Abstract:
The present invention reduces latencies in a wireless network while decreasing bandwidth usage in the wireless network for mobile stations. The wireless network monitors the current access network identifier for a mobile station. Upon detecting a change in current access network identifier due to movement of the mobile station, the wireless network generates and transmits one or more messages containing the changed current access network identifier. The messages are subsequently processed and a portion of the wireless system registrar database corresponding to the mobile station is updated to reflect the change in current access network identifier. Based upon the change in the location of the mobile station, the wireless network invokes or ends corresponding location-based options.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to communication systems, and more particularly, to a system and method for tracking a mobile station and invoking applications and user preferences based on the current location of the mobile station.  
       BACKGROUND OF THE INVENTION  
       [0002]     Conventional wide area wireless networks using Internet Protocol (IP) include several potential latency points. Upon a first mobile station (MS) initiating a call to a second MS, the network must poll the second MS to determine its location. This polling process not only takes time, but also consumes valuable bandwidth resources. Once the call has been established, in-session latencies can occur when the first and/or second MS changes from one access network to another access network due to movement of the first and/or second MS.  
         [0003]     Furthermore, a location-based application may fail to be invoked because the location of the MS is unknown. In addition, in some locations, multiple access networks may be available, for example a location may have both cdma2000 and Wi-Fi (IEEE 802.11 standard) wireless access available. While a user may have a preference as to the type of access network used, an application may not apply the user preference because it does not know the location of the MS. Alternatively, a location-based application may periodically poll the MS to determine its location. When the location-based application polls the MS and the MS has not moved, this leads to an inefficient use of the network&#39;s bandwidth resources. This is especially true when an access layer element within the network, such as a base station or packet control function, already has the location of the MS or the location of the MS has not changed.  
         [0004]     Accordingly, there is a need for a system and method for tracking a location of an MS to reduce both system latency and bandwidth usage. Further, there is a need for timely invoking location-based applications that depend upon the location of the MS. Additionally, there is a need for properly implementing user preferences that may similarly depend upon the location of the MS.  
       SUMMARY OF THE INVENTION  
       [0005]     A first embodiment of the invention is based upon a method for tracking a location of an MS based upon the identifier of the access network currently providing access for the MS. By detecting changes in the Access Network Identifier (ANID), the location of the MS can be tracked and a corresponding registrar database within the network can be updated. By detecting a change in the ANID at the access layer within a network, bandwidth at the application layer within the network is used only when the ANID actually changes. Thus, bandwidth at the application layer is conserved by not periodically polling an MS to determine if the MS has moved because the access layer already has this information. Updating the location of the MS stored in the registrar database therefore becomes an event-based function, not a periodic time-based function, thereby conserving application layer network bandwidth. Access layer bandwidth is also conserved as Radio Frequency (RF) bandwidth between a base station and various mobile stations will not be used for polling purposes that are initiated by the application layer.  
         [0006]     In a related embodiment, the method further comprises invoking location-based applications corresponding to the location of the MS. The method also comprises invoking corresponding location-based user preferences. Location-based options correspond to location-based applications and location-based user preferences.  
         [0007]     A further embodiment is a system for tracking a location of an MS based upon the ANID of the access network currently providing access for the MS. By detecting changes in the ANID, the network tracks the location of the MS and updates a corresponding registrar database. The system may invoke location-based options corresponding to the location of the MS.  
         [0008]     Another embodiment is a computer product for operating on one or more computers for tracking a location of an MS. The computer product causes the computer(s) to detect a change in the ANID and to update a corresponding registrar database based upon a change in MS location. The computer product can cause the computer(s) to invoke location-based options corresponding to the location of the MS. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     A more complete understanding of the present invention and its advantages will be readily apparent from the following Detailed Description taken in conjunction with the accompanying drawings. Throughout the accompanying drawings, like parts are designated by like reference numbers and in which:  
         [0010]      FIG. 1  is a schematic illustration of a cellular network in accordance with the present invention;  
         [0011]      FIG. 2  is a block diagram illustrating a protocol reference model for a cellular network in accordance with the present invention; and  
         [0012]      FIG. 3  is a flow diagram illustrating a method for tracking a location of a MS in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0013]      FIG. 1  schematically illustrates a representative environment of the present invention. An MS  100  (e.g., a cellular mobile telephone) wirelessly connects to a base station  105  via a radio frequency (RF) network (e.g., a cdma2000 network). The base station  105  connects to a base station controller (BSC)  110 , typically via a wire-line, such as a T1 line. The BSC  110  connects to and controls multiple base stations  105 . The BSC  110  connects to a Packet Control Function (PCF)  115  and to a Mobile Switching Center (MSC)  120 .  
