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838 WIRELESSINTERNETVoice Telephony as the Primary Service
The current generation of the wide area wireless net-
works, i.e., the cellular networks, has been developed pri-
marily to serve voice telephony. From the physical layer
(e.g., channel coding and transmission) to the application
layer (e.g., voice compression), all aspects of the system
were designed and optimized for the purpose of maximiz-
ing the capacity and the quality of phone calls. Despite the
increasing use of services such as wireless Web and SMS
(to be discussed later), the bulk of present-day wireless
traffic remains voice telephony. For example, according
to Strand Consult’s report from 2002, more than 85% of
mobile service revenues in Europe were from voice tele-
phony in year 2002 (How to make money, 2002). This is
especially noteworthy since Western Europe is one of the
leading markets in use of non-voice wireless services.
Another leading market is South Korea. SK Telecom,
Korea’s leading mobile carrier with 11 million subscribers
which claims to have the most advanced mobile network
based on CDMA 2000 1X (Telecommunications Indus-
tries Association, 2001), recently reported that it expects
to gather only 5.4% of its expected total sales from mo-
bile Internet services. Even though this figure represents
a large increase over previous years, it remains small in
comparison to the revenue from voice telephony. The les-
son here is that while the growth of nonvoice services over
cellular networks will continue, it is important to continue
to serve what is currently the most valuable market, i.e.,
voice telephony.Popularity of Instant Messaging (SMS)
Since its launch in 1995 as a part of the original GSM spec-
ifications, short messaging service has become a tremen-
dously popular service offered on wireless telephone net-
works. Although its nascent growth was fueled by the
younger generation, by the year 2000 the popularity of
SMS has spread beyond the original group. Worldwide,
the use of SMS has skyrocketed. The GSM Association
announced in February 2001 that 15 billion messages
were sent over the world’s GSM wireless networks dur-
ing December 2000, compared to only 3 billion messages
a year before. In terms of revenue, research outfit IDC
expects SMS revenue to reach US$6.5 billion worldwide
by 2002.
SMS provides the ability to send and receive text mes-
sages to and from mobile handsets with message lengths
ranging from 120 to 256 characters. The communication
is near real-time as in Internet-based IM. In addition to
GSM, SMS or SMS-like services are available in other pop-
ular wireless standards, such as in IS-136 and IS-95 net-
works. Virtually any type of information based on text can
be sent using SMS, including e-mails, news headlines, and
some games. The range of applications of SMS has yet to
be thoroughly explored and continues to expand.
The tremendous success of SMS has resulted in devel-
opment of more advanced versions of SMS. The enhanced
messaging service (EMS) is an open 3rd Generation Part-
nership Project (3GPP) standard (3GPP TS 23.040, 2002)
that allows a mobile phone to send and receive not only
plain text, but text enhanced with different fonts and sizes,
images, sounds, and animation. Since EMS also utilizesthe signaling channels for transport and the same SMS
Centers, no network modifications are needed to support
SMS, which allows a relatively painless upgrade path.
In comparison, multimedia messaging service (MMS)
offers more drastic changes both in terms of functional-
ities and requirements (3GPP TS 23.140, 2002). For ex-
ample, MMS data are delivered over the traffic channel
rather than the signaling channel. This would require one
of the new mobile network infrastructures, such as Gen-
eral Packet Radio Service (GPRS) (Cai & Goodman, 1997)
or 3G, as well as new network elements such as multime-
dia messages relays and servers to fully utilize the capabil-
ities of MMS. In return, rich media messages composed
of text, images, audio, and video will be made possible.
Some of the envisioned applications include maps, car-
toons, games, and interactive videos. Just as the current
success of SMS was totally unexpected, it is imprudent to
speculate on the future of these newfangled technologies.
With the development of suitable applications, however,
these services have a good chance of success.Web Access
Based on the growth from the traditional methods of Web
access based on modems and other wireline devices, wire-
less Web access was expected to be the next killer applica-
tion on the wireless cellular networks. Who wouldn’t want
to access all those Web sites with the conveniences of not
being tethered to any sockets or switches on walls? How-
ever, the lofty expectations of exponential growth have yet
to be realized. Problems such as limited speed, incompati-
ble data standards, and poor user interfaces have hindered
the growth. Even so, there were already more than 28 mil-
lion subscribers in Japan, or close to 1/5 of the population,
who subscribe to NTT DoCoMo’s i-mode mobile Internet
service at the end of April 2002 (technically, i-mode is a
specification, not a standard).
Fortunately, there has been much ongoing progress in
addressing some of the difficulties that have plagued wire-
less Web access. Higher bandwidth technologies such as
GPRS and high data rate (HDR) CDMA (Bender et al.,
2000) are beginning to be deployed and will increase data
transmission speeds to more than 171 Kbps. Advances in
user interfaces such as voice recognition and better dis-
plays, in conjunction with increasing use of industry stan-
dards such as WAP and i-mode, will continue to improve
accessibility of the Web via the wireless network.Higher Bit Rates for Data—GPRS and HDR
Two of the more promising wireless technologies slated to
become the main drivers of wireless data access are GPRS
and HDR. Whether they are true 3G service or mere stop-
gap 2.5G is up for debate, but both are able to provide sig-
nificantly enhanced data rates, which will allow more di-
verse applications to be served over the wireless network.GPRS
GPRS builds upon the tremendous success of GSM tech-
nology, which, according to the GSM Association, claims
more than 825 million users in over 193 countries as of
March 2003. The major advantage of GPRS over the exist-
ing GSM data services such as circuit switched data (CSD)