Networks and Protocols CE00997-3

Week 7b

Network technologies

2.5G & 3rd 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

•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

LicenseLicense CompanyCompany PaidPaid (Pounds) (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

•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 – Always on?

•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 BreakdownChannel 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 classesClass 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

•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

•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

GPRS

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

• One device should be able to work anywhere !“Access to Information from Anyplace, 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

• From these classes certain defined Quality of Service (QOS) specifications are guaranteed like packet delay time

Conversational Streaming Interactive Background

Real-Time Best-effort, guarantee of quality delivery

Voice Streaming Video Web Pages MMS, SMS, emails

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

Satellite

Macro-CellMicro-Cell

UrbanIn-Building

Pico-Cell

Global

Suburban

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/) LicenseLicense CompanyCompany PaidPaid (Pounds) (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 UMTSMobile 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=211200865

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