Download Mobile Communications

Wireless Communication
and Mobile Technology
Chapter 1: Introduction
What is Wireless?
Wireless refers to the method of transferring
information between computing devices, such as a
personal data assistant (PDA) and a data source
such as an agency database server, without a
physical connection or wires.
The distances involved may be short (a few meters
as in television remote control) or long (thousands
or millions of kilometers for radio
communications).
Not all wireless communication technologies are
mobile.
What is Wireless?
For example, lasers are used in wireless data
transfer between buildings, but cannot be used in
mobile communication at this time.
Because in this technology transmitter and
receiver will remain at fixed position and if is
change the communication may loss.
What is Mobile?
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Mobile simple describes a computing device that
is not restricted to a desktop.
Mobile device may be a PDA, a “smart” cell
phone, a laptop computer, or any one of numerous
other devices that allow the user to complete
computing task without being connected to a any
Network.
What is Wireless communication?
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Wireless communication is simply data
communication without the use of landlines.
This may involve cellular telephone, two-way
radio, fixed wireless (broadband wireless), laser
(free space optics), or satellite communications.
What is Mobile Computing?
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It is a technology that allows transmission of data
via, a computer without having to be connected to
a fixed physical link.
Mobile computing environment as being made up
of three main components: a computer (that
moves), a N/W (that is either wired or wireless) &
co-ordination S/W that ties them together.
In mobile N/W computing activities are not
disrupted when the user changes the computer’s
points of attachment to the internet.
What is Mobile Computing?
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Instead all the needed reconnection occurs
automatically & no interactively.
Truly mobile computing offers many advantages.
Confident access to the internet any time, any
where will help free us from the ties that bind us
to our desktops.
Why Wireless communication?
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People now a day are demanding instant
communication at the same time they do not want
to stick to their desk or office.
What they want is communication at any where
and any time, even though they are on move.
The solution for complete mobility is only.
Wireless computing can make significant
difference in your productivity, responsiveness to
the customer.
You can also reduce or eliminate cabling cost and
relocate devices without having to rewire your
facilities.
Advantages of Wireless Communication?
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Mobility:
Wireless network systems can provide network
users with access to real-time information
anywhere in there organization.
The mobility supports productivity and service
opportunities not possible with wired networks.
Advantages of Wireless Communication?
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Installation speed & simplicity:
Installation a wireless network system can be fast
and easy and can eliminate the need to pull cable
through walls and ceilings.
Installation Flexibility:
Wireless technology allows the network to go
where wire can not go.
Advantages of Wireless Communication?
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Reduced cost of Ownership:
While the initial investment required for wireless
network hardware can be higher than the cost of
wired.
N/W hardware overall installation expenses and
life-cycle costs can be significantly lower.
Long term cost benefits are greatest in dynamic
environments requiring frequent moves and
changes.
Advantages of Wireless Communication?
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Scalability:
Wireless N/W systems can be configured in a
variety to topologies to meet the need of specific
application and installations.
Configurations are easily changed and range from
peer to peer N/W suitable for a small no of users
to full infrastructure N/Ws of thousands of users
that enable roaming over a broad area.
Disadvantage of wireless
communication
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Radio signal interference:
Because wireless devices operate using radio
signals, the potential for two type of signal
interference exists.
Signals from other devices can disrupt what a
wireless device is trying to transmit, or a wireless
device may itself be a source of interference for
other devices.
several common office devices transmit radio
signals that may interfere with a WLAN.
Disadvantage of wireless
communication
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These devices include microwave ovens, elevator
motors and other heavy electrical equipment.
These may cause errors to occur in the
transmission between a wireless device and an
access point.
In addition, Bluetooth and WLAN 802.11 devices
both operate in the same radio frequency,
potentially resulting in interference between such
devices.
Disadvantage of wireless
communication
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The solution for wireless devices is the same as
that for standard cabled network devices: locate
the source of the interference and eliminate it.
This usually is solved by moving a photocopier or
microwave oven across the room or another room.
In addition many wireless devices can identify that
an error has occurred in the transmission and
retransmit the data as necessary.
