KR102078770B1 - System and Method for Supporting Improved Mobility for Downward Traffic in RPL - Google Patents

Abstract

The present invention relates to an apparatus and a method for supporting downlink traffic toward a mobility node in an RPL environment to increase reliability of downlink traffic and reduce transmission delay through retransmission to a mobile node in a mobile environment. After receiving the message, the mobility information is stored in the mobility table by checking the mobility flag.If the ACK is not received during the specified number of transmissions, if the destination of the transport packet is a mobile node and it is registered in the mobility table, the child node has moved. Downlink traffic retransmission processing unit for determining, changing the next hop MAC address to broadcast and retransmit; the mobile node periodically broadcasts DIS to request neighboring nodes DIO message, informs their location information, and the list of neighboring parent nodes Rank value and the current parent node's rank Intended to include; reference to a parent node reselection and change and control the message processor to recover a path to transmit the message to the root node DAO.

Description

System and Method for Supporting Improved Mobility for Downward Traffic in RPC in RPC environment

The present invention relates to RPL routing, and more specifically, to support downlink traffic toward a mobile node in an RPL environment to increase reliability of downlink traffic and reduce transmission delay through retransmission to a mobile node in a mobile environment. An apparatus and method are disclosed.

The Internet Engineering Task Force (IETF) ROLL Working Group proposed the IPv6 Routing Protocol Low Power and Lossy Networks (RPL), a standard routing protocol for IPv6-based low-power wireless networks that allows multiple objects to communicate with each other over the Internet.

This protocol forms a tree-based Destination Oriented Directed Acyclic Graph (DODAG) and performs routing. In addition, in order to establish a routing path of the Internet of Things (IoT) network, a network path is constructed by a preloaded OF (Objective Function).

As such, RPL is designed for low-power and noisy network environments such as IEEE 802.15.4 and power line communications, and is a multi-hop routing protocol.

RPL aims to form a tree-based Destination Oriented Directed Acyclic Graphs (DODAG) and to build a smooth network through routing.

DODAG is configured through OF (Objective Function), which calculates the relative distance from the root, and can use a separate OF to satisfy the QoS required for each network situation.

DODAG is configured through DODAG Information Object (DIO), Destination Advertisement Object (DAO), and DODAG Information Solicitation (DIS), which are control messages.

Nodes in DODAG announce their network information periodically by sending DIO messages.

Each node participates in the network after selecting the optimal parent mode indicating a single direction to the root node with the rank value calculated through OF based on the neighbor's DIO information, and secures routing information about upstream traffic.

The DAO message is used to inform the best route to the root node and information about the downstream traffic.

In non-storing mode, every node sends a DAO message to the root node, and the route takes care of all routing, just as in a centralized approach.

The DIS message is a control message that requests a DIO message. Used when a node wants to join the network or needs to update its path.

RPL is suitable for LLN environment, but it is designed based on static environment and does not consider mobility, so a technique for dealing with this is needed.

In RPL, a mobile node cannot act as a routing node, only as a terminal.

The upstream traffic of the mobile terminal node selects a new parent mode after the movement and forwards the information only to its parent node.

On the other hand, the downlink traffic is transmitted through the source routing at the root node, and in the case of the downlink traffic directed to the mobile terminal node, routing information for the existing mobility node may become invalid.

This causes packet loss until a new parent node is selected and the routing information of the route is updated through the DAO.

In addition, RPL is a tree-based protocol whose main purpose is to collect data, but downlink traffic such as P2P communication, AMI configuration, and actuation is also important.

Also, ETX (expectation transmission rate), which is the basic OF of RPL, is the number of transmissions for communication success and is the inverse of the packet transmission rate.

The higher the ETX value, it can be determined that there is a communication problem between nodes.

The child node updates the ETX for the neighboring nodes through control messages and packet transmissions, and selects a new parent node above a certain threshold.

However, the downlink traffic loss from the parent node to the child node has no effect on the child node selecting a new parent node.

It does not support fast path recovery and causes downlink packet loss until the path is restored.

Republic of Korea Patent No. 10-1208400 Republic of Korea Patent No. 10-1678964 Republic of Korea Patent No. 10-1755596

The present invention is to solve the problems of the RPL routing technology of the prior art, from the RPL environment to the mobility node to increase the reliability of the downlink traffic and reduce the transmission delay through retransmission to the mobile node in the environment where mobility exists It is an object of the present invention to provide an apparatus and method for supporting downlink traffic.

