At&t Bell Laboratories

At+t Corp.

Peter M Dollard

Sid Chaudhuri

Simon S Zelingher

Chin-Wang Chao

Thomas S Afferton

Mei Deng

Liem T Nguyen

Sarma S Tanuku

Omar M Mansour

Robert P Guenther

William E Goodson

Hossein Eslambolchi

Z Ming Ma

David R Cochran

James D Askew

William Turin

A network that is architectured to distributively be responsible for remedying failures achieves advantageous operation. This is accomplished by algorithmically and distributively assigning the responsibility for recovery from all failures to different network nodes and by re-routing traffic at the failed point though network elements in close topological proximity to the failed point. Each node maintains an awareness of the spare resources in its neighborhood and pre-plans re-route plans for each of the failures for which it is responsible. It maintains the created re-route plans and, upon detection of a failure, transmits a re-route plan to particular nodes that participate in the re-routing recovery planned for such a failure. Alternatively, it transmits re-route plans to the nodes that need them, and upon detection of a failure, the network node broadcasts an ID of the re-route plan that needs to be executed. Nodes that receive a plan ID that corresponds to a plan that they possess execute the relevant plan. Whenever the spare resources change in a manner that suggests that a re-route plan needs to be revisited, the network node initiates a new re-route preplanning process.

Local information-based restoration arrangement

An in-band fault detection and isolation system and method for networks such as Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) networks. Fault detection may be quickly and efficiently performed by a network without requiring modification to any add/drop multiplexers (ADMs) and/or without the involvement of an external network management system (NMS). To accomplish this without violating SONET/SDH standards, a new signal, called a fault isolation signal in the path (FIS-P), is proposed. The FIS-P may be used in lieu of an AIS-P to support special applications on certain digital cross connect (DCS)-to-DCS path segments. Moreover, the present invention may be implemented such that the behavior, of path terminating equipment (PTE) is unaffected.

Fault detection and isolation in a synchronous optical network (SONET) and in a synchronous digital hierarchy (SDH) network

A restoration system is provided for enhancing the reliability of a telecommunications network such that particular traffic which is disrupted by, for example, a faulty link, may be quickly rerouted via an alternate route established 'on the fly'. In particular, each node and link forming the network is monitored, and in the event that such monitoring detects a faulty link or node then a central controller is notified. The controller is arranged to locate spare capacity and establish an alternate route, in which the continuity of the alternate route is confirmed before the disrupted traffic is transferred thereto.

Telecommunications network restoration architecture

The present invention relates to a quasi-soft decision decoder for convolutional self-orthogonal codes which includes a multistage syndrome register, a bit detection means, parity check means and threshold logic gates. The bit detection means is augmented to render a 'quality' bit in conjunction with each detected data bit which indicates the quality of the received signal level for that bit when compared with a predetermined threshold signal level. Memory storage is provided for storing the quality bits in parallel with memory storage for the data bits. Each of the threshold logic gates includes a separate group of active inputs from the syndrome register plus an associated one of the quality bits, each gate being arranged to generate an information correction bit which is dependent on a predetermined threshold level of corresponding input signals. The quality bit, therefore, provides an additional vote in the decision of whether a suspect data bit is erroneous or not.

Quasi-soft decision decoder for convolutional self-orthogonal codes

The present invention relates to a decoder (10) for convolutional self-orthogonal codes which includes a multistage syndrome register (16) and is responsive to two separate threshold levels. The first threshold level, as in prior art arrangements, includes a first majority logic circuit (24) connected to selected stages of the syndrome register and functions to correct the information bits (X.sub.1 -X.sub.7) currently being processed. Instead of also using this majority logic circuit to correct the syndrome register, as in the prior art, the present invention includes a second majority logic circuit (28), which operates at a different threshold level than the first and functions to correct the selected stages of the multistage syndrome register.

Dual threshold decoder for convolutional self-orthogonal codes

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Highlands, NJ, United States of America

Peter M Dollard