Abstract:
An apparatus and method in a telephone communications system that provide for redirecting a call by an adjunct processor, utilizing a control message. The control message contains various directives for current or subsequent execution by a telephone switching center, which can assume a function of a mobile switching center in a wireless communications system or a landline switching center in a landline telephone system. Directives in the control message instruct the telephone switching center to redirect a call contingent upon subsequent call events that can occur.

Description:
FIELD OF INVENTION 
     This invention relates to a telephone communications system enabling call redirection for subsequent call events. 
     BACKGROUND OF THE INVENTION 
     With telephone communications systems, services may require call redirection to an alternate call destination dependent upon events that occur during the duration of the call. With the current state of the art, the initiation of the call redirection is caused by a call event that has already occurred. The prior art supports call redirection in one of three ways. The most common approach is to “camp on” the call by “hairpinning” the call through an adjunct processor using telephone facilities. This enables the adjunct processor to monitor the call throughout the duration of the call. However, hairpinning can add substantial cost to the service because additional transmission facilities are required. If a specified call event is detected by the adjunct processor, the adjunct processor instructs the telephone switching center to establish another call to a specified call destination. 
     With the second approach, hairpinning is not utilized. Rather, a call between a telephone unit and an adjunct processor is established. From the dialog that occurs during the call, the adjunct processor determines that the call should be redirected to another telephone designation. A connection is established from the telephone unit and the telephone designation. At this time, the adjunct processor is not involved with the call and thus is not active in subsequent call processing. 
     With the third approach, a call between a telephone unit and an adjunct processor is established, enabling dialog between the adjunct processor and the telephone unit to occur. The call is consequently redirected to another telephone designation. Moreover, the adjunct processor sends an enabling trigger to the telephone switching center over a control link. If the specified call event occurs, the telephone switching center sends a query message over the control link to the adjunct processor, asking for the appropriate action to be taken. The adjunct processor responds with a redirection message that contains a specified call destination. 
     FIG. 1 corresponds to the hairpinning approach (the above-described first approach) and illustrates an architecture as embodied in prior art for attaching adjunct processor  103  to mobile switching center (MSC)  102  in order to provide wireless services. In this architecture, mobile subscriber unit  100  is provided services by MSC  102  through base station  101 . Mobile subscriber unit  100  communicates with base station  101  over radio channel  106  requesting a call. Both control messages as well as voice transmission are supported by radio channel  106 . Voice transmission is supported over facility  107  to a switching fabric contained in MSC  102 . Adjunct processor  103  monitors and relays voice transmission to public switching telephone network (PSTN)  104  over facility  108  to facility  109 . PSTN  104  establishes a voice connection to designated party  105  according to dialed digits entered by either mobile subscriber unit  100  or designated party  105  thus completing the call. 
     Adjunct processor  103  can reside at one of a number of network entities that are associated with a wireless intelligent network, including an intelligent peripheral (IP), a service node (SN), or a service control point (SCP). The IP performs specialized resource functions such as playing announcements, collecting digits, performing speech-to-text or text-to-speech conversions, recording and storing voice messages, and so forth. The SCP is a real-time database and transaction processing system that provides service control and service data functionality. The SN combines the capabilities of an IP and an SCP. 
     If adjunct processor  103  detects that a particular call event occurs during the call between mobile subscriber unit  100  and party  105 , such as a disconnect indication from party  105 , adjunct processor  103  issues control redirection message  110  to PSTN  104  to reconfigure a voice path between mobile subscriber unit  100  and party  111 . Redirection message  110  is typically transported on a separate control link. PSTN  104  subsequently establishes a voice path through PSTN  104  to party  111 . 
     FIG. 2 corresponds to the above described second approach and illustrates a wireless communications architecture utilizing a redirection directive in accordance with prior art. Mobile subscriber unit  120  communicates with base station  121  over radio channel  126  requesting a call. Voice transmission is supported over facilities  127  and  128  to adjunct processor  123  through MSC  122 . Consequently, a full-duplex connection is established between a user of mobile subscriber unit  120  and adjunct processor  123 , from which it is determined that the call should be redirected to telephone unit  125 . Adjunct processor  123  sends redirection message  130  to MSC  122 , instructing MSC  122  to establish voice connection  129  through PSTN  124  to party  125  and to remove voice connection  128 . Thus, a voice path is completed between mobile subscriber unit  120  and party  125 . At this time, adjunct processor  123  is no longer active with the call. 
