Abstract:
Access is controlled to wireless access points connected in a wireless local area network (WLAN) providing telecommunications service for authorized users with wireless handsets. Identities of priority users are configured for a predetermined access point. Wireless users within range are associated to the predetermined access point. Bandwidth consumption data is aggregated corresponding to the associated wireless users. The aggregated consumption data is compared with a predetermined bandwidth capacity of the predetermined access point. If the aggregated consumption data is not less than the predetermined bandwidth capacity then use of the access point by a non-priority associated user having an identity that is not configured as one of the priority users is limited.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   Not Applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
   Not Applicable. 
   BACKGROUND OF THE INVENTION 
   The present invention relates in general to dual mode WLAN/WWAN telecommunication systems, and, more specifically, to maintaining Quality of Service (QoS) in the WLAN. 
   Wireless local area network (WLAN) telecommunication systems are being used in many workplace/office settings as an alternative to traditional, hardwired private branch exchange (PBX) and Centrex systems. WLAN systems comprise an array of wireless access points (AP&#39;s) deployed within a building connected by a wired LAN and communicating wirelessly with telephone appliances carried by individual system users. Each access point provides a respective coverage area such that coverage areas overlap and users can maintain a constant network connection as they move (i.e., roam) throughout the building. 
   WLAN systems provide many benefits over wired systems such as lower installation, upgrading, and maintenance costs. They provide a wide array of telephone features, which are easy to add and modify for new and existing users. Voice calls between users of the WLAN system are free of airtime or other charges. Gateways are used to interface the WLAN system with wireless wide area network (WWAN) systems such as cellular networks and with the public switched telephone network (PSTN) for establishing voice calls between WLAN users and conventional phone customers. 
   In dual mode WLAN/WWAN systems, a user&#39;s phone call is carried by the WLAN while in the workplace and is then handed off to the WWAN when the user moves out of range of the WLAN. Migration of active calls between the two networks is shown, for example, by United States Publication 2002/0085516A1, entitled “Automatic and Seamless Vertical Roaming Between Wireless Local Area Network (WLAN) and Wireless Wide Area Network (WWAN) While Maintaining an Active Voice or Streaming Data Connection: Systems, Methods and Program Products”. Preferably, a single phone appliance incorporates transceivers for operating with both networks so that the handoff between the two systems is transparent to the user. 
   Each wireless access point connected within a WLAN has a certain throughput capacity or bandwidth. Consumption of the bandwidth depends upon the number of users associated with the AP and their level of activity at any one time. When the aggregated traffic of all users approaches the bandwidth capacity of the AP, then issues of quality of service provided to the users arises. Typical mechanisms for controlling QoS give priority to one type of traffic over another or one class of subscribers over another. For example, it is known in WLAN systems to give priority to all voice traffic over any data services being accessed over the network. 
   The coverage area of any particular wireless access point may include workplace areas subject to different typical uses. For example, primary workstations such as an office desk of a user may be covered as well as transient or secondary work areas for all employees in a building such as conference rooms, file rooms, lunch rooms, or others. Consequently, the priority of voice over data traffic may not always be desirable. For example, a user at their desk may be accessing a data service via a particular access point, while a voice user who is roaming enters the particular access point coverage area. It may undesirable disrupt the data traffic of the user at their desk, especially when the voice call of the roaming user could be migrated to the WWAN system. 
   SUMMARY OF THE INVENTION 
   The present invention has the advantage of providing priority access to WLAN capacity for intended users who are “in zone” as opposed to transient traffic from “out-of-zone” users or visitors. 
   In one aspect of the invention, a method is provided for controlling access to wireless access points connected in a wireless local area network (WLAN) providing telecommunications service for authorized users with wireless handsets. Identities of priority users are configured for a predetermined access point. Wireless users within range are associated to the predetermined access point. Bandwidth consumption data is aggregated corresponding to the associated wireless users. The aggregated consumption is compared with a predetermined bandwidth capacity of the predetermined access point. If the aggregated consumption is not less than the predetermined bandwidth capacity then use of the access point by a non-priority associated user having an identity that is not configured as one of the priority users is limited. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing a dual mode WLAN/WWAN system of the present invention. 
       FIG. 2  is a block diagram showing a wireless access point and wireless access point controller in greater detail. 
       FIG. 3  is a flowchart showing a preferred method of the present invention. 
