Transcript Price Paid

General Packet
Radio Service
Justin Champion
Room C208 - Tel: 3273
www.staffs.ac.uk/personel/engineering_and_technology/jjc1
General Packet Radio Service
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Contents
 Why
do we need it
 Details of GPRS
 Sending of Packets
General Packet Radio Service
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Value Added Services
 Operators
have seen the use of data as a new
source of revenue
 The potential for data use is
To sell the users the data applications
 To charge them for data needed to use them
 To charge other developers to allow the applications on
to the network
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General Packet Radio Service
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3G data use
 Although
the UK operators have bought licensees to
use 3G the infrastructure is not ready
 The operators paid a lot for the radio spectrum
licenses
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This left little available for infrastructure upgrades
Also devices were not ready to be used with 2 Mbps
Company
Price Paid
Company
Price Paid
Hutchison 3G
US$ 6.9 billion
T-Mobile
US$ 6.3 billion
Orange
US$ 6.44 billion
O2
US$ 6.35 billion
Vodafone
US$ 9.4 billion
General Packet Radio Service
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General Packet Radio Service (GPRS)

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This standard was agreed by ETSI March 1998
It is designed to allow data communication to take
place within the existing GSM infrastructure.
A few additional servers are added to the network to
allow this and these will be discussed later
This is described as being a 2.5G technology
To use GPRS you will need a GPRS enabled device

Existing GSM devices will not be able to make use of
the additional features
General Packet Radio Service
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General Packet Radio Service (GPRS)
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Features
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Higher connections speeds
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Theoretical Maximum of 171 Kbps
 Interference
 Distance from transmitter
 All GSM channels would have to be dedicated to GPRS
communications
 This speed also does not take into account any error-correction
 Does not consider a device uploading data
Actually speeds with conditions taken into account is theoretically a
maximum of 53.6 Kbps
 Studies have show the average is usually about 30 – 40 Kbps
Always on Data communications

No delay in setting up a data communication
General Packet Radio Service
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GPRS Devices
 In
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 All
the standard there are three types of GPRS devices
A
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Capable of Simultaneous data transfer and voice communications

Automatic switching between voice and data calls. This will need to
be configured on the device itself

Switching between data and voice operated by the device user
manually.
B
C
of these standards are backwards compatible with the
GSM networks for voice communications
General Packet Radio Service
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GPRS
 Relies
on the fact that Internet communications are
bursty in nature
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 All
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A large amount of data will be received and the user will process
it before requesting more i.e. a web page
A single voice circuit will from GSM will be broken into smaller
parts and the GPRS data is sent on this circuit.
data is sent in packets
Data must be broken into small packets
These packets are re-assembled at the destination
These packets add an overhead in the form of the packet header
General Packet Radio Service
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GPRS Channel Breakdown
Channel
Use of the Channel
0
Voice
1
AAAABBABBAAAAFA
2
Voice
3
AAABAABAAAFAAAA
4
AAAFAFAFFFAFFFFB
5
BBBBABABAFFFFFFF
6
Voice
7
FFAFFAFFABABBBBB
Data Users
A = User 1
B = User 2
F = User 3
In this instance we
have 3 voice calls and
5 users receiving data
General Packet Radio Service
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GPRS Channel Breakdown Continued
 A channel
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Can only be shared between other GPRS users
It can not be allocated in that time slot for GSM voice calls
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which is being used for GPRS data
Even if part of the time slot is available
The use of GPRS will reduce the amount of voice calls that can
be made on that cell
With enough data calls a cell will become useless for voice
callers, which require exclusive access to the time slots
General Packet Radio Service
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GPRS Multi slot classes
Class
Downlink
Uplink
Maximum Active
1
1
1
2
2
2
1
3
3
2
2
3
4
3
1
4
5
2
2
4
6
3
2
4
7
3
3
4
8
4
1
5
9
3
2
5
10
4
2
5
11
4
3
5
12
4
4
5
General Packet Radio Service
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GPRS coding schemes
 Depending
on environment one of the following coding
schemes are used
Scheme Max Throughput per 1 Time Slot
Error Checking
CS-1
8 Kbps
Good
CS-2
12 Kbps
Good
CS-3
14.4 Kbps
Moderate
CS-4
20 Kbps
Poor
Schemes CS-1 and CS-2 are usually used
General Packet Radio Service
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GPRS network layers
General Packet Radio Service
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GPRS network layers
 SNDCP
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Provides services to the higher layers
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Compression
Connectionless, connection orientated services
Multiplexing
Segmentation
 BSSGP
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Allows
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Maps a SGSN to a BSS
Control information between a BSS and a SGSN
 BSS
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Refers to a base station and an associated Base station controller
General Packet Radio Service
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GPRS Infrastructure
 As
discussed earlier GPRS build upon the GSM networks.
 Network elements need changing
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Base stations
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Requires a software upgrade
Base station controller

Requires a software upgrade
 New parts need adding
 Serving GPRS Support Node (SGSN)
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Has VLR functionality
 Authorise attached users
Details recorded of data packets to be charged for
Session Management
Router for packets which may be lost during a handover during a data
call
General Packet Radio Service
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GPRS Infrastructure continued
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Gateway GPRS Support Node (GGSN)
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Is the connection into the GPRS network
It carries out all translations that area required
Firewall for the network
Collates data regarding the amount of packets received
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Potentially in the future this will allow for competing GGSN’s in a network! Free
market choosing either the cheapest or most reliable GGSN!
There are 3 types of GGSN
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A – Near Future/Now
 The GGSN becomes part of its own ISP and provides Internet services. The
devices will be assigned IP address using DHCP.
B – Now
 The SSGN always selects the same GGSN to do the Internet work. The
configuration will be done dynamically and on a temporary basis
C – Future
 This allows a private company to have its own GGSN, with an encryption
key so that only authorised devices can gain access. i.e. a VPN into a
network, constant email access etc
General Packet Radio Service
General Packet Radio Service
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Packet Control Unit (PCU)
 Logically
part of the Base station controller
 Responsible for the radio interface of GPRS
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GPRS and SMS
 SMS
messages are sent in GPRS as a part of the
normal data channels
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In GSM they are usually sent via the control channels
 Why
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This changes has taken place ready for the Multimedia
Messaging service
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Due to the size of the messages
General Packet Radio Service
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Current Supported Protocols
 IP
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Internet Protocol
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Connectionless protocol, which delivers based on best effort
Widely used in most networks
 X.25
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Connection orientated communications
Reliability built in with error checking the header
Uses Virtual circuits
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Intended for terminal services
Still used but is being replaced by other technologies
General Packet Radio Service
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General Packet Radio Service Problems
 Initial
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When launched there was only a few compatible devices
These had poor features and terrible battery life
There was nothing to use the increased data rate
Limited advertising of the features of GPRS

 This
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problems existed in respect to the GPRS device
Potentially this was an issue around how much the advertising of the
WAP services cost operators
is now changing
O2 have seen a 25% growth in usage of GPRS data from Jan to
June 2003
(http://www.ovum.com/go/content/c,36230, 2003)
General Packet Radio Service
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Summary
 Why
we need the technology
 What it is
 Infrastructure changes