VOICE OVER DIGITAL SUBSCRIBER LINE WITH AN EMBEDDED VOICE GATEWAY MODULE

Abstract: A telecommunication system is provided. The telecommunications system includes an access transport network having an interface coupleable to the public switched telephone network. The telecommunications system further includes at least one digital loop carrier coupled to the access transport network that provides digital subscriber line (xDSL) services to a plurality of subscribers. The at least one digital loop carrier includes an embedded gateway module that converts between packet format and a time division multiplex format to facilitate transmission of voice between the digital subscriber line and the public switched telephone network.

Description: VOICE OVER DIGITAL SUBSCRIBER LINE WITH AN EMBEDDED VOICE GATEWAY MODULE Technical Field The present invention relates generally to telecommunications, and in particular, to providing voice over a Digital Subscriber Line (DSL) with an embedded voice gateway module. Background The modern telephone system was primarily designed to transport voice signals between terminals at remote locations. Conventionally, the telephone system makes connections and routes calls through a network using switches and other electronic equipment. Prior to the 1960s, the telephone system used primarily analog switches and other analog equipment. With the increasing capability of computer systems and other digital electronics, the telephone system began to include digital switches and other equipment. For example, Digital Loop Carriers (DLCs) were developed to allow connections from a number of subscribers to be routed to a location remote from the central office and then connected to the central office over a high speed, digital line. Again, however, this digital equipment was primarily designed to handle voice signals. Over time, telecommunications systems have been used to carry data, other than voice signals, between terminals at remote locations as well. Transporting data has posed a variety of problems for conventional telephone systems. For example, as mentioned, the telephone system was designed to carry low bandwidth voice traffic. Unfortunately, these low bandwidth channels can provide a significant obstacle to providing higher bandwidth data services that have become so popular, e.g., the Internet and other data networks. To capture a portion of this data market, the telephony industry developed a group of technologies known collectively as "Digital Subscriber Line" (DSL) services, e.g., Asymmetrical Digital Subscriber Line (ADSL), High-Bit Rate Digital Subscriber Line (HDSL), Rate Adaptive Digital Subscriber Line (RADSL), Symmetric Digital Subscriber Line (SDSL), etc. These services provide high speed connections over existing copper wires used to carry conventional telephone traffic. These services use various modulation schemes and other techniques to allow the data to be transmitted over the existing copper lines at higher speeds. In addition to data, some of these DSL technologies allow multiple phone lines to share one physical line thus increasing the capacity of the system without the need to install additional copper connections between the customer and the network. Unfortunately, DSL voice traffic is not directly compatible with conventional equipment in the Public Switched Telephone Network (PSTN). For example, DSL voice traffic conventionally is incorporated in Asynchronous Transfer Mode (ATM) packets or cells. This is different from the Time Division Multiplexing (TDM) format associated with the PSTN. Further, the ATM packets are not directly compatible with signaling and other requirements of the PSTN. Therefore, a specialized voice gateway is placed at the point in the network that DSL voice traffic, e.g., from a number of DLCs, is to enter the PSTN. This voice gateway provides translation between ATM and TDM formats as well as processing the signaling and other functions required by network standards, e.g., GR-303 in North America, V5 in the International market, to prepare the voice traffic for transmission over the PSTN. One problem with this architecture is that the voice gateway is typically an expensive piece of equipment and thus inhibits the ability of service providers to introduce new subscribers to voice over DSL service. Therefore, there is a need in the art for providing voice over DSL without the use of an expensive voice gateway located at the point that the DSL voice traffic is provided to the PSTN. Summary The above mentioned problems with providing voice over DSL service and other problems are addressed by the present invention and will be understood by reading and studying the following specification. Embodiments of the present invention incorporate a voice over DSL gateway module in network equipment associated with the provision of DSL services to convert the voice data from ATM to TDM formats. Advantageously, in some embodiments of the present invention the network equipment uses existing circuitry in addition to the voice over DSL gateway module to prepare the data from the ATM cells for the legacy PSTN equipment, e.g., a GR-303 processor