SYSTEM AND METHOD FOR SUPPORTING DTMF TONE SENDING IN AN IP BASED GSM NETWORK

Abstract: The present invention provides a system and method for reliably transferring Dual Tone Multiple Frequency (DTMF) signals originating at an MS through an IP based GSM network. In general, when an MS sends a DTMF request, it is processed in the IP network by a logical application module in an MSC, which, based on the disclosed processing, activates another logical application module in an appropriate gateway (for independent tone generation), and then the logical application module in the gateway directs the production of the DTMF signal in the destination network.

Description: SYSTEM AND METHOD FOR SUPPORTING DTMF TONE SENDING IN AN IP BASED GSM NETWORK TECHNICAL FIELD The invention relates generally to telecommunications and more particularly to a system and method of sending Duel Tone Multiple Frequency (DTMF) tones having an Internet Protocol (IP) based network backbone (also called a trunk) through a Global System for Mobile Communications (GSM). BACKGROUND OF THE INVENTION Dual Tone Multiple Frequency (DTMF) tones are used to, for example, allow a telephone network user to direct the functioning of an Advanced Intelligence Network (AIN). Traditionally, in a PSTN, DTMF tones are generated by a hand set. However, in a GSM, if DTMF tones were transmitted from a Mobile Station (MS) handset, the DTMF signals would be mutilated by a transcoder, and could not pass to the network. Thus, for a MS in a GSM to send DTMF tones, a tone generation command (rather than the actual tone) is sent from the MS and routed to a Mobile Switching Center (MSC). The tones are then typically generated by the MSC and sent to a destination device. As the use of mobile systems has proliferated, and the number of cell phone users has grown, additional demands have been placed on GSM networks. One of the features users employ that places additional demands on GSM systems is the transmission of DTMF tones across the GSM network to accomplish, for example, voice mail interaction or electronic banking. Sometimes the number of users attempting to use the GSM cellular network exceeds the capacity of the system, and thus, some call placements go unconnected (resulting in frustrated users and lost revenues). Networks utilizing Internet Protocols (IP) are readily available, offer defined system interface protocols, and have the ability to reliably transmit voice data. Accordingly, IP networks have been used as a communications backbone suitable for providing a platform to trunk the excess GSM network demands, thus increasing the capacity of the network and allowing more calls to connect. The increased call capacity provided by the IP network, however, comes at a cost. Unfortunately, there does not exist a reliable system or method of transferring a DTMF tone through an IP based GSM network. Thus, when an IP network is used as a backbone for GSM calls, those calls using the IP network are unable to reliably send DTMF signals. Therefore, there exists the need for a system and method of sending DTMF tones reliably through a GSM based telecommunications network which uses an IP network as a backbone. SUMMARY OF THE INVENTION The present invention provides a system and method for reliably transferring dual tone multiple frequency tones through an IP based GSM network. In general, when a MS sends a DTMF request (typically a DTAP message called "Start DTMF"), it is processed in the IP network by a MSC, which, based on the disclosed processing, activates a software module and an appropriate gateway (for independent tone generation), and then a processor in the gateway directs the production of the DTMF signal in the destination network. In one aspect the present invention provides a system for sending DTMF tones through an IP network in the GSM. The system generally comprises a mobile switching center having a first logical application module which receives a Direct Transfer Application Part (DTAP) message and converts the DTAP message into a Device Control Message (DCM). The system also contains a gateway coupled to the mobile switching center and has a second logical application module which directs the generation of the tone in the destination communication system. The system may provide the capacity for the first logical application module to pass the DTAP message to the second logical application module. In addition, the second logical application module may send a failure message to the first logical application module when the destination communication system is not in a state capable of receiving a tone. The second logical application module may also select the tone generation method and direct the creation and routing of the tone to the destination communication system. The gateway of the system may be in communication with a Public Switched Telephone Network (PSTN), an IP network, or a mobile phone network. The method of supporting DTMF tone sending in an IP based GSM network utilizes the steps of receiving a DTAP command from a GSM compatible mobile phone system, converting the DTAP command into a device control message, instructing a tone generator to generate a DTMF tone, and sending the DTMF tone to the destination communication system. The destination communication system utilized in this method could be a PSTN. In addition, the DTAP command used to initialize the method could be