by January 7, 2000 0 comments

The compact and portable nature of mobile devices will soon
lead to a convergence of a variety of applications, such as e-mail, stock
quotes, multimedia content, etc, on to the mobile handset. However, for this to
happen, you should be able to transfer data at high rates, significantly higher
than today’s 9.6 kbps, over the mobile network.

GPRS (Global Packet Radio Service) is a step towards this and
promises to deliver data transfer rates of up to 115 kbps. Once this happens,
your cellphone will overcome the bottleneck of 9.6 kbps and 160 characters,
currently faced by circuit-switched data and SMS respectively.

GPRS is a packet-based wireless communication service and
will support the popular IP (Internet Protocol) and the X.25 protocol–a
packet-based protocol mainly used in Europe. It’ll supplement today’s
circuit-switched data and short message service, and would also support
simultaneous voice and data communication. So, you’ll be able to make or
receive calls even while you’re in the midst of a data session, transferring
huge files. In other words, your cellphone will be able to multitask.

The packet-based nature of GPRS would make it possible for
network and mobile operators to make the best use of network and radio
resources. Multiple users will be able to share the same radio channel, as it
would use the radio link only for the duration of time that’s used to send and
receive data, and not for the entire duration connected. This in turn will prove
to be very cost effective, as users would pay only for the amount of transferred
or received data and not for the idle time. The best part of this is that you
could stay connected for hours together, without worrying about costs, or
requiring to dial-in every time you wish to send or receive data. This could
lead to the development of a new breed of mobile Internet access devices that
would use GPRS and the cellphone network.

On the other hand, due to the high throughput offered by GPRS
and its packet-based nature, a host of new applications will be available on
your mobile handset. Multimedia on the cellphone would become a reality. The
applications could include full blown e-mail, browsing, chat,
video-conferencing, stock quotes, FTP and multimedia games… Basically the idea
here is to get all the Internet applications, which you are currently able to
use on your desktop machine onto your cellular phone. In addition you could also
make use of graphics-intensive map applications to navigate, and access your
company intranet, etc, on your mobile device.

All this would obviously require modifications on the
existing GSM network. Let’s take a look at some of these. First of all, in
place of today’s cellphone, you’ll need a GPRS device, which is able to
handle higher data transfer rates and is also able to packetize data. Current
handsets lack this capability.

In today’s cellular network, next comes the BSS (Base
Station Subsystem) that comprises the BTS (Base Transceiver Station) and BSC
(Base Station Controller). The BTS handles radio link protocols with the mobile
stations, and the BSC manages radio resources for one or two BTS. So, in all the
BSS controls the radio link with the mobile handset. It’s also the connection
point between the mobile station and the MSC. The MSC or the Mobile Switching
Center includes the functionality needed to handle a mobile subscriber, such as
registration, authentication, location updating, etc. It also provides
connection to fixed networks, like PSTN, etc.

Now for GPRS to be enabled, the BTS and BSC would require a
software upgrade. In addition, the BSC would require a new piece of hardware
called the PCU (Packet Control Unit), which would direct data traffic to the
GPRS network.

Thus, when voice or data traffic originates at the subscriber
terminal, it’ll be transported (over the air) to BTS and from the BTS to the
BSC. At the BSC, data and voice will be separated and handled separately. Voice
will be sent to the MSC (Mobile Switching Center) and data to a new node called
the SGSN via the PCU.

Current MSCs are not able to handle packet data. So, two new
GPRS support nodes–SGSN (Serving GPRS Support Node) and GGSN (Gateway GPRS
Support Node) –will have to be added.

The SGSN will keep track of the location of GPRS users,
process registrations for new subscribers, etc, and would also deliver packets
to subscriber terminals. The SGSN in turn will be connected to the GGSN, which
will be the connection point between various external IP networks such as the
Internet, intranets, or other mobile service provides’ GPRS services, etc.
Thus, the SGSN will receive packets from the mobile station. These packets would
be passed over to the GGSN, which in turn will pass these packets to other
networks, and vice versa.

Is GPRS the ultimate answer to the mobile bandwidth problem?
No. Today, GPRS is seen as an evolutionary step towards EDGE (Enhanced Data GSM
Environment) and UMTS (Universal Mobile Telephone System). Once these two step
in, one can expect much higher data transfer rates, up to 2 Mbps with mobile
devices, but much depends on the success of GPRS.

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