KR20080067254A - Communication method in a wireless network, communication method of a mesh point in a wireless network, and a mesh point - Google Patents

Abstract

A communication method in a wireless network, a communication method of a mesh point in the wireless network, and the mesh point thereof are provided to improve a hybrid wireless mesh protocol, thereby more efficiently selecting an optimal path. One mesh point transmits an RREQ(Route-Request). Another mesh point located in a proactive tree of a proactive tree building mode receives the RREQ. If the one mesh point corresponds to a parent of another mesh point, another mesh point retransmits the RREQ after a randomized time elapses. If the one mesh point does not correspond to the parent of another mesh point, another mesh point immediately retransmits the RREQ.

Description

COMMUNICATION METHOD IN A WIRELESS NETWORK, COMMUNICATION METHOD OF A MESH POINT IN A WIRELESS NETWORK, AND A MESH POINT}

1 is a view schematically showing the structure of a wireless mesh network to which the present invention is applied;

FIG. 2 is a view for explaining a scenario in which an optimal path between a source and a destination is selected by an on-demand mode of HWMP after a tree path via a route is selected by a proactive tree building mode of HWMP.

3 illustrates a format of a data frame according to an embodiment of the present invention;

4 illustrates a format of an RREQ frame according to an embodiment of the present invention, and

FIG. 5 is a diagram illustrating each field of the RREQ frame illustrated in FIG. 4.

The present invention relates to a communication method in a wireless network, a communication method of a mesh point in a wireless network, and a mesh point.

In a wireless mesh network system, a hybrid wireless mesh protocol is used as a protocol for establishing a path for data communication.

An object of the present invention is to provide a communication method in a wireless network, a communication method of a mesh point in a wireless network, and a mesh point in a wireless network to improve the hybrid wireless mesh protocol to select and communicate with an optimal path.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

In a wireless network according to an aspect of the present invention, a communication method includes: transmitting one mesh point by RREQ (Route-Requset); Receiving another RREQ by another mesh point located in a proactive tree in a proactive tree building mode; And when the one mesh point corresponds to a parent of the other mesh point, the other mesh point retransmits the RREQ after a randomized time, and the one mesh point is the other mesh point. If not corresponding to the parent of the other mesh point immediately retransmits the RREQ; includes.

The mesh point according to an aspect of the present invention is a randomized time when receiving a Route-Request (RREQ) from a parent on a proactive tree created by a proactive tree building mode. RREQ is retransmitted after elapse, and if the one mesh point does not correspond to the parent of the other mesh point, the RREQ is retransmitted immediately.

In a wireless network according to another aspect of the present invention, a communication method includes: transmitting, by one mesh point, a route-request (RREQ) including a variable TTL (Time To Live) value to a specific mesh point; And one or more Another mesh point receiving the RREQ and retransmitting or not retransmitting the RREQ.

According to another aspect of the present invention, a mesh point selects a time-to-live (TTL) value of a route-request (RREQ) as one variable, and selects an RREQ including the selected TTL value toward a specific mesh point. send.

In a wireless network according to another aspect of the present invention, a communication method includes: transmitting, by one mesh point, a route-request (RREQ) including a depth to a specific mesh point; Another mesh point located in a proactive tree in a proactive tree building mode may include: receiving the RREQ; And the other mesh point does not retransmit the RREQ if the depth from the root of the proactive tree is greater than the depth of the RREQ, and the depth from the root of the proactive tree is equal to the depth of the RREQ. Retransmitting the RREQ if it is smaller than the depth or equal to the depth of the RREQ.

According to another aspect of the present invention, a mesh point receives a Route-Request (RREQ) including a depth transmitted from one mesh point toward a specific mesh point, and is created by the proactive tree building mode. If the depth from the root on the preactive tree is greater than the depth included in the RREQ, the depth from the root is less than or equal to the depth included in the RREQ, without retransmitting the RREQ. If it is the same as the included depth, the RREQ is retransmitted.

The mesh point according to another aspect of the present invention includes a depth in a route-request (RREQ) and transmits the RREQ toward a specific mesh point.

First, in describing the present invention, terms related to the present invention will be defined.

