Abstract:
A system and method for generating Dual Tone Multi-Frequency (DTMF) tones in the media gateway of a Universal Mobile Telecommunications System (UMTS) network. The method includes receiving a DTMF signal in a media gateway controller, where the DTMF signal can be a stop tone request, or a start tone request, sending the DTMF signal from the media gateway controller to the media gateway, monitoring the status of a set of timers, where the set of timers includes a minimum tone duration timer, an inter tone timer, and a maximum tone duration timer, and responding to the received DTMF signal, said status of said timers, or a queued request. The system includes a media gateway, a plurality of timers within the media gateway, a media gateway controller, a finite state machine within the media gateway, where the finite state machine includes the following states: No Tone, Play Tone, Queue Stop Request, Inter Tone Timing, Queue Start Request, and Ready to Stop Tone.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to wireless telecommunications and more particularly to a system and method of generating Dual Tone Multi-Frequency tones in the media gateway of a Universal Mobile Telecommunications System network. 
     A major effort has been made in the last decade to integrate multimedia capabilities and mobile communications. For example, the International Telecommunications Union (ITU) and other organizations have been developing standards and recommendations to insure that mobile communications in the future will be able to support multi-media applications of at least the same quality as existing fixed networks. More specifically, many global research projects have been sponsored in order to develop such next third generation (3G) mobile systems. 3G systems are intended to provide a global mobility with wide range of services including telephony, paging, messaging, Internet and broadband data. In particular, the 3rd Generation Partnership Project (3GPP) was formed for technical development relating to this new mobile communications technology. The Universal Mobile Telecommunications System (UMTS) is a new radio access network, which is optimized for support of 3G services, including multi media-capable mobile communications. 
     One important aspect of any telecommunications system, including a UMTS network, is support of Dual Tone Multi-Frequency (DTMF) signaling. In fact, the UMTS standards specify that such systems must support DTMF signaling in the mobile-to-land direction. Generally, DTMF is the signal to the phone company that is generated when the telephone network user presses a key on the user equipment (e.g., a mobile phone). In the United States, it is more commonly known as “Touchtone” dialing. DTMF tones are used to allow a telephone network user to do such things as interact with voice mail systems, perform electronic banking, or direct the functioning of an Advanced Intelligence Network service. 
     Under the UMTS standards, which are described in detail in a number of technical specifications put out by 3GPP, the UMTS network must ensure that the minimum length of tone and the minimum gap between two subsequent tones is achieved. These two times have been defined in the standards. There is no defined maximum length to the tone, however. Significantly, the UMTS standards do not specify how to implement these important concepts. 
     Thus, there is a need in the art to provide an implementation of the UMTS standards for interconnecting DTMF signals that are present in the UMTS network and playing the tones for different durations. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a system and method of generating DTMF tones in the media gateway of a UMTS network is provided. 
     In accordance with one aspect of the present invention, the method includes receiving a DTMF signal in a media gateway controller, where the DTMF signal can be either a Stop Tone request, or a Start Tone request, sending the DTMF signal from the media gateway controller to the media gateway, monitoring the status of a set of timers, where the set of timers includes a minimum tone duration timer, an inter tone timer, and a maximum tone duration timer, and responding based on the received DTMF signal, the status of the timers, or a queued request. 
     In accordance with another aspect of the present invention, the system includes a media gateway, which includes a set of timers, a media gateway controller, a finite state machine within the media gateway, where the finite state machine includes the following states: No Tone, Play Tone, Queue Stop Request, Inter Tone Timing, Queue Start Request, and Ready to Stop Tone. 
     The advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the invention. The invention may take form in various components and arrangements of components, and in various of steps and arrangements of steps, the preferred embodiments of which will be illustrated in the accompanying drawings wherein: 
         FIG. 1  is a simplified block diagram of a typical Universal Mobile Telecommunication System network useful for discussing the present invention; 
         FIG. 2  is a block diagram of a finite state machine for generating DTMF tones in a media gateway according to the present invention; 
         FIG. 3  is a call flow diagram illustrating a short tone duration according to the present invention; 
         FIG. 4  is a call flow diagram illustrating a short gap between tones according to the present invention; and 
         FIG. 5  is a call flow diagram illustrating a maximum tone duration according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It is understood that the specific devices and processes illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Therefore, specific examples and characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     Referring to the drawings,  FIG. 1  illustrates a simplified block diagram of a typical UMTS network  100  in which a preferred embodiment of the present invention can be employed. Particularly, when initiating a mobile call, user equipment  10  communicates with a radio network  20  having at least one base station  22  via a wireless link. The user equipment  10  may be one of a variety of communication devices, such as a wireless phone or a portable personal computer with an internal or external modem. The base station  22  is in communication with and controlled by a radio network controller  24 . 
