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Mechanism for Integrating VOICE and DATA on a Transmission Channel

IP.com Disclosure Number: IPCOM000040224D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Bouillot, M: AUTHOR [+3]

Abstract

A way to integrate voice and data information on the same transmission channel consists in reducing the rate needed for voice transport by means of voice-compression techniques. These techniques are sophisticated, and voice-compression equipment is needed at both ends of the channel. This article relates to a simple mechanism allowing voice and data to be transmitted on the same channel without using voice- compression techniques. Even if no compression technique is used, voice signal can be carried together with data information, due to the fact that voice signal includes no-activity periods. Such periods correspond to a voice level lower than a predetermined threshold. Such no-activity periods are long compared to a slot duration which is generally of 125 microseconds.

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Mechanism for Integrating VOICE and DATA on a Transmission Channel

A way to integrate voice and data information on the same transmission channel consists in reducing the rate needed for voice transport by means of voice-compression techniques. These techniques are sophisticated, and voice-compression equipment is needed at both ends of the channel. This article relates to a simple mechanism allowing voice and data to be transmitted on the same channel without using voice- compression techniques. Even if no compression technique is used, voice signal can be carried together with data information, due to the fact that voice signal includes no-activity periods. Such periods correspond to a voice level lower than a predetermined threshold. Such no-activity periods are long compared to a slot duration which is generally of 125 microseconds. A voice activity detector VAD detects inactivity with an integration of the voice signal over several slots. In this environment a difficulty arises to delimitate the voice and data information since non-compressed voice slots must not be permanently altered and it is not possible to use one bit out of the n bits in the slot to indicate whether this slot carries voice or data. The main idea is to use an HDLC (High Level Data Link Control) flag F as a delimiter, and a slot handler insures that the voice slots never simulate a flag. It is to be noted that the zero-insertion techniques cannot be used inside the voice stream, as it is necessary to keep all voice slots at slot boundaries. The slot handler detects voice slot values corresponding to flags F, and alters them to avoid flag simulations by changing the flag pattern 01111110 into 01111111; the low-order bit is changed from O to 1.

This does not cause any significant degradation of the voice quality.

Once the flag simulations hav...