching of the mobile node 100 increases, the mobile node 120 undergoes a large delay until the mobile node 120 receives the packet sent from the sink node 100 and delivers one packet to the mobile node 120. Energy consumption in the entire sensor network increases. Therefore, the sink node 100 should select an optimized packet forwarding path to increase the packet forwarding efficiency.

 However, if the mobile node 120 optimizes the path each time the sensor node performs the sensor switching, the control is transmitted from the sensor node 110 to the sink node 100 when the mobile node 120 frequently performs the sensor switching. The number of packets increases, which incurs a lot of overhead.

Therefore, the sink node 100 should optimize the path only when it is determined that the mobile node 120 will not switch the sensor for a predetermined time. That is, if the mobile node 120 is close to the current sensor node, it may be estimated that the mobile node 120 will not switch the sensor for a predetermined time. Therefore, when the distance between the mobile node 120 and the current sensor node is smaller than the threshold value, the path is optimized using the threshold value used in the packet pre-forwarding technique.

When the sink node 100 sets an optimal path for communication with the mobile node 120 as described above, the sink node 100 communicates with the mobile node 120 using the set optimal path. Perform.

However, if the packet is transmitted through the optimized path, the packets may be delivered to the mobile node 120 in a reversed order.

Therefore, the sink node 100 waits for the difference of transmission delays experienced by the two paths before changing from the existing path to the optimal path in order to maintain the order of the transmitted packets, and then transmits the packets using the set optimal path. do.

The transmission delay in the two paths can be obtained through a round trip time (RTT) of the path, and the sink node 100 can measure the RTT of the two paths by using separate control packets.

FIG. 2 is a block diagram schematically illustrating a configuration of a sensor node device supporting continuous mobility of a mobile node in a sensor network according to the present invention. FIG. 3 is a diagram illustrating a configuration of a routing table according to the present invention. A diagram illustrating a form of a data packet according to the invention.

Referring to FIG. 2, a sensor node device for mobility support of a mobile node may include an event for allocating a corresponding event to a network interface unit 200, a buffer 210, and a module that can process an event when an event occurs. Handler 220, a transmission decision maker 230 for determining a message transmission method, and a mobile monitoring unit for controlling and processing a function according to whether a mobile node within a service range of a sensor node moves. (240, Mobility Supervisor), a location detector (250, Location Detector) to accurately determine the location of the current mobile node, a status reporter (260, State Reporter) for reporting the current packet transmission status, a mobile node for packet transmission It includes a routing table 248 that stores the entire route up to.

The network interface unit 200 is a module for communication, and is responsible for not only communication with other sensor nodes but also communication with a mobile node and communication with a sink node.

If the data received through the network interface unit 200 is data including a message requesting several events, the corresponding data is stored in the buffer 210 and waits for the event handler 220 to process.

The event handler 220 allocates data stored in the buffer 210 to a corresponding module capable of processing an event according to a message type.

That is, the event handler 220 transmits the event to the location sensor 250 when the event requires the location information of the node. When the event handler 220 does not need to obtain information on the location, the event method determination unit ( 230).

When the message is received from the event handler 220, the transmission method determination unit 230 determines the transmission method according to the situation.

That is, the transmission method determination unit 230 performs a different transmission method according to the location of the mobile node, and includes a forwarding handler 232 and a broadcasting handler 234.

The transmission method according to the position of the mobile node is determined according to the service range and the threshold distance of the sensor node. The forwarding handler 232 transfers the data to a desired neighbor sensor node, and the broadcasting handler 234 transmits the data to all neighboring sensor nodes.

That is, the forwarding handler 232 performs a function of simply forwarding data to another sensor node when the mobile node is out of service range and forwarding a message to the mobile node when the mobile node is within a critical distance.

The broadcasting handler 234 broadcasts a message to neighboring peripheral sensor nodes when the mobile node passing the service range of the sensor node exceeds a threshold distance. In other words, the broadcasting handler 234 is a module for identifying packets of neighbors and preventing packet loss while preparing for switching.

Therefore, even if the mobile node moves to another sensor range, the mobile node can receive continuous service by the broadcasted message.

The mobile monitoring unit 240 serves to control and process a function according to the mobility of the mobile node within the service range of the sensor node, and the sensor switching management unit 242 for determining a sensor node to service the mobile node. Sensor Switching Manager), a position estimator 244 for determining whether the mobile node is present within a critical distance of the sensor node, and a node information handler for managing the routing table 248 to service the mobile node. (246, Node Information Handler).