a third level GSM command. Likewise, another method of supporting DTMF tone sending in a IP based GSM network utilizes the steps of receiving a DTAP command from a GSM compatible mobile phone system, converting the DTAP command into a device control message, and selecting a DTMF tone generator method compatible with the destination IP network. The tone generator method could comprise the steps of ordering a tone generator to generate a DTMF tone and then routing the DTMF tone to a destination IP network. Alternatively, the tone generator method could comprise the step of generating a DTMF tone by placing tone generating RTP data packets into the data stream. The command used to initialize this method could comprise a third level GSM command. Alternatively, another method of supporting DTMF tone sending in an IP based GSM network could comprise the steps of receiving a DTAP command from a GSM compatible source mobile phone system, converting the DTAP command into a device control message, ordering a tone generator to generate a DTMF tone, and routing the DTMF tone through the tone generator to a destination mobile phone system. This method could also use a third level GSM command to initialize the DTAP command. BRIEF DESCRIPTION OF THE DRAWINGS Other aspects of the invention, including specific embodiments, are understood by reference to the following detailed description taken in conjunction with the drawings in which: Figure 1 shows a prior art GSM configuration; Figure 2 illustrates a GSM network having an Internet Protocol (IP) network for its backbone; Figure 3 is a flow diagram showing the steps for communicating a DTMF tone from a mobile station to a PSTN in a GSM across an IP backbone; Figure 4 provides a block flow diagram illustrating the steps for communicating a DTMF from a mobile station to an IP based network in a GSM across an IP backbone; and Figure 5 depicts the flow of logic for communicating a DTMF from an MS to another MS across a GSM having an IP backbone. References in the detailed description correspond to like references in the figures unless otherwise indicated. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 shows a prior art GSM network denoted generally as 100. Within the network 100, a MS 120 communicates with a Base-station Transceiver Substation (BTS) 130 via radio communications (illustrated in Figure 1 and other Figures as a lightening bolt). The BTS 130 then communicates with a Base Station Controller (BSC) 140. The BSC 140 then routes the communications between the BTS 130 and a Mobile Switching Center (MSC) 150. Although only one BTS 130 is shown, in a typical GSM network, a plurality of BTSs are connected to a BSC. Likewise, a plurality of BSCs are typically attached to a MSC 150. The MSC 150 may then be connected to a standard GSM based network backbone which carries calls from the MS 120 to a destination device through a destination network 160, (which may be a PSTN, an JP, or a mobile phone network). In a prior art GSM, DTMF tone sending is not done directly by a MS. This is because a DTMF tone, if sent by a MS, would be mutilated by a transcoder in a MS. Because they are mutilated, the tones would not then be recognized by an application which needs to interpret them. Instead, according to the present invention, when a user of the MS 120 attempts to send a tone from the MS 12, instead of the tone being sent from the MS 120 to the BTS 130, a Direct Transfer Application Part (DTAP) message, "Start DTMF", is sent from the MS 120 to the BTS 130. The Start DTMF message routes through the BSC 140, and then to the MSC 150. The MSC 150 then connects an appropriate tone sending device to the network and instructs the tone sending device to insert a tone into the network 160. If the MSC 150 detects that the tone sending was successful, the fact that the tone sending was successful is reported to the MS 120 with a "Start DTMF Acknowledge" message. If the tone generation fails, the failure is reported to the MS 120 using a "Start DTMF Reject" message. Figure 2 illustrates a GSM network having an IP network 270 for its backbone. MS 220 is in communication with BTS 222 which is wire connected to an IP network 270. MS 220 may communicate with a variety of destination networks. Accordingly, another mobile station 266 is shown in radio communication with another BTS 264 which is wire coupled to the IP network 270. In addition, MSC 230 having a DTMF MSC processor (DMSCT) 232 therein is in communication with the IP network 270. Also attached to the IP network 270 is a Gateway (GW) 260 having therein a DTMF Media Gateway Processor (DMGP) 262 for directing tone generation and signal evaluations. Another GW 240 is coupled between the IP network 270 and a PSTN 244, the GW 240 having therein a DMGP 242 for directing the routing of a tone to the PSTN 244 and for evaluating whether or not the tone was successfully received by a destination device. Furthermore, the system of the present invention comprises a GW 250 coupled between the IP network 270 and an Internet Protocol based Network 254, the GW 250 having therein a DMGP for directing the generation of a tone into the IP network 254 and for evaluating signal sending success. Thus, from Figure 2, it can be seen that the present invention can be used to route a tone originating from a mobile station through an IP based network backbone, and then send the tone to, for