Abstract:
An architecture, client specification and application programming interface (API) for supporting advanced voice services (AVS) for use in handsets in order to support advanced voice services (AVS) for wireless communications systems. The handset or mobile unit executes a client application therein for performing the call setup and in-band signaling with the wireless network for the group voice services, and executes a presence/group management application therein for performing presence and group management functions related to the group voice services in the mobile unit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. Section 119(e) of the following co-pending and commonly-assigned U.S. provisional patent applications: 
     Ser. No. 60/569,953, filed on May 11, 2004, by Ravi Ayyasamy and Krishnakant Patel, entitled PRESS TO TALK CLIENT APPLICATION PROGRAMMING INTERFACE (PCAPI); and 
     Ser. No. 60/579,309, filed Jun. 14, 2004, by Ravi Ayyasamy, Krishnakant Patel, and Gorachand Kundu, entitled CLIENT SPECIFICATION AND ARCHITECTURE FOR SUPPORTING PRESS TO TALK AND OTHER PREMIUM VOICE SERVICES IN WIRELESS NETWORKS; 
     both of which applications are incorporated by reference herein. 
     This application is a continuation-in-part and claims the benefit under 35 U.S.C. Sections 119, 120 and/or 371 of the following co-pending and commonly-assigned patent applications: 
     Ser. No. 10/515,556, filed on Nov. 23, 2004, by Gorachand Kundu, Ravi Ayyasamy, and Krishnakant Patel, entitled DISPATCH SERVICE ARCHITECTURE FRAMEWORK, which application claims the benefit under 35 U.S.C. Section 371 of the following co-pending and commonly-assigned PCT international patent application:
         Serial No. PCT/US03/16386, filed on May 23, 2003, by Gorachand Kundu, Ravi Ayyasamy, and Krishnakant Patel, entitled DISPATCH SERVICE ARCHITECTURE FRAMEWORK, which application claims the benefit under 35 U.S.C. Section 119(e) of the following co-pending and commonly-assigned U.S. provisional patent applications:
           Ser. No. 60/382,981, filed on May 24, 2002, by Gorachand Kundu, Ravi Ayyasamy, and Krishnakant Patel, entitled RADIO GATEWAY ARCHITECTURE FRAMEWORK;   Ser. No. 60/383,179, filed May 24, 2002, by Gorachand Kundu, Ravi Ayyasamy, and Krishnakant Patel, entitled DISPATCH SERVICE ARCHITECTURE FRAMEWORK; and   Ser. No. 60/407,168, filed Aug. 30, 2002, by Gorachand Kundu, Ravi Ayyasamy, and Krishnakant Patel, entitled DISPATCH SERVICE ARCHITECTURE FRAMEWORK; and   
               

     Serial No. PCT/US04/23038, filed on Jul. 16, 2004, by F. Craig Farrill, Bruce D. Lawler, and Krishnakant M. Patel, entitled PREMIUM VOICE SERVICES FOR WIRELESS COMMUNICATIONS SYSTEMS, which application claims the benefit under 35 U.S.C. Section 119(e) of the following co-pending and commonly-assigned U.S. provisional patent applications:
         Ser. No. 60/488,638, filed on Jul. 18, 2003, by F. Craig Farrill, Bruce D. Lawler and Krishnakant Patel, entitled REAL-TIME EXCHANGE;   Ser. No. 60/492,650, filed Aug. 5, 2003, by Bruce D. Lawler, Krishnakant Patel, and F. Craig Farrill, entitled CDMA PRESS-TO-TALK (P2T) PROOF-OF-CONCEPT DEMONSTRATION; and   Ser. No. 60/576,094, filed Jun. 2, 2004, by Craig Farrill, Bruce Lawler, and Krishnakant Patel, entitled TECHNIQUE FOR ZERO DELAY CALL SET-UP IN P2T SYSTEMS;       

