Proxy modem for voice over internet protocol based communication system

In a packet data communications system (100) where a customer premises (120) has only a packet-based connection, a proxy modem (200) is provided at the customer premises to connect to devices that send and receive modulated transmissions, e.g., facsimile, modem, and TDD/TTY. The proxy modem demodulates the modulated transmissions (208), organizes the resulting digital signal into a packet (210) and forwards the packet over a packet network (104, 106). Another proxy modem (200) that connects to the packet network and to a telephony network (110) receives the packets from the packet network. The packets are re-organized into a digital signal that is then modulated and forwarded over the telephony network to a destination. Use of the proxy modems in the network prevents unnecessary digitizing of modulated transmissions, which slows transmission and introduces errors.

FIELD OF THE INVENTION

The present invention relates generally to telephony services, and in particular, to a method and apparatus that provides a virtual or proxy modem for modulated services in an Internet protocol communication system.

BACKGROUND OF THE INVENTION

Voice over Internet protocol (VoIP) telephone services are known. Such systems allow voice calls using Internet Protocol (“IP”) networks such as the Internet as an alternative to traditional public switched telephone networks (“PSTN”). Unlike the PSTN, which is circuit-switched, the Internet is packet-switched. As such, communications on the Internet is accomplished by transmitting and receiving packets of data. In addition to data, each packet contains a destination address to ensure that it is routed correctly. The format of these packets is defined by the IP. One type of allowable data is encoded, digitized voice, termed voice over IP (VoIP). VoIP is voice that is packetized as defined by the Internet protocol, and communicated over the Internet for telephone-like communication. Individual VoIP packets may travel over different network paths to reach the final destination where the packets are reassembled in correct sequence to reconstruct the voice information.

With the advent of VoIP services, many current proposals suggest that no analog telephone connection to the public switched telephone network be provided at a customer premises. Instead a packet network connection is provided at the customer's premises. For example, iMerge, a solution in IP and TDM transport formats, available from AG Communications of Phoenix, Ariz., transports voice or data from and to a customer's premises via a fiber-to-the-home network or a cable network that interfaces to a managed IP network. The managed IP network is coupled to the public switched telephone network via a gateway, such as an IP to GR-303 gateway. The equipment at the customer's premises, e.g., telephones, connect to the fiber-to-the-home network or cable network via an analog-to-IP gateway with multiple ports that support multiple directory numbers and line terminations. Where the customer's equipment uses a modulated data transmission, for example, a modem, fax or TDD/TTY terminal, the lack of an analog telephone connection from and to the home, requires that the modulated data transmission be digitized (re-digitized) at the analog-to-IP gateway, prior to transmission over the managed IP network. The digitized modulated data transmissions are eventually converted back to a modulated data transmission at a point where the packet network connects to a circuit-switched telephone connection. Unfortunately, the extra digitizing of the modulated transmission at the customer's premises and the subsequent packet transmission and conversion back to a modulated format causes undesirable errors in the modulated transmission that affect the true and attainable data rate and bandwidth for the connection. This is due to delay, clocking mismatches, packet drop outs and the like.

Therefore, a need exists for an improved method and apparatus for supporting modulated transmission where only an IP connection is provided at a customer's premises.

SUMMARY OF THE INVENTION

The need is met and an advance in the art is made by the present invention, which provides a proxy or virtual modem connection to prevent unnecessary encoding and transcoding of a modulated transmission from a customer premises device that directly accesses a packet network.

In accordance with one aspect of the present invention, a method is provided for transmitting a modulated signal over a packet network. The method includes the step of receiving a modulated signal, for example, an analog modem signal that is modulated in conformance with a particular protocol. The modulated signal is demodulated with reference to the protocol to produce a demodulated digital signal. The demodulated digital signal is packetized, that is, organized into a packet. The packet is transmitted over a packet network. The packet is then received and the demodulated digital signal is recovered from the packet. The demodulated digital signal is then modulated in accordance with the particular protocol to produce a virtual modulated signal. The virtual modulated signal is then transmitted over a telephone network.

In another aspect of the invention, prior to the step of receiving the modulated signal, data is received identifying a destination for a data call. Then, a database query is performed with the data identifying the destination to determine a virtual modem location associated with the destination. The packet is sent to the virtual modem location associated with the destination via a packet network. The packet is then received at the virtual modem location associated with the destination and, at that location, converted into the virtual modulated signal that is then transmitted over a telephone network.

