NISHI BHANU PRATAP SINGH
ELECTRONICS AND COMMUNICATION ENGINEERING
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ABOUT THE INSTITUTE
Advanced Level Telecom Training Centre (ALTTC), Ghaziabad is the apex
training institute of BSNL. An ISO 9001: 2008 accredited institute, ALTTC
was set up as a joint venture of InternationalTelecommunication Union,
Geneva, UNDP and the Governmentof India in 1975. ALTTCfunctions on
the frontiers of telecom technology, finance and management and
imparts training to the leaders in the business. Thestrength of ALTTC lies
in the state of art labs, massiveinfrastructureand trained, talented and
qualified human resourcepool.
The Centre's Mission statement is "To Deliver Excellence Through
The training areas cover vastspectrumof topics such as Digital
Switching and IN, Mobile Communication: GSM, 3G CDMA Data
communication: Broadband and Networking, Optical Networks: SDH,
DWDM, NGN, Access Networks, Management, Telecom Finance,
Information Technology, Building Science (Civil and Electrical) and
Telecom Network Planning.
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The difficulties the international industry standard bodies have had in approving all
of the necessary standards has led to a delay in the deployment of 3G wireless
systems. To lessen the impact of these delays, General Packet Radio Service is being
introduced as an intermediate step to efficiently transport high-speed data over the
current GSM wireless network infrastructures.
GPRS is a packet-based data bearer service for GSM and TDMA networks. It is being
rolled out by operators around the world as the first vital step towards 3G. GPRS
gives mobile users faster data speeds and is particularly suitable for bursty Internet
and intranet traffic. It makes mobile data faster, cheaper and more user-friendly
than ever before. With GPRS-enabled mobile devices, users can be always on the
Mobile Internet, so that, for example, emails arrive instantaneously. It also permits
users to receive calls simultaneously when sending and receiving data calls.
GPRS provides end-to-end IP connectivity that can be used to connect corporate
LANs, ISPs and operators’ own service LANs via interfaces to TCP/IP and X.25. GPRS
gives almost instantaneous connection set-up, and allows charging on the basis of
data transmitted rather than connection time. As a packet data technology, GPRS
only uses network resources and bandwidth when data is actually transmitted. This
makes extremely efficient use of available radio bandwidth. Supported data rates
range from 14.4 Kbps using just one TDMA slot, up to 115 Kbps and higher using all
GPRS can be implemented by simply adding new packet data nodes in GSM/TDMA
networks, and upgrading existing nodes to provide a routing path for packet data
between the mobile terminal and a gateway node. The gateway node provides
interworking with external packet data networks for access to the Internet and
intranets, for example, and requires few or no hardware upgrades to existing
Between 2000 and 2002, upgrades to existing GSM, GPRS and TDMA networks are
planned that will allow single-slot rates of 38.4 Kbit/s for HSCSD and 60 Kbit/s for
GPRS – allowing rates as high as 384 Kbit/s by joining multiple time slots. Known as
Enhanced Data for GSM Evolution (EDGE) these upgrades represent the final
evolution of data communications within the GSM standard and will enable
operators with existing 2G networks to evolve to 3G services on existing network
frequencies, using current network infrastructure. Consequently, EDGE services are
sometimes referred to as 2.5 Generation services.
GPRS is ideal for Wireless Application Protocol (WAP) services. WAP over GPRS
brings cost savings to both mobile operators and consumers, because GPRS radio
resources are only needed while transferring the message. For the end user, that
means you only pay for the time it takes to download. WAP content is optimised for
thin-client devices, such as mobile phones and is also future proof, enabling it to be
deployed on 2.5G, 3G and other networks. While GPRS features efficient use of
resources, instant access, fast delivery of information and innovative charging
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I would like to thank the teachers of Advanced Level Telecom Training
Centre for providing me the golden opportunity to train in such a nice
campus of Ghaziabad .
I am vey grateful to Mr. Manoj Kumar Mishra and Mr. Mukesh Kumar
Arya for their valuable support and guidance.
I am very grateful and thankful to all those who helped me in my entire
training program especially the teachers.
I am indebted to my college training and placement department for
providing me the opportunity of training in ALTTC.
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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 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 infrastructurewhereas with 3G networks it
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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.
GPRS stands for General Packet Radio Service , and is a relatively
low cost technology that offers packet-based radio service and allows
data or information to be sent and received across mobile telephone
networks.Designed to supplement the existing mobile technologies, like
GSM, CDMA, TDMA etc.
WHATDOES GPRS DO?
GPRS provides a permanent connection where information can be
sent or received immediately as the need arises, subject to radio
coverage. No dial-up modem connection is necessary. This is why GPRS
users are sometimes referred to be as being anytime-anywhere "always
connected".The GPRS tariff structure is based on a fixed cost, dependent
on the quantity of data required. In other words customers will be able
to fix their operating costs without the concerns of variable billing.
At present circuit switching technique like your telephone line, 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.
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With packet switching technique 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.
TIMESCALES FOR GPRS :
When a new service is introduced, there are a number of stages
before it becomes established. GPRS service developments will include
standardization, infrastructure development, network trials, contracts
placed, network roll out, availability of terminals, application
development, and so on. These stages for GPRS are:
Throughout1999 –2000 Network operators place trial and
commercial contracts for GPRS
Incorporation of GPRS
Summer of 2000 Firsttrial GPRS services become
available. Typical single user
throughputis likely to be 28 kbps.
For example, T-Mobil is planning a
GPRS trial at Expo2000 in Hanover
in the Summer of 2000
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Start of 2001 Basic GPRS capable terminals begin
to be available in commercial
Throughout2001 Network operators launch GPRS
services commercially and roll out
Vertical market and executive GPRS
early adopters begin using it
regularly for nonvoice mobile
2001/2 Typical single user throughputis
likely to be 56 kbps. New GPRS
specific applications, higher
bitrates, greater network capacity
solutions, morecapable terminals
become available, fuelling GPRS
2002 Typical single user throughputis
likely to be 112 kbps.
GPRS Phase 2/EDGE begins to
emerge in practice
2002/3 3GSMarrives commercially
Like the GSM standard itself, GPRS will be introduced in phases.
Phase 1 is expected to be available commercially in the year 2000/1.
Point to Point GPRS (sending information to a single GPRS user) will be
supported, but not Point to Multipoint (sending the same information to
several GPRS users at the same time). GPRS Phase 2 is not yet fully
defined, but is expected to support higher data rates through the
possibleincorporation of techniques such as EDGE (Enhanced Data rates
for GSM Evolution), in addition to Point-to-Multipoint support.
2. FEATURES OF GPRS
2.1 KEY USER FEATURES OF GPRS :
The General Packet Radio Service (GPRS) is a new nonvoice value
added service that allows information to be sent and received across a
mobile telephone network. It supplements today's Circuit Switched Data
and Short Message Service. GPRS is NOT related to GPS (the Global
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Positioning System), a similar acronym that is often used in mobile
contexts. GPRS has several unique features which can be summarized as:
Theoretical maximum speeds of up to 171.2 kilobits per second
(kbps) are achievable with GPRS using all eight timeslots at the same
time. This is about three times as fast as the data transmission speeds
possible over today's fixed telecommunications networks and ten times
as fast as current Circuit Switched Data services on GSM networks. By
allowing information to be transmitted more quickly, immediately and
efficiently across the mobile network, GPRS may well be a relatively less
costly mobile data service compared to SMS and Circuit Switched Data.
