Abstract:
Overlaying a Wireless Macro Cell architecture on a Micro Cell network. WLAN MAC Address Translation (WMAT) is used to translate BSSIDs from the BSSID used to initialize a radio in an access node and identify communications between the radio in the access node and a controller, and the BSSID used over the air for Macro Cell operation. WMAT is used for transmit operations, translating the BSSID of outgoing packets to the Macro Cell BSSID prior to wireless transmission. On the receive side, packets undergo WMAT and transmission to the controller if the STN MAC address of the sender is in an ACK table associated with the radio, or the packet is one of a predetermined type. The ACK table is managed by transmit operations, and by control commands from the controller.

Description:
[0001]    The present application is a continuation of pending U.S. patent application Ser. No. 12/261,959, entitled “Wireless Macro Cell Overlay” filed on Oct. 30, 2008. The present invention relates to wireless systems, and in particular, to the problem of overlaying a Macro Cell architecture on top of a Micro Cell network. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Wireless networks, such as those operating according to IEEE 802.11 standards typically provide wireless packet-based data services to clients in a network. In one embodiment of a wireless network such as that shown in  FIG. 1 , referred to as a Micro Cell architecture, each access node  300  has a distinct Basic Service Set Identifier (BSSID) which usually represents the Media Access Control (MAC) address of the radio in the access node. Access nodes advertise access to one or more networks which are identified by Service Set Identifiers (SSID). Multiple access nodes may advertise the same SSID-identified network on the same or different radio channels, but the BSSIDs are distinct. Access nodes  300  are coordinated by controller  200 , which also provides access to network  100 . 
         [0003]    In a Macro Cell network as shown in  FIG. 2 , multiple access nodes  300  advertise services using the same BSSID and SSID values, operating on the same channel. 
         [0004]    What is needed is a way to overlay a macro cell architecture on a micro cell network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The invention may be best understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention in which: 
           [0006]      FIG. 1  shows a Micro Cell network, 
           [0007]      FIG. 2  shows a Macro Cell network, and 
           [0008]      FIG. 3  shows details of a network. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Embodiments of the invention relate to methods of overlaying a Macro Cell wireless architecture on a Micro Cell wireless network by providing WLAN Mac Address Translation (WMAT) in the access nodes, allowing an access node to advertise a Macro Cell BSSID over the air, and support connections on that BSSID. In a Micro Cell network comprising one or more access nodes connected to a controller, an access node during initialization establishes one or more connections with its controller. As part of that initialization, the access node establishes connections for each radio in the access node, each connection established using the BSSID associated with a radio in the access node. 
         [0010]    According to the present invention, as this connection is established with the controller, a Macro Cell Manager running on the controller recognizes BSSIDs associated with Macro Cell nodes. The Macro Cell manager sends control messages to the indicated BSSID, changing the radio associated with that BSSID to Macro Cell mode, and giving it a new BSSID to use for wireless communications. Other information such as channel selection and power levels may also be supplied. 
         [0011]    During operation in Macro Cell mode, the radio applies wireless mac address translation (WMAT) to transmit traffic sent to its BSSID by the controller, translating the BSSID used on the controller link to the BSSID supplied for over the air Macro Cell operation. On the receive side, an ACK table is associated with the radio in Macro Cell operation, containing the STN MAC addresses of client devices to which it responds. When a frame from a client with an STN MAC address contained in the ACK table is received, an ACK is transmitted to that client, and the frame is forwarded to the controller. Entries are added to the ACK table based on message traffic transmitted, or by control messages from the controller. Certain incoming messages, which may include broadcasts and/or probe request frames, are forwarded to the controller, again using WMAT, translating the over-the-air Macro Cell BSSID to the BSSID used for the controller connection. 
         [0012]    As shown in  FIG. 1 , a Micro Cell architecture network supports connections of wireless clients  400   a ,  400   b  to a wired network. Wired network  100 , such as a wired IEEE 802.3 Ethernet network, is connected to controller  200 . Controller  200  supports connections  250  to access nodes  300   a ,  300   b ,  300   c . Access nodes  300   a ,  300   b ,  300   c  provide wireless communications to wireless clients  400   a ,  400   b.    
         [0013]    As is understood in the art, controller  200  is a purpose-built digital device having a CPU  210 , memory hierarchy  220 , and a plurality of network interfaces  230 ,  240 . CPU  210  may be a MIPS-class processor from companies such as Raza Microelectronics or Cavium Networks, although CPUs from companies such as Intel, AMD, IBM, Freescale, or the like may also be used. Memory hierarchy  220  includes read-only memory for device startup and initialization, high-speed read-write memory such as DRAM for containing programs and data during operation, and bulk memory such as hard disk or compact flash for permanent file storage of programs and data. Network interfaces  230 ,  240  are typically IEEE 802.3 Ethernet interfaces to copper, although high-speed optical fiber interfaces may also be used. Controller  200  typically operates under the control of purpose-built embedded software, typically running under a Linux operating system, or an operating system for embedded devices such as VXWorks. 
