Patent Publication Number: US-2003235170-A1

Title: Method, apparatus, and system for distributed access points for wireless local area network (LAN)

Description:
FIELD  
       [0001] An embodiment of the invention relates to the field of data communications, and more specifically, relates to a method, apparatus, and system for distributed access points for wireless local area network (LAN).  
       BACKGROUND  
       [0002] In the past few years, communication systems have continued to advance rapidly in light of several technological advances and improvements with respect to communication networks and protocols, in particular wireless communication networks. Wireless local area networks have become increasingly used to facilitate effective and efficient information communication in various environments and improve user mobility and flexibility. A wireless local area network (LAN) can be implemented to extend the connectivity of a wired local area network or as an alternative of a wired local area network.  
       [0003]FIG. 1 illustrates an embodiment of a typical wireless network system  100 . The wireless network system  100  includes a link  110  based on a physical medium, which is part of a wired network  115  (e.g., a wired local area network such as an Ethernet LAN). The wired network  115  includes network or system resources  120  that can be accessed and used by users of the network system  100 . For example, the system or network resources  120  may include network servers, file servers, system databases, application programs, etc. As shown in FIG. 1, the network system  100  further includes multiple access points (APs)  130 A- 130 C that communicate via a wireless link with their associated mobile units (MUs)  140 A- 140 E. The mobile units are also referred to as mobile stations or simply stations herein. Users of the mobile units  140 A- 140 E can access and use the system resources  120  via the access points  130 A- 130 C. The access points  130 A- 130 C are used as bridges between the wired network  115  and a wireless network comprised of mobile units  140 A- 140 E. In other words, the access points  130 A- 130 C provide connectivity between the wired network  115  and the mobile units  140 A- 140 E and also between the mobile units themselves. Typically, the mobile units  140 A- 140 E communicate with the access points  130 A- 130 C using a standardized protocol (e.g., the Institute of Electrical and Electronic Engineers (IEEE) 802.11 wireless communication standard, published Nov. 16, 1998).  
       [0004] Generally, an access point is used to for various purposes or functions including: (1) providing connection between the mobile units or stations and the wireless network; (2) performing the point control functions for the associated mobile units, as defined by a standardized protocol such as the IEEE 802.11 standard; and (3) providing the connectivity between the wireless network and the wired network (e.g., an Ethernet network). The second function performed by an access point requires computation and memory resources. However, the first function performed by an access point can be considered as the function of a radio repeater. Each access point in a typical wireless network requires to be equipped and configured to perform all of those functions mentioned above. Such a configuration may result in under-utilization of the resources and capacity of some access points and over-utilization of other access points in the wireless network. For example, for a given period of time, it is assumed that the access point  130 A is required to perform the point control functions for all of its associated mobile units while another access point such as  130 B is only performing the connectivity function for its associated mobile units. In this example, it can be seen that access point  130 A is over-utilized and access point  130 B is under-utilized with respect to their computation and memory resources required to perform their corresponding functions. As a result, the conventional configuration of access points in a wireless network can be inefficient with respect to cost, flexibility, and scalability of resources.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0005] The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. In the drawings:  
     [0006]FIG. 1 shows a block diagram of a wireless network system;  
     [0007]FIG. 2 illustrates a block diagram of a wireless network configuration according to one embodiment of the invention;  
     [0008]FIG. 3 shows a block diagram of an access point repeater (APR) according to one embodiment of the invention;  
     [0009]FIG. 4 shows a block diagram of an access point server (APS) according to one embodiment of the invention;  
     [0010]FIG. 5 shows a flow diagram of a process according to one embodiment of the invention; and  
     [0011]FIG. 6 illustrates a flow diagram of a method according to one embodiment of the invention.  
    
    
     DETAILED DESCRIPTION  
     [0012] In the following detailed description numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details.  
     [0013] As mentioned above, an access point in a wireless network system is used to for various purposes or functions including: (1) providing connection between the mobile units or stations and the wireless network; (2) performing the point control functions for the associated mobile units, as defined by a standardized protocol such as the IEEE 802.11 standard; and (3) providing the connectivity between the wireless network and the wired network (e.g., an Ethernet network). The second function performed by an access point requires computation and memory resources. However, the first function performed by an access point can be considered as the function of a radio repeater.  