WLAN Mesh: A part of a distributed system that includes at least two mesh points connected through an IEEE 802.11 link and communicates through a WLAN mesh service, and refers to a wireless distributed system based on IEEE 802.11. . The WLAN mesh may support dynamic path selection, including zero or many entry points (mesh portals), automatic topology learning, and multiple hop paths. (A WLAN Mesh is an IEEE 802.11-based WDS which is part of a DS, consisting of a set of two or more Mesh Points interconnected via IEEE 802.11 links and communicating via the WLAN Mesh Services.A WLAN Mesh may support zero or more entry points (Mesh Portals), automatic topology learning and dynamic path selection (including multiple hop paths))

WLAN Mesh Service: A series of WLAN networks that support the transmission, management, and operation of WLAN meshes, including the transmission of MAC Service Data Units (MSDUs) between mesh points within a WLAN mesh. service. (The set of services provided by the WLAN Mesh that support the control, management, and operation of the WLAN Mesh, including the transport of MSDUs between Mesh Points within the WLAN Mesh.WLAN Mesh Services supplement DSS (Distribution System Services))

Mesh Point: An IEEE 802.11 entity that includes a MAC layer and a PHY layer that conform to IEEE 802.11 for interfacing a wireless medium and supports WLAN mesh services within the WLAN mesh. (Any IEEE 802.11 entity that contains an IEEE 802.11-conformant Medium Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM), that is within a WLAN Mesh, and that supports WLAN Mesh Services)

Mesh AP: A mesh point that simultaneously performs the role of an access point. Any Mesh Point that is also an Access Point

Mesh Portal: MSDUs enter or exit the WLAN mesh from other parts of the distributed system or out of the WLAN mesh to other parts of the distributed system, or MSDUs come from a non-802.11 network. The point of entry into or out of a WLAN mesh. (A point at which MSDUs exit and enter a WLAN Mesh to and from other parts of a DS or to and from a non-802.11 network.A Mesh Portal can be collocated with an IEEE 802.11 portal)

Mesh Link: A bidirectional IEEE 802.11 data link between two associated mesh points. (A bidirectional IEEE 802.11 data link between two associated Mesh Points)

Link Metric: A criterion used to characterize the performance / quality / flexibility of mesh links. (A criterion used to characterize the performance / quality / eligiblity of a mesh link as a member of a mesh path.A mesh link metric may be used in a computation of a path metric)

Mesh Path: A series of mesh links from the origin mesh point to the destination mesh forint. (A concatenated set of connected Mesh Links from a source Mesh Point to a destination Mesh Point)

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

1 is a diagram schematically illustrating a structure of a wireless mesh network to which the present invention is applied.

Referring to FIG. 1, the wireless mesh network includes a mesh point, a mesh access point, and a station. In addition, the present wireless mesh network may include a mesh portal serving as a gateway to an external network, which is optional.

Stations STAs are connected to a mesh access point (Mesh AP) to connect to a wireless mesh network. The mesh point is a relay node constituting the mesh network, and a mesh access point (Mesh AP) is a mesh point that simultaneously performs the role of an access point.

In the wireless mesh network configured as described above, a hybrid wireless mesh protocol (hereinafter referred to as "HWMP") is used as a path selection protocol for selecting a path of a data frame.

HWMP supports two modes of operation: on-demand mode and proactive tree building mode.

The HWMP protocol used in the on-demand mode method borrows much from the Ad-hoc On-demand Distance Vector (AODV) protocol specified in IETF RFC 356. However, it is possible to set the link metric to an airtime cost.

In the proactive tree building mode, a root periodically transmits a proactive RREQ frame or RANN frame, thereby creating a path between the root and mesh points.

The route may be any one of a mesh point, a mesh access point, and a mesh portal, and which one to set the route is determined by an operator providing a wireless mesh network service. In general, the mesh portal may be used as a root in consideration of the fact that the amount of data frames transmitted to the mesh portal serving as a gateway to the external network is higher than that of other mesh points.

The route uses a proactive Route-Request (RREQ) mechanism or a proactive Root Annoucement (RANN) mechanism to establish a route to reach the route at each mesh point and mesh access point.

That is, the route periodically transmits a proactive RREQ frame or a proactive RANN frame, and the mesh points receiving the retransmissions of the proactive RREQ frame or the proactive RANN frame generate a path between the root and the mesh points.

At this time, a proactive RREQ frame or a proactive RANN frame includes a hop count field. When reproducing a proactive RREQ frame or a RANN frame at each mesh point, the hop count field is increased by 1 and transmitted. do.