         [0014]     The PCF  115  connects to a packet data serving node (PDSN)  130  via an RN-PDSN interface (RP). The Radio Network (RN) includes the PCF  115 , the BSC  110 , and the base station  105 . The PDSN  130  connects to an Authentication, Authorizing, and Accounting (AAA) proxy server  135  and to a core network  140 , both typically via wire-line. The core network  140  includes both a Session Initiation Protocol (SIP) proxy server  145  and a Cellular Serving System (CSS)  150 , also typically connected via a wire-line. The core network  140  connects to a communications network  155  (e.g., the Internet). For purposes of this patent, an access layer element within the wireless network corresponds to any element below the core network  140 , including, but not limited to, the MS  100 , the base station  105 , the BSC  110 , the PCF  115 , the MSC  120 , the PDSN  130 , and the AAA proxy server  135 . Furthermore, an application layer element within the wireless network includes, but is not limited to, the core network  140  itself, the SIP proxy server  145 , the CSS  150 , and the communications network  155 . Thus, the protocol stack distinguishes access layer elements from application layer elements.  
         [0015]     A second MS  160  (e.g., a cellular mobile phone) wirelessly connects to a second base station  165  via a second RF network. In the illustrated embodiment, the second RF network is not necessarily a cdma2000 network, but can use another type of wireless access technology. The second base station  165  connects to the communications network  155  via a number of intermediate devices (not shown) to allow the second MS  160  to communicate with the MS  100 . The present invention can be used to advantage in a wide area wireless network using Internet Protocol (IP) for communication between core networks. The present invention also applies to various wireless communication networks including, but not limited to, Wi-Fi, wireless local area networks (LAN), Wideband Code Division Multiple Access (WCDMA) networks, General Packet Radio Services (GPRS), and Third Generation (3G) networks.  
         [0016]      FIG. 2  illustrates a protocol reference model for a cdma2000 based access network in accordance with the present invention. The physical layer and link layer protocols would be different for other wireless access technologies. For interoperability, the protocols at the network layer and above use open standards. In this protocol model, call control is performed via the Session Initiation Protocol (SIP), and the media streams are conveyed over the Real Time Protocol (RTP), User Datagram Protocol (UDP), and Internet Protocol (IP).  
         [0017]     The protocol stack for the MS  100 , the base station  105 /PCF  115 , the PDSN  130 , the SIP proxy server  145 , and the CSS  150  are shown in  FIG. 2 . At the top of the protocol stack is the SIP, which provides for call control between the MS  100 , the PDSN  130 , and the CSS  150 . The data streams are then conveyed between the MS  100 , the PDSN  130 , and the CSS  150  via RTP/UDP/IP. A Radio Access Network (RAN) protocol is used for transmitting data from base stations  105  to the BSC  110 , between BSCs (not shown), and between the BSC  110  and an associated MSC  120 .  
         [0018]     At the link layer, the MS  100  communicates with the PDSN  130  via the point-to-point protocol (PPP), and with the base station  105 /PCF  115  via the link access control (LAC) and the medium access control (MAC) protocols. At the physical layer, the MS  100  communicates with the base station  105  via an air-interface using the Airlink protocol.  
         [0019]     The base station  105 /PCF  115  communicates with the PDSN  130  via radio protocol (RP) at the link layer, and via any number of protocols at the physical layer depending on the physical interconnections between the base station  105 /PCF  115  and the PDSN  130 .  
         [0020]     The PDSN  130  communicates with the SIP proxy server  145  via the same protocol stack of SIP/RTP/UDP/IP as the MS  100 . As the physical interconnections between the PDSN  130  and the SIP proxy server  145  are system dependent, the corresponding link layer protocols will also be system dependent. The PDSN  130  can also communicate with the AAA proxy server  135  associated with the MS  100 . The PDSN  130  then forwards data from the AAA proxy server  135  along with data from the base station  105 /PCF  115  to the SIP proxy server  145 . By employing various open protocols, communications between the MS  100  and the CSS  150  may be carried out independent of the number and types of physical interconnections therebetween.  
         [0021]     The relevant data to be passed through the networks illustrated in  FIGS. 1 and 2  will now be discussed. The ANID identifies the access network to which the MS  100  attaches, and consists of at least a Packet Zone Identifier (PZID), a System Identifier (SID), and a Network Identifier (NID). Thus, the ANID defines the packet zone or serving location of the PCF  115 , and therefore the location of the MS  100 . The ANID to which the MS  100  is currently attached is the Current ANID (CANID). The ANID to which the MS  100  was previously attached is the Previous ANID (PANID). The MS  100  transmits the ANID (which includes both the PANID and the CANID) to the base station  105  via the air-interface and from there to the PCF  115 . The MS  100 , upon detecting a change in PZID, temporarily opens a communication channel and transmits the ANID to the base station  105 . In other words, the MS  100  initiates the data transmission process based on the occurrence of an event, a change in PZID, not merely the passage of time. The PCF  115  subsequently forwards the ANID to the PDSN  130 . The PDSN compares the PANID and the CANID to determine if there has been a change in access network. A change in access network indicates a change in the location of the MS  100 . Note that while the PZID, the SID, and the NID define the ANID under the cdma2000 protocol, other wireless network protocols can employ other data components within an access network identifier. Because the present invention is applicable to other wireless network protocols, the term access network identifier or ANID includes any identifier that indicates the access network to which an MS  100  is attached.  
