KR20090020004A - Multicasting / Broadcasting Procedures in Wireless Mesh Networks - Google Patents

Abstract

Disclosed is a broadcasting procedure in a wireless mesh network. In the broadcasting procedure according to an embodiment of the present invention, as a broadcasting procedure in a wireless mesh network in which a parent-child relationship is established between a plurality of wireless devices, a person who receives a broadcasted data frame ( Child) The wireless device judges whether the sender of the data frame is the same as its parent wireless device, and if it is determined that the sender and the parent wireless device are the same, the wireless device restarts the received data frame. Broadcast; otherwise, rebroadcasting is not performed. Here, the rebroadcasted data frame may have a format that can be recognized by all other wireless devices and wireless stations connected to the own wireless device, and the wireless device may only have data once even when there is a wireless station connected to the wireless device. Broadcast the frame. One example of such a hat relationship may be a hat relationship in a proactive pathway.

Description

Multicasting / broadcasting procedure in wireless mesh network

The present invention relates to a wireless mesh network, and more particularly, to a multicasting / broadcasting procedure in a wireless mesh network.

A wireless mesh network is a network that supports a plurality of wireless devices having a relay function to communicate directly without passing through an access point (AP). In a wireless mesh network, one wireless device may be connected to a plurality of other wireless devices to have a plurality of communication paths. Such a wireless device is called a mesh point (MP), but is not limited thereto. In addition to the relay function described above, the MP performs a function of an access point (Access Point, AP) together is called a mesh access point (Mesh Access Point, MAP).

Such a wireless mesh network has advantages such as flexibility in network construction, reliability by a bypass path, and power consumption reduction due to a shortening of a communication distance. More specifically, using a wireless mesh network it is possible to build a flexible network between the MP even in a place without the existing communication network. In the wireless mesh network, a plurality of MPs may be connected to each other to secure a plurality of bypass paths, so that even if one MP fails, data may be transmitted through another path. In the wireless mesh network, even though the coverage of one MP is not wide, communication is possible through adjacent MPs, thereby enabling long-distance communication even with low power.

Meanwhile, message transmission in wireless communication may be classified into unicast, multicast, and broadcast according to the number of target devices or destination terminals. Unlike unicast, in which a target device of a transmission message is one terminal, in multicast, a target address of a transmission message is specified as a multicast group address. And broadcast is a special multicast in which the group address specifies all terminals. Therefore, even when hereinafter referred to simply as 'broadcast,' it may be interpreted to include multicast together except when it is impossible to apply due to its nature.

In the conventional wireless mesh network, a simple flooding method is used when broadcasting data frames. 'Simple Flooding Method' means that an MP (or MAP) receiving a broadcasted data frame re-broadcasts the received data frame for another MP in the same network and / or a wireless station (STA) connected to it. Say how.

However, in such a simple flooding method, the same data frame may be repeatedly broadcast indefinitely. For example, if the MP receives back a data frame that it has already broadcast, there is a possibility that the MP will repeatedly broadcast the same data frame. It is also possible that one data frame may be broadcast numerous times by multiple MPs.

In order to prevent this problem, the conventional simple flooding method uses a sequence number and a time to live (TTL). More specifically, in the conventional broadcasting procedure, a mesh header is defined in a data frame transmitted for the MP, and the mesh header includes a TTL indicating a sequence number of the data frame and the remaining hops. The sequence number is used to determine whether the broadcast data frame received by the MP and the data frame already broadcast by the MP are the same broadcast frame. This prevents the MP from broadcasting the same data frame again. The TTL is used to impose a restriction on the total number of hops (number of hops) in which the same data frame is broadcasted by a plurality of MPs sequentially. When using this, the same data frame is broadcasted more than the set number of hops. You can prevent it.

However, the method of limiting the total number of broadcasts using the TTL has a problem that the same data frame is repeatedly broadcast within the range allowed by the TTL regardless of the configuration or characteristics of the network. This may cause a decrease in the efficiency of the network, because if the number of MPs or STAs constituting the network is small, an unnecessary number of broadcasts may be performed.

