Browse Prior Art Database

Fax Relay System for Switched Networks Using Voice Compression

IP.com Disclosure Number: IPCOM000118968D
Original Publication Date: 1997-Oct-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 82K

Publishing Venue

IBM

Related People

Cesaro, C: AUTHOR [+4]

Abstract

There are many attempts today to integrate voice and data traffic over the same network backbone. Many activities, researches, and reports exit around subjects like: Voice-over frame relay, Voice-over ATM, Voice-over IP. But, voice is a real-time traffic and needs to benefit from some priority over traditional data traffic. Therefore, to reduce the bandwidth related to a voice channel and, thus, to reduce the constraint and the impact on network congestion, speech will be compressed in most cases by a voice compression algorithm.

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Fax Relay System for Switched Networks Using Voice Compression

      There are many attempts today to integrate voice and data
traffic over the same network backbone.  Many activities, researches,
and reports exit around subjects like:  Voice-over frame relay,
Voice-over ATM, Voice-over IP.  But, voice is a real-time traffic and
needs to benefit from some priority over traditional data traffic.
Therefore, to  reduce the bandwidth related to a voice channel and,
thus, to reduce the constraint and the impact on network congestion,
speech will be compressed in most cases by a voice compression
algorithm.

      The problem appears when fax transmission occurs on a voice
channel.  Modern voice compression algorithms are optimized for
subjective perception of speech, but do not deal with fax modem
signals.  The distortion introduced by these algorithms is
incompatible with proper fax transmission.

      This disclosure presents a fax demodulation/remodulation system
which can be used in conjunction with any voice compression algorithm
to solve this problem.  The purpose of this system is to demodulate
the fax-modem signal at the source node, to transmit the data
(protocol or picture) over the network, and to remodulate this data
at the output  node.  This allows transparent fax traffic with a
bandwidth of 9.6 kbps,  instead the 64 kbps needed for clear channel
transmission (Fig. 1).

      As shown in Fig. 2, the system includes a signal discriminator
which analyses the PCM signal in order to discriminate between voice
and fax.  If voice is detected, the signal is compressed by the voice
compression algorithm; and if fax is detected, the fax transfer code
is called.  This code is based on V21 (300 bps), V27ter (2.4 and 4.8
kbps), and V29 (7.2 and 9.6 kbps) modems...