and DSO matrix or circuitry appropriate to another standard. In particular, an illustrative embodiment of the present invention provides a telecommunication system. The telecommunications system includes an access transport network having an interface coupleable to the public switched telephone network. The telecommunications system further includes at least one digital loop carrier coupled to the access transport network that provides digital subscriber line (xDSL) services to a plurality of subscribers. The at least one digital loop carrier includes an embedded gateway module that converts between packet format and a time division multiplex format to facilitate transmission of voice between the digital subscriber line and the public switched telephone network. Brief Description of the Drawings Figure 1 is a block diagram of one embodiment of a telecommunications network that incorporates digital loop carrier circuits having voice over Digital Subscriber Line gateway modules according to the teachings of the present invention. Figure 2 is a block diagram of one embodiment of a digital loop carrier circuit incorporating a voice over Digital Subscriber Line gateway module according to the teachings of the present invention. Figure 3 is a block diagram of another embodiment of a telecommunications network that incorporates a digital loop carrier having an embedded voice over Digital Subscriber Line gateway module according to the teachings of the present invention. Detailed Description The following detailed description refers to the accompanying drawings which form a part of the specification. The drawings show, and the detailed description describes, by way of illustration specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be used and logical, mechanical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. Figure 1 is a block diagram of one embodiment of a telecommunications network, indicated generally at 100, according to the teachings of the present invention. Network 100 includes digital loop carrier (DLC) circuits 102 — 1 , . . , 102 - N. Remote units 102 - 1, . . ., 102 - N each include integrated voice over Digital Subscriber Line (DSL) gateway modules. These gateway modules convert voice signals provided over the digital subscriber line (DSL) service, e.g., asymmetric Digital Subscriber Line (ADSL) service, to formats compatible with legacy voice systems. Advantageously, network 100 does not require an expensive, separate voice gateway located at the point of connection to the public switched telephone network (PSTN). Digital loop carrier (DLC) circuits 102 — 1, . . ., 102 — N are coupled together over access transport network 104. In one embodiment, access transport network 104 comprises an asynchronous transfer mode (ATM) network. In another embodiment, access transport network 104 comprises a synchronous optical network (e.g., SONET, SDH) with at least one virtual connection, e.g., an STS - 1, that carries DSL data and at least one virtual connection that carries time division multiplex (TDM) data. In other embodiments, access transport network 104 includes ATM functionality in at least one layer to back-haul voice data to the public switched telephone network. Each DLC circuit 102 — 1, . . ., 102 — N is coupled to a plurality of subscriber lines 106 ~ 1, . . ., 106 - N. Subscriber lines 106 — 1, . . ., 106 - N may comprise in one embodiment digital subscriber line (DSL) service lines or in another embodiment a combination of conventional plane old-fashioned telephone service (POTS) lines and digital subscriber line (DSL) service lines. In other embodiments, subscriber lines 106-1, . . ., 106-N also include Integrated Services Digital Network (ISDN) Basic Rate (BRI) service lines in combination with DSL service lines. At a minimum, it is understood that subscriber lines 106-1, . . ., 106-N include some form of DSL service lines although other services may be provided in combination with the DSL service, e.g., POTS, ISDN. For simplicity, the embodiments in this application are described in terms of providing DSL and POTS lines. It is understood that in an actual implementation some combination of DSL with POTS, ISDN or other services may be implemented. Thus, the described embodiments are provided by way of illustration and not by way of limitation. Subscriber lines 108 and 1 10 of subscriber lines 106 — 2 illustrate Digital Subscriber Line service provided over network 100 to subscribers 1 12 and 114, respectively. Subscriber 1 12 includes computer 1 16 coupled to subscriber line 108 through ADSL modem 1 18 and splitter 120. Subscriber 112 also includes telephone 122 coupled to subscriber line 108 through splitter 120. Telephone 122 is a conventional POTS telephone that operates in a conventional manner. Subscriber 112 illustrates that a single subscriber line may carry both conventional and DSL service. Subscriber 1 14 is configured for voice service using both conventional POTS and voice over DSL services using telephones 124 and 126, respectively. Subscriber 1 14 includes splitter 128. Splitter 128 is coupled to telephone 124 and to DSL modem 130. The DSL modem 130 is coupled