In accordance with another aspect of the invention, a proxy modem for use in a packet data communications system is provided. The proxy modem includes a first processor that receives a modulated signal that is modulated in accord with a certain protocol. The first processor demodulates the modulated signal with reference to the certain protocol to produce a demodulated digital signal. The first processor then packetizes the demodulated digital signal into a packet and transmits the packet over a packet network. A second processor then receives the packet and recovers the demodulated digital signal from the packet. The second processor then modulates the demodulated signal in accordance with the certain protocol to produce a virtual modulated signal. The virtual modulated signal is then sent over a telephone network.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a block diagram of a communications system100that provides a proxy modem for voice over Internet protocol telephone services in accordance with the present invention. Communications system100includes a customer premises102. Customer premises102is directly connected to IP network104. Notably, customer premises102does not have a traditional circuit-switched telephony interconnection to the public switched telephone network. Instead, customer premises102has a direct connection to IP network104. The direct connection is preferably a fiber-to-the-home network or cable network. Analog-to-IP gateway120interfaces with IP network104. Inside the customer premises102, analog-to-IP gateway120provides interfaces to a traditional telephone126, a facsimile machine124and a computer122. Computer122actually has two connections to analog-to-IP gateway120. The first connection is through modem128. The second connection is a network connection to a network interface130of computer122. Other connections to analog-to-IP gateway120are contemplated, including a connection to a TDD/TTY terminal.

Analog-to-IP gateway120provides an interface for traditional telephone connections at the customer premises102. In particular, telephone126connects to analog-to-IP gateway120for voice communications. In accordance with traditional voice over IP services, analog voice received from telephone126is digitized and placed in packets to be sent over IP network104. Also, analog-to-IP gateway120has analog phone connections for attaching to fax124and modem128. In accordance with traditional voice over IP services, as discussed above, analog modulated transmissions from fax124and modem128are digitized and placed into packets in a manner similar to the treatment of voice from telephone126. As discussed above, this process introduces undesirable errors in the modulated transmissions. As discussed further below, analog-to-IP gateway120is modified in accordance with the present invention to treat modulated signals, such as signals from fax124and modem128in a different manner to facilitate better data communications. In addition, and in accordance with another aspect of the invention, computer122uses network interface130to emulate a modem such that a signal to be modulated is sent using analog-to-IP gateway120without extra digitizing of the modulated signal to conform to an IP network protocol.

IP network104provides access to and from many other communications systems. In particular, as shown inFIG. 1, IP network104is coupled to Internet106. IP network104is preferably a privately managed IP network. IP network104is coupled to modem pool112. Modem pool112is coupled to the public switched telephone network (PSTN)110. Internet106is coupled to IP-to-PSTN gateway108. Modem pool112converts from an IP network to a modem protocol suitable for the public switched telephone network and vice versa. Similarly, IP-to-PSTN gateway108converts from an IP protocol to a protocol suitable for the public switched telephone network, and vice versa. InFIG. 1, a data center114, such as a data center for a pool of computers, and a fax115are shown connected to PSTN110. Of course, any devices capable of connecting to the public switched telephone network may connect to PSTN110.

As discussed above, analog-to-IP gateway120is modified in accordance with the present invention such that the modulated transmissions received by analog-to-IP gateway120are not unduly digitized in a manner to cause undesirable errors. Also, a network element that converts from an IP protocol to a PSTN protocol is modified in accordance with the invention to modulate previously modulated signals received from analog-to-IP gateway120in accord with a proper protocol. For example, a transmission from fax124to fax115is enhanced over prior art transmissions. Similarly, transmissions between modem128and a data center114are enhanced over prior art transmissions. More specifically, modulated transmissions received by analog-to-IP gateway120from fax124or modem128are not digitized in the manner that voice signals are digitized, as if received from, for example, telephone126. Instead, the modulated transmissions are demodulated in analog-to-IP gateway120according to the protocol used to modulate the signals to thereby produce a demodulated digital signal. It will be appreciated by those skilled in the art that this demodulated signal is more accurate than a digitized version of the modulated signal. The demodulated digital signal is then organized into packets that are transmitted to IP network104. When the packets of the demodulated digital signal reach a network element that will send the communications over a public switched telephone network connection, the demodulated signal is modulated in accordance with the proper protocol and that analog signal is then transmitted over the telephone connection. The network elements shown inFIG. 1that transmit over a public switched telephone connection from an IP connection include modem pool112and IP-to-PSTN gateway108.

FIG. 2is a block diagram partially showing communications system100, including further details of analog-to-IP gateway120and modem pool112. In particular, a block diagram of a proxy modem200ain analog-to-IP gateway120is shown. Similarly, a proxy modem200bin modem pool112is shown. The proxy modems are substantially similar and hence, the same reference numerals are used to designate like parts, except that an alphabet (a or b) following the reference numeral distinguishes whether the reference is associated with analog-to-IP gateway120or modem pool112. Hereinafter, a reference to a reference numeral without the trailing alphabet refers to all occurrences of the designated item. In contrast, the designation to the reference numeral and alphabet refers to the specific instance of that item.

