Abstract:
Method and apparatus for suppressing route request messages for wireless gateway applications by establishing a relationship between a serving mobile switching center identifier and a facility identifier at a wireless gateway switch. The wireless gateway switch determines a corresponding facility to the serving mobile switch in order to establish an incoming call to a wireless subscriber unit. An exemplary embodiment exploits the present invention in a wireless system utilizing ANSI-41 messaging.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of wireless communications, and, more specifically, to supporting an incoming call through a wireless gateway switch destined for a mobile subscriber unit. 
     BACKGROUND OF THE INVENTION 
     Mobile wireless communications is rapidly becoming ubiquitous throughout the world. A major goal of all mobile wireless service providers is to provide seamless service so that wireless service, including incoming calls, is available to a mobile subscriber unit wherever it is currently located. 
     Because of this cooperation among service providers, a mobile subscriber unit can roam from a service area of a serving mobile switching center (MSC) to a service area of another MSC. To facilitate seamless roaming, the wireless system registers the location of the mobile subscriber unit as the mobile subscriber unit moves from place to place. Location information is typically stored in a home location register (HLR), which may be a stand-alone entity (stand-alone HLR) or may physically reside at a home MSC (integrated HLR). A “home MSC” for a mobile subscriber unit is the MSC that serves the location where the mobile subscriber unit is primarily located. 
     FIG. 1 illustrates an exemplary incoming call for a roaming wireless subscriber unit in wireless system according to the prior art ANSI-41 messaging. The incoming call is initiated when telephone  101  dials the directory number of wireless subscriber unit  108 . The call is delivered to switching network  102  over facility  110 . Switching network  102  directs the incoming call to wireless gateway switch  103  via facility  111 . A “wireless gateway” switch is a portal or point of entry for calls from a public switch telephone network, such as  102 , to a wireless network. Wireless gateway switch  103  determines where mobile subscriber unit  108  is located by requesting HLR  104  for the location of mobile subscriber unit  108 . In order to do so, wireless gateway switch  103  sends a location request message  112  to HLR  104 . Message  112  contains the directory number of mobile subscriber unit  108  (DGTSDIAL field in the message). HLR  104  maintains a record that includes the location of mobile subscriber unit  108 , comprising the serving MSC  105  in which mobile subscriber unit  108  has last registered. A visiting location register (VLR)  106  record is maintained at serving MSC  105  while mobile subscriber  108  is located within the region served by MSC  105 . 
     In response to message  112 , HLR  104  sends a route request message  114  to the serving MSC ( 105  in this example) where the mobile subscriber unit last registered. Message  114  contains an IMSI field, which designates mobile subscriber unit  108 . Serving MSC  105  responds to HLR  104  with route request return result message  115 , which contains an MSCID field and TLDN field. MSCID field identifies serving MSC  105  and is represented as a 24-bit digital number (with 16 bits representing the system identification and 8 bits representing the switch number) in accordance with ANSI-41. TLDN field is a temporary local directory number that is subsequently utilized in the call scenario for delivering the incoming call to serving MSC  105 . HLR  104  conveys the information received in message  115  by sending location request return result message  113  (including MSCID field and TLDN field) to wireless gateway switch  103 . 
     Wireless gateway switch  103  delivers the incoming call to serving MSC  105 , as identified by MSCID field, over facility  117  designating a telephone number according to TLDN field. Serving MSC  105  continues the delivery of the call to a serving base station, in this example base station  107 , in which mobile subscriber unit  108  is located. Radio communications is established between serving base station  107  and mobile subscriber unit  108  over radio channel  119 , thus completing the call between telephone  101  and mobile subscriber unit  108 . Other standards, such as GSM mandate similar call setup message traffic. 
     With all the messages sent from place to place to establish each incoming call, message traffic on the wireless system (typically SS 7  in North America) is increased and call capacity is decreased. Also, because messaging is increased on a per call basis, the inherent time delay associated with call setup for an incoming call is increased. Moreover, TLDNs (for a wireless system complying with ANSI-41) and MRNs (for a wireless system complying with GSM-MAP) are required for completing the incoming call. If the number of TLDNs or MRNs that are assigned to a serving MSC is exhausted, the serving MSC cannot accept incoming calls until a TLDN or an MRN is relinquished from a previously established incoming call. In such a case, the service provider must either accept call blockage that is associated with the limited pool of TLDNs or MRNs or increase the size of the TLDN pool or MRN pool of the serving MSC&#39;s. TLDNs and MRNs are typically valid telephone numbers that can be otherwise assigned to a local revenue producing mobile subscriber unit. 
     SUMMARY OF THE INVENTION 
     The present invention effects an economical call setup to a mobile subscriber unit located within a gateway cluster. The gateway cluster comprises a wireless gateway switch and at least one MSC. The wireless gateway switch identifies a facility to a serving MSC from a new data structure according to the present invention. If the serving MSC is not in the gateway cluster, a facility to the serving MSC is identified by a method or apparatus according to prior art. 
