Abstract:
In a wireless local area network including an access controller (AC) and an access points (AP), the AC transmits a functionality inquiry to the AP. Upon receiving the inquiry, the AP transmits a query response including the functional capabilities of the AP. The AC then generates a map of the functional capabilities present in the network based on the inquiry response. Conflicting or redundant functional capabilities are identified and are disabled, enabled, or reconfigured by instructions from the AC. The AC may selectively enable and/or disable functional capabilities at nodes in the network to provide a more balanced load on the network, and to provide for load sharing by allocating functionalities between and among network nodes having common functional capabilities to satisfy a variety of situations encountered in the network.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 60/670,174, filed on Apr. 11, 2005, which is incorporated by reference as if fully set forth herein. 
    
    
     FIELD OF INVENTION 
     The present invention generally relates to wireless local area networks (WLANs), and more particularly, to a method and apparatus for determining and analyzing network topology, configuring network nodes, and resolving functional conflicts that arise in network architectures. 
     BACKGROUND 
     The term “access point” (AP) as used herein includes, but is not limited to, a base station, an access router (AR), a Node B, a site controller, or other interfacing device in a wireless environment that provides other stations with wireless access to a network with which the AP is associated. 
     The term “station” (STA) as used herein includes, but is not limited to, a wireless transmit/receive unit (WTRU), a user equipment, a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. 
     Typically, a WLAN includes a plurality of APs, wherein each AP is capable of conducting concurrent wireless communications with appropriately configured STAs, as well as multiple appropriately configured APs or ARs, when configured in the “infrastructure mode”. Some STAs may alternatively be configured to conduct wireless communications directly to one another, i.e., without being relayed through a network via an AP. This is commonly known as “peer-to-peer mode” or “ad hoc mode”. Where a STA is configured to communicate directly with other STAs, it may also be configured to function as an AP. STAs can be configured for use in multiple networks, with both network and peer-to-peer communications capabilities. 
     In the infrastructure mode architecture, STAs are conventionally connected in a star-type topology to a central AP in order to communicate to each other or to connect to other external networks. Although this architecture has proven successful in the past, many factors, such as the increasing number of closely located APs, the increasing number of applications for a WLAN, and the fact that APs are restricted to public bands, have resulted in conventional infrastructure mode architectures becoming less desirable. Accordingly, other infrastructure mode topologies have evolved. 
     One topology is known as a “mesh” topology, in which WLAN nodes have two or more paths between them which enables the nodes to communicate directly with each other (i.e., as in the ad hoc mode) and to communicate indirectly with each other (via other nodes that relay information). A second topology is known as a “split” architecture, in which one or more access routers (ARs) or access controllers (ACs) are connected via an interconnection to APs present in the network. The ACs provide network-wide monitoring, improve scalability, and facilitate dynamic configurability. The logical interconnection may be a direct connection to the APs, a switched connection, or a routed network connection. The AC and the AP may be collocated in the same physical device. 
     In addition to exchanging configuration and control information with the APs, the ACs “split” or share certain functionalities with the APs that are conventionally provided solely by the APs. That is, functions typically provided by standalone or “fat” APs are removed from these APs and are provided by the AC(s). These split-function or reduced-function APs are referred to as “thin” APs. This architecture is similar to a UMTS architecture, where the AC is analogous to a central radio network controller (RNC) and the AP is analogous to a Node B connected to the RNC. 
       FIG. 1  is a diagram of a network  100  with an infrastructure mode architecture including a plurality of STAs  102   a - 102   n  communicating with a fat AP  104 . This architecture is often referred to as a fat AP architecture because all of the medium access control (MAC) layer functionalities are located in the AP  104 . The STAs  102  communicate with the AP  104 , and with one another via the AP  104 . The AP  104  incorporates a physical (PHY) layer  106 , a real time (RT) MAC layer  108 , and a non-real time (NRT) MAC layer  110 . 