     [0014] In one embodiment of the invention, a distributed access point configuration is implemented for a wireless local area network system. Instead of having each access point configured and equipped to perform both the media access functions and the specific point control functions according to a wireless communication protocol or standard such as the IEEE 802.11 standard, an access point according to one embodiment of the invention is comprised of two parts or two components. One component is called an access point repeater (APR) and the other component is called an access point server (APS). In one embodiment, one APS can support multiple access point repeaters (APRs).  
     [0015] In one embodiment of the invention, the functions that are performed by a conventional or traditional access point in a wireless network system are split between the APR and the APS. In one embodiment, the APR can be used to perform the media access functions of a standardized access control protocol such as the medium access control (MAC) protocol as specified in the IEEE 802.11 standard. The APS, in one embodiment, can be used to perform the specific point control functions that are relatively not real-time functions. In one embodiment, the APR and the APS are connected via a wired network (e.g., an Ethernet wired LAN) to communicate with each other.  
     [0016]FIG. 2 illustrates a block diagram of a wireless network configuration  200  according to one embodiment of the invention. As shown in FIG. 2, the wireless network configuration  200  includes an access point server (APS)  210 , one or more access point repeaters (APRs)  220 ( 1 )-  220 (N). The APS  210  and the APRs  220  are connected and communicate with each other via a link  230 , which is part of a wired network  240 . In one embodiment, the wired network  240  is an Ethernet wired local area network (LAN) and the link  230  can be an Ethernet hub or switch. The network configuration  200  further includes system resources  250  (e.g., server/router) that are coupled to network link  230 .  
     [0017] In one embodiment, each APR  220  can be associated with one or more mobile units (not shown). Mobile units are also referred to as mobile stations or simply stations herein. A “mobile unit” (MU) can be any electronic device that includes logic for processing information (e.g., a processor, microcontroller, state machine, etc.) and a wireless transceiver for receiving information from and transmitting information to another electronic device (e.g., an APR or another mobile unit, etc.). Mobile units may include computers (e.g., desktop computers, laptop computers, hand-held computers such as a personal digital assistant “PDA”, etc.), communications equipments (e.g., pagers, telephones, facsimile machines, etc.), television set-top boxes, PC cards, PCI adapters, bar-code scanners, etc. In one embodiment, an APS such as the APS  210  can be configured to support multiple APRs such as APR  220 ( 1 )- 220 (N).  
     [0018] In one embodiment, the APR  220  is used to perform the media access portion of the MAC protocol that needs real-time performance and wireless physical layer (PHY) functionality. As shown in FIG. 2, each APR  220  is connected with the APS  210  through the Ethernet link  230 . In one embodiment, the APS  210  is a software application that can run on any Ethernet-aware platform (e.g., server, router, switch, etc.). The APS  210  performs the specific point control functions of a wireless communication protocol such as the IEEE 802.11 standard. The specific point control functions are relatively not real-time functions. For example, in one embodiment, the APS  210  is responsible for getting and storing frames that cannot be immediately delivered or released due to the power state of the receiving stations. In one embodiment, the APS  210  can also perform the wired equivalent privacy (WEP) and other non-MAC layer security/authentication algorithms or functions such as security key distribution. In one embodiment, the APR  220  includes 802.11 physical layer (PHY), all or part of the 802.11 MAC component, Ethernet MAC and PHY, MAC address filter, one or more buffers (e.g., FIFO buffers) and corresponding buffer control logic. In one embodiment, one FIFO buffer is used for wireless to wired network (e.g., wireless to Ethernet) information transfer. One or more FIFO buffers are used for wired network to wireless (e.g., Ethernet to wireless) information transfer to allow for flexibility in case of priority and PCF (point coordination function) support. For example, one FIFO buffer can be used to collect frames sent by DCF (distributed coordination function) and another FIFO buffer can be used to collect frames sent by PCF. In one embodiment, multiple FIFO buffers may be used to support priority queues and fragmentation also.  
     [0019] According to one embodiment of the invention, MAC multi-addressing mechanism is utilized as follows. Each APR  220  is a multi-addressable entity or device on the wired network (e.g., Ethernet LAN). Each APR  220  is associated in the APS  210  with every MAC address of stations supported by the respective APR  220 . The APS  210  is also a multi-addressable entity or device on the wired network (e.g., Ethernet LAN). The APS  210  obtains from the Ethernet the basic service set identifier (BSSID) addresses of the APRs that are connected to the APS  210 . In this configuration, no look up is needed to process frames transferred between stations, APR, and APS.  