GPRS facilitates instant connections whereby information can be
sent or received immediately as the need arises, subject to radio
coverage. No dial-up modem connection is necessary. This is why GPRS
users are sometimes referred to be as being "always connected".
Immediacy is one of the advantages of GPRS (and SMS) when compared
to Circuit Switched Data. High immediacy is a very important feature for
time critical applications such as remote credit card authorization where
it would be unacceptable to keep the customer waiting for even thirty
NEW APPLICATIONS, BETTER APPLICATIONS:
GPRS facilitates several new applications that have not previously
been available over GSM networks due to the limitations in speed of
Circuit Switched Data (9.6 kbps) and message length of the Short
Message Service (160 characters). GPRS will fully enable the Internet
applications you are used to on your desktop from web browsing to chat
over the mobile network. Other new applications for GPRS, profiled
later, include file transfer and home automation- the ability to remotely
access and control in-house appliances and machines.
SERVICE ACCESS :
To use GPRS, users specifically need:
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A mobile phone or terminal that supports GPRS (existing GSM
phones do NOT support GPRS)
A subscription to a mobile telephone network that supports GPRS
Use of GPRS must be enabled for that user. Automatic access to
the GPRS may be allowed by some mobile network operators,
others will require a specific opt-in
Knowledgeof how to send and/ or receive GPRS information using
their specific model of mobile phone, including software and
hardware configuration (this creates a customer service
A destination to send or receive information through GPRS.
Whereas with SMS this was often another mobile phone, in the
case of GPRS, it is likely to be an Internet address, since GPRS is
designed to make the Internet fully available to mobile users for
the first time. From day one, GPRS users can access any web page
or other Internet applications- providing an immediate critical
mass of uses.
2.2 KEY NETWORKFEATURES OF GPRS :
PACKET SWITCHING :
GPRS involves overlaying a packet based air interface on the
existing circuit switched GSM network. This gives the user an option to
use a packet-based data service. To supplement a circuit switched
network architecture with packet switching is quite a major upgrade.
However, as we shall see later, the GPRS standard is delivered in a very
elegant manner- with network operators needing only to add a couple of
new infrastructure nodes and making a software upgrade to some
existing network elements.
With GPRS, the information is split into separate but related
"packets" before being transmitted and reassembled at the receiving
end. Packet switching is similar to a jigsaw puzzle- the image that the
puzzlerepresents is divided into pieces at the manufacturing factory and
put into a plastic bag. During transportation of the now boxed jigsaw
from the factory to the end user, the pieces get jumbled up. When the
recipient empties the bag with all the pieces, they are reassembled to
form the original image. All the pieces are all related and fit together,
but the way they are transported and assembled varies. The Internet
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itself is another example of a packet data network, the most famous of
many such network types.
SPECTRUM EFFICIENCY :
Packet switching means that GPRS radio resources are used only
when users are actually sending or receiving data. Rather than
dedicating a radio channel to a mobile data user for a fixed period of
time, the available radio resource can be concurrently shared between
several users. This efficient use of scarce radio resources means that
large numbers of GPRS users can potentially share the same bandwidth
and be served from a single cell. The actual number of users supported
depends on the application being used and how much data is being
transferred. Because of the spectrum efficiency of GPRS, there is less
need to build in idle capacity that is only used in peak hours. GPRS
therefore lets network operators maximize the use of their network
resources in a dynamic and flexible way, along with user access to
resources and revenues.
GPRS should improve the peak time capacity of a GSM network since it
simultaneously allocates scarce radio resources more efficiently by
supporting virtual connectivity immigrates traffic that was previously
sent using Circuit Switched Data to GPRS instead, and reduces SMS
Center and signaling channel loading by migrating some traffic that
previously was sent using SMS to GPRS instead using the GPRS/ SMS
interconnect that is supported by the GPRS standards.
For the first time, GPRS fully enables Mobile Internet functionality
by allowing interworking between the existing Internet and the new
GPRS network. Any service that is used over the fixed Internet today-
File Transfer Protocol (FTP), web browsing, chat, email, telnet- will be as
available over the mobile network because of GPRS. In fact, many
network operators are considering the opportunity to use GPRS to help
become wireless Internet Service Providers in their own right.
The World Wide Web is becoming the primary communications
interface- people access the Internet for entertainment and information
collection, the intranet for accessing company information and
connecting with colleagues and the extranet for accessing customers
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and suppliers. These are all derivatives of the World Wide Web aimed at
connecting different communities of interest. There is a trend away from
storing information locally in specific software packages on PCs to
remotely on the Internet. When you want to check your schedule or
contacts, instead of using something like "Act!", you go onto the Internet
site such as a portal. Hence, web browsing is a very important
application for GPRS.
Because it uses the same protocols, the GPRS network can be viewed as
a sub-network of the Internet with GPRS capable mobile phones being
viewed as mobile hosts. This means that each GPRS terminal can
potentially have its own IP address and will be addressable as such.
SUPPORTS TDMA AND GSM :
It should be noted right that the General Packet Radio Service is
not only a service designed to be deployed on mobile networks that are
based on the GSM digital mobile phone standard. The IS-136 Time
Division Multiple Access (TDMA) standard, popular in North and South
America, will also support GPRS. This follows an agreement to follow the
same evolution path towards third generation mobile phone networks
concluded in early 1999 by the industry associations that support these
two network types.
3 GPRS TERMINALS :-
A complete understanding of the application availability and GPRS
timeline requires understanding of terminal types and availability. The
term "terminal equipment" is generally used to refer to the variety of
mobile phones and mobile stations that can be used in a GPRS
environment; the equipment is defined by terminal classes and types.
Cisco Gateway GPRS Serving Node (GGSN) and data network
components interoperate with GPRS terminals that follow the GPRS
GPRS TERMINAL CLASSES :
A GPRS terminal can be one of three classes: A, B, or C. A Class A
terminal supports GPRS and other GSM services (such as SMS and voice)
simultaneously. This support includes simultaneous attach, activation,
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monitor, and traffic. As such, a Class A terminal can make or receive calls
on two services simultaneously. In the presence of circuit-switched
services, GPRS virtual circuits will be held or placed on busy rather than
A Class B terminal can monitor GSM and GPRS channels
simultaneously, but can support only one of these services at a time.
Therefore, a Class B terminal can support simultaneous attach,
activation, and monitor, but not simultaneous traffic. As with Class A,
the GPRS virtual circuits will not be closed down when circuit-switched
traffic is present. Instead, they will be switched to busy or held mode.
Thus, users can make or receive calls on either a packet or a switched
call type sequentially, but not simultaneously.
