Abstract:
A wireless local area network (WLAN) includes a station, an access point (AP), and a network management entity (NME). A method for remote radio resource management in the WLAN begins by configuring a trigger condition at the AP. A determination is made whether the trigger condition has been met, and a notification message is sent from the AP to the NME if the trigger condition has been met.

Description:
CROSS REFERENCE TO RELATED APPLICATION(S)  
       [0001]     This application claims from the benefit of U.S. Provisional Application No. 60/488,060, filed Jul. 17, 2003, which is incorporated by reference as if fully set forth herein. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates to wireless local area network (WLAN) systems, and more particularly, to remote radio resource management (RRM) in a WLAN.  
       BACKGROUND  
       [0003]     Simple network management protocol (SNMP) is a widely utilized client-server based protocol allowing a remote network management entity (NME, i.e., an “agent”) to monitor network client devices. In a WLAN context, the agent is typically an access point (AP). The SNMP protocol allows retrieval of information from the client, via a GET command. Another feature of the SNMP protocol is that the client device (i.e., the AP) can send notifications to the NME.  
         [0004]     These notifications, or event-triggered reports, are widely used, for example, in the universal mobile telecommunications system (UMTS) for triggering measurement reports to inform the radio network controller (RNC) of critical situations such as handover, high interference levels in a cell, or a change in soft handover candidate cells. These notifications are an efficient means of keeping signaling overhead low in a mobile communications network.  
         [0005]     WLANs based on 802.11 have only three standardized notifications (Disassociate, Deauthenticate, and Authenticate Failure). These notifications are part of the standardized 802.11 management information base (MIB). With the move towards WLAN integration into multiple cell deployments, RRM can be used to maintain efficiency and inter-operability of WLAN access. Presently, there is no existing IEEE 802.11 standard relating to remote RRM (i.e., not implemented in the AP) to benefit from the signaling efficiency and traffic load reduction as allowed by event-triggered reporting in UMTS, for example.  
       SUMMARY  
       [0006]     A wireless local area network (WLAN) includes a station, an access point (AP), and a network management entity (NME). A method for remote radio resource management (RRM) in the WLAN begins by configuring a trigger condition at the AP. A determination is made whether the trigger condition has been met, and a notification message is sent from the AP to the NME if the trigger condition has been met.  
         [0007]     Another method for remote RRM in the WLAN begins by transmitting a request message from the station to the AP. The request message is processed at the AP, and is responded to by sending a response message from the AP to the station. The contents of the response message are evaluated at the AP and a notification message is sent from the AP to the NME based on the contents of the response message.  
         [0008]     A third method for remote RRM in the WLAN begins by measuring a parameter at the station and reporting the parameter from the station to the AP. The parameter is compared to a predetermined threshold at the AP and a notification message is sent from the AP to the NME if the parameter meets the threshold.  
         [0009]     A network management entity (NME) for remote radio resource management in a wireless local area network (WLAN) having a station and an access point (AP) includes receiving means for receiving a notification message from the AP, processing means for processing the notification message, and managing means for managing the radio resources of the WLAN based on the contents of the notification message.  
         [0010]     An access point (AP) in a wireless local area network (WLAN) having a station and a network management entity (NME) includes receiving means for receiving information from the station; processing means for processing the information and generating a notification message, the contents of the notification message based on the processed information; and transmitting means for transmitting the notification message to the NME. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     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:  
         [0012]      FIG. 1  is a block diagram of the IEEE 802.11 protocol stack;  
         [0013]      FIG. 2  is a flow diagram showing sending a notification message based on an association response frame;  
         [0014]      FIG. 3  is a flow diagram showing sending a notification message based on a reassociation response frame;  
         [0015]      FIG. 4  is a flow diagram showing sending a notification message based on a channel occupation value;  
         [0016]      FIG. 5  is a flow diagram showing sending a notification message based on a signal quality value;  
         [0017]      FIG. 6  is a flow diagram showing sending a notification message based on an in band interference value;  
         [0018]      FIG. 7  is a flow diagram showing sending a generic notification message when a trigger is activated at the AP; and  
         [0019]      FIG. 8  is a flow diagram showing an alternate embodiment of sending a generic notification message when a trigger is activated at the AP.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     The present invention can be implemented as an add-on to the WLAN IEEE 802.11 standards, including 802.11 baseline, 802.11a, 802.11b, and 802.11g, which are the basic WLAN air interface specifications. The present invention can also be implemented in other 802.11-based systems, in 802.16-based systems, and in other wireless network systems.  
