Third Generation or 3G, as the name suggests, refers to the
third generation of mobile telephony or cellular technology. However,
operators are already touting 4G with lots of marketing hype, despite
the fact that many experts think only five or six percent of mobile Internet
users will be using 4G by 2015. Thus, 3G is here to stay for the
short-term, at least, if not beyond. Let’s look at a generational
timeline to see how the technology has evolved and where it is today.

The First
Generation (1G) began in the 1980s with the deployment of Advanced
Mobile Phone Service (AMPS) that carried analog voice in the 800 MHz
frequency band. The Second Generation (2G) followed in the 1990s with
two competing digital voice standards: Code Division Multiple Access
(CDMA) and Time Division Multiple Access (TDMA), the latter of which is
used by the Global System for Mobile Communication (GSM). CDMA operated
in the 800 MHz band, whereas TDMA operated in the 900 and 1800 MHz
bands. This digital technology allowed for smaller, less expensive
devices for voice and data transmission and led to an increased demand
for speed and bandwidth. 

Thus, 2.5G emerged, although it was not an official wireless standard, referring to
interim packet switched networks that sent bursts of data as needed
rather than locking up a channel for the duration of an
exchange. Examples of 2.5G networks included Single Carrier Radio
Transmission Technology (1xRTT),
1x Evolution-Data Optimized (EV-DO), 1x Evolution-Data Voice (EV-DV), and 1xEV-DO Revision A
on the CDMA evolutionary roadmap, as well as General Packet Radio Service
(GPRS), Enhanced Data Rates for GSM Evolution (EDGE), and various versions of High-Speed Packet Access (HSPA), including
HSPA+, on the GSM evolutionary roadmap, with speeds ranging from about 50 to nearly 400 Kbps, depending on the technology.

Under the International
Telecommunications Union (ITU) group of standards belonging to the
International Mobile Telecommunications (IMT)-2000 initiative, 3G was
rolled out early in this century. Japan’s NTT DoCoMo launched the
world’s first 3G network for commercial use in 2001, and South Korea’s
SK Telecom followed in 2002 using 1xEV-DO. Soon operators around the world rolled out wireless broadband 3G networks, which support a wide range
of applications for consumers and businesses, including high-speed Internet and
intranet access, streaming media, and mobile TV. 

For the most part, wireless operators chose either the CDMA or
GSM roadmap for building out and enhancing their 3G networks, but both
roadmaps and most carriers are now converging on Long-Term Evolution
(LTE) for their 4G technology. Competition
between the CDMA and GSM 3G paths brought innovation in technologies,
features, and services, as well as lower prices, although international
markets tended more towards GSM. WiMAX, once holding a time to market
advantage over LTE for evolved 3G or 4G, was also poised to be an
option for integrated fixed/mobile wireless services beyond 3G, but
Sprint’s recent change in direction to LTE pushes WiMAX technology more
solidly towards emerging markets.

As
with 2G wireless networking, there is no single 3G standard; 3G
standards include CDMA2000, Wideband-CDMA/Universal Mobile
Telecommunications System (W-CDMA/UMTS), and Time Division-Synchronous
Code Division Multiple Access (TD-SCDMA), a home-grown standard in
China. (TD-SCDMA is considered
an iteration of UMTS with a slightly different radio interface.)

W-CDMA
is the air interface for one of the ITU’s family of 3G mobile
communications systems and was developed by the global GSM community as
its chosen path for 3G evolution. GSM networks were designed from the
beginning to be an international digital cellular service. Since it is
based on
digital technology, GSM allows synchronous and asynchronous data to be
transported as a bearer service to or from an Integrated Services Digital Network (ISDN) terminal. Data
can use either the transparent service, which has a fixed delay but no
guarantee
of data integrity, or a non-transparent service, which guarantees data
integrity
through an Automatic Repeat Request (ARQ) mechanism, but with variable
delay.
Supplementary services are provided on top of teleservices or bearer
services,
including such features as caller identification, call forwarding, call
waiting,
and multi-party conversations. There is also a lockout feature, which
prevents
the dialing of certain types of calls, such as international calls. GSM
uses a combination of Time- and Frequency-Division Multiple Access
(TDMA/FDMA)
to divide bandwidth among as many users as possible. FDMA
involves dividing the frequency of the total 25-MHz bandwidth into 124
carrier frequencies of 200-KHz bandwidth. One or more carrier
frequencies are
then assigned to each base station, with each of these carrier
frequencies divided in
time using a TDMA scheme, into eight time slots. One time slot
is used for transmission by the mobile device and one for reception;
they are
separated in time so that the mobile unit does not receive and transmit
simultaneously. Within the framework of TDMA, two types of channels are provided–traffic
channels and control channels. Traffic channels carry voice and data between
users, while the control channels carry information that is used by the network
for supervision and management.  

W-CDMA
enables the continued support of voice, text, and multimedia services,
in addition to richer mobile multimedia, such as music, TV and video,
entertainment, and Internet access. Speeds for 3G W-CDMA theoretically hit
7.2 Mbps, though considerably less in practice.