Multiplex communications – Fault recovery – Bypass an inoperative switch or inoperative element of a...
Patent
1995-11-27
1998-01-06
Chin, Wellington
Multiplex communications
Fault recovery
Bypass an inoperative switch or inoperative element of a...
375228, 371 201, 39518202, H04Q 1100
Patent
active
057062773
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for changing-over to standby for a transmission device for the bidirectional transmission of digital signals and to an arrangement for carrying out the method.
Such a method and such a changeover device are already known from CCITT Recommendation G.783, Geneva 1990, ANNEX A.
The known changeover device is provided for a transmission device for the bidirectional transmission of digital signals, in which two terminals are connected to one another via an operating link and a standby link. The two terminals in each case contain a monitoring device for finding transmission faults. A switching device, which can be controlled by the monitoring device, connects a receiving device to the operating link in a first switching state and to the standby link in a second switching state. Between the control devices of the two terminals, control information of the first and second type is exchanged. The switching device is in each case controlled by the local monitoring device in dependence on local control criteria and control criteria contained in control information received from the distant station.
One of the methods according to CCITT Recommendation G.783, Annex A, relates to transmission devices of the synchronous digital hierarchy SDH and uses the K1 and K2 bytes of the section overhead for coordinating the switching process bidirectionally between the two terminals. To conclude a switching process, altered K1 and/or K2 bytes must be transmitted three times in succession between the two terminals.
Furthermore, a variant of a bidirectional switch-over which only provides for K1 and K2 bytes to be exchanged twice is described in the said recommendation.
From published European patent application 0 533 167, an optical communication system with circuit switching is known. From published European patent application 0 507 379, a protective device for an optical transmission facility is known.
SUMMARY OF THE INVENTION
It is the object of the invention to develop the method and, respectively, the changeover device of the type initially mentioned, in such a manner that the bidirectional changing over to the standby link takes place as rapidly as possible. In particular, the changeover device should be suitable for line equipment of the synchronous digital hierarchy with a 1+1 or 1:1 arrangement, the same information signal being transmitted from one terminal to the other via the operating link and the standby link in a 1+1 arrangement and via the operating link or the standby link in a 1:1 arrangement.
In the known switch-over, a sequence of a number of steps can be used for ensuring, that the switching devices of both transmission directions correspond to one another after the sequence of steps has ended.
The invention is based on the finding that the average duration of the bidirectional changeover to standby can be considerably shortened by a bidirectional switch-over with only a single information transmission being provided in which in exceptional cases switching faults can occur and such a switching fault, if necessary, being corrected in a correction phase which can also be implemented in a simple manner.
According to the invention, the switching request with the highest priority of the local switching requests and of the switching requests received from the remote distant station is in each case selected in both terminals. Local and received switching requests are dealt with on an equal basis. The switching request thus selected determines the controlling of the switching device directly, that is to say without further exchange of information with the distant station.
The measures according to the invention result in the advantage that, as a rule, the operation of the switching devices in the two terminals can take place with only a single transmission of the control information between the two terminals. The changeover process is thus normally concluded very rapidly for both transmission directions of the bidirectional information transmission.
When
REFERENCES:
patent: 4905222 (1990-02-01), Seeger et al.
patent: 5014264 (1991-05-01), Nagler et al.
Chin Wellington
Corrielus Jean B.
Siemens Aktiengesellschaft
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