An object of the present invention is to provide an apparatus and method for supporting downlink traffic to a mobility node in an RPL environment that supports fast parent node change and path recovery of a mobile node by detecting mobility and delivering additional information to the mobile node. .

According to the present invention, assuming that the mobility of the mobile node moves based on locality, the new parent mode selects a new parent mode by using a neighbor relationship with the previous parent mode and transmits downlink traffic until the root path is updated. An object of the present invention is to provide an apparatus and method for supporting downlink traffic to a mobile node in an RPL environment.

The present invention takes advantage of the fact that when the previous parent node of the mobile node retransmits the packet in broadcast, when it detects the movement of the mobile node as a child, the parent mode is immediately set to an available 1 bit of the flow control field of the mac header. It is an object of the present invention to provide an apparatus and method for supporting downlink traffic to a mobility node in an RPL environment so as to enable fast parent node selection and path recovery in a dynamic environment in which mobility exists by sending information to be changed.

Other objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, an apparatus for supporting downlink traffic to a mobility node in an RPL environment according to the present invention stores a mobility information in a mobility table by checking a mobility flag after receiving a DAO message, and for a specified number of transmissions. If it does not receive an ACK, if the destination of the transport packet is a mobile node and is registered in the mobility table, it is determined that the child node has moved, and the downlink traffic retransmission processing unit changes the next hop MAC address to broadcast and retransmits; It periodically broadcasts DIS to request neighboring nodes to request DIO message and inform them of their location information, and reselects and changes parent node based on the rank value of neighboring parent node list and the rank value of current parent node, and sends DAO message. Control menu to restore path by sending to root node It characterized in that it comprises a; if processing.

The control message processor may reselect and change the parent node when the rank value of the neighboring parent list is smaller than the rank value of the current parent and the difference between the two values is larger than the specified threshold value.

The downlink traffic retransmission processing unit includes a DAO message processing unit for receiving a DAO message from a parent node, a mobility information storage unit storing the mobility information in a mobility table by checking a mobility flag after receiving a DAO message, and a downstream traffic. Transmission number management unit to reduce the set number of transmissions by 1 when not receiving an ACK for the existing number of transmissions when heading to the mobile node, and checks the mobile node to determine whether the destination of the transmission packet is a mobile node if an ACK is not received during the specified number of transmissions. And, if it is registered in the mobility table after checking whether the destination of the transport packet is a mobile node, it is determined that the child node has moved, and includes a downlink traffic retransmission unit for changing the next hop MAC address to broadcast and retransmitting. do.

The neighboring nodes receiving the retransmission packet by the downlink traffic retransmission unit recognize the location information of the mobile node from the DIS transmitted by the mobile node and transmit the packet to the mobile node.

In addition, the downlink traffic retransmission processing unit may be configured to detect a movement of a mobile node whose child is a time when a previous parent node of a mobile node retransmits a packet by broadcast for fast parent selection and path recovery in a dynamic environment in which mobility exists. It is characterized by sending the information to change parent immediately to usable 1bit of flow control field of mac header.

In addition, the control message processing unit broadcasts DIS periodically from the mobile node to process the control message of the mobile node and selects a parent node, requests a DIO message to neighbor nodes and informs its location information of the DIO message request unit. When the mobile node receives the DIO message and selects a new parent node, if the rank value of the neighboring parent list is less than the rank value of the current parent and the difference between the two values is greater than the specified threshold value, the parent node reselects and And a DAO message processing unit for restoring a path by transmitting a DAO message to a root when the parent mode is changed and the parent mode is changed.

In the parent node change unit, the use of the threshold value prevents the change in the parent if the rank value is small, because the overhead of the change is greater than the advantage of changing the parent node. It is characterized by using to.

The parent node change unit, after receiving a packet from neighbor nodes, checks reserved_1 bit of the flow control field of the MAC header to change the parent node, and at this time, rank value of the parent node list without considering the threshold value It is characterized by selecting this better node as a parent node.

In addition, the control message processing unit may not additionally generate and broadcast a DIO message because the mobile node does not have a router function but a role of a terminal node in the RPL.

