Transcript Networks and Protoco..

Networks and Protocols
CE00997-3
Week 7b
Network technologies
2.5G &
rd
3
generation
2.5G, GPRS
• Contents:
– Why do we need it
– Details of GPRS
– Details of EDGE
GPRS
• 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
GPRS
•3G data use
–Although the UK operators have bought licensees to use 3G the
infrastructure was not ready to be used
–The operators paid a lot for the radio spectrum licenses
• This left little available for infrastructure upgrades
• Also devices were not ready to be used with 2 Mbps
License
Company
Paid (Pounds)
A
TIW (3)
4,384,700,000
B
Vodafone
5,964,000,000
C
MM02
4,030,100,000
D
One2One (T-Mobile)
4,003,600,000
E
Orange
4,095,000,000
GPRS
• General Packet Radio Service (GPRS)
– This standard was agreed by ETSI March 1998
– It is designed to allow data communication to take place within
the existing GSM infrastructure and technology
– 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
GPRS
•General Packet Radio Service (GPRS)
–Features
• Higher connections speeds
– 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?
GPRS – Always on?
•Is it always on
–In the GSM infrastructure to make a data call your device would phone the data
centre which would make the data connection
• This is a part of the circuit switched infrastructure and as such you were paying
for every second you were connected no matter if you were communicating or
not
–Within GPRS you are always attached to the data infrastructure
• When you first turn on your device you are authorised for GPRS
communications
• When you need to use data services you no longer have to dial a number
• Your device will make a request to the SGSN to allow data communications via
the BS
– Once setup your device can then start sending packets across the infrastructure
» There will be a delay but this is very small in comparison to the GSM
infrastructure
GPRS
•GPRS Devices
–In the standard there are three types of GPRS devices
• A
– Capable of Simultaneous data transfer and voice communications
• B
– Automatic switching between voice and data calls. This will need to be
configured on the device itself
• C
– Switching between data and voice operated by the device user manually.
–All of these standards are backwards compatible with the GSM
networks for voice communications
GPRS
•GPRS
–Relies on the fact that Internet communications are bursty in
nature
• 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 from GSM will be broken into smaller parts and
the GPRS data is sent on this circuit.
–All 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
– Lower resource requirements than circuit switched communications
GPRS
• 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
GPRS
•GPRS Channel Breakdown Continued
–A channel which is being used for GPRS data
• Can only be shared between other GPRS users
• It can not be allocated in that time slot for GSM voice calls
– 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
GPRS
•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
GPRS
•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
GPRS
•GPRS Infrastructure
–As discussed earlier GPRS build upon the GSM network.
–One network element need changing
• Base stations
– Requires a software upgrade
• Base station controller
– Requires a software upgrade
–New parts need adding
• Serving GPRS Support Node (SGSN)
– 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
•GPRS Infrastructure continued
–Gateway GPRS Support Node (GGSN)
•
•
•
•
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
– 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
– 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
GPRS
•Packet Control Unit (PCU)
–Logically part of the Base station controller
–Responsible for the radio interface of GPRS
•GPRS and SMS
–SMS messages are sent in GPRS as a part of the normal data
channels
• In GSM they are usually sent via the control channels
–Why
• This changes has taken place ready for the Multimedia Messaging
service (MMS)
– Due to the size of the messages
» The size limits of SMS are removed with MMS
GPRS
GPRS
•Current Supported Protocols
–IP
• Internet Protocol
– Connectionless protocol, which delivers based on best effort
– Widely used in most networks
–X.25
• Connection orientated communications
• Reliability built in with error checking the header
• Uses Virtual circuits
– Intended for terminal services
– Still used but is being replaced by other technologies
GPRS
•IP Address
–As you connect and disconnect you will be given a new IP
Address
• Using Dynamic Host Configuration Protocol (DHCP)
• Consider if you disconnect because an handover does not work
– What happens to your packets, does another device get them ?
