2.5G and Third Generation (3G) Wireless Technologies

 
2.5G and Third Generation (3G) Wireless Technologies
The intermediate step between 2G and 3G networks is called 2.5G technology. 2.5G includes
networks with transmission speeds of 100Kbps and supports various data technologies.
Third generation (3G) technology will enable wireless devices to send and receive
data as much as seven times faster than a standard 56Kbps modem.17 The growth of 2.5G
and 3G technologies will depend largely on spectrum allocation, infrastructure development
and standardization. 2.5G and 3G technologies are expected to help fuel the growth
of m-business (see Chapter 2, m-Business) and other future wireless communications developments.
10.4.1 High Speed Circuit-Switched Data (HSCSD)
Most 2.5G technologies have moved to packet-switched network technology which we discussed
in Section 10.3.3. However, some alternatives exist which use circuit-switched
transmission technology. Circuit-switched data describes how data is passed through a network
or over a wireless medium. When a user wants to pass information from one source
to another, a connection, or circuit, is made from the source to the desired destination. The
circuit established is permanent for the duration of the transmission.18 Circuit-switched
data technology is common in 1G and 2G networks and is used in some forms of GSM,
CDMA and TDMA networks.
High Speed Circuit-Switched Data (HSCSD) is a 2.5G, circuit-switched technology
designed to enhance GSM networks and increase data speeds up to 115Kbps.19 HSCSD
uses TDMA technology to enhance Web browsing and the transfer of files over wireless
networks.20
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Developers using HSCSD technology include Nokia and Ericsson. Nokia uses HSCSD
in its Card Phone 2.0™ technology for wireless communications. Competing standards
like EDGE and GPRS, which are designed to extend GSM capabilities, could be a challenge
for the adoption and use of HSCSD. In addition, many networks are moving toward
technologies that use packet-switched data, which can support faster, more efficient data
transmissions.
10.4.2 General Packet Radio Service (GPRS)
General Packet Radio Service (GPRS) is a 2.5G technology which can be added to existing
GSM networks to enhance performance and increase transmission speeds. GPRS is projected
to support data speeds of up to 168Kbps, as compared to the 9.6Kbps currently offered
by GSM.
GPRS transmits data using packet data traffic channels (PDCHs) that send packets of
data back and forth from one destination to another on the network. SMS is one packetbased
technology.21 GPRS connections use always-on connectivity allowing users to connect
permanently to the network without having to reconnect each time a transmission
occurs. However, unlike TDMA, the connection transmit only when data is ready to send
by the user (i.e., a phone call is made or a wireless e-mail message is sent).22 GPRS phones
have the capacity to carry a maximum of eight slots to transmit calls on one device, though
it requires more battery power.23
GPRS competes with other 2.5G and 3G technologies including EDGE, CDMA
1xRTT and W-CDMA, which are discussed later in this chapter. GPRS is one of the first
2.5G technologies introduced in the United States and internationally. GPRS can be
installed in mobile devices for a lower cost than existing or developing technologies, therefore,
GPRS could become a viable, cost efficient option for future network implementations.
24
10.4.3 Enhanced Data Rates for Global Evolution (EDGE)
Enhanced Data Rates for Global Evolution (EDGE) is another technology that works over
GSM networks in association with GPRS and TDMA. It provides always-on packet connectivity
and supports a transmission speed of 384Kbps. EDGE is built over existing networks
and does not need its own frequency spectrum to operate.
EDGE technology is used for data-only transmissions. Voice technologies already
covered on the existing networks can be used in conjuction with EDGE. EDGE is currently
being developed by AT&T and Nokia and will enable high-speed wireless Internet access,
e-mail and streaming audio and video.25 EDGE technology provides system developers
with flexibility in network development at lower costs as compared to other projected 3G
technologies.
EDGE system drawbacks include bandwidth and channel-allocation obstacles. The
system does not operate on its own frequency band. Instead, EDGE is built with other technologies
(e.g., GSM) over existing networks.26 EGDE competes with other standards such
as W-CDMA and UMTS (discussed in Section 10.4.5).27
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10.4.4 CDMA2000
CDMA2000 is another 2.5G alternative which also will extend CDMA to 3G capabilities
eventually. It supports existing CdmaOne technologies as well as GSM and TDMA.
CDMA2000 is a family of technologies similar to CdmaOne and currently consists of four
technology types—CDMA 1x Multi-Carrier (1xMC), 1x-EV One, 1x EV-DO and CDMA 3x
Multi-Carrier (3xMC). Members of the CDMA2000 family vary in standard speeds and the
frequency band over which they operate.28
CDMA 1xMC is considered a 2.5G technology similar to EDGE. 1xRTT upgrades
voice and data capacity, doubling the performance of existing CdmaOne networks with
expected data speeds of 144Kbps. 1xRTT is currently used in trial developments with such
operators as Sprint PCS, Verizon and SK Telcom of Korea. Most providers expect to
launch services in late 2001 or 2002.29
1x Evolution (1xEV) is currently supported by vendors like Qualcomm, Lucent and
Ericsson. This technology covers both data and voice transmissions but separates them into
two transmission channels. In addition, 1xEV is being developed in two phases to allow for
development of network infrastructures. The first part of 1xEV is called 1xEV-Data Only
(1xEV-DO). As the name implies, this network supports only data transmissions (i.e.,
streaming audio, video, e-mail and faxes) with no voice capabilities. 1xEV-DO is projected
to support data rates of 2.4Mbps, which is competitive with other developments underway
for 2.5G and 3G networks. It allows wireless data providers to compete with other data
technologies such as Digital Subscriber Line (DSL) and wireless broadband.30 DSL and
wireless broadband are discussed in Chapter 9, Wireless Communications Technologies
(Part I).