         [0021]     There are three types of media access control (MAC) frames, or signaling messages, in the 802.11 specifications, including data frames (for carrying a payload), control frames (for example, for carrying acknowledgements), and management frames (for example, beacons). Generally speaking, there are several subtypes for each frame type. These frame types all have particular contents or information elements (IEs) as set forth in current 802.11 specifications.  
         [0022]     As shown in  FIG. 1 , a service primitive is an internal station signaling message used for inter-layer and/or inter-protocol entity exchanges (for example, from a station management entity (SME) to a MAC sublayer management entity (MLME) and vice versa) with standardized message contents. The particular format of the message is not specified by the standard (it can be implementation-specific); only the content is specified. This type of message is usually used to initiate and/or confirm an action such as sending a particular frame for management purposes to another station.  
         [0023]     To achieve remote RRM in a WLAN environment, the following set of signaling messages (station management (SMT) notifications) are proposed. Each of the messages is defined as a SMT notification. An SMT notification in accordance with a preferred embodiment of the present invention is a simple signaling message on the network side (functioning like a measurement report message from a Node B to a RNC in UMTS exchanged over the UMTS Iub/Iur interfaces). Basically, the AP sends SMT notifications as a kind of SNMP protocol message once certain conditions are fulfilled. The conditions can come from L1 and L2, and will likely contain measurements. Because SNMP is situated above L1 and L2 (the MAC layer), a UDP/IP message format would typically be used. An SMT notification can be exchanged by other means, such as from a station to an AP over the air interface carried by IP or a MAC management frame, or by encapsulating the SMT notification into a MAC frame.  
         [0024]     The notifications sent from the AP to the NME in accordance with the present invention can be in formats other than SMT notifications or SNMP messages. The notification could be formatted in Extensible Markup Language (XML) or be sent as service primitives exchanged between protocol entities, even if the protocol entities reside in the same physical piece of hardware. For example, a notification could be sent as a primitive across the service access point (SAP) from the MAC layer to the IP layer, with both layers residing on the station.  
         [0025]     For purposes of discussion of the operation of the present invention, it is assumed that the notifications will be sent using SNMP, and are also referred to herein as “SMT notifications.” It is noted that the present invention operates in the same manner regardless of the format of the notifications or the means used to send the notifications.  
         [0026]      FIG. 2  is a flow diagram showing notification messages sent by an AP  202  to a NME  204  depending upon the contents of an Association Response frame sent by the AP  202  to a station  206 . An Association Request frame is sent by the station  206  to the AP  202  in an attempt to associate the station  206  in the basic service set (BSS) with the AP  202  (step  210 ). The AP  202  in turn replies to the station  206  with an Association Response frame (step  212 ), which includes a status code indicating whether the association was successful or not, and if not successful, a reason code for the failed association. It is noted that the status codes used are the status codes set forth in the 802.11 standards.  
         [0027]     The AP  202  evaluates the status code contained in the Association Response frame (step  214 ). If the status code indicates a successful association, then the AP  202  sends an Associate notification to the NME  204  (step  216 ). The Associate notification includes the MAC address of the station  206  to which the Association Response frame was sent. If the status code does not indicate a successful association (step  214 ), then the AP  202  sends an Associate Failed notification to the NME  204  (step  218 ). The Associate Failed notification includes the MAC address of the station  206  to which the Association Response frame was sent and the reason for the association failure.  