A Class C terminal supports only nonsimultaneous attach. The user
must select which service to connect to. Therefore, a Class C terminal
can make or receive calls from only the manually (or default) selected
service. The service that is not selected is not reachable. Finally, the
GPRS specifications state that support of SMS is optional for Class C
DEVICE TYPES :
In addition to the three variables, each handset will have a unique
form factor. Some of the form factors will be similar to current mobile
wireless devices, while others will evolve to use the enhanced data
capabilities of GPRS.
The earliest available type will be closely related to the current
mobile phone. These will be available in the standard form factor with a
numeric keypad and a relatively small display.
PC Cards are credit card-sized hardware devices that connect via a
serial cable to the bottom of a mobile phone. Data cards for GPRS
phones will enable laptops and other devices with PC Card slots to be
connected to mobile GPRS-capable phones. Card phones provide
functionality similar to that offered by PC Cards, without needing a
separate phone. These devices may need an earpiece and microphone
to support voice services.
Smart phones are mobile phones with built-in voice, nonvoice,
and Web-browsing services. Smart phones integrate mobile computing
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and mobile communications into a single terminal. They come in various
form factors, which may include a keyboard or an icon drive screen. The
Nokia 9000 series is a popular example of this form factor.
The increase in machine-to-machine communications has led to
the adoption of application-specific devices. These "black-box" devices
lack a display, keypad, and voice accessories of a standard phone.
Communication is accomplished through a serial cable. Applications such
as meter reading utilize such black-box devices.
Personal digital assistants (PDAs) such as the Palm Pilot series or
Handspring Visor are data-centric devices that are adding mobile
wireless access. These devices can either connect with a GPRS-capable
mobile phone via a serial cable or have GPRS capability built in.
4 GPRS ARCHITECTURE : -
From a high level, GPRS can be thought of as an overlay network
onto a second-generation GSM network. This data overlay network
provides packet data transport at rates from 9.6 to 171 kbps.
Additionally, multiple users can share the same air-interface resources.
GPRS attempts to reuse the existing GSM network elements as
much as possible, but in order to effectively build a packet-based mobile
cellular network, somenew network elements, interfaces, and protocols
that handle packet traffic are required. Therefore, GPRS requires
modifications to numerous network elements, as summarized in
following Table and illustrated in following Figure.
MODIFICATIONS REQUIRED FOR GPRS :
Modification or UpgradeRequired for GPRS
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A totally new subscriber terminal is required to access
GPRS services. These new terminals will be backward
compatible with GSMfor voice calls.
BTS A softwareupgradeis required in the existing base
transceiver site (BTS).
BSC The base station controller (BSC) will also require a
softwareupgrade, as well as the installation of a new
piece of hardwarecalled a packet controlunit (PCU).
The PCU directs the data traffic to the GPRS network
and can be a separate hardwareelement associated
with the BSC.
Core Network The deployment of GPRS requires the installation of
new corenetwork elements called the Serving GPRS
SupportNode (SGSN) and Gateway GPRS SupportNode
and so on)
All the databases involved in the network will require
softwareupgrades to handle the new call models and
functions introduced by GPRS.
Generic GPRS Network Architecture
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GPRS SUBSCRIBER TERMINALS :
New terminals (TEs) are required because existing GSM phones do
not handle the enhanced air interface, nor do they have the ability to
packetize traffic directly. A variety of terminals will exist, as described in
a previous section, including a high-speed version of current phones to
support high-speed data access, a new kind of PDA device with an
embedded GSM phone, and PC Cards for laptop computers. All these TEs
will be backward compatiblewith GSM for making voice calls using GSM.
GPRS BSS :
Each BSC will require the installation of one or more PCUs and a
softwareupgrade. The PCU provides a physical and logical data interface
out of the base station system (BSS) for packet data traffic. The BTS may
also require a software upgrade, but typically will not require hardware
When either voice or data traffic is originated at the subscriber
terminal, it is transported over the air interface to the BTS, and from the
BTS to the BSC in the same way as a standard GSM call. However, at the
output of the BSC the traffic is separated; voice is sent to the mobile
switching center (MSC) per standard GSM, and data is sent to a new
device called the SGSN, via the PCU over a Frame Relay interface.
GPRS NETWORKS NODE:
In the core network, the existing MSCs are based upon circuit-
switched central-office technology, and they cannot handle packet
traffic. Thus two new components, called GPRS Support Nodes, are
Serving GPRS Support Node (SGSN)
Gateway GPRS Support Node (GGSN)
The SGSN can be viewed as a "packet-switched MSC;" it delivers
packets to mobile stations (MSs) within its service area. SGSNs send
queries to home location registers (HLRs) to obtain profile data of GPRS
subscribers. SGSNsdetectnew GPRS MSs in a given servicearea, process
registration of new mobile subscribers, and keep a record of their
location inside a given area. Therefore, the SGSN performs mobility
management functions such as mobile subscriber attach/detach and
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location management. The SGSN is connected to the base-station
subsystem via a Frame Relay connection to the PCU in the BSC.
GGSNs are used as interfaces to external IP networks such as the
public Internet, other mobile service providers' GPRS services, or
enterprise intranets. GGSNs maintain routing information that is
necessary to tunnel the protocol data units (PDUs) to the SGSNs that
service particular MSs. Other functions include network and subscriber
screening and address mapping. One (or more) GGSNs may be provided
to support multiple SGSNs. More detailed technical descriptions of the
SGSN and GGSN are provided in a later section.
Enabling GPRS on a GSM network requires the addition of two
core modules, the Gateway GPRS Service Node (GGSN) and the Serving
GPRS Service Node (SGSN). As the word Gateway in its name suggests,
the GGSN acts as a gateway between the GPRS network and Public Data
Networks such as IP and X.25. GGSNs also connect to other GPRS
networks to facilitate GPRS roaming. The Serving GPRS Support Node
(SGSN) provides packet routing to and from the SGSN service area for all
users in that service area.
In addition to adding multiple GPRS nodes and a GPRS backbone,
some other technical changes that need to be added to a GSM network
to implement a GPRS service. These include the addition of Packet
Control Units; often hosted in the Base Station Subsystems, mobility
management to locate the GPRS Mobile Station, a new air interface for
packet traffic, new security features such as ciphering and new GPRS
GPRS MOBILITY MANAGEMENT:
Mobility management within GPRS builds on the mechanisms
used in GSM networks; as a MS moves from one area to another,
mobility management functions areused to track its location within each
mobile network. The SGSNs communicate with each other and update
the user location. The MS profiles are preserved in the visitor location
registers (VLRs) that are accessible by the SGSNs via the local GSM MSC.
A logical link is established and maintained between the MS and the
SGSN in each mobile network. At the end of transmission or when a MS
moves out of the area of a specific SGSN, the logical link is released and
the resources associated with it can be reallocated.
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A final category of GPRS terminals is handheld communications.
Again, these are primarily data-centric devices that are adding mobile
wireless access. Access can be gained via a PC Card or via a serial cable
to a GPRS-capable phone.
5 HOW GPRS WORKS : -
The General Packet Radio Service is Mobile Data upgrade to a
GSM mobile phone network. This provides users with packet data
services (similar to the Internet) using the GSM digital radio network.