The sensor switching manager 242 determines a sensor node that provides a service as the mobile node moves. That is, the sensor switching manager 242 predicts that it is advantageous to receive a service from another sensor node in the future when the mobile node is out of the threshold distance, and transmits the corresponding data packet to all the sensor nodes around through the broadcasting handler 234. Broadcast. If the mobile node does not move completely to another sensor node, the previous sensor node will manage the service for that node.

The position determiner 244 determines whether the sensor node has exceeded a threshold range based on the position of the mobile node and performs a necessary command. The threshold range is expressed as RSSI as a threshold for the distance between the mobile node and the sensor node transmitting current data.

That is, the position determining unit 244 stores the threshold value of the current sensor node, and determines whether the RSSI of the sensor node is greater than or equal to the stored threshold value. If the RSSI is greater than or equal to the threshold, the position determining unit 244 determines that the mobile node is within a threshold range. If the RSSI is not greater than or equal to the threshold value, the location determination unit 244 determines that the mobile node is out of the threshold range.

Then, if it is determined that the mobile node is within a threshold range, the position determiner 244 transmits data to the mobile node through the forwarding handler 232 and the network interface unit 200.

If it is determined that the mobile node is out of the threshold range, the position determiner 244 broadcasts the data to the neighboring sensor nodes by the broadcasting handler 234 so that the neighboring sensor nodes transmit the data to the corresponding service range. Do it.

The node information handler 246 serves to process information of a routing table that manages a path of a mobile node. The routing table 248 is configured as shown in FIG.

Referring to FIG. 3, the routing table 248 includes a sink node ID, a mobile node ID, a progress sensor node ID, a next sensor node ID, and time information for the path to be continued.

The time information for which the path is to be continued is deleted if there is no packet transmission.

The sink node ID refers to an ID of a sink node that broadcasts data, the mobile node ID refers to an ID of a mobile node receiving data, an advanced sensor node ID refers to an ID of a sensor transferred from the previous, and a next sensor node ID refers to data. The ID of the sensor node to pass next.

Accordingly, when the data packet is received from the sink node or the neighbor sensor node, the node information handler 246 determines whether the same mobile node ID exists in the routing table 248 using the destination ID.

At this time, the data packet is configured as shown in FIG.

Referring to FIG. 4, the data packet includes a type header, a source ID, a destination ID, a sequence number, and data. The type header is information indicating whether the current packet is network control information or a service to be provided to the mobile node.

The source ID is information indicating which sensor the data packet is from, and the destination ID is information indicating which mobile node to forward to. The sequence number is information indicating what data is in the service and is used as an ID number of a data packet.

The node information handler 246 registers the mobile node information in the routing table 248 when the determination result indicates that the destination ID does not exist in the routing table (ie, when a new approach is made within the transmission radius of the sensor node). do.

If the destination ID exists in the routing table 248 as a result of the determination, the node information handler 246 determines whether the corresponding mobile node exists within its transmission range through the location determining unit 244. .

The status report unit 260 transmits the information about the data packet transmitted from the sensor node to the connected computer. The status reporter 260 includes a packet delay reporter 262 for reporting a situation where a packet delay occurs.

The packet delay reporter 262 sends a time difference between the sequence number of the data packet to be transmitted and the previous packet to the connected computer. The computer receiving the time difference value from the packet delay reporter 262 may graph the delay for each packet and confirm that the lost packet has no delay value.

If there are a plurality of mobile nodes, the buffer 210 serves to wait for the information on each mobile node in the event handler 220. That is, the buffer 210 temporarily stores data received through the network interface unit 200.

When the mobile node moves to a point where the propagation region between the sensor nodes overlaps using the sensor node device configured as described above, the sensor switching is performed by determining the threshold value and the propagation intensity of each of the sensor nodes.

In addition, delay and packet loss in sensor switching may be reduced by using packet preforwarding according to the threshold.

5A and 5B are flowcharts illustrating a handoff processing method of a mobile node when a sensor node has mobility according to an embodiment of the present invention.

5A and 5B, the mobile node continuously receives an advertisement message from the neighboring sensor node (S500), and measures the RSSI of each neighboring sensor node using the received advertisement message (S502). That is, when the mobile node starts to move, the mobile node may continuously receive an advertisement message from neighboring neighboring sensor nodes to detect the neighboring sensor nodes.