The second phase of 1xEV is 1x Data-over-Voice (1xDV). This phase will expand
1xEV-DO networks to handle voice transmissions while maintaining high network speeds.
These networks are supported by many of the service providers which are testing CDMA
1xEV. Trials are expected to begin as early as 2001. However, most networks are not
expected to be established until 2003 or 2005.31
CDMA 3xMC, or 3xRTT, is being developed to expand 1xRTT networks to full 3G
standards. It is designed similar to UMTS (Section 10.4.5) and will support increased data
speeds for both voice and data transmissions. 3xMC development has currently slowed
because 1xEV has been promoted to 3G status by the CDMA Development Group
(www.cdg.org)—1xEV is expected to comply with 3G standards set by respective 3G
standards committees (e.g., ITU and TIA). If 1xEV is a technology that can be used to
develop 3G networks, then a need for 3xRTT as a separate CDMA technology is unnecessary.
32
There are drawbacks to CDMA2000. Companies are developing competing versions
of various technologies in the CDMA2000 family. Final specifications and product standards
cannot be established yet and will be delayed until these developments slow down or
merge together. These companies include Qualcomm, Ericsson, Lucent, Motorola, Nortel
and Samsung. For example, 3Com and Samsung are developing CDMA2000 at speeds of
384Kbps, while the 1xEV under development by Motorola and Nokia supports data speeds
up to 144Kbps.33 CDMA could combine with GSM in the future, possibly establishing uniformity
for wireless network development worldwide. For more information on CDMA
technology including CDMA2000, CDMA 1xRTT and cdmaOne, visit www.qualcomm.
com, www.cdma.com and www.ericsson.com.
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10.4.5 Wideband Code Division Multiple Access (W-CDMA)
One of the fastest-growing versions of CDMA for 3G technology is Wideband CDMA (WCDMA).
This technology expands the current CDMA network capacity and increases
transmission speeds to 2Mbps. It is expected to replace some CDMA and most GSM networks.
34
The ITU standards for W-CDMA are part of the IMT-2000 standards family for 3G
networks. These standards are also known as the Universal Mobile Telecommunications
System (UMTS). To accommodate this new technology, the ITU has decided on a new frequency
spectrum range. The FCC in the U.S. has not offered the same solution for WCDMA
development which currently makes W-CDMA not an option for networks in the
United States.35
W-CDMA supports both packet-switched and circuit-switched data and is intended to
work with all mobile applications.36 W-CDMA operates on a frequency with a much wider
bandwidth than existing networks, allowing for faster transmission speeds. In addition, all
transmissions use the same frequency to minimize interference problems with multiple frequencies.
W-CDMA uses technology that can determine the speed and path that a signal
will take on an individual transmission basis. Each time data is sent over the network, it is
evaluated before the transmission occurs to determine how fast it can be sent and which
route in the network path will maximize efficiency. W-CDMA technology can make these
determinations based on the type of transmission (e.g. data, voice, video, etc.) and the size
of the transmission (i.e., number of MBs, KBs, etc.).37
NTT DoCoMo, Japan’s largest mobile service provider, developed W-CDMA technology.
NTT originally targeted May 2001 as the initial deployment date for W-CDMAbased
3G networks but delayed deployment to late 2001. W-CDMA is the basis for the new
DoCoMo service entitled Freedom of Mobile multimedia Access (FOMA) which is
designed to provide high-speed mobile service for users, enabling them to access information
almost anytime and anywhere. NTT has also developed the i-mode service, one of the
most popular mobile services available in Japan with over 24 million subscribers as of June
2001. Other W-CDMA developers include Siemens (www.siemens.com) and Nortel
Networks (www.nortel.com). i-mode is discussed in detail in Chapter 22, i-mode.
Another form of W-CDMA under development is ultra-wideband CDMA (UWC or
UW-CDMA). UWC does not require a specific frequency band, and therefore, is appealing
to developers because most 3G technologies require a different frequency spectrum than
2G or 1G and creation of an entirely new band to support new transmission technologies.
UWC uses single wave transmission over a wider spectrum instead of continuous, multiple
transmissions. These single-wave transmissions occupy channels for short periods of time
so that channels can be re-used efficiently and with little interference because of their minimal
occupancy time. In addition, instead of sending continuous transmission waves from
a mobile device to a base station and vice versa as in most wireless communications networks,
UWC uses pulses or short bursts of signal transmissions.38 One of the main proponents
of UWC is Time Domain (www.timedomain.com) which incorporates UWC into
its Time Modulated- Ultra Wideband™ (TM-UWB) technology. For tutorials and more
background information, visit www.timedomain.com.
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