• Addresses Issues
– Two options
– Private - only available within the network
» Uses Network address translator (NAT) to get data from the
Internet
– Public – Available from outside of the network
» Effectively the node is a part of the Internet
» All of the PC security issues are still valid
GPRS
•General Packet Radio Service Problems
–Initial problems existed in respect to the GPRS device
•
•
•
•
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
– Potentially this was an issue around how much the advertising of the WAP
services cost operators
–This is now changing
• Vodafone has published for ½ half 2008 35% increase in data revenue
– In the UK it is £383 Million
» http://www.vodafone.com/etc/medialib/attachments/agm_2008.P
ar.77336.File.dat/2008_Annual_Report_FINAL.pdf
» Messaging made the group £923 Million
EDGE – Newer Technology
•Enhanced Data Rate for the GSM Environment (EDGE)
–EDGE was another step towards the holy grail of 3G
–It was developed by Erricson for the losers of the 3G auctions
–EDGE builds upon the infrastructure which is installed for GPRS
–QOS supported
–Improved air interface technology
–Increased throughput from the new encoding method
• 384 Kbps (theoretical)
• 80 – 100 Kbps (closer to reality)
EDGE – UK usage
•There are three operators using this technology
–Orange
–T-Mobile
–O2
• These have upgraded there infrastructure to EDGE to support the use of
the apple i-phone
• Apple listed one of the reasons for EDGE was the relatively large
availability of EDGE rather than 3G communications at this time
• In addition to the reduced battery requirements of EDGE
• Apple have now released the 3G version and as such the technology is
moving towards that
EDGE – Changes
•The changes to the infrastructure
–The BS will need a new transceiver
• This is to deal with the 8 Phase shifting Key (8
PSK) encoding used
– This method will encode 3 bits in each modulation
– This is the one of the reasons why it is 3 times
faster than GPRS
• New software on the BS
– This is to deal with the new encoding method
• The other required changes would have been
carried out during the GPRS upgrades
EDGE – QOS
•QOS classes
–The classes which are supported by EDGE are the same as UMTS
• Conversational
– Real-Time communications highest priority
» Two way communications
• Streaming
– Video – audio files, time dependent
» One way communication
• Interactive
– WWW usage, telnet etc
» Reduced request response time
• Background
– SMS, email, MMS
» Best effort delivery
–Each of the communications will be issued with one of these classes.
• This will depend ion the technology being used for EDGE
EDGE – QOS
•Air Interface Improvements
–Improved Retransmission procedures
• Lower modulation quality techniques can be used
• Packets can then be resent at the new level
• Addressing of frames has been increased to 2048 from the 128 of
GPRS
–Improved Forward error checking
–Measurements for correct sending rate are carried out
continuously
• The coding technique can then be changed to the appropriate rate
EDGE – 3G?
•EDGE and 3G
–The International Telecommunication Union (ITU) made some
definitions for 3G
–Moving slowly a minimum speed of 384 Kbps to be classed as 3G
–EDGE does meet this requirement and as such can be considered as
a 3G technology
• Others describe it as a 2.5G or 2.75G technology!
EDGE – Roll out
•Rollout Stages
–Phase 1
• Introduce single and multi-slot packet switched services
• Introduce single and Multi-slot circuit switched services
–Phase 2
• Web Use
• Email
• Real-time services
– VOIP
– Video Conferencing
GPRS
•Key Points of lecture
–GPRS increases the data rate of GSM
• 20-40 Kbps
–Uses current GSM infrastructure, with small changes
• Additional servers
–How GPRS operates
• Dividing the time slots between multiple users
–EDGE Technology
• What is it
• What is needed
–Issue of IP packets in a network
• Changing IP Addresses
3G UMTS
– Why 3G?
– UMTS (Universal Mobile Telecommunication
system)
– Use of 3G at the moment
3G
• Third Generation (3G)
– We have looked at current and older technologies over the
last couple of lectures
•
•
•
•
TACS
GSM
GPRS
EDGE
– 3G is the currently widely available state of the art
technology
• In terms of high speed data access over a cellular environment
• The user can get access anywhere any time!