     all of which applications are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates in general to wireless communications systems, and more specifically, to an architecture, client specification and application programming interface (API) for supporting advanced voice services (AVS) including push-to-talk or press-to-talk on wireless handsets and networks. 
     2. Description of Related Art 
     Group-based voice services, such as two-way half-duplex voice calls within a group or between individuals, also known as “Push-to-Talk,” “Press-to-Talk,” PTT or P2T, have enormous revenue earnings potential for wireless networks, such as cellular networks and personal communications systems (PCS) networks. Corporate subscribers primarily use such services for coordinating field people or fleet users from a central location. 
     Currently, there are three major approaches employed in providing group-based voice services such as P2T in wireless networks. One approach requires the installation of a dedicated private network, parallel to the wireless network, to support the group-based voice services. NEXTEL uses such a system, based on a solution developed by MOTOROLA known as IDEN. However, a dedicated private network is costly to install and maintain and is employed by a few public wireless carriers. Also, the IDEN system is non-standard, and hence cannot be used in standard wireless communications networks, such as those based on CDMA and GSM. 
     Another approach is based on Voice over IP (VoIP) technologies. While this approach promises compliance with newer and emerging standards, such as GPRS (General Packet Radio Service), UMTS (Universal Mobile Telecommunications System), etc., it does not provide a solution for carriers employing wireless networks based on existing standards, such as GSM (Global System for Mobile Communications), CDMA (Code Division Multiple Access), etc. However, even for the newer standards, solutions based on VoIP have serious drawbacks, including slower call setup, significant overhead, increased susceptibility to packet losses, low bit rate voice coders (vocoders), and significant modifications to the mobile handset. There is a need, instead, for solutions that require only minimal upgrades to the handset. 
     Still another approach is that defined in the co-pending and commonly-assigned patent applications cross-referenced above and incorporated by reference herein. In this approach, group-based voice services are provided by a real-time exchange or dispatch gateway that interfaces to the wireless network to provide the group-based voice services therein, wherein both the real-time exchange and mobile handsets that use the group-based voice services communicate with each other using call setup and in-band signaling within the wireless network. 
     Notwithstanding these innovations, there is a need in the art for an architecture, client specification and application programming interface (API) for use in handsets in order to support advanced voice services (AVS) for wireless communications systems. The present invention aims to satisfy this need. 
     SUMMARY OF THE INVENTION 
     To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses an architecture, client specification and application programming interface (API) for use in handsets in order to support advanced voice services (AVS) for wireless communications systems. The handset or mobile unit executes a client application therein for performing the call setup and in-band signaling with the wireless network for the group voice services, and executes a presence/group management application therein for performing presence and group management functions related to the group voice services in the mobile unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
         FIG. 1  is a block diagram that illustrates an exemplary embodiment of a wireless communications network according to a preferred embodiment of the present invention; 
         FIG. 2  illustrates a proposed architecture for a real-time exchange according to the preferred embodiment of the present invention; 
         FIG. 3  is a state diagram that illustrates the operation of a push-to-talk call according to a preferred embodiment of the present invention; 
         FIG. 4  illustrates the high-level functional components and their interfaces inside a mobile handset according to a preferred embodiment of the present invention; 
         FIG. 5  illustrates the high-level functional components of the push-to-talk client application and presence/group management application according to a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration the specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized as structural changes may be made without departing from the scope of the present invention. 
     Overview 
     The present invention provides an architecture, client specification and application programming interface (API) for supporting advanced voice services (AVS) on handsets used in wireless communications networks. 
     Network Architecture 
       FIG. 1  is a block diagram that illustrates an exemplary embodiment of a wireless communications network according to a preferred embodiment of the present invention. 
     Within the network  100 , an RTX (Real-Time Exchange)  102 , previously known as a Dispatch Gateway (DG), communicates with a MSC (Mobile Switching Center)  104  and PSTN (Public Switched Telephone Network)  106  using SS7—ISUP/WIN/CAMEL (Signaling System 7—Integrated Services Digital Network User Part/Wireless Intelligent Network/Customized Applications for Mobile Enhanced Logic) messages at a signaling plane  108 . A bearer path  110  implements a TDM (Time Division Multiplexing) interface carrying PCM (Pulse Code Modulation) or TFO (Tandem Free Operation) voice frames. Support for TFO in this path  110  is negotiated between a BSC (Base Station Controller)  112  and the RTX  102  for each originating and terminating leg of a group call. The use of TFO ensures high voice quality (as voice vocoder conversion is avoided) between mobile-to-mobile calls. 
     When a subscriber originates a group call, the MSC  104  routes the call to the RTX  102 . The MSC  104  also requests the BSC  112  via  116  to establish a radio traffic path  118  with a mobile unit or handset  120  via the BTS (Base Transceiver Station)  122  (as it does for a normal cellular call). At this time, the BSC  112  tries to negotiate TFO (if it is supported) on a TDM link with the far end (in this case, the RTX  102 ). 
     At the same time (after the MSC  104  terminates the group call request to the RTX  102 ), the RTX  102  identifies the terminating group users and their MS-ISDN (Mobile Station—Integrated Services Digital Network) numbers. It sends an ISUP call origination request for each terminating handset  120 . It may send requests directly to the MSC  104 , PSTN  106  or IP network  124  via a PDSN (Public Data Switched Network)  126 , Router  128 , and/or Internet/Intranet  130 , depending on the routing table configuration for terminating MS-ISDN numbers. Once the bearer path  110  is established, the RTX  102  begins a negotiation with the far end (in this case, the terminating BSC  112 ) for each terminating leg to a handset  120 . 
     Once bearer paths  110  are established for originating and terminating legs for a group call, the RTX  102  switches (or duplicates) voice frames from the originating handset  120  to all terminating mobile handsets  120 . 
     The RTX  102  may use an IP network  124  or the Internet/Intranet  130  for two different purposes. The IP network  124  or the Internet/Intranet  130  can be used in a toll bypass mode where two RTXs  102  can exchange voice traffic bypassing the PSTN  106 . However, each RTX  102  is responsible for terminating traffic to its closest MSC  104 . In this case, the IP network  124  or the Internet/Intranet  130  is used as a backbone transport of voice traffic between two RTXs  102 . 
     The IP network  124  or the Internet/Intranet  130  can also be used for a registration and presence application. Since the MSC  104  will not direct a registration request from a handset  120  to the RTX  102  (because it would require changes in the MSC  104 ), the latter does not have any information of the registered mobile handsets  120 . To circumvent this issue, a registration and presence application runs over an IP stack in the handset  120 . After the handset  120  registers for a data interface (i.e., obtaining an IP address) with the PDSN  126  (or Serving GSM Service Nodes (SGSN) in the case of GSM networks), the registration and presence application in the handset  120  registers with the RTX  102  using its IP address. The RTX  102  also uses this IP interface to update the presence information of other group members to a handset  120 . 
     An alternative embodiment would use the SMS (Short Message Service) transport to carry presence messages over a data channel. The RTX  102  interacts with the mobile handset  120  using predefined presence application related messages that are transported as SMS messages. The same messages can be transported via the PDSN  126  interface, if group users have data service. 
     Real Time Exchange 
       FIG. 2  illustrates a proposed architecture for the RTX  102  according to the preferred embodiment of the present invention. 
     The architecture includes a Call Processing system  200 , Presence Server  202 , Real-Time Event Processing system  204 , one or more Media Managers  206 , and an SMPP (Short Message Peer-to-Peer) Transport  208 , as well as modules for various SS7 protocols, such as MTP-1 (Message Transfer Part Level 1)  210 , MTP-2 (Message Transfer Part Level 2)  212 , MTP-3 (Message Transfer Part Level 3)  214 , ISUP (Integrated Services Digital Network User Part)  216 , SCCP (Signaling Connection Control Part)  218 , and TCAP (Transactions Capabilities Application Part)  220  protocols. 
     The Call Processing system  200 , Presence Server  202 , Media Managers  204 , SMPP Transport  206 , and other modules communicate across an IP network  222 . The Real-Time Event Processing system  204  communicates directly with the Call Processing system  200 , Presence Server  202 , and the modules for various SS7 protocols. The modules for various SS7 protocols communicate with other entities via a SS7 Signaling Link  224 . The SMPP Transport  206  communicates with a SMSC (Short Message Service Center) gateway using the SMPP protocol  226 . The Media Managers  204  communicate among themselves using the H.110 protocol  228  (or some other protocol, such TCP/IP). 