Each voice circuit in GSM transmits the speech on a secure14kbps digital
radio link between the mobile phone and a nearby GSM transceiver
station. The GPRS service joins together multiple speech channels to
provide higher bandwidth data connections for GPRS data users. The
radio bandwidth remains the same, it is just shared between the voice
users and the data users. The network operator has the choice of
prioritizing one or the other.
GPRS users will also benefit frombeing able to useGPRS while
traveling as the GSMsystemshould transparently hand over the GPRS
connection fromone base station to another.
Each GSM radio transceiver uses Time Division Multiplexing to
deliver eight voice circuits on one radio channel. Each radio site may
have one or more transceivers to provide sufficient channels to end
users (maximum numbers are limited by many factors including -
operators radio license, interference with other nearby GSM cells, cost
of equipment, capacity of radio site infrastructure etc.)
A GPRS user may theoretically use all voice channels on one
transceiver - (8 * 14 kbps) but radios to support this are not available
and the operators will probably reserve at least some channels for voice
Each 14kbps channel may be shared by multiple 'connected' GPRS
users (many users will be connected to the network but transmitting
very little data). As a user's data requirements grow, they will use more
of the available capacity within that timeslot, and then more available
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timeslots up to the maximum available or the maximum supported by
In general the higher the data rate, the more power the mobile
device will use and the shorter the battery life and the higher the
transmitted RF power. If you areusing GPRS with a mobile phone, do not
keep it near your ear for long periods while data transfers are taking
GPRS MOBILEDEVICES :
The key use for GPRS is to send and receive data to a computer
application such as Email, web browsing or even telemetry (telemetry
refers to devices not being controlled by humans such as cash point
machines or traffic monitoring cameras etc.). To use GPRS the service is
'dialed' in a similar manner to a standard data call (though there is no
phone no.) at which point the user is 'attached' and an IP address is
allocated. From then on data can flow to and from the Internet until
either the network unattaches you (maybe because of a time-out, fault
or congestion) or you manually unattach.
Mobile workers usually havea mobile phone, when this includes
GPRS then it can also be used to transfer data to an connected
Some of the key issues are:
Using GPRS will not stop you making or receiving voice calls.
Currentphones will usually suspend the data session while
a voice call takes place.
Battery life will be reduced when using GPRS.
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The data needs to be connected with your computer.
The three standardmethods toconnect your computer to GPRS mobile
Infrared - available on most business mobile phones - just
align the IR. port on the phone with the IR. port on the
Data-cable - reliable and doesn't require the careful
alignment of IR. which may be difficult when traveling
Bluetooth - My preferred solution - often difficult to set up
but once its configured Bluetooth provides a very
convenient connection. Bluetooth is available for
connecting to Laptops via USB, PC-cards or CF-cards in
addition to cards for PDAs such as those offered by PALM.
Older Compaq IPAQs will require an expansion jacket but
newer Pocket PC devices usually include a suitable
expansion port (check at the time of purchase). One very
important point is that Bluetooth devices are very low
powered so do not drain your computer battery or phone
battery too much. Many people will be tempted by the all-
in-one phone/PDA, but consider will you be happy with the
relatively short battery life, large size and weight and
unreliability of many PocketPC devices.
GPRS data cards are also available, the issues here are:
Fully integrated solution
Best in Laptops with PC card expansion slots
GPRS will drain your battery so expect reduced life
You can subscribe to a different network than your GSM
GPRS data cards will havetheir own SIM card and hence will
need another subscription to your mobile network
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GPRS ROAMING :
In the short term don't expect to be able to roam to many
countries with GPRS, many networks are still negotiating to set up
roaming agreements. Technically there are two type of GPRS Roaming
Home Network Roaming - Here all data is transmitted from
wherever you connect to a GPRS network to your home
GPRS network where it is connected to the Internet or your
company LAN as if you were indeed in your home country.
Local Network Roaming - Data is just connected to a local
Internet connection point and will be subject to local
conditions for security and performance.
GPRS users would be advised to ensure they also are able to use
either GSM or High Speed GSM data (HSCSD) to retrieve their data when
traveling because of the changing state of GPRS roaming agreements.
They can either phone their ISP or RAS server on their home network or
subscribe to an ISP which provides local access points in each country
GPRS SECURITY :
The radio interface is considered to be relatively secure being
controlled by the GSM network's security - (SIM card + HLR). Security
issues arise when data needs to leave the GPRS network to be delivered
to either the Internet or a company LAN.
Internetconnectivity is the cheapest and mostcommon - and here
you can take charge of security by encrypting sensitive data. If your
GPRS network supplier allows it you can set up encrypted VPN
connections to your company systems - though there could be a
performance hit. Treat the connection as a standard dial-up Internet
connection to an ISP and take similar security precautions.
As a business GPRS user you will have a choice of methods to
connect to the GPRS network - by far the most common method will be
via the Internet. For larger users you may connect your company LAN to
the GPRS networks using leased lines or Frame Relay virtual circuits.
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Your company probable already has an Internet connection
(though you may need more capacity if you add many GPRS users) and
this provides a quick and easy way of connection to GPRS.
The key problem is to deliver your data SECURELY to your users,
using strong encryption such as with SSL (128 bit) or VPN (162 bit).
For secure company Email access youhave a number of choices. These
VPN firewalls - this will provide secure access to everything
on the company LAN from GPRS and other Internet users.
Microsoft Mobile Information Server
WAP interfaces to your Email system e.g. Peramon
POP server - set up a company POP server to provide
Internet based Email, make sure to enable additional
security if required.
Employees (often senior managers) often bypass a companies
security systems by redirecting to personal Internet Email accounts
which provides them with a quick fix to mobile connectivity.
LEASED LINES :
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Leased lines provide the most secure method of connecting to
GPRS but are traditionally expensive and have long contract periods.
(Min 1 year)
The protocol over the leased line would normally be frame relay
but it is possible you could use ATM with some networks. You do not
really need any CPE (Customer Premises Equipment) supplied by your
GPRS network supplier, just a spare Frame relay port on an existing
router. There may be economies to be made if you also use the leased
line to carry standard voice and data and bulk SMS in addition to the
GPRS traffic - in which case your network supplier will provide a device
to route these onto your network. They may also try to sell you
consultancy to design this interface - shop around to get the best
Keep costs down by connecting to a geographically close
connection point to the chosen GPRS network. Not all networks have the
same number and location of connection points (GGSNs in GPRS terms).
If you already have a frame relay connection with one of the key
UK network suppliers then adding an addition PVC (Private Virtual
Circuit) to one of the GPRS networks will make a cost effective solution,
even if you have to increase the size of the link.