     The radio network controller  24 , in turn, communicates with a core network  30 , which may include, among other things, a service provider softswitch  32  and a media gateway  34 . The softswitch  32  is a packet switch, well known in the art, which discerns network technology and provides signaling protocols. Thus, the softswitch  32  provides the necessary call processing intelligence to the media gateway  34 . 
     The media gateway  34  is an element in the wireless network—enabling voice and data traffic to employ multiple media paths and traverse across a converged network. The media gateway  34  provides packet switching, transcoding, and media manipulation, such as tones, conferencing, and splitting, among other things. Acting as a translation unit, the media gateway  34  enables communication between disparate networks. For each mobile call, a context  36  having at least a pair of terminations T 1  and T 2  is created within the media gateway  34 . The terminations T are logical entities within the media gateway  34 , which act as sources of packet streams. The context  36  is an association between terminations T for sharing media between the terminations. The terminations T can be added or subtracted from the context  36 , and they can be moved from one context to another. Each context  36  and all of the terminations T it contains are associated with a single media gateway controller  32 . As shown in  FIG. 1 , the terminations T 1  and T 2  are in communication with each other. Voice, data, video and other media are transmitted through the radio network  20  to termination T 1 . Meanwhile, signals such as DTMF signals are transmitted through the radio network  20  to the softswitch  32 , and then on to termination T 2 . The termination T 2  is also in communication with the Public Switched Telephone Network (PSTN)  50 . 
     The softswitch  32  communicates with the media gateway  34  with standards-based control protocols, such as Megaco, and routes applicable inbound calls to the user&#39;s service. Megaco stands for “media gateway control.” Megaco (also known as H.248) is a protocol that operates between a media gateway and a media gateway controller such as a softswitch, allowing the softswitch to control the media gateway. H.248/Megaco is an emerging standard enabling voice, fax and multimedia calls to be switched between the PSTN and emerging IP networks. However, H.248/Megaco simply provides for a single duration for the DTMF tone, which is not in compliance with the UMTS standards. Therefore, the media gateway  34  preferably includes a finite state machine  200  for generating DTMF tones of different durations in the media gateway  34 . To implement the finite state machine  200 , the media gateway  34  further includes a set of timers  102 ,  104 , and  106 . The MIN timer  102  defines the minimum duration of a DTMF tone, the INTER TONE timer  104  defines the minimum interval between consecutive DTMF tones, and the MAX timer  106  defines the maximum duration of a DTMF tone. 
     Accordingly, when a user presses a key on the user equipment  10 , a DTMF signal is routed through the radio network  20  to the softswitch  32 . The softswitch  32 , in turn, sends an H.248 command to the media gateway  34  to play a tone. The media gateway  34  ultimately sources the tone to the PSTN  50  through the termination T 2 . This process of DTMF tone generation in a media gateway may be accomplished successfully and in accordance with the applicable industry standards through implementation of the novel finite state machine  200 . The operation of the finite state machine  200  will be explained in greater detail below. 
     Referring to  FIG. 2 , a preferred embodiment of the finite state machine  200  for generating DTMF tones in the media gateway  34  is shown. A common means to implement a communication protocol is to use a finite state machine (FSM). A finite state machine is a machine which has a fixed and finite number of states and in which transitions from one state to another are defined by transition rules. In  FIG. 2 , each state is indicated by a circle, while arrows connecting the states indicate allowed transitions. 
     Thus, starting at the top of the FSM  200 , a No Tone state  202  is the initial and final state of the FSM  200 . The FSM  200  is in the No Tone state  202  prior to a key (or digit) on user equipment  10  being pressed. In this state, none of the timers  102 ,  104 , or  106  have been started. When the first digit is pressed on the user equipment  10 , a Start Tone Request is made and the first transition  204  occurs to a Play Tone state  206 . At this time, the MIN timer  102  and the MAX timer  106  are started. If a Stop Tone Request is received and the MIN timer  102  has not expired, there is a transition  208  to a Queue Stop Request state  210 . Once the MIN timer  102  expires, a return acknowledgement is sent and there is a transition  212  to an Inter Tone Timing state  214 . In this state, the DTMF tone has stopped playing and the INTER TONE timer  122  has started. If a Start Tone Request is received, there is a transition  216  to a Queue Start Request state  218 . When the INTER TONE timer  104  expires, there is a transition  220  back to Play Tone state  206 . On the other hand, if a Stop Tone Request is received in the Inter Tone Timing state  214  and the INTER TONE timer  104  has not expired, a transition  222  returns to the state in which it began, the Inter Tone Timing state  214 . However, if the INTER TONE timer  104  expires, there is a transition  224  to a No Tone State  202 . 