Disadvantage of wireless
communication
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Security:
Because a wireless device transmits radio signals
over a broad area, security becomes a major
concern.
It is possible for an intruder to be lurking outdoors
with a note book computer and wireless NIC with
the intent of intercepting the signals from a nearby
wireless network.
Because much of a business network traffic may
contain sensitive information, this is a real concern
for many users.
Disadvantage of wireless
communication
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However, some wireless technologies can provide
added levels of security.
A special coded number can be programmed into
every authorized wireless device and the device
must transmit the special number prior to gaining
access to the network, otherwise it is denied
access.
Network managers can also limit access to a
wireless network by programming it with a list of
approved wireless devices.(e.g:cyber roam)
Disadvantage of wireless
communication
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Only those devices on the list will be allowed
access.
As a further protection, data transmitted between
the access point and the wireless device can also
be encrypted or encoded in such a way that only
the recipient can decode the message.
If an unauthorized user were to intercept the radio
signals being transmitted, he or she could not read
the messages being sent.
Disadvantage of wireless
communication
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Health risks:
Wireless devices contain radio transmitters and
receivers that emit radio frequency (RF) energy.
Typically, these wireless devices emit low levels
of RF while being used.
Scientists know that high levels of RF can
produce biological damage through heating
effects. (This is how a microwave oven is able to
cook food.)
Disadvantage of wireless
communication
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In the United States, the Food and Drug
Administration (FDA) and the Federal
Communications commission (FCC) set policies
and procedures for some wireless devices, such as
cellular telephones.
The latest FDA update stated that “ the available
science does not allow us to conclude the that
(wireless devices) are absolutely safe, or that they
are unsafe.”
Disadvantage of wireless
communication
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Thus the available science does not permit a
conclusion either way about the safety of wireless
mobile devices.
There is no evidence regarding any health risks
associated with using any wireless device, it is
always wise to be aware of the concern and to
monitor ongoing scientific research.
Different between Mobile and Wireless
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Two aspects of mobility:
 user mobility: users communicate (wireless) “anytime,
anywhere, with anyone”
 device portability: devices can be connected anytime,
anywhere to the network
Wireless vs. mobile
Examples
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stationary computer
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notebook in a hotel
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wireless LANs in historic
buildings
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Personal Digital Assistant
(PDA)
Mobile and Wireless Devices
Pager
• receive only
• tiny displays
• simple text
messages
PDA
• graphical displays
• character recognition
• simplified WWW
Mobile phones
• voice, data
• simple graphical displays
Laptop/Notebook
• fully functional
• standard applications
Smart phone
• tiny keyboard
• simple versions
of standard applications
performance
Application of Mobile and Wireless
Communications
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Education:
Wireless technology is an ideal application of
colleges and schools.
An instructor can create a classroom presentation
on the notebook computer in his home or school
office and this presentation can access in
classroom using wireless devices.
Teachers can also distribute handouts directly to
students who have brought their own wireless
devices to class.
Application of Mobile and Wireless
Communications
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The wireless connection also frees students from
having to go to a specific computer lab or the
library to get on the college campus network.
They can access the campus network “wirelessly”
from almost any location on campus.
Application of Mobile and Wireless
Communications
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Home Entertainment:
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Several large computer manufacturers are
introducing specialized media PCs that enable
movie and audio enthusiasts to download,
distribute and control all forms of digital
entertainment from anywhere in the house.
Some of the systems also have the ability to
control lights, air conditioners and other
household devices.
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Application of Mobile and Wireless
Communications
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You can send music, movies, or pictures to a
stereo receiver, portable device or PC located
anywhere in the house.
You can also download the files to your digital
media portable devices, such as MP3 and video
players that can be used while roaming throughout
the house.
Application of Mobile and Wireless
Communications
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Vehicles :
 Transmission of news, road condition, weather,
music via DAB(Digital Audio Broadcasting )
 Personal communication using GSM(Global
System for Mobile Communications)/UMTS(Universal
Mobile Telecommunications System )
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Position via GPS(Global Positioning System )
local ad-hoc network with vehicles close-by to
prevent accidents, guidance system
vehicle data (e.g., from busses, high-speed trains)
can be transmitted in advance for maintenance
Typical application: road
traffic
UMTS, WLAN,
DAB, DVB, GSM,
cdma2000, TETRA, ...