     FIG. 3 corresponds to the above described third approach and illustrates an architecture using a two-stage approach as embodied in prior art for attaching adjunct processor  152  to landline switching center  151  in order to provide landline telephone services. With landline advanced intelligent networks, landline switching center  151  is typically identified as a service switching point SSP. In this architecture, telephone unit  150  is provided service by telephone switching center  151 . However, as appreciated by one skilled in the art, this architecture is applicable to wireless services by incorporating a plurality of base stations, replacing landline switching center  151  with a mobile switching center, and utilizing mobile subscriber units as telephone units. Moreover, the term “telephone unit” is applicable to a variety of telephone instruments including wired telephone sets, cordless telephones, mobile subscriber units, fixed wireless telephone sets and so forth. 
     In FIG. 3, telephone unit  150  communicates with landline switching center  151 , requesting a call. This request is physically conveyed by a signal, which can be a digital message, on facility  156 . Moreover, facility  156  also transports voice transmission once the call is established. Landline switching center  151  completes the call to party  154  over facility  157  through PSTN  153 . Adjunct processor  152  is notified of the call by landline switching.center  151  by sending message  158  to adjunct processor  152 . Messages  158 ,  159 ,  160 , and  161  are transported on a control link between landline switching center  151  and adjunct processor  152 . 
     Adjunct processor  152  arms landline switching center  151  in order to prepare landline switching center  151  for the possibility of a subsequent call event identified in arm event message  159 . For advanced intelligent networks, arm event message  159  is specified as the Request_Report_BCM_Event message in Bellcore GR-1298-CORE and GR-1299-CORE, Issue 4, Revision 1, October 1998, pages 4-1 to 4-15 (SSP Processing of Triggers and Requested Events). Landline switching center  151  continues to process and monitor the call until the call event as specified in arm event message  159  occurs. If the call event occurs, landline switching center  151  stops processing, sends event query message  160  to adjunct processor  152 , and waits for response message  161  from adjunct processor  152 . GR-1298 and GR-1299 specify the event query message as the EDP-Request message for advanced intelligent networks. Adjunct processor  152  returns response message  161 , which instructs landline switching center  151  about subsequent action, such as redirecting the call to a different party. 
     The present invention obviates the need for the adjunct processor to monitor the call or the need for a two-stage approach (the above described third approach) for redirecting the call while affecting a call contingent upon subsequent call events. 
     SUMMARY OF THE INVENTION 
     The apparatus and method of the present invention enables a telephone communications system to redirect a call by an adjunct processor, utilizing a control message having various directives for current and subsequent execution by a telephone switching center. The telephone communications system can function as a mobile switching center in a wireless communications system or a landline switching center in a landline telephone system. The adjunct processor may be implemented within a service control point, a service node, or an intelligent peripheral. 
     The adjunct processor includes program instructions to generate a control message in response to a request for telephone service, such as in response to a dialog between a user of a telephone unit and the adjunct processor. The telephone switching center includes program instructions to receive the control message, to redirect the call, and to redirect the call again in response to call events that may occur during the call when first redirected. 
     The control message contains a initial redirection telephone number associated with the first redirection and with designated telephone numbers associated with subsequent call events that can occur during the call after the call is redirected to the initial redirection telephone number. Alternatively, the control message may contain only designated telephone numbers associated with subsequent call events that can occur during the call in which the telephone unit is currently active. 
     Numerous other advantages and features of the present invention will become readily apparent from the detailed description of the invention and the embodiments thereof, from the claims, and from the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a wireless communications architecture using an hairpinning configuration in accordance with prior art; 
     FIG. 2 illustrates a wireless communications architecture utilizing a redirection directive in accordance with prior art; 
     FIG. 3 illustrates a wireline telephone architecture in which the two-stage approach for control messaging is utilized in accordance with prior art; 
     FIG. 4 illustrates an architecture for a single-stage redirection approach for a wireless communications system; 
     FIG. 5 illustrates a message structure for a modified ANSI-41 Redirection Directive message; 
     FIG. 6 is a block diagram of a telephone network illustrating an exemplary embodiment of the present invention; 
     FIG. 7 is a flow diagram illustrating the logic for the single-stage redirection approach; 
     FIG. 8 illustrates a voice mail application utilizing the single redirection approach for a mobile-origination call in a wireless communications system; and 
     FIG. 9 illustrates a voice message application utilizing the single redirection approach for a mobile-terminated call in a wireless communications system. 