       FIG. 2  is a diagram of a network  200  with a split architecture, including a plurality of STAs  202   a - 202   i , several APs  204   a - 204   c , and an access controller (AC)  206 . In the split network  200 , certain AP functions are split away from the APs  204  and are provided by the AC  206 . Although the AP functions may be split in any number of configurations,  FIG. 2  shows one of the most common arrangements. The APs  204  terminate the infrastructure side of the wireless physical links, provide radio-related management, and provide all RT services to the STAs  202 . The AC  206  provides the NRT management functions such as configuration, quality of service (QoS), access control, etc., for all of the APs  204 . By sharing functionalities at a higher layer, a better coordinated deployment is possible. 
     The AP functional definitions made to support future AC-AP architectures must also be backward compatible to accommodate present-day devices. Since infrastructure mode networks are the present-day convention, it is noted that accommodating hybrid architectures, i.e., those networks with both fat APs and thin APs, will be a significant challenge for future networks. 
     An example of a pathological hybrid network  300  with both fat APs and thin APs is shown in  FIG. 3 . The network  300  includes a plurality of STAs  302   a - 302   i ; two thin APs, AP 1  ( 304   a ) and AP 2  ( 304   b ); a fat AP, AP 3  ( 306 ); and an AC  308 . AP 3   306  provides all of its L 2  MAC functionalities, including both the RT MAC  310  and the NRT MAC  312 . In this deployment, the AC  308  manages all three APs  304   a ,  304   b ,  306 . Accordingly, there is a conflict with redundancy in the NRT functionalities between the AC (NRT MAC  314 ) and AP 3   306  (NRT MAC  312 ). This conflict is further aggravated in other network topologies such as, for example, mesh networks, wherein AP functionalities are distributed over the entire mesh network and wherein direct communication between ACs and APs is not always possible. 
     Accordingly, it is desirable to provide a method and apparatus to resolve functional conflicts that arise in WLAN architectures. 
     SUMMARY 
     The present invention relates to a method and apparatus for configuring network nodes and resolving functional conflicts or redundancies that arise in network architectures. In a WLAN including at least one AC and a plurality of APs, the AC transmits functionality queries to the APs. Upon receiving these queries, the APs transmit query responses, which include the functional capabilities of the APs. The AC then generates a functional map of the functional capabilities available in the network based on the query responses. Conflicting or redundant functional capabilities are identified and are disabled, enabled, or reconfigured by instructions from the AC to the APs having conflicting or redundant functionalities. 
     A method for configuring nodes in a WLAN including an AC and an AP begins with the AC sending a functionality inquiry to the AP. The AP responds to the functionality inquiry by sending its functional capabilities to the AC. The AC maps the functional capabilities of the AP. A determination is made whether a capability conflict exists between the capabilities of the AP and the capabilities of the AC, wherein a conflict can include redundant capabilities between the AP and the AC. If there are any capability conflicts, they are resolved. 
     An AC for configuring nodes in a WLAN includes a transmitter/receiver, an inquiry device, a capability mapping device, and a capability evaluating device. The inquiry device is in communication with the transmitter/receiver and is configured to send functionality inquiry messages to an AP in the WLAN. The capability mapping device is in communication with the transmitter/receiver and is configured to receive functionality inquiry reply messages from the AP and to map the functionality capabilities of the AP. The capability evaluating device is in communication with the capability mapping device and is configured to determine if any functionality capability conflicts exist between the AP and the AC. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more detailed understanding of the invention may be had from the following description of a preferred embodiment, given by way of example, and to be understood in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a diagram of an infrastructure mode WLAN with a fat AP; 
         FIG. 2  is a diagram of a split architecture WLAN with thin APs; 
         FIG. 3  is a diagram of a hybrid WLAN architecture with both fat APs and thin APs; 
         FIGS. 4A ,  4 B, and  5  are flow diagrams of a method for resolving functionality conflicts or redundancies between an AC and an AP in the architecture shown in  FIG. 3 ; and 
         FIG. 6  is a block diagram of a system including an AC and an AP configured to perform the method shown in  FIGS. 4A ,  4 B, and  5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In a preferred embodiment, a WLAN including at least one AC and at least one AP is considered. The AC is preferably configured to split or remove certain L 2  MAC functionalities (e.g., NRT MAC functions) from the AP(s) and provide these functionalities to the network. An example of this configuration is shown in  FIG. 3 . Alternatively, the AC may provide all MAC layer functionalities to the network. As noted above, the AC may split and provide any functionality that is typically provided by the APs, including MAC layer functions, PHY layer functions, security methods, management interfaces, etc. 