example, a PSTN, an IP, or another MS. CASE ONE Figure 3 is a flow diagram which shows the steps for communicating a DTMF tone from a MS 220 to a PSTN 244 in a GSM having an IP backbone 270. In an initialization, step 310, the MS 220 sends a "Start DTMF" message to the Logical Application Module known as the DTMF MSC Processor (DMSCP) 232, which resides in the MSC 230. Next, through a conversion, step 312, the DMSCP 232 processes the start DTMF into a device control message, which is then transported to a LAM called a DTMF Media Gateway Processor (DMGP) 242 (the DMGP 242 is stored and executed in the GW 240) in a transport, step 314. Next, the DMGP 242 checks to determine if the destination device (not shown) is available in a destination check, step 320. If the destination device is not ready or able to receive a DTMF tone, the DMGP 242 sends a the MSC 230 of the failure in a rejection notice, step 324. To report the failure to the MS, the DMSCP 232 then sends a "Start DTMF Reject" notice to the MS 220 in a MS rejection notice, step 326. If the DMGP 242 detects that the destination device can receive a DTMF tone, then the DMGP 242 directs the tone generation. How the tone is generated depends on the devices available for tone generation, which are analyzed in a gateway tone, step 330. In this case, if the GW 240 can generate a tone, then the GW 240 generates the tone in a GW tone generation, step 332. Then, the tone is routed to the appropriate destination device in a tone routing, step 338. If the GW 240 cannot generate a tone, then the DMGP 242 commands a tone generation device, such as another GW 260, to generate the tone in a tone command, step 334. In a tone generation, step 336, the tone generation device produces the tone. The tone routing is then directed by the DMGP 242 in a tone routing, step 338. Following the tone routing, step 338, the DMGP 242 detects whether or not the destination device received the tone in a success check, step 340. If the tone generation is unsuccessful the DMGP 242 sends a rejection notice to MSC 230 in a rejection notice, step 324. Next, the DMSCP 232 sends a "Start DTMF Reject" notice to the MS 220 to report the failure in a MS rejection notice, step 326. If the tone generation is successful the DMGP 242 notifies the DMSCP 232 of the successful tone transmission in a success notice, step 342. Then, the DMSCP 232 notifies the MS 220 of the tone generation by sending a "Start DTMF Acknowledge" message in a MS success notice, step 344. Figure 4 provides a block flow diagram illustrating the steps for communicating a DTMF tone from a MS 220 to an IP based network 254 through a GSM having an IP backbone 270. In an initialization, step 410, the MS 220 sends a "Start DTMF" message to the logical application module DMSCP 232 in the MSC 230. Next, through the conversion, step 412, the DMSCP 232 processes the start DTMF into a device control message, which is transported to a LAM, DMGP 252, in the GW 252 in a transport, step 414. The DMGP 252 then checks to determine if the destination device (not shown) is available in a destination check, step 420. If the destination device is not ready or able to receive a DTMF tone, the DMGP 252 sends a rejection notice to the MSC 230 in a rejection notice, step 424. The DMSCP 232 then sends a "Start DTMF Reject" notice to the MS 220 to report the transmission failure in a MS rejection notice, step 426. If the DMGP 252 senses that the destination device can receive a DTMF tone, then the DMGP 252 directs the tone generation, depending on available tone generation techniques, which are analyzed in a gateway tone, step 430. If the GW 250 can generate a tone, as in Case One, the GW generates the tone in a GW tone generation, step 432. The tone is then routed to the appropriate destination device in a tone routing, step 438. If the GW 250 cannot generate a tone, then the DMGP 252 places tone generating RTP data packets into the EP network data stream in a RTP stream, step 436. The routing of the RTP data packets is accomplished in the tone routing, step 438. Following the tone routing, step 438, the DMGP 252 detects whether or not the destination device received the tone in a success check, step 440. If the tone generation fails, the DMGP 252 sends a rejection notice to MSC 230 in a rejection notice, step 424. Next, the DMSCP 232 sends a "Start DTMF Reject" notice to the MS 220 to report the failure in a MS rejection notice, step 426. If the tone generation is successful, the DMGP 252 notifies the DMSCP 232 of the tone in a success notice, step 442. Then, the DMSCP 232 notifies the MS 220 of the tone generation by sending a "Start DTMF Acknowledge" message in a MS success notice, step 444. CASE THREE Figure 5 depicts the flow of logic for communicating a DTMF from a MS 220 to another MS 266 across an IP based backbone 270 in a GSM. In an initialization, step 510, the MS 220 sends a start DTMF message to the LAM DMSCP 232 in the MSC 230. Next, through the conversion step the DMSCP 232 changes the start DTMF into a device control message, which is transported to a LAM, DMGP 262, which is in the GW 260, in a transport, step 514. The DMGP 262 then checks to determine if the destination device (not shown) is available in a destination check, step 520. If the destination device is not ready or able to receive a DTMF tone, the DMGP 262 sends a rejection notice to the MSC 230 in a rejection