to telephone 126 through integrated access device (IAD) 132. In another embodiment, DSL modem 130 is integrated with IAD 132. For voice over DSL service, IAD 132 samples voice signals from telephone 126, optionally compresses the data, and maps the data to ATM cells. In one embodiment, voice over DSL service is implemented using voice over ATM. In other embodiments, voice over DSL service is implemented using voice over Internet protocol (IP). Subscriber 1 14 also includes computer 134 that is coupled to IAD 132. Computer 134 is configurable to transmit and receive data over a digital subscriber line service. It is noted that subscribers 1 12 and 1 14 are provided by way of illustration and not by way of limitation. It is further understood that network 100 is designed to support access for a wide variety and quantity of end-users or subscribers through connections to Remote units 102 - 1, . . ., 102 - N. Network 100 includes an interface with the public switched telephone network. Specifically, access transport network 104 includes transport gateway 136. Transport gateway 136 selectively passes the data to either the public switched telephone network 138 through local exchange 140 or to data network 142. In operation, network 100 is configured to provide voice over Digital Subscriber Line (DSL) service. In the upstream direction, voice traffic is generated at, for example, one of telephones 126. Integrated access device 132 samples the voice data, optionally compresses the voice data, and maps the voice data to ATM cells. IAD 132 provides these ATM cells to DSL modem 130. Modem 130 transmits the ATM cells on digital subscriber line 110 to DLC 102 - 2. DLC 102 - 2 converts the ATM cells to a format that is compatible with the public switched telephone network, e.g., time division multiplex (TDM) formats such as required by standards GR 303, V5, or other appropriate standard. DLC 102 — 2 provides the TDM data to local exchange 140 via access transport network 104 and transport gateway 136. Advantageously, voice over DSL service is thus provided without a separate voice gateway connected to local exchange 140. Network 100 operates in a similar manner in the downstream direction. Another advantage of network 100 is that lifeline POTS may be provided from the same platform as voice over DSL service. Further, both voice over DSL and POTS services may be routed to the same GR303 or V5 interface with the PSTN. Figure 2 is a block diagram of one embodiment of a digital loop carrier (DLC) circuit, indicated generally at 200, incorporating a voice over Digital Subscriber Line gateway module 208 according to the teachings of the present invention. DLC circuit 200 is used, for example, as Remote units 102 - 1, . . ., 102 - - N in Figure 1. DLC circuit 200 includes line cards 202 - 1 , . . ., 202 - N. Line cards 202 - 1, . . ., 202 — N provide an interface between DLC circuit 200 and a plurality of subscriber lines. Line cards 202 - 1, . . ., 202 — N include at least one line card that supports a digital subscriber line service, e.g., ADSL. Each of line cards 202 - 1, . . ., 202 — N may also support POTS telephony. In one embodiment, at least one of line cards 202 - 1, . . ., 202 — N comprises a line card that supports both POTS and DSL services. In another embodiment, at least one of line cards 202 - 1, . . ., 202 — N supports only DSL services. Again, one or more of line cards 202-1, . . ., 202 -N may also support other services such as Basic Rate ISDN or any other appropriate service. DLC circuit 200 also includes three modules that are connected to line cards 202 - 1, . . ., 202 - N. First, DLC circuit 200 includes transport module 204. Transport module 204 is coupled to line cards 202 - 1, . . ., 202 — N. When line cards 202 - 1, . . ., 202 — N support DSL services they provide packet data from a digital subscriber line service to transport module 204. Transport module 204 also includes an interface to the network such as access transport network 104 of Figure 1. Through the support of transport module 204, line cards 202 - 1, . . ., 202 - N gain access to the public switched telephone network as well as other data networks. DLC circuit 200 also includes network interface module 206. Network interface module 206 is coupled to line cards 202 - 1, . . ., 202 — N. Line cards 202 - 1 , . . ., 202 - N provide the data in time division multiplex (TDM) formats to network interface module 206. In one embodiment, network interface module 206 comprises a GR 303 processor and a DS-0 matrix. Network interface module 206 performs necessary functions for processing voice traffic destined for the public switched telephone network. Thus, the connection between line cards 202 - 1, . . ., 202 — N and network interface module 206 provides POTS service for the subscriber lines. Network interface module 206 is coupled to transport module 204. DLC circuit 200 also includes voice over DSL (VoDSL) gateway module 208. Module 208 is coupled to line cards 202 - 1 , . . ., 202 - N. line cards 202 - 1 , . . ., 202 — N provide voice packets, e.g., ATM cells, Internet protocol packets carried in ATM cells. Module 208 converts the