     Returning now to the Play Tone state  206 , if the MIN timer  102  expires, there is a transition  226  to a Ready To Stop Tone state  228 . If either a Stop Tone Request is received or the MAX timer  106  expires, there is a transition  230  to the Inter Tone Timing state  214 . Finally, if a Stop Tone Request is received in the No Tone state  202 , the transition  232  returns to the state in which it started, the No Tone state  202 . Thus, the only states in which the tone is actually playing are the Play Tone state  206 , the Queue Stop Request state  218 , and the Ready To Stop Tone state  228 . 
       FIGS. 3-5  illustrate several examples of call flow diagrams for various situations and are helpful in understanding the implementation of FSM  200 . Referring now to  FIG. 3 , there is shown a call flow diagram illustrating an implementation of the FSM  200  for a Mobile-to-PSTN call having a short DTMF tone duration. Initially, a call from user equipment  10  to the PSTN  50  is established ( 302 ). The user equipment  10  then sends a Start DTMF message with digit (or key) information to the softswitch  32  ( 304 ). This is a request to play a single DTMF tone. The softswitch  32  sends an H.248 Modify command to the media gateway  34  to instruct the media gateway  34  to apply the tone ( 306 ) on the termination T 2 . As a result, the media gateway  34  starts two timers, the MIN timer  102  and the MAX timer  106 , and turns on the DTMF tone ( 308 ). The media gateway  34  then sends an H.248 Modify acknowledgement to the softswitch  32  ( 310 ). The softswitch  32  sends a Start DTMF acknowledge back to user equipment  10  ( 312 ). Meanwhile, the MIN timer  102  expires, and the tone is ready to be stopped. 
     Next, the user equipment  10  sends a Stop DTMF message to the softswitch  32  ( 314 ). The softswitch  32  then sends an H.248 Modify command to the media gateway  34  to instruct the media gateway  34  to stop applying the DTMF tone ( 316 ). The media gateway  34  turns off the tone, stops the MAX timer  106  and starts the INTER TONE timer  104  to “guard” the inter-digit interval. The media gateway  34  sends an H.248 Modify Acknowledgement message back to the softswitch  32  ( 318 ). The softswitch  32  then sends a Stop DTMF acknowledgement back to user equipment  10  ( 320 ). Meanwhile, the INTER TONE timer  104  expires, and a new tone request can now be processed. 
     User equipment  10  then sends a Start DTMF command with digit information to the softswitch  32  ( 322 ). The softswitch  32  sends an H.248 Modify command to the media gateway  34  to instruct the media gateway  34  to apply the DTMF tone on the termination T 2  ( 324 ). The media gateway  34  starts the MIN timer  102  and the MAX timer  106  and turns on the tone ( 326 ). The media gateway  34  sends an H.248 Modify acknowledgement back to the softswitch  32  ( 328 ). The softswitch  32  sends a Start DTMF acknowledgement back to the user equipment  10  ( 330 ). As a result, the user equipment  10  sends a Stop DTMF message to the softswitch  32  ( 332 ). The softswitch  32  sends an H.248 Modify command to the media gateway  34  to instruct the media gateway  34  to stop applying the DTMF tone on the termination T 2  ( 334 ). At this point, MIN timer  102  has not expired yet, and the stop signal is queued. When the MIN timer  102  expires, the media gateway  34  turns off the tone, stops the MAX timer  106  and starts the INTER TONE timer  104 . The media gateway  34  sends an H.248 Modify acknowledgement back to the softswitch  32  ( 336 ). Finally, the softswitch  32  sends a Stop DTMF acknowledgement back to the user equipment  10  ( 338 ). 