     The present invention is not limited to the network deployment illustrated in  FIG. 3 . Rather, the present invention is applicable to any network deployment in which functional conflicts between network components occur. As previously described in connection with  FIG. 3 , there is a redundancy conflict with the NRT functionalities between the AC  308  and AP 3   306 , in that both the AC  308  and AP 3   306  attempt to provide L 2  NRT-MAC functionalities, creating a problem in the network  300 . 
     Overview 
     Utilizing a query-response mechanism, the AC queries all associated APs regarding their respective functional capabilities. Once responses are received from all associated APs, the AC utilizes the responses to generate a functional map of the different functional blocks available in the network. This functional map enables the AC to detect whether any APs are providing duplicate functionalities that may cause an operational conflict. 
     If an AP in the system fails to respond or is unable to respond to the AC&#39;s query, the AC may assume that the non-responding AP is capable of implementing all functionality modules and that a resulting functionality conflict exists. Failure to respond to the AC&#39;s query may indicate one of two possible scenarios: that an AP was implemented according to an alternate standard or that the AP is a legacy AP not capable of responding to the query. Since the AP will be assumed to be a fat AP capable of providing all possible functionalities, the AC stops support of the non-responding AP. 
     To resolve a detected conflict or redundancy, the AC generates and transmits a message to the AP ordering that the conflicting module in the AP be disabled or reconfigured to resolve the redundancy. Conflicts among network modules are preferably resolved based on the individual priority of the modules. Modules that reside higher in the network hierarchy (i.e., AC) are given higher priority than nodes that are lower in the hierarchy (i.e., APs). Disabling a module in the AP preferably occurs after a predetermined period of time (e.g., sync-up, future event, etc.), at which point the AC takes control of those functions for the AP and thus resolves the conflict. 
     It should be noted that the messaging means described above may also be used to enable functionalities, such as with a functionality enabling message. Additionally, the disabling, reconfiguring, and enabling of functionalities may occur during a system start-up phase or dynamically while the system is operating. Dynamic adjustments may be utilized, for example, to better distribute and re-balance processing power in a system based on functional maps and node priority. Similarly, dynamically adjusting functions may be preferred in certain architectures, such as mesh networks, wherein the AC functionalities are not situated in a single network node, but are distributed across various nodes. 
     It is noted that an AC may split and/or provide some or all MAC layer functions, while allowing the APs to provide some or all PHY layer or multiple PHY layer functions. Further, the approach described herein may be applied to other functionalities such as to multiple PHY layers, multiple radios (RFs), multiple security methods, multiple routing algorithms, different versions of a standard (e.g., 802.11e-WMS/WME/other), management interfaces (e.g., station management entity (SME)), etc., wherein the AC splits and provides these functions. 
     AR-AP Capability Signaling 
       FIGS. 4A ,  4 B, and  5  are flow diagrams of a method  400  for resolving functionality conflicts between an AC  402  and an AP  404 . Although the network is typically provided with a plurality of APs, only one AP  404  and its interaction with the AC  402  is shown for purposes of simplicity, it being understood that the AC  402  interrogates all other APs in the network in a like manner. As an initial step, the AP  404  starts up and enables all of its functionalities (step  406 ). 
     The AC  402  sends an inquiry to the AP  404  (step  410 ). The inquiry can be sent upon initial setup or upon the entry of a new node to the network, such that the system can correctly configure itself as quickly as possible. The inquiry can also be sent on a periodic basis (e.g., once a day as the system should not need to change too frequently) or by being triggered by a particular event (e.g., when a congestion condition arises, the capabilities are gathered as a pretext for load balancing). After the inquiry is sent, the AC  402  sets a timer for receiving a reply from the AP  404  (step  412 ). The AP  404  receives the inquiry (step  414 ) and replies to the AC  402  providing its functional capabilities (step  416 ). 
     There is a possibility that the AC  402  may send an inquiry to the AP  404  (step  410 ) and the AP  404  fails to respond, as indicated by the dashed lines for sending the inquiry and sending the reply. Failure to respond to the AC&#39;s query may indicate that an AP was implemented according to an alternate standard or that the AP is a legacy AP not capable of responding to the query. 