3G UMTS
• The Dream (intention)
– 2G and 2.5G systems are incompatible around the
world
– Although GSM is dominant there are still lots of other technologies
• Worldwide devices need to have multiple technologies
inside of them, i.e. tri-band phones, dual-mode phones
– To develop a single standard that would be accepted
around the world
“Access
Information
from
Anyplace,
• One to
device
should be able
to work
anywhere !Anytime”
3G UMTS
• The Dream (continued)
– Worldwide positioning available
• Able to pinpoint a device and direct services to it.
• Mostly to be used for “Push” services
– Increased data rate
• Maximum 2048Kbps
– Operational
• in Europe by 2002
• Japan 2001 (this was achieved)
• Worldwide usage by 2005 (Did not happen)
3G UMTS
• The reality
– Different standards with some operators in difference countries and the rest
of the world
• For example
– In the US market forces dictate the adopted technologies in Europe this is done by
the EU with the agreement of the member states
– In the future market forces may move towards a single standard
• i.e. VHS and Betamax video tapes, currently being seen in the new DVD
standards
– Difficulties
• World wide identical available spectrum
• Agreement on the encoding/decoding technique used
• Local influence groups
– Manufacturers who have invested in one technology
3G UMTS
• Standard
– The 3G standard was written by the International
Telecommunication Union (ITU)
• The standard was referred to as IMT-2000
– The key to the standards was the available data over the air
interface
» 2Mbps in fixed or in-building environments
» 384 kbps in pedestrian or urban environments
» 144 kbps in wide area mobile environments
» Variable data rates in large geographic area systems
(satellite)
3G UMTS
• Other parts of the standard
–
–
–
–
–
Frequency Spectrum
Technical Specification
Radio and Network components
Tariffs and Billing
Technical Assistance
• 3 Main technical implementations were agreed
– UMTS - Europe
– CDMA2000 - America
– TD-SCDMA – China
3G Standards
• Added Confusion
– Two specification groups create the standards within the ITU
specifications
• 3GPP
– Developed the standards for the UMTS system which is built upon GSM
• 3GPP2
– Developed the standards building upon the US CDMA networks, specifically
the CDMA-2000 standard
• The Chinese group is referred to as
– Chinese Academy of Telecommunications Technology (CATT)
3G UMTS
• Universal Mobile Telecommunication system (UMTS)
– UMTS
• Builds upon the successful European GSM network
– Incorporates the developments made for the GPRS and EDGE networks
• Five areas of standardisation
–
–
–
–
Radio
Core Network
Terminals
Services
3G UMTS
• The core network
– Asynchronous Transfer Method (ATM)
• Has been defined as the core networking technology
–
–
–
–
ATM allows circuit switched transfer of data using packets.
High speed data transfer – currently maximum 10 Gbps
Guarantee of quality of service for the duration of packet transfer
Small packets used called cells for the transfer of data to minimise the impact
on the routers, network and switches.
– IPv6
• Arguments are being pushed for the core network to allow IPv6
• RFC3314, September 2002
– This would allow packets to be transferred directly from the internet to the
device with no translation
– IPv6 does contain QOS headers, which can be used with the correctly
configured hardware
– All 3G devices could have a single IP address that would not need to change
3G UMTS
• UMTS
– Full packet driven architecture
• For voice and for data transmissions.
• Packet based networks allow for an increased amount of
traffic on a medium.
• The only time part of that medium is blocked is when a
device is transmitting or receiving.
– Consider how often in your phone calls you actually say nothing
» Natural pause between words
» Taking a breath
» Waiting for a response
» Thinking of something to say
3G UMTS
•UMTS
–Offers voice and data services the same as EDGE
• Services offered will be classed into one of the following
Conversational
Streaming
Real-Time
Voice
Streaming Video
Interactive
Background
Best-effort, guarantee of quality
delivery
Web Pages
MMS, SMS,
emails
• From these classes certain defined Quality of Service (QOS) specifications
are guaranteed like packet delay time
3G UMTS
• Intended Data Rates
– Actual data rates will be effected by
•
•
•
•
•
•
Interference (other devices, background, buildings)
Over use of the frequency
Weather!
Amount of other traffic
Base station / cell actually attached to
Speed you are moving at !