Prof. Dr.-Ing.
Jochen H. Schiller
www.jochenschiller
.de
MC - 2009
Personal Travel Assistant,
PDA, Laptop,
GSM, UMTS, WLAN,
Bluetooth, ...
Application of Mobile and Wireless
Communications
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In Companies:
In companies mangers can use mobile computer in, say
critical presentations to major customers.
They can access the latest market share information.
At a small recess, they can revise the presentation take
advantages of this information.
They can communicate with the office about possible new
offers and call meetings for discussing responds to the new
proposals.
Therefore, mobile computers can leverage competitive
advantages.
Application of Mobile and Wireless
Communications
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Government:
Government applications center around
assessments, inspections and work orders.
Most of these applications involve auditing some
sort of facility or process
For e.g.: food service, restaurant, child care,
schools, and residential buildings.
Application of Mobile and Wireless
Communications
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Emergency Services:
Emergency services ability to receive information
on the move is vital where the emergency services
are involved.
Information regarding the address, type and other
details of an incident can be dispatched quickly,
via CDPD(Cellular Digital Packet Data) system
using mobile computers.
Here, the reliability and security implemented in
the CDPD system would be of great advantage.
Application of Mobile and Wireless
Communications
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Healthcare:
The focus in the industry has been on automting
patient records, medication dispersion and sample
collection.
A common goal is to leverage mobile computing
in the implementation of positive patient
identification.
Application of Mobile and Wireless
Communications
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Market Research:
Automating the survey process has enable these
companies to get their data more accurately and
quickly while being able to customize their
queries at will.
Application of Mobile and Wireless
Communications
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Credit Card Verification:
At Point of Sale (POS) terminals in shops and
supermarkets, when customers use credit cards for
transactions, the intercommunication required
between the bank central computer and the POS
terminal, in order to effect verification of the card
usage, can take place quickly and securely over
cellular channels using a mobile computer unit.
This can speed up the transaction process and
relieve congestion at the POS terminals.
Application of Mobile and Wireless
Communications
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Electronic Mail/Paging:
Usage of mobile unit to send and read emails is a
very useful asset for any business individual, as it
allow him/her to keep in touch with any
colleagues as well as any urgent developments that
may affect their work.
Access to the internet, using mobile computing
technology, allows the individual to have vast
array of knowledge at his/her fingertips.
Application of Mobile and Wireless
Communications
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Paging is also achievable here, giving even more
intercommunication capability between
individuals, using a single mobile computer
device.
Application of Mobile and Wireless
Communications
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Taxi/Truck Dispatch:
Using the idea of a centrally controlled dispatcher
with several mobile units(taxis), mobile
computing allows the taxis to be given full details
of the dispatched job as well as allowing the taxis
to communicate information about their
whereabouts back to the central dispatch office.
This system is also extremely useful in secure
deliveries i.e.: securicor.
Application of Mobile and Wireless
Communications
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This allows a central computer to be able to track
and receive status information from all of its
mobile secure delivery vans.
Again, the security and reliability properties of the
CDPD system shine through.
Wireless Operating Systems
and Languages
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Major Operating System
 Palm OS
 EPOC (Symbian)
 Windows CE
 JAVA Micro Edition
Wireless Languages
 HDML
 WML
 cHTML
Types of Wireless Systems
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AMPS and European Analog cellular (Advanced
Mobile Phone System)
TDMA (Time Division Multiple Access)
CDMA (Code-Division Multiple Access)
GSM (Global System for Mobile
Communication)
GPRS (General Packet Radio Service)
EDGE (Enhanced Data Rates for Global
Evolution)
Types of Wireless Technologies
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Radio Waves
Microwave
Wi-Fi
Wi-Max
ZIGBEE
Location Dependent Services
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Many research efforts in mobile computing and
wireless networks try to hide the fact that the
network access has been changed or that a
wireless link is more error prone than a wired one.
