Third Generation (3G) Overview

The rapid increase in the demand for data services, primarily IP, has been
thrust upon the wireless industry. Over the years there has been much
anticipation of the onslaught of data services, but the radio access platforms
have been the inhibitor from making this a reality. Third generation (3G) is
a term that has received and continues to receive much attention as the
enabler for high-speed data for the wireless mobility market. 3G and all it
is meant to be are defined in the ITU specification International Mobile
Telecommunications-2000 (IMT-2000). IMT-2000 is a radio and network
access specification defining several methods or technology platforms that
meet the overall goals of the specification. The IMT-2000 specification is
meant to be a unifying specification, enabling mobile and some fixed highspeed
data services to use one or several radio channels with fixed network
platforms for delivering the services envisioned:
■ Global standard
■ Compatibility of service within IMT-2000 and other fixed networks
■ High quality
■ Worldwide common frequency band
■ Small terminals for worldwide use
■ Worldwide roaming capability
■ Multimedia application services and terminals
■ Improved spectrum efficiency
■ Flexibility for evolution to the next generation of wireless systems
■ High-speed packet data rates
■ 2 Mbps for fixed environment
■ 384 Mbps for pedestrian
■ 144 Kbps for vehicular traffic
Figure 4-1 shows the linkage between the various platforms that comprise
the IMT-2000 specification group.
The definition of what exactly 3G encompasses is usually clouded in
marketing terms, with the technical reader desiring a straightforward
answer. The reason 3G is hard to pin down is primarily due to the fact that
it involves radio access and network platforms that do not exist right now.
The standard that everyone is striving for is IMT-2000 and it incorporates several competing radio access platforms, which will not achieve harmonization,
if ever, until 4G or beyond. The radio access platforms that comprise
the IMT-2000 specification are all different and it should be no wonder
that it is difficult to obtain a simple answer when asked to describe what a
3G system will look like.
IMT2000/3G can be described as:
■ Being used to reference a multitude of technologies covering many
frequency bands, channel bandwidths, and, of course, modulation
formats.
■ No single 3G-infrastructure platform, technology, or application exists.
■ 3G is applied to mobile and stationary wireless applications involving
high-speed data. IMT-2000 mandates data speeds of 144 Kbps at
driving speeds, 384 Kbps for outside stationary use or walking speeds,
and 2 Mbps for indoors.
Coupled with the different platforms that comprise the IMT-2000 standard
is the issue that the existing 1G/2G platforms need to transition into
the 3G arena. The transition method that an operator must select and
spend currency on is, of course, a difficult decision and will determine how
successful the wireless operator will be in the future. The interim platform
that bridges the 2G systems into a 3G environment is referred to as 2.5G.

What follows is a brief visualization of the interaction between the major
1G, 2G, 2.5G, and 3G platforms. Obviously, if an operator chooses to implement
more than one technology platform for marketing and strategic reasons,
then the lines of transition become more complicated than those
shown in Figure 4-2.
3G is a mobile radio and network access scheme that enables high-speed
data to be utilized, allowing for true multimedia capabilities in a mobile
wireless system. Presently, voice has been the primary wireless application with the use of the short message service (SMS) being the largest packet
data service.

Today’s wireless cellular and personal communications services (PCS)
systems have the same radio bandwidth allocated for both voice and data.
Some of the 2.5G transition or migration plans call for the use of a dedicated
spectrum just for data applications. The IMT-2000 specifies that
data speeds of 144 Kbps for vehicular, 384K for pedestrian, and 2 Mbps for indoor applications are the desired goals and have been built into the
specifications.

Table 4-2 is a brief grouping of the various major technology platforms
and the data speeds that are associated with each.
In examining Table 4-2, it is apparent that several of the IMT-2000 platform
standards are not included and that is on purpose. The platforms that
are listed in both Wideband Code Division Multiple Access (WCDMA) and
CDMA2000 are the two 3G platforms that will be discussed in some level of
detail for the remainder of this textbook. The reason for the two-platform
focus lies in the primary issue that a vast majority of wireless operators,
both existing and new, are planning to utilize one of these two standards,
which are part of the IMT-2000 specification.