packets received from one of line cards 202 - 1, . . ., 202 — N from a packet format, e.g., ATM, to a time division multiplex format compatible with the public switched telephone network. Module 208 is coupled to network interface module 206. In operation, digital loop carrier circuit 200 supports voice over DSL service for a number of subscriber lines. For example, line card 202 — 1 receives voice over DSL data from its subscriber line. This data includes ATM cells that are provided to module 208 as voice packets. Module 208 converts the ATM cells to a time division multiplex format compatible with the public switched telephone network. Module 208 provides the time division multiplex data to network interface module 206. Network interface module 206 prepares this data to be provided to the public switched telephone network. Network interface module 206 further passes the data from the ATM cells to an access transport network through transport module 204. In the downstream direction, TDM data is received by transport module 204 and provided to network interface module 206 further, the TDM data after processing by network interface module 206 is provided to module 208 for conversion to packet data. The packet data from module 208 is provided to line card 202 ~ 1 for transmission as voice over DSL service to a subscriber. DLC circuit 200 advantageously may provide both lifeline POTS and voice over DSL services from the same platform. Further, both voice over DSL and POTS services may be routed to the same GR303 or V5 interface with the PSTN. Figure 3 is a block diagram of another embodiment of a telecommunications network, indicated generally at 300, according to the teachings of the present invention. Network 300 includes a digital loop carrier (DLC) including central unit 301 and remote units 302 — 1, . . , 302 - N. Central unit 301 includes an integrated voice over Digital Subscriber Line (DSL) gateway module. This gateway module converts voice signals provided over the digital subscriber line (DSL) service, e.g., asymmetric Digital Subscriber Line (ADSL) service, to formats compatible with legacy voice systems in the public switched telephone network. Advantageously, network 300 does not require an expensive, separate voice gateway located at the point of connection to the public switched telephone network (PSTN). Remote units 302 — 1, . . ., 302 — N and central unit 301 are coupled together over access transport network 304. In one embodiment, access transport network 304 comprises an asynchronous transfer mode (ATM) network. In another embodiment, access transport network 304 comprises a synchronous optical network (e.g., SONET, SDH) with at least one virtual connection, e.g., an STS - 1, that carries DSL data and at least one virtual connection that carries time division multiplex (TDM) data. In other embodiments, access transport network 304 includes ATM functionality in at least one layer to back-haul voice data to the public switched telephone network. Each remote unit 302 — 1, . . ., 302 — N is coupled to a plurality of subscriber lines 306 — 1, . . ., 306 - N. Subscriber lines 306 — 1, . . ., 306 - M comprise a combination of conventional plane old-fashioned telephone service (POTS) lines and digital subscriber line (DSL) service lines. In other embodiments, subscriber lines 306-1, . . ., 306-N also include Integrated Services Digital Network (ISDN) Basic Rate (BRI) service lines in combination with DSL service lines. At a minimum, it is understood that subscriber lines 306-1, . . ., 306-N include some form of DSL service lines although other services may be provided in combination with the DSL service, e.g., POTS, ISDN. For simplicity, the embodiments in this application are described in terms of providing DSL and POTS lines. It is understood that in an actual implementation some combination of DSL with POTS, ISDN or other services may be implemented. Thus, the described embodiments are provided by way of illustration and not by way of limitation. Subscriber lines 308 and 310 of subscriber lines 306 — 2 illustrate Digital Subscriber Line service provided over network 300 to subscribers 312 and 314, respectively. Subscriber 312 includes computer 316 coupled to subscriber line 308 through ADSL modem 318 and splitter 320. Subscriber 312 also includes telephone 322 coupled to subscriber line 308 through splitter 320. Telephone 322 is a conventional POTS telephone that operates in a conventional manner. Subscriber 312 illustrates that a single subscriber line may carry both conventional and DSL service. Subscriber 314 is configured for voice service using both conventional POTS and voice over DSL services using telephones 324 and 326, respectively. Subscriber 314 includes splitter 328. Splitter 328 is coupled to telephone 324 and to DSL modem 330. DSL modem 330 is coupled to telephone 326 through integrated access device (IAD) 332. In another embodiment, DSL modem 330 is integrated with IAD 332. For voice over DSL service, IAD 332 samples voice signals from telephone 326, optionally compresses the data, and maps the data to ATM cells. In one embodiment, voice over DSL service is implemented