Abstract:
A method and an apparatus to transfer a frame in an extended wireless local area network (LAN) environment into which wireless access points are introduced, the method including: grouping the wireless access points; receiving a frame; detecting destination address information from the frame; comparing the destination address information to address information of the wireless access points belonging to a group; and transmitting the frame to a wireless access point if the destination address information is identical to the address information of the wireless access points belonging to the group, to promote preventing a broadcast storm where a broadcast frame is repeatedly transmitted in a loop.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 10-2005-31505, filed on Apr. 15, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     Aspects of the invention relate to a method and an apparatus to route frames in an extended wireless local area network (LAN) environment, and, more particularly, to a method and apparatus to form an effective transmission route, grouping wireless access points, and to prevent frames from being redundantly transmitted in an extended wireless LAN environment into which the wireless access points are introduced.  
         [0004]     2. Description of the Related Art  
         [0005]     A repeater having wired and wireless interfaces is typically required to transfer data from a wired network to a mobile terminal connected to a wireless network. An access point (AP) defined by the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard generally plays the role of a repeater in a LAN.  
         [0006]      FIG. 1  illustrates a LAN environment in accordance with the IEEE 802.11 standard. Referring to  FIG. 1 , first and second access points (APs) (AP 1 , AP 2 )  130  and  140  are connected to the Internet  100  via a router  110 , receive frames having a media access control (MAC) address, which is a link layer address, from the Internet  100  or a host  120  over a wired network, and forwards the frames to first through fourth stations (STA 1 , STA 2 , STA 3 , STA 4 )  150 ,  160 ,  170 , and  180 , which are mobile terminals belonging to basic service sets (BSSs)  135 ,  145 , according to the MAC address. The coverage of a BSS is generally determined according to a radio wave that can reach an AP. A mobile station, for example, the third station (STA 3 )  170  in  FIG. 1 , can receive radio waves from two or more APs, since the coverage of two or more APs overlap. In this regard, all the stations can be linked to an AP and communicate the frames using a basic service set identifier (BSSID) in the IEEE 802.11 standard.  
         [0007]     However, an extended wireless LAN, such as a wireless mesh network, in which a mobile node is separated from a wired network and can route frames is not specified. Mobile nodes can communicate the frames in the extended wireless LAN and form an ad hoc network. In this regard, where the frames are broadcasted, a broadcast storm in which the frames are repeatedly transmitted in a loop can occur. Such a repetition of the loop can be prevented by redesigning the topology, such as a spanning tree, but can ineffectively set a frame transfer route.  
         [0008]     Further, similar to the LAN illustrated in  FIG. 1 , where the frames are transmitted to a mobile node capable of communicating with two or more portals (transfer points intermediating the wired network and the wireless network) over the wired network in an extended wireless LAN, the AP to forward the frames has not been addressed in relation to providing an effective transmission route.  
       SUMMARY OF THE INVENTION  
       [0009]     Several aspects and exemplary embodiments of the invention provide a method and an apparatus to group wireless access points, to set an effective transmission route, and to prevent frames from being redundantly transmitted in an extended wireless LAN environment.  
         [0010]     According to an aspects of the invention, there is provided a method of routing a frame received over a wired network to a wireless network including mobile nodes (MNs) having a frame routing function, by a routing device to interconnect both the wired and wireless networks, the method including: detecting destination address information included in the frame; comparing the detected destination address information with address information of MNs belonging to a group which the routing device manages; and selectively transferring the frame to the MNs belonging to the group based on the address information comparison.  
         [0011]     According to aspects of the invention, there is also provided a computer-readable storage medium having embodied thereon a computer program to execute by a processor a method of routing a frame received over a wired network to a wireless network including mobile nodes (MNs) having a frame routing function, by a routing device to interconnect both the wired and wireless networks, the method of routing the frame embodied in the program including: detecting destination address information included in the frame; comparing the detected destination address information with address information of MNs belonging to a group which the routing device manages; and selectively transferring the frame to the MNs belonging to the group based on the address information comparison.  
         [0012]     Further, according to aspects of the invention, there is provided an apparatus to route a frame between a wireless network including mobile nodes (MNs) having a frame routing function and a wired network, the apparatus including: a comparator to compare address information of MNs belonging to a group which the apparatus manages with destination address information included in the frame received over the wired network; and a transmitter to selectively transfer the received frame to the MNs belonging to the group based on the address information comparison.  