A method for supporting downlink traffic directed to a mobility node in an RPL environment according to the present invention for achieving another object includes processing a DAO message in which a parent node receives a DAO message from a child for supporting downlink traffic directed to a mobility node in an RPL environment. Step; The mobile information storage step of storing the mobility information in the mobility table through the mobility flag check after receiving the DAO message; If the downstream traffic does not receive an ACK for the existing number of transmissions to the mobile node, the set number of transmissions decrease by 1 A mobile node identification step of checking whether a destination of a transport packet is a mobile node if an ACK is not received for a specified number of transmissions; if the destination of the transport packet is registered in the mobility table after checking whether the destination of the transport packet is a mobile node, the child node Determine that it has moved and then use the next hop MAC address It characterized in that it comprises a; change in load-cast traffic and the downlink retransmission step of retransmitting.

In this case, the neighboring nodes receiving the retransmission packet by the downlink traffic retransmission step recognize the location information of the mobile node from the DIS transmitted by the mobile node and deliver the packet to the mobile node.

In the downlink traffic retransmission step, when the previous parent node of the mobile node detects the movement of the mobile node whose child is the time to retransmit the packet in broadcast for fast parent selection and path recovery in a dynamic environment in which mobility exists. It is characterized by sending the information to change parent immediately to usable 1bit of flow control field of mac header.

In the RPL environment, a method for supporting downlink traffic toward a mobile node in accordance with the present invention for achieving another object is to broadcast a DIS periodically from a mobile node to process control messages of a mobile node and to select a parent node. Requesting DIO message and informing its location information; requesting DIO message; mobile node receiving DIO message selects a new parent node, and rank value of neighboring parent list is smaller than current parent's rank value Changing the parent node to reselect and change the parent node if the difference between the two values is greater than the specified threshold value; processing the DAO message to restore the path by sending a DAO message to the root when the parent mode is changed; It features.

In the parent node change step, the use of the threshold value prevents the change in the parent if the rank value is small, because the overhead of the change is greater than the benefit of the parent node change. It is characterized by using to.

In the parent node changing step, after the packet is received from neighboring nodes, the parent node is changed by checking reserved_1 bit of the flow control field of the MAC header, and at this time, the rank of the parent node list is not considered without considering the threshold value. The node whose value is better is selected as a parent node.

An apparatus and method for supporting downlink traffic toward a mobile node in an RPL environment according to the present invention as described above have the following effects.

First, it is possible to increase the reliability of downlink traffic and reduce transmission delay through retransmission to the mobile node in the presence of mobility.

Second, it supports fast parent node change and path recovery of mobile nodes by detecting mobility and delivering additional information to mobile nodes.

Third, assuming that the mobility of the mobile node moves based on locality, when moving, the new parent node receives downlink traffic until it selects a new parent node and updates the root path by using the neighbor relationship with the previous parent node. To be able.

Fourth, the parent node immediately changes the parent node to an available 1-bit of the flow control field of the mac header by using the fact that the previous node of the mobile node retransmits the packet in broadcast when it detects the mobile node's movement. This information is sent to enable fast parent node selection and path recovery in a dynamic environment with mobility.

1 is a configuration diagram showing an example of downlink traffic routing in a non-storing mode
2 is a diagram illustrating a downlink traffic loss and path recovery process after moving a mobile node;
3 is a timing diagram of mobile node DODAG participation
4 is a diagram illustrating a downlink traffic path after path recovery
5 is a block diagram showing downlink routing according to the present invention
6 DAO message structure
7 is an option of DAO message
8 is a diagram illustrating a process of storing mobility node information obtained from a DAO message.
9 to 11 are configuration diagrams of an apparatus for supporting downlink traffic toward a mobile node in an RPL environment according to the present invention;
12 illustrates a downlink traffic retransmission algorithm to a mobility node.
13 is a diagram illustrating a reserved field of the 802.15.4 Mac frame format
14 is a flowchart illustrating a control message processing and parent node selection process of a mobile node

Hereinafter, a preferred embodiment of an apparatus and method for supporting downlink traffic toward a mobile node in an RPL environment according to the present invention will be described in detail.

Features and advantages of the apparatus and method for supporting downlink traffic to the mobile node in the RPL environment according to the present invention will become apparent from the detailed description of each embodiment below.