In addition, the conventional broadcasting procedure of controlling the number of broadcasting using the sequence number and the TTL causes a problem that the MAP performs two multicasts for the same data frame. The reason why MAP performs multicast twice is that the data frame including the mesh header is not recognized by the wireless station (STA). Finally, according to the conventional broadcasting procedure, the MAP broadcasts a data frame including a mesh header once for another MP and also broadcasts a data frame without a mesh header once again for an STA connected to it. .

FIG. 1 is a diagram for describing a conventional broadcasting procedure using the simple flooding method and a problem thereof in more detail.

Referring to FIG. 1, the MP 12 broadcasts its received broadcast data frame for another MP or MAP 14. In this case the broadcast data frame includes a mesh header. As such, broadcasting of a data frame including a mesh header may be referred to as, for example, mesh broadcast. Since the MP 12 does not have an STA associated with itself, the MP 12 does not separately broadcast a data frame without a mesh header.

On the other hand, the MAP 14 receiving the data frame from the MP 12 first broadcasts a data frame with a mesh header for another MP or MAP 16 (Mesh Broadcast). The MAP 14 also broadcasts a data frame without a mesh header for the STA 24 connected to it. As such, broadcasting a data frame without a mesh header is referred to as a basic service set broadcast (BSS Broadcast). The order of mesh broadcast and BSS broadcast is not particularly limited. That is, the MAP 14 broadcasts data of the same content twice in mesh broadcast and BSS broadcast in different formats. The MAP 16 that receives the data frame from the MAP 14 also performs a mesh broadcast for another MP or MAP 18 and a BSS broadcast for the STA 26, similarly to the MAP 14.

As a result, according to the conventional broadcasting procedure, data frames may be continuously broadcast within a range not exceeding the TTL limit regardless of network characteristics, which may cause a problem of degrading the performance of the wireless mesh network. In addition, since the MAP must broadcast a data frame including a mesh header and a data frame without a mesh header, the MAP not only degrades the performance of the wireless mesh network but also increases the data processing burden of the MAP.

Meanwhile, in a wireless mesh network, multicast / broadcast is frequently used to find a forwarding path or to stream multimedia. If the mesh point receives a multicast / broadcast frame in the idle channel state, the mesh point is received immediately after a certain time, for example, a distributed inter-frame space (DIFS) time without backoff. Relayed frames. In this case, if multiple mesh points receive the frame, collision probability of relayed multicast / broadcast frames is very high since all mesh points are likely to multicast / broadcast the frame. . In this case, there is a problem that the reliability of multicast / broadcast in a wireless mesh network is greatly reduced.

An object of the present invention is to provide a broadcasting procedure in a wireless mesh network that can improve the performance of the wireless mesh network.

Another technical problem to be solved by the present invention is to provide a broadcasting procedure in a wireless mesh network that can alleviate the burden of MAP performing broadcasting.

Another technical problem to be solved by the present invention is to provide a broadcasting procedure in a wireless mesh network which can improve the reliability of multicast / broadcast.

The broadcasting procedure in the wireless mesh network according to the embodiment of the present invention for achieving the above technical problem is a broadcasting procedure in a wireless mesh network in which a parent-child relationship is established between wireless devices. The child wireless device that receives the broadcasted data frame determines whether the sender of the data frame is the same as its parent wireless device, and only if the sender and the parent wireless device are the same. And rebroadcasting the received data frame by the wireless device. The wireless device may be MP or MAP.

According to an aspect of the present embodiment, the rebroadcasted data frame may have a format that can be recognized by all other wireless devices and wireless stations connected to the own wireless device. The wireless device may broadcast the data frame only once even when there is a wireless station connected to the wireless device. In addition, the hat relationship between the wireless devices may constitute a proactive path of the wireless mesh network. Determining whether the sender of the data frame is the same as its parent wireless device may use information included in the sender address field of the data frame.

Broadcasting procedure in a wireless mesh network according to another aspect of the present invention for achieving the above technical problem is a broadcasting procedure in a wireless mesh network in which a proactive path is established, the root radio is broadcast as a target address Among the wireless devices that transmit a first data frame having an address and receive the first data frame, only the first wireless device that is a child wireless device of the root wireless device in the proactive path is the broadcast address. Transmit a second data frame having the same broadcast address as.