         [0013]     Also, according to aspects of the invention, there is provided a method of routing a broadcast frame in a wireless network, the method including: receiving at least one group identifier (GID), to determine a transfer range of a broadcast frame from an apparatus to relay the broadcast frame between the wireless network and a wired network, and selecting a GID of the received one or more group identifiers (GIDs); receiving the broadcast frame; detecting a GID included in the received broadcast frame and comparing the detected GID with the selected GID; and selectively transferring the broadcast frame based on the GID comparison.  
         [0014]     According to aspects of the invention, there is also provided a computer-readable storage medium having embodied thereon a computer program to execute by a processor a method of routing a broadcast frame in a wireless network, the method of routing the broadcast frame embodied in the program including: receiving at least one group identifier (GID) to determine a transfer range of a broadcast frame from an apparatus to relay the broadcast frame between the wireless network and a wired network and selecting a GID of the received one or more GIDs; receiving the broadcast frame; detecting a GID included in the received broadcast frame and comparing the detected GID with the selected GID; and selectively transferring the broadcast frame based on the GID comparison.  
         [0015]     Further, according to aspects of the invention, there is provided a method of routing a broadcast frame in a wireless network including mobile nodes (MNs) having a frame routing function, the method including: generating a group identifier (GID) to determine a transfer range of a broadcast frame and broadcasting the broadcast frame; receiving the broadcast frame; comparing a GID included in the received broadcast frame with the generated GID; and selectively transferring the broadcast frame based on the GID comparison.  
         [0016]     Additionally, according to aspects of the invention, there is provided a computer-readable storage medium having embodied thereon a computer program to execute by a processor a method of routing a broadcast frame in a wireless network including mobile nodes (MNs) having a frame routing function, the method of routing the broadcast frame in the wireless network embodied in the program including: generating a group identifier (GID) to determine a transfer range of a broadcast frame and broadcasting the broadcast frame; receiving the broadcast frame; comparing a GID included in the received broadcast frame with the generated GID; and selectively transferring the broadcast frame based on the GID comparison.  
         [0017]     Also, according to aspects of the invention, there is provided an apparatus to route a frame in a wireless network, the apparatus including: a receiver to receive at least one group identifier (GID) to determine a transfer range of a broadcast frame from an apparatus to relay the broadcast frame between the wireless network and a wired network; a selector to select a GID of the received one or more group identifiers (GIDs); a comparator to compare a GID included in the broadcast frame to the GID received by the receiver, if the broadcasting frame is received; and a transmitter to transfer the broadcast frame based on the GID comparison.  
         [0018]     Additional aspects and/or advantages of the invention are set forth in the description which follows or are evident from the description, or can be learned by practice of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0020]      FIG. 1  is a block diagram of a LAN environment defined by the IEEE 802.11 standard;  
         [0021]      FIG. 2  is a block diagram of an extended wireless LAN environment;  
         [0022]      FIG. 3  is a block diagram of two groups of mobile nodes (MNs) according to an embodiment of the invention;  
         [0023]      FIG. 4  is a block diagram of a repeater and an MN according to an embodiment of the invention;  
         [0024]      FIG. 5  is a flowchart of a method of forwarding a frame to a wireless network using a repeater according to an embodiment of the invention;  
         [0025]      FIG. 6  is a flowchart of a method of forwarding a broadcast frame using an MN according to an embodiment of the invention; and  
         [0026]      FIGS. 7A and 7B  are block diagrams illustrating changes in groups of MNs according to aspects of the invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0027]     Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain aspects of the invention by referring to the figures, with well-known functions or constructions not necessarily being described in detail.  
         [0028]      FIG. 2  illustrates an extended wireless LAN environment. Referring to  FIG. 2 , a wired network  203  is connected to the Internet  201  via a router  200 . A first repeater  210 , a second repeater  220  and a host  202  are connected to the wired network  203 . The wired network  203  can generally use an Ethernet as a backbone network in a wireless LAN environment. The wired network  203  specifies a network including repeaters, and can be realized as a wireless network.  
         [0029]     The first repeater  210  and the second repeater  220  repeat frames between the wired network  203  and the wireless network  204 , and interface two different environments since the wired network  203  does not follow the IEEE 802.11 protocol in the wireless LAN environment. The first repeater  210  and the second repeater  220  are referred to as portals in the IEEE 802.11 protocol, and are generalized terms for the portals. A first mobile node (MN)  230  (MN 1 ), a second MN  240  (MN 2 ), a third MN  250  (MN 3 ), a fourth MN  260  (MN 4 ), and a fifth MN  270  (MN 5 ) are introduced from the extended wireless LAN environment, and route the frames based on a MAC address, which is a data link layer address of an open systems interconnection (OSI) reference model, and can communicate with each other over the wireless network  204 . The first MN  230  (MN 1 ), the second MN  240  (MN 2 ), the fourth MN  260  (MN 4 ), and the fifth MN  270  (MN 5 ) typically do not include a basic service set (BSS), and thus they are not referred to as wireless access points (APs). However, the third MN  250  (MN 3 ) is an AP including a BSS  290  to which a station  280  belongs.  
