|Title of Invention||
ARRANGEMENT FOR DATA TRANSMISSION UTILIZING THE TELEPHONE NETWORK
|Abstract||For modem connections via telephone lines, modems (MODCh1, MODCh2) which in each case correspond to the terminal modems (MOD1, MOD2) are arranged as closely as possible to the entry point of the subscriber lines in the subscriber line circuits (TSCH1, TSCH2) of the telephone exchanges. Modem communication now only in each case between these pairs.|
Arrangement for data transmission utilizing the
The invention relates to an arrangement for data transmission utilizing the telephone network between modems for data terminal equipment connected to a telephone exchange via analogue telephone subscriber lines.
In a telephone network that is utilized in this manner, the modems (modulator/demodulator) which represent a data transmission facility are arranged as a link for adaptation between telephone paths and data terminal equipment and used for. converting the digital signals supplied by the data terminal equipment into line signals which are advantageous for transmission and which correspond to the electrical conditions of analogue telephone connections, and perform an inverse conversion of such signals into digital signals.
In this context, different types of modulation method such as frequency modulation, differential phase modulation and quadrature amplitude modulation are used (see, for example, Handworterbuch des elektrischen Fernmeldewesens (dictionary of electrical telecommunication) published on commission by the Federal German Ministry for Posts and Telecommunication).
There is a large variety of different types of modem protocols for modem connections, for example those specified in the so-called V Series by the ITU-T (formerly the CCITT).
Figure 1 shows how data transmission was previously handled via the telephone network.
Data signals coming from data terminal equipment, for example a personal computer PCI, are converted into the abovementioned line signals in a modulator Modl and transmitted via subscriber line TL1 which is primarily used for the transmission of voice
signals from and to a telephone terminal Tel, to a telephone exchange LE1. In the subscriber line unit TSCH1, to which the subscriber line is connected, they are subjected to the same treatment as the voice signals, namely band limiting to 300 to 3400 Hz, analogue/digital conversion, companding according to the A-law or the m-law and are finally transmitted via a PCM link PCM of the telephone network SPN, which also includes the exchange LEI, to a destination exchange LE2 of the telephone network SPN to which the other data terminal in the form of personal computer PC2 of the connection considered is connected. In the subscriber line unit TSCH2 of the destination exchange LE2, the data transmitted are subjected to a corresponding inverse conversion, namely an A-law or m-law expansion and a digital/analogue conversion before they are transmitted via the telephone subscriber line TL2 to modem Mod2 from where they reach the data terminal equipment PC2 after conversion into digital signals.
The system parts outside the data terminal equipment which are primarily used for voice signal transmission between telephone terminals such as the terminals Tell and Tel2 shown, and which were mentioned in connection with the data signal transmission described, are accordingly optimized for voice signal transmission and therefore have a restricting effect on the transmission rate and transmission bandwidth of the data transmission. To achieve an increase in the achievable data rates, highly complex modulation methods are used for the digital data which, of course, is associated with corresponding expenditure.
In the known manner of handling data transmission by utilizing the telephone network as described, there is direct communication between the subscribers, that is to say the modems in this case, as in the case of voice signal connections. This requires that the subscribers must "understand one another",
that is to say that the same modem protocol must be used at both terminal modems. When modem protocols are reformulated, this results in the requirement that these must also cover previous modem protocols so that modems already installed can continue to be used as before.
It is then the object of the invention to develop an arrangement for data transmission utilizing the telephone network between modems for data terminal equipment connected to a telephone exchange via analogue telephone subscriber lines to the effect that such modem connections are possible without the abovementioned restrictions.
This object is achieved by means of the features specified in the characterizing clause of Claim 1.
In the arrangement according to the invention, accordingly, a modem which operates in accordance with the same modem protocol as the modem connected to the respective telephone subscriber line at the subscriber end is in each case arranged at the interfaces to telephone subscriber lines affected, that is to say those which establish a connection to the modem of a data terminal equipment. This therefore means that in the case of a data connection between two terminal modems for data terminal equipment, these terminal modems no longer have to communicate directly with one another but in each case only with the modem located in the exchange. The modem protocols used in the case of such a communication and especially the type of coding method used depends only on the properties of the transmission link between terminal modem and exchange. This makes is possible to define modem protocols which cover all previous standards and are additionally capable of transmitting much higher data rates (>>64kbits/s) .
Further embodiments of the invention are characterized in the subclaims.
According to Claim 2, the exchange modems are placed as closely as possible to the interface to the telephone subscriber line. It is thus no longer necessary to pass through all voice-signal-specific equipment in the input area of the exchange which, as indicated, led to restrictions under the previous practice. Thus, for example, the companding and expansion according to the A-law or m-law provided for voice signals can be avoided.