According to an aspect of the embodiment, out of the wireless devices that receive the second data frame, only the second wireless device that is the own wireless device of the first wireless device in the proactive path is the same as the broadcast address as the target address. The third data frame having the broadcast address may be transmitted.

In the broadcasting procedure according to the embodiment of the present invention, the MP or the MAP that receives the multicast data frame rebroadcasts it only when the sender of the data frame is its own MP, thereby saving resources of the wireless mesh network. Not only can it be efficiently managed, but it can also prevent data frames from being repeatedly broadcast unnecessarily.

And according to the broadcasting procedure according to the embodiment of the present invention, the MP or MAP does not need to broadcast the same data frame twice in different formats. Therefore, according to the present embodiment, it is possible to alleviate the overhead of MAP in which the data frame including the mesh header and the data frame without the mesh header must be broadcast twice. In addition, since a data frame in a format including a mesh header is no longer needed as a broadcast data frame, a simple broadcasting procedure can be implemented.

In addition, according to the multicasting / broadcasting procedure according to an embodiment of the present invention, mesh points receiving a multicast / broadcast frame are received after performing a backoff for each arbitrary time interval even if the channel is idle. Multicast / broadcast the captured frames again. Therefore, according to this embodiment of the present invention, by preventing collision between multicast / broadcast frames relayed by mesh points, it is possible to improve the reliability of multicast / broadcast.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like numbers refer to like elements throughout the specification. In the following embodiment, only the broadcasting procedure in the wireless mesh network will be described. However, the technical idea of the present invention included in the following embodiments may be equally applicable to the multicasting procedure in the wireless mesh network, except that the present invention is not applicable.

FIG. 2 is a diagram illustrating an example of a configuration of a wireless mesh network constituting an extended service set (ESS). Referring to FIG. 2, a wireless mesh network includes a plurality of STAs 110a through 120h and one or more MPs 120a, 120b, 120c, 120d and 130. Among the MPs, reference numerals 120a, 120b, 120c, and 120d exist as MPs, that is, MAPs, which simultaneously perform functions of an AP because there is an STA connected with the self. The MPs 120a and 120b are entities connected to an external network through a wired or wireless distribution system (DS) 140, which is referred to as a root MP.

The STAs 110a through 120h are arbitrary functional media including medium access control compliant with the IEEE 802.11 standard and a physical layer interface to a wireless medium, and are non-AP stations. )to be. The STAs 110a to 120h subscribe to the broadcast service and receive data frames broadcast by the MAPs 120a, 120b, 120c or 120d that they have established. Such a STA may also be called a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), or a mobile subscriber unit (Mobile Subscriber Unit) in addition to a radio station. Can be.

The MPs 120a, 120b, 120c, 120d, and 130 are entities that constitute a wireless mesh network. The MPs 120a, 120b, 120c, 120d, and 130 are members of a wireless mesh network. It is a functional object. The MPs 120a, 120b, 120c, 120d, and 130 are wireless devices that support mesh services, and a mesh service refers to a service that enables direct communication between MPs constituting a mesh network. To this end, the MP relays broadcast frames for other MPs, and may also relay unicast frames or multicast frames. In particular, according to the present invention, the MP receives only the multicast data frame from its parent MP through its established proactive path. Broadcast for Child MP. This will be described in detail later.

As described above, an MP that performs a function as an AP among MPs is specifically referred to as MAP. Therefore, the MAPs 120a, 120b, 120c, and 120d also perform the function of the AP for the associated station which is connected to itself in addition to the functions of the aforementioned MP. The AP may be called a centralized controller, a base station (BS), a node-B, or a site controller in addition to an access point. In addition, according to the present invention, unlike the conventional MAP (120a, 120b, 120c, 120d) is broadcast only once for the MP and STA using the same format data frame, which will be described in detail later.

Next, a message transmission path between MPs in a wireless mesh network will be described. One of the path selection protocols that can be used in the wireless mesh network is the heterogeneous wireless mesh protocol (HWMP). HWMP is a mesh path selection protocol that combines the flexibility of on-demand path selection with proactive paths. Thus, HWMP enables optimal and efficient path selection in various types of mesh networks.