     [0020]FIG. 3 shows a block diagram of an access point repeater (APR)  220  according to one embodiment of the invention. As shown in FIG. 3, in one embodiment, APR  220  may include IEEE 802.11 physical layer (PHY)  310 , IEEE 802.11 MAC Real Time portion  320 , one or more prioritized transmit buffers  330 , one or more non-prioritized transmit buffers  335 , one or more receive buffers  340 , buffers control logic  350 . The APR  220  further includes adaptive multi-addressing filter  360  and Ethernet MAC/PHY layer  370  These various components are used by the APR  220  to perform its corresponding media access functions of the MAC protocol that need real-time performance and wireless PHY functionality.  
     [0021] In one embodiment, APR  220  is a multi-addressable entity on the wired network (e.g., the Ethernet LAN). The APR  220  is addressable by MAC address of any station associated with APR  220 . The APR  220  includes a table of addresses which is updated each time a station is associated with or disassociated from the APR  220 . In one embodiment, the APR  220  receives all frames directed to it via the wireless medium (e.g., air) according to a wireless communication standard such as the IEEE 802.11 standard. Control frames received by the APR  220  are processed by the APR  220 . Management frames are directed by the APR  220  to the APS  210 . Data frames can be redirected by the APR  220  to the appropriate station provided that certain criteria are satisfied. For example, the APR  220  can redirect data frames to a station when the respective station is in the same basic service set (BSS), in the proper power state to receive data, and that the APR  220  is able to properly perform the required security functions, if necessary, with respect to the data frames to be sent (e.g., decrypt and/or encrypt).  
     [0022] In one embodiment, the APR  220  will redirect a data frame to the APS  210  if the data frame should be stored or needs decryption/encryption processing that the APR  220  is not able to provide. The APR  220  redirects the received data frame to the APS  210  by enveloping the data frame in an Ethernet frame and using the corresponding BSSID as the destination address.  
     [0023] In one embodiment, the APR  220  gets Ethernet frames from APS  210  to be sent to a corresponding station via the wireless medium (e.g., air). These frames contain valid 802.11 frames under Ethernet envelope. Destination address of these frames is the address of the corresponding station. There can be various kinds of frames sent from the APS  210  to the APR  220 . They may include frames for immediate transmission and frames that should be sent in a particular manner (e.g., PCF). In this case, the APR  220  can recognize and store such frames for later use.  
     [0024]FIG. 4 shows a block diagram of an access point server (APS) (e.g., APS  210 ) according to one embodiment of the invention. As shown in FIG. 4, APS  210  may include an Ethernet MAC/PHY layer  410 , an adaptive multi-addressing filter  415 , a network driver  420 , IEEE 802.11 MAC management portion  425 , and one or more extended access point (AP) applications  430 . The APS  210  may further include a database  435  for storing information and an operating system  440  for controlling the operations of the various components included in the APS  210 .  
     [0025] In one embodiment, the APS  210  is configured as a multi-addressable entity on the wired network (e.g., Ethernet LAN). The APS  210  can be addressable by the corresponding BSSID of any APR supported by APS  210 . In one embodiment, the APS  210  receives redirected frames from the APR  220  which are enveloped in Ethernet format. The BSSID of the respective APR  220  is used as the destination address. In one embodiment, APS  210  gets all management frames redirected to APS  210  by APR  220 . The APS  210  may also get some control frames and data frames. The APS  210  is responsible for performing management functions of the wireless communication protocol (e.g., IEEE 802.11).  
     [0026] In one embodiment, the APS  210  is configured to store data frames that cannot be immediately sent to stations because the stations are in power down state. The APS  210  also forwards data frames between basic service sets. In one embodiment, the APS  210  creates, stores, and distributes security keys between stations. The APS  210  allows usage of individual key for any station.  
     [0027] In one embodiment, the APS  210  sends IEEE 802.11 frames to the APR  220  for transmission over the wireless medium to the stations. The APS  210  envelops these frames in Ethernet format. The destination address of these frames is the address of the station. The APS  210  could allow roaming between APRs by substitution of the BSSID in the registry of stations.  