    
    
     DETAILED DESCRIPTION 
     FIG. 4 illustrates an architecture in accordance with the present invention. In this architecture, only one redirection message is utilized. Thus, this architecture is referred to as a “single-stage” redirection approach. As in FIGS. 1 and 2, mobile subscriber unit  200  establishes a connection with base station  201  over radio channel  206  in order to support a call request. The connection is extended to MSC  202  over facility  207 . Adjunct processor  203  is notified by MSC  202  sending, for example, an ORREQ message  209  to adjunct processor  203 . Adjunct processor  203  acknowledges ORREQ message  209  by returning orreq message  210  to MSC  202 . In this exemplary embodiment, a call is established between adjunct  203  and mobile subscriber unit  200  over facilities  207  and  211  so that a dialog occurs between adjunct processor  203  and a user of mobile subscriber unit  200 . 
     From this dialog, adjunct processor  203  determines that the call should be redirected and thus sends redirection message  212  to MSC  202 . With the inclusion of a initial redirection telephone number, redirection message  212  instructs MSC  202  to reconfigure the call to party  205  over facility  208  through PSTN  204  and to remove facility  211 , thus completing the call. Contingent upon the occurrence of a future call event during the call between mobile subscriber  200  and party  205 , the call is redirected to party  213 . Redirection message  212  contains the initial redirection telephone number of party  205 , the designated telephone number of party  213 , and the call event associated with the designated telephone number of party  213 . (The structure of redirection message  212  is illustrated in FIG.  5  and is discussed subsequently.) Party  213  may correspond to another mobile subscriber unit, wireline telephone, or processor such as adjunct processor  203 . 
     Other embodiments include call scenarios in which there is no dialog between adjunct processor  203  and mobile subscriber unit  200 . In such cases, adjunct processor  203  is notified of the call at some time during the middle of the call. Thus, redirection message  212  may not contain an initial redirection telephone number but only at least one designated telephone number. 
     While FIG. 4 depicts an architecture of a wireless system, messages  209 ,  210  and  212  are also applicable to a landline telephone system. In such an arrangement, MSC  202  is analogous with a landline switching center (similar to that shown as landline switching center  151  in FIG.  2 ), mobile subscriber unit  200  is replaced with a telephone unit (similar to that shown as telephone unit  150  in FIG.  2 ), and base station  201  is removed, whereby the telephone unit directly communicates with the landline switching center over a facility. 
     FIG. 5 illustrates an exemplary embodiment of a message structure corresponding to redirection message  212  in accordance with ANSI-41 message REDDIR  250 . ANSI-41 is specified in Telecommunications Industry Association/Electronic Industries Association TLA/EIA SP-3588 Cellular Radio Telecommunications Intersystem Operations. The first parameter of REDDIR  250  is BillID parameter  251 , which currently exists in ANSI-41 and is not relevant to the present invention. Digits parameter  252 , which is an existing parameter in ANSI-41, corresponds to the initial redirection telephone number of party  205 . Electronic Serial Number parameter  253  and Mobile Identification Number parameter  254  identifies the mobile subscriber unit associated with the call. Other parameters  255  is currently supported parameters in ANSI-41 that are not relevant to the present invention and is shown to illustrate the message structure of message REDDIR  250 . Additional parameters CallBackBusy  256 , CallBackNoAns  257 , CallBackFERel  258 , CallBackMobRel  259 , and CallBackDefault  260  are included in REDDIR message  250  in order to support the single-stage redirection in accordance with the present invention. With this exemplary embodiment, the occurrence of future call events busy, no answer, far-end release, and mobile release correspond to parameters call back busy  256 , call back no answer  257 , call back far-end release  258 , and call back mobile release  259 , respectively. Each of these parameters contains a designated telephone number corresponding to a specified call event that may occur subsequently to generating REDDIR message  250 . If any of parameters  256 ,  257 ,  258 , or  259  does not contain a designated telephone number, the designated telephone number in CallBackDefault parameter  260  is used for the corresponding call event. 