HWMP supports two modes of operation, depending on its configuration: on-demand mode and Proactive Tree Building Mode. In the on-demand mode, the MP can communicate using a peer-to-peer path. This mode is typically used in configurations without a root MP, but can be used if it can provide a better path even with a root MP. According to the proactive tree building mode, a route is established using a mechanism that uses a frame that the root MP periodically broadcasts, such as a Path Request (PREQ) mechanism or a Root Announcement (RANN) mechanism. This path is periodically updated by the same mechanism. Hereinafter, the paths selected according to the on-demand mode and the proactive tree building mode will be referred to as on-demand paths and proactive paths, respectively.

The proactive path is a structure in which the message transmission path is branched like a tree branch from the root MP, and the message transmission path between the MPs is periodically set by parent-child relation. The mother-child relationship is a tree-shaped path that is continuously connected in order to grandparents-children-grandchildren among the plurality of MPs starting from the root MP. The method for establishing a proactive path is not particularly limited, and for example, a PREQ mechanism or a RAAN mechanism may be used.

On the other hand, the on-demand path is an arbitrarily established path between MPs when a message needs to be transmitted. When establishing an on-demand route, for example, the Ad hoc On-demand Distance Vector (AODV) protocol can be used. The on-demand route does not need to pass through the root MP, for example, at that point, the shortest route or link metric between the source MP and the target MP may be set to the best route.

According to the HWMP, since the proactive tree building mode and the on-demand mode are not mutually exclusive, the above-described proactive path and the on-demand path can be used in combination with each other. For example, a data frame that the source MP first transmits to the target MP may be sent along the proactive path. In this case, data frames are transmitted from the source MP to the root MP along the upstream path of the proactive path, and data is transmitted from the root MP to the target MP along the downstream path of the proactive path. The target MP can then find the on-demand path towards the source MP and then use this on-demand path to send another data frame.

3 is a diagram for illustrating the above-described message transmission path in a wireless mesh network, in which a proactive path and an on-demand path from MP 4 to MP 9 are shown, respectively.

Referring to FIG. 3, the proactive path from MP④ to MP⑨ is composed of an 'upward path' leading from MP④ to MP①, the root MP, and a 'downward path' leading from MP① to MP⑨ from MP①, the root MP. . Here, the upward path is a path from the child MP to the parent MP (for example, from MP④ to MP③, from MP③ to MP②, and from MP② to MP①), and refers to the path whose end point is the root MP, and the downward path is from the parent MP. The path to the MP (for example, from MP① to MP⑥ and from MP⑥ to MP⑨) refers to a path whose starting point is the root MP. The on-demand route from MP④ to MP⑨ may be, for example, a path from MP④ to MP⑨ through MP⑦. Such a path is one of temporary paths for message transmission from MP④ to MP⑨ or from MP⑨ to MP④.

The broadcasting procedure according to the present invention utilizes a proactive path preset in the corresponding network. More specifically, the present invention utilizes the hat relationship in the proactive path, more specifically the down path, to prevent the same data frame from being continuously rebroadcasted. According to the present invention, when the source of a data frame to be broadcast is an STA, the data frame is transmitted to the root MP using an uplink path of a proactive path so that the data frame can be broadcast along a downlink path. do. In addition, in the present invention, by broadcasting a data frame in a format that both the MP and the STA can recognize, the MAP also broadcasts the data frame only once. This will be described below in detail.

4 is a flowchart illustrating a broadcasting procedure according to an embodiment of the present invention. This procedure is performed inside one MP (or MAP).

Referring to FIG. 4, an MP receiving a broadcast data frame, that is, a data frame having a broadcast address, has a sender address of the data frame and an address of its parent MP in the proactive path. It is determined whether or not the same (S11). According to one aspect of this embodiment, the functional entity that starts broadcasting the data frame in the ESS is the root MP. That is, according to the present embodiment, broadcasting is started by the root MP, and the broadcast data frame may be received from an external network through a DS or may be requested by a STA in the same ESS.

If it is determined that the sender address is not the same as the address of the parent MP, the MP terminates the procedure without further broadcasting the received data frame. However, if it is determined in step S11 that the sender address and the address of the mother MP are the same, the MP rebroadcasts the received data frame (S12). In this case, the data frame is broadcast only once regardless of whether the MP is MAP. That is, even when the MP is a MAP having a STA connected to the self, according to the broadcasting procedure according to the present embodiment, the MP broadcasts a data frame received only once.

