Alcatel-Lucent omniacces-voip gateway User Manual
VoIP Standards for Development
Page 1-18
A-Law and Mu-Law are processes needed to compand digital signals. A-Law is used in most
countries except for the U.S., Canada and Japan where Mu-Law is more common. Compand-
ing is the process of compressing the amplitude range of a single signal, and then expanding
them at the receiving end back to their original form. Although it is impossible to exactly
reproduce an analog signal digitally, companding greatly improves the accuracy of this
process. PCM uses two different companding processes. For this reason, PCM A-Law is used
for international networks.
countries except for the U.S., Canada and Japan where Mu-Law is more common. Compand-
ing is the process of compressing the amplitude range of a single signal, and then expanding
them at the receiving end back to their original form. Although it is impossible to exactly
reproduce an analog signal digitally, companding greatly improves the accuracy of this
process. PCM uses two different companding processes. For this reason, PCM A-Law is used
for international networks.
A-Law: The PCM coding and companding standard used in Europe and in areas outside of
North America. A-Law encoding samples audio waveforms used in the 2.048 Mbps, 30-chan-
nel PCM system (E-carrier).
North America. A-Law encoding samples audio waveforms used in the 2.048 Mbps, 30-chan-
nel PCM system (E-carrier).
Mu-Law (E-Law): The PCM voice coding and companding standard used in Japan and North
America. A PCM encoding algorithm where analog voice signals are sampled 8,000 times per
second with each sample represented by an eight-bit value, and a raw 64 Kbps transmission
rate. All sample bits are inverted before transmission.
America. A PCM encoding algorithm where analog voice signals are sampled 8,000 times per
second with each sample represented by an eight-bit value, and a raw 64 Kbps transmission
rate. All sample bits are inverted before transmission.
♦ Note ♦
A-Law and Mu-Law are incompatible. For example, a
signal sent with A-law cannot be received by a system
using Mu-Law.
signal sent with A-law cannot be received by a system
using Mu-Law.
G.723.1
This is the ITU-T algorithm recommendation used for compressed digital audio over Plain Old
Telephone Service (POTS) lines. It is the voice part of H.324 (POTS video conferencing). This
algorithm runs at 6.3 or 5.3 kbps (20 bytes per 30ms interval) and uses linear predictive
coding and dictionaries, which help provide smoothing. The smoothing process is CPU-inten-
sive during real time based activities.
Telephone Service (POTS) lines. It is the voice part of H.324 (POTS video conferencing). This
algorithm runs at 6.3 or 5.3 kbps (20 bytes per 30ms interval) and uses linear predictive
coding and dictionaries, which help provide smoothing. The smoothing process is CPU-inten-
sive during real time based activities.
G.729a
This is the ITU’s standard voice algorithm – CS-ACELP (Conjugate Structure Algebraic Code
Excited Linear Predictive for the encoding/decoding of speech at 8 Kbps using conjugate-
structure, algebraic-code excited linear predictive method. G.729 is supported by inter alia
(among other things), American Telephone and Telegraph, France Telecom and Japan’s
Nippon Telephone and Telegraph.
Excited Linear Predictive for the encoding/decoding of speech at 8 Kbps using conjugate-
structure, algebraic-code excited linear predictive method. G.729 is supported by inter alia
(among other things), American Telephone and Telegraph, France Telecom and Japan’s
Nippon Telephone and Telegraph.
VON (Voice on the Net) Developments
The VON (Voice on the Net) Coalition is concerned with developments in Internet Tele-
phony and IP Telephony around the world. It is an incorporated, non-profit U.S. organization
working with the government, business and other groups and individuals on regulations that
affect this technology and its use. Alcatel’s H.323 VoIP gateway was designed with the consid-
erations of the VON Coalition in mind. Compression techniques and DSPs improve the qual-
ity of VON transmissions and minimize problems associated with IP packet delays.
phony and IP Telephony around the world. It is an incorporated, non-profit U.S. organization
working with the government, business and other groups and individuals on regulations that
affect this technology and its use. Alcatel’s H.323 VoIP gateway was designed with the consid-
erations of the VON Coalition in mind. Compression techniques and DSPs improve the qual-
ity of VON transmissions and minimize problems associated with IP packet delays.