     [0028]FIG. 5 shows a flow diagram of a process  500  according to one embodiment of the invention. As shown in FIG. 5, the process  500  includes the association phase or sub-process  510 , the transmit data phase or sub-process  530 , and the receive data or sub-process  550 . At block  512 , a station issues an association request with a BSSID. At block  514 , an APR with the corresponding BSSID receives the respective association request and forwards the association request to an APS. In one embodiment, the APR appends the address of this station to its adaptive multi-addressing filter. At block  516 , the APS processes the association request and answers with an association response. The association response is then sent from the APS to the APR through a wired network (e.g., the Ethernet LAN). The association response frame is enveloped in an Ethernet format using the station address as the destination address. If the response is unsuccessful, the last added MAC address is removed from the APR&#39;s adaptive multi-addressing filter. At block  518 , the APR sends the association response to the station via the wireless medium (e.g., air).  
     [0029] Referring again to FIG. 5, at block  532 , to transmit a data frame from the APS to an APR, the APS envelopes the frame to be transmitted in Ethernet format using the station address as the destination address and sends the data frame to the APR via the wired network (e.g., the Ethernet LAN). The APR that receives the data frame is responsible for delivering this data frame to the corresponding station so that the APS can free the buffer of this data frame (at block  534 ). At block  536 , the APR transmits the data frame to the respective station and waits for an acknowledgement signal (ACK) from the respective station. At block  538 , the APR responds to the APS with the ACK signal so that the APS can determine whether the APR frees its buffer for the next frame.  
     [0030] Continuing with the present discussion, at block  552 , a station (also called a first station) transmits data to another station (called a second station). The APR recognizes the BSSID of the frame and receives the frame from the first station. At block  554 , the APR checks the CRC of the frame received to decide whether to respond with ACK. At decision block  556 , if the CRC fails (CRC not OK), the frame is dismissed and ACK is not sent by the APR (at block  572 ). If the CRC is successful (CRC OK), there can be different scenarios to process the frame. For example, in one embodiment, in one scenario, the APR can be configured to send any data frame received from a station to the APS (scenario 1, block  558 ). In this case, the APR forwards the data frame to the APS which is enveloped with an Ethernet header and using the BSSID as the destination address. The APS then decides how to process the data frame (e.g., how to decrypt the data frame, to store it or to forward for transmission to the targeted station).  
     [0031] Alternatively, in another embodiment (scenario 2), the APR may be configured to decide whether to redirect the received data frame to the targeted station or to send the data frame to the APS, based on various factors or criteria (at block  560 ). For example, the various factors or criteria used by the APR to determine whether to redirect the data frame to the targeted station or send the data frame to the APS may be based the APR&#39;s capabilities to perform certain required functions to process and transmit the data frame, the power state of the targeted station, whether the targeted station is in the same BSS as the transmitting station, etc. For example, if each station uses its own key for encryption and the APR does not have enough space to store keys for all stations then the APR needs to forward the data frame to the APS. As another example, if the targeted station is in power down mode then the APR needs to send the data frame to the APS to be stored for transmission to the targeted station later on.  
     [0032]FIG. 6 illustrates a flow diagram of a method  600  according to one embodiment of the invention. At block  610 , a first communication device in a wireless local area network is connected to a wired local area network. At block  620 , a second communication device in the wireless local area network is connected to the wired local area network. The first and second communication devices communicate with each other via the wired local area network. At block  630 , the first communication device is assigned and configured to function as an access point repeater (APR) to transmit information to and receive information from one or more mobile units (stations) that are associated with the first communication device, according to a first wireless processing protocol (e.g., IEEE 802.11 standard). The first communication device is configured to perform the media access functions of the first wireless processing protocol (e.g., the media access portion of IEEE 802.11 MAC protocol). At block  640 , the second communication device is assigned and configured to function as an access point server (APS). The second communication device is configured to perform specific point control functions of the first wireless processing protocol that are relatively not real-time functions.  
     [0033] While the invention has been described in terms of several embodiments, those of ordinary skill in the art will recognize that the invention is not limited to the embodiments described herein. It is evident that numerous alternatives, modifications, variations and uses will be apparent to those of ordinary skill in the art in light of the foregoing description.