As described above, according to the present embodiment, the MP receiving the broadcast data frame rebroadcasts the data frame when the sender of the received data frame is its parent MP in the proactive path, but not in the parent MP. Do not rebroadcast. When determining whether to rebroadcast, it only checks whether the sender of the data frame is its own MP, and does not use the TTL and / or sequence number included in the received data frame. Therefore, a mesh header for including a TTL and / or sequence number does not need to be inserted into a broadcasting data frame. According to this embodiment, in particular, the MAP is sufficient to broadcast only once using a data frame having a format that both the MP and the STA can recognize.

5 is a block diagram illustrating an example of a format of a data frame used in a broadcasting procedure according to the present invention. As described above, the data frame 200 of FIG. 5 is a format that both the MP and the STA can recognize and do not include a mesh header. Referring to FIG. 5, the data frame 200 includes a frame control field (Frame Control 210), a duration field (Duration 220), a destination address field (Destination Address 230), and a sender address field (Sender Address 240). Source address field (Source Address 250), sequence control field (Sequence Control, 260), QoS control field (QoS Control, 270), frame body field (Frame Body, 280) and / or frame check sequence field (FCS, 290). However, according to the present embodiment, the sequence control field 260 is an arbitrary component because the sequence number is not required unlike the conventional art.

The frame control field 210 includes information necessary for controlling, managing, transmitting / receiving a corresponding frame, such as a protocol version, type, power management, and DS. The duration field 220 may include information such as a time required for transmitting one data frame. The target address field 230 includes the address of the final target STA of the data frame 200. In this embodiment, the target address field 230 includes a broadcast address.

The sender address field 240 includes the address of the MP for transmitting the data frame 200. In this embodiment, the sender of the data frame 200 uses the address of the sender address field 240. Determine if it is MP. The source address field 250 includes an address of a device or an STA that first requested the transmission of the data frame 200. For example, when the wireless device that requests the transmission of the data frame 200 is an STA, medium access control (Medium) of the STA is performed. Access Control (MAC) address is included. The sequence control field 260 includes information such as a fragment number of the corresponding data frame 200 among all broadcasted data sequences.

In addition, the QoS control field 260 includes information for identifying a traffic category (TC) or a traffic stream (TS) to which the data frame 200 belongs, various information related to QoS, and the like. The frame body field 28 includes all or part of data to be transmitted. The frame check sequence field 290 contains information for checking whether there is an error in the received data frame 200. For example, the frame check sequence field 290 may include a 32-bit Cyclic Redundancy Check (CRC) code.

6 is an example of an ESS block diagram illustrating a proactive path of a wireless mesh network for explaining a broadcasting procedure according to another embodiment of the present invention. In FIG. 6, one STA 352 and multiple MPs are shown, which is for convenience of description only. For example, one or more STAs may be connected to all or part of the MP, and in this case, the MP may be a MAP.

And the broadcasting procedure according to the embodiment of the present invention utilizes a predetermined proactive path, and broadcasting of data frames always starts from the root MP 300. An example of a format of a data frame broadcast from the root MP 300 has been described above with reference to FIG. 5, and thus description thereof is omitted here.

According to the present embodiment, there is no particular limitation on the path through which the root MP 300 acquires data included in the data frame to start broadcasting. For example, root MP 300 may receive data to broadcast from another network via DS. In addition, when there is data to be broadcast by an internal radio station of the mesh network, the root MP 300 may receive data to be broadcast from the radio station, for example, the STA 342. In this case, when the STA 342 transmits data to broadcast to the AP 322 to which the connection is made, the AP 322 transmits data to be broadcast using the uplink path of the proactive path to the root MP 300. To). That is, data to be broadcast is transmitted from the STA 342 to the root MP 300 via the MAP 322 and the MP 312.

FIG. 7 is a block diagram illustrating an example of a format for a data frame used when the STA 342 transmits data requesting broadcasting from the MAP 322 to the root MP 300. The data frame of this format may be transmitted from the MAP 322 to the root MP 300 according to the unicast scheme, but is not limited thereto.

