Browse Prior Art Database

Variable-Speed Data Transmission

IP.com Disclosure Number: IPCOM000043636D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Borgnis-Desbordes, P: AUTHOR [+2]

Abstract

This is a voice and data modem for transmitting on a medium to high speed (e.g., 9600 bps) communication line, the data received from a set of adapters of different types. The basic principle involves dynamically adapting the transmission speed of the adapters by varying the frequency of the clock signal provided by the voice and data modem. The speed optimization is performed on a frame period, e.g., 20 ms, and introduces the corresponding delay. In a telephone conversation, bursts of speech (e.g., 140 ms long) are mixed with silences. The both-way line capability is unused 60 to 70%. It is thus not consistent to assign fixed time frame durations to the transmission of voice-originated data. Instead, variable time frames should be assigned to voice data, and the spared time frame should be assigned to pure data.

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Variable-Speed Data Transmission

This is a voice and data modem for transmitting on a medium to high speed (e.g., 9600 bps) communication line, the data received from a set of adapters of different types. The basic principle involves dynamically adapting the transmission speed of the adapters by varying the frequency of the clock signal provided by the voice and data modem. The speed optimization is performed on a frame period, e.g., 20 ms, and introduces the corresponding delay. In a telephone conversation, bursts of speech (e.g., 140 ms long) are mixed with silences. The both-way line capability is unused 60 to 70%. It is thus not consistent to assign fixed time frame durations to the transmission of voice- originated data. Instead, variable time frames should be assigned to voice data, and the spared time frame should be assigned to pure data. Let us consider a full duplex 9600 bps line between two voice and data modems (referenced A and B). Each modem will include two ports. A data port to be connected to a terminal (T) and receiving clock signals from the voice and data modem is made operable at rates between 9600 and 2400 bps. The voice port is connected to a tie line (TL) through a voice card which digitizes the voice signal at a rate of 6800 bps. Each 20 ms a Voice Data Modem Controller (VDMC) is provided with 17 bytes of data, the first byte including a voice activity indicator. The VDMC buffers 22 bytes of data to be able to transmit, during the next 20 ms...