Mesh points recognize as their parent the mesh point that sent the smallest metric among the proactive RREQ frames or RANN frames sent from the root as their parent, and the parent is the next hop to the root. hop). In addition, the hop count in the received proactive RREQ frame or the proactive RANN frame is the depth from the root. In this way, each mesh point knows the path to the root, the parent of the next hop.

In the proactive RREQ mechanism or the proactive RANN mechanism, the path between the route and the mesh points may be updated due to the change of the mesh point constituting the wireless mesh network, or the like.

HWMP supports four scenarios.

1) The scenario of the first HWMP has no route, and assumes that there is a destination inside the mesh. 2) The second scenario of HWMP is when there is a non-root mesh portal and the destination is outside the mesh. 3) The scenario of the third HWMP assumes that there is a mesh portal that is the root, and the destination to communicate with exists outside the mesh. 4) The scenario of the fourth HWMP is that a route exists, and the destination is inside the mesh. Imagine it exists.

Here, the first and second scenarios are route selection to the destination by HWMP's on-demand mode, and the third scenario is route selection to the destination by HWMP's proactive tree building mode.

In the fourth scenario, first, a tree path via a route is selected by HWMP's proactive tree building mode, and then an on-demand mode of HWMP achieves an optimal path selection between a source and a destination.

FIG. 2 is a diagram for describing a scenario in which an optimal path between a starting point and a destination is selected by an on-demand mode of the HWMP after the tree path via the route is selected by the proactive tree building mode of the HWMP.

Referring to FIG. 2, a case in which mesh point 4 wants to communicate with mesh point 9 will be described.

First, all mesh points know the route to the route through a RANN message broadcast from mesh point 1, which is the route. This means that a hierarchical tree path is created between the mesh points and the root.

The transmitting station STA1 is connected to mesh point 4, which is the starting mesh point, and the receiving station STA2 is connected to mesh point 9, which is the destination mesh point.

When the transmitting station STA1 sends a data frame to the receiving station STA2, the source mesh point MP4 checks its local forwarding table to retrieve the active forwarding path to the destination mesh point MP9.

In the absence of an active forwarding path, the origin mesh point MP9 may immediately send a data frame to the proactive path towards mesh point 1, which is the root.

When mesh point 1, which is the root, receives the data frame, the route forwards the received data frame to the destination mesh point MP9 along the preactive path. That is, the data frame is transferred from the root to the destination mesh point MP9 via mesh point 6 on the tree path.

3 illustrates a format of a data frame according to an embodiment of the present invention.

Referring to FIG. 3, a TTL (Time To Live) field exists in a mesh header field of a data frame. The TTL field is decremented by '1' each time a data frame is forwarded from one mesh point to another. In the mesh point where the data frame is first generated, that is, the source point, the TTL field has a default value of HWMP-NET-DIAMETER, and the value is 20.

When the destination mesh point (MP9) receives a data frame, it sends a Route-Request (RREQ) frame to the source mesh point (MP4) in an on-demand mode in order to find the optimal path than the proactive tree path via the route. Can transmit

4 is a diagram illustrating a format of an RREQ frame according to an embodiment of the present invention, and FIG. 5 is a diagram illustrating each field of the RREQ frame shown in FIG. 4.

In the on-demand mode scheme, the destination mesh point MP9 connected to the receiving station STA2 floods the RREQ frame toward the source mesh point MP4, and the source mesh point MP4 is the RREQ frame. In response to this, unicast the Route-Reply (RREP) frame to the destination mesh point (MP9) in response.

Here, flooding an RREQ frame means that the mesh point receiving the RREQ frame retransmits the RREQ frame to other mesh points except for the mesh point that has transmitted the RREQ frame to itself.

The above-mentioned RREQ frame corresponds to a management frame defined in IEEE 802.11e. In IEEE 802.11e, a management frame uses voice traffic, which is the highest priority traffic, as an access category. This is intended to access the channel sooner.

For this reason, RREQ frames are more likely to collide than normal data frames. In particular, as the number of adjacent mesh points increases, the probability of collision of RREQ frames becomes higher. In addition, since the RREQ frame corresponds to a broadcast frame, when a collision occurs, retransmission and binary backoff policy are not used.

For this reason, when collisions between RREQ frames increase, the probability of selecting an optimal path in HWMP decreases, and the path selection time increases in the on-demand mode.

