Method for changing-over to standby for a transmission device for the bidirectional transmission of digital signals and arrangement for carrying out the method

• US 5,706,277 A
• Filed: 11/27/1995
• Issued: 01/06/1998
• Est. Priority Date: 05/28/1993
• Status: Expired due to Fees

• Current Assignee: Nokia Siemens Networks GmbH & Company KG (Nokia Corporation)
• Original Assignee: Siemens AG
• Inventors: Klink, Joachim
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Corrielus, Jean B.
• Application Number:
  US08/553,567
• Time in Patent Office: 771 Days
• Field of Search: 375/260, 375/257, 370/217, 370/220, 370/225, 370/226, 370/227, 379/2, 371/20.1, 371/20.6, 371/20.2, 340/827, 340/825.01, 395/182.02
• US Class Current: 370/220
• CPC Class Codes: H04B 10/032 using working and protection systems H04J14/0287 takes precedence
• CPC Class Codes: H04J 2203/006 Fault tolerance and recovery
• CPC Class Codes: H04L 1/22 using redundant apparatus to increase reliability

Abstract

A method is provided for changing over to a standby link for a transmission device for the bidirectional transmission of digital signals. To implement the bidirectional changeover to the standby link as quickly as possible, control information is transmitted, as a rule, in only one step between the terminals (1, 3). In the event of a mismatch between information on the state of the respective local switching device formed locally and received (K2) from the distant station, the local receiving device (14, 34) is connected to the operating link (21) for eliminating the switching fault.

Claims

1. A method for changeover to standby for a transmission device for bidirectional transmission of digital signals in which each of two terminals of a transmission section has a respective transmitting device and is connected to one another via an operating link and a standby link and contains a local monitoring device for detecting transmission faults, each of the two terminals having a switching device, which is controllable by a respective monitoring device, connecting a respective receiving device to the operating link in a first switching state and to the standby link in a second switching state, comprising the steps of:

exchanging control information of the first type and second type between the monitoring devices of the two terminals, the control information of the first type being sent out containing an information item on a local control criteria, and each of the switching devices being controllable by control signals by the respective local monitoring device in dependence on respective local control criteria and on control criteria contained in received control information such that digital signals are optionally passed to the respective receiving device via the operating link or the standby link;

treating both the local control criteria and the control criteria of a remote terminal contained in the received control information of the first type as equivalent switching requests by the monitoring device when the control signals are formed;

operating the respective switching device only in accordance with a switching request having a highest priority in that the sent out control information of the second type contains an information item on the state of the local switching device and in that the local switching device is placed in its first state by the monitoring device when a mismatch occurs between locally formed control information and received control information of the second type, and if the local switching device is in the second state.

2. A changeover device for a transmission device for bidirectional transmission of digital signals between two terminals of a transmission section, comprising:

a transmitting device in each terminal connected to one another via an operating link and a standby link;

a monitoring device in each terminal for detecting transmission faults;

a switching device in each terminal, which is controlled by the monitoring device;

a receiving device in each terminal, the switching device connecting the receiving device to the operating link in a first switching state and to the standby link in a second switching state;

control information of the first type and second type being exchangeable between the monitoring devices of the two terminals, sent out control information of the first type containing an information item on a local control criteria, each of the switching devices being controllable by control signals by the respective local monitoring device in dependence on local control criteria and on control criteria contained in the received control information, such that the digital signals pass optionally via the operating link or the standby link to the receiving device;

each of the monitoring devices being structured such that both the local control criteria and the control criteria of a remote terminal contained in the received control information of the first type are treated as equivalent switching requests when the control signals are formed and such that the respective switching device is only operated in accordance with a switching request having a highest priority;

the sent out control information of the second type containing an information item on the state of a respective local switching device; and

each of the monitoring devices, for a mismatch between locally formed control information and received control information of the second type and with the respective local switching device being in its second state, placing the respective local switching device in the first state.

3. The changeover device as claimed in claim 2, wherein each of the terminals has, in addition to the switching device located at an input of the receiving device, a further switching device optionally connecting the standby link to an output of the transmitting device, and wherein the two switching devices of a common terminal are jointly controlled.

4. The changeover device as claimed in claim 3, wherein the further switching device is structured such that the standby link is optionally connected to the output of the transmitting device or to the output of a further transmitting device and wherein each of the terminals has a further receiving device and wherein an input of a respective further receiving device is optionally connected to the standby link via an additional switching device.

5. The changeover device as claimed in claim 2, wherein the transmission device for the bidirectional transmission of digital signals in each of the terminals has a device for periodic sending-out of the control information of the first type and second type at a transmitting end and a device for converting the periodically received control information into continuous signals at a receiving end.

6. The changeover device as claimed in claim 2, wherein the monitoring device, for a mismatch between locally formed control information and received control information of the second type and due to the switching device being in the second state, is structured to output a message on the switching fault detected in this manner and, after the switching fault has been eliminated, is structured to maintain the message for as long as the mismatch continues to exist.

7. The changeover device as claimed in claim 2, wherein the mismatch between locally formed control information and received control information of the second type is only detected after a predetermined waiting time has elapsed.

8. The changeover device as claimed in claim 2, wherein the transmission device for the bidirectional transmission of digital signals is a transmission device of a synchronous digital hierarchy, and wherein the control information of the first type is transmitted as a K1 byte of the overhead and the control information of the second type is transmitted as a K2 byte of the overhead.

9. The changeover device as claimed in claim 8, wherein the first four bits of the K1 byte contain an information item on a state of the transmission link, an operating state of the changeover device or external control commands, and the last four bits of the K1 byte contain an information item on an associated link.

10. The changeover device as claimed in claim 8, wherein the first four bits of the K2 byte contain an information item on a state of the switching device or the switching devices, respectively.