1 is a diagram illustrating an example of downlink traffic routing in a non-storing mode, and FIG. 2 is a diagram illustrating a downlink traffic loss and a path recovery process after moving a mobile node.

The present invention is intended to support fast path recovery through high reliability of downlink traffic, low latency, and fast parent node selection in a dynamic environment in which mobility exists in RPL.

An apparatus and method for supporting downlink traffic to a mobility node in an RPL environment according to the present invention for improving the reliability of downlink traffic and reducing transmission delay through retransmission to a mobile node in an environment in which mobility exists. It may include.

According to the present invention, assuming that the mobility of a mobile node moves based on locality, the new parent node selects a new parent node by using a high neighboring relationship with the previous parent node and transfers downlink traffic until the root path is updated. It may include a configuration to receive.

The present invention takes advantage of the fact that when the previous parent node of the mobile node retransmits the packet in broadcast, when it detects the movement of the mobile node as a child, the parent node is immediately placed in an available 1 bit of the flow control field of the mac header. It may contain a configuration that sends information to change to enable fast parent node selection and path recovery in a dynamic environment where mobility exists.

FIG. 1 illustrates a DODAG configuration and routing path when there is top-down traffic in a node having mobility in a non-storing mode.

When node C sends a packet to mobile node D, it sends the packet to the root node for routing.

The root node checks the destination information for the packet in its routing table and then performs source routing to set the full path.

That is, the packet of node C arrives at D via node A-B. In a static environment, the loss of the top-down packet is not large, but a problem occurs when the mobile node D moves with mobility.

As shown in FIG. 2, when the mobile node D is out of the TX range of the node B, routing information for the mobile node D recorded in the network becomes invalid and packets cannot be delivered, leading to packet loss.

By default, mobile node D periodically sends DIS to nodes to select new parent nodes.

The mobile node receives a DIO from neighboring nodes in response to DIS and selects a new preferred parent node. After the parent node is selected, the mobile node sends a DAO message to the root node to update the path.

3 shows a timing diagram when a mobile node participates in DODAG.

4 shows a downlink traffic path after the path recovery, in which the mobile node D selects a new parent node after the movement and transfers a DAO message to the root node to update the path of the root node.

Due to the movement of mobile node D, packet loss occurs until a new parent node is selected and the path to the mobile node D in the network is updated through the DAO.

5 is a block diagram showing downlink routing according to the present invention.

The mobile node D selects a new parent node so that it can receive downstream traffic until it updates the route path.

Here, assuming that the mobility of the mobile node moves based on locality, the new parent node uses the point that the neighboring relationship with the previous parent node is high when moving.

6 illustrates a DAO control message structure in which a mobile node selects a parent node and transmits a DAO message to a root node.

DAO messages can carry valid options.

7 shows options of a DAO message, which are DAO message options in rfc 6550.

Add mobility_flag to tell the parent node that it has mobility. The parent node determines the mobility from the DAO message and stores the mobility information in the mobility table.

8 is a diagram illustrating a process of storing mobility node information obtained from a DAO message.

8 is an algorithm showing that a parent node stores mobility information in a mobility table by checking a mobility flag after receiving a DAO message from a child.

9 to 11 are configuration diagrams of an apparatus for supporting downlink traffic toward a mobile node in an RPL environment according to the present invention.

In the RPL environment, the apparatus for supporting downlink traffic toward the mobility node according to the present invention stores the mobility information in the mobility table through the mobility flag check after receiving the DAO message, as shown in FIG. If it is not received, if the destination of the transmission packet is a mobile node and is registered in the mobility table, it is determined that the child node has moved, and the downlink traffic retransmission processing unit 100 that changes the next hop MAC address to broadcast and retransmits it, The node periodically broadcasts DIS to request neighboring nodes to request DIO messages and inform them of their location information, and reselects and changes the parent node based on the rank value of the neighboring parent node list and the rank value of the current parent node. Control message processing unit recovers the path by sending a message to the root node 200.

Here, the control message processor 200 reselects and changes the parent node when the rank value of the neighboring parent list is smaller than the rank value of the current parent and the difference between the two values is larger than the specified threshold value.

