Abstract:
A data communication method is disclosed that enables the simultaneous transmission of voice and data over a single Public Switched Telephone Network (PSTN) line. A party to a data communication connection (hereinafter “the client”) can accept and originate voice calls from and to anywhere on the PSTN while maintaining the data communication with the original destination (hereinafter “the server”). This is accomplished by adding additional functionality at the location of the server and by utilization of existing “Call Forwarding” and “Caller-Id” technology. The server manages voice calls to and from the client while the client and server are engaged in the data communication connection.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to data communications equipment and, more particularly, to the simultaneous transmission of voice and data over a single Public Switched Telephone Network (PSTN) line. 
     Simultaneous Voice and Data (SVD) technology permits simultaneous voice and data communications between a pair of users within the bandwidth provided by a single “plain old telephone service” (POTS) line. In operation, a high speed voice-band modem carries data in the usual manner. When either user wishes to communicate to the other by voice, a signal is sent via a standard V 70  Protocol message. Once the other user acknowledges the message, a voice channel is opened and a portion of the total modem rate (e.g., 8 KB/S) is allocated for carrying the digitally compressed voice data. As a result, the two parties can simultaneously communicate by both voice and data. To be able to convert between analog data and compressed digital voice data, and to handle the signaling protocol, both parties must have SVD capability. The basic operation of an SVD modem is described in U.S. Pat. No. 5,448,555 to Bremer et al. 
     Technology has been developed which enables an SVD user to have a voice conversation and a data connection at the same time, but with different parties. Under this prior art technique, a central office (e.g. an inter-exchange carrier such as AT&amp;T) of a PSTN provides a “local loop” SVD service in which both voice and data calls with the user co-exist over a POTS line, and the voice and data portions of these calls are routed to separate parties. To accomplish this result, the central office must include a modem pool that has both SVD-capable modems and standard (e.g., CCITT V.32 compatible) modems. A user with an SVD modem establishes an SVD link with the SVD modem of the central office. The SVD modem of the central office then separates the voice and data portions of the voice-band signal received from the local loop for separate transmission by the central office to different parties. The voice portion of the SVD signal receives standard voice-call handling from the central office for transmission to the party that is a part of the voice-call. The data portion of the SVD signal is routed through the standard modem of the central office for transmission to the party that is a part of the data-call. As a result, only the SVD user is required to have an SVD-capable modem, yet the SVD user can have both a voice connection and a data connection over a single “tip/ring” type telephone line. This kind of arrangement is described in U.S. Pat. No. 5,513,251 to Rochkind et al. and U.S. Pat. No. 5,625,677 to Feiertag et al., and in published European Patent Application No. EP 674,420 which cites U.S. patent application Ser. No. 216,373 as a priority application. 
     In the above described call-handling system, the central office of the PSTN must be equipped with the additional modems to be able to detect the type of incoming call (modem/voice or SVD) for a particular telephone number and process that call properly. This is very expensive because all of the central offices that want to provide this functionality must be upgraded to include SVD modems and standard data modems. If the central office to which User  1  is connected is not equipped with the specialized modems, User  1  cannot carry on this simultaneous voice and data communication with different parties. Further, the central office can accomplish the simultaneous voice/data communication only because it has the capability of establishing a local loop between the central office and the caller with the SVD modem. 
     SUMMARY OF THE INVENTION 
     Permits a first party (hereinafter “the client”) to a data communication connection with a second party (hereinafter “the server”) on a regular voice-band PSTN connection to accept and originate voice calls from and to anywhere on the PSTN while maintaining the data communication with the server. This is accomplished by adding additional functionality at the location of the server and by utilization of existing “Call Forwarding” and “Caller-Id” technology. 
     In one embodiment, the call handling is accomplished by the steps of establishing a SVD data connection between a first party and a second party; and establishing a voice call between the first party and a third party; wherein the voice call and the data call co-exist on a regular voice-band PSTN line between a switching system of said second party and terminal equipment of said first party, and the telephone number of said second party and the telephone number of said third party are different. 
     In a preferred embodiment all calls that are incoming to the first party are automatically forwarded to the second party; and the second party manages the connection of the voice-call between said first party and said third party. Upon initiation of a voice-call from said third party to said first party, said second party receives said incoming call from said third party; determines the identity of the calling party (said third party) and said party being called (said first party); and establishes a connection between said third party and said first party on the same regular voice-band PSTN connection that is being used for said data-call between said first party and said second party. 
     In a more preferred form, the second party comprises an internet service provider or a server independent of the PSTN. 
     In another embodiment, the additional step of establishing voice calls between a plurality of parties located at the same location as said first party and an equal number of parties located elsewhere is performed. For the duration of the SVD data connection, all calls that are incoming to the first party are forwarded to the second party, and the second party manages all incoming/outgoing calls to/from the first party by forwarding incoming calls to the first party over the PSTN line on which the SVD data connection is established and by forwarding all outgoing calls of the first party to a destination party over the PSTN line. 
