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Your advert here!!! Our Guides Technical Editors:
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What is GPRS?
The name, General
Packet Radio Service (GPRS) doesn't convey much information to the non-technical
user. Describing it as providing a direct link into the Internet from a GSM
phone, is much clearer. GPRS is to mobile networks what ADSL (Asymmetric Digital
Subscriber Line) is to fixed telephone networks - the favoured solution for
providing fast and inexpensive Internet links. GPRS has come about
because the way mobile networks currently handle data is highly inefficient. At
present, in order to send or receive emails; transfer files or browse WAP/Web
sites, it is first necessary to make a 'data' call. The call is answered by a
modem or an ISDN adapter owned either by the network operator itself (such as BT
Cellnet) or by an Internet Service Provider (ISP). Next the caller is
'authenticated' by giving a user ID and password and then assigned an Internet
address by the ISP or operator. The whole process can take up to sixty seconds
or more and even at the end of this procedure the connection is slow - normally
a mere 9.6 Kbit/s. With GPRS, there is
no call. Once the handset is powered on, by pressing a button the user is
connected directly to the Internet. The link is only broken
when the handset is turned off -
hence GPRS is known as an 'always on' connection. The fact that the link
is continuous has one major benefit. It enables the ISP/operator to know a
handset's Internet address. So messages can be passed directly over the Internet
from a PC, for example, down to your handset. Crucially this facility enables
the Internet Service Provider to 'push' messages down to your handset - rather
like an SMS message. The difference is that with GPRS the link is interactive.
That means if you want to respond directly - such as instruct your broker to
sell 500 shares - you can. One of the major criticisms aimed at WAP is that it
lacked support for 'push' technologies. This failing has effectively been
rectified via an update to the WAP standards (version 1.2) and the introduction
of GPRS enabled WAP handsets. GPRS will undoubtedly
speed up a handset's Internet connection - but it remains to be seen exactly how
much speed can be wrung out of the system. GPRS works by amalgamating
(aggregating) a number of separate data channels. This is feasible because data
is being broken down into small 'packets' which are re-assembled by the
receiving handset back into their original format. The catch is that the number
of receiving channels does not necessarily have to match the number of sending
channels. On the Internet, it is assumed that you want to view more information
(such as a complicated Web page) than you want to send (such as a simple Yes or
No response). So GPRS is an asymmetric technology because the number of
‘down’ channels used to receive data doesn’t match the number of ‘up’
channels used to send data. The task of defining
GPRS has been the responsibility of the Special Mobile Group (SMG) - part of the
3GPP initiative (3rd Generation
Partnership Project). Rather than
wait for the final version of the SMG standard some manufacturers decided to go
with GPRS handsets which conformed to an earlier version of the specifications
known as SMG29. This basically offers two 'down' channels and a single 'up'
channel. In practice each channel is offering around 12-13 Kbit/s so the top
speeds works out to be around 26 Kbit/s. Most experts agree, however that full
interoperability between products will come with SMG 31. This is capable of
offering four 'down' channels which equates to a top speed of around 52 Kbit/s -
the same as a high speed (V.90) landline modem. GPRS is classified as
a 2.5G (or 2G Plus) technology because it builds upon existing network
infrastructure whereas with 3G networks it normally requires building an
entirely new network. In order to compete against 3G networks, therefore, North
American operators have been looking to GPRS to provide high speed data links.
Hence, manufacturers have been working on a related technology known as EDGE
(Enhanced Data for Global Evolution). In order to compete with 3G, EDGE must
offer links running at 384 Kbit/s and originally this equated to running GPRS
three times faster. However, because GPRS has proved much slower than expected,
it now needs to be seven times faster.
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