Referring to FIG. 7, the data frame 400 includes a frame control field (Frame Control, 402), a duration field (Duration, 404), a receiver address field (Receiver Address, 406), and a sender address field (Sender Address, 408). Target address field (Destination Address, 410), sequence control field (Sequence Control, 412), source address field (Source Address, 414), Qos control field (QoS Control, 416), mesh header field (Mesh Header, 418) And a frame body field (Frame Body 420), and a frame check sequence field (422, FCS). The following description will focus on differences from the format of the data frame 200 described with reference to FIG. 5.

In this embodiment, since the data is transmitted to the root MP by using the uplink path of the proactive path, the receiver address field 406 includes the MAC address of the mother MP of the data frame 400 and the target address field. 410 includes the address of the root MP. The source address field 414 may include, for example, the MAC address of the MP to which the STA requesting the broadcasting of data is connected.

Referring to FIG. 7, the mesh header 418 includes a mesh flag subfield (Mesh Flag 418a), a TTL subfield (TTL, 418b), a mesh sequence number subfield (Mesh Sequence Number, 418c), and a broadcast address sub. Field (Broadcast Address, 418d), and a source station address subfield (Source STA Address, 418e). The subfields are not all essential components, and some of them are arbitrary components. For example, the TTL subfield 418b, the mesh sequence number subfield 418c, and / or the source station address subfield 418e may be included only when there is corresponding information or is needed.

The mesh flag subfield 418a includes information indicating that the field is a mesh header, and the broadcast address subfield 418d includes the broadcast address of the data frame 400. The source station address subfield 418d is included only when the entity requesting the broadcasting of the data frame is an STA, and includes a MAC address for the STA.

Subsequently, this embodiment will be described with reference to FIG. 6.

The root MP 300 that has obtained the data to broadcast generates a data frame to multicast using the data. The generated data frame may be, for example, a data frame as shown in FIG. 4. The root MP 300 broadcasts the generated data frame. In this case, all MPs and / or STAs located in an area covered by the root MP 300 may receive a data frame broadcast by the root MP 300. The MP and / or STA may include the MPs 312 and 314 as well as other MPs.

Next, the STAs receiving the broadcast data frame check whether the sender of the corresponding data frame matches the address of the MAP that they have established, and if the addresses match, the STAs perform post-processing on the received data frame. If not, discard it. The MPs (Ref. No. 312, 314, etc.) receiving the broadcast data frame determine whether the sender address of the received data frame matches the address of their mother MP in the proactive path. If not, the received data frame is discarded. On the other hand, if the sender address of the received data frame matches the address of its parent MP in the proactive path, the MPs 312 and 314 each generate a data frame with their sender address and rebroadcast it. Cast. As such, the format for the frame to be rebroadcasted may also have the format shown in FIG. 4, for example, and the frame has a configuration that can be recognized by the STA as well as the MP.

Next, for the data frame rebroadcasted by the reference numerals 312 and 314, the same procedure as described in the data frame broadcast by the root MP 300 is performed. As a result, STAs connected to the reference numbers 312 and 314 may receive a data frame serviced by multicast. And the child MPs 312 and 314 MP in the proactive path also rebroadcast the received data frames, respectively. Subsequently, the subsequent procedure proceeds in the same manner, so that all STAs connected to all MPs of the corresponding network can receive a data frame in which broadcast service is performed.

8 is a diagram schematically showing a broadcasting procedure according to an embodiment of the present invention.

Referring to Fig. 8, root MP 32 first broadcasts a data frame. In this case, when there is no STA connected to the root MP 32, the root MP 32 broadcasting a data frame corresponds to a conventional mesh broadcast. The MAP 34 receiving the data frame broadcast by the root MP 32 broadcasts the data frame again because the sender of the data frame is his / her own MP. Although one or more STAs 44 are connected to the MAP 34, the MAP 34 broadcasts a data frame only once. Thus, broadcasting of data frames by MAP 34 includes both conventional mesh broadcasts and BSS broadcasts. Subsequently, the same process as in MAP 34 is repeated in MAP 36 and MAP 38.