Proxy modems200include a telephone interface206. Telephone interface206provides a connection to a telephony device for the public switched telephone network. The interface supported may vary from a two-line interface to a T1 network interface or any other circuit-switched telephony interface.

Modulated transmissions received by telephone interface206are demodulated by demodulator208. Demodulator208reproduces the signal that was originally modulated by implementing an inverse of the modulation protocol used to modulate the signal. For example, for a modulated communication from fax124, demodulator208aprovides an inverse of the fax protocol to produce a digital demodulated signal representative of the fax transmission.

The digital demodulated signal produced by demodulator208is then organized into packets by packetizer210. The packets from packetizer210are sent over a packet network via a packet network interface212.

After traveling across a packet network, packets of the digital demodulated signal are received as packets by packet network interface212. Depacketizer214organizes the packets to recreate the digital demodulated signal. Modulator216receives the digital demodulated signal and modulates the demodulated digital signal in accordance with the proper protocol and sends the modulated signal over telephone interface206.

By way of example, modem128sends and receives data to data center114via the following procedure. A modulated signal produced by modem128is received by telephone interface206a. Telephone interface206aknows that it is receiving a modulated signal from modem128either because of a port designated on analog-to-IP gateway120for receiving modulated transmissions, or telephone interface206adetects that the signal is modulated via digital signal analysis of the modulated signal itself. Telephone interface206asends the modulated signal to demodulator208a. In accordance with, and in reference to, the modem protocol used to modulate the signal, demodulator208ademodulates the signal to produce a digital demodulated signal. The digital demodulated signal is sent to packetizer210a,which organizes the digital demodulated signal into packets that are forwarded over IP network104via packet network interface212a.The packets travel across IP network104to packet network interface212b.The packets are organized into a digital demodulated signal by depacketizer214b.The digital demodulated signal is then modulated by modulator216bto produce an analog modulated signal that is sent to the public switched telephone network by telephone interface206b.The modulated signal is then routed through the public switched telephone network to data center114. Data from data center114follows an analogous path over PSTN110to telephone network interface206b.This analog modulated signal is then demodulated by demodulator208band organized into packets by packetizer210bprior to being forwarded over IP network104by packet network interface212b.Packet network interface212areceives the packets and re-organizes the packets into a digital demodulated signal using depacketizer214a.The digital demodulated signal is then modulated by modulator216ato produce an analog signal that is sent over telephone interface206ato modem128.

FIG. 3is a flow diagram illustrating the flow of a data call that includes a modulated transmission in accordance with the present invention. In particular,FIG. 3shows modem128, analog-to-IP gateway120, IP network104, modem pool112, and PSTN110. Lines with an arrow, which are designated by reference numerals, are also shown inFIG. 3to illustrate the steps and procedures used to accomplish the data call in accordance with the present invention. An example operation in accordance with the invention is described below with reference toFIG. 3.

First, modem128goes off-hook to initiate the beginning of a call in the traditional manner (300). In response to the off-hook indication, analog-to-IP gateway120returns a dial tone to modem128, if resources are available to initiate the call (302). After receipt of the dial tone, modem128sends digits representative of the number to be called for the data call (304). These procedures represent the traditional method of establishing an analog phone call and apply not only for modem128, but also for phone calls placed using telephone126or fax124.

After analog-to-IP gateway120has the digits representing the number to be called, the analog-to-IP gateway120can proceed to set up the call over the packet network to the public switched telephone network. This requires determining an IP address for the final packet device that directly connects to the public switched telephone network to complete the call. In this example, modem pool112connects the call to the PSTN, and therefore, the IP address of modem pool112is the final packet destination. First, a setup message is sent from analog-to-IP gateway120to modem pool112to initiate communication with the modem pool (306). Modem pool112then sends an acknowledgement message back to analog-to-IP gateway120to indicate that setup is properly established (308). In response to the acknowledgement, analog-to-IP gateway120sends digits for the phone call to modem pool112(310). Upon receipt of the phone number for the final destination, modem pool112sets up the circuit-switched or telephony connection to the destination attached to the public switched telephone network110.

In order to connect to the destination connected to the public switched telephone network110, modem pool112send digits representing the telephone number associated with the destination (312). If the destination is available, then the call is answered (314). When the modem pool112detects that the phone call is answered, modem pool112sends an acknowledgement to analog to IP gateway120(316). The acknowledgement indicates that the phone call has been established with the destination, including a path through a packet network.

