Wireless Wide Area Networks
3G (or 3-G) is short for third-generation technology. It is used in the context of mobile phone
standards. The services associated with 3G provide the ability to transfer simultaneously both voice
data (a telephone call) and non-voice data (such as downloading information, exchanging email, and
instant messaging). In marketing 3G services, video telephony has often been used as the killer
application for 3G.
Worldwide roll-out of 3G networks was delayed in some countries by the enormous costs of additional
spectrum licensing fees. In many parts of the world 3G networks do not use the same radio frequencies
as 2G, requiring mobile operators to build entirely new networks and license entirely new frequencies;
a notable exception is the United States where carriers operate 3G service in the same frequencies as
other services. The license fees in some European countries were particularly high, bolstered by initial
excitement over 3G's potential. Other delays were as a result of the expenses related to upgrading
equipment for the new systems.
Japan and South Korea were relatively quick to adopt 3G, because their governments prioritize
technological infrastructure development, and spectrum licensing fees are minimal.
The first country which introduced 3G on a large commercial scale was Japan. In 2005, about 40% of
subscribers used 3G networks only, with 2G being on the way out. It was expected that the transition
from 2G to 3G would be largely completed during 2006, and upgrades to the next 3.5G stage with 3
Mbit/s data rates were under way.
The successful 3G introduction in Japan showed that video telephony was not the killer application for
3G networks after all. The real-life usage of video telephony on 3G networks was found to be a small
fraction of all services. On the other hand, downloading of music found strong acceptance by
customers. Music download services in Japan were pioneered by KDDI with the EZchakuuta and
Chaku Uta Full services.
3G networks are not IEEE 802.11 networks. IEEE 802.11 networks are short range, higher-bandwidth
(primarily) data networks, while 3G networks are wide area cellular telephone networks which
evolved to incorporate high-speed internet access and video telephony.
According to the GSA, in December 2005 there were 100 3G networks in operation in 40 countries in
the world. In Asia, Europe, and the USA, telecommunication companies use WCDMA technology
with the support of around 100 terminal designs to operate 3G mobile networks.
In 2001, NTT DoCoMo—one of the giant telecommunication companies in Japan—was the first
telecommunication company to launch a commercial WCDMA network. The introduction of 3G
services within Europe began in early 2003.
The official 3G mobile network is the systems and services based on the International
Telecommunication Union (ITU) family of standards under the International Mobile
Telecommunications programme, "IMT-2000". A boost was given to 3G mobile networks in Europe
when the European Union council suggested that the 3G operators should cover 80% of the European
national populations by the end of 2005. In Africa, Vodafone Egypt (also known as CLICK GSM) will
provide the service in Egypt in the middle of 2007. Early 2007, Vodacom Tanzania switched on its 3G
HSPDA in Dar ea salaam. With the installation of a 3G HSDPA network, Tanzania is only the second
country in Africa with such technology, the first being South Africa.
The most significant feature offered by third generation (3G) mobile technologies is the capacity to
support greater numbers of voice and data customers — especially in urban centres — as well as
higher data rates at lower incremental cost than 2G.
By using the radio spectrum in bands identified, which is provided by the ITU for Third Generation
IMT-2000 mobile services, it subsequently licensed to operators. 3G uses 5 MHz channel carrier width
to deliver significantly higher data rates and increased capacity compared with 2G networks.
The 5 MHz channel carrier provides optimum use of radio resources for operators who have been
granted large, contiguous blocks of spectrum. On the other hand, it also helps to reduce the cost to 3G
networks while being capable of providing extremely high-speed data transmission to users.
It also allows the transmission of 384kbps for mobile systems and 2Mbps for stationary systems. 3G
users are expected to have greater capacity and improved spectrum efficiency, which will allow them
to access global roaming between different 3G networks.
W-CDMA (Wideband Code Division Multiple Access) is a type of 3G cellular network. W-CDMA
is the higher speed transmission protocol used in the Japanese FOMA system and in the UMTS
system, an advanced 3G system, designed as a replacement for the aging 2G GSM networks deployed
More technically, W-CDMA is a wideband spread-spectrum mobile air interface that utilizes the direct
sequence Code Division Multiple Access signalling method (or CDMA) to achieve higher speeds and
support more users compared to the older TDMA signalling method of GSM networks. W-CDMA is a
competitor to CDMA2000.
Only key features are cited below.
• Radio channels are 5MHz wide.
• Chip rate of 3.84 Mcps
• Supports two basic modes of duplex, frequency division and time division. Current systems use
frequency division, one frequency for uplink and one for downlink. For time division, FOMA
uses sixteen slots per radio frame, where as UMTS uses 15 slots per radio frame.
• Employs coherent detection on uplink and downlink based on the use of pilot symbols.
• Supports inter-cell asynchronous operation.
• Variable mission on a 10 ms frame basis.
• Multicode transmission.
• Adaptive power control based on SIR (Signal-to-Interference Ratio).