10 illustrates a detailed configuration of the downlink traffic retransmission processing unit 100. The parent node moves to the mobility table through the DAO message processing unit 100a receiving the DAO message from the child, and checking the mobility flag after receiving the DAO message. A mobile information storage unit 100b for storing information, a transmission number management unit 100c for reducing the set number of transmissions by one if a downlink traffic does not receive an ACK when the downlink traffic is directed to a mobile node, and a designated number of transmissions If no ACK is received, the mobile node check unit 100d for checking whether the destination of the transport packet is a mobile node, and if it is registered in the mobility table after checking whether the destination of the transport packet is a mobile node, determines that the child node has moved. And a downlink traffic retransmitter 100e that changes the next hop MAC address to broadcast and retransmits.

Here, the neighboring nodes that have received the retransmission packet by the downlink traffic retransmission unit 100e recognize the location information of the mobile node from the DIS transmitted by the mobile node, and thus may transmit the packet to the mobile node.

When the downlink traffic retransmission processing unit 100 detects the movement of the mobile node whose child is the time when the previous parent node of the mobile node retransmits the packet in a broadcast for fast parent selection and path recovery in a dynamic environment in which mobility exists. Using this information, we send the information to change the parent immediately to an available 1bit of the flow control field in the mac header.

11 illustrates a detailed configuration of the control message processing unit 200. In order to process the control message of the mobile node and to select a parent node, the mobile node periodically broadcasts DIS to request a DIO message to neighboring nodes. The DIO message request unit 200a which informs the location information and the mobile node receiving the DIO message go through the process of selecting a new parent node, and the rank value of the neighboring parent list is smaller than the rank value of the current parent and the difference between the two values is different. A parent node change unit 200b for reselecting and changing a parent node when the threshold value is larger than a specified threshold value, and a DAO message processor 200c for transmitting a DAO message to a root to restore a path when the parent mode is changed.

Here, in the parent node change unit 200b, the threshold value has a small difference in the rank value, and thus, if the parent is changed, the overhead of the change is greater than the advantage of changing the parent node. To be used.

After receiving the packet from the neighbor nodes, the parent node change unit 200b checks the reserved_1 bit of the flow control field of the MAC header to change the parent node.

At this time, a node having a better rank value is selected as the parent node in the parent node list without considering the threshold value.

In addition, the control message processing unit 200 does not broadcast by additionally generating a DIO message because the mobile node has only a role of a terminal node in RPL without having a router function.

As described above, the control message processing unit 200 supports fast path recovery through high reliability of downlink traffic, low latency, and fast parent node selection in a dynamic environment in which mobility exists in the RPL.

12 is a downlink traffic retransmission algorithm to a mobility node.

In the downlink traffic retransmission process to a mobility node according to the present invention, a DAO message processing step of allowing a parent node to receive a DAO message from a child, and a movement of storing mobility information in a mobility table through a mobility flag check after receiving a DAO message The information storage step, the transmission count management step to reduce the set number of transmissions by 1 when the downlink traffic is directed to the mobile node, and the destination of the transmission packet is not received during the designated number of transmissions. If it is registered in the mobility table after checking the mobile node to check whether it is a mobile node and if the destination of the transport packet is a mobile node, it determines that the child node has moved, and then changes the next hop MAC address to broadcast and retransmits it. Traffic retransmission step.

Specifically, if the downlink traffic does not receive an ACK for the existing number of transmissions to the mobile node, the set number of transmissions is reduced by one. If the ACK is not received for the specified number of transmissions, it is determined that the destination of the transmission packet is a mobile node. If it is registered in the mobility table, it is determined that the child node has moved, and the next hop MAC address is changed to broadcast and retransmitted.

The neighboring nodes that have received the retransmission packet can recognize the location information of the mobile node from the DIS transmitted by the mobile node and can forward the packet to the mobile node.

Therefore, the mobile node selects a new parent node from the previous parent node and receives the packet while restoring the path, thereby reducing packet loss.

In addition, the following method is applied to solve the root cause of the loss of downstream traffic until the mobile node selects a new parent node and restores the path.

RPL generally uses ETX as OF.

The ETX update of the child node's neighbor node is possible when there is traffic to the neighbor node, and even if there is a loss of the downlink packet from the parent node to the child node, it does not affect the child's parent change.

In addition, even if there is traffic to neighboring nodes, it does not change the parent unless it is constant or the number of updates to ETX does not exceed a certain threshold value, which causes a lot of downlink packet loss in a dynamic environment requiring fast parent change. .