     The operation of these various components are described in the co-pending and commonly-assigned patent applications cross-referenced above and incorporated by reference herein. 
     P2T State Diagram 
       FIG. 3  is a state diagram that illustrates the operation of a P2T call according to a preferred embodiment of the present invention. 
     State  300  represents a mobile handset  120  in a NULL state, i.e., the start of the logic. A user pressing a P2T button or making a request to terminate a group call triggers a transition out of this state. 
     State  302  represents a mobile handset  120  in an active group call state. In this state, the user receives a chirp tone to start talking. The user responds by pressing the P2T button on the mobile handset  120  and talking. A talking user must hold the P2T button. The mobile handset  120  ensures that only when the user presses the P2T button is the reverse traffic channel is used to send voice frames, and the RTX  102  switches voice frames only in one direction, i.e., from talker to listener, which ensures the half-duplex operation required for a P2T call. 
     State  304  represents the group “floor” being available to all members of the group. When the talking user releases the P2T button, the floor is available to all group members. All members of the group receive a “free floor” tone on their mobile handset  120 . A user who requests the floor by pressing the P2T button first (in the “free-floor” state) is assigned the floor, wherein the network  100  sends a chirp tone to the successful user. 
     State  306  represents a mobile handset  120  being in an active group call state. In this state, the user is listening to the group call. If a non-talking user presses the P2T button in a call active state, the user does not receive any response from the network  100  and remains in the same functional state. 
     State  308  represents a user receiving an “unsuccessful bidding” tone on his mobile handset  120 , after the user pressed the P2T button, but was not granted the floor of the group call. The user subsequently starts listening to the voice message of the talking user. 
     Non-talking users (including the talking user who must release the P2T button to end the call thus becoming non-talking and making the floor available for others) can request the network  100  to end their respective call legs explicitly. 
     State  310  represents a terminating leg being released from the group call after the user ends the call. 
     State  312  also represents a terminating leg being released from the group call after the user ends the call. 
     State  314  represents all terminating legs being released from the group call when no member of the group bids for the floor within a specified time period. 
     Mobile Handset Components 
       FIG. 4  illustrates the high-level functional components and their interfaces inside the mobile handset  120  according to a preferred embodiment of the present invention. The high-level functional components and their interfaces include a physical layer  400 , layer  2   402 , signaling layer  3   406 , cellular voice application  408 , P2T client application  410 , SMS (or USSD (Unstructured Supplementary Services Data) or GPRS (General Packet Radio Service)) application  412  and presence/group management application  414 . 
     Note that P2T client application  410  and presence/group management application  414  are incorporated without requiring any changes in signaling layer  3   406  and below. All the existing messages that the cellular voice application  408  and SMS application  412  use remain as is and no additional messages are required to be implemented. 
     The P2T client application  410  performs all the call signaling states described in  FIG. 3 , which are the same that are traversed through by the cellular voice application  408 . However, in some cases, the actions or behaviors in a particular state may vary. 
     As an example, for terminating a P2T call, the P2T client application  410  in an “alerting” state does not play an alerting tone to the user and wait for user action. Instead, it plays a small duration “alert” tone, sends a “connect” message immediately to the network  100  and joins the vocoder output to a speaker on the handset  120 . (Alternatively, the handset  120  could answer the call, and the RTX  102  plays the tone.) 
     Similarly, the presence/group management application  414  messages are tunneled via SMS (or USSD or GPRS) messages and delivered to the SMS application  412  by Layer  3  signaling  406 , and vice versa. These messages are identified and handed over to the presence/group management application  414  for decoding. In one embodiment, the Wireless Village protocol messages are used between the handset  120  and the RTX  102  for presence and group management operations, although other messages could be used as well. 
     P2T Client Application and Presence/Group Management Application 
       FIG. 5  illustrates the high-level functional components of the P2T client application  410  and the presence/group management application  414  according to a preferred embodiment of the present invention. 
     In this embodiment, the P2T client application  410  includes a message transport layer  500 , encoder  502 , decoder  504  and database  506 . In addition, the P2T client application  410  provides an application programming interface (API) for use by other components of the handset  120 . 
     Other components in the handset  120  that use the API of the P2T client application  410  include the presence/group management application  414 , a user interface  508 , call manager  510  and non-volatile (NV) memory  512 . 
     The transport layer  500  delivers encoded messages from the handset  120  to a destination presence server  202  in the RTX  102 . The media used to transport these messages could be SMS, USSD or GPRS. The transport layer  500  can be configured for any of these media based on the configuration parameters. 
     The transport layer  500  implements a queue to transport the messages from the handset  120 . The transport layer  500  also notifies the upper layer modules, such as the presence/group management application  414 , about the failure or success of the message transport. In case of any failures in sending the messages, the transport layer  500  handles the re-transmission of the messages. The retransmission parameters are configurable and can be modified at run time without affecting the other module functionalities. 
     As noted above, the presence server  202  and handset  120  communicate using Wireless Village messages. The encoder  502  encodes the Wireless Village messages, and handles message fragmentation, if necessary. 
     The decoder  504  decodes incoming Wireless Village messages from the RTX  102  and populates specific data structures in the handset  120 . The decoder  504  checks the validity of the incoming messages by verifying mandatory parameters for each of the incoming messages. A message will not be processed further if the decoder  504  fails to decode the message. 
     The presence/group management application  414  does the most of the processing of the Wireless Village messages. The decoded message from decoder  504  is sent to the presence/group management application  414  to take the appropriate action. In this regard, the presence/group management application  414  may interact with the encoder  502 , database  506 , transport layer  500  or user interface  508 . 
     The presence/group management application  414  enables P2T subscribers to track the presence of fellow members of the group in the network  100  on their mobile handsets  120 . It also provides a mechanism and API to carry-out group management operations on the handset  120 , such as add member, delete member, etc. The communication interface between presence/group management application  414  and the presence server  202  in the RTX  102  may rely on either SMS (or USSD or GPRS) messages for transport. 
     Since most of the presence information is stored in the database  506 , the database  506  is tightly integrated with the presence/group management application  414 . The database  506  stores groups, contacts, presence and availability related information in the NV memory  512 . The database  506  information essentially contains group and member information along with presence information associated with each group and member. Apart from group and member information, the database  506  also stores subscriber information, such as privileges, presence information, etc. The other components of the handset  120  may interact with the database  506  to retrieve/update the group, members and presence information for various operations. The database  506  also has pointers to the native address book on the handset  120 , which is stored in the NV memory  512 , to provide seamless “alias” naming for contacts between cellular calls and P2T calls. 
     The user interface  508  provides a mechanism for the user to view and manage groups, group members, contacts, presence and availability. The user interface  598  also makes it possible to make P2T calls from the group/contact list screens. 
     The call manager  510  handles all the telephony related functionalities, such as P2T Group/Private/Dynamic Group calls. The call manager  510  implementation is device-specific and vendor-specific, and it interacts with the user interface  508  and database  506 . The required information for call-related functionalities is obtained from the wrappers provided by the database  506 . 
     The NV memory  512  is also used to store the configuration parameters, which can be updated by the RTX as required. 
     User Interactions with the Mobile Handset 
     This section describes various scenarios that a group user may explicitly invoke through the mobile handset  120 . 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 User Interactions with the Mobile Handset 
               
