Abstract:
A data coding device for coding data, to be transmitted as part of data communication, to signals of a first frequency range, not used for voice communication with a first set of performance features, and a conversion device are provided. The conversion device has an interface for connecting a voice terminal having a second set of performace features and for transmission of data coded to signals of a second frequency range that are to be transmitted with the second set of performance features as part of voice communication. The conversion device also has a coding means for recording signals of the second frequency range to signals of a third frequency range that is located outside the first frequency range. Furthermore, a frequency-separating filter for feeding signals of the first and third frequency range into the subscriber line is provided.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is based on and hereby claims priority to German Application No. 102 40 651.0, the contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   Subscriber lines of public or private communication networks provided for voice communication are increasingly being used also for data communication. Known examples of these are the transmission technologies summarized under the code xDSL (x Digital Subscriber Line), that permit very high data transmission rates. Widespread xDSL technologies are, for example, ADSL (Asynchronous Digital Subscriber Line), HDSL (High Bit Rate Digital Subscriber Line), VHDSL (Very High Bit Rate Digital Subscriber Line), VADSL (Very High Bit Rate Asymmetrical Digital Subscriber Line) or SDSL (Symmetric Digital Subscriber Line). 
   With the ADSL-Over-ISDN technologies, as they are known, that are widespread in public communication networks, a frequency range of 162-1102 kHz that can still be physically transmitted via the subscriber line is used for data transmission, in addition to a 0-120 kHz frequency range for an ISDN basic access reserved for voice communication. Because the given frequency ranges are disjunctive, voice and data can be transmitted independently and parallel to each other via a common subscriber line. For this purpose, voice terminals and data terminals are coupled via a frequency-separating filter, often known as a splitter, to the common subscriber line. A particular voice terminal is in this case connected via a S 0  or a U K0  interface to the splitter. 
   Because, however, the ADSL-Over-ISDN technology is essentially designed for public communication networks and their subscriber lines and voice terminals, the set of performance features for voice terminals is substantially limited. 
   SUMMARY OF THE INVENTION 
   One possible object of this invention is to provide a system for voice and data communication via a common subscriber line, that, compared to the ADSL-Over-ISDN technology enables the set of performance features that is available for voice terminals to be expanded. 
   For voice and data communication via a common subscriber line, a data coding device is provided for coding data to be transmitted as part of data communication into signals of a first frequency range not used for voice communication with a first set of performance features, and also a conversion device is provided. The conversion device has an interface for connecting a voice terminal with a second set of performance features and for transmission of data coded as signals of a second frequency range that are to be transmitted in the course of voice communications with the second set of performance features. The conversion device also has a coding device for recoding the signals of the second frequency range into signals of a third frequency range outside the first frequency range. Furthermore, a frequency-separating filter is provided for feeding the signals of the first and third frequency range into the subscriber line. 
   A possible advantage is that standard xDSL technology can also be used in private communication networks with a second set of performance features expanded compared to public networks. Suitable voice terminals with expanded set of performance features usually have a connecting interface the signal frequency range of which overlaps with the first frequency range used for data transmission. With the system, the signals transmitted via this interface are converted to signals of a third frequency range outside the first frequency range and can thus be transmitted jointly with the signals used for data communication via the subscriber line without mutual interference. 
   In this way, an expanded set of performance features of modern private exchange equipment can also be used in the context of standard xDSL technologies designed for public communication networks. 
   A further possible advantage is that the existing voice terminals and existing xDSL assemblies can be used for this purpose. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  is a communication system for voice and data communication via a common subscriber line. 
       FIG. 2  is a frequency diagram to indicate the frequency ranges used for voice and data communication. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     FIG. 1  is a schematic illustration of a communication system for voice and data communication via a common subscriber line TL. The subscriber line TL is preferably a copper twin-wire cable such as is frequently used for connecting subscriber terminals to public communication networks. The communication system has a private communication network PKN shown by a dotted line, a public communication network OKN, e.g. a public telephone network, and a wide area network WAN based on an internet protocol, such as the Internet. 
   Compared with the set of performance features, referred to in the following as a first set of performance features, available in the public communication network OKN, the private communication network PKN has an expanded set of performance features, referred to in the following as a second set of performance features. 
   The private communication network PKN in the present exemplary embodiment has, as communication equipment, a voice terminal EG for voice communication supporting the second set of performance features, exchange equipment VE supporting the second set of performance features and a personal computer PC for data transmission. The voice terminal EG has a U P0/E  interface through which it is connected to a converter device DA. In addition to the U P0/E  interface the conversion device DA has a U2B1Q interface and a coding device KM for converting the protocol and for signal recoding between the U P0/E  and U2B1Q interface. The conversion device DA is connected to a frequency-separating filter SP 1  via the U2B1Q interface. In this exemplary embodiment, the frequency-separating filter SP 1  is a standard ADSL frequency-separating filter, called a splitter. 
   The personal computer PC is connected to the frequency-separating filter SP 1  by an ADSL modem AM that acts as a data encoder and data decoder. 
   The frequency separating filter SP 1  is connected via the subscriber line TL to a main distributor MDF (MDF: Main Distribution Frame) of the private communication network PKN. A further frequency-separating filter SP 2 , in the form of an ADSL splitter, is coupled to the main distributor MDF. The frequency-separating filter SP 2  is connected via a U2B1Q interface to the exchange equipment VE. If the exchange equipment VE does not have a U2B1Q interface, a further conversion device (not illustrated) for protocol conversion can be connected between the exchange equipment VE and the frequency-separating filter SP 2 . 