In the dynamic environment with mobility, the header of the mac header is detected when the previous node of the mobile node detects the movement of the mobile node as a child when the previous parent node of the mobile node re-broadcasts the packet for fast parent selection and path recovery. One bit available in the control field contains the information to change the parent immediately.

13 is a diagram illustrating a reserved field of the 802.15.4 Mac frame format.

14 is a flowchart illustrating a control message processing and parent selection process of a mobile node.

In the mobile node control message processing and parent selection process according to the present invention, the mobile node periodically broadcasts DIS to request the DIO message to neighbor nodes for processing the control message and parent node selection. A request for informational DIO message, and the mobile node receiving the DIO message selects a new parent node, and the threshold value of the neighboring parent list is smaller than the current parent's rank value and the difference between the two values is specified. If the value is larger than the parent node, a parent node change step of reselecting and changing the parent node and a DAO message processing step of recovering a path by transmitting a DAO message to the root when the parent mode is changed are included.

Specifically, the mobile node periodically broadcasts DIS to request neighboring nodes to request DIO messages and inform them of their location information.

The mobile node receives the DIO message and selects a new parent node. If the rank value of the neighboring parent node list is smaller than the rank value of the current parent and the difference between the two values is greater than the specified threshold value, the mobile node reselects and Change it.

The threshold value is used to prevent the change in the parent node when the rank value is small, because the overhead of the change is greater than the benefit of the change of the parent node.

After receiving the packet from neighboring nodes, the mobile node checks reserved_1 bit in the flow control field of the MAC header and changes the parent node.

At this time, a node having a better rank value is selected as the parent node without considering the threshold value. When the parent node changes, the path is restored by sending a DAO message to the root node.

In RPL, the mobile node does not have a router function but only a role of a terminal node, and thus does not generate and broadcast additional DIO messages.

The apparatus and method for supporting downlink traffic to a mobile node in an RPL environment according to the present invention described above are designed to increase reliability of downlink traffic and reduce transmission delay through retransmission to a mobile node in a mobile environment. will be.

The present invention detects mobility and provides additional information to the mobile node to support fast parent node change and path recovery of the mobile node.

As described in the above description, it will be understood that the present invention is implemented in a modified form without departing from the essential characteristics of the present invention.

Therefore, the described embodiments should be considered in descriptive sense only and not for purposes of limitation, and the scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent scope are included in the present invention. It should be interpreted.

100. Downlink traffic retransmission processing unit
200. Control message processing unit

Claims (15)