3G UMTS
• Types of Cells and Base station to use them
– Macro Cell
• These cover a large area and will give slow access
• 144 Kbps – max speed of 500 Km/h
– Micro Cell
• These should cover a medium area
• 384 Kbps max speed 120 Km/h
– Pico Cell
• Less than 100 metres
• 2 Mbps – max speed of 10 Km/h
• Difficult to predict
– Actual distances and bandwidth depend on local conditions
3G UMTS
•Types of Cells and Base station to use them
–Cells will operate in a hierarchy overlaying each other
Global
Satellite
Suburban
Urban
In-Building
Micro-Cell
Macro-Cell
Pico-Cell
3G UMTS
•Consider
–These data rates are in Mega Bits per Second and Kilo Bits
• In terms of data rate the measure of a kilo bit is 1000 bits
– Not the 1024 which is used for data storage
–So
• 2 Mega Bits per Second = 244 Kilo Bytes per second (roughly)
3G UMTS – Hierarchy of Cells
3G UMTS
•What transmitters/base stations look like
–Pictures taken from
(http://www.scotland.gov.uk/library/pan/pan62-05.asp, 2009)
3G Base Station Locations
•A database of all cellular base stations is provided by
OFCOM in the UK
–This database contains the locations of all Base stations and discuss the details of them
• Here is a screen grab of Stafford, UK
• http://www.sitefinder.radio.gov.uk/
3G UMTS
•Radio Interface: Allocated Frequencies
3G - UK
•3G spectrum auction
–License shows the size of the spectrum with A being the largest
• Part of the auction rules was a new company in the UK won the License type ‘A’
• Auction closed on the 27th April 2000
• Original estimates were for a total selling value of £1.5 billion
(http://www.3gnewsroom.com/html/whitepapers/nao_3g_report.zip)
• The license is allocated until the 31st December 2021
• The operators must have 80% uk coverage by the 31st December 2007 otherwise they will be
fined
–The UK phone companies in June, 2003 said that they would claim the VAT back on the license
purchases! About £3.3 Billion pounds
• European Court case started in 2004
• This claim though was dismissed though in June 2007
(http://www.theregister.co.uk/2007/06/26/no_vat_on_3g/)
License
Company
Paid (Pounds)
A
TIW (3)
4,384,700,000
B
Vodafone
5,964,000,000
C
MM02
4,030,100,000
D
One2One (T-Mobile)
4,003,600,000
E
Orange
4,095,000,000
3G UMTS
•UK 3G Winners ??
3G UMTS
•Radio Interface
–UMTS uses Wideband-Code Division Multiple Access (W-CDMA)
•
•
•
•
Also known as “IMT-2000 Direct Spread”
Extremely complex algorithms
Uses 10x the current 2G processing power!
Modulation is done with Quadrature phase shift keying (QPSK)
– This encodes 2 bits with each change
• Supports two modes of operation
– Frequency Division Duplex (FDD)
– Time Division Duplex (TDD)
3G UMTS
•W-CDMA
–Operates in the same manner as the CDMA used in the US
• CDMA allows multiple users to communicate at the same time over the
same frequency
– Each of the devices is given a “Chipping code” this is known by the device
and the base station.
– This chipping code is then used to identify the signal and allows the BS to
receive the signal
– The chipping code is used to adjust the frequency of data transferred
during the transfer
– The essential point of CDMA is the use of power control
3G UMTS
•W-CDMA
–Wideband CDMA operates the same but this takes place over
a wider area of frequency
• UMTS uses 5MHz for the signal
• CDMA (narrowband) uses 200 KHz
• These communications are secure by the nature that unless the
chipping code is known, the sequence of the data can not be
known
• Communications can take place as soon as the device is ready
and frequency reuse factor is now one
3G UMTS
•W-CDMA
–Frequency Reuse Factor
• This is the distance which needs to be left between cells
• As the same frequency is reused and the chipping code which is
used is change and unique to a BS
• The frequency can be reused in adjoining cells
• Temporary Base stations can be added to the infrastructure if
required, as long as the chipping code was unique
3G UMTS
•Power Control
–If you consider a group of people speaking, Chinese, English and
Italian
• If these all speak at the same volume you can then listen for the parts
which you understand.
