Multiplex communications – Wide area network – Packet switching
Patent
1984-01-13
1986-03-11
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370 15, H04J 116, H04J 314
Patent
active
045758417
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a method and apparatus in a telecommunication system for checking, with the aid of so-called through-connection testing, the establishment and existence of a duplex connection for transmitting digital information in a time division multiplexed bus network, to which subscribers are connected via line terminals.
BACKGROUND ART
A method is disclosed, e.g., in the Swedish Patent No. 7410475-3, for through-connection testing in a digital exchange of a telecommunication system. The method is characterized by erroneous parity intentionally being introduced into the digital character flow to an input on an exchange, after steps have been taken to set up a connection between the input and a given output at the exchange, subsequent to which such output is scanned with respect to erroneous parity, and that information relating to the result of this scanning indicating an erroneously or correctly established connnection, is transmitted to a central control unit.
DISCLOSURE OF INVENTION
The problem with the known method is that it is entirely under the control of a central control unit controlling all activity relating to the through-connection test, resulting in substantial time delay and complicated hardware. Neither is the method utilizable in a larger switching network with a larger number of exchanges or terminals. The test is limited solely to the exchange. The method is based on parity being checked on the receive side under control of the central processor and established on the send side also under control of the central processor. It is thus necessary to take active steps both on the send and receive side of a connection.
The method and apparatus in accordance with the invention, which solves this problems which is characterized by the claims is utilizable in a multiprocessor system, and is not under the control of any central processor. The through-connection test in accordance with the invention is based on the idea that monitoring to ensure that a connection has been set up and exists, is checked by one and the same terminal, i.e., the termianl transmitting the through-connection test also has the task of detecting it. This means that all other terminals along the path of the connection, e.g., processors and the PCM line terminals, only pass along the test message without taking any further steps. The embodiment of this invention is also based on an erroneous parity bit being added to the data samples. It is indeed possible to use other testing signals than erroneous parity, e.g., a particular check word or a particular check bit. The invention thus permits monitoring that a correct connection has been established in a duplex connection in a digital bus system. The through-connection test (TCT) for both halves of a duplex connection is initiated, and the result is checked at the same point (terminal) of the connection. A parity bit of intentionally wrong polarity is sent together with the speech sample and, is mentioned, the generation of the parity bit and the check of its polarity is performed in the same terminal (processor). In a multiprocessor system initiation and testing can thus be assigned to one and the same processor, which is not possible in the prior art.
BRIEF DESCRIPTION OF DRAWINGS
The apparatus in accordance with the invention is described in detail below with the aid of an embodiment, and with reference to the appended drawing, whereon:
FIG. 1 is a traffic path diagram illustrating the establishment of a connection where the apparatus in accordance with the invention is incorporated;
FIG. 2 depicts a line terminal in the switching network with the apparatus in accordance with the invention shown in a block diagram; and
FIG. 3 is a block diagram of a digital terminal for carrying out the through-connection test.
MODE FOR CARRYING OUT THE INVENTION As will be seen from FIG. 1, a digital
switching network of the kind discussed contains a plurality of terminals T, which are digital, processor-controlled exchanges, one of these terminals de
REFERENCES:
patent: 3739098 (1973-06-01), Camiciottoli et al.
patent: 3830982 (1974-08-01), Christiansen
patent: 4048445 (1977-09-01), Ghisler
patent: 4149038 (1979-04-01), Pitroda et al.
patent: 4296492 (1981-10-01), Hafer
Fagerstedt Nils U. H.
Roos Sture G.
Stipcevic Franko
Chin Wellington
Olms Douglas W.
Telefonaktiebolaget LM Ericsson
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