3GPP and 3GPP2 Packet-Based Voice Transport Technologies
and Packet-Based Voice Quality Enhancement Technology
WHITE PAPER — TELLABS
®
GLOBAL SERVICES
Introduction
“Mr. Watson! Come here, I want to see you.”
Since Alexander Graham Bell uttered those words to his assistant
during the first telephone call on March 10, 1876, voice telecommu-
nications has continued to evolve; from party lines to Bluetooth, from
wireline to wireless. Even with the popularity of e-mail, text messaging
and instant messaging, voice communications is still the dominate
form of inter-personal communication. With convenient and ubiqui-
tous coverage and service, wireless communication has become an
integral part of our daily lives. And as the wireless market grows, and
as competition to increase market share increases, a high level of
Voice Quality remains as an integral requirement for these networks.
This white paper discusses voice transport technological evolutions in
3GPP
1
and 3GPP2
2
, the causes and the types of voice impairments,
and the voice quality enhancement technologies treating those voice
impairments.
Voice Is Still the King
The first fully automatic mobile phone system, Mobile Telephone
System A (MTA), was introduced in 1956. Wireless technology has
developed from the early, first generation and second generation (2G)
technologies to today’s 3G and 4G services. Wireless data commu-
nications were very limited in the early days due to the lack of speed
and practical applications. But, with the introduction of CDMA2000
1XEV-DO and HSDPA/HSUPA, wireless data applications have
become a reality. Instead of the bulky, cumbersome “Brick” phones
of yesteryear, we now use compact, sleek, mobile phones with music,
data and video capabilities settling easily in the pockets of our jeans.
Despite these changes, one thing remains the same — voice is still
the king “Killer Application” in wireless. Voice communication is still
the major revenue contributor for WSPs not only in North America,
but globally as well. Figure 1 illustrates the voice and data revenue for
the North American market.
High voice quality is one of the primary requirements when consum-
ers choose a WSP. The importance of voice quality as a significant
factor in WSP selection is outlined in survey data from such sources
as Consumer Reports
3
and the J.D. Power and Associates “Wireless
Call Quality Performance Study
SM
.”
4
WSPs use this information to their
advantage and WSPs with high voice quality numbers site their voice
quality in their marketing and advertising campaigns.
Data
$250
$200
$150
$100
$50
$0
’10’09’08’07’06’05’04
Millions
Year
’03’02
Voice
High voice quality attracts and retains high revenue customers
while the converse is true for low voice quality. Low voice quality
leads to higher churn rates. The relationship between churn rates
of the major WSPs and their voice quality rankings is clear to even
the unsophisticated observer.
Voice Transport, a Historical Perspective
So how did we get to a high speed, data capable network from the
early beginnings of wireless communications as a voice only means
of communications? The ITU-T G.711 Pulse-Code Modulation (PCM)
standard has been used worldwide for voice transmission. This stan-
dard encodes voice using a 64 kbps bitstream for the voice signal
sampled at 8 kHz. It was soon evident that 64 Kbps bits per call would
consume the available Radio Frequency (RF) spectrum (bandwidth).
Consequently, more bandwidth efficient wireless voice encoders/
decoders (codecs), or vocoders, were developed to reduce the bit
rate and spectrum usage, enabling more calls to traverse the scarce
Source: Gartner 2007
Figure 1. North American mobile service revenues.
1
Third Generation Partnership Project is a global standards body involved with GSM and UMTS
2
Third Generation Partnership Project 2 is a global standards body involved with CDMA
3
ConsumerReports.com, September 2007, URL: http://www.consumerreports.org/cro/electronics-
computers/phones-mobile-devices/phones/cell-phone-service-providers/cell-phone-serviceE1-07/
overview/0107_serve_ov_1.htm
4
http://www.jdpower.com/telecom/ratings/wireless/call_quality/index.asp