     In an alternative embodiment, call handling is accomplished by establishing a data connection between a first party and a second party over a regular voice-band PSTN line; and for the duration of the data connection, all calls that are incoming to the first party are forwarded to the second party, and the second party manages all incoming/outgoing calls to/from the first party by forwarding all of the incoming calls to the first party to an incoming call processor. 
     A hardware embodiment of the present invention comprises a server for routing voice/data calls to/from a first SVD modem via a PSTN, the server comprising a second SVD modem, coupled to the PSTN, for receiving a transmission from the first SVD modem, the transmission having a voice channel and a data channel; a first caller identification circuit, coupled to the second SVD modem and to said PSTN, for identifying a party being called from the first SVD modem and a party calling to the first SVD modem; a second caller identification circuit, coupled to the PSTN; and a controller, coupled to the second caller identification circuit and the second SVD modem, for controlling the routing of voice/data calls to/from the first SVD modem via the PSTN based on the identification made by the first and second caller identification circuits. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a communication system in accordance with the present invention. 
     FIG. 2 is a block diagram of the communication system of the present invention showing a multi-user connection. 
     FIG. 3 is a block diagram of the communication system of the present invention in which non-SVD modems are utilized. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a client, e.g., User  1 , is coupled to a PSTN  700  via SVD modem  600 . PSTN  700  may comprise a series of separate but interconnected central offices  702 ,  704 ,  706  and  708  as shown. User  1  has a digital communication device, e.g., a terminal  10  and a voice-band audio communication device, e.g., telephone  20 , each of which are connected to the SVD modem  600 . A server, e.g., internet service provider (ISP)  800  provides an internet connection (data communication) to all of its subscribers, including User  1 . As a service to its subscribers, ISP  800  uses an SVD modem  802  to connect to the PSTN  700 . Thus, in a known manner, User  1  can conduct data communications and voice communications with the ISP  800 . It should be understood that in actual application ISP  800  would be equipped with multiple SVD modems to enable servicing of multiple subscribers; for simplification of explanation, only a single SVD modem  802  is discussed herein. 
     In accordance with the present invention, to enable User  1  to send or receive voice communications with parties other than the ISP  800  while maintaining a data connection with the ISP  800 , “Caller-Id” and “Call Forwarding”, both standard features provided by all central offices associated with the PSTN  700 , are utilized. Specifically, User  1  must subscribe to Call Forwarding and have all incoming calls forwarded to the ISP  800 , at least when User  1  wishes to have the ability to conduct simultaneous voice and data communication. Further, the ISP  800  must subscribe to Caller-Id. By subscribing to Caller-Id, the ISP  800  will receive information about a calling party as well as the party being called by the calling party. Conventional Caller-Id detection equipment  804  is coupled to a switching processor  806  and also to SVD modem  802 . Although shown as a separate block, the Caller-ID detection equipment  804  can be included with SVD modem  802  as a single unit. 
     Switching processor  806  provides several important switching functions and can be implemented using software in a conventional manner. For example, using the information detected by the Caller-Id detection equipment  804 , the switching processor  806  can instruct SVD modem  802  to signal a ring request to the appropriate destination for an incoming call. When the user at the destination receives the ring request and decides to open the voice channel by lifting the receiver, this is detected by the switching processor  806  and it routes the incoming voice signal to the opened voice channel. 
     The operation of this system is now described. First, assume that there is a data connection between User  1  and ISP  800 . In a first scenario, User  2  dials the telephone number of User  1  via telephone  22 . On the PSTN  700 , the central office associated with User  2  receives the call request (shown pictorially as a connection between telephone  22  and central office  702 ). Since User  1  has all incoming calls forwarded to ISP  800 , central office  702  forwards the call to central office  704  associated with the ISP  800  (shown pictorially as a connection between central office  702  and central office  704 ) after being “advised” of the call forwarding status by central office  708 . This incoming call is detected by the ISP  800  and the Caller-Id equipment  804  identifies the party calling (User  2 ) and the party being called (User  1 ). After making the identification, the ISP  800  sends a “voice channel open” request to User  1  via switching processor  806 . The “voice channel open” request is a message that is sent from SVD modem  802  to SVD modem  600  using V 70  protocol. Upon reception of this message, SVD modem  600  simulates a ring to User  1 . 
     User  1  accepts the “voice channel open” request by lifting the hand-set of telephone  20 . Upon receiving such acceptance, the switching processor  806  connects User  2  to User  1  via central office  706  and central office  708 . Thus, the SVD modem of ISP  800  allocates a portion (e.g., 8 KB) of the data connection bandwidth to the voice-call between User  2  and User  1 , while the remaining bandwidth (e.g., 16 KB) remains in use for the on-going data connection between the ISP  800  and User  1 . As is well known, the incoming voice signal from User  2 , which is analog, is converted to a digital signal by a conventional A/D converter or by appropriate A/D conversion circuitry included in SVD modem  802  before being transmitted to SVD modem  600 . The signal is then converted back to analog via conventional D/A conversion circuitry. 