         [0022]     Upon detecting a change in access networks, the PDSN  130  generates a current access network bearer trigger message that is transmitted to the SIP proxy server  145 . This current access network bearer trigger message includes the CANID for the access network to which the MS  100  is currently attached. While bearer trigger messages are part of the cdma2000 protocol, other wireless network protocols include messages serving the same function of transmitting operational data within the wireless network. Therefore, a bearer trigger message will correspond more generally to a message specified by a wireless network protocol and used for transmitting operational data within the wireless network.  
         [0023]     The PDSN  130  requests data corresponding to location-based options from the AAA proxy server  135 . These location-based options can include presence status information and service subscription choices. These service subscription choices can include alerts based on weather or traffic issues and other multi-media services that may be integrated with cellular service. The service subscription choices can also include location-based service options, such as a connection access option in which Wi-Fi access is given preference over cdma2000 access when both are available in a given location. When data corresponding to location-based options is available, the current access network bearer trigger message generated by the PDSN  130  can include the location-based options as well as the CANID.  
         [0024]     Upon receiving the current access network bearer trigger message, the SIP proxy server  145  generates a corresponding current access network SIP register message that is transmitted to the CSS  150 . The current access network SIP register message includes a P-Access-Network-Info field. The P-Access-Network-Info includes both the CANID and any location-based options from the current access network bearer trigger message. Upon receiving the current access network SIP register message, the CSS  150  updates a portion of a registrar database contained therein with the CANID and any location-based options contained in the current access network SIP register message. While the registrar database is contained within the CSS  150  in this example, the registrar database can be located anywhere within the wireless network so long as the CSS  150  can update it. Furthermore, the registrar database can be any database a wireless service provider employs to track the status of an MS  100 . After updating the registrar database, the CSS  150  then causes any relevant location-based options to be invoked. When the relevant location-based options to be invoked are located on the CSS  150 , the CSS  150  simply starts the location-based option. Some relevant location-based options can be located on the MS  100 , the base station  105 , the PCF  115 , the PDSN  130 , the CSS  150 , or some combination thereof. In these cases, the CSS  150  invokes the location-based option by sending one or more messages to cause the corresponding element(s) to start the location-based option.  
         [0025]      FIG. 3  illustrates a flow diagram of a process for MS tracking in accordance with the present invention. The process tracks the CANID and revises a registrar database located in a memory (not shown) within the CSS  150  when changes in the CANID are detected. The process may invoke location-based options based upon the CANID.  
         [0026]     The process starts at step  300 . In step  305 , the CSS  150  registers the MS  100  upon the MS  100  being powered-up. In step  310 , the PCF  115  determines if the ANID provided by the MS  100  has changed due to a change in the location of the MS  100 . If there has been no change in the ANID, the PCF  115  continues to monitor messages from the MS  100  for possible changes in the ANID. If the PCF  115  detects a change in the ANID, the PCF  115  transmits the ANID, containing both the PANID and the CANID, to the PDSN  130  in step  315 . In step  320 , the PDSN  130  compares the PANID and the CANID to determine if they are identical. If the PANID and the CANID are identical, which would occur upon powering-up the MS  100 , then the process returns, and the PCF  115  continues to monitor messages from the MS  100  for possible changes in the ANID.  
         [0027]     If the PDSN  130  determines the PANID and the CANID are not identical in step  320 , this indicates the MS  100  has changed locations and further steps are taken. In step  325 , the PDSN  130  requests and receives data corresponding to location-based options from the AAA proxy server  135 . In step  330 , the PDSN  130  generates a current access network bearer trigger message containing the CANID and the location-based options. The PDSN transmits this current access network bearer trigger message to the SIP proxy server  145  in step  335 . In other words, the access layer transmits the CANID to the application layer of the wireless network. The SIP proxy server  145 , in step  340 , generates a current access network SIP register message with a P-Access-Network-Info field containing the CANID and the location-based options. The SIP proxy server  145  transmits the current access network SIP register message to the CSS  150  in step  345 . The CSS  150 , upon receipt of the current access network SIP register message in step  350 , revises the CANID and the location-based options portion of the registrar database associated with the MS  100 . In step  355 , the CSS  150  invokes any required changes corresponding to location-based options based upon the location of the MS  100  as reflected in the revised CANID. Such changes could include invoking any relevant location-based options. The entire process then repeats until the next change in CANID is detected.  
         [0028]     While the above describes the process whereby a location-based option is invoked, the invention contemplates the reverse as well. When an MS  100  changes location such that a given location-based option no longer applies, the CSS  150  will end the location-based option. As before, this may be at the CSS  150  level if the location-based option is on the CSS  150 . If the location-based option resides on one or more of the other elements in the wireless network, the CSS  150  will send the appropriate end massage(s) to the corresponding element(s).  
         [0029]     Although the present invention has been fully described by way of examples and with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention. Therefore, unless such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.