   The frequency-separating filter SP 2  is also connected to a DSL multiplexer DSLAM (Digital Subscriber Line Access Multiplexer), to which the public communication network OKN and the wide area network WAN are also connected. The DSL multiplexer DSLAM serves to combine several ADSL lines and also for connection to forwarding data transmission equipment, such as an ATM switch (ATM: Asynchronous Transfer Mode). In the present exemplary embodiment, the DSL multiplexer DSLAM combines ADSL lines from the private communication network PKN and the public communication network OKN and forwards the data transported through these into the wide area network WAN. 
   In the following, let us assume data transmission between the personal computer PC and wide area network WAN and also a voice connection between the terminal EG and the exchange equipment VE, with the voice connection and the data transmission being jointly carried on the subscriber line TL. 
   As part of the data transmission, data DD, preferably in the form of data packets based on the Internet protocol, is transmitted from the personal computer PC to the ADSL modem AM. This codes the data DD into ADSL signals S 1  that are forwarded to the frequency-separating filter SP 1 . The ADSL signals S 1  are transmitted in a first frequency range FB 1  of 162 kHz to 1102 kHz provided for ADSL data transmission. 
   The frequency diagram shown in  FIG. 2  shows the first frequency range FB 1  reserved for ADSL data transmission, in relation to the other frequency ranges relevant for this exemplary embodiment. As  FIG. 2  shows, the first frequency range FB 1  reserves (excludes) that frequency range FB 0  that in public communication networks is reserved for ISDN connections with the first set of performance features that is normal in that network. In the case of ISDN connections via a U k0  line interface with 4B3T coding, this is, for example, the 0-120 kHz frequency range. Otherwise, the first frequency range FB 1  would largely exhaust the transmission bandwidth physically available for average subscriber lines. This type of ADSL data transmission is frequently called ADSL-Over-ISDN. Correspondingly, standard equipment preferably designed for ADSL-Over-ISDN is to be used as the ADSL modem AM and the frequency-separating filter SP 1 . 
   As part of the voice connection between the terminal EG and exchange equipment VE using the second set of performance features, voice communication data SD is communicated from the terminal EG to the conversion device DA. The voice communication data SD usually includes both pure voice data and also signaling information. 
   The voice communication data SD is transmitted in the form of electrical signals S 2  via the U p0/E  interface. The signals S 2 , as shown in  FIG. 2 , occupy a second frequency range FB 2  of 0-384 kHz that overlaps with the first frequency range FB 1 . The second frequency range FB 2  is broader than the frequency range FB 0  normally reserved for ISDN voice communication in public communication networks, because the expanded second set of performance features of the private communication network PKN requires higher data transmission rates, e.g. for voice and signaling data, than a public communication network. 
   The signals S 2  transmitted to the conversion device DA are recoded by the coding device KM into electrical signals S 3  with the information being retained. The signals S 3  occupy a third frequency range FB 3  that is narrower than the second frequency range FB 2 . In the example given here, the signals S 3  have a 2B1Q coding with a signal frequency range of 0-80 kHz as a third frequency range FB 3 . The 2B1Q coding requires a lower separating bandwidth than the coding of the signals S 2  for the same data transmission range.  FIG. 2  shows the third frequency range FB 3  occupied by signals S 3  compared to the other aforementioned frequency ranges FB 1 , FB 2  and FB 0 . 
   Due to the narrowing of the bandwidth by the conversion device DA, the third frequency range FB 3  is completely below the first frequency range FB 1  reserved for ADSL data transmission and thus does not overlap with the first frequency range FB 1 . 
   The signals S 3  coding the voice communication data SD are transmitted from the conversion device DA via the interface U2B1Q provided for the 2B1Q coding to the frequency-separating filter SP 1 . The frequency-separating filter SB 1  feeds the signals S 3  of the third frequency range FB 3  received from the conversion device DA, and also the signals S 1  of the first frequency range FB 1  received from the ADSL modem AM, into the subscriber line TL. Because the first and third frequency ranges do not overlap, the signals S 1  and S 3  or the data DD and SD transmitted by them, can be transmitted to the frequency separating filter SP 2  in parallel and without mutual interference via the subscriber line TL and the main distributor MDF. 
   The frequency-separating filter SP 2  separates the first and third frequency ranges again from each other and correspondingly transmits signals S 3  coding the voice communication data SD to the exchange equipment VE and signals S 1  coding the data DD to the DSM multiplexer DSLAM. Finally, the voice communication data SD is forwarded from the exchange equipment VE, and the data DD from the DSL multiplexer DSLAM, to the wide area network WAN. 
   For reasons of clarity, only one direction of transmission, i.e. from terminal EG in the direction of the exchange equipment VE or from the personal computer PC in the direction of the wide area network WAN, was considered here. The examples here can, however, be used in a similar manner for voice or data transmission in the reverse direction, i.e. from the exchange equipment VE to terminal EG or from the wide area network WAN to the personal computer PC. In this case, the frequency-separating filter SP 2  feeds signals S 3  of the third frequency range FB 3  originating from the exchange equipment VE, and signals S 1  of the first frequency range FB 1  originating from the DSL multiplexer DSLAM, into the subscriber line TL. The fed-in signals S 1  and S 3  are then separated again by the frequency-separating filter SP 1 , with signals S 1  being communicated to the ADSL modem AM and signals S 3  being sent to the conversion device DA. Whereas the ADSL modem AM extracts the data DD transported in signals S 1  and transmits it to the person computer PC, the coding device KM recodes the signal S 3  into signals S 2  of the second frequency range FB 2 . Signals S 2  containing the voice communication data SD are finally transmitted from the conversion device DA via the U p0/E  interface to the terminal EG. 
   Further variants of this exemplary embodiment can be realized in that the Up0/E interface is replaced by a general Up0 interface and/or the U2B1Q interface by the Uk 0  interface and/or the ADSL technology by a different xDSL technology. 
   The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.