After receiving the DAO message, the mobility information is stored in the mobility table, and if the ACK is not received for the specified number of transmissions, if the destination of the transport packet is a mobile node and if it is registered in the mobility table, the child node moves. A downlink traffic retransmission processing unit for determining that it is, and retransmitting the next hop MAC address to broadcast;
The mobile node periodically broadcasts DIS, requests neighboring nodes to request DIO messages, informs them of their location information, reselects and changes the parent node based on the rank value of the neighboring parent node list and the rank value of the current parent node. And a control message processing unit for recovering a path by transmitting a DAO message to a root node.
The control message processing unit reselects and changes the parent node when the rank value of the neighboring parent list is smaller than the rank value of the current parent and the difference between the two values is greater than the specified threshold value. Device for supporting downstream traffic. delete The method of claim 1, wherein the downlink traffic retransmission processing unit,
A DAO message processing unit for receiving a DAO message from a child of a parent node;
A movement information storage unit for storing movement information in the mobility table by checking the mobility flag after receiving a DAO message;
When the downlink traffic to the mobile node does not receive an ACK for the existing number of transmissions transmission number management unit to reduce the set number of transmissions by 1,
A mobile node checking unit for checking whether a destination of a transport packet is a mobile node if an ACK is not received for a specified number of transmissions;
If the destination of the transport packet is registered in the mobility table after checking whether the destination is a mobile node, it is determined that the child node has moved, and includes a downlink traffic retransmission unit that changes the next hop MAC address to broadcast and retransmits it. Device for supporting downlink traffic from a node to a mobility node. 4. The RPL environment of claim 3, wherein neighboring nodes receiving the retransmission packet by the downlink traffic retransmission unit recognize the location information of the mobile node from the DIS transmitted by the mobile node and deliver the packet to the mobile node. Device for supporting downlink traffic from a node to a mobility node. The method of claim 3, wherein the downlink traffic retransmission processing unit,
In the dynamic environment of mobility, the flow control of the mac header is used when the previous parent node of the mobile node detects the movement of the mobile node as a child when the previous parent node of the mobile node rebroadcasts the packet for fast parent selection and path recovery. A device for supporting downlink traffic to a mobility node in an RPL environment, characterized by sending information to immediately change the parent in the usable 1 bit of the field. The method of claim 1, wherein the control message processor is further configured to process a control message of a mobile node and to select a parent node.
The DIO message request unit periodically broadcasts DIS to request neighboring nodes to request DIO messages and informs their location information.
When the mobile node receives the DIO message and selects a new parent node, if the rank value of the neighboring parent list is smaller than the rank value of the current parent and the difference between the two values is larger than the specified threshold value, the parent node is reselected and changed. A parent node change section
And a DAO message processing unit for restoring a path by transmitting a DAO message to a root when a parent mode is changed, the apparatus for supporting downlink traffic toward a mobility node in an RPL environment. The method of claim 6, wherein the use of the threshold value in the parent node change unit,
If the rank value is small, changing the parent is more likely than the benefit of changing the parent node, so it is more likely that the overhead occurs when changing the parent node. Device for supporting downstream traffic. The method of claim 6, wherein the parent node change unit,
After receiving the packet from neighbor nodes, change reserved node by checking reserved_1bit of flow control field of MAC header, and at this time, do not consider threshold value and select node with better rank value from parent node list. The apparatus for supporting downlink traffic to the mobility node in the RPL environment, characterized in that selected as. The method of claim 1, wherein the control message processing unit,
An apparatus for supporting downlink traffic toward a mobile node in an RPL environment, in which the mobile node does not have a router function but only a role of a terminal node in RPL, and thus does not generate and broadcast DIO messages. In order to support downlink traffic to a mobility node in an RPL environment,
A DAO message processing step in which a parent node receives a DAO message from a child;
A movement information storage step of storing movement information in a mobility table after checking a mobility flag after receiving a DAO message;
A transmission count management step of reducing the set number of transmissions by one if downlink traffic does not receive an ACK for the existing transmission number when the traffic is directed to the mobile node;
A mobile node identification step of confirming whether a destination of a transport packet is a mobile node if an ACK is not received for a specified number of transmissions;
If it is registered in the mobility table after checking whether the destination of the transport packet is a mobile node, it is determined that the child node has moved, downlink traffic retransmission step of changing the next hop MAC address to broadcast and retransmit;
In the downlink traffic retransmission step, it is when the previous parent node of the mobile node detects the movement of the mobile node that is a child at the time of retransmission of the packet by broadcast for fast parent selection and path recovery in a dynamic environment in which mobility exists. A method for supporting downlink traffic directed to a mobility node in an RPL environment, characterized by sending information to immediately change a parent in an available 1 bit of a flow control field of a mac header. 11. The RPL environment of claim 10, wherein neighboring nodes receiving the retransmission packet by the downlink traffic retransmission step recognize the location information of the mobile node from the DIS transmitted by the mobile node and deliver the packet to the mobile node. For support of downlink traffic from a node to a mobility node. delete In order to process control messages of mobile nodes and select parent nodes,
Requesting a DIO message to neighbor nodes by periodically broadcasting DIS in the mobile node and informing its location information;
When the mobile node receives the DIO message and selects a new parent node, if the rank value of the neighboring parent list is smaller than the rank value of the current parent and the difference between the two values is larger than the specified threshold value, the parent node is reselected and changed. Changing a parent node;
And a DAO message processing step of recovering a path by transmitting a DAO message to a root when a parent mode is changed. The method of claim 13, wherein the use of a threshold value in the parent node change step comprises:
If the rank value is small, changing the parent is more likely than the benefit of changing the parent node, so it is more likely that the overhead occurs when changing the parent node. How to support downstream traffic. The method of claim 13, wherein changing the parent node comprises:
After receiving the packet from neighbor nodes, change reserved node by checking reserved_1bit of flow control field of MAC header, and at this time, do not consider threshold value and select node with better rank value from parent node list. The method for supporting downlink traffic to the mobility node in the RPL environment, characterized in that the selection.

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