Analog-to-IP gateway120forwards the acknowledgement and any data for the connection over to modem128(318). Modem128responds in a manner consistent with answering a traditional analog phone call by returning tones to establish the communication over the call (320).

At this point, a communications path for the data call is established between modem128and the final destination attached to the public switched telephone network110. The path shown via lines320,322,324,326,328,330are representative of the continuous back and forth sending of data between the participants of the data call. Path320is an analog path that includes a modulated transmission. Path322is a packet transmission in accordance with the present invention. Data on path322is formed from a modulated transmission processed by proxy modem200of analog-to-IP gateway120. Path324is a telephony connection that carries a modulated transmission processed by a proxy modem200of modem pool112. Path326carries a modulated transmission over a telephony connection to modem pool112. Path328is a packet connection that, in accordance with the invention, is processed by proxy modem200of modem pool112. Path330is a telephony connection back to modem128. Data on path330is processed by proxy modem200of analog-to-IP gateway120.

In accordance with a preferred option according to the invention, after analog-to-IP gateway120receives the dialed digits for the call (304), analog-to-IP gateway120performs a database look-up, for example, using a service control point (SCP) database390, or the like. The SCP database is accessible via any available network. The SCP database provides a number or identification, typically an IP address, for the destination packet device that makes the connection to the telephone network. Using a database look-up advantageously permits flexible selection of a destination device that connects to the PSTN. Selection may be based on rate, geographical location, time, cost or another parameter.

FIG. 4is a block diagram showing an alternate embodiment of the present invention particularly suited for modulated transmissions originating from a computer. In particular,FIG. 4shows in greater detail, the network connection408between computer122and analog-to-IP gateway120. As discussed further below, in accordance with this aspect of the invention, rather than analog-to-IP gateway120receiving modulated transmissions from computer122, analog-to-IP gateway120receives digital data that is to be modulated over network interface408and then portions of proxy modem200in analog-to-IP gateway120are used to communicate the transmissions. For the return path, modulated transmissions received from a packet network by proxy modem200in analog-to-IP gateway120are not modulated prior to being sent to computer122, but instead are sent as digital data over network connection408to computer122.

Computer122includes a processor402, a memory404and a network interface130. Processor402, memory404and network interface130are coupled together for communication in any known manner. Processor402is any suitable microprocessor, micro-controller, digital signal processor or combination of these. Any network connection and corresponding network interface is employed, for example, Ethernet. Indeed a simpler connection such as a parallel or serial connection, for example, USB or Firewire, may be employed.

Processor402, in conjunction with memory404, executes a stored program that simulates a modem in accordance with the present invention. The modem emulation program communicates with other applications running on computer122to provide an interface consistent with a physical modem and a software driver for the modem. The modem emulation program receives data from other applications that are to be sent as a modulated transmission. Data to be modulated by the emulation program is forwarded via network interface130and network connection408to network interface406of analog-to-IP gateway120.

A companion modem emulation program runs on a processor on analog-to-IP gateway120. This program interfaces with network interface406to receive the data to be modulated from network connection408. Rather than modulate that data, in accordance with the invention, the data to be modulated is forwarded to packetizer210a,where it is organized into packets and forwarded to an IP network via packet network interface212a.The packets are ultimately received by a device that is connected to the public switched telephone network, for example modem pool112. At the device connected to the public switched telephone network, the data is modulated and forwarded over the public switched telephone network. For example, data to be modulated from computer122is received by packet network interface212bof modem pool112. That data is then depacketized by the depacketizer214band modulated by modulator216b.Then the modulated analog data is forwarded over telephone interface206bto public switched telephone network110and ultimately a destination connected to PSTN110, for example, data center114.

Modulated transmissions that are sent to computer122are subjected to an inverse process in accordance with the present invention. In particular, packetized modulated data, such as that output by packet network interface212bof modem pool112, is received by packet network interface212a.That data is then re-organized into digital data by depacketizer214a.That data is then forwarded to network interface130of computer122via network interface406and network connection408. The modem emulation program running on computer122then provides the received data to applications communicating with the modem.

Proxy modems are provided in a communications system in accordance with the invention to accommodate modulated transmissions. Advantageously, unnecessary digitizing and re-digitizing of the modulated transmission is avoided. This facilitates faster more reliable modulated transmissions within an Internet protocol communications system.

Whereas the present invention has been described with respect to specific embodiments thereof, it will be understood that various changes and modifications will be suggested to one skilled in the art and it is intended that the invention encompass such changes and modifications as fall within the scope of the appended claims.