Accordingly, the mobile node measures the RSSI of each neighboring sensor node using an advertisement message received from the neighboring sensor node. The advertisement message includes the ID of the sensor node and the threshold value of the RSSI.

After performing step 502, the mobile node determines whether there is a sensor node that is greater than or equal to a preset threshold value among the measured plurality of RSSIs (S504). Here, the threshold value is a threshold value for the distance between the mobile node and the source sensor node transmitting current data, and is expressed in RSSI.

That is, the mobile node stores the threshold value of the source sensor node, and determines whether there is a sensor node that is greater than or equal to the stored threshold value in the measured RSSI of the neighboring sensor node.

If there is a sensor node that is greater than or equal to a preset threshold as a result of the determination in step 504, the mobile node measures the RSSI of the packet transmitted from the source sensor node (S506). The mobile node measures the RSSI of the current sensor node using a data packet transmitted from the source sensor node or an advertisement message periodically broadcasted.

After performing step 506, the mobile node determines whether the measured RSSI of the source sensor node is greater than or equal to a preset threshold (S508).

If it is determined in step 508 that the measured RSSI is greater than or equal to a preset threshold, the mobile node does not handoff. This prevents handoffs from occurring too frequently because neighboring sensor nodes are too close.

If it is determined in step 508 that the measured RSSI is not greater than or equal to a preset threshold, the mobile node transmits a pre-forwarding message to the source sensor node (S510).

The pre-forwarding message indicates that the mobile node moves out of the transmission radius of the source sensor node and enters the transmission radius of another sensor node, and is a message informing the source sensor node of performing sensor switching soon.

When the source sensor node receives a pre-forwarding message from the mobile node (S534), the source sensor node transmits a packet to be transmitted to the mobile node to the mobile node and the neighbor sensor node (S536).

That is, the source sensor node transmits packets arriving after receiving a pre-forwarding message to neighboring sensor nodes as well as the mobile node.

The source sensor node receiving the pre-forwarding message forwards the packet to the mobile node and simultaneously transmits the packet to neighboring sensor nodes so that the mobile node can receive the packet without interruption even if it is out of the transmission range.

Since the source sensor node does not know which sensor node the mobile node will switch to, the sensor simply transmits a packet to all neighboring sensor nodes that manage a region neighboring its transmission range.

The neighbor sensor node receiving the packet from the source sensor node broadcasts the packet at its own transmission radius. The neighbor sensor node does not know when the mobile node will enter its transmission range and switch sensors.

Accordingly, the neighbor sensor node simply broadcasts the packet received from the source sensor node to its transmission radius to minimize delay and packet loss that may occur when switching the sensor.

After performing step 510, the mobile node selects the sensor node having the highest value among the RSSIs measured in step 502 (S512).

After performing step 512, the mobile node transmits a path change message to the selected target sensor node (S514).

When the target sensor node receives a route change message from the mobile node (S516), the target sensor node broadcasts a route setup request message (RREQ message) (S518).

When the target sensor node receives the route change message from the mobile node, the target sensor node generates a route setup request message including its own address information and address information of the sink node.

The target sensor node then broadcasts the generated route request message to neighboring sensor nodes. The neighbor sensor nodes that receive the route request message compare their destination addresses with their own addresses.

If the destination address is not the same as its own address, the corresponding sensor nodes update the received route setting request message and then broadcast them to neighboring sensor nodes to be transmitted to the sink node. The updated information includes a hop count.

Accordingly, the routing request message includes a mobile node ID, an address (sink node ID) of a destination node, a hop count, and an address of a sensor node broadcasting the routing request message.

When the sink node receives the broadcast path setting request message through step 518 (S520), the sink node sets up a routing path (S522). That is, the sink node establishes a routing path by using a hop count included in the transmitted route request message. For example, the sink node may set a path having the smallest hop count as a routing path.

After performing step 522, the sink node transmits a path setup response (RREP) message to the target sensor node using the set path (S524). That is, the sink node transmits a routing response message to the first sensor node. Then, the first sensor node transmits the routing response message to the target sensor node using the stored routing table.

When the path setting response message is received by performing step 524 (S526), the target sensor node stores the routing information receiving the path setting response message (S528), and transmits a path change response message to the mobile node (S530). ).

When the target sensor node receives a routing response message from the sink node, the target sensor node stores routing information included in the routing response message in a routing table, and transmits a routing change response message to the mobile node.

When the mobile node receives a path change response message from the target neighbor node, the mobile node completes the handoff (S532).