using voice over ATM. In other embodiments, voice over DSL service is implemented using voice over Internet protocol (IP). Subscriber 314 also includes computer 334 that is coupled to IAD 332. Computer 334 is configurable to transmit and receive data over a digital subscriber line service. It is noted that subscribers 312 and 314 are provided by way of illustration and not by way oflimitation. It is further understood that network 300 is designed to support access for a wide variety and quantity of end-users or subscribers through connections to remote units 302 - 1, . . ., 302 - N. Network 300 includes an interface with the public switched telephone network. Specifically, remote units 302 — 1, . . ., 302 - N are coupled to central unit 301 by access transport network 304 central unit 301 selectively passes the data to either the public switched telephone network 338 through local exchange 340 or to data network 342. Central unit 301 also includes an embedded voice gateway that converts between packet data and time division multiplex formats compatible with the public switched telephone network. In operation, network 300 is configured to provide voice over Digital Subscriber Line (DSL) service. In the upstream direction, voice traffic is generated at, for example, one of telephones 326. Integrated access device 332 samples the voice data, optionally compresses the voice data, and maps the voice data to ATM cells. IAD 332 provides these ATM cells to DSL modem 330. Modem 330 transmits the ATM cells on digital subscriber line 310 to remote unit 302 — 2. Remote unit 302 — 2 forwards the cells to central unit 301 which converts the ATM cells to a format that is compatible with the public switched telephone network, e.g., time division multiplex (TDM) formats such as required by standards GR 303, V5, or other appropriate standard. Central unit 301 provides the TDM data to local exchange 340 via access transport network 304 and transport gateway 336. Advantageously, voice over DSL service is thus provided without a separate voice gateway connected to local exchange 340. Network 300 operates in a similar manner in the downstream direction. Another advantage of network 300 is that lifeline POTS may be provided from the same platform as voice over DSL service. Further, both voice over DSL and POTS services may be routed to the same GR303 or V5 interface with the PSTN. Conclusion Although specific embodiments have been illustrated and described in this specification, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. For example, various transport networks can be used to connect the DLC with the PSTN. Further, other xDSL services can be used to provide voice over DSL service. Also, the embodiments described can be used with any appropriate TDM based telephony network.

Claims: What is claimed is: 1. A telecommunication system, comprising: an access transport network having an interface coupleable to the public switched telephone network; at least one digital loop carrier coupled to the access transport network and providing digital subscriber line (xDSL) services to a plurality of subscribers; and wherein the at least one digital loop carrier includes an embedded gateway module that converts between packet format and time division multiplex format to facilitate transmission of voice between the digital subscriber line and the public switched telephone network. 2. The telecommunications system of claim 1 , wherein the at least one digital loop carrier and the access transport network comprise a plurality of integrated digital loop carrier units coupled to a synchronous optical network backbone. 3. The telecommunications system of claim 1, wherein: the access transport network comprises a synchronous optical network backbone; and the at least one digital loop carrier comprises a universal digital loop carrier with a plurality of remote terminals and a central terminal, wherein the central terminal includes the embedded gateway module. 4. The telecommunications system of claim 1, wherein the access transport network comprises an asynchronous transfer mode (ATM) network. 5. The telecommunications system of claim 1, wherein the access transport network comprises a hybrid transport network on a synchronous optical network infrastructure with at least one virtual path for ATM cells and at least one virtual path of TDM data. 6. The telecommunications system of claim 1 , wherein the at least one digital loop carrier provides asymmetrical digital subscriber line (ADSL) service. 7. The telecommunications system of claim 1, wherein the at least one digital loop carrier uses voice over ATM to implement voice over DSL. 8. The telecommunications system of claim 1 , wherein the at least one digital loop carrier uses voice over IP to implement voice over DSL. 9. A digital loop carrier, comprising: at least one line card having an input that is coupleable to a subscriber line, and that supports at least one digital subscriber line (xDSL) service; a transport module coupled to the at least one line card and providing a connection to an access transport network; a digital network interface module, coupled to the at least one line card and to the transport module, that prepares input signals for transmission by the transport module on the access transport network; and a voice over Digital Subscriber Line gateway module coupled to the at least one line card and to the digital network interface module, that converts signals between an packet format and a time division multiplex format to facilitate communication between the at least one line card and the public switched telephone network. 