According to Claim 3, the exchange modems are set up for operating optionally in accordance with different modem protocols, in practice in accordance with all hitherto known protocols so that communication with all types of existing terminal modems is easily possible.
According to Claim 4, the exchange modems are integrated into subscriber-individual constructional subscriber line units or subscriber-group-individual subscriber line modules for connection of the telephone subscriber lines.
According to Claim 5, the constructional subscriber line units in this case exhibit, in addition to their connection to the telephone exchange, a connection to a data network, these connections being activated for the data signals to be transmitted between data terminals as an alternative. In this type of constellation, a subscriber equipped with any type of commercially available modem at the terminal equipment can be conducted directly into the data network via the subscriber line of the exchange or its data network connection. This prevents connections to the data network which frequently last for a long period of time, for example Internet applications, from loading the non-subscriber-individual parts of the telephone network beyond the processes of setting up the connection and clearing down the connection.
According to Claim 6, the exchange modems are implemented by using a digital processor system, for
example a signal processor or microprocessor. The respective optional modem protocol characteristic can then be achieved simply by loading the appropriate software or exchanging or regrouping corresponding function blocks.
In the case of the presence of subscriber line modules, it is provided according to Claim 7 to form, for the purpose of implementing the modems, a signal processor pool which comprises fewer signal processors than a subscriber line module comprises subscriber line circuits, in which arrangement the processors can be optionally dynamically allocated to the subscriber line circuits. This results in a structurally compact and inexpensive solution.
According to Claim 8, the modems operate in accordance with the DMT (discrete multitone) method. In this method, the lower transmission frequency range is kept available for analogue voice transmission of the telephony operation which thus can take place at the same time as the data transmission occurring in the higher transmission frequency range.
In the text which follows, the invention will be explained in greater detail by means of an illustrative embodiment and referring to a drawing, in which:
Figure 1 shows the previous relationships, previously discussed, in the case of data transmissions via the telephone network in the form of modem connections.
Figure 2 shows an arrangement for data transmission utilizing facilities of the telephone network according to the invention, assuming the existence of a data network.
Figure .3 shows a subscriber line module equipped in accordance with a special development of the invention.
In Figure 2, parts which are identical to parts shown in Figure 1, are provided with the same reference symbols.
In contrast with the conditions shown in Figure 1, subscriber line units TSCH1 and TSCH2, respectively, of the telephone exchanges LE1 and LE2, to which terminal modems MODI and MOD2, respectively, are connected via subscriber lines TL1 and TL2, respectively, exhibit an exchange modem MODChl and MODCh2 respectively. These modems are arranged as closely as possible to the interface to telephone subscriber line TL1 and TL2, respectively, namely following a facility AFE which represents the analogue section of the interface in which the analogue/digital conversion and, respectively, digital/analogue conversion also take place.
The exchange modems MODChl and MODCh2 are connected to an interface circuit IFDN which leads to a data network access to a data network DN.
The data network can be, for example, the Internet. Thus, an Internet connection will then only occupy central sections of the exchanges LEI and LE2 during the stage of connection set-up and for the entire Internet call only use subscriber-line-individual or subscriber-line-group-individual parts. Modem communication during the course of such a call between PCI and PC2 only needs to occur between modem MODI and modem MODChl, on the one hand, and modem MOD2 and modem MODCh2, on the other hand.
As before, however, it is still possible also to conduct the data communication to its full extent or at least to a greater extent via the telephone network. This may be required if the exchange at the end of the called party of a data connection is not equipped in the manner according to the invention.
Figure 3 shows in greater detail a subscriber line module SLMI:MSFM for subscriber lines TL which are connected to data equipment PC, which is configured in
accordance with a special development of the invention. Such a subscriber line module is assumed to be used for connecting 16 subscriber lines and therefore comprises 16 subscriber circuits TSCHG which essentially contain the analogue section AFE of the line interface, also shown in Figure 2. The digital interface section DFE for the voice signals, which interface is shown in Figure 1 and in which, among other things, the companding and expanding according to the A-law or, respectively, (m-law, and line impedance matching takes place, is in this case provided as a common facility for the 16 subscriber line circuits. The same applies to the IFSPN interface to the PCM line PCM leading to the central section of the exchange.
The companding or, respectively, expanding according to the A-law or, respectively, m-law, and the A/D and, respectively, D/A conversion are all kinds of analogue/digital functions and are in this case allocated to the analogue section AFE of the line interface. This allocation requires the AFE to be activated for switching companding and expanding off or on depending on the requirement.