Next, a channel access mechanism for relaying multicast / broadcast frames in a wireless mesh network according to an embodiment of the present invention will be described. The channel access mechanism described below can be applied to the broadcasting (multicasting) procedure according to the above-described embodiment of the present invention, as well as to the broadcasting procedure or the multicasting procedure according to the prior art. Therefore, whether or not the mesh point receiving the broadcast / multicast frame relays the received frame or according to which procedure is relayed has nothing to do with the channel access mechanism according to the embodiment of the present invention.

According to the channel connection mechanism according to the embodiment of the present invention, the mesh point always backs off the multicast / broadcast frame regardless of whether the channel is idle. This is different from existing channel access mechanisms that transmit multicast / broadcast frames received after a DIFS time without backoff when the channel state is idle. However, according to the embodiment of the present invention, the backoff is performed even when the channel state is idle, and after the backoff time expires, the multicast / broadcast frame is transmitted again after the DIFS time.

In the case of performing a backoff for relay of a multicast / broadcast frame in which a mesh point is received in a wireless mesh network according to an embodiment of the present invention, the backoff time is, for example, at [0, CW _min ]. Can be determined. According to an aspect of the present embodiment, in order to reduce the collision probability of the multicast / broadcast frame, the CW _min may be selected from the AC_BE (Access Category_Best Effort). According to another aspect of the present embodiment, when CW _min is selected in AC_VO (Access Category_Voice) or AC_VI (Access Category_Video) instead of AC_BE, a collision protection scheme may be used to reduce the collision probability of multicast / broadcast. For example, you can use a method such as exchanging Request To Send (RTS) / Clear To Send (CTS) frames.

As mentioned above, although preferred embodiment of this invention was described in detail, if it is a person with ordinary knowledge in the technical field to which this invention belongs, this invention may be carried out without deviating from the mind and range of this invention contained in a claim. It will be appreciated that various modifications or changes can be made.

1 is a view for explaining a conventional broadcasting procedure using a simple flooding method.

FIG. 2 is a diagram illustrating an example of a configuration of a wireless mesh network configuring an extended service set (ESS).

FIG. 3 is a diagram illustrating a proactive path and an on-demand path that are message transmission paths in a wireless mesh network.

4 is a flowchart illustrating a broadcasting procedure according to an embodiment of the present invention.

5 is a block diagram illustrating an example of a format of a data frame used in a broadcasting procedure according to the present invention.

6 is an example of an ESS block diagram illustrating a proactive path of a wireless mesh network for explaining a broadcasting procedure according to another embodiment of the present invention.

FIG. 7 is a block diagram showing an example of a format for a data frame used when an MP transmits data for which a radio station requests broadcasting to the root MP.

8 is a diagram schematically showing a broadcasting procedure according to an embodiment of the present invention.

Claims (7)

In a broadcasting procedure in a wireless mesh network in which a parent-child relationship is established between wireless devices, A child wireless device that has received the broadcast data frame determines whether the sender of the data frame is the same as its parent wireless device; And And determining that the own wireless device rebroadcasts the received data frame only if the sender and the parent wireless device are identical. The broadcasting procedure according to claim 1, wherein the data frame to be rebroadcasted has a format that can be recognized by both a wireless station and a wireless station to which the wireless station is connected. The broadcasting procedure as claimed in claim 1, wherein the own wireless device broadcasts the data frame only once even when there is a wireless station connected to the own wireless device. 2. The broadcasting procedure of claim 1, wherein the hat relationship between the wireless devices constitutes a proactive path of the wireless mesh network. 2. The broadcasting procedure of claim 1, wherein determining whether the sender of the data frame is the same as its parent wireless device uses information included in the sender address field of the data frame. In the broadcasting procedure in the wireless mesh network where the proactive path is established, The root radio transmits a first data frame having a broadcast address as a target address, Among the wireless devices that receive the first data frame, only the first wireless device that is a child wireless device of the root wireless device in the proactive path has a second data frame having the same broadcast address as the broadcast address. Broadcasting procedure, characterized in that for transmitting. The method of claim 6, Among the wireless devices that have received the second data frame, only the second wireless device that is the own wireless device of the first wireless device in the proactive path has the third data having the same broadcast address as the broadcast address as a target address. Broadcasting procedure, characterized in that for transmitting the frame.

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