Examples: Mobile IP tries to hide that fact of
changing access points by redirecting packets but
keeping the same IP address, and many protocols
try to improve link quality using encoding
mechanisms or retransmission so that applications
made for fixed networks still work.
Location Dependent Services
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In many cases, however, it is important for an
application to ‘known’ something about the
location or it might be that the user needs location
information for further activities.
Several services that might depend on the actual
location can be distinguished:
Follow-on Services:
Location aware Services:
Privacy:
Information Services:
Support Services:
Location Dependent Services
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Follow-on Services:
The function of forwarding calls to the current
user location is well-known from the good old
telephone system.
Wherever you are just transmit your temporary
phone number to your phone and it redirects
incoming calls using mobile computer a followon service could for instance.
This offer the same desktop environment
wherever you are around the world.
Location Dependent Services
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All e-mail would automatically be forwarded, all
changes to your desktop and documents stored,
at a central location at your company.
If someone wanted to reach you using a
multimedia conferencing system, this call would
then also be forwarded to your current location.
Location Dependent Services
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Location aware Services:
Imagine you wanted to print a document sitting
in the lobby of a hotel using your laptop.
If your drop the document over the printer icon,
where would you expect the document to be
printed?
Certainly not by the printer in your office!
But without additional information about your
environment, this might be the only thing you
can do.
Location Dependent Services
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Therefore services are needed that provide
information about the capabilities of your
environment.
For instance, there could be a service in the hotel
announcing that a standard laser printer is
available in the lobby, a color printer in a hotel
meeting room etc.
In return your computer might then transmit your
personal profile to your environment, so that the
hotel can charge you with the printing costs.
Location Dependent Services
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Privacy:
The two service classes listed above
immediately raise the question of privacy.
You might not want video calls following you to
dinner, but may be you would want important emails to be forwarded.
So there might be locations and/or times when
you want to exclude certain services form
reaching you, thereby telling the caller that you
do not want to be disturbed.
Location Dependent Services
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Furthermore, although you want to utilize
location dependent services, you might not
want the environment to know exactly who
you are?
Imagine a hotel monitoring all guests and
selling these profiles to companies for
advertisements.
Location Dependent Services
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Information Services:
While walking around in a city you could
always use your wireless travel guide to ‘pull’
information from a service, e.g., ‘where is the
next Mexican restaurant to my current position?’
But a service could also actively ‘push’
information on your travel guide, e.g., that the
Mexican restaurant just around the corner has a
special offer.
Location Dependent Services
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Support Services:
Finally, many small additional mechanisms can
be integrated to support a mobile device.
Intermediate results of calculations, state
information or cache contents could ‘follow’ the
mobile node through the fixed network.
As soon as the mobile node reconnects, all
information is available again.
Location Dependent Services
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This helps to reduce access delay and traffic
within the fixed network.
The alternative would be a central location for
user information and a user accessing this
information through the network all the time as
it is typically done today.
Early history of wireless
communication
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Many people in history used light for communication
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heliographs, flags (“semaphore”), ...
150 BC smoke signals for communication;
(Polybius, Greece)
1794, optical telegraph, Claude Chappe
Here electromagnetic waves are
of special importance:
 1831 Faraday demonstrates electromagnetic induction
 J. Maxwell (1831-79): theory of electromagnetic Fields, wave
equations (1864)
 H. Hertz (1857-94): demonstrates
with an experiment the wave character
of electrical transmission through space
(1888, in Karlsruhe, Germany)
History of wireless communication I
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1896 Guglielmo Marconi
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1907 Commercial transatlantic connections
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huge base stations
(30 100m high antennas)
1915 Wireless voice transmission New York - San Francisco
1920 Discovery of short waves by Marconi
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first demonstration of wireless
telegraphy (digital!)