     In a second scenario, User  1 , while connected to the ISP  800  via a data connection, desires to place a telephone call to another party, for example, User  2 . To initiate the call, User  1  lifts the handset of telephone  20 , thereby sending a V 70  “voice channel open” request to the ISP  800 . The ISP  800  accepts the request and establishes the voice channel with User  1 . User  1  is then prompted to dial the outgoing call number (the telephone number of User  2 ) and, if required by the ISP  800 , a password to authorize this service. The ISP  800  detects, from the dual tone multi-frequency (DTMF) tones corresponding to the numbers dialed by User  1 , the information regarding the calling party (User  1 ) and the party being called (User  2 ) using the Caller-Id technology. Upon receipt of this information, the ISP  800  then routes the call to the party being dialed, in this case, User  2 , via the various central offices as discussed above. In effect, the ISP  800  receives the attempt by User  1  to call User  2  and completes the connection by dialing User  2 . As with the first scenario, a portion of the data connection is allocated to handle the voice call. 
     The present invention also has application in a multi-user SVD connection environment. Referring to FIG. 2, a multi-user SVD connection according to the present invention is shown. In this scenario, User  1 A, User  1 B, and User  1 C are located in a common location, e.g., the same office. User  1 A is connected to a data line e.g., the internet, via terminal  10 A, SVD modem  600 A, PSTN  700 A and SVD modem  802 A provided by the internet service provider. User  1 B and User  1 C have telephones  20 B and  20 C respectively, which enable them to send or receive voice data over the PSTN  700 A. User  2 A and User  2 B are external users and are essentially equivalent to User  2  shown in FIG.  1 . 
     User  1 A connects to the internet in the same manner described with respect to FIG.  1 . For simplicity of explanation, the details of the various central offices that may comprise PSTN  700 A of FIG. 2 are not shown; however, the operation and structure of PSTN  700 A are essentially identical to PSTN  700  shown in FIG.  1 . If User  2 A initiates a telephone call to User  1 B, the central office associated with User  2 A receives the call request and forwards the call to the central office associated with the ISP  800 A, since User  1 B has forwarded incoming calls to ISP  800 A using Call-Forwarding technology. This incoming call is detected by the ISP  800 A and the Caller-Id equipment  804 A identifies the party calling and the party being called. After making the identification, the ISP  800 A sends a “voice channel open” request to User  1 B via switching processor  806 A. User  1 B accepts the “voice channel open” request by lifting the handset of telephone  20 B. Upon receiving such acceptance, the switching processor  806 A connects User  2 A to User  1 B. While this is occurring, User IC can make an outgoing call to User  2 B. To initiate this call, User IC lifts the handset of telephone  20 C and opens the voice channel to the ISP  800 A. User  1 C then dials the outgoing call number (telephone number of User  2 B), and, if required by the ISP  800 A, a password to authorize this service. The ISP  800 A detects the information regarding the calling party and the party being called using the Caller-Id technology. Upon receipt of this information, the ISP  800 A and switching processor  806 A then routes the call to the party being dialed, in this case, User  2 B. 
     The number of users that can simultaneously operate in the above manner depends only on the bandwidth available for the connection. Each voice channel takes some bandwidth away from the data connection. For example, if it is assumed that a connection rate of X Kbps exists, if three voice channels of Y Kbps are opened simultaneously, the data throughput will go down by a factor of X−3Y. 
     The above description describes the immediate connection of an incoming call to a user while that user is connected in a data connection (e.g., connected to the internet). However, situations may arise when the user connected to the data connection may wish to defer incoming calls (i.e, have them answered by voice-mail or other answering means) and/or receive an incoming facsimile transmission. Further, if SVD modems are not available, the user may, by necessity, have to defer incoming calls or fax transmissions. As shown in FIG. 3, the present invention can accomplish this without the need for an SVD connection. In FIG. 3, assume that User  1 AA is connected to the internet service provided by ISP  800 B via a standard data modem  600 B and PSTN  700 B. While connected to the internet, User  1 AA has incoming telephone calls forwarded to ISP  800 B using Call-Forwarding technology. 
     If User  2 AA sends a fax to User  1 AA by dialing User  1 AA&#39;s telephone number, the incoming call is detected by Caller-Id equipment  804 B at ISP  800 B and the fax is received by ISP  800 B and stored in a conventional manner (hard copy, in computer memory, etc) by incoming call processor  808 B. User  1 AA can access this fax via the internet or by other means provided by ISP  800 B. 
     If the incoming call from User  2 AA to User  1 AA is a voice call, the call is forwarded to ISP  800 B where it is stored via voice-mail, answering machine or other call storing device by incoming call processor  808 B, so that the message is recorded. User  1 AA can then access the message by placing an ordinary telephone call to ISP  800 B. 
     While there has been described herein the principles of the invention, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation to the scope of the invention. Accordingly, it is intended by the appended claims, to cover all modifications of the invention which fall within the true spirit and scope of the invention.