         [0030]     The frames transmitted from the router  200  or the host  202  and received by the first and second repeaters  210  and  220  are forwarded based on the MAC address. If a frame that is transmitted from the Internet  201  to the station  280  reaches the wired network  203 , the first repeater  210  and the second repeater  220  can forward the frame to the first MN  230  (MN 1 ), the second MN  240  (MN 2 ), the third MN  250  (MN 3 ), the fourth MN  260  (MN 4 ), and the fifth MN  270  (MN 5 ). The first MN  230  (MN 1 ), the second MN  240  (MN 2 ), the third MN  250  (MN 3 ), the fourth MN  260  (MN 4 ), and the fifth MN  270  (MN 5 ) can form a wireless ad hoc network so that a transfer range is determined according to a topology structure, other than radio wave reach distances of the first repeater  210  and the second repeater  220 , to generate various transfer routes. Since a frame of a link layer does not include a field to determine whether the frame is repeatedly transmitted, if the station  280  broadcasts the frame, a loop can be generated as indicated by the arrows in  FIG. 2 .  
         [0031]      FIG. 3  illustrates two groups A and B of MNs according to an embodiment of the invention. Referring to  FIG. 3 , a first MN  330  (MN 1 ), a second MN  340  (MN 2 ), and a third MN  350  (MN 3 ) belong to the group A managed by a first repeater  310 , and a fourth MN  360  (MN 4 ) and a fifth MN  370  (MN 5 ) belong to the group B managed by a second repeater  320  in a wireless network  381 . The first and second repeaters  310  and  320  store MAC addresses of mobile stations belonging to each of the groups A and B. Therefore, where a frame to be transmitted from the Internet  302  to a station  351  reaches a wired network  380 , since a MAC address of a receipt address field of the frame is identical to, or corresponds to, a MAC address of a mobile station belonging to the group A, the first repeater  310  forwards the frame to the station  351 . However, the second repeater  320  determines that a final receiver of the frame does not belong to the group B, and thus, does not forward the frame and disregards the frame.  
         [0032]     Also, where a proxy address resolution protocol (ARP) is used, the first repeater  310  and the second repeater  320  do not store MAC addresses of all mobile stations, but store the MAC addresses of the MNs respectively belonging to the groups A and B. Where the first repeater  310  broadcasts an ARP frame, the third MN  350  (MN 3 ) responds to the ARP frame instead of the station  351 , and the first repeater  310  forwards the ARP frame to the third MN  350  (MN 3 ). In this regard, each of the first MN  330  (MN 1 ), the second MN  340  (MN 2 ), the third MN  350  (MN 3 ), the fourth MN  360  (MN 4 ), and the fifth MN  370  (MN 5 ) store MAC addresses of mobile stations respectively belonging to a BSS of the MN.  
         [0033]     Where a mobile station belonging to a mobile node broadcasts a frame, and if each of the MNs stores a group ID that discriminates groups of the MNs, a broadcast storm typically does not occur. More specifically, if the station  351  belonging to the group A broadcasts the frame, the fourth MN  360  (MN 4 ) belonging to the group B does not forward the frame transmitted by the third MN  350  (MN 3 ) and disregards the frame, so that a repetitive transfer loop is typically not generated. In that the frame must include the group identifier (ID), a station or an MN must write the group ID to the frame. Further, since a sixth MN  390  (MN 6 ) can be linked with the first repeater  310  and the second repeater  320 , the first repeater  310  and the second repeater  320  must store the group ID. In this regard, the second repeater  320  forwards a broadcasted frame over the wired network  380  and disregards a broadcast frame received from the sixth MN  390  (MN 6 ).  
         [0034]      FIG. 4  is a block diagram of a repeater  400  and an MN  450  according to an embodiment of the present invention. Referring to  FIG. 4 , the repeater  400  includes a wired network interface  410 , a wireless network interface  415 , an advertisement frame generator  420 , a group information storage unit  425 , a group ID generator  430 , and a processor  440 . The MN  450  comprises a wireless interface  455 , a group ID storage unit  460 , and a processor  470 . The wired network interface  410  is a protocol analysis member to communicate with a wired network. The wireless network interfaces  415  and  455  are protocol analysis members to communicate with a wireless network.  