     After the timer has been set (step  412 ), a determination is made whether the AC  402  has received a reply from the AP  404  (step  418 ). If no reply has been received, then a check is made to determine whether the timer has expired (step  420 ). If the timer has not expired, the method  400  waits for a reply from the AP  404  (step  418 ). 
     If the timer has expired (step  420 ), this indicates that no reply was received from the AP  404 . The AC  402  defaults the AP  404  to having all possible capabilities (step  422 ). Since the AP  404  is presumed to have all possible capabilities (e.g., that the AP  404  is a fat AP), the AC  402  also halts support of services to the AP  404  (step  424 ). As applied to the scenario shown in  FIG. 3 , the AC  402  will not attempt to perform NRT-MAC scheduling for the AP  404  because the AP  404  is presumed to have this capability. 
       FIG. 4B  is a flowchart of an alternate method  450  for performing the initial steps of the method  400 . The AP  404  starts up and enables all of its functionalities (step  406 ). The AP  404  attempts to discover the AC  402  (step  452 ). The AP  404  can attempt to discover the AC  402  through various means. For example, the AC  402  could broadcast packets announcing its presence or a dedicated pre-agreed address on how to join the AC  402  could be known to all APs. After the AP  404  has discovered the AC  402 , the AP  404  sends its capabilities to the AC  402  (step  454 ). 
     If the AC  402  has received a reply from the AP  404  (step  418 ), if the AC  402  has set the AP  404  to having default capabilities (steps  422 ,  424 ), or if the AP  404  has sent its capabilities to the AC  402  (step  454 ), the AC  402  stores and maps the capabilities of all APs in the network (step  502 ;  FIG. 5 ). Next, the AC  402  determines whether the capabilities of any AP conflict or are redundant with the capabilities of the AC  402  or with the capabilities of another AP (step  504 ). The capabilities of other APs are checked for situations where there are different levels of APs or where APs have different priorities within the network. 
     As one example, assume that the AP  404  has a plurality of functional capabilities, at least one of which is the same as at least one of the capabilities of the AC  402 . In order to avoid any conflict within the network, the co-existence of the common function by both the AC  402  and the AP  404  necessitates that this co-existence be resolved by preventing the AP  404  from providing this functionality to other nodes within the network. The AC  402  may utilize an associative memory technique for comparing the AC functionalities with the AP functionalities. However, any other suitable technique for determining a conflict may be employed. 
     If there are any capability conflicts or redundancies (step  504 ), then the AC  402  sends a disable or reconfigure capabilities message to the AP  404  (step  506 ). In instances where an AP may have priority over another AP or other APs in the network, the AP having priority is permitted to support the functionality in issue and lower priority APs will have the functionality disabled or reconfigured. In situations where none of the APs have a higher priority level but are located at a higher level in the network architecture hierarchy, only the AP having the higher network hierarchy level is instructed to continue support of that functionality. In either case, the AC provides disabling or reconfiguring messages to APs at a lower network hierarchy level. 
     Additional factors considered by the AC include functional capabilities derived from cross-vendor components in which conflicts or redundancies arise due to differences in the components or due to one of the APs having superior operational capabilities compared with other APs in the network. This situation may arise where functional capabilities are shared in common with two APs, wherein one of which is a legacy AP, and the AC decides in favor of the more up to date module while disabling or reconfiguring the functional capability of the legacy AP. 
     The AP  404  receives the disable or reconfigure capabilities message (step  508 ) and disables or reconfigures any capabilities that conflict or are redundant with the AC&#39;s capabilities (step  510 ). After adjusting the capabilities according to the message, the AP  404  sends an acknowledgement (ACK) to the AC  402  (step  512 ). The AC  402  receives the ACK and updates the capabilities map with the current capabilities of the AP  404  (step  514 ). 
     The allocation of capabilities between and among the APs is not limited to MAC layer functions and PHY layer functions and may include security methods, management interfaces, and the like. For example, in mesh networks, the AC can allocate and split functional capabilities over the network in order to provide better balance within the network and to alleviate potential overloading of network nodes. Alternatively, security requirements may be utilized as the overriding factor in allocating and assigning functional capabilities between and among the APs. 
