Multiplex communications – Wide area network – Packet switching
Patent
1983-10-13
1985-08-20
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370 84, H04J 316
Patent
active
045368724
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a telecommunication system having telecommunication exchanges, wherein digital information is transmitting between a plurality of exchanges, different transmission rates.
BACKGROUND ART
It is already known to utilize digital transmission channels, intended for example for telephony and operating with pulse code modulation, for transmitting data information, not only if the bit rate in the data information consists of pure submulitples of the PCM channel, i.e. 64 kbits/s, but also for the data rates standardized by CCITT. Such a modulation will be apparent from the Swedish Pat. No. 376 137, describing an example of the transmission of data information at 2.4 kbits/s on a standard 64 kbits/s voice transmission channel.
DISCLOSURE OF INVENTION
These known arrangements do not, however, solve the problem of being able to transmit desired arbitrary standard data rates without considerable alteration in terminal equipment, while at the same time being able to use the same exchange for setting up speech connections as well as for setting up the data channels with different data transmission rates. Furthermore, they do not enable transmission over the same line of several data flows having different-speeds, nor synchronous and asynchronous data flow mixed with each other.
The basic concept of the invention is that each of the transmitting terminal equipments produces a data format corresponding the intended data rate, this format being forwarded by the exchange without the latter even having knowledge of whether data signals or voice signals are passing through a set-up connection.
The invention is characterized as will be seen from the claim.
DESCRIPTION OF FIGURES
The invention will be described in detail below, with reference to the appended drawing, on which
FIG. 1 illustrates a telecommunication system in accordance with the invention,
FIG. 2 illustrates the transmitter part of a terminal equipment,
FIG. 3 illustrates the receiver part of a terminal equipment, and
FIGS. 4a, 4b illustrates examples of different formats used in transmitting at different data rates.
PREFERRED EMBODIMENT
FIG. 1 schematically illustrates a telecommunication system, in accordance with the invention, represented by two data terminal equipments 11a and 11b connected to an exchange 13, intended for setting up digital voice connections between two telephone extensions, e.g. 12a, 12b. The exchange is a conventional digital exchange forwarding telephone calls in accordance with the PCM principle over 64 kbits/s channels between 30 extensions, for example. Such an exchange is well known, and is described in the Swedish Pat. No. 351 541, for example, and therefore it will not be described any further here.
The data terminal equipment includes the conventional components, the terminal 14, an interface adjusting circuit 15 and a transmitter-receiver circuit 16, and a data format-producing circuit 17 in accordance with the invention being connected between circuits 15 and 16. In its transmitter part S, the data format-producing circuit 17 converts the data flow coming from the data terminal to a-format which can be transmitted with the aid of the available 64 kbits/s channel, and in its receiver part M it can restore the original data flow.
The basic inventive concept is that the data flow is subdivided into binary words of given length which are then transmitted at the bit rate of the PCM channel but with the number per time unit made necessary by the data rate. A bit rate of 64 kbits/s enables, for example, a CCITT standard data transmission rate of 48 kbits/s, further bit information being transmitted for synchronization and interface information, as will be described later on. If there is a 16 kbits/s channel available in addition to the 64 kbits/s channel over the line, a higher data rate (56 kbits/s) than the one mentioned above can be transmitted, however.
FIG. 4a illustrates how a frame for transmission of a 48 kbits/s data flow is built up. The frame is subdivided into a fr
REFERENCES:
patent: 3796835 (1974-03-01), Closs et al.
patent: 4392234 (1983-07-01), Maruta
patent: 4471480 (1984-09-01), Haussmann et al.
Olms Douglas W.
Rokoff Kenneth I.
Telefonaktiebolaget LM Ericsson
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