– If the English person starts talking louder than the rest, the all you will hear
is English
– The other languages will be drowned out
• CDMA Works on the same basis
– One point of CDMA is the power control, so that the power sent out is just
enough to allow data transfer to take place.
» As a side effect of this technology this controlling of the power that
the radio interface uses, also saves the battery on the device
3G UMTS
•W-CDMA, Infrastructure
3G UMTS
•W-CDMA – UTRAN
–The core network for 3G will remain the same as GSM
• This is a purely cost issue, in the future the infrastructure will be
upgraded
GSM
UMTS
Mobile device/station (MS)
User Equipment (UE)
Base Station (BS)
Node-B
Base Station Controller (BSC)
Radio Network Controller (RNC)
3G UMTS
•W-CDMA
–UMTS Terrestrial Radio Access Network (UTRAN)
• A device which wishes to communicate need’s to request access
to the network
– This is to prevent too many devices communicating at once
– Although CDMA will theoretically allow a very large number of user
to communicate at once
» What actually happens is the quality of the calls is reduced
considerably
» This is a issue for voice but is a disaster for data calls
3G UMTS
•W-CDMA
–Handover
• UMTS will use a soft handover technique
– GSM used a hard handover technique
– In a handover the device is always attached to at least one BS
Node-B
Node-B
Node-B
Node-B
Node-B
Node-B
3G UMTS - WCDMA
• The technology which UMTS is based upon (WCDMA)
has some patented content
– On this basis any manufacturer who builds a handset needs
to pay royalties to Qualcomm
– On the 1st of October 2007 the European Community
started looking into this to investigate if Qualcomm was
overcharging
•
•
•
http://www.iht.com/articles/2007/10/01/business/cell.php
"If the other patent holders were to do as Qualcomm is doing,
royalties could raise the cost of WCDMA handsets considerably thus raising the prices to consumers.“
In October 2008 Nokia paid $2.3 Billion for the use of the
technology
–
This will settle worldwide court cases which were ongoing
» http://www.eetimes.com/news/semi/showArticle.jhtml?articleID=2
11200865
3G UMTS
•3G UMTS was tested in the Isle of Man for Europe
• The equipment was run and operated by O2
• The license spectrum used on this island was given free by the government
• The actual devices used were given to some of the islanders
– The idea was to trial the equipment in a limited manner
– Also they wanted to see if there was a pattern of usage for the technology i.e. the killer app
– A single killer app, like SMS was for GSM, is unlikely
» It is more likely a series of applications will be popular
» http://www.conted.ox.ac.uk/cpd/electronics/links/killer_applications_for_3g.asp
•3G is now widely available
• Most of the operators started to get the infrastructure working in 2004 and this is continuing
to cover the country
• The devices to make use of the technology are also now widely available and the cost is
coming down.
• PCMCIA cards are available for laptops to give data access
–Japan
• When we consider Japan for the killer app it was email!
– 3G bandwidth is not needed for email!
3G UMTS
•
Increasing usage of this technology now it is rolled out is being developed
–
Mobile broadband as an alternative to DSL connections from phone companies
•
Increasing number of devices which can make use of this technology with USB
dongles or inbuilt technology
•
All of this allows for 3G to be rolled out increasingly to devices which are beyond the
original consideration of just a “mobile phone”
•
On the 30th of September 2008 a number of companies have linked with the GSMA to
produce a symbol to rival the Wi-Fi logo
–
–
•
Mobile Broadband to be put onto Laptops which support 3G connectivity
http://www.gsmworld.com/news/press_2008/press08_61.shtml
Also interesting if the government statistics on this technology
–
That 19% of mobile phone users had used it to connect to the Internet in the last 3 months
http://www.statistics.gov.uk/pdfdir/iahi0808.pdf
UMTS
• Links
– Details of the 3G license auction (UK)
• www.umts-forum.org/servlet/dycon/ztumts/umts/Live/en/umts/Resources_Licensing_UK
– UMTS standards documents
• www.3gpp2.org/Public_html/specs/index.cfm