long wave transmission, high
transmission power necessary (> 200kW)
reflection at the ionosphere
smaller sender and receiver, possible due to the invention of the vacuum
tube (1906, Lee DeForest and Robert von Lieben)
1926 Train-phone on the line Hamburg - Berlin
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wires parallel to the railroad track
History of wireless communication II
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1928 many TV broadcast trials (across Atlantic, color TV, news)
1933 Frequency modulation (E. H. Armstrong)
1958 A-Netz in Germany
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1972 B-Netz in Germany
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analog, 160MHz, connection setup from the fixed network too (but location of the
mobile station has to be known)
available also in A, NL and LUX, 1979 13000 customers in D
1979 NMT at 450MHz (Scandinavian countries)
1982 Start of GSM-specification
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analog, 160MHz, connection setup only from the mobile station, no handover, 80%
coverage, 1971 11000 customers
goal: pan-European digital mobile phone system with roaming
1983 Start of the American AMPS (Advanced Mobile Phone System, analog)
1984 CT-1 standard (Europe) for cordless telephones
History of wireless communication III
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1986 C-Netz in Germany
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1991 Specification of DECT
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analog voice transmission, 450MHz, hand-over possible, digital signaling,
automatic location of mobile device
was in use until 2000, services: FAX, modem, X.25, e-mail, 98% coverage
Digital European Cordless Telephone (today: Digital Enhanced Cordless
Telecommunications)
1880-1900MHz, ~100-500m range, 120 duplex channels, 1.2Mbit/s data
transmission, voice encryption, authentication, up to several 10000 user/km2, used
in more than 50 countries
1992 Start of GSM
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in D as D1 and D2, fully digital, 900MHz, 124 channels
automatic location, hand-over, cellular
roaming in Europe - now worldwide in more than 200 countries
services: data with 9.6kbit/s, FAX, voice, ...
History of wireless communication IV
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1994 E-Netz in Germany
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1996 HiperLAN (High Performance Radio Local Area Network)
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ETSI, standardization of type 1: 5.15 - 5.30GHz, 23.5Mbit/s
recommendations for type 2 and 3 (both 5GHz) and 4 (17GHz) as wireless ATMnetworks (up to 155Mbit/s)
1997 Wireless LAN - IEEE802.11
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GSM with 1800MHz, smaller cells
as Eplus in D (1997 98% coverage of the population)
IEEE standard, 2.4 - 2.5GHz and infrared, 2Mbit/s
already many (proprietary) products available in the beginning
1998 Specification of GSM successors
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for UMTS (Universal Mobile Telecommunications System) as European proposals
for IMT-2000
Iridium
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66 satellites (+6 spare), 1.6GHz to the mobile phone
History of wireless communication V
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1999 Standardization of additional wireless LANs
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IEEE standard 802.11b, 2.4-2.5GHz, 11Mbit/s
Bluetooth for piconets, 2.4GHz, <1Mbit/s
decision about IMT-2000
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Start of WAP (Wireless Application Protocol) and i-mode
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first step towards a unified Internet/mobile communication system
access to many services via the mobile phone
2000 GSM with higher data rates
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HSCSD offers up to 57,6kbit/s
first GPRS trials with up to 50 kbit/s (packet oriented!)
UMTS auctions/beauty contests
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several “members” of a “family”: UMTS, cdma2000, DECT, …
Hype followed by disillusionment (50 B$ paid in Germany for 6 licenses!)
Iridium goes bankrupt
2001 Start of 3G systems
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Cdma2000 in Korea, UMTS tests in Europe, Foma (almost UMTS) in Japan
History of wireless communication VI
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2002
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2003
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over 3.3 billion subscribers for mobile phones (NOT 3 bn people!)