         [0035]     The advertisement frame generator  420  generates an advertisement frame including a MAC address of the repeater  400  and broadcasts the advertisement frame. If the MN  450  receives the advertisement frame, and the MN  450  determines to join a group including the repeater  400 , and the MN  450  sends a response frame including a MAC address of the MN  450 , the group information storage unit  425  stores the MAC address of the MN  450 . Where the MN  450  receives the advertisement frame but does not send a response frame, the group information storing unit  425  can obtain the MAC address of the MN  450  that has joined the group. In this regard, the repeater  400  can obtain MAC addresses of MNs or mobile stations that join the group of the repeater  400  based on an orientation address information field of a data frame transmitted from the MNs or mobile stations. Also, in this regard, where an MN changes groups, the repeaters typically are informed of such a change of groups, such as further discussed with reference to  FIG. 7 .  
         [0036]     The group information storage unit  425  stores address information related to the MNs that have joined the group. The address information includes MAC addresses of stations. Also, if a proxy ARP is used, the address information includes MAC addresses of MNs, as described. The group ID generator  430  generates the group ID used to discriminate groups, stores the group ID in a database associated with the repeater  400 , such as a suitable memory, and transmits the group ID of a group member, via the wireless network interface  415 . However, the group ID can be included in the advertisement frame generated by the advertisement frame generator  420 . Also, the group information storage unit  425 , such as a suitable memory, can store the group ID.  
         [0037]     The processor  440  includes a transmitter  443 , a comparator  444 , and a determiner  445 . The processor  440  can be any suitable processing device, such as a processor, microprocessor or an application specific integrated circuit (ASIC), with associated memory and software or programming, to control the operations of the repeater  400 . If the processor  440  receives a frame from the wired network via the wired network interface  410 , the comparator  444  compares destination address information of the frame to the MAC address stored in the group information storage unit  425 . Where the MAC address and the destination address information are identical to, or corresponds to, each other, the transmitter  443  forwards the frame to a mobile station. Where the MAC address and the destination address information are not identical to, or do not correspond to, each other, the frame is disregarded.  
         [0038]     If a broadcast frame is received, the comparator  444  compares a group ID included in the broadcast frame with the group ID generated by the group ID generator  430 . If the group IDs are identical, or correspond, to each other, the transmitter  443  forwards the broadcast frame. If the group IDs are not identical, or do not correspond, to each other, the broadcast frame is disregarded. However, broadcast frames transmitted over the wired network typically are forwarded without comparing both group IDs. In this regard, the determiner  445  determines whether the processor  440  receives the broadcast frame over the wired network or the wireless network.  
         [0039]     The processor  470  of the MN  450  includes a receiver  471 , a comparator  472 , a selector  476 , a transmitter  473 , a fabricator  474 , and a determiner  475 . The processor  470  can be any suitable processing device, such as a processor, microprocessor or an application specific integrated circuit (ASIC), with associated memory and software or programming, to control the operations of the MN  450 . The determiner  475  receives the advertisement frame from the repeater  400 , determines whether to join the group including the repeater  400 , and informs the transmitter  473  of its determination. The transmitter  473  transmits a response frame to the MAC address of the repeater  400  included in the advertisement frame.  
         [0040]     The receiver  471  receives a group ID from the repeater  400  via the wireless network interface  455 . The group ID storage unit  460  stores the group ID. If the receiver  471  receives two or more group IDs, the selector  476  selects one of the group IDs so that no MN typically should belong to two or more groups simultaneously. If the receiver  471  receives the broadcast fame via the wireless network interface  455 , the comparator  472  compares a group ID included in the broadcast frame with the group ID of the group of the MN  450  stored in the group ID storage unit  460 . If the group IDs are identical to, or correspond to, each other, the transmitter  473  forwards the broadcast frame. If the group IDs are not identical, or do not correspond, to each other, the broadcast frame is disregarded. Also, if the receiver  471  receives a broadcast frame that does not include a group ID, and the fabricator  474  determines that the broadcast frame is transmitted from a mobile station within the BSS managed by the MN  450 , the fabricator  474  writes the group ID of the group of the MN  450  to the broadcast frame, and forwards the broadcast frame.  
         [0041]      FIG. 5  is a flowchart of a method of forwarding a frame to a wireless network using a repeater according to an embodiment of the invention. Referring to  FIG. 5 , the repeater broadcasts an advertisement frame including a MAC address of the repeater to the MNs (Operation  510 ), receives the advertisement frame, stores a MAC address detected from the response frame or a data frame received from an MN that attempts to join a group, and registers the MN as a group member (Operation  520 ). The repeater receives a frame from a wireless network, which is a backbone network (Operation  530 ), extracts destination address information of the frame (Operation  540 ), and compares the extracted destination address information to a MAC address of the MN to determine whether the analyzed MAC address belongs to a group member (Operation  550 ). If the extracted destination address information and the MAC address of the MN are identical, or correspond, to each other, where the analyzed MAC address belongs to a group member, the repeater forwards the frame to the MN (Operation  560 ), otherwise the frame is disregarded (Operation  555 ).  