10. The digital loop carrier of claim 9, wherein the at least one line card comprises a line card that supports asymmetric digital subscriber line (ADSL) services. 1 1. The digital loop carrier of claim 9, wherein the transport module is configured to provide a connection to a synchronous optical network backbone. 12. The digital loop carrier of claim 9, wherein the digital network interface module includes a GR-303 processor and a DSO matrix. 13. The digital loop carrier of claim 9, wherein the digital network interface module includes a V5 processor. 14. The digital loop carrier of claim 9, wherein the at least one line card supports voice over DSL service using voice over ATM. 15. The digital loop carrier of claim 9, wherein the at least one line card supports voice over DSL service using voice over IP. 16. A method for providing voice services over a digital subscriber line, the method comprising: receiving voice signals over the digital subscriber line; converting the voice signals from a packet format to a time division multiplex format at a digital loop carrier; and transporting the voice signals in the time division multiplex format to an interface with the public switched telephone network. 17. The method of claim 16, wherein receiving voice signals comprises receiving voice signals over asymmetric digital subscriber line (ADSL) service. 18. The method of claim 16, wherein converting the voice signals comprises converting signals from asynchronous transfer mode (ATM) format to a time division multiplex format. 19. The method of claim 16, wherein receiving voice signals comprises receiving voice signals in voice over Internet protocol (VoIP) format. 20. The method of claim 16, wherein receiving voice signals comprises receiving voice signals in voice over asynchronous transfer mode (ATM) format. 21. The method of claim 16, wherein transporting the voice signals comprises transporting the voice signals over an ATM network. 22. The method of claim 16, wherein transporting the voice signals comprises transporting the voice signals over a synchronous optical network. 23. The method of claim 16, wherein converting the voice signals comprises converting the voice signals at a central office terminal of a digital loop carrier. 24. A communication system, comprising: an access transport network; a central unit coupled to the access transport network and having an interface coupleable to the public switched telephone network; at least one remote unit communicatively coupled to the central unit by the access transport network and including a plurality of ports, wherein at least one port is configurable to provide digital subscriber line (xDSL) services to a plurality of subscribers; and wherein the central unit includes an embedded gateway module that converts between a packet format and a time division multiplex format to facilitate transmission of voice between the digital subscriber lines and the public switched telephone network. 25. The system of claim 24, wherein the access transport network comprises an asynchronous transfer mode (ATM) network. 26. The system of claim 24, wherein the access transport network comprises a synchronous optical network. 27. The system of claim 24, wherein the embedded gateway converts between asynchronous transfer mode (ATM) and a time division multiplex format compatible with the public switched telephone network (PSTN). 28. The system of claim 24, wherein at least one port of the at least one remote unit is configurable to provide asymmetric digital subscriber line (ADSL) service. 29. The system of claim 24, wherein at least one port of the at least one remote unit is configurable to provide digital subscriber line service using voice over ATM. 30. The system of claim 24, wherein at least one port of the at least one remote unit is configurable to provide digital subscriber line service using voice over Internet protocol (IP). 31. A telecommunication system, comprising: an access transport network having an interface coupleable to the public switched telephone network; at least one digital loop carrier coupled to the access transport network and providing digital subscriber line (xDSL) and lifeline POTS services to a plurality of subscribers; and wherein the at least one digital loop carrier includes an embedded gateway module that converts between packet format and time division multiplex format to facilitate transmission of voice between the digital subscriber line and the public switched telephone network.

Inventors: SAAD YOSSEF, SAAD, YOSSEF
Applicants: ADC TELEDATA COMMUNICATIONS LT, ADC TELEDATA COMMUNICATIONS, LTD.
Application year: 2001
Main classification: H04L12
IPC codes: H04L12, H04Q11