Browse Prior Art Database

Communication Carrier Detect and Disable Device for Broadband Local Area Networks

IP.com Disclosure Number: IPCOM000034426D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 4 page(s) / 49K

Publishing Venue

IBM

Related People

Beavers, JA: AUTHOR [+4]

Abstract

A technique is described whereby a communication carrier detect and disable device is used in broadband local area networks (LANs). The concept improves on circuitry designed to detect malfunctioning devices in that it not only provides detection capabilities, but provides a disablement feature to offending communication adapters. This improvement eliminates the need of operator intervention and provides an uninterrupting feature for an entire communication network. Typically, broadband LANs allow computers to communicate with each other over a single cable and utilize a frequency spectrum divided up into six-megahertz-wide channels, similar to television cable networks, and generally occupy two channels, one for transmitting and one for receiving.

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Communication Carrier Detect and Disable Device for Broadband Local Area Networks

A technique is described whereby a communication carrier detect and disable device is used in broadband local area networks (LANs). The concept improves on circuitry designed to detect malfunctioning devices in that it not only provides detection capabilities, but provides a disablement feature to offending communication adapters. This improvement eliminates the need of operator intervention and provides an uninterrupting feature for an entire communication network. Typically, broadband LANs allow computers to communicate with each other over a single cable and utilize a frequency spectrum divided up into six-megahertz-wide channels, similar to television cable networks, and generally occupy two channels, one for transmitting and one for receiving. Radio frequency (RF) modems, used at each of the computer communication adapters, connect to the cable so that converted serial bit streams from the link level protocol of the adapter will function over the LAN. The serial bit streams usually consist of a preamble, start flag, address information, data, cyclic redundancy check (CRC), and a stop flag. Conversely, receiving modems convert the received signal back into the required bit stream. All of the modems transmit at the same frequency up to the head- end, or inbound path. At the head-end, a frequency translator converts the incoming signal to a different channel for transmission out to the modem receivers, or outbound path. The sequence of events must assure that the communications protocol is functioning properly. A protocol, such as carrier sense multiple access/collision detection (CSMA/CD), is generally used for this purpose. The concept described herein is primarily concerned with the carrier sense (CS) portion of this feature. In the general operation of the broadband computer network, before a communication adapter and its modem begins transmitting, it first listens with its receiver to determine if another computer is transmitting on the network. If it detects a carrier signal, it must wait before sending its message, and if no carrier signal is present, it proceeds to send. However, problems can exist, known as "hot carrier", where an adapter or modem is malfunctioning, causing a continuous carrier signal to be present. Since all of the computer adapters are designed to wait until a "no carrier signal" is present, the malfunction can cause the entire system to be down. Although, "hot carrier detect" devices have been designed to detect a carrier malfunction and to identify the offending adapter, no provision was made to circumvent user intervention. Furthermore, the user could be required to re-boot all of the systems on the network, so as to recover from the "hot carrier" error condition. The concept described herein enhances the prior-art "hot carrier detect" devices' ability to identify the offending adapter by implementing circuitry that w...