Then, the mobile node performs packet transmission and reception with the sink node using the set path.

After the sensor switching is performed as described above, the sink node sets the shortest path for transmitting and receiving the data packet with the mobile node.

Then, the sink node measures a round trip time (RTT) of the current packet forwarding path and the set shortest path RTT, and calculates transmission delay times of two paths from the measured RTT. Then, the sink node transmits the data packet along the shortest path set after the obtained transmission delay time so that the order of arriving packets is not changed. After this process, the mobile node communicates with the sink node in the shortest path using the target sensor node.

6A and 6B are flowcharts illustrating a handoff processing method of a mobile node when a sensor node is a fixed node according to another embodiment of the present invention.

6A and 6B, the mobile node measures an RSSI of a source sensor node that transmits a current packet (S600), and determines whether the measured RSSI is greater than or equal to a preset threshold (S602).

If it is determined in step 602 that the measured RSSI is not greater than or equal to a preset threshold, the mobile node transmits a pre-forwarding message to the source sensor node (S604).

When the pre-forwarding message is received from the mobile node (S634), the source sensor node transmits a packet to be transmitted to the mobile node to the mobile node and the neighbor sensor node (S636).

After performing step 604, the mobile node measures the RSSI of each neighboring sensor node using an advertisement message continuously received from the neighboring sensor node (S606). That is, when the mobile node starts to move, the mobile node may continuously receive an advertisement message from neighboring neighboring sensor nodes to detect the neighboring sensor nodes.

Accordingly, the mobile node measures the RSSI of each neighboring sensor node using an advertisement message received from the neighboring sensor node.

 After performing step 606, the mobile node determines whether there is a sensor node that is greater than or equal to a preset threshold value among the measured RSSIs (S608).

If there is a sensor node that is greater than or equal to a preset threshold as a result of the determination in step 608, the mobile node selects a sensor node having the strongest RSSI among the RSSIs measured in step 606 (S610).

After performing step 610, the mobile node transmits a route change message to the selected target sensor node (S612).

Since the process after step 612 is the same as the step shown in FIG. 5, the description thereof will be omitted.

7 is a flowchart illustrating a data packet transmission method when a mobile node is handed off according to the present invention.

Referring to FIG. 7, when a mobile node is handed off and a path is established, the sink node sets an optimal path for communication with the mobile node (S700). The optimal path refers to the shortest path, and the optimal path setting method may use, for example, a hop count.

When the optimal path is established in step 700, the sink node measures the RTT of the current packet forwarding path and the RTT of the shortest path, respectively (S702).

That is, the mobile node transmits a packet to be transmitted to the sink node by using a path set by being handed off. Then, the sink node determines that the mobile node will stay in the propagation area of the current sensor node for a predetermined time without moving to another area, and measures the RTT of the current packet forwarding path and the set shortest path. .

After performing step 702, the sink node obtains a transmission delay time using the measured RTTs of the two paths (S704).

After performing step 704, the sink node waits for the obtained transmission delay time, and then transmits a packet using the set optimal path (S706).

That is, the sink node obtains transmission delay times of two paths from the measured RTT and transmits packets to the shortest path after the obtained transmission delay time so that the order of arriving packets is not changed. That is, after the sync node sets the optimal path, if the packet is transmitted through the set optimal path, the sync nodes may be transferred to the mobile node in a reversed order.

For example, if the sink node transmits packet 7 on the existing path and then packet 8 on the optimal path, the mobile node sends packet 8 before packet 7 because the transmission delay on the optimal path is shorter. I can receive it. This causes serious problems when the packet delivered to the mobile node is multimedia data.

Therefore, the change from the existing propagation path to the optimal path must consider the order of packets. In order to maintain the order of the transmitted packets, the sink node must wait as much as the difference in transmission delay experienced by the two paths before changing from the existing path to the optimal path.

After waiting for the transmission delay obtained as described above, the mobile node communicates with the sink node in an optimal path by using a target sensor node. Then, as the movement of the node continuously increases, the packet forwarding path in the sensor network is also increased, which wastes unnecessary bandwidth and suffers a lot of transmission delay.

The method of the present invention as described above may be implemented in a program and stored in a recording medium in a computer-readable form. Since this process can be easily carried out by those skilled in the art will not be described in more detail.

The present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention.