       FIG. 4  is a flowchart showing a preferred method for handling data traffic. 
       FIG. 5  is a flowchart showing a modified method for restoring access to lower priority users when capacity again becomes available. 
       FIG. 6  is a flowchart showing a preferred method for handling mixed voice and data services. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , wireless access points  10 ,  11 , and  12  are deployed in a building and interconnected by a local area network (LAN)  13 . AP&#39;s  10 ,  11 , and  12  provide coverage areas  14 ,  15 , and  16 , respectively, to provide overlapping coverage to support roaming of the users. A wireless access point controller  17  is connected to LAN  13  for providing centralized control of all the access points. Alternatively, separate controllers may be integrated within each access point. 
   Wireless devices for communicating with the access points include wireless telephone appliances  20 - 24  and personal computers  25  and  26  equipped with wireless transceivers. The foregoing WLAN system may be comprised of a Spectrum  24  system from Symbol Technologies, Inc., or a Link Wireless Telephone System (Link WTS) from SpectraLink Corporation, for example. LAN  13  is coupled to Internet  27  for exchanging data traffic therewith. Voice traffic may be exchanged with other telephone users via a gateway  28  connected to LAN  13 . Gateway  28  is connected to PSTN  29  and to a mobile telephone switching office (MTSO)  30 , which is part of a WWAN cellular telephone service. Thus, MTSO  30  is connected to a base station  31 , which is connected with a WWAN transmitter  32 . MTSO  30  may also be connected with Internet  27  for providing data services to the WWAN users. 
   Appliances  20 - 24  and PC&#39;s  25  and  26  are registered within the WLAN system so that they may access the network via any wireless access point. The present invention defines users as being “in-zone” for a predetermined wireless access point and grants the in-zone users priority in accessing the corresponding AP. In-zone status may be determined, for example, by the location of an employee&#39;s primary workstation or office and their typical mobility patterns (e.g., trips to a printer or location of shared documents). A particular user may be registered as an in-zone user of one or more access points. When connecting via any other access point, the user is “out-of-zone”. In addition to registered users not at their primary workstation, out-of-zone users may also include unregistered visitors when the WLAN is open to the public. 
   As shown in  FIG. 2 , AP  10  includes an antenna  35  connected to a transceiver/modulator/demodulator  36 . A baseband packet processor  37  is connected to transceiver  36  and to a network interface  38  for coupling with LAN  13 . An association table  40  keeps track of active wireless devices within the coverage area of AP  10  that are associated with (i.e., have been granted access to) AP  10 . AP controller  17  includes a media access control (MAC) processor  41  connected to a registration database  42 . Database  42  lists a terminal ID for each registered user on the WLAN system. In addition to the terminal ID, each database entry identifies the predetermined access points where the corresponding user is designated as being “in-zone”. Furthermore, each user may be assigned data rate bandwidths for accessing digital data services. Thus, a first user with a terminal ID of “TermID-1” is an in-zone user for an access point “AP-2” and is allocated data rates of 128 kilobits per second upload and 384 kilobits per second download. 
   AP controller  17  includes a capacity utilization module  43  coupled to MAC processor  41 . Based upon the identity of terminals associated with a particular access point, the services used by the identified terminals, and the allocated bandwidth corresponding to the services being used, capacity utilization model  43  determines the bandwidth capacity of each access point that is currently reserved. Furthermore, it compares the allocated bandwidth to a known capacity threshold for identifying when lower priority users should have their access limited in order to avoid degradation in quality of service for the higher priority users. 
     FIG. 3  shows a preferred overall method of the invention especially adapted for a voice WLAN system. The method starts at step  45  and proceeds to check in step  46  whether a predetermined capacity threshold of a predetermined access point has been reached. If not, then a return is made to step  46  in order to re-test the allocated capacity whenever new services are requested of the access point (e.g., when a new user attempts to associate with the access point). When the capacity threshold is reached, a check is made in step  47  to determine whether there are out-of-zone users presently associated with and using resources of the predetermined access point. If there are none, then no improvement can be made by limiting out-of-zone users and a return is made to step  46  for further monitoring. If there are out-of-zone users, then an out-of-zone user is migrated off the WLAN and onto the WWAN in step  48 . In step  49 , steps are taken to deny allocation of resources on the access point to any new out-of-zone users that attempt to associate with the access point since sufficient access point resources (i.e., bandwidth) are not available. 