         [0028]      FIG. 3  is a flow diagram showing notification messages sent by an AP  302  to a NME  304  depending upon the contents of a Reassociation Response frame sent by the AP  302  to a station  306 . A Reassociation Request frame is sent by a roaming station  306  to a new AP  302  in an attempt to reassociate the station  306  with the new AP  302  (step  310 ). The new AP  302  in turn replies to the station  306  with a Reassociation Response frame (step  312 ), which includes a status code indicating whether the reassociation was successful or not, and if not successful, a reason code for the failed reassociation.  
         [0029]     The new AP  302  evaluates the status code contained in the Reassociation Response frame (step  314 ). If the status code indicates a successful reassociation, then the AP  302  sends a Reassociate notification to the NME  304  (step  316 ). The Reassociate notification includes the MAC address of the station  306  to which the Reassociation Response frame was sent. If the status code does not indicate a successful reassociation (step  314 ), then the AP  302  sends a Reassociate Failed notification to the NME  304  (step  318 ). The Reassociate Failed notification includes the MAC address of the station  306  to which the Reassociation Response frame was sent and the reason for the reassociation failure.  
         [0030]      FIG. 4  is a flow diagram showing a Traffic Load notification message sent by an AP  402  to a NME  404  depending upon a channel occupation value sent from a station  406  to the AP  402 . A Traffic Load notification is a message to signal from the AP  402  to the NME  404  that the averaged experienced traffic load in the BSS exceeds a certain limit.  
         [0031]     The station  406  measures the channel occupation (step  410 ) and reports the channel occupation value to the AP  402  (step  412 ). The AP  402  compares the channel occupation value reported by the station  406  to a predetermined threshold (step  414 ). The threshold is exceeded when the average channel occupation ratio is higher than a predetermined percentage for longer than a predetermined time. It is noted that the baseline channel occupation ratio and the minimum time are implementation-specific. In one embodiment of the invention, the baseline channel occupation ratio is 30% and the minimum time is 10 minutes.  
         [0032]     If the channel occupation value exceeds the threshold, a Traffic Load notification is sent to the NME  404  (step  416 ). The Traffic Load notification includes the traffic load value as corresponding to a predetermined value. If the channel occupation value does not exceed the threshold (step  418 ), then the AP  402  waits for receipt of an updated channel occupation value, and continues with normal AP operation.  
         [0033]      FIG. 5  is a flow diagram showing a Low Signal Quality notification message sent by an AP  502  to a NME  504  depending upon a signal quality value sent from a station  506  to the AP  502 . A Low Signal Quality notification is a message to signal from the AP  502  to the NME  504  that a particular station is experiencing a low signal quality for a certain amount of time.  
         [0034]     The station  506  measures the signal quality (step  510 ) and reports the signal quality value to the AP  502  (step  512 ). The AP  502  evaluates the signal quality to determine whether the signal quality is below a predetermined threshold (step  514 ). The threshold is whether the average signal quality level is a predetermined percentage lower than a predetermined value for longer than a predetermined time. It is noted that the percentage difference, the baseline signal quality value, and the minimum time are implementation-specific. In one embodiment of the invention, the percentage difference is 50%, the baseline signal quality value is 10 dB signal to noise ratio (SNR), and the minimum time is 10 minutes.  
         [0035]     If the signal quality is below the threshold, then a Low Signal Quality notification is sent to the NME  504  (step  516 ). The Low Signal Quality notification includes the MAC address of the station experiencing low signal quality and its average signal quality level. If the signal quality value exceeds the threshold (step  518 ), then the AP  502  waits for receipt of an updated signal quality value, and continues with normal AP operation.  