As described above, according to the present invention, a mobile node in a sensor network is capable of identifying position information of a moving node using sensor nodes in a sensor network and continuously receiving data from the nearest sensor node as the node moves. It is possible to provide a sensor node device and a method for supporting mobility of a device.

In addition, according to the present invention, when the mobile node moves to a point where the propagation areas of the sensor nodes overlap, the radio nodes determine the propagation intensity of each of the sensor nodes to hand off to the sensor node of the area where the propagation intensity is too high. It is possible to provide a sensor node device and a method for supporting mobility of a mobile node in a sensor network that can prevent a ping-pong problem caused by a handoff or a delay problem due to a too slow handoff.

In addition, according to the present invention, when the packet transmission radius of the sensor node is limited to a certain distance, in the sensor network that can prevent the loss of packets transmitted to the mobile node in advance by setting a threshold value for the distance in advance It is possible to provide a sensor node device and a method for supporting mobility of a node.

In addition, according to the present invention, as the movement of the node is continuously increased by optimizing the path, the packet forwarding path in the sensor network is also increased to move in a sensor network that can waste unnecessary bandwidth and solve a large transmission delay. It is possible to provide a sensor node device and a method for supporting mobility of a node.

In addition, the present invention can provide a sensor node device and a method for supporting mobility of a mobile node in a sensor network suitable for a wireless sensor network environment and capable of supporting continuous mobility minimizing packet loss.

In addition, the present invention can provide a sensor node device and a method for supporting mobility of a mobile node in a sensor network that can receive a continuous service by a broadcasted message even if the mobile node is moved to another sensor range. .

In addition, according to the present invention, the sensor node receiving the pre-forwarding message forwards the packet to the mobile node and at the same time to the neighboring sensor nodes, so that the sensor network can receive the packet seamlessly even if the mobile node is out of the transmission range. The present invention can provide a sensor node device and a method for supporting mobility of a mobile node.

In addition, the present invention can provide a sensor node device and a method for supporting mobility of a mobile node in a sensor network that improves the efficiency of data transmission through an optimization technique of a packet forwarding path.

Claims (20)

