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Review of:
Mobile Network Evolution:
A Revolution on the Move
Johan De Vriendt, Philippe Laine,
Chritophe Lerouge, and Xiaofeng Xu, Alcatel
David C. Morris
CPSC 502 – Communications I
Summer 2002
The paper I have selected to review, "Mobile Network Evolution: A
Revolution on the Move" was written as an overview of the evolution in mobile
communications.
The authors write about second generation (2G), third
generation (3G), and the future of mobile communications with respect to IP
networks.
The author's objective is to give an overview of the different
technologies while describing the trends towards all-IP networks.
They begin to describe four different 2G technologies which currently
coexist: Global Systems for Mobile Communication (GSM), cdmaOne, Time
Division Multiple Access (TDMA), and Personal Digital Cellular (PDC). Figure 1
of their paper describes the market distribution of these four technologies. The
authors later suggest the market share of the TDMA is likely to increase as they
move towards GSM for financial as well as technical reasons.
GSM is described as being one of the first commercial services, started in
mid 1991, and deployed in 22 countries across 36 networks. In comparison, they
state that in recent days there are now more than 470 GSM networks, in more
than 172 countries, with more than 646 million users.
From a performance
aspect the author's state that by allocating unique time slots to individual users,
GSM can allow eight users to share a single 200 KHz channel. GSM's data
transfer rates were made possible using circuit-switched data (CSD), which
offers a throughput of 14.4 KB/s. However, as a 2G system, GSM has its
drawbacks, it is inherently inefficient for bursty traffic, and it continuously uses
several radio channels. With this, improvements to GSM have been made in the
3G systems, by incorporating Enhanced Data Rate for Global Evolution (EDGE).
In contrast, the next 2D technology the author's describe is cdmaOne.
They state that with cdmaOne, up to 64 users can share the same 1.25 MHz
channel. They claim that is done by attaching a pseudo-random code to each
user, and decode at the opposite end. However, like GSM, cdmaOne offer a
limited throughput, at rates of 14.4 kb/s.
Finally, for 2G systems, the author's describe both TDMA and PDC. They
only give a brief explanation of both, but state that TDMA is a single subscriber
system which assigns a 30 KHz channel to each user. PDC is a Japanese
TDMA-based system operating in the 800 and 1500 MHz bands. Though, as the
authors note, with over 30 million subscribers to PDC, it became necessary to
move towards 3G systems.
Next, the authors shift their discussion to the details of 3G systems. They
begin by explaining that 3G systems became necessary to deal with issues such
as more capacity, new frequencies, and higher bit rates. Within the scope of 3G
systems, there are two main systems, Universal Mobile Telecommunications
Systems (UTMS), and cdma2000. A standard evolution from 2G to 3G can be
seen in Figure 2.
UTMS, as the authors explain, works on Frequency Division Duplex
(FDD), and Time Division Duplex (TDD). They explain that FDD mode is derived
from CDMA, using a 5 MHz carrier frequency for uplink and downlink,
respectively allowing users to achieve data rates up to 384 kb/s. They also
believe that the TDD mode likely to be implemented is the Time-DivisionSynchronous Code-Division Multiple Access (TD-SCDMA).
They believe this
because it allows for a 1.6 MHz carrier spacing instead of 5 MHz, providing the
end user with data rates up to 2 Mb/s, in optimal conditions.
Cdma2000, in comparison, supports and introduces a new air interface on
downlink. This technology only requires a separate 1.25 MHz carrier for data
only, providing up to 2.4 Mb/s on the downlink. The down-side to this is it only
provides 153 kb/s for uplinks. As the authors begin to describe the new IP
network technologies for mobile communications, cdma2000 is thought to
introduce new radio techniques with an all-IP architecture, promising data rates
up to 3 Mb/s.
The move towards IP architecture is being driven by two main objectives:
first, the independence of the transport and control layers, which allow for easier
implementation of new applications, and second, operation and maintenance for
the network. As the authors point out, major new elements in mobile
communications associated with networked architecture, is the ability to easily
track the location of individual mobile stations, and the ability to encapsulate
packets received from external sources and route them. The authors project that
3rd party developers can both rapidly and cost effectively generate customized
applications for each mobile user. Shown within Figures 7 and 8, are the
interconnections of the network, which makes the use of shared resources
possible.
With the conception of using IP-based communications, the ability to
utilize wireless LAN becomes available. They suggest that wireless LANs will be
a complement to the 3G networks. Performance aspects of these wireless LANs
are given to be around 5.5 Mb/s throughput per users. The authors also suggest
that with emerging technologies, such as Bluetooth, wireless LAN products will
migrate to using the 5 GHz band. This band is noted for having throughput
values around the 30 Mb/s range per user. Based on an initiative by both the
IEEE and ETSI, this progress shall be accomplished in a reasonable amount of
time.
Table 1 shows the standard characteristics between wireless LAN
standards. In short, Figure 9 describes how multiple technologies can share and
access the same IP-based core network. This give companies the ability to offer
their users real-time multimedia services, via the user's mobile network.