             
          
           
               
                   
                   
                 Action by the P2T client 
                   
               
               
                   
                   
                 application 410 and 
               
               
                   
                   
                 presence/group 
               
               
                   
                   
                 management application 
               
               
                 No. 
                 User action 
                 414 in the handset 120 
                 Remarks 
               
               
                   
               
             
          
           
               
                 1. 
                 The user powers on the 
                 The presence/group 
                 Each handset 120 is 
               
               
                   
                 handset 120. 
                 management application 
                 configured with the 
               
               
                   
                   
                 414 is notified when the 
                 address of the home RTX 
               
               
                   
                   
                 handset 120 is turned on. 
                 102 when it is 
               
               
                   
                   
                 The presence/group 
                 provisioned for group 
               
               
                   
                   
                 management application 
                 service. 
               
               
                   
                   
                 414 sends a “presence 
               
               
                   
                   
                 registration” message to 
               
               
                   
                   
                 the home RTX 102. The 
               
               
                   
                   
                 presence/group 
               
               
                   
                   
                 management application 
               
               
                   
                   
                 414 interacts with the 
               
               
                   
                   
                 SMS application 412 to 
               
               
                   
                   
                 transport this message to 
               
               
                   
                   
                 the SMSC gateway and 
               
               
                   
                   
                 the SMSC gateway routes 
               
               
                   
                   
                 the message to the home 
               
               
                   
                   
                 RTX 102 via the IP 
               
               
                   
                   
                 network 124 (as e-mail). 
               
               
                 2. 
                 The user powers off the 
                 The presence/group 
               
               
                   
                 handset 120. 
                 management application 
               
               
                   
                   
                 414 is notified when the 
               
               
                   
                   
                 handset 120 is turned off. 
               
               
                   
                   
                 The presence/group 
               
               
                   
                   
                 management application 
               
               
                   
                   
                 414 sends a predefined 
               
               
                   
                   
                 “presence registration” 
               
               
                   
                   
                 message to the home 
               
               
                   
                   
                 RTX 102. The 
               
               
                   
                   
                 presence/group 
               
               
                   
                   
                 management application 
               
               
                   
                   
                 414 interacts with the 
               
               
                   
                   
                 SMS application 412 to 
               
               
                   
                   
                 transport this message to 
               
               
                   
                   
                 the SMSC gateway and 
               
               
                   
                   
                 the SMSC gateway routes 
               
               
                   
                   
                 this message to the home 
               
               
                   
                   
                 RTX 102 via the IP 
               
               
                   
                   
                 network 124 (as e-mail). 
               