In the sensor node device for supporting the mobility of the mobile node in the sensor network, A network interface unit for communicating with a sink node, a neighbor sensor node, and the mobile node; A mobile monitoring unit determining a location of the mobile node and determining a sensor node for service of a data packet received through the network interface unit based on the determined location; A transmission method determination unit for determining a transmission method according to the position of the mobile node with respect to the data packet received through the network interface unit; and Status report unit for reporting the status of data packet transmission through the sensor node device Sensor node device for supporting the mobility of the mobile node in the sensor network comprising a. The method of claim 1, And a buffer for temporarily storing the data packet received through the network interface unit. The sensor node device for supporting mobility of a mobile node in a sensor network. The method of claim 1, In processing the data packet received through the network interface unit, if the location of the mobile node is necessary, the data packet is transmitted to the mobile monitoring unit. If the location of the mobile node is not required, the transmission method determination unit The sensor node device for supporting the mobility of the mobile node in the sensor network, characterized in that it further comprises an event handler for transmitting to. The method of claim 1, The transmission method determination unit includes a forwarding handler for transmitting a corresponding data packet to a specific neighboring sensor node, and a broadcast casting handler for broadcasting the corresponding data packet to neighboring neighboring sensor nodes. Sensor node device. The method of claim 4, wherein The location monitoring unit detects the location of the mobile node and determines the location of the detected mobile node is within the threshold range of the current sensor node; A sensor switching manager to determine a sensor node for a service according to a determination result of the position determiner; And a node information handler in which a routing table for managing a path of the mobile node is stored. The method of claim 5, The threshold range is a threshold value for the distance between the mobile node and the current sensor node, and is a sensor node device for supporting mobility of the mobile node in a sensor network, characterized in that it is expressed as Received Signal Strength Indication (RSSI). . The method of claim 5, The sensor switching management unit transmits a data packet transmission message to the forwarding handler to transmit the data packet to the mobile node if the mobile node is within a critical range as a result of the determination of the position determining unit. And transmitting a data packet transmission message to the broadcasting handler to broadcast the data to neighboring sensor nodes, if not within range. The method of claim 5, The routing table includes a sink node ID, a mobile node ID, a progress sensor node ID, a next sensor node ID, and time information for the path to be continued. Determining, by the mobile node, whether or not sensor switching is necessary using a threshold value and Received Signal Strength Indication (RSSI) of each sensor node; Determining a target sensor node by using the threshold value and the signal strength of each sensor node when sensor determination is needed; Performing a handoff to the determined target sensor node; Setting an optimal path through the determined target sensor node; and Performing data packet transmission / reception using the configured optimal path The mobility support method of the mobile node in the sensor network comprising a. The method of claim 9, The mobile node may determine whether sensor switching is required by using a threshold value and received signal strength (RSSI) of each sensor node. Measuring received signal strength (RSSI) of each neighboring sensor node using an advertisement message periodically transmitted from neighboring sensor nodes; Determining that there is a neighbor sensor node that is greater than or equal to a preset threshold value among the measured received signal strengths (RSSI); Measuring a received signal strength (RSSI) of a source sensor node currently performing a data packet service when there is a neighbor sensor node that is greater than or equal to a preset threshold as a result of the determination; and And determining that sensor switching is necessary if the measured signal intensity (RSSI) of the source sensor node is not greater than or equal to a threshold value. The method of claim 10, And transmitting a pre-forwarding message to the source sensor node if the measured signal intensity (RSSI) of the source sensor node is not greater than or equal to a threshold value. How to support mobility. The method of claim 11, The pre-forwarding message is a message for notifying the source sensor node performing the sensor switching, the mobility support method of the mobile node in the sensor network. The method of claim 10, The advertisement message includes a corresponding sensor node ID and a threshold value of an RSSI. The method of claim 9, The mobile node may determine whether sensor switching is required by using a threshold value and received signal strength (RSSI) of each sensor node. Measuring received signal strength (RSSI) of a source sensor node currently performing a data packet service; Measuring received signal strength (RSSI) of each neighboring sensor node using an advertisement message periodically transmitted from neighboring sensor nodes if the measured signal intensity (RSSI) of the source sensor node is not greater than or equal to a threshold value; and And determining that a sensor switching is necessary when there is a neighboring sensor node that is greater than or equal to a preset threshold value in each of the measured signal strengths (RSSI). The method of claim 9, When the sensor switching is necessary as a result of the determination, determining the target sensor node by using the threshold value and the signal strength of each sensor node. And determining a neighbor sensor node having the strongest received signal strength (RSSI) among the received signal strengths (RSSI) of the neighbor sensor nodes as a target sensor node. The method of claim 9, Performing a handoff to the determined target sensor node, Transmitting a route change message to the target sensor node; Generating, by the target sensor node, a route setting request message and transmitting the generated route setting message to the sink node; Setting a routing path and transmitting a path setting response message according to the set path when the sink node receives a path setting request message; And when the target sensor node receives a route setting response message from the sink node, storing the routing path information and transmitting a route change response message to the mobile node. How to support mobility. The method of claim 9, Performing data packet transmission and reception using the set optimal path is Measuring a first round trip time of a current data packet forwarding path and a second round trip time of the set optimal path; Obtaining a transmission delay time using the measured first round trip time and the second round trip time; And waiting for the obtained transmission delay time, performing data packet transmission / reception using the set optimal path. In the handoff processing method of a mobile node in a sensor network, Measuring received signal strength (RSSI) of each neighboring sensor node using an advertisement message periodically transmitted from neighboring sensor nodes; Determining that there is a neighboring sensor node that is greater than or equal to a preset threshold value among the measured received signal strengths (RSSI); Measuring a received signal strength (RSSI) of a source sensor node currently performing a data packet service if a neighbor sensor node having a predetermined threshold value or more exists; If the measured RSI of the source sensor node is not equal to or greater than a threshold value, a pre-forwarding message is transmitted to the source sensor node and received from the received signal strength RSSI of the neighboring sensor node. Determining a neighbor sensor node having the strongest signal strength RSSI as a target sensor node; Transmitting a route change message to the determined target sensor node; and If a path change response message is received from the target sensor node, performing data packet transmission / reception through the target sensor node; The handoff processing method of the mobile node in the sensor network comprising a. The method of claim 18, The source sensor node receiving the pre-forwarding message transmits a data packet to be transmitted to the mobile node to the mobile node and the neighbor sensor node. The method of claim 18, The step of transmitting a route change message to the determined target sensor node, Generating, by the target sensor node, a route setting request message to the sink node when a route change message is received from the mobile node; Setting a routing path and transmitting a path setting response message according to the set path when the sink node receives a path setting request message; and And when the target sensor node receives a route setting response message from the sink node, storing the routing path information and transmitting a route change response message to the mobile node. How to handle handoffs.

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