• Multiuser detection and smart antennas can be used to increase capacity and coverage.
• Multiple types of handoff between different cells including soft handoff, softer handoff and
W-CDMA was developed by NTT DoCoMo as the air interface for their 3G network FOMA. Later
NTT DoCoMo submitted the specification to the International Telecommunication Union (ITU) as a
candidate for the international 3G standard known as IMT-2000. The ITU eventually accepted W-
CDMA as part of the IMT-2000 family of 3G standards, as an alternative to CDMA2000, EDGE, and
the short range DECT system. Later, W-CDMA was selected as the air interface for UMTS, the 3G
successor to GSM.
Code Division Multiple Access communication networks have been developed by a number of
companies over the years, but development of cell-phone networks based on CDMA (prior to W-
CDMA) was dominated by Qualcomm, the first company to succeed in developing a practical and
cost-effective CDMA implementation for consumer cell phones, its early IS-95 air interface standard.
IS-95 evolved into the current CDMA2000 (IS-856/IS-2000) standard.
In the late 1990s, NTT DoCoMo began work on a new wide-band CDMA air interface for their
planned 3G network FOMA. FOMA's air interface, called W-CDMA, was selected as the air interface
for UMTS, a newer W-CDMA based system designed to be an easier upgrade for European GSM
networks compared to FOMA. FOMA and UMTS use essentially the same air interface, but are
different in other ways; thus, handsets are not 100% compatible between FOMA and UMTS, but
roaming is supported.
Qualcomm created an experimental wideband CDMA system called CDMA2000 3x which unified the
W-CDMA (3GPP) and CDMA2000 (3GPP2) network technologies into a single design for a
worldwide standard air interface. Compatibility with CDMA2000 would have beneficially enabled
roaming on existing networks beyond Japan, since Qualcomm CDMA2000 networks are widely
deployed, especially in the Americas, with coverage in 58 countries in 2006. However, divergent
requirements resulted in the W-CDMA standard being retained and deployed.
Despite incompatibilities with existing air-interface standards, the late introduction of this 3G system,
and despite the high upgrade cost of deploying an all-new transmitter technology, W-CDMA has been
adopted and deployed rapidly, especially in Japan, Europe and Asia, and is already deployed in over 55
countries with ????? subscribers in 2006.
Rationale for W-CDMA
W-CDMA transmits on a pair of 5 Mhz wide radio channels, while CDMA2000 transmits on one or
several pairs of 1.25 MHz radio channels. Though W-CDMA does use a direct sequence CDMA
transmission technique like CDMA2000, W-CDMA is not simply a wideband version of CDMA2000.
The W-CDMA system is a new design by NTT DoCoMo, and it differs in many respects from
CDMA2000. From an engineering point of view, W-CDMA provides a different balance of costs vs.
capacity vs. performance vs. density, and promises to achieve a benefit of reduced cost for video phone
handsets. W-CDMA may also be better suited for deployment in the very dense cities of Europe and
Asia. And cross-licencing of patents between Qualcomm and W-CDMA vendors has eliminated
possible patent issues due to the features of W-CDMA which remain covered by Qualcomm patents.
W-CDMA has been developed into a complete set of specifications, a detailed protocol that defines
how a mobile phone communicates with the tower, how signals are modulated, how datagrams are
structured, and system interfaces are specified allowing free competition on technology elements.
The world's first commercial W-CDMA service, FOMA, was launched by NTT DoCoMo in Japan in
Elsewhere, W-CDMA deployments have been exclusively UMTS based. See the main UMTS article
for more information.
Universal Mobile Telecommunications System
Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile
phone technologies. The currently most common form uses W-CDMA as the underlying air interface,
is standardized by the 3GPP, and is the European answer to the ITU IMT-2000 requirements for 3G
cellular radio systems.
To differentiate UMTS from competing network technologies, UMTS is sometimes marketed as
3GSM, emphasizing the combination of the 3G nature of the technology and the GSM standard which
it was designed to succeed.
This article discusses the technology, business, usage and other aspects encompassing and surrounding
UMTS, the 3G successor to GSM which utilizes the W-CDMA air interface and GSM infrastructures.
Any issues relating strictly to the W-CDMA interface itself may be better described in the W-CDMA
UMTS, using W-CDMA, supports up to 14.0 Mbit/s data transfer rates in theory (with HSDPA),
although at the moment users in deployed networks can expect a performance up to 384 kbit/s for R99
handsets, and 3.6 Mbit/s for HSDPA handsets in the downlink connection. This is still much greater
than the 14.4 kbit/s of a single GSM error-corrected circuit switched data channel or multiple 14.4
kbit/s channels in HSCSD, and - in competition to other network technologies such as CDMA2000,
PHS or WLAN - offers access to the World Wide Web and other data services on mobile devices.