Ask your network supplier about availability figures as it is
important they have redundant connections to the chosen Frame
6 GPRS DATA COMMUNICATION:-
Some cooperation still exists between elements of the current
GSM services and GPRS. On the physical layer, resources can be reused
and somecommon signaling issues exist. In the same radio carrier, there
can be time slots (TSs) reserved simultaneously for circuit-switched and
GPRS use. The most optimum resource utilization is obtained through
dynamic sharing between circuit-switched and GPRS channels. During
the establishment of a circuit-switched call, there is enough time to
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preempt the GPRS resources for circuit-switched calls that have higher
GPRS SERVICE :
The GPRS provides a bearer service from the edge of a data
network to a GPRS MS. The GPRS protocol layering is illustrated in Figure
shown below. The physical radio interface consists of a flexible number
of TDMA time slots (from 1 to 8) and thus provides a theoretical raw
data rate of 171 kbps. A Media Access Control (MAC) utilizes the
resources of the physical radio interface and provides a service to the
GPRS Logical Link Control (LLC) protocol between the MS and the serving
GSN (SGSN). LLC is a modification of a High-Level Data Link Control
(HDLC)-based Radio Link Protocol (RLP) with variable frame size. The two
most important features offered by LLC are the support of point-to-
multipoint addressing and the control of data frame retransmission.
From the standpoint of the application, GPRS provides a standard
interface for the network layer.
Figure : GPRS Protocol Layering
DATA ROUTING :
One of the main issues in the GPRS network is the routing of data
packets to/from a mobile user. The issue can be divided into two areas:
data packet routing and mobility management.
DATA PACKET ROUTING :
The main functions of the GGSN involve interaction with the
external data network. The GGSN updates the location directory using
routing information supplied by the SGSNs about the location of a MS
and routes the external data network protocol packet encapsulated over
the GPRS backbone to the SGSN currently serving the MS. It also
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decapsulates and forwards external data network packets to the
appropriatedata network and collects charging data that is forwarded to
a charging gateway.
In following Figure, three different routing schemes are
illustrated: mobile-originated message (path 1), network-initiated
message when the MS is in its home network (path 2), and network-
initiated message when the MS has roamed to another GPRS operator's
network (path 3). In these examples, the operator's GPRS network
consists of multiple GSNs (with a gateway and serving functionality) and
an intra-operator backbone network.
GPRS operators will allow roaming through an inter-operator
backbone network. The GPRS operators connect to the inter-operator
network via a boarder gateway (BG), which can provide the necessary
interworking and routing protocols (for example, Border Gateway
Protocol [BGP]). It is also foreseeable that GPRS operators will
implement QoS mechanisms over the inter-operator network to ensure
service-level agreements (SLAs). The main benefits of the architecture
are its flexibility, scalablility, interoperability, and roaming.
Figure : Routing of DataPackets betweenaFixedHost and a GPRS MS
The GPRS network encapsulates all data network protocols into its
own encapsulation protocol, called the GPRS Tunneling Protocol (GTP),
as shown in above Figure. This is done to ensure security in the
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backbone network and to simplify the routing mechanism and the
delivery of data over the GPRS network.
GPRS MOBILITY MANAGEMENT:
The operation of the GPRS is partly independent of the GSM
network. However, some procedures share the network elements with
current GSM functions to increase efficiency and to make optimum use
of free GSM resources (such as unallocated time slots).
Figure : States of GPRS in a Mobile Station
An MS has three states in the GPRS system: idle, standby, and
active . The three-state model represents the nature of packet radio
relative to the GSM two-state model (idle or active).
Data is transmitted between a MS and the GPRS network only
when the MS is in the active state. In the active state, the SGSN knows
the cell location of the MS. However, in the standby state, the location
of the MS is known only as to which routing area it is in. (The routing
area can consist of one or more cells within a GSM location area.)
When the SGSN sends a packet to a MS that is in the standby
state, the MS must be paged. Because the SGSN knows the routing area
in which the MS is located, a packet paging message is sent to that
routing area. After receiving the packet paging message, the MS gives its
cell location to the SGSN to establish the active state.
Packet transmission to an active MS is initiated by packet paging
to notify the MS of an incoming data packet. The data transmission
proceeds immediately after packet paging through the channel indicated
by the paging message. The purpose of the packet paging message is to
simplify the process of receiving packets. The MS has to listen to only the
packet paging messages, instead of all the data packets in the downlink
channels, reducing battery use significantly.
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When an MS has a packet to be transmitted, access to the uplink
channel is needed. The uplink channel is shared by a number of MSs, and
its use is allocated by a BSS. The MS requests use of the channel in a
packet random access message. The transmission of the packet random
access message follows Slotted Aloha procedures. The BSS allocates an
unused channel to the MS and sends a packet access grant message in
reply to the packet random access message. The description of the
channel (one or multiple time slots) is included in the packet access
grant message. The data is transmitted on the reserved channels.
The main reasons for the standby state are to reduce the load in
the GPRS network caused by cell-based routing update messages and to
conserve the MS battery. When a MS is in the standby state, there is no
need to inform the SGSN of every cell change—only of every routing
area change. The operator can define the size of the routing area and, in
this way, adjust the number of routing update messages.
In the idle state, the MS does not have a logical GPRS context
activated or any Packet-Switched Public Data Network (PSPDN)
addresses allocated. In this state, the MS can receive only those
multicast messages that can be received by any GPRS MS. Because the
GPRS network infrastructure does not know the location of the MS, it is
not possible to send messages to the MS from external data networks.
A cell-based routing update procedure is invoked when an active
MS enters a new cell. In this case, the MS sends a short message
containing information about its move (the message contains the
identity of the MS and its new location) through GPRS channels to its
current SGSN. This procedure is used only when the MS is in the active
When an MS in an active or a standby state moves from one
routing area to another in the service area of one SGSN, it must again
perform a routing update. The routing area information in the SGSN is
updated and the success of the procedure is indicated in the response
The inter-SGSN routing update is the most complicated of the
three routing updates. In this case, the MS changes from one SGSN area
to another, and it must establish a new connection to a new SGSN. This
28 | P a g e
means creating a new logical link context between the MS and the new
SGSN, as well as informing the GGSN about the new location of the MS.
7 GPRS SOLUTION : -
The GGSN network element, while the SGSN solution is available
through Cisco partners.
GGSN OVERVIEW :
GGSN combines in one box:
GGSN features as defined by the European Telecommunication
Standards Institute (ETSI)
Value-added networking functionality of Cisco routers
The GGSN functionality embedded in the Cisco IOS®
software is what
differentiates the Cisco GGSN. The Cisco IOS software within a GGSN
provides a sophisticated suite of networking capabilities that reside at
the heart of internetworking devices. These capabilities provide
interoperability with more standards-based physical and logical protocol
interfaces than any other internetworking solutions. They connect
otherwise-disparate hardware and provide security, reliability, and
investment protection in the face of network growth, change, and new
The Cisco GGSN is compliant with ETSI's GPRS standards. Key GPRS
features supported by GGSNinclude GPRS-defined routing and transfers,
mobility management in conjunction with SGSN, GPRS quality-of-service
(QoS) classes mapping to Internet QoS, QoS negotiation and handling,
mobile authentication through Remote Authentication Dial-In User
Service (RADIUS), dynamic IP addressing through Dynamic Host
Configuration Protocol(DHCP), network management, and charging data
collection. The Cisco GGSN supports all Cisco IOS features. A partial list
of supported Cisco IOS features within GGSN includes IP routing, IP
tunneling, and support of the Domain Name System (DNS), DHCP, and
RADIUS. Additional technical information can be found in the Cisco
GGSN data sheet.