         [0042]      FIG. 6  is a flowchart of a method of forwarding a broadcast frame using an MN according to an embodiment of the invention. Referring to  FIG. 6 , the MN receives an advertisement frame including a MAC address of a repeater from the repeater (Operation  610 ), determines to join a group including the repeater, and transmits a response frame. The repeater stores a MAC address of the MN included in the response frame so that the MN is registered as a member of the group. The MN receives a group ID from the repeater (Operation  620 ). The group ID can be included in the advertisement frame. Where the MN does not transmit the response frame, the MN can be registered as a member of the group by transferring a data frame to the repeater. If the MN receives a plurality of group IDs from two or more repeaters, the MN selects one of the group IDs and is registered as a member of the selected group.  
         [0043]     The MN receives the broadcast frame (Operation  630 ), extracts a group ID included in the broadcast frame and analyzes the extracted group ID (Operation  640 ), and determines whether a group ID exists (Operation  650 ). If no group ID exists, and the MN determines that a mobile station within a BSS managed by the MN has broadcasted the frame, the MN writes a group ID of the group of the MN to the broadcast frame (Operation  680 ), and forwards the broadcast frame (Operation  690 ). If a group ID exists, the MN compares the group ID of the group of the MN with the extracted group ID (Operation  660 ). If the group IDs are identical, or correspond, to each other, the MN forwards the broadcast frame (Operation  690 ). If the group IDs are not identical to, or do not correspond to, each other, the MN disregards the broadcast frame (Operation  670 ).  
         [0044]      FIGS. 7A and 7B  are block diagrams illustrating changes in groups of MNs according to an embodiment of the invention. Referring to  FIG. 7A , where the location of a third MN  730  (MN 3 ) is changed as shown in  FIG. 7A , groups of the third MN  730  (MN 3 ) are typically changed since the third MN  730  (MN 3 ) that joins a group A communicates with only a fifth MN  760  (MN 5 ). In this regard, if the group A of the third MN  730  is not changed to a group B, a frame broadcasted in the group A is no longer transmitted to the third MN  730  (MN 3 ).  
         [0045]     In this regard, if a fourth MN  750  (MN 4 ) of the group B analyzes a group ID of the broadcast frame transmitted from a second MN  720  (MN 2 ) and determines that the broadcast frame is not transmitted from the group B, the broadcast frame is not forwarded. The broadcast frame is forwarded via a second repeater  740  over a wired network. Finally, since the broadcast frame forwarded by the fifth MN  760  (MN 5 ) includes a group ID of the group B, the third MN  730  (MN 3 ) disregards the broadcast frame.  
         [0046]     Therefore, the third MN  730  (MN 3 ) transmits a broadcast frame to the second repeater  740  in order to join the group B. In this regard, a first repeater  700  deletes the third MN  730  (MN 3 ) from a routing table, which is a MAC address information list of group members of the first repeater  700 , and the second repeater  740  or the third MN  730  (MN 3 ) informs the first repeater  700  of the group change.  
         [0047]     Referring to  FIG. 7B , although the location of MNs is not changed, the group of the third MN  730  is changed. If a third MN  730  (MN 3 ) that joins the group A including the first repeater  700  transmits a frame to the second repeater  740 , the second repeater  740  stores a MAC address of the frame, and the third MN  730  (MN 3 ) joins the group B so that the group of the third MN  730  (MN 3 ) is changed. As described with reference to  FIG. 7A , the third MN  730  (MN 3 ) or the second repeater  740  informs the first repeater  700  of the group change of the third MN  730  (MN 3 ).  
         [0048]     According to the aspects of the invention, a repeater groups MNs and manages the grouped MNs in an extended wireless LAN environment. Therefore, where an MN communicates with two or more repeaters directly or indirectly, a route is typically set such that a frame is received via a repeater, to promote reducing unnecessary network resources and preventing a broadcast storm where a broadcast frame is repeatedly transmitted along a loop.  
         [0049]     The foregoing embodiments, aspects and advantages are merely exemplary and are not to be construed as limiting the invention. Also, the description of the embodiments of the invention is intended to be illustrative, and not to limit the scope of the claims, and various other alternatives, modifications, and variations will be apparent to those skilled in the art. Therefore, although a few embodiments of the invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in the embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.