Third Generation (3G)

Third Generation (3G)
The rate at which new telecommunication standards are being developed is phenomenal.
Alongside the introduction of HSCSD, GPRS and EDGE as standard methods  of data connectivity, operators are eager to deliver advanced methods for data-centric
applications, such as broadcast quality video. Remember, we can already rely on voice
and, to an extent, data connectivity. Operators are always keen to create new scenarios
where there is an increased and continued revenue stream. To that extent, in 1998
the Third Generation Partnership Project (3GPP) a collaboration of partners, which
comprise a number of standards bodies, such as ETSI, the Telecommunications
Technology Committee (TIC) and the Association of Radio Industries and Businesses
(ARIB) to name but a few, made a consorted agreement. The primary objective of this
group is to maintain and support the existing cellular infrastructure and associated
technologies (that is, GSM, HSCSD, GPRS and EDGE). The scope of these activities
also extends to specifying new standards for third generation technology. This will
ultimately benefit the operator, as there is a united driving force ensuring high-speed
interoperable telecommunications standards.
Within the 3G arena an additional multiplexing technique is used called Code
Division Multiple Access (CDMA). This forms our third multiplexing scheme where
our two previous methods were FDMA and TDMA. CDMA is a direct sequence (DS)
technology utilizing a spread spectrum topology where multiple users occupy the
radio channel and frequency concurrently (we will discuss this in more detail later).
An exception to the appearance of CDMA within 3G is cdmaOne; it’s widely deployed
in the US and Korea and is classified as a second generation technology. It is defined
by IS-95 and is now superseded by IS-2000 (also called CDMA2000) and is very
much in competition with GSM. CDMA was initially developed by Qualcomm
(www.qualcomm.com) a research and development company based in the US.One other CDMA variant includes Universal Mobile Telecommunications Service
(UMTS) which is based upon Wideband CDMA (WCDMA); this is perceived as
third generation. 3GPP’s activities are concerned with defining UMTS. More confusingly,
there is a second group called the Third Generation Partnership Project 2
(3GPP2) whose activities include defining third generation technology evolved from
CDMA2000. cdmaOne, CDMA2000 and WCDMA are incompatible standards and
are summarized in Table 3.1.
WCDMA was developed by NTT DoCoMo as Japan’s third generation Freedom of
Mobile Multimedia Access (FOMA) technology. This became the initial draft of UMTS
after NTT DoCoMo submitted it to the International Telecommunications Union (ITU).
ITU, a global standards body, adopted and subsequently incorporated WCDMA into its
International Mobile Telecommunications-2000 (or IMT-2000) specification. This specification
is pivotal in identifying key attributes of what characterizes third generation cellular
technology. One glowing characteristic of the IMT-2000 specification is the attempt
to bring together a cohesive cellular experience where world-wide cellular infrastructures
interwork and interoperate. This translates into users being capable of utilizing one cellular
phone and moving it from state to state and country to country with transparency and
ease. The ITU, 3GPP, 3GPP2 and the Universal Wireless Communications Consortium
(UWCC) all work in partnership to realize IMT-2000. In addition to providing cohesion,
the IMT-2000 also defines the increasing need to deliver broader applications to include
a range of multimedia services from a single cellular platform. Numerous data rates are
offered for a number of application contexts where a minimum of 2Mbps for cellular
users, in a fixed location is offered, to lower data rates (of 384Kbps and 144Kbps) for
mobile consumers, such as pedestrians and vehicle connectivity.The Republic of China has also made its own contribution to the IMT-2000 partnership
in association with Siemens. It has defined a CDMA derivative called Time
Division Synchronous CDMA (or TD-SCDMA) and was incorporated by the 3GPP in
2001 as part of the UMTS standard. It is envisioned that TD-SCDMA will initially be
deployed in China where, at the time of writing, field testing is being conducted.
Underlying UMTS is a radio access method called Universal Terrestrial Radio Access
(UTRA), which constitutes the WCDMA, UTRA/FDD method and the TD-SCDMA,
UTRA/TDD (Time Division Duplex) method. The two methods offer complementary
mechanisms each accommodating the various services that are available through UMTS.
Understanding how CDMA works
CDMA is a Direct Sequence Spread Spectrum (DSSS) technology that doesn’t transmit
on a particular frequency, as compared with FDMA and TDMA. Instead, it uses all
the available bandwidth for multiple users in the same channel, where codes are
assigned to identify individual connections. We illustrate the conceptual model of
CDMA in Figure 3.11. Despite multiple users using the same channel no interference
occurs between conversations. Like FDMA and TDMA, CDMA has access to the
same spectrum, but merely alters the way it uses that spectrum. It is the unique characteristics
of the spread spectrum technique that makes this possible. In short, data is
transmitted in its rawest form (binary 1s and 0s) and is spread over a channel in a
pseudo-random pattern. Both the transmitter and receiver have agreed how to
pseudo-randomly encode and decode the binary data. Similarly, with a number of
potential callers engaged in a connection, a receiver will only listen to a particular conversation,
that is, the conversation that has the right code. The next generation of cellular applications
Will we see the emergence of fourth generation (4G) technology? Yes, we will, and
arguably most academics, researchers, and cellular advocates believe it’s already here,
but it’s a matter of timing and belief. Japan is directing considerable effort in research
and development for this “fourth generation” technology. It is unclear at this stage
what is meant by 4G; how it will be constituted and so on. Several companies believe
that the technology will simply be an upgrade to 3G and others believe it will completely
replace the existing infrastructure. The latter belief is somewhat difficult to
understand, as so many companies have invested so much into delivering 3G technology.
The proposed shift from 3G to 4G is beginning to take shape, albeit on a visionary
basis only, as operators are in the process of deploying 3G cellular services. For example,
within the United Kingdom several operators have only recently introduced 3G services
for its consumer base. Again, it’s hard to understand why operators and the like would
want to replace their existing infrastructure. We will inevitably witness 4G or at least
the concept of this technology, delivering full broadcast quality television across a cellular
network; this effort forms part of the R&D currently undertaken by the Japanese
companies. Perhaps 4G will only exist as a concept, but its emergence as a full-bodied
deployment, most certainly on a national basis, is still a long way off. Increasingly,
with an eagerness to create better wireless applications, perhaps the emergence of
4G technology will itself exist as an amalgamation of wireless technologies, in turn,
creating wireless convergence