         [0036]      FIG. 6  is a flow diagram showing an In Band Interference notification message sent by an AP  602  to a NME  604  depending upon an in band interference value sent from a station  606  to the AP  602 . An In Band Interference notification is a message to signal from the AP  602  to the NME  604  that the average experienced interference level in the BSS exceeds a certain limit.  
         [0037]     The station  606  measures the in band interference (step  610 ) and reports the in band interference value to the AP  602  (step  612 ). The AP  602  determines whether the in band interference value exceeds a predetermined threshold (step  614 ). The threshold is exceeded when the station  606  perceives an average interference level higher than a predetermined value in dBm for longer than a predetermined time. It is noted that the baseline interference level and the minimum time are implementation-specific. In one embodiment of the invention, the baseline interference level is −75 dBm and the minimum time is 10 minutes.  
         [0038]     If the in band interference exceeds the threshold, then an In Band Interference notification is sent to the NME  604  (step  616 ). The In Band Interference notification includes the interference level. If the in band interference value is below the threshold (step  618 ), then the AP  602  waits for receipt of an updated in band interference value, and continues with normal AP operation.  
         [0039]     The contents of each type of notification can vary by the station&#39;s MAC address, the reason code, the status code, and the error code. The notifications can be dependent on configuration by the NME. For example, an In Band Interference notification is sent when interference level as given by measurement A exceeds a configured threshold B for longer than C seconds, with the variables A, B, and C being configuration-specific or implementation-specific.  
         [0040]      FIG. 7  is a flow diagram showing a generic notification message sent by an AP  702  to a NME  704  after a trigger condition has been met. The NME  704  configures trigger conditions and transmits the trigger conditions to the AP  702  (step  710 ). In order for the trigger to be activated, one of two events can occur: some activity at the AP  702  (step  712 ) or a station  706  sends information to the AP  702  (step  714 ). It is noted that either one or both of the steps  712 ,  714  may satisfy the trigger conditions, and is dependent upon the trigger conditions set by the NME (hence, steps  712  and  714  are shown as dashed boxes, because both steps do not have to be performed). Step  712  can include AP-based events such as an internal AP measurement or other internal AP trigger. Step  714  can include any action taken by the station  706 , such as sending a request frame to the AP  702 .  
         [0041]     A determination is made whether the trigger conditions are met (step  716 ). If the trigger conditions are not met, then the AP  702  waits for additional activity, as indicated by steps  712 ,  714 . If the trigger conditions are met (step  716 ), then a notification is sent from the AP  702  to the NME  704  (step  718 ). The AP then returns to waiting for additional activity, as indicated by steps  712 ,  714 .  
         [0042]      FIG. 8  is a flow diagram showing an alternate embodiment of a generic notification message sent by an AP  802  to a NME  804  after a trigger condition has been met. The AP  802  configures trigger conditions (step  810 ). In order for the trigger to be activated, one of two events can occur: some activity at the AP  802  (step  812 ) or a station  806  sends information to the AP  802  (step  814 ). It is noted that either one or both of the steps  812 ,  814  may satisfy the trigger conditions, and is dependent upon the trigger conditions set by the NME (hence, steps  812  and  814  are shown as dashed boxes, because both steps do not have to be performed). Step  812  can include AP-based events such as an internal AP measurement or other internal AP trigger. Step  814  can include any action taken by the station  806 , such as sending a request frame to the AP  802 .  
         [0043]     A determination is made whether the trigger conditions are met (step  816 ). If the trigger conditions are not met, then the AP  802  waits for additional activity, as indicated by steps  812 ,  814 . If the trigger conditions are met (step  816 ), then a notification is sent from the AP  802  to the NME  804  (step  818 ). The AP then returns to waiting for additional activity, as indicated by steps  812 ,  814 .  
         [0044]     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. While specific embodiments of the present invention have been shown and described, many modifications and variations could be made by one skilled in the art without departing from the scope of the invention. The above description serves to illustrate and not limit the particular invention in any way.