               
                 3. 
                 The user presses the P2T 
                 The P2T client 
                 The MSC 104, based on 
               
               
                   
                 button on the handset 120 
                 application 410 is 
                 the DP trigger, sends a 
               
               
                   
                 to contact the default 
                 invoked. It sends a call 
                 query to the RTX 102 
               
               
                   
                 group. 
                 origination message with 
                 with the called party&#39;s 
               
               
                   
                   
                 the called party&#39;s address 
                 address. The RTX 102 
               
               
                   
                   
                 parameter filled with a 
                 responds with its routing 
               
               
                   
                   
                 DP trigger code, a code to 
                 number and sets up the 
               
               
                   
                   
                 identify a private/group 
                 terminating legs for the 
               
               
                   
                   
                 call and the default group 
                 group. The call setup is 
               
               
                   
                   
                 id. A bearer path is set up 
                 performed in parallel in 
               
               
                   
                   
                 and the vocoder 
                 order to improve call 
               
               
                   
                   
                 input/output is connected 
                 setup time. 
               
               
                   
                   
                 to the microphone and 
               
               
                   
                   
                 speaker of the handset 
               
               
                   
                   
                 120, respectively. 
               
               
                 4. 
                 The user selects a 
                 The P2T client 
               
               
                   
                 particular group from a 
                 application 410 is 
               
               
                   
                 list of groups displayed 
                 invoked. It sends a call 
               
               
                   
                 on the handset 120 and 
                 origination message with 
               
               
                   
                 presses the P2T button. 
                 the called party&#39;s address 
               
               
                   
                   
                 parameter filled with a 
               
               
                   
                   
                 DP trigger code, a code to 
               
               
                   
                   
                 identify the private/group 
               
               
                   
                   
                 call, and the selected MS- 
               
               
                   
                   
                 ISDN/group id. A bearer 
               
               
                   
                   
                 path is set up and the 
               
               
                   
                   
                 vocoder input/output is 
               
               
                   
                   
                 connected to the 
               
               
                   
                   
                 microphone and speaker 
               
               
                   
                   
                 of the handset 120, 
               
               
                   
                   
                 respectively. 
               
               
                 5. 
                 The user wants to make a 
                 The P2T client 
                 The RTX 102 should be 
               
               
                   
                 private call and presses 
                 application 410 is 
                 able to isolate the MS- 
               
               
                   
                 the P2T button. (A private 
                 invoked. (A private call is 
                 ISDN number and group 
               
               
                   
                 call involves only two 
                 considered a group call 
                 id based on the code. 
               
               
                   
                 parties. The called party 
                 where only two parties 
               
               
                   
                 in a private call may be a 
                 are involved). It sends a 
               
               
                   
                 member of his/her 
                 call origination message 
               
               
                   
                 subscribed group or 
                 with the called party&#39;s 
               
               
                   
                 he/she can enter called 
                 address parameter filled 
               
               
                   
                 party&#39;s MS-ISDN number 
                 with a DP Trigger code, a 
               
               
                   
                 explicitly). 
                 code to identify a 
               
               
                   
                   
                 private/group call and the 
               
               
                   
                   
                 selected MS-ISDN 
               
               
                   
                   
                 number. A bearer path is 
               
               
                   
                   
                 set up and the vocoder 
               
               
                   
                   
                 input/output is to the 
               
               
                   
                   
                 microphone and speaker 
               
               
                   
                   
                 of the handset 120, 
               
               
                   
                   
                 respectively. 
               
               
                 6. 
                 The user selects a 
                 The P2T client 
               
               
                   
                 particular group from the 
                 application 410 is 
               
               
                   
                 list of groups displayed 
                 invoked. It sends a call 
               
               
                   
                 on the handset, marks a 
                 origination message with 
               
               
                   
                 set of members and then 
                 the called party&#39;s address 
               
               
                   
                 presses the P2T button. 
                 parameter filled with a 
               
               
                   
                   
                 DP Trigger code, a 
               
               
                   
                   
                 selected group id and the 
               
               
                   
                   
                 positions of the marked 
               
               
                   
                   
                 members within the 
               
               
                   
                   
                 group. A bearer path is set 
               
               
                   
                   
                 up and the vocoder 
               
               
                   
                   
                 input/output is connected 
               
               
                   
                   
                 to the microphone and 
               
               
                   
                   
                 speaker of the handset 
               
               
                   
                   
                 120, respectively. 
               
               
                 7. 
                 While in a group call 
                 The P2T client 
               
               
                   
                 active state, the user 
                 application 410 sends a 
               
               
                   
                 releases the P2T button to 
                 “#” as an in-band DTMF 
               
               
                   
                 free the floor. 
                 signal to the BSC 112. 
               
               
                   
                   
                 The BSC 112 injects this 
               
               
                   
                   
                 DTMF signal into the 
               
               
                   
                   
                 PCM stream. 
               
               
                 8. 
                 While in a group call 
                 The P2T client 
               
               
                   
                 active state, the user 
                 application 410 sends a 
               
               
                   
                 presses the P2T button to 
                 “*” as an out of band 
               
               
                   
                 get the floor. 
                 DTMF signal to the BSC 
               
               
                   
                   
                 112. The BSC 112 injects 
               
               
                   
                   
                 this DTMF signal into the 
               
               
                   
                   
                 PCM stream. 
               
               
                 9. 
                 While in a group call 
                 The P2T client 
               
               
                   
                 active state, the user 
                 application 410 sends a 
               
               
                   
                 presses the “End” button 
                 call release message to 
               
               
                   
                 explicitly to release the 
                 the MSC 104. The MSC 
               
               
                   
                 group call. 
                 104 requests the handset 
               
               
                   
                   
                 120 to clear its call states 
               
               
                   
                   
                 and sends a release 
               
               
                   
                   
                 message to the RTX 102. 
               
               
                   
                   
                 The RTX 102 releases 
               
               
                   
                   
                 that user&#39;s leg from the 
               
               
                   
                   
                 group call. 
               