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GGSN APPLICATIONS :
The GGSN can be deployed in a variety of network topologies and
architectures. The following sections illustrate several alternatives.
Operators of a standalone Public Land Mobile Network (PLMN)
who own the frequency may have one or more SGSNs and GGSNs. The
GGSN serves as a gateway to the Internet (external packet data
network). (See in following Figure.)
Figure : The CiscoGPRS solutionenables GSM operators toprovide
packet data service totheir mobile subscribers.
WAP SERVICES IN GPRS ENVIRONMENT:
The Wireless Access Protocol (WAP) empowers mobile users of
wireless devices to easily access live interactive information services and
applications from the screens of mobile phones. Services and
applications include e-mail, customer care, call management, unified
messaging, weather and traffic alerts, news, sports and information
services, electronic commerce transactions and banking services, online
address book and directory services, as well as corporate intranet
WAP utilizes HTTP 1.1 Web servers to provide content on the
Internet or intranets, thereby taking advantage of existing application
development methodologies and developer skill sets such as CGI, ASP,
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NSAPI, JAVA, and Servlets. WAP defines an XML (eXtensible Markup
Language) syntax called WML (Wireless Markup Language). All WML
content is accessed over the Internet using standard HTTP 1.1 requests.
To take advantage of today's extremely large market penetration
of mobile devices, the user interface components of WML map well onto
existing mobile phone user interfaces. This means end users can
immediately use WAP-enabled mobile phones and services without re-
education. WAP specifications enable products which employ standard
Internet technology to optimize content and airlink protocols to better
suit the characteristics and limitations of existing and future wireless
networks and devices. Since WAP transport is based on IP, Cisco can
provide all the required features and products to scale mass market
WAP applications.(see in following figure)
Figure : SN in a WAP enablednetwork
FAXOVER GPRS :
Faxes are ubiquitous—and inexpensive compared to postage. Not
only are faxes fast and easy to use, they provide immediate and reliable
confirmation that a remote fax machine received the message. In parts
of the developing world, fax is a lifeline—the only reliable means of
exchanging important business, government, and personal documents.
The fax store-and-forward solution addresses each of these issues
through a combination of Cisco and partner technology (see in following
Integration of fax with electronic documents converts faxes
into Multipurpose Internet Mail Extension (MIME) messages
with attached Tagged Image File Format (TIFF) documents that
can be reconverted to fax or accessed electronically.
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Improved delivery controlis realized through directory services
based on Simple Mail Transfer Protocol (SMTP) mail servers
(provided by Netscape or Software.com) plus directory services
that map fax numbers to user accounts.
Messagestorage and retrieval includies software to convert PC
documents into TIFF documents.
Least-cost routing, billing, management and user access via the
Web is achieved through partner software that enables service
providers to offer store-and-forward fax services profitably.
CORPORATEVOICEAND DATA :
Cisco GGSNenables offering alternative solutions whereGGSNcan
be placed at the customer premises. Based on leading routing
technology, Cisco IOS software, it is the ideal solution that integrates
GPRS with already-deployed IP services, such as virtual private dial-up
networks (VPDNs) and voice over IP (see in following Figure ).
VIRTUAL PRIVATENETWORKCORPORATESOLUTIONS :
High scalable SGSN nodes could be used to create a GPRS
corporate solution. Scalability, interworking features, and standard
protocols are the key aspects that Cisco is introducing in all its innovative
and advanced projects. Distributed solutions with intelligent devices can
give operators a competitive advantage, especially in the small
office/home office (SOHO) business. (see in following Figure).
8 GPRS APPLICATIONS : -
GPRS will enable a variety of new and unique services to the
mobile wireless subscriber. These mobile applications contain several
unique characteristics that enhance the value to the customers. First
among them is mobility—the ability to maintain constant voice and data
communications while on the move. Second is immediacy, which allows
subscribers to obtain connectivity when needed, regardless of location
and without a lengthy login session. Finally, localization allows
subscribers to obtain information relevant to their current location. The
combination of these characteristics provides a wide spectrum of
possible applications that can be offered to mobile subscribers. The core
32 | P a g e
network components offered by Cisco enable seamless access to these
applications, whether they reside in the service provider's network or
the public Internet.
In general, applications can be separated into two high-level
categories: corporate and consumer. These include:
Communications—E-mail; fax; unified messaging;
Value-added services (VAS)—Information services; games
E-commerce—Retail; ticket purchasing; banking; financial
Location-based applications—Navigation; traffic conditions;
airline/rail schedules; location finder
Vertical applications—Freight delivery; fleet management;
Communications applications include all those in which it appears
to the users that they are using the mobile communications network
purely as a pipe to access messages or information. This differs from
those applications in which users believe that they are accessing a
service provided or forwarded by the network operator.
The first stage of enabling users to maintain contact with their
office is through access to e-mail, fax, and voice mail using unified
messaging systems. Increasingly, files and data on corporate networks
are becoming accessible through corporate intranets that can be
protected through firewalls, by enabling secure tunnels (virtual private
As a critical mass of users is approached, more and more
applications aimed at general consumers are being placed on the
Internet. The Internet is becoming an invaluable tool for accessing
corporate data as well as for the provision of product and
service information. More recently, companies have begun using the
33 | P a g e
Internet as an environment for carrying out business, through e-
E-MAIL AND FAX:
E-mail on mobile networks may take one of two forms. It is
possible for e-mail to be sent to a mobile user directly, or users can have
an e-mail account maintained by their network operator or their
Internet service provider (ISP). In the latter case, a notification will be
forwarded to their mobile terminal; the notification will include the first
few lines of the e-mail as well as details of the sender, the date/time,
and the subject. Fax attachments can also accompany e-mails.
UNIFIED MESSAGING :
Unified messaging uses a single mailbox for all messages, including
voice mail, faxes, e-mail, short message service (SMS), and pager
messages. With the various mailboxes in one place, unified messaging
systems then allow for a variety of access methods to recover messages
of different types. Some will use text-to-voice systems to read e-mail
and, less commonly, faxes over a normal phone line, while most will
allow the interrogation of the contents of the various mailboxes through
data access, such as the Internet. Others may be configured to alert the
user on the terminal type of their choice when messages are received.
VALUE-ADDED SERVICES :
Value-added services refer strictly to content provided by network
operators to increase the value of their service to their subscribers. Two
terms that are frequently used with respect to the delivery of data
applications are push and pull, as defined below.
Push refers to the transmission of data at a predetermined
time, or under predetermined conditions. It could also apply to
the unsolicited supply of advertising (for example, delivery of
news as it occurs, or stock values when they fall below a preset
Pull refers to the demanding of data in real time by the user
(for example, requesting stock quotes or daily news headlines).
To be valuable to subscribers, this content must posses several
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Personalized information is tailored to user-specific needs
with relevant information. A stock ticker, focusing on key quotes
and news, or an e-commerce application that knows a user's
profile are two examples of personalized information.