         [0014]    Similarly, as understood by the art wireless access nodes  300   a ,  300   b  and  300   c  are also purpose-built digital devices. These access nodes include CPUs  310 , memory hierarchy  320 , and wireless interfaces  330 . Wireless interfaces  330  may contain one or more radio transmitter/receiver pairs. As with controller  200 , the CPU commonly used for such access nodes is a MIPS-class CPU such as one from Raza Microelectronics or Cavium Networks, although processors from other vendors such as Acorn, Intel, AMD, Freescale, and IBM may be used. The memory hierarchy comprises read-only storage for device startup and initialization, fast read-write storage such as DRAM for holding operating programs and data, and permanent bulk file storage such as compact flash. Wireless access nodes  300  typically operate under control of purpose-built programs running on an embedded operating system such as Linux or VXWorks. Wireless interfaces  330  are typically interfaces operating to the family of IEEE 802.11 standards including but not limited to 802.11a, b, g, and/or n. 
         [0015]    Wireless client  400  is also a digital device, similarly having CPU  410 , memory hierarchy  420 , wireless interface  430 , and I/O devices  450 . As examples, wireless device  400  may be a general purpose computer such as a laptop, or may be a purpose-built device such as a Wi-Fi phone or a handheld scanner. In a general-purpose computer, CPU  410  may be a processor from companies such as Intel, AMD, Freescale, or the like. In the case of purpose-built devices, Acorn or MIPS class processors may be preferred. Memory hierarchy  420  comprises the similar set of read-only memory for device startup and initialization, fast read-write memory for device operation and holding programs and data during execution, and permanent bulk file storage using devices such as flash, compact flash, and/or hard disks. Additional I/O devices  450  may be present, such as keyboards, displays, speakers, barcode scanners, and the like. 
         [0016]    In operation of the Micro Cell network according to  FIG. 1 , access nodes  300  start up, and establish a connection  250  with controller  200 . Access nodes  300  may boot from images stored internally in memory hierarchy  320 , by fetching an image from controller  200 , or by a combination. The connection  250  established, for example, between access node  300   a  and controller  200  is established using standard TCP/IP, and is established with an ID, for example, the same value as the BSSID used for wireless transmissions, in this case, 31. As access node  300   a  continues its startup, it advertises wireless services on channel  1  using BSSID=30 and SSID=“ENGR” as an example. Similarly, access nodes  300   b  and  300   c  start up, establishing communications links  250  with controller  200 , and advertising wireless services as shown, each advertising the SSID “ENGR” but with different BSSIDs and on different channels. 
         [0017]    While connection  250  is shown as a direct link between controller  200  and access nodes  300 , this link may be a wired link such as an 802.3 Ethernet link, or a wireless link such as an 802.11 mesh network link, WiMax link, or other wireless backhaul. Wired links may be electrical, optical, or a combination, including passing through switched networks, for example, having an access node  300  at a remote location such as a user&#39;s home, connecting back to corporate controller  200  through public Internet connections. It should be noted that these connections  250  may be encrypted, for example using GRE tunnels. Traffic across this link  250 , from access node  300  to controller  200  is identified, for example using the BSSID of the radio in access node  300 . 
         [0018]    While the internal architecture of controller  200 , access nodes  300 , and wireless client  400   a  in the Macro Cell network of  FIG. 2  may be similar to their counterparts in  FIG. 1 , the operation of the wireless network is different. In the Macro Cell network, as shown in  FIG. 2 , multiple access nodes operate on the same channel, advertising the same BSSID, and therefore SSID, as an example, all operating on channel  1  with SSID=“EP” and BSSID=121. 
         [0019]    According to an aspect of the present invention, one or more access nodes in a Micro Cell network during startup are converted to Macro Cell operation. As shown in  FIG. 3 , as access node  300   g  starts up, it establishes a connection with controller  200 , identifying itself using a preset ID, for example its BSSID (BSSID 1 ). This ID is recognized by the Macro Cell Manager process  280  running in controller  200 . Macro Call Manager  280  instructs access node  300   g  to switch to Macro Cell mode, supplying it with a new BSSID (BSSID 2 ) to use for over-the-air communications. Other information, such as channel number and SSID may also be supplied. In transmit operation, packets sent by controller  200  to access node  300   g  using BSSID 1  are translated using wireless mac address translation (WMAT) and transited over the air using the translated BSSID, BSSID 2 . 
         [0020]    For receive operation, according to the present invention, a subset of frame types received by a Macro Cell access node such as access node  300   g  are forwarded directly to controller  200 . This subset may include messages such as broadcasts and/or probe request frames, or other types as defined by Macro Cell manager  280  and/or controller  200 . Frames sent from Macro Cell access node  300   g  to controller  200  undergo WMAT, substituting BSSID 1  for BSSID 2 . 
         [0021]    Other received frames are processed in Macro Cell access node  300   g  according to an ACK table  350  kept by access node  300   g . Each frame received contains the STN MAC address of the device sending the frame, as well as BSSID 2 , the BSSID of the device to which the frame is addressed. ACK table  350  contains the STN MAC addresses of client devices to which access node  300   g  responds. When access node  300   g  receives a frame with an STN MAC address with a match in its ACK table, it transmits an ACK to that wireless client, and forwards the frame to controller  200 . Entries to ACK table  350  may be added and/or deleted using control messages sent by controller  200  and/or Macro Cell manager  280 . Entries may also be added to ACK table  350  automatically by Macro Cell access node  300   g , by inspecting STN MAC addresses of messages received from controller  200  to be transmitted after WMAC using the over the air BSSID 2 , and adding those STN MAC addresses not already present in ACK table  350 . 
         [0022]    While the invention has been described in terms of various embodiments, the invention should not be limited to only those embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is this to be regarded as illustrative rather than limiting.