Apco P25 Dvsi's Ambe+2 - Icom IC-F9011 User Manual

IC-F9510 series has DVSI AMBE +2™ New
Vocoder Ready
Digital Voice Systems, Inc. specializes in low rate,
high-quality voice compression products for use in
digital communications and storage applications.
Their products include vocoders, error correction
schemes, test sets, and other offerings. DVSI is a
leading provider of hardware and software voice leading provider of hardware and software voice
coding solutions to equipment manufacturers and
OEMs throughout the world.
DVSI has introduced a new low data rate AMBE+2™
Vocoder that sets a new standard for high-quality,
high-performance speech quality at data rates from
2.0 to 9.6 kbps.
The new vocoder technology has been shown to
outperform DVSI's previously industry-leading
AMBE+ ™ Vocoder, that outperformed G.729 and
G.726 vocoders while operating at only 4.0 kbps, and
DVSI's baseline AMBE ™ vocoder technolgy.
It is designed to be particularly robust and perform
exceptionally well even under bit errors and acoustic
background noise conditions.
Recent independent evaluations have proved that
the model-based, Multi-Band Excitation algorithm
provides distinct advantages over traditional CELP-
based vocoders. Operating at data rates from 2.0 to
9.6 kbps, the new AMBE+2™ algorithm has achieved
higher Mean Opinion Scores (MOS) than any other higher Mean Opinion Scores (MOS) than any other
vocoder technology tested.
The superior performance characteristics of the new
AMBE+2™ Vocoder make it ideally suited for mobile
radio, secure voice, satellite communications,
computer telephony, and other digital voice and
storage applications where bandwidth is at a
premium and low data rate, high-quality is premium and low data rate high quality is
imperative.
The new AMBE+2™ Vocoder clearly illustrates why
DVSI has been selected for many prominent global
mobile satellite systems including: Inmarsat M and
Mini-M, Iridium, ICO-Global, Thuraya, ACeS, and
many others. DVSI was also chosen as the vocoder
standard for the North American, APCO Project 25
public safety mobile radio system.
4-8 APCO P25 DVSI AMBE+2™ Vocoder
The Mean Opinion Score Values p
In multimedia using codecs to compress the
bandwidth requirement (for example, of a digitized
voice connection from the standard 64 kilobit/sec
PCM Modulation), the Mean Opinion Score (MOS)
provides a numerical indication of the perceived
quality of received media after compression and/or
transmission. The MOS is expressed as a single
number in the range 1 to 5, where 1 is lowest number in the range 1 to 5 where 1 is lowest
perceived audio quality, and 5 is the highest
perceived audio quality measurement. Here is the
AMBE+2™ MOS test result.
The vocoder speed specified by P25 specification
slowed down from 7200 bps to 3200 bps but DVSI
introduced a new enhanced vocoder of AMBE+2™ and
prevented the deterioration of the sound quality. Please prevented the deterioration of the sound quality Please
see the graph above. Even in 3600 bps, the AMBE+2™
is better than the P25 standard vocoder.
How Are MOS Tests Conducted?
MOS tests for voice are specified by ITU-T
recommendation P.800. The MOS is generated by
averaging the results of a set of standard, subjective
tests where a number of listeners rate the heard tests where a number of listeners rate the heard
audio quality of test sentences read aloud by both
male and female speakers over the communications
medium being tested. A listener is required to give
each sentence a rating using the following rating
scheme:
MOS Quality Impairment
5 5 Excellent E cellent Imperceptible Imperceptible
4 Good Perceptible but not annoying
3 Fair Slightly annoying
2 Poor Annoying
1 Bad Very annoying
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