Precursors to 3G are 2G mobile telephony systems, such as GSM, IS-95, PDC, PHS and other 2G
technologies deployed in different countries. In the case of GSM, there is an evolution path from 2G,
called GPRS, also known as 2.5G. GPRS supports a much better data rate (up to a theoretical
maximum of 140.8kbit/s, though typical rates are closer to 56kbit/s) and is packet switched rather than
connection oriented (circuit switched). It is deployed in many places where GSM is used. E-GPRS, or
EDGE, is a further evolution of GPRS and is based on more modern coding schemes. With EDGE the
actual packet data rates can reach around 180 kbit/s (effective). EDGE systems are often referred as
Since 2006, UMTS networks in many countries have been or are in the process of being upgraded with
High Speed Downlink Packet Access (HSDPA), sometimes known as 3.5G. Currently, HSDPA
enables downlink transfer speeds of up to 3.6Mbit/s. Work is also progressing on improving the uplink
transfer speed with the High-Speed Uplink Packet Access (HSUPA). Longer term, the 3GPP Long
Term Evolution project plans to move UMTS to 4G speeds of 100Mbps down and 50Mbps up, using a
next generation air interface technology based upon OFDM.
UMTS supports mobile videoconferencing, although experience in Japan and elsewhere has shown
that user demand for video calls is not very high.
Other possible uses for UMTS include the downloading of music and video content, as well as live
Beginning in 2003 under the name 3, Hutchison Whampoa gradually launched their startup UMTS
networks worldwide including Australia, Austria, Denmark, Hong Kong, Italy, United Kingdom,
Ireland and Sweden.
Operators are starting to sell mobile internet products that combine 3G and Wi-Fi in one service.
Laptop owners are sold a UMTS modem and given a client program that detects the presence of a Wi-
Fi network and switches between 3G and Wi-Fi when available. Initially Wi-Fi was seen as a
competitor to 3G, but it is now recognised that as long as the operator owns or leases the Wi-Fi
network, they will be able to offer a more competitive product than with UMTS only. Nokia predicted
that by the end of 2006 one sixth of all cellular phones would be UMTS devices.
Enhanced Data Rates for GSM Evolution
Enhanced Data rates for GSM Evolution (EDGE) or Enhanced GPRS (EGPRS), is a digital
mobile phone technology that allows to increase data transmission rate and improve data transmission
reliability. It is generally classified as a 2.75G network technology. EDGE has been introduced into
GSM networks around the world since 2003, initially in North America.
It can be used for any packet switched applications such as an Internet connection. High-speed data
applications such as video services and other multimedia benefit from EGPRS' increased data capacity.
EDGE Circuit Switched is a possible future development.
EDGE/EGPRS is implemented as a bolt-on enhancement to 2G and 2.5G GSM and GPRS networks,
making it easier for existing GSM carriers to upgrade to it. EDGE/EGPRS is a superset to GPRS and
can function on any network with GPRS deployed on it, provided the carrier implements the necessary
Although EDGE requires no hardware or software changes to be made in GSM core networks, base
stations must be modified. EDGE compatible transceiver units must be installed and the base station
subsystem (BSS) needs to be upgraded to support EDGE. New mobile terminal hardware and software
is also required to decode/encode the new modulation and coding schemes and carry the higher user
data rates to implement new services.
In addition to Gaussian minimum shift keying (GMSK), EDGE uses 8 phase shift keying (8PSK) for
the upper five of its nine modulation and coding schemes. EDGE produces a 3-bit word for every
change in carrier phase. This effectively triples the gross data rate offered by GSM. EDGE, like GPRS,
uses a rate adaptation algorithm that adapts the modulation and coding scheme (MCS) according to the
quality of the radio channel, and thus the bit rate and robustness of data transmission. It introduces a
new technology not found in GPRS, Incremental Redundancy, which, instead of retransmitting
disturbed packets, sends more redundancy information to be combined in the receiver. This increases
the probability of correct decoding.
EDGE can carry data speeds up to 236.8 kbit/s for 4 timeslots (theoretical maximum is 473.6 kbit/s for
8 timeslots) in packet mode and will therefore meet the International Telecommunications Union's
requirement for a 3G network, and has been accepted by the ITU as part of the IMT-2000 family of 3G
standards. It also enhances the circuit data mode called HSCSD, increasing the data rate of this service.
EGPRS modulation and coding scheme (MCS)
Coding and modulation Speed
scheme (MCS) (kbit/s)
MCS-1 8.8 GMSK
MCS-2 11.2 GMSK
MCS-3 14.8 GMSK
MCS-4 17.6 GMSK
MCS-5 22.4 8-PSK
MCS-6 29.6 8-PSK
MCS-7 44.8 8-PSK
MCS-8 54.4 8-PSK
MCS-9 59.2 8-PSK
Whether EDGE is 2G or 3G depends on implementation. While Class 3 and below EDGE devices
clearly are not 3G, class 4 and above devices perform at a higher bandwidth than other technologies
conventionally considered as 3G (such as 1xRTT). Because of the variability, EDGE is generally
classified as 2.75G network technology.