An embodiment of the present invention proposes a new RREQ frame flooding technique to solve this problem.

First Example

According to a first embodiment of the present invention, a mesh point receiving an RREQ frame does not immediately retransmit the received RREQ frame.

More specifically, when an RREQ frame is broadcast from a particular mesh point, the mesh points that receive the broadcasted RREQ frame perform a layer comparison between the mesh point that transmitted the RREQ frame to itself and the mesh that transmitted the RREQ frame. Check that the point corresponds to your parent.

As the tree is constructed by the proactive tree building mode, the mesh points know the next hop to the root, which is the parent of the mesh point.

In the proactive tree structure, when the mesh point transmitting the RREQ frame corresponds to the parent of the mesh point receiving the RREQ frame, that is, in other words, the mesh point receiving the RREQ frame transmits the RREQ frame. In the case of being a child of the mesh point, the mesh point receiving the RREQ frame does not immediately rebroadcast the received RREQ frame, but rebroadcasts the RREQ frame after a certain waiting time has elapsed.

This is because the probability that the mesh point to communicate with is a child of the child is relatively low. If the mesh point to communicate with is a child, communication without needing to flood the RREQ frame is required. This is because you can unicast the RREQ frame to the mesh point you want to use.

In contrast, in a proactive tree structure, if the mesh point receiving the RREQ frame does not correspond to a child of the mesh point sending the RREQ message, the mesh point receiving the RREQ message immediately broadcasts the RREQ message. do. In this way, the possibility of collision between RREQ messages can be reduced.

2nd Example

The second embodiment of the present invention indicates that the destination mesh point can know the number of hops from the source mesh point to the destination mesh point through a data frame delivered to it via the route on the proactive tree structure. I use it.

In the fourth scenario of the HMWP, the source mesh point passes the data frame to the destination mesh point along the proactive tree path via the route, where the source mesh point uses the value of the Time To Live (TTL) field within the data frame. After setting a specific default value (called 'N'), the data frame is sent to the destination mesh point. In IEEE 802.11s, the default value of the TTL field is fixed to 20, which is HWMP_NET_DIAMETER. The field value of the TTL field is decremented by one each time through one mesh point (including the root).

In one embodiment of the present invention, the destination mesh point identifies the field value of the TTL field of the received data frame. If the TTL field value of the received data frame is M, the value of the reduced TTL field becomes N-M, that is, 20-M while the data frame is transmitted from the source mesh point to the destination mesh point in the proactive tree structure. In this case, 20-M, which is a value of the reduced TTL field, may correspond to the number of hops from the source mesh point to the destination mesh point.

That is, the destination mesh point calculates a difference value between the field value of the TTL field set in the receiving mesh point and the TTL field value of the data frame arriving at the destination mesh point. The destination mesh point sets the calculated difference value to the TTL field value of the RREQ frame, and then broadcasts the RREQ frame toward the source mesh point in an on-demand manner.

This is because, when selecting the optimal path in the on-demand mode, it is pointless to find a path having a hop number larger than the hop number of the path from the source mesh point to the destination mesh point in the proactive tree structure.

That is, in one embodiment of the present invention, when broadcasting an RREQ frame at a destination mesh point, instead of using a fixed HWMP_NET_DIAMETER value as a field value of a TTL field, it corresponds to the number of hops from the source mesh point to the destination mesh point. Used by setting the value to the TTL field value.

As such, since the value of the TTL field of the RREQ frame is reduced to a value corresponding to the number of hops from the source mesh point to the destination mesh point, the RREQ frame is hopped from the source mesh point to the destination mesh point in the IEEE 802.11s wireless mesh network. It can be prevented from being flooded more than a number, thereby reducing the possibility of collision of the RREQ frame.

The third Example

The third embodiment of the present invention is based on the fact that the mesh points can know the number of hops from the root to itself.

First, assume that the number of hops from the destination mesh point to the root is m.

When a data frame is received from the source mesh point to the destination mesh point using the proactive tree path, the destination mesh point checks the TTL field value of the received data frame to determine the number of hops from the source mesh point to the destination mesh point. To calculate.

That is, as described in the second embodiment, the number of hops from the source mesh point to the destination mesh point corresponds to the difference value of the TTL field value of the data frame reaching the destination mesh point in HWMP-NET-DIAMETER (= 20). .