     The functionality of parameters  254 ,  255 ,  256 ,  257 , and  258  can be added to other standardized messages utilized in wireless services. One example is the CallControlDirective message as specified in Telecommunications Industry Association/Electronics Industries Association TIA/EIA PN-4287 (Wireless Intelligent Network Capabilities for Pre-Paid Charging). This example, as well as other examples that may be developed in the future, can be appreciated by one skilled in the art. 
     FIG. 6 is a block diagram illustrating an apparatus embodiment  300  in accordance with the present invention. Apparatus  300  may be distributed between MSC  202  and adjunct processor  203 . The functionality of adjunct  203  may reside on an intelligent peripheral, a service node, or a service control point. 
     Referring to FIG. 6, apparatus  300  includes processor  302 , network interface  301 , and memory  303 . Network interface  301  detects specified call events, receives incoming calls, and initiates outgoing calls, generates control messages, and receives control messages. Network interface  301  may be couplable to PSTN  204  for transmission and reception of PSTN (wireline) calls or couplable to transmission and reception of wireless calls at base station  201 . Memory  303  may be a magnetic hard drive, an optical storage device, or any other type of data storage apparatus and is used to store program instructions. In addition, memory  303  may also store information pertaining to types of services and subscriber classes, call placement, and routing information. Processor  302  may include a single integrated circuit or may include a plurality or integrated circuits or components connected, arranged, or grouped together. As used herein, the term “processor” should be understood to equivalently mean and include a single processor, an arrangement of processors, microprocessors, controllers, or some other grouping of integrated circuits which perform functions as will be discussed in relation to FIG.  7 . Memory  303  contains the corresponding program instructions that perform the functions as shown in FIG.  7 . 
     FIG. 7 is a flow diagram illustrating the logic for the single-stage redirection approach which may be represented in programming instructions, stored in memory  303 , and executed by processor  302 . Step  400  starts the process shown in FIG.  7  and is initiated by a call from the mobile subscriber unit to the adjunct processor. In step  401 , based upon the dialog with the user of the mobile subscriber unit, the adjunct processor redirects the call to a party that previously called the mobile subscriber unit and left a message. The dialog and the message may assume a variety of formats and are not limited to voice, text, or dual tone multi-frequency (DTMF) characters. 
     The redirection message from the adjunct processor to the telephone switching center provides the initial redirection telephone number of the party as well as designated telephone numbers to which the call should be redirected a second time if specified call events subsequently occur during the redirected call between the mobile subscriber unit and the party. With this exemplary embodiment in step  402 , the telephone switching center monitors for the specified call events during the directed call. In step  403 , the call is redirected to appropriate designated telephone number corresponding to the call event that occurs first. In step  404 , the adjunct processor determines if the process as shown in FIG. 7 should be repeated. If so, step  401  is repeated; otherwise, the process is exited in step  405 . As an example, there may be additional messages for the telephone unit. In step  404 , according to an exemplary embodiment, the designated telephone number of step  403  corresponds to the adjunct processor. However, other embodiments do not require that the call be redirected back to the adjunct processor but rather redirected to another designated telephone number. In such an embodiment, step  404  is not implemented; rather the process is exited. 
     FIG. 8 is a call flow diagram illustrating a voice mail service that utilizes the single redirection approach for a mobile-origination call in a wireless communications system. Mobile subscriber unit  500 , base station  501 , MSC  502 , voice mail application  503 , PSTN  504 , and party  505  correspond to mobile subscriber unit  200 , base station  201 , MSC  202 , adjunct processor  203 , PSTN  204 , and party  205 , respectively. Mobile subscriber unit  500  initiates the mobile-origination call by sending origination message  506  to base station  501 .Origination message  501  contains dialed digits of the form “*xy”, where “x” and “y” are digits from  0  to  9 . The dialed digits signify that a user of mobile subscriber unit  500  wishes to establish a connection to voice mail application  503  in order to retrieve voice messages from previous callers. In response to receiving origination message  506 , base station  501  establishes a voice connection between mobile subscriber unit  500  and base station  501  and sends setup message  507  that relays dialed digits “*xy”. Also, voice connection  511  is established between base station  501  and MSC  502 . MSC  502  translates digits “*xy” and determines that message trigger (ORREQ)  508  must be sent to voice mail application  503 . Voice mail application  503  returns response message (orreq)  509  to MSC  502 . Message  509  contains a routing telephone number so that MSC  502  can complete voice connections  512  and  513  between MSC  502  and PSTN  504  and between PSTN  504  and voice mail application  503 , respectively. Voice connections  510 ,  511 ,  512 , and  513  constitute the voice path between mobile subscriber unit  500  and voice mail application  503 . 