     The present invention obviates a route request message between an HLR and a serving MSC including the temporary telephone number. A wireless gateway switch queries the HLR about the location of the mobile subscriber unit. The wireless gateway switch chooses a facility to the serving MSC according to a relationship between the serving MSC identifier (MSCID) that is provided by the HLR and a facility identifier. The wireless gateway switch utilizes a data structure in order to determine the facility identifier. In an exemplary example of the present invention, the facility identifier comprises a trunk group number. 
     Moreover, the present invention may be extended to call scenarios in which secondary call treatment is provided. The invention supports provisioning either the HLR or the wireless gateway switch with an indicator associated with each serving MSC of the gateway cluster. The indicator signifies whether the serving MSC is within the gateway cluster. The HLR utilizes the indicator to determine whether to generate a route request message to the serving MSC according to prior art or to suppress the route request message according to the present invention. 
     The exemplary embodiment exploits the present invention in a wireless invention utilizing ANSI-41 messaging and can be extended to GSM-MAP messaging. The exemplary embodiment supports incoming calls to the mobile subscriber unit and may result in providing secondary call treatment if the mobile subscriber unit does not respond to paging. The conservation of assignable telephone numbers allows for an increased number of mobile subscriber units that can be supported in a wireless system. Obviating the necessity of the two messages for an incoming call ameliorates the limitations imposed by the factors discussed heretofore. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows an incoming call scenario in a wireless system that supports a roaming wireless subscriber unit according to prior art as exemplified by ANSI-41 messaging; 
     FIG. 2 shows an incoming call scenario in a wireless system that supports a roaming mobile subscriber unit according to the present invention; 
     FIG. 3 illustrates a data structure utilized for delivering an incoming call to a serving MSC according to the present invention; 
     FIG. 4 shows an incoming call scenario with secondary call treatment in a wireless system that supports a roaming mobile subscriber unit according to prior art as exemplified by ANSI-41 messaging; 
     FIG. 5 shows an incoming call scenario with secondary call treatment in a wireless system that supports a roaming mobile subscriber unit according to the present invention; 
     FIG. 6 illustrates a flow diagram for the call scenario in FIG. 2; and 
     FIG. 7 illustrates a flow diagram for secondary call treatment for the call scenario in FIG.  5 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 2 illustrates a wireless system according to the present invention. Gateway cluster  403  comprises wireless gateway switch  400 , serving MSC  404 , serving MSC  405  and serving MSC  406 . (In the disclosure, a “gateway cluster” comprises a wireless gateway switch and at least one serving MSC in which a facility to a serving MSC from the wireless gateway switch is identified by a data structure, e.g., data structure  401 , according to the present invention. Wireless gateway switch  400  establishes an incoming call from telephone  101  to serving MSC  404 , serving MSC  405 , serving MSC  406  or serving MSC  105  depending on the location of mobile subscriber unit  108 . If mobile subscriber unit  108  is located within the region served by serving MSC  404 , serving MSC  405  or serving MSC  406 , wireless gateway switch  400  utilizes data structure  401  as described further, below, in connection with FIG.  3 . However, mobile subscriber unit  108  may be located outside the region served by gateway cluster  403 . For example, if mobile subscriber unit  408  is located within a region served by serving MSC  105 , wireless gateway switch  400  establishes the incoming call to serving MSC  105  over facility  117  utilizing a TLDN or MRN as described in relation to FIG.  1 . 
     As in FIG. 1, an incoming call is initiated by telephone  101  to switching network  102  over facility  110  by dialing the directory number of mobile subscriber unit  108 . Switching network  102  directs the incoming call to wireless gateway switch  400  through facility  111 . Wireless gateway switch  400  determines that mobile subscriber unit  108  is located within the region served by serving MSC  404  by sending a location request message  502  to HLR  504 . Message  502  contains DGTSDIAL field, which is the directory number of mobile subscriber unit  108 . HLR  504  determines that mobile subscriber unit  108  was last located in the region served by MSC  404  in which mobile subscriber unit  108  last registered. If MSC  404  is contained in gateway cluster  403 , HLR  504  does not request a temporary local directory number from serving MSC  404 . In the exemplary embodiment, an indicator, which is an entry in a database, is provisioned at HLR  504  for each serving MSC to specify if the serving MSC is contained in gateway cluster  403 . The indicator is determined according to whether wireless gateway switch  400  shall select facility  407  by utilizing data structure  401 . Data structure  401  is discussed in the subsequent discussion of FIG.  6 . Otherwise, wireless gateway switch  400  utilizes a TLDN to connect the incoming call as described previously in connection with FIG.  1 . 
     A gateway cluster (e.g. gateway cluster  403 ) can be configured so that a mobile to mobile call (in which a second mobile subscriber unit within the gateway cluster calls a first mobile subscriber unit also within the gateway cluster) is processed as an incoming call according to the present invention. For example, the serving MSC (e.g. serving MSC  404 ) routes the call to the wireless gateway switch (e.g. wireless gateway switch  400 ) through a loop-around facility (as is known in the art) so that the call from the second mobile subscriber unit appears as an incoming call to the first mobile subscriber unit. 
