Browse Prior Art Database

Line Quality Monitoring Method

IP.com Disclosure Number: IPCOM000084931D
Original Publication Date: 1976-Jan-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 39K

Publishing Venue

IBM

Related People

Bryant, PG: AUTHOR [+4]

Abstract

This method enables the quality of data transmission over a telephone line to be monitored by a computer without interrupting the data transmission.

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Line Quality Monitoring Method

This method enables the quality of data transmission over a telephone line to be monitored by a computer without interrupting the data transmission.

The method is applicable to data transmission systems which employ modems of the type that convert different bit patterns into analog signals having different amplitudes and phases. For instance, if the bit stream to be transmitted is broken up into four-bit segments, there will be 16 possible bit combinations, and these can be converted into analog signals having either of two permissible amplitudes at each of eight phase angles (0 degrees, 45 degrees, 90 degrees, 135 degrees, etc.).

If the transmission is faultless, each received analog signal exactly denotes by its amplitude and phase the bit pattern which it represents. More specifically, the particular combination of in-phase (X) and quadrature (Y) components of each received signal will denote one of 16 available X and Y combinations, each corresponding to a respective one of the 16 available bit patterns.

When transmission conditions on the line are less than perfect, the X and Y parameters of the received signals will at best merely approximate some of the standard values of these parametcrs, and the receiving modem 1 then must attempt, if possible, to identify each signal according to the proximity of its X-Y parameters to one of the standard sets of X-Y values. If the X and Y components of each signal are passed through a suitable interface 2 to a suitable graphic converter 3, the received signal will form dot images on the viewing screen 4 of this converter, each dot being positioned along two dimensions in accordance with the in-phase (X) and quadrature (Y) parameters of a respective analog signal.

The various ways in which these dots mav be positioned or arranged relative to standard target points on the screen 4 will indicate to an experienced observer...