     A dialog is established between voice mail application  503  and the user of mobile subscriber unit  500 . In FIG. 8, it is determined that the user wishes to call back party  505  that left a voice message, which voice mail application  503  has played for the user. Thus, voice mail application  503  sends REDDIR message  514  to MSC  502  to redirect the call to party  505 . MSC  502  acknowledges REDDIR message  514  by returning reddir message  515  to voice mail application  503 . 
     MSC  502  processes the Digits parameter (parameter  252  in FIG.  5 ), and redirects the call accordingly. Subsequently, party  505  releases the call. PSTN  504  notifies MSC  502  about this call event. MSC  502  processes the CallBackFERel parameter (parameter  256  in FIG. 5) as contained in previously received REDDIR message  514 . (Similar call flows can be constructed that are contingent upon the detection of other types of call events such as party  505  is busy, party  505  does not answer, and mobile subscriber unit  500  releasing the call.) This parameter contains the designated telephone number of voice mail application  503 . Thus, the call is redirected back to voice mail application  503  as a result of party  505  releasing the call. The voice dialog between the user of mobile subscriber unit  500  and voice mail application  503  is resumed if another party has left a voice message. The process as described for FIG. 8 is then repeated as many times as needed to span the entirety of voice messages that have been left for the user of mobile subscriber unit  500 . 
     FIG. 9 is a call flow diagram showing a voice mail service that utilizes the single-stage redirection approach for a mobile-terminated call in a wireless communications system. Mobile subscriber unit  600 , base station  601 , MSC  602 , voice mail application  603 , PSTN  604 , and party  605  correspond to mobile subscriber unit  200 , base station  201 , MSC  202 , adjunct processor  203 , PSTN  204 , and party  205 , respectively. Voice mail application  603  initiates the mobile-terminated call to mobile subscriber unit  600  by requesting PSTN  604  to set up the call. (Various events can initiate the mobile-terminated call such as a predetermined time duration expiring since the last access by mobile subscriber unit  600 .) Thus, voice connection  606  from voice mail application  603  to PSTN  604  is established in conjunction with sending a telephone number corresponding to mobile subscriber unit  600  either on voice connection  606  or on a separate signaling facility. PSTN  604  routes the call to MSC  602  in which mobile subscriber unit  600  is located. In other variations, mobile subscriber unit  600  may not be located in MSC  602 , and thus the call is routed to another MSC in which mobile subscriber unit  600  is located. Such variations are well known in the art. 
     MSC  602  initiates base station  601  to page and locate mobile subscriber unit  600  utilizing setup procedure  609 , which is known in the art. Voice connections  608  and  610  are established, completing a voice path between mobile subscriber unit  600  and voice mail application  603 . Voice mail application  603  is notified that mobile subscriber unit  600  has answered the call by answer notification  611  being sent from mobile subscriber unit  600  to base station  601 . Consequently, answer notification  612  is relayed from base station  601  to MSC  602 , and answer notification  613  is sent from MSC  602  to voice mail application  603 . A dialog is established between voice mail application  603  and a user of mobile subscriber unit  600 . Voice mail application  603  determines that the user wishes to call back party  605  that has left a voice message. The remainder of the call flow in FIG. 9 is analogous to the call flow in FIG.  8 . Voice mail application  603  sends REDDIR message  614  to MSC  602  to redirect the call to party  605 . MSC  602  acknowledges REDDIR message  614  by returning reddir message  615  to voice mail application  603 . MSC  602  processes the Digits parameter (parameter  252  in FIG. 5) and redirects the call accordingly. Subsequently, party  605  releases the call. PSTN  604  notifies MSC  602  about this call event. MSC  602  processes CallBackFERel parameter (parameter  258  in FIG. 5) as contained in previously received REDDIR message  614 . The CallBackFERel parameter contains the designated telephone number of voice mail application  603 . Thus, the call is redirected back to voice mail application  603  as a result of party  605  releasing the call. The dialog between the user of mobile subscriber unit  600  and voice mail application  603  is resumed if another party has left a voice message. The process is repeated as many times as needed to span the entirety of voice messages that have been deposited for the user of mobile subscriber unit  600 . 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.