               
                   
               
             
          
         
       
     
     Note that the P2T client application  410  and presence/group management application  414  also may manage a P2C (Press-To-Conference) session in a manner similar to a P2T session. More information on P2C sessions can be found in the co-pending and common-assigned patent application Serial Number PCT/US04/23038, filed on Jul. 16, 2004, by F. Craig Farrill, Bruce D. Lawler, and Krishnakant M. Patel, entitled PREMIUM VOICE SERVICES FOR WIRELESS COMMUNICATIONS SYSTEMS, which application is incorporated by reference herein. 
     Network Interactions with the Mobile Handset 
     This section outlines scenarios that occur when the P2T client application  410  and presence/group management application  414  in the mobile handset  120  interact with the network  100 . Note that user is not aware of these scenarios as the P2T client application  410  and presence/group management application  414  in the mobile handset  120  handle these network-generated events in the background. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Network Interactions with the Mobile Handset 
               
             
          
           
               
                   
                   
                 Action by P2T client 
                   
               
               
                   
                   
                 application 410 and 
               
               
                   
                   
                 presence/group 
               
               
                   
                   
                 management application 
               
               
                   
                 Causing Event/Scenario 
                 414 in the Mobile 
               
               
                 No. 
                 in Mobile 
                 Handset 120 
                 Remarks 
               
               
                   
               
             
          
           
               
                 1. 
                 A cellular call terminates 
                 The P2T client 
                 The indicator for group 
               
               
                   
                 to the handset 120 which 
                 application 410 is 
                 call in the calling party&#39;s 
               
               
                   
                 the calling party starts 
                 invoked. It does not play 
                 address should be unique 
               
               
                   
                 with a “*” (in an alerting 
                 an alerting tone to the 
                 enough so that it is never 
               
               
                   
                 state). The call 
                 user as specified in the 
                 used in a cellular call. 
               
               
                   
                 termination identifier can 
                 “Alert With Info” 
               
               
                   
                 be either a prefix or a 
                 message. Instead, it plays 
               
               
                   
                 suffix. 
                 a small duration (e.g., 200 ms) 
               
               
                   
                   
                 special group call 
               
               
                   
                   
                 terminating alerting tone, 
               
               
                   
                   
                 immediately sends a 
               
               
                   
                   
                 connect message to the 
               
               
                   
                   
                 network 100, and 
               
               
                   
                   
                 connects the vocoder 
               
               
                   
                   
                 output to the speaker of 
               
               
                   
                   
                 the handset 120. 
               
               
                 2. 
                 While in a group call 
                 The P2T client 
               
               
                   
                 active state, a release 
                 application 410 releases 
               
               
                   
                 event is received from the 
                 allocated resources in the 
               
               
                   
                 network 100. 
                 handset 120 and sends a 
               
               
                   
                   
                 “release complete” 
               
               
                   
                   
                 message to the network 
               
               
                   
                   
                 100. There are two 
               
               
                   
                   
                 possible scenarios: (1) the 
               
               
                   
                   
                 originator disconnects and 
               
               
                   
                   
                 the call goes on, or (2) the 
               
               
                   
                   
                 originator disconnects and 
               
               
                   
                   
                 the entire call is ended. 
               
               
                 3. 
                 A Presence Update 
                 The presence/group 
               
               
                   
                 Notification message is 
                 management application 
               
               
                   
                 delivered through the 
                 414 is invoked to decode 
               
               
                   
                 SMS interface. 
                 the message. It 
               
               
                   
                   
                 adds/deletes/modifies the 
               
               
                   
                   
                 member&#39;s information 
               
               
                   
                   
                 with the presence 
               
               
                   
                   
                 information in the specific 
               
               
                   
                   
                 group indicated in the 
               
               
                   
                   
                 message. There is a 
               
               
                   
                   
                 special WV delimiter that 
               
               
                   
                   
                 differentiates this from 
               
               
                   
                   
                 regular SMS/data. 
               
               
                 4. 
                 An Auto Configuration 
                 The presence/group 
               
               
                   
                 Update message is 
                 management application 
               
               
                   
                 delivered through the 
                 414 is invoked to decode 
               
               
                   
                 SMS application 412. 
                 the message. 
               
               
                   
                 This message is received 
                 Configuration parameters 
               
               
                   
                 only once when a user is 
                 for the P2T client 
               
               
                   
                 provisioned for group 
                 application 410 and 
               
               
                   
                 voice service. 
                 presence/group 
               
               
                   
                   
                 management application 
               
               
                   
                   
                 414 are set. 
               
               
                   
               
             
          
         
       
     
     Service Interactions with the P2T Client Application 
     A handset  120  can support either cellular or group voice service at any instant of time. This section highlights various scenarios when the two services may conflict with each other. In some of these cases, the user&#39;s intervention is needed to select one of the services, whereas other cases are decided by the P2T client application  412  itself as part of the call processing logic. This section also discusses the impact of other cellular services, such as call hold, call forwarding, call forwarding busy, call waiting, call forwarding no answer, etc., on group voice services. 
     The following table has been prepared with the assumption that, while using group voice services, a user cannot put other parties on hold, even though they can switch to another call without disconnecting the group call leg. However, a user can leave a group call session at any time by selecting an “end” soft key. The objective is to allow group members to continue with the call, while one or more legs can either be released from the RTX  102  or disjoined at the MSC  104  (at the time of service switching) during a session. The network  100  releases a group call only when the floor remains free for some predefined time. If a talking user leaves the session, the network  100  will make the floor available to all others. 
     It is also assumed that a member of a group has call waiting, calling number presentation at call waiting, call forwarding busy (to voicemail) and calling line identity presentation features enabled on the handset  120 . 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Service Interactions for the P2T client application 
               