notice, step 524. The DMSCP 232 then sends a "Start DTMF Reject" notice to the MS 220 to report the failure in a MS rejection notice, step 526. If the destination device can receive a DTMF tone, then the DMGP 262 directs the tone generation. Tone generation is implemented by first issuing a generate tone command in a tone command, step 534. The selected tone generating device then produces the tone in a tone generation, step 536. Next, the DMGP 262 routes the tone to the appropriate destination device in a tone routing, step 538. Following the tone routing, step 538, the DMGP 262 detects whether or not the destination device received the tone in a success check, step 540. If the tone generation step fails, the DMGP 262 sends a rejection notice to the MSC 230 in a rejection notice, step 524. The DMSCP 232 then sends a "Start DTMF Reject" notice to the MS 220 to report the failure in a MS rejection notice, step 526. If the tone generation is successful, the DMGP 262 notifies the DMSCP 232 of the tone in a success notice, step 542. Then, the DMSCP 232 notifies the MS 220 of the tone generation by sending a "Start DTMF Acknowledge" message in a MS success notice, step 544. While the invention has been described with preferred embodiments it should be understood that modifications will become apparent to those of ordinary skill in the art and that such modifications are intended to be included with the scope of the invention as defined by the following claims. JO-

Claims: What is claimed is: A system for sending Dual Tone Multi-Frequency (DTMF) tones through an Internet Protocol (IP) based network in a Global System for Mobile Communications (GSM), the system comprising: a mobile switching center (MSC) having a first logical application module (LAM), said first LAM configured for receiving a Direct Transfer Application Part (DTAP) DTMF message and converting the DTAP DTMF message into a device control message; and a gateway coupled to the MSC and having a second LAM, said second LAM configured for receiving said device control message, and configured for directing the generation of a DTMF tone on a destination network. 2. The system of Claim 1 wherein the first LAM passes the DTAP DTMF message to the second LAM through said IP based network. 3. The system of Claim 1 wherein the second LAM is configured to send a failure message to the first LAM when the destination communication system is not capable of receiving a DTMF tone. 4. The system of Claim 1 wherein the second LAM is configured to directs if the destination communications system is capable of receiving a tone. 5. The system of Claim 1 wherein the gateway is in communication with a Public Switched Telephone Network (PSTN). 6. The system of Claim 1 wherein the gateway is in communication with an IP Network. 7. The system of Claim 1 wherein the gateway is in communication with a Mobile Phone Network. 8. The system of Claim 1 wherein the gateway is configured to generate DTMF tones. 9. The system of Claim 1 wherein the second LAM is configured to detect if a tone generation attempt was successful. 10. The system of Claim 1 wherein the second LAM is configured to send a success notice to the first LAM. 11. A method of supporting DTMF tone sending in an IP based GSM network, comprising the steps of: receiving a DTAP DTMF command from a GSM compatible mobile phone system; converting the DTAP DTMF command into a device control message; ordering a tone generator to generate a DTMF tone receivable by a destination network; and sending the DTMF tone to the destination network. 12. The method of claim 11 wherein the destination network is a PSTN. 13. The method of claim 11 wherein the DTAP DTMF command is comprised in a third level GSM command. 14. The Method of claim 11 further comprising the step of determining if the DTMF tone was received by the destination network. 15. A method of supporting DTMF tone sending in an IP based GSM network, comprising the steps of: receiving a DTAP DTMF command from a GSM compatible mobile phone system; converting the DTAP DTMF command into a device control message; and selecting a DTMF tone generator method compatible with a destination IP network. 16. The method of claim 15 wherein the step of selecting a DTMF tone generator method further comprises the steps of: ordering a tone generator to generate a DTMF tone; and sending the DTMF tone to the destination IP network. 17. The method of claim 15 wherein the step of selecting a DTMF tone generator method further comprises the step of generating a DTMF tone by placing tone generating RTP data packets into the data stream. 18. The method of claim 15 wherein the DTAP DTMF command is comprised in a third level GSM command. 19. A method of supporting DTMF tone sending in an EP based GSM network, comprising the steps of: receiving a DTAP DTMF command from a GSM compatible source mobile phone system; converting the DTAP DTMF command into a device control message; ordering a tone generator to generate a DTMF tone; and routing the DTMF tone through the tone generator to a destination mobile phone system. 20. The method of claim 15 wherein the DTAP DTMF command is comprised in a third level GSM command.

Inventors: DAVIDSON LEE, HAMELEERS HEINO, VALENTINE ERIC, DAVIDSON, LEE, HAMELEERS, HEINO, VALENTINE, ERIC
Applicants: ERICSSON INC, ERICSSON, INC.
Application year: 2000
Main classification: H04Q7
IPC codes: H04W88