When 3GPP started standardizing the IMS a few years ago, most analysts expected the
number of IMS deploymentsto grow dramatically as soon the initial IMS specifications were
ready (3GPP Release 5 was functionallyfrozenin the first half of 2002and completedshortly
after that). While those predictions have proven to be too aggressive owing to a number of
upheavals hitting the ICT (Information and Communications Technologies) sector, we are
now seeing more and more commercial IMS-based service offerings in the market. At the
time of writing (May 2008), there are over 30 commercial IMS networks running live traffic,
addingup to over10million IMS users aroundthe world; the IMS is beingdeployedglobally.
In addition, there are plenty of ongoing market activities; it is estimated that over 130 IMS
contracts have been awarded to all IMS manufacturers. The number of IMS users will grow
substantially as these awarded contracts are launched commercially. At the same time, the
number of IMS users in presently deployed networks is steadily increasing as new services
are introduced and operators running these networks migrate their non-IMS users to their
IMS networks.
Wireless communications has become a field of enormous scientific and economic interest. Recent
success stories include 2G and 3G cellular voice and data services (e.g., GSM and UMTS), wireless
local area networks (WiFi/IEEE 802.11x), wireless broadband access (WiMAX/IEEE 802.16x), and
digital broadcast systems (DVB, DAB, DRM). On the physical layer side, traditional designs typically
assume that the radio channel remains constant for the duration of a data block. However, researchers
and system designers are increasingly shifting their attention to channels that may vary within a block.
In addition to time dispersion caused by multipath propagation, these rapidly time-varying channels
feature frequency dispersion resulting from the Doppler effect. They are, thus, often referred to as
being “doubly dispersive.”
During the past three decades, the world has seen signifi cant changes in the telecom-
munications industry. There has been rapid growth in wireless communications, as
seen by large expansion in mobile systems. Wireless communications have moved
from fi rst-generation (1G) systems primarily focused on voice communications to
third-generation (3G) systems dealing with Internet connectivity and multi-media
applications. The fourth-generation (4G) systems will be designed to connect wire-
less personal area networks (WPANs), wireless local area networks (WLANs) and
wireless wide-area networks (WWANs).
This chapter provides extensive coverage of existing mobile wireless technologies. Much of the
emphasis is on the highly anticipated 3G cellular networks and widely deployed wireless local
area networks (LANs), as the next-generation smart phones are likely to offer at least these two
types of connectivity. Other wireless technologies that either have already been commercialized or
are undergoing active research and standardization are introduced as well. Because standardization
plays a crucial role in developing a new technology and a market, throughout the discussion
standards organizations and industry forums or consortiums of some technologies are introduced.
In addition, the last section of this chapter presents a list of standards in the wireless arena.
This book paves the path toward fourth generation (4G) mobile communica-
tion by introducing mobility in heterogeneous IP networks with both third
generation (3G) and wireless local area networks (WLANs), which is seen as
one of the central issues in the becoming 4G of telecommunications networks
and systems. This book presents a thorough overview of 3G networks and
standards and discusses interworking and handover mechanisms between
WLANs and the Universal Mobile Telecommunication System (UMTS).