Localized content is based on a user's current location; it
can include maps, hotel finders, or restaurant reviews.
Convenience suggests that the user interface and menu
screens are intuitive and easy to navigate.
Trust pertains primarily to e-commerce sites where the
exchange of financial or other personal information is required.
E-commerce is defined as the carrying out of business on the
Internet or data service. This would include only those applications
where a contract is established over the data connection, such as for the
purchase of goods, or services, as well as online banking applications
because of the similar requirements of user authentication and secure
transmission of sensitive data.
The popularity among banks of encouraging electronic banking
comes from the comparable costs of making transactions in person in a
bank to making them electronically. Specific banking functions that can
be accomplished over a wireless connection include: balance checking,
moving money between accounts, bill payment, and overdraft alert.
FINANCIAL TRADING :
The immediacy with which transactions can be made using the
Internet and the requirement for up-to-the-minute information has
made the purchasing of stocks a popular application. By providing push
services such as those detailed in the VAS section earlier and coupling
these with the ability to make secure transactions from the mobile
terminal, a very valuable service unique to the mobile environment can
LOCATION-BASED SERVICES AND TELEMATICS :
Location-based services provide the ability to link push or pull
information services with a user's location. Examples include hotel and
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restaurant finders, roadside assistance, and city-specific news and
information. This technology also has vertical applications such as
workforce management and vehicle tracking.
VERTICAL APPLICATIONS :
In the mobile environment, vertical applications apply to systems
utilizing mobile architectures to supportthe carrying outof specific tasks
within the value chain of a company, as opposed to applications that are
then being offered for sale to a consumer. Examples of vertical
Sales support—Provision of stock and product information
for sales staff, as well as integration of their use of appointment
details and the remote placing of orders
Dispatching—Communication of job details such as location
and scheduling; permitting interrogation of information to support
Fleet management—Control of a fleet of delivery or service
staff, monitoring their locations and scheduling work
Parcel delivery—Tracking the locations of packages for
feedback to customers and performance monitoring
Advertising services will be offered as a push type information
service. Advertising may be offered to customers to subsidize the cost of
voice or other information services. Finally, advertising may be location
sensitive where, for example, a user entering a mall would receive
advertising specific to the stores in that mall.
9 LIMITATIONS OF GPRS : -
It should already be clear that GPRS is an important new enabling
mobile data service which offers a major improvement in spectrum
efficiency, capability and functionality compared with today's nonvoice
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mobile services. However, it is important to note that there are some
limitations with GPRS, which can be summarized as:
LIMITED CELL CAPACITY FOR ALL USERS :
GPRS does impact a network's existing cell capacity. There are
only limited radio resources that can be deployed for different uses- use
for one purpose precludes simultaneous use for another. For example,
voice and GPRS calls both use the same network resources. The extent
of the impact depends upon the number of timeslots, if any, that are
reserved for exclusive use of GPRS. However, GPRS does dynamically
manage channel allocation and allow a reduction in peak time signalling
channel loading by sending short messages over GPRS channels instead.
RESULT: NEED FOR SMS as a complementary bearer that uses a different
type of radio resource.
SPEEDS MUCH LOWER IN REALITY :
Achieving the theoretical maximum GPRS data transmission speed
of 172.2 kbps would require a single user taking over all eight timeslots
without any error protection. Clearly, it is unlikely that a network
operator will allow all timeslots to be used by a single GPRS user.
Additionally, the initial GPRS terminals are expected be severely limited-
supporting only one, two or three timeslots. The bandwidth available to
a GPRS user will therefore be severely limited. As such, the theoretical
maximum GPRS speeds should be checked against the reality of
constraints in the networks and terminals. The reality is that mobile
networks are always likely to have lower data transmission speeds than
RESULT: Relatively high mobile data speeds may not be available to
individual mobile users until Enhanced Data rates for GSM Evolution
(EDGE) or Universal Mobile Telephone System (3GSM) are introduced.
SUPPORT OF GPRS MOBILETERMINATEBY TERMINALS IS NOT
At the time of writing, there has been no confirmation from any
handset vendors that mobile terminated GPRS calls (i.e. receipt of GPRS
37 | P a g e
calls on the mobile phone) will be supported by the initial GPRS
terminals. Availability or not of GPRS MT is a central question with
critical impact on the GPRS business case such as application migration
from other nonvoice bearers.
By originating the GPRS session, users confirm their agreement to
pay for the delivery of content from that service. This origination may
well be performed using a Wireless Application Protocol (WAP) session
using the WAP microbrowser that will be built into GHPRS terminals.
However, mobile terminated IP traffic might allow unsolicited
information to reach the terminal. Internet sources originating such
unsolicited content may not be chargeable. A possible worse case
scenario would be that mobile users would have to pay for receiving
unsolicited junk content. This is a potential reason for a mobile vendor
NOT to support GPRS Mobile Terminate in their GPRS terminals.
However, there is always the possibility of unsolicited or
unwanted information being communicated through any media, but that
does not mean that we would wish to preclude the possibility of any
kind of communication through that means altogether. A network side
solution such as GGSN or charging platform policing would be preferable
rather than a non-flexible limitation built into all the GPRS handsets.
When we asked Nokia about this issue, it commented: "Details of
the Nokia GPRS terminals are not available at this time. It is too early to
confirm whether MT will be supported in the first Nokia GPRS
terminals". The company's policy is not to make details available about
products before they are announced. Readers should contact the GSM
Association, Mobile Lifestreams Limited and/ or the vendors directly to
encourage them to incorporate support for GPRS MT in their initial
RESULT: GPRS usability and therefore business caseis threatened if GPRS
MT is not supported by GPRS terminals.
SUBOPTIMAL MODULATION :
GPRS is based on a modulation technique known as Gaussian
minimum-shift keying (GMSK). EDGE is based on a new modulation
scheme that allows a much higher bit rate across the air interface- this is
called eight-phase-shift keying (8 PSK) modulation. Since 8 PSK will also
38 | P a g e
be used for 3GSM, network operators will need to incorporate it at some
stage to make the transition to third generation mobile phone systems.
RESULT: NEED FOR EDGE.
GPRS packets are sent in all different directions to reach the same
destination. This opens up the potential for one or some of those
packets to be lost or corrupted during the data transmission over the
radio link. The GPRS standards recognize this inherent feature of
wireless packet technologies and incorporate data integrity and
retransmission strategies. However, the result is that potential transit
delays can occur.
Because of this, applications requiring broadcastquality video may
well be implemented using High Speed Circuit Switched Data (HSCSD).
HSCSD is simply a Circuit Switched Data call in which a single user can
take over up to four separate channels at the same time. Because of its
characteristic of end to end connection between sender and recipient,
transmission delays are less likely.
RESULT: NEED FOR HSCSD.
NO STORE AND FORWARD :
Whereas the Store and Forward Engine in the Short Message
Service is the heart of the SMS Center and key feature of the SMS
service, there is no storage mechanism incorporated into the GPRS
standard, apart from the incorporation of interconnection links between
SMS and GPRS.