     If there are no conflicting capabilities or redundancies (step  504 ) or after the AC  402  has received the ACK and updated the capabilities map based on disabled or reconfigured capabilities (step  514 ), a determination is made whether any previously disabled capabilities of the AP  404  need to be enabled (step  516 ). This scenario may arise, for example, in a load balancing situation where the AC  402  wants to enable or reconfigure functions in the AP  404  that it had previously disabled or reconfigured. 
     If there are any capabilities that need to be enabled or reconfigured (step  516 ), then the AC  402  sends an enable/reconfigure message to the AP  404  (step  518 ). The AP  404  receives the enable/reconfigure message (step  520 ) and enables or reconfigures the capabilities listed in the message (step  522 ). After enabling or reconfiguring the capabilities according to the message, the AP  404  sends an ACK to the AC  402  (step  524 ). The AC  402  receives the ACK and updates the capabilities map with the current capabilities of the AP  404  (step  526 ) and the method terminates (step  528 ). 
     If there are no capabilities that need to be enabled or reconfigured (step  516 ), then the method terminates (step  528 ). 
     Exemplary System 
       FIG. 6  is a block diagram of a system  600  including an AC  602  and an AP  604  configured to perform the method  400 . The AC  602  includes a transmitter/receiver  610 , an antenna  612  connected to the transmitter/receiver  610 , an inquiry device  614  in communication with the transmitter/receiver  610 , a timer  616  in communication with the inquiry device  614 , a capability mapping device  618  in communication with the transmitter/receiver  610  and the timer  616 , and a capability evaluating device  620  in communication with the capability mapping device  618  and the transmitter/receiver  610 . 
     The AP includes a transmitter/receiver  630 ; an antenna  632  connected to the transmitter/receiver  630 ; a capability determining device  634  in communication with the transmitter/receiver  630 ; a station management entity (SME)  636  in communication with the capability determining device  634 , the SME  636  including a list of the capabilities of the AP  604 ; and a capability adjusting device  638  in communication with the transmitter/receiver  630  and the SME  636 . 
     In operation, the system  600  functions as follows. The inquiry device  614  sends an inquiry message to the transmitter/receiver  610  for transmission to the AP  604 . When the inquiry message is sent, the inquiry device  614  sets the timer  616 . The AP  604  receives the inquiry message via its transmitter/receiver  630 . The inquiry message is passed to the capability determining device  634 , which accesses the capabilities list in the SME  636  to determine the capabilities of the AP  604 . The capability determining device  634  then sends a reply message to the transmitter/receiver  630  for transmission to the AC  602 . 
     The reply message is received at the AC  602  and is passed to the capability mapping device  618 , which maps the capabilities of all APs in communication with the AC  602 . If the AC  602  does not receive a reply from the AP  604  and the timer  616  expires, and the capability mapping device  618  defaults the AP  604  to having all possible capabilities (i.e., the AP  604  will be considered to be a fat AP). 
     The capability evaluating device  620  examines the capability mapping for all APs and determines which APs have capabilities that conflict with the AC  602 . If there are any conflicting capabilities, the capability evaluating device  620  sends a disable or reconfigure message to the transmitter/receiver  610  for transmission to the AP  604 . Upon receipt of the disable or reconfigure message by the AP  604 , it is forwarded to the capability adjusting device  638  which disables or reconfigures the capabilities specified by the message by signaling the SME  636  which updates the capabilities list accordingly. Once the capabilities are disabled or reconfigured, the capability adjusting device  638  sends an ACK to the AC  602 . 
     In a similar manner, if the AC  602  instructs the AP  604  to enable or reconfigure any capabilities, the capability adjusting device  638  enables or reconfigures the capabilities specified by the AC  602  by signaling the SME  636  which updates the capabilities list accordingly. Once the capabilities are enabled or reconfigured, the capability adjusting device  638  sends an ACK to the AC  602 . 
     Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention. Although the various embodiments discussed above are described with reference to certain layers, it should be understood that any of the embodiments can be implemented in any layer or any combination of layers. Further, the features and elements of the present invention may be implemented on a single integrated circuit, such as an application specific integrated circuit (ASIC), multiple ICs, discrete components, or a combination of discrete components and ICs. Moreover, the present invention may be implemented in any type of wireless communication system.