IEEE Spectrum June, 2015 - 17

ies of the requirements for intelligible
speech dating back to the 1920s. That
range cuts off high frequencies needed
to discriminate between consonants
such as f and s, but it fit the limited bandwidth of old analog copper phone lines.
In 1988, the International Telecommunication Union approved the G.722 standard for HD Voice, which allows digital
phone lines to carry 50 to 7,000 Hz. But
it was little used because it would have
required upgrading the landline phone
network. The first three generations of
cellular phones instead retained the
3,400-Hz narrowband landline audio,
but they often sounded worse because
of the way they compressed speech
to squeeze more calls into the limited
mobile spectrum. [See "Why Mobile
Voice Quality Still Stinks-and How to
Fix It," IEEE Spectrum, October 2014.]
The broader bandwidth of the Internet allowed Skype and some other VoIP
services to carry 7,000-Hz HD Voice,
but VoIP calls into the phone network
have been limited to 3,400 Hz. Most 4G
smartphones include dedicated circuits
running algorithms to code and decode
7,000-Hz HD Voice, but they can connect
at that rate only if both phones and every
link between them can handle the signals. In practice, that means it works only
between 4G phones on the same carrier.
Full HD will be able to bridge the
audio gap regardless of the network or
the device connected to it. The technological heart of Full-HD Voice is a standard called the Enhanced Voice Services
(EVS) codec. Its speech compression algorithms are more complex and powerful

Full-HD Voice is
Nearly Here
HD Voice, the first major
upgrade to telephone sound
quality since the vacuumtube era, has finally become
widely available-just in time for a new
generation of phone service called FullHD Voice to take its place.
At the Mobile World Congress in Barcelona earlier this year, Fraunhofer IIS
(Institute for Integrated Circuits) demonstrated a system based on a combination of powerful standard algorithms
that can encode and decode in real time
the full audio spectrum to 20 kilohertz
in stereo. Switching to Full HD, which
could be done in many devices as early
as next year, would also mark the complete merging of voice into the mobile
data stream, a goal long in the making.
Full-HD Voice converts speech into
packets that can flow through the Internet along with data traffic, incorporating algorithms that can recover from
packet loss, which turns today's Voice
over Internet Protocol (VoIP) calls into

choppy, unintelligible hash. The technology includes algorithms that encode
music and other nonspeech audio, sounds
that are typically mangled by codes optimized to squeeze many voice calls into
narrow slices of the spectrum. Because
Full-HD Voice carries the whole audio
spectrum, calls sound as if everybody's
in the same room; you can even hear soft
background sounds, like the faint clatter
of fingers on a keyboard. And the powerful coding-decoding (codec) software can
run as a smartphone app.
"We want to bring telephony into the
21st century," just as HD television has done for video, says
Fu l l -H D Vo i ce
H.P. Baumeister, director of
Fraunhofer IIS's U.S. branch,
Plain old
in San Jose, Calif.
telephone
HD Voice
service
There's no doubt that voice
telephony still has a foot in the
20th century. Modern landline
0 Hz
3.400 Hz
7.000 Hz
14.000 Hz
20.000 Hz
phones have a frequency range
of 300 to 3,400 hertz, a staneasy listeNiNg: Unlike earlier systems, Full-HD
Voice will cover the whole range of human hearing.
dard based on Bell Labs studSource: FraunhoFer iiS

getty ImAges

Combining codecs for voice and music will
yield perfectly clear calls

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nORTh aMERICan

JUn 2015

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Table of Contents for the Digital Edition of IEEE Spectrum June, 2015