Browse Prior Art Database

Isdn Subscriber Loop Testing

IP.com Disclosure Number: IPCOM000037250D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Golding, NL: AUTHOR

Abstract

Disclosed is a method by which a terminal or device may determine at installation time if the network connection characteristics are within reasonable limits before service is provided at the network Local Office. If service interruptions occur, the same method will aid in determining the probable location of the fault.

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Isdn Subscriber Loop Testing

Disclosed is a method by which a terminal or device may determine at installation time if the network connection characteristics are within reasonable limits before service is provided at the network Local Office. If service interruptions occur, the same method will aid in determining the probable location of the fault.

The ANSI T1.601-1988 Standard for the U Interface provides for full-duplex communication over one pair of wires at user data rates of up to 144 Kbps. The transmission technique relies on echo-cancellation to receive data from the far end while transmitting at the same time. If data transfer becomes severely errored, then some method of fault isolation is required. The current definition specifically prevents the user from requesting data loop tests at the Layer 1, or transport layer. The only option is to request the Network to provide a loop test service, which is currently not defined, and even when it is, will be charged to the user as a service.

When the interface circuits are powered on, they execute an activation sequence, during which the transmitters at each end of the line generate a signal to "train" their echo-cancellers. Each transmitter, in turn, sends a signal which it also receives and recognizes. By comparing the received data with a copy of the transmitted data, the echo-canceller "learns" the form of its own transmission and can then delete that from the composite signal that will be received when bot...