Architecture, client specification and application programming interface (API) for supporting advanced voice services (AVS) including push to talk on wireless handsets and networks

[0001] 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:

[0002] 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

[0003] 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;

[0004] both of which applications are incorporated by reference herein.

[0005] 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:

[0006] 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:

• • [0007] 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:
    • [0008] Ser. No. 60/382,981, filed on May 24, 2002, by Gorachand Kundu, Ravi Ayyasamy, and Krishnakant Patel, entitled RADIO GATEWAY ARCHITECTURE FRAMEWORK;
    • [0009] Ser. No. 60/383,179, filed May 24, 2002, by Gorachand Kundu, Ravi Ayyasamy, and Krishnakant Patel, entitled DISPATCH SERVICE ARCHITECTURE FRAMEWORK; and
    • [0010] Ser. No. 60/407,168, filed Aug. 30, 2002, by Gorachand Kundu, Ravi Ayyasamy, and Krishnakant Patel, entitled DISPATCH SERVICE ARCHITECTURE FRAMEWORK; and

[0011] 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:

• • [0012] Ser. No. 60/488,638, filed on Jul. 18, 2003, by F. Craig Farrill, Bruce D. Lawler and Krishnakant Patel, entitled REAL-TIME EXCHANGE;
  • [0013] 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
  • [0014] 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;

[0015] all of which applications are incorporated by reference herein.

[0016] 1. Field of the Invention

[0017] 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.

[0018] 2. Description of Related Art

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0031] 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.

[0032] Overview

[0033] 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.

[0034] Network Architecture

[0035] 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.

[0036] 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.

[0037] 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).

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] Real Time Exchange

[0044] FIG. 2 illustrates a proposed architecture for the RTX 102 according to the preferred embodiment of the present invention.

[0045] 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.

[0046] 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).

[0047] 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.

[0048] P2T State Diagram

[0049] FIG. 3 is a state diagram that illustrates the operation of a P2T call according to a preferred embodiment of the present invention.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] State 310 represents a terminating leg being released from the group call after the user ends the call.

[0057] State 312 also represents a terminating leg being released from the group call after the user ends the call.

[0058] 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.

[0059] Mobile Handset Components

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.)

[0064] 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.

[0065] P2T Client Application and Presence/Group Management Application

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] The NV memory 512 is also used to store the configuration parameters, which can be updated by the RTX as required.

[0079] User Interactions with the Mobile Handset

[0080] This section describes various scenarios that a group user may explicitly invoke through the mobile handset 120.

[0081]

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's
		the called party'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'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's
	he/she can enter called	address parameter filled
	party'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'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's leg from the
		group call.

[0082] 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.

[0083] Network Interactions with the Mobile Handset

[0084] 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.

[0085]

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'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'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.

[0086] Service Interactions with the P2T Client Application

[0087] 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'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.

[0088] 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.

[0089] 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.

[0090]

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'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).

[0091] 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.