If the number of hops from the starting mesh point to the destination mesh point is h, the destination mesh point calculates the difference between the hop number from the starting mesh point to the destination mesh point, h, and the number of hops from the starting mesh point to the root, and thus the starting mesh point. Check the hop count from to root. That is, the number of hops from the starting mesh point to the root is h-m.

The destination mesh point sets the maximum value of the hop number from the source mesh point to the route, i.e., h-m, and the maximum number of hops from itself and the route, m, to the depth value. That is, the depth value may be expressed by the following equation.

depth = Max {hops from origin mesh point to route (h-m), hops from route to destination mesh point (m)}

The destination mesh point is a depth value of max (hm, which is a depth value in the reserved 6 bits (Bit2 to Bit7) of the Per Destination Flags field (see FIGS. 4 and 5) of the RREQ frame when broadcasting the RREQ frame on-demand. m) Add the value and send it.

The mesh points that receive the broadcasted RREQ frame from the destination mesh point compare the depth value included in the Per Destination Flags field of the RREQ frame with the number of hops from the root to itself.

If the number of hops from the root to itself is less than or equal to the depth value, the mesh point retransmits the received RREQ frame. On the contrary, if the number of hops from the root to itself is larger than the depth value, the corresponding mesh point is not retransmitted to the RREQ frame.

This is because if the number of hops from the root to the mesh point is larger than the depth value, retransmitting the RREQ frame to the mesh point is not likely to help in selecting an optimal path, and may increase only the possibility of collision of the RREQ frame.

Although embodiments of the present invention have been described for each of the three embodiments, the technical idea of the present invention may be implemented by combining any two embodiments of the above-described first to third embodiments or by combining all three embodiments. .

In the above description of the preferred embodiment of the present invention, the present invention is not limited to the above-described specific embodiment, it is common in the art to which the invention belongs without departing from the spirit of the invention claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

As described above, according to one embodiment of the present invention, there is an advantage that the optimal path can be selected more efficiently by improving the hybrid wireless mesh protocol.

Claims (29)