2008
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HSDPA starts in Germany as fast UMTS download version offering > 3 Mbit/s
WLAN draft for 250 Mbit/s (802.11n) using MIMO
WPA2 mandatory for Wi-Fi WLAN devices
2007
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WiMax starts as DSL alternative (not mobile)
first ZigBee products
2006
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UMTS starts in Germany
Start of DVB-T in Germany replacing analog TV
2005
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WLAN hot-spots start to spread
“real” Internet widely available on mobile phones (standard browsers, decent data rates)
7.2 Mbit/s HSDPA, 1.4 Mbit/s HSUPA available in Germany, more than 100 operators support
HSPA worldwide, first LTE tests (>100 Mbit/s)
2009 – the story continues with netbooks, iphones, VoIPoWLAN…
Wireless systems:
Overview of the Development
cellular phones
1981:
NMT 450
satellites
1986:
NMT 900
1992:
GSM
1994:
DCS 1800
analog
digital
1984:
CT1
1987:
CT1+
1988:
InmarsatC
1991:
CDMA
1991:
D-AMPS
1993:
PDC
2000:
GPRS
wireless
LAN
1980:
CT0
1982:
InmarsatA
1983:
AMPS
cordless
phones
1989:
CT 2
1992:
Inmarsat-B
Inmarsat-M
1991:
DECT
1998:
Iridium
199x:
proprietary
1997:
IEEE 802.11
1999:
802.11b, Bluetooth
2000:
IEEE 802.11a
2001:
IMT-2000
200?:
Fourth Generation
(Internet based)
Worldwide wireless subscribers
(old prediction 1998)
700
600
500
Americas
Europe
Japan
others
total
400
300
200
100
0
1996
1997
1998
1999
2000
2001
Areas of research in mobile
communication

Wireless Communication
 transmission quality (bandwidth, error rate,
delay)
 modulation, coding, interference
 media access, regulations
 ...
Areas of research in mobile
communication

Mobility
 location dependent services
 location transparency
 quality of service support (delay, jitter,
security)
 ...
Areas of research in mobile
communication

Portability
 power consumption
 limited computing power, sizes of display, ...
 usability
 ...
Simple Reference Model

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The basic reference model used to structure
communication system.
In next slide figure a personal digital assistant
(PDA) which provides an example for a wireless
and portable device.
This PDA communicates with a base station in the
middle of the picture.
The base station consists of a radio transceiver
(sender & receiver) and an inter working unit
connecting the wireless link with the fixed link.
Simple Reference Model


The communication partner of the PDA, a
conventional computer, is shown on the righthand side.
Each N/W element (such as PDA, inter working
unit, computer), the figure shows the protocol
stack implemented in the system according to
the reference model.
Simple Reference Model used here
Application
Application
Transport
Transport
Network
Network
Data Link
Physical
Radio
Network
Network
Data Link
Data Link
Data Link
Physical
Physical
Physical
Medium
Simple Reference Model
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End-System, such as the PDA and computer in
the example need a full protocol stack comprising
the application, transport, network, data link and
physical layer.
Applications on the end-systems communicate
with each other using the lower layer services.
Intermediate system, such as the inter working
unit, do not necessarily need all of the layers.
Next slide to explain the functions of each layer in
more derail in a wireless and mobile environment.
Simple Reference Model
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Physical layer:
This is the lowest layer in a communication
system and is responsible for the conversion of a
stream of bits into signals that can be transmitted
on the sender side.
The physical layer of the receiver then transforms
the signals back into a bit stream.
For wireless communication the physical layer is
responsible for frequency selection, generation of
the carrier frequency, signal detection, modulation
of data onto a carrier frequency and encryption.
Simple Reference Model
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Data link layer:
The main tasks of this layer include accessing the
medium, multiplexing of different data streams,
correction of transmission errors, and
synchronization.
The data link layer is responsible for a reliable
point-to-point connection between two devices or
a point-to-multipoint connection between one
ender and several receivers.
Simple Reference Model
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Network layer:
This third layer is responsible for routing packets
through network or establishing a connection
between two entities over many other intermediate
systems.
Important topics are addressing, routing, device
location and handover between different networks.
Simple Reference Model
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Transport layer:
This layer is used in the reference model to
establish an end-to-end connection.
The quality of service, flow and congestion
control are relevant, especially if the transport
protocols known from the internet, TCP and UDP
are to be used over a wireless link.
Simple Reference Model
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Application layer:
Finally, the application are situated on top of all
transmission-oriented layers.
And support for multimedia applications, adaptive
applications that can handle the large variations in
transmission characteristics and wireless access to
the world wide web using a portable device.
Very demanding applications are video and
interactive gaming.