             
          
           
               
                   
                   
                   
                 Action by the 
                   
               
               
                   
                   
                   
                 P2T client 
               
               
                   
                   
                   
                 application 410 
               
               
                   
                   
                   
                 and 
               
               
                   
                   
                   
                 presence/group 
               
               
                   
                   
                   
                 management 
               
               
                   
                   
                   
                 application 414 in 
               
               
                   
                 Present State (in 
                   
                 the Mobile 
               
               
                 No. 
                 Mobile) 
                 Triggering Event 
                 Handset 120 
                 Remarks 
               
               
                   
               
             
          
           
               
                 1. 
                 A group voice call 
                 Another group or 
                 (1) In this case, the 
                 For (1), the user 
               
               
                   
                 is in an active state 
                 cellular call is 
                 P2T client 
                 remains as a non- 
               
               
                   
                 and the user is 
                 being terminated 
                 application 410 
                 talking leg to the 
               
               
                   
                 talking with the 
                 by the MSC 104 
                 sends a DTMF 
                 RTX 102, even 
               
               
                   
                 P2T button 
                 and a call-waiting 
                 signal to free the 
                 though the circuit 
               
               
                   
                 pressed. 
                 tone is played. The 
                 floor. Next, the 
                 is broken at the 
               
               
                   
                   
                 user is prompted to 
                 P2T client 
                 MSC 104. The 
               
               
                   
                   
                 accept the second 
                 application 410 
                 RTX 102 may 
               
               
                   
                   
                 call. The following 
                 sends a “Flash 
                 release all legs of 
               
               
                   
                   
                 scenarios can 
                 with Info” 
                 the call at any 
               
               
                   
                   
                 occur: (1) the user 
                 message to accept 
                 time. 
               
               
                   
                   
                 releases the P2T 
                 the second call, 
               
               
                   
                   
                 button and accepts 
                 while the first call 
               
               
                   
                   
                 the second call; (2) 
                 is broken at the 
               
               
                   
                   
                 the user releases 
                 MSC 104. After 
               
               
                   
                   
                 the P2T button, 
                 attending to the 
               
               
                   
                   
                 ends the active call 
                 second call, the 
               
               
                   
                   
                 and accepts the 
                 user may toggle to 
               
               
                   
                   
                 second call; (3) the 
                 the first call. (2) In 
               
               
                   
                   
                 user does not 
                 this case, the P2T 
               
               
                   
                   
                 accept the waiting 
                 client application 
               
               
                   
                   
                 second call and 
                 410 sends a DTMF 
               
               
                   
                   
                 continues with the 
                 signal to free the 
               
               
                   
                   
                 first call. 
                 floor. Next, it 
               
               
                   
                   
                   
                 releases the active 
               
               
                   
                   
                   
                 call and the second 
               
               
                   
                   
                   
                 call is established. 
               
               
                   
                   
                   
                 (3) The MSC 104 
               
               
                   
                   
                   
                 handles the second 
               
               
                   
                   
                   
                 call using a “call 
               
               
                   
                   
                   
                 forwarding no 
               
               
                   
                   
                   
                 answer” feature 
               
               
                   
                   
                   
                 provisioned for the 
               
               
                   
                   
                   
                 user. 
               
               
                 2. 
                 A group voice call 
                 Another group or 
                 (1) In this case, the 
               
               
                   
                 is in an active state 
                 cellular call is 
                 P2T client 
               
               
                   
                 and the user is not 
                 being terminated 
                 application 410 
               
               
                   
                 talking (i.e., does 
                 by the MSC 104 
                 sends a “Flash 
               
               
                   
                 not press the P2T 
                 and the call- 
                 with Info” 
               
               
                   
                 button). 
                 waiting tone is 
                 message to accept 
               
               
                   
                   
                 played. The user is 
                 the second call, 
               
               
                   
                   
                 prompted to accept 
                 while the first call 
               
               
                   
                   
                 the second call. 
                 is broken at the 
               
               
                   
                   
                 The following 
                 MSC 104. After 
               
               
                   
                   
                 scenarios can 
                 attending to the 
               
               
                   
                   
                 occur: (1) the user 
                 second call, the 
               
               
                   
                   
                 accepts the second 
                 user may toggle to 
               
               
                   
                   
                 call, (2) the user 
                 the first call. (2) In 
               
               
                   
                   
                 ends the active call 
                 this case, the P2T 
               
               
                   
                   
                 and accepts the 
                 client application 
               
               
                   
                   
                 second call, or (3) 
                 410 releases the 
               
               
                   
                   
                 the user does not 
                 active call and the 
               
               
                   
                   
                 accept the waiting 
                 second call is 
               
               
                   
                   
                 call and continues 
                 established. (3) In 
               
               
                   
                   
                 with the first call. 
                 this case, the MSC 
               
               
                   
                   
                   
                 104 handles the 
               
               
                   
                   
                   
                 second call using 
               
               
                   
                   
                   
                 the “call 
               
               
                   
                   
                   
                 forwarding no 
               
               
                   
                   
                   
                 answer” feature 
               
               
                   
                   
                   
                 provisioned for the 
               
               
                   
                   
                   
                 user. 
               
               
                 3. 
                 A cellular voice 
                 Another group call 
                 Similar to the 
               
               
                   
                 call is in an active 
                 is terminated by 
                 previous case. 
               
               
                   
                 state 
                 the MSC 104 and 
               
               
                   
                   
                 the “call-waiting” 
               
               
                   
                   
                 tone is played. The 
               
               
                   
                   
                 user&#39;s action is 
               
               
                   
                   
                 similar to the 
               
               
                   
                   
                 previous case. 
               