One mesh point transmitting a Route-Requset (RREQ); Receiving another RREQ by another mesh point located in a proactive tree in a proactive tree building mode; And If the one mesh point corresponds to a parent of the other mesh point, the other mesh point retransmits the RREQ after a randomized time elapses, and the one mesh point corresponds to the other mesh point. If not the parent, the other mesh point immediately retransmits the RREQ; communication method in a wireless network comprising a. When receiving a Route-Request (RREQ) from a parent on the proactive tree created by the proactive tree building mode, retransmits the RREQ after a randomized time, and the one And if the mesh point of does not correspond to the parent of the other mesh point, immediately retransmits the RREQ. When receiving a Route-Request (RREQ) from a parent on the proactive tree created by the proactive building mode, retransmits the RREQ after a randomized time, and the one A mesh point that immediately retransmits an RREQ if the mesh point does not correspond to the parent of the other mesh point. Transmitting, by one mesh point, a route-request (RREQ) including a variable time to live (TTL) value toward a specific mesh point; And One or more Another mesh point receiving the Route-Request (RREQ) and not retransmitting or retransmitting the Route-Request (RREQ). The method of claim 4, wherein the specific mesh point, A mesh point located on a proactive tree generated by a proactive tree building mode, wherein the one mesh point is a mesh point to set an optimal path according to an on demand mode. How to communicate on the network. The method of claim 4, wherein The variably selected TTL value is, A total number of hops between a particular mesh point and the one mesh point via the root of the proactive tree generated by the proactive tree building mode. The method of claim 6, The total number of hops between the particular mesh point and the one mesh point is When data is transmitted from the specific mesh point to the one mesh point along a proactive tree path generated by the proactive tree building mode, a TTL value set for the data at the specific mesh point and the one mesh point. Communication method in a wireless network, characterized in that the difference between the TTL value of the data received from. One mesh point variably selecting a time to live (TTL) value of a route-request (RREQ); And And transmitting the RREQ including the selected TTL value toward a specific mesh point. The method of claim 8, wherein the specific mesh point, A mesh point located on a proactive tree generated by a proactive tree building mode, wherein the one mesh point is a mesh point to set an optimal path according to an on demand mode. Method of communicating mesh points in a network. The method of claim 8, The selected TTL value is, The total number of hops between the particular mesh point and the one mesh point via the root of the proactive tree generated by the proactive tree building mode. The method of claim 10, The total number of hops between the particular mesh point and the one mesh point is When data is received from the specific mesh point to the one mesh point along a proactive tree path, an initial TTL value included in the data at the specific mesh point and a TTL value of the data received at the one mesh point The communication method of the mesh point in the wireless network, characterized in that the difference value of. A mesh point that selects a time-to-live (TTL) value of a route-request (RREQ) as one variable and transmits an RREQ including the selected TTL value toward a specific mesh point. The method of claim 12, wherein the specific mesh point, A mesh point located on a proactive tree generated by a proactive tree building mode, wherein the mesh point is a mesh point for setting an optimal path according to an on demand mode. The method of claim 12, Selecting the total number of hops through the root of the proactive tree generated by the proactive tree building mode from the specific mesh point as the TTL value of the RREQ. The method of claim 13, The number of hops from the particular mesh point is When data is received from the specific mesh point along a proactive tree path generated by the proactive tree building mode, a difference value between an initial TTL value included in the data and the TTL value of the received data at the specific mesh point The mesh point characterized by being. Transmitting, by one mesh point, a route-request (RREQ) including a depth toward a specific mesh point; Another mesh point located in a proactive tree in a proactive tree building mode may include: receiving the RREQ; And The other mesh point does not retransmit the RREQ when the depth from the root of the proactive tree is greater than the depth of the RREQ, and the depth from the root of the proactive tree is the depth of the RREQ. Retransmitting an RREQ if less than or equal to the depth of the RREQ. The method of claim 16, wherein the specific mesh point, Located in the Proactive Tree created by Proactive Tree Building Mode, And the one mesh point is a mesh point for setting an optimal path according to an on demand mode. The method of claim 16, The depth included in the RREQ is a maximum value of a depth from the specific mesh point to the root of the proactive tree and a depth from the root to the one mesh point. Receiving a Route-Request (RREQ) including a depth transmitted from one mesh point toward a specific mesh point; And If the depth from the root on the preactive tree created by the proactive tree building mode is greater than the depth included in the RREQ, the depth from the root is included in the RREQ without retransmitting the RREQ. Retransmitting if smaller than the depth, or the same as the depth included in the RREQ; Communication method of the mesh point in a wireless network comprising a. The method of claim 19, Depth included in the RREQ, And a maximum value of a depth from the specific mesh point to a root on the proactive tree and a depth from the root to the one mesh point. Receive a Route-Request (RREQ) including a depth transmitted from one mesh point toward a specific mesh point, If the depth from the root on the preactive tree created by the proactive tree building mode is greater than the depth included in the RREQ, do not retransmit the RREQ, A mesh point for retransmitting an RREQ if the depth from the root is smaller than the depth included in the RREQ or is equal to the depth included in the RREQ. The method of claim 21, wherein the specific mesh point, Located on the proactive tree generated by the proactive tree building mode, The mesh point, characterized in that the one mesh point is a mesh point to set the optimum path according to the on demand mode (On demand mode). The method of claim 21, And a depth included in the RREQ is a maximum value of a depth from the specific mesh point to a root on the proactive tree and a depth from the root to the one mesh point. Including a depth in the Route-Request (RREQ), and transmitting the RREQ including the depth toward a specific mesh point; Communication method of the mesh point in a wireless network comprising a. The method of claim 24, wherein the specific mesh point, Located on the tree created by Proactive Tree Building Mode, The mesh point is a communication method of the mesh point in a wireless network, characterized in that the mesh point to set the optimum path according to the on demand mode (On demand mode). The depth of claim 24, wherein the depth included in the RREQ includes: And a maximum value of the depth from the specific mesh point to the root on the preactive tree in the proactive tree building mode and the depth from the root to the mesh point. A mesh point including a depth in a route-request (RREQ) and transmitting the RREQ toward a specific mesh point. The method of claim 27, wherein the specific mesh point, Located on the proactive tree generated by the proactive tree building mode, The mesh point is a mesh point, characterized in that the mesh point to set the optimum path according to the on demand mode (On demand mode). The depth of claim 27, wherein the depth included in the RREQ includes: And a maximum value of the depth from the specific mesh point to the root on the preactive tree in the proactive tree building mode and the depth from the root to the mesh point.

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