Multiplex communications – Wide area network – Packet switching
Patent
1987-08-10
1989-07-11
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370 86, 3701101, H04J 302
Patent
active
048478334
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a data transmission system which has an improved data format.
2. Description of the Prior Art
Such a system is known in the form of what is referred to as the ISDN-S.sub.O or S/T interface for the ISDN base terminal of an integrated services digital telecommunications network (Fernmeldepraxis, No. 19/20, 1985, pp. 759-762).
Data transmission systems which utilize bit rates of less than about 200 kbit/s are known in the prior art. The subscriber-line technology in the integrated services digital network is divided into a first area of switching to the subscriber, and into a second area of the installation at the subscriber. A network termination unit NT with a U-interface on the network switching side and a S/T-interface on the subscriber's side, installed at the subscriber, serves as a tie between the two areas. A connection between the network termination unit NT and up to eight terminal devices of the same kind or of a different kind occurs via two pairs of a S-bus. The transmission at the S/T-interface occurs with a bit rate of 192 kbit/s.
SUMMARY OF THE INVENTION
The object of the invention is to expand such a system such that it is employable up to bit rates of 140 Mbit/s upon retention of its performance features, particularly of the D-channel access control which is yet to be set forth.
FIG. 1 illustrates the stated object. The passive bus comprising, for example, eight terminal equipment receptacle sockets and the network terminating unit (NT) as interface to the ISDN which is merely schematically shown in FIG. 1 is to be expanded and re-designed such by the invention that it can process bit rates of about 140 Mbit/s instead of bit rates under 200 kbit/s, i.e. can process, a data rate which is higher by about 700 times. In addition to the D-channel access control and the line lengths for the bus and feeders which are possible in the narrow-band execution, uniform terminal equipment receptacle sockets are also to be provided both for the previous ISDN narrow-band services as well as for the newly added broad-band services. The various, possible connections are illustrated in FIG. 1, namely: narrow-band services (TE SBA) which are to be connected via a special adaptor.
A number of problems caused by the significantly higher bit rate which do not occur in the previous interfaces derive in order to achieve a rated condition shown in FIG. 1. The properties of the known S.sub.O interface shall be discussed in brief below.
Two independent, transparent B-channels (useful channels) each having a rate of 64 kbit/s according to CCITT recommendation I.412 and one D-channel (signaling channel) having a rate of 16 kbit/s are made available in both directions via the S.sub.O interface.
The said channels and further functions are combined into a digital multiplex signal.
The multiplex frame is 48 bits long and lasts 250 .mu.s. A plurality of terminal equipment can simultaneously access the D-channel, whereas every D-channel can be occupied by only one terminal equipment. A procedure was selected for the access onto the D-channel which assures that a terminal equipment can always successfully transmit its information (D-channel access control) even given simultaneous access of two or more terminal equipment to the D-channel. When no information is to be transmitted in the D-channel, continuous status binary 1 is transmitted (quiescent condition). A D-echo channel having 16 kbit/s from the network terminating unit in the direction toward the terminal equipment is used for the D-channel access control. Upon receipt of a bit from the terminal equipment on the D-channel, the network terminating unit should reflect this condition with the next D-echo channel bit to the terminal equipment. Every terminal equipment in the active condition should observe the D-echo channel. It may only access the D-channel when, by counting the successive statuses of binary 1 on the D-echo channel, it has determined that no other terminal equipment has o
REFERENCES:
patent: 4562573 (1985-12-01), Murano et al.
patent: 4592045 (1986-05-01), Fundneider
patent: 4686667 (1987-08-01), Ohnsorge
DE 3333379 (Fujitsu), Mar. 22, 84.
IEEE Transactions on Communications, vol. COM-29, (Jun 1981), H. Matt et al.
Nachtiehtentechnische Zeitschrift, vol. 27, issue 8, 1974 (Berlin, DE).
The Sixth International Symposium on Subscribers Loop and Services, Oct. 1984, Ono et al.
Article ISDN-Teilnehmer "Die Teilnehmeranschlusstechnik im ISDN", by Schollmeier, pp. 753-762, in Fernmelde-Praxis-19+2/85.
Bertelsmeier Manfred
Doering Karlheinz
Grimm Karl J.
Jung Min
Olms Douglas W.
Siemens Aktiengesellschaft
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