     In the exemplary embodiment, an indicator is provisioned at HLR  504  for each serving MSC. A technician provisions each indicator by inputting commands to terminal  506  through interface  507 . Alternative embodiments can implement the indicators at serving gateway switch  400  as can be appreciated by one skilled in the art. HLR  504  responds with location request return result message  503 , which contains an MSCID field and RoutingDigits field. HLR  504  determines a value for RoutingDigits field according to the corresponding indicator. 
     FIG. 3 illustrates data structure  401  that is utilized by wireless gateway switch  400  for delivering the incoming call to serving MSC  404  according to the present invention. MSCID, as contained in MSCID field  154 , is used by wireless gateway switch  400  as an index to network neighbor database  601  to fetch corresponding database entry  603 . Database entry  603  comprises route index  604 . 
     Route index  604  is used as an index to facility database  602  to fetch corresponding database entry  607 . Database entry  607  comprises facility identifier  608 . In the exemplary embodiment, facility identifier  601  comprises a trunk group number from which wireless gateway switch  400  chooses a trunk member number. Wireless gateway switch  400  establishes the incoming call over facility  407  corresponding to the trunk group number and trunk member number. As appreciated by one skilled in the art, alternative embodiments can implement facility identifier  601  as directly identifying both the trunk group number and trunk member number, however. 
     FIG. 4 illustrates a prior art incoming call scenario as in FIG. 1, except that mobile subscriber unit  108  is not available and subsequent secondary call treatment is determined. As in FIG. 1, the incoming call is delivered to serving MSC  105  over facility  117 . However, mobile subscriber unit  108  is currently communicating on another call to serving base station  107  over radio link  119 . Other examples include call scenarios in which mobile subscriber unit  108  is powered down and mobile subscriber unit  108  is not responding to paging messages because of poor coverage of the RF channel. If mobile subscriber unit  108  is unavailable, serving MSC  105  sends redirection request message  302  with redirection reason field, which indicates the reason for mobile subscriber unit  108  not being available to wireless gateway switch  103 . Wireless gateway switch  103  consequently sends transfer to number request message  304  with an IMSI field. The IMSI field identifies mobile subscriber unit  108  to HLR  104 . HLR  104  responds with transfer to number request return result message  350  containing transfer DN field, which designates the directory number of voicemail unit  301 . Consequently, wireless gateway switch  103  redirects the incoming call from facility  111  to voicemail unit  301  through facility  306 . 
     In the call scenario shown in FIG. 4, the secondary treatment is to redirect the incoming call to voicemail unit  301 ; however, alternative types of secondary call treatment include redirecting the incoming call to an announcement or to another mobile subscriber unit. 
     FIG. 5 shows an incoming call scenario with secondary treatment to mobile subscriber unit  108  in a wireless system according to the present invention. The call scenario in FIG. 5 is similar to the call scenario in FIG. 2 except that mobile subscriber unit  108  is not available. When wireless gateway switch  400  determines that mobile subscriber unit  108  is not available, the call scenario in FIG. 5 proceeds as in FIG. 2 to determine the secondary call treatment. 
     FIG. 6 illustrates a flow diagram for the call scenario shown in FIG.  5 . In step  801 , the incoming call is connected to wireless gateway switch  400 . Wireless gateway switch  400  sends location request message  502  to HLR  404  in step  803 . In step  805 , if mobile subscriber unit  108  is located in the region served by gateway cluster  403 , step  807  is executed. If mobile subscriber unit  108  is not located in gateway cluster  403 , HLR  504  sends route request message  114  to serving MSC  105  as shown in FIG.  1 . In such a case, wireless gateway switch  400  utilizes a TLDN to route the incoming call to serving MSC  105  as shown in FIG.  1 . 
     In step  807 , HLR  504  responds with location request return result message  503  to wireless gateway switch  400  with MSCID field  154 , instructing wireless gateway switch  400  to utilize data structure  401  to route the incoming call. In step  808 , wireless gateway switch  400  determines facility identifier  608  from MSCID field  154 . In step  809 , serving MSC  404  pages mobile subscriber unit  108 . If mobile subscriber unit  108  responds, the incoming call is completed in step  812 . If mobile subscriber unit  108  does not respond to the page, step  811  is executed and secondary call treatment is determined according to the call flow in FIG.  7 . 
     FIG. 7 illustrates a flow diagram for secondary treatment for the call scenario shown in FIG.  5 . In step  901 , serving MSC  105  determines that mobile subscriber unit  108  is not available. Consequently, serving MSC  105  sends redirection request message  302  to wireless gateway switch  400 . In step  903 , wireless gateway switch  400  sends transfer to number request message  304  to fTLR  504 . In step  904 ,  1 LR  504  responds with transfer to number request return result message  305  with the routing number of voicemail unit  301 . In step  905 , secondary call treatment is provided. With the example shown in FIG. 5, secondary call treatment is provided by voicemail unit  301  although other types of secondary treatment (e.g., an announcement) can be provided. 
     It is to be understood that the above-described embodiment is merely an illustrative principle of the invention and that many variations may be devised by those skilled in the art without departing from the scope of the invention. It is, therefore, intended that such variations be included with the scope of the claims.