The modems designated by MODChl and MODCh2, respectively, in Figure 2 are in this case implemented in the form of signal processors DSP which are capable of operating in accordance with all known modem protocols, for which purpose the appropriate software is loaded in each case. If new protocols are produced, it is only necessary to update the software.
In the case shown, the signal processors are not permanently allocated to the individual subscriber circuits TCSH but form a pool which comprises fewer signal processors than the subscriber line module comprises subscriber line circuits TSCHG. They can be allocated dynamically to these subscriber line circuits.
The digital signal processors DSP and the interface IF under the controlling influence of a
control processor IOP which is influenced from a control network CN and which also determines, among other things, whether the data signals processed by one of the signal processors are supplied to the data network via the interface IFDN or to the voice network via the interface IFSPN.
According to a development of the invention, the modems operate in accordance with the DMT (discrete multitone) method. In this method, a number of carrier signals are used for the transmission so that the transmission channel is subdivided into n subchannels. During the modulation of the data, tones of a certain frequency are generated which are combined and sent through the line as "DMT symbol".
In the version according to the invention, the lower transmission frequency range is kept available for analogue voice transmission of the telephony operation and data transmission takes place in the higher transmission frequency range and can occur simultaneously with the telephony operation.
1. Arrangement for data transmission utilizing facilites of the telephone network between modems for data terminal equipment connected to a telephone exchange via analogue telephone subscriber lines, characterized in that in the service area of telephone exchanges (LEI, LE2) a modem (MODChl, MODCh2) which operates in accordance with the same modem protocol as the modem (MODI, MOD2) connected to the telephone subscriber line (TL1, TL2) at the subscriber end is in each case arranged at the interfaces to telephone
subscriber lines (TL1, TL2) affected.
as claimed in
2. Arrangement accORDING—to -Claim 1, echracterized in that the exchange modems (MODChl, MODCh2) are placed
as closely as possible to the interface to the telephone subscriber line (TL1, TL2) so that data signals to be transmitted on this line have to pass through the fewest possible voice-signal-specific facilities and accordingly modem protocols can be used which allow high-bit-rate data transmission.
3. Arrangement according to Claim 1 or 2,
as claimed in
characterized in that the exchange modems (MODChl, MODCh2) are set up for operating optionally in accordance with different types of modem protocols.
4 . Arrangement according—in one of the preceding
as claimed in claims, characterized—in that, the exchange modems
(MODChl, MODCh2) are integrated into subscriber-individual constructional subscriber line units (TSCH) or subscriber-group-individual subscriber
line modules (SLMI)
as claimed in
5. Arrangement ACOORDING—to Claim 4, -charactorizod
in that the subscriber line unit (TSCH) or,
respectively, the subscriber line modules (SLMI:MSFM) exhibit, in addition to their connection to the telephone exchange (IFSPN), a connection (IFDN) . to a data network, in which arrangement these connections
can be activated for the data signals to be transmitted between data terminals (PC1, PC2) as an alternative.
6. Arrangement as claimed In one of the preceding claims, wherein the exchange modems are implemented by using a digital processor system and that the respective modem protocol characteristic is achieved by loading the appropriate software or by exchanging or connecting other function blocks.
7. Arrangement as claimed in claim 5, if subscriber line modules are present, wherein the signal processors (DSP) for the purpose of implementing the modems from a pool which comprises fewer signal processors than a subscriber line module (SLMI:MSFM) comprises subscriber line circuits (TSCHG), In which arrangment the signal processors can be optionally dynamically allocated to the subscriber line circuits.
8. Arrangement as claimed In one of the preceding claims, wherein the modems (MODI, MODCh1; MOD2, MODCh2) operate in
accordance with the DMT (discrete muititone) method and that the lower transmission frequency range is kept available for analogue voice transmission of the telephony operation which thus can take place at the same time as the data transmission occurtng In he higher transmission frequency range.
For modem connections via telephone lines, modems (MODCh1, MODCh2) which in each case correspond to the terminal modems (MOD1, MOD2) are arranged as closely as possible to the entry point of the subscriber lines in the subscriber line circuits (TSCH1, TSCH2) of the telephone exchanges. Modem communication now only in each case between these pairs.
|Indian Patent Application Number||866/CAL/1998|
|PG Journal Number||41/2007|
|Date of Filing||13-May-1998|
|Name of Patentee||SIEMENS AKTIENGESELLSCHAFT|
|Applicant Address||WITTELSBACHERPLATZ 2, 80333 MUNCHEN, GERMANY|
|PCT International Classification Number||H 04 M 3/42|
|PCT International Application Number||N/A|
|PCT International Filing date|