     FIG. 4  shows an embodiment especially adapted for a WLAN providing data services. The method starts in step  50 . Each time new services are requested of the access point, a check is made in step  51  whether the allocated capacity of the access point reaches a predetermined capacity threshold. When the capacity threshold is reached, a check is made in step  52  to determine whether there are any out-of-zone users having an allocated data rate that is currently unthrottled (i.e., unreduced). Throttling of a user&#39;s data rate in effect reallocates the de-allocated bandwidth for other usage. If there are unthrottled out-of-zone users, then the data rate of one or more out-of-zone users is reduced in step  53  and a return is made to step  51  to handle further requests for service. If there are no unthrottled out-of-zone users, then a check is made in step  54  to determine whether there are any out-of-zone users currently using capacity of the predetermined access point (i.e., users who have had their data rates already reduced). If not, then no improvements can be made and a return is made to step  51 . If out-of-zone users are present, then their usage is preempted or they are migrated to the WWAN in step  55 . Preemption is comprised of denial of access to the WLAN. Support for data services by the WWAN is required when migrating an out-of-zone user to the WWAN. 
     FIG. 5  shows an optional method for reinstating usage by out-of-zone users when capacity again becomes available within the predetermined access point (e.g., as a result of other users disassociating from the access point).  FIG. 5  is a modification to the method shown in  FIG. 3 . After starting at step  45 , a check is made in step  56  to determine whether any limits have been put in place. If not, then the method proceeds with step  46  in the manner described above for  FIG. 3 . If limits are in place, then a check is made in step  57  to determine whether allocated bandwidth to all current in-zone and out-of-zone users has dropped below a predetermined threshold. This threshold is preferably lower than the capacity threshold used in step  46 . If usage has not dropped below the threshold then no restoration is needed and the method continues on in step  46 . When allocated bandwidth drops below the threshold, then limits on out-of-zone users are removed in step  58 . Thus, any reduced data rates are restored to their original levels and/or new associations of out-of-zone users are no longer denied. 
     FIG. 6  shows a preferred method for limiting out-of-zone users and/or lower priority services when the WLAN provides mixed services (i.e., a voice service and a data service). A first service S 1  (e.g., voice) is provided with a higher priority than a second service S 2  (e.g., data). A check is made in step  61  to determine whether allocated bandwidth of the access point has reached the capacity threshold. If yes, then a check is made in step  62  to determine whether there are out-of-zone users of service S 2 . If there are, then they are preempted or migrated off of the WLAN in step  63 . 
   If there are no out-of-zone S 2  users, then a check is made in step  64  to determine whether there are out-of-zone users of service S 1 . If so, then these users are preempted or migrated off of the WLAN in step  65 . If there are none, then there are no out-of-zone users having any allocated bandwidth on the predetermined access point (assuming there are no other services besides S 1  and S 2 ). 
   In step  66 , a check is made to determine whether there are in-zone users of service S 2  for whom the associated data rate is reducible. If so, then one or more of these in-zone users of service S 2  have their data rate throttled in step  67 . Otherwise, if there are no in-zone S 2  users whose data rate can be reduced, then a check is made in step  68  to determine whether the bandwidth being sought to be allocated (i.e., which caused the capacity threshold to be reached) is a request for the higher priority service S 1 . If so, then an in-zone user of the lower priority service S 2  is migrated to the WWAN in step  69 . Otherwise, no corrective actions can be taken and the method is finished at step  70 . 
   According to the foregoing invention, preferential treatment for WLAN access is given to in-zone users according to specific rules to determine the need for preemption or blocking of out-of-zone users from a particular access point and/or migration of the out-of-zone user&#39;s connection to another telecommunications network, such as a WWAN (e.g., cellular, PCS, or GSM networks). These rules can be different for voice sessions and data sessions. For example, the bandwidth required for a voice-over-WLAN call is a known quantity for a given WLAN system, and rules for migrating out-of-zone users can be invoked when current capacity usage increases such that there is insufficient reserve for in-zone users. These rules may be static (e.g., 5 users allowed per access point) or dynamic (e.g., based on load balancing). Likewise, specific enterprises may determine appropriate data rates to be allocated to each employee (e.g., 128 kbps upstream and 384 kbps downstream) and generate the rules accordingly. The rules may either completely block out-of-zone users when such capacity thresholds are reached, or be configured to allow some out-of-zone users and then preempt their sessions when in-zone users initiate sessions.