RESULT: NEED FOR SMS.
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10 RELATED GPRS CHALLENGES :-
GPRS is a different kind of service from those typically available on
today’s mobile networks. GPRS is essentially a packet switching overlay
on a circuit switching network. The GPRS specifications stipulate the
minimum charging information that must be collected in the Stage 1
service description. These include destination and source addresses,
usage of radio interface, usage of external Packet Data Networks, usage
of the packet data protocol addresses, usage of general GPRS resources
and location of the Mobile Station. Since GPRS networks break the
information to be communicated down into packets, at a minimum, a
GPRS network needs to be able to count packets to charging customers
for the volume of packets they send and receive. Today's billing systems
have difficulties handling charging for today's nonvoice services. It is
unlikely that circuit switched billing systems will be able to process a
large number of new variables created by GPRS.
GPRS call records are generated in the GPRS Service Nodes. The
GGSN and SGSN may not be able to store charging information but this
charging information needs to be processed. The incumbent billing
systems are often not able to handle real time Call Detail Record flows.
As such, an intermediary charging platform is a good idea to and
preparing it for submission to perform billing mediation by collecting the
charging information from the GPRS nodes the billing system. Packet
counts are passed to a Charging Gateway that generates Call Detail
Records that are sent to the billing system.
However, the crucial challenge of being able to bill for GPRS and
therefore earn a return on investment in GPRS is simplified by the fact
that the major GPRS infrastructure vendors all support charging
functions as part of their GPRS solutions. Additionally, a wide range of
other existing non-GSM packet data networks such as X.25 and Cellular
Digital Packet Data (CDPD) are in place along with associated billing
It may well be the case that the cost of measuring packets is
greater than their value. The implication is that there will NOT be a per
packet charge since there may be too many packets to warrant counting
and charging for. For example, a single traffic monitoring application can
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generate tens of thousands of packets per day. Thus the charging
gateway function is more a policing function than a charging function
since network operators are likely to tariff certain amounts of GPRS
traffic at a flat rate and then need to monitor whether these allocations
are far exceeded.
This is not to say that we will end up with the free Internet Service
Provider model that has become established on the fixed Internet in
which users pay no fixed monthly charge and network operators rely on
advertising sales on mobile portal sites to make money. There is a
premium for mobility and there is frankly a shortage of mobile
bandwidth that limits the extent to which that bandwidth is viewed as a
commodity. And given the additional customer care and billing
complexity associated with mobile
Internet and nonvoice services, network operators would be ill
advised to reduce their prices in such a way as to devalue the perceived
value of mobility.
Decisions on charging for GPRS by packet or simply a flat monthly
fee are contentious but need to be made. Charging different packets at
different rates can make things complicated for the user, whilst flat rates
favor heavy users more than occasional ones.
We believe that the optimal GPRS pricing model will be based on
two variables- time and packet. Network operators should levy a
nominal per packet charge during peak times plus a flat rate, no per
packet charge during non peak times. Time and packet related charging
will encourage applications such as remote monitoring, meter reading
and chat to use GPRS overnight when spare network capacity is
available. Simultaneously, a nominal per packet charge during the day
will help to allocate scarce radio resources and charge radio heavy
applications such as file and image transfer more than applications with
lower data intensity. It has the advantage that it will automatically adjust
customer charging according to their application usage.
As such the optimal charging model could well be a flat rate charge
during off-peak times along with a per packet charge during peak times.
CUSTOMER SERVICE :
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Value-added network services such as mobile data, mobile
Internet and unified messaging all generate certain specific customer
problems and requirements, thereby requiring customer service
personnel to be aware of these issues and know how to solve them.
Nonvoice services are surprisingly complex- involving unique
configurations of phone types, data cards, handheld computers,
subscriptions, operating systems, Internet service providers and so on.
Some network operators require customers to opt into certain value
added services rather than including them as part of the core
subscription- necessitating a customer serviceprocess. Itis even possible
to write a 350 page book about the SHORT message service (it is called
In theory, the need for dedicated customer service for Circuit
Switched Data, SMS and other nonvoice mobile services will decrease in
the future as terminals and services become easier to use and as the
services themselves are used more widely for customer service
The reality in the short and medium term is that the need for
customer support for value-added services will increase not decrease as
awareness of services and their usage increases, and as new services and
terminals come onto the marketplace.
Rather than keeping everything in-house or outsourcing
everything, we are a proponent of an approach that keeps first line
support and customer contact in-house, whilst outsourcing the difficult
specific customer service problems arising from connectivity issues and
so on. In this way, the network operator is aware of and in control of the
kinds of questions and problems its customers are asking.
It is well worth incurring the cost to get the customer aware,
educated and initially set up with data services, because, for example,
once the PC data card has been successfully connected to the laptop to
the Internet software and so on, the same configuration can be
repeatedly used. The one-off customer requirement leads to ongoing
11 GLOSSARY OF TERMS : -
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Second generation; generic name for second generation of digital mobile
networks (such as GSM, and so on)
Third generation; generic name for next-generation mobile networks
(UniversalTelecommunications System [UMTS], IMT-2000; sometimes
GPRS is called 3G in North America)
3G Partnership Project
Border Gateway Protocol
Bits per second
Base Station Controller
Base transceiver station
Dynamic HostConfiguration Protocol
Domain Name System
Enhanced data rates for GSMevolution; upgrade to GPRS systems that
requires new basestations and claims to increasebandwidth to 384
European Telecommunications Standards Institute
Interfacebetween a SGSNand a BSS
Interfacebetween a GGSN and a HLR
Interfacebetween a GGSN and a HLR
Interfacebetween a SMS-GMSCand a SGSN, and between a SMS-
IWMSCand a SGSN
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Interfacebetween a SGSNand an EIR
Gateway GPRS SupportNode
Reference point between GPRS and an external packet data network
GSM interworking unit
Gateway mobile services switching center
Interfacebetween two GSNs within the same PLMN
Interfacebetween two GSNs in different PLMNs
General Packet Radio Service; upgradeto existing 2G digital mobile
networks to provide higher-speed data services
Interfacebetween a SGSNand a HLR
Interfacebetween a SGSNand a MSC/VLR
Global Systemfor Mobile Communications; most widely deployed 2G
digital cellular mobile network standard
GPRS SupportNode (xGSN)
GPRS Tunneling Protocol
High-Level Data Link Control
Home location register
High-speed circuit-switched data; softwareupgradefor cellular networks
that gives each subscriber 56K data
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Layer two Tunneling Protocol
Logical Link Control
Medium Access Control
Mobile services switching center
Network access server
Operations, administration, and management
Packet data network
Packet Data Protocol
Public Land Mobile Network; generic name for all mobile wireless
networks that useearth base stations rather than satellites; the mobile
equivalent of the PSTN
Packet Switched Public Data Network
Public Switched Telephone Network
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Quality of service
Remote Authentication Dial-In User Service
Radio Link Protocol
Serving GPRS SupportNode
Signaling System Number 7
Narrowband digital TDMA standard; uses same frequencies as AMPS,
thus is also known as D-AMPS or digital AMPS