       FIG. 4  is a call flow diagram illustrating an implementation of the FSM  200  for a Mobile-to-PSTN call having a short gap between DTMF tones. Initially, a call from the user equipment  10  to the PSTN  50  is established ( 402 ). The user equipment  10  then sends a Start DTMF message with digit information to the softswitch  32  ( 404 ). This is a request to play a single DTMF tone. The softswitch  32  sends an H.248 Modify command to the media gateway  34  to instruct the media gateway  34  to apply the tone ( 406 ) on the termination T 2 . As a result, the media gateway  34  starts two timers, the MIN timer  102  and the MAX timer  106 , and turns on the DTMF tone ( 408 ). The media gateway  34  then sends an H.248 Modify acknowledgement to the softswitch  32  ( 410 ). The softswitch  32  sends a Start DTMF acknowledge back to the user equipment  10  ( 412 ). Meanwhile, the MIN timer  102  expires, and the tone is ready to be stopped. 
     Next, the user equipment  10  sends a Stop DTMF message to the softswitch  32  ( 414 ). The softswitch  32  then sends an H.248 Modify command to the media gateway  34  to instruct the media gateway  34  to stop applying the tone on the termination T 2  ( 416 ). The media gateway  34  turns off the tone, stops the MAX timer  106  and starts the INTER TONE timer  104  to guard the inter-digit interval. The media gateway  34  sends an H.248 Modify acknowledgement back to the softswitch  32  ( 418 ). The softswitch then sends a Stop DTMF acknowledgement back to the user equipment  10  ( 420 ). 
     The user equipment  10  then sends a Start DTMF message with digit information to the softswitch  32  ( 422 ). The softswitch  32  sends an H.248 Modify command to the media gateway  34  to instruct the media gateway  34  to apply the DTMF tone on the termination T 2  ( 424 ). Since the INTER TONE timer  104  has not expired, the new tone request must be queued until the INTER TONE timer  104  has expired. Once the INTER TONE timer  104  expires, the media gateway  34  starts the MIN timer  102  and the MAX timer  106  and turns on the tone ( 426 ). The media gateway  34  sends an H.248 Modify acknowledgement back to the softswitch  32  ( 428 ). The softswitch  32  sends a Start DTMF acknowledgement back to user equipment  10  ( 430 ). As a result, the user equipment  10  sends a Stop DTMF message to the softswitch  32  ( 432 ). Meanwhile, the MIN timer  102  expires, and the tone is ready to be stopped. The softswitch  32  sends an H.248 Modify command to the media gateway  34  to instruct the media gateway  34  to stop applying the tone on the termination T 2  ( 434 ). The media gateway  34  turns off the tone, stops the MAX timer  106  and starts the INTER TONE timer  104 . The media gateway  34  sends an H.248 Modify acknowledgement back to the softswitch  32  ( 436 ). Finally, the softswitch  32  sends a Stop DTMF acknowledgement back to the user equipment  10  ( 438 ). 
       FIG. 5  is a call flow diagram illustrating an implementation of the FSM  200  for a Mobile-to-PSTN call having a maximum DTMF tone duration. Initially, a call from the user equipment  10  to the PSTN  50  is established ( 502 ). The user equipment  10  then sends a Start DTMF message with digit information to the softswitch  32  ( 504 ). This is a request to play a single DTMF tone. The softswitch  32  sends an H.248 Modify command to the media gateway  34  to instruct the media gateway  34  to apply the DTMF tone ( 506 ) on the termination T 2 . As a result, the media gateway  34  starts two timers, the MIN timer  102  and the MAX timer  106 , and turns on the tone ( 508 ). The media gateway  34  then sends an H.248 Modify acknowledgement to the softswitch  32  ( 510 ). The softswitch  32  sends a Start DTMF acknowledge back to user equipment  10  ( 512 ). Meanwhile, the MIN timer  102  expires, and the tone is ready to be stopped. Then, the MAX timer  106  expires, the tone is turned off and the INTER TONE timer  104  is started. After the INTER TONE timer  104  expires, the FSM  200  is ready for the next tone. 
     The user equipment  10  sends a Stop DTMF message to the softswitch  32  ( 514 ). The softswitch  32  sends an H.248 Modify command to the media gateway  34  to instruct the media gateway  34  stop applying the tone on the termination T 2  ( 516 ). Since the tone is already off, no action is needed. The media gateway  34  sends an H.248 Modify acknowledgement back to the softswitch  32  ( 518 ). Finally, the softswitch  32  sends a Stop DTMF acknowledgement back to the user equipment  10  ( 520 ). 
     Thus, the FSM  200  describes the DTMF control standard for wireless subscribers in a UMTS network and enforces minimum tone, maximum tone, and inter-digit timing tolerances for DTMF tones, all in accordance with the applicable industry standards. It will be appreciated by those skilled in the art that the FSM  200  may be implemented through various types of hardware and software. 
     The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalence thereof.