               
                 4. 
                 A group call is in 
                 The user wants to 
                 (1) In this case, the 
                 The first case may 
               
               
                   
                 an active state and 
                 originate another 
                 P2T client 
                 lead to a 3-party 
               
               
                   
                 the user is talking 
                 cellular call. The 
                 application 410 
                 call, which should 
               
               
                   
                 with the P2T 
                 following 
                 sends a DTMF 
                 be avoided from a 
               
               
                   
                 button pressed. 
                 scenarios may 
                 signal to free the 
                 group call 
               
               
                   
                   
                 occur: (1) The user 
                 floor. Next, the 
                 perspective. 
               
               
                   
                   
                 releases the P2T 
                 P2T client 
               
               
                   
                   
                 button and 
                 application 410 
               
               
                   
                   
                 originates the 
                 sends a “Flash 
               
               
                   
                   
                 second call, or (2) 
                 with Info” 
               
               
                   
                   
                 the user releases 
                 message to 
               
               
                   
                   
                 the P2T button, 
                 originate the 
               
               
                   
                   
                 ends the first 
                 second cellular 
               
               
                   
                   
                 active call, and 
                 call, while the first 
               
               
                   
                   
                 originates the 
                 call is broken at 
               
               
                   
                   
                 second call (the 
                 the MSC 104. 
               
               
                   
                   
                 user can originate 
                 After attending to 
               
               
                   
                   
                 a group call as 
                 the second call, the 
               
               
                   
                   
                 well). 
                 user may toggle to 
               
               
                   
                   
                   
                 the first call. (2) In 
               
               
                   
                   
                   
                 this case, the P2T 
               
               
                   
                   
                   
                 client application 
               
               
                   
                   
                   
                 410 sends a DTMF 
               
               
                   
                   
                   
                 signal to free the 
               
               
                   
                   
                   
                 floor. Next, the 
               
               
                   
                   
                   
                 P2T client 
               
               
                   
                   
                   
                 application 410 
               
               
                   
                   
                   
                 releases the active 
               
               
                   
                   
                   
                 call and then 
               
               
                   
                   
                   
                 originates a 
               
               
                   
                   
                   
                 cellular or group 
               
               
                   
                   
                   
                 call (by pressing 
               
               
                   
                   
                   
                 the P2T button. 
               
               
                 5. 
                 A group call is in 
                 The user wants to 
                 (1) In this case, the 
               
               
                   
                 an active state with 
                 originate another 
                 P2T client 
               
               
                   
                 a non-talking user 
                 cellular call. The 
                 application 410 
               
               
                   
                 (the P2T button is 
                 following 
                 sends a “Flash 
               
               
                   
                 free). 
                 scenarios may 
                 with Info” 
               
               
                   
                   
                 occur: (1) the user 
                 message to 
               
               
                   
                   
                 originates a second 
                 originate the 
               
               
                   
                   
                 cellular call, or (2) 
                 second cellular 
               
               
                   
                   
                 the user ends the 
                 call, while the first 
               
               
                   
                   
                 first active call and 
                 call is broken at 
               
               
                   
                   
                 originates a second 
                 the MSC 104. 
               
               
                   
                   
                 call (the user can 
                 After attending to 
               
               
                   
                   
                 also originate a 
                 the second call, the 
               
               
                   
                   
                 group call). 
                 user may toggle to 
               
               
                   
                   
                   
                 the first call. (2) In 
               
               
                   
                   
                   
                 this case, the P2T 
               
               
                   
                   
                   
                 client application 
               
               
                   
                   
                   
                 410 releases the 
               
               
                   
                   
                   
                 active call and 
               
               
                   
                   
                   
                 then originates a 
               
               
                   
                   
                   
                 cellular or group 
               
               
                   
                   
                   
                 call (by pressing 
               
               
                   
                   
                   
                 the P2T button). 
               
               
                 6. 
                 A cellular voice 
                 The user wants to 
                 (1) In this case, the 
               
               
                   
                 call is in an active 
                 originate a P2T 
                 P2T client 
               
               
                   
                 state. 
                 call. The 
                 application 410 
               
               
                   
                   
                 following 
                 sends a “Flash 
               
               
                   
                   
                 scenarios may 
                 with Info” 
               
               
                   
                   
                 occur: (1) the user 
                 message to 
               
               
                   
                   
                 originates a second 
                 originate the 
               
               
                   
                   
                 P2T call by 
                 second P2T call, 
               
               
                   
                   
                 pressing the P2T 
                 while the first call 
               
               
                   
                   
                 button, or (2) the 
                 is broken at the 
               
               
                   
                   
                 user ends the first 
                 MSC 104. After 
               
               
                   
                   
                 active call and 
                 attending to the 
               
               
                   
                   
                 originates a second 
                 second call, the 
               
               
                   
                   
                 P2T call. 
                 user may toggle to 
               
               
                   
                   
                   
                 the first call. (2) In 
               
               
                   
                   
                   
                 this case, the P2T 
               
               
                   
                   
                   
                 client application 
               
               
                   
                   
                   
                 410 releases the 
               
               
                   
                   
                   
                 active call and 
               
               
                   
                   
                   
                 then originates a 
               
               
                   
                   
                   
                 group call (by 
               
               
                   
                   
                   
                 pressing the P2T 
               
               
                   
                   
                   
                 button). 
               
               
                   
               
             
          
         
       
     
     CONCLUSION 
     The foregoing description of the preferred embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not with this detailed description, but rather by the claims appended hereto.