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7/29/2019 Wireless Networks(Introduction)
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Wireless Networks
Chapter 1. Introduction
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What is Wireless Network?
A technology that enables two or more entities to
communicate without network cabling.
A Group of interconnected nodes that exchange
information and share resources through a wirelesstransmission medium.
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Mobility
Initially Internet and Telephone Networks were designed assumingthe user terminals are static
No change of location during a call/connection
A user terminals accesses the network always from a fixed location
Two aspects of mobility: user mobility: users communicate (wireless) anytime, anywhere, with
anyone.
Mobility means changing point of attachment to the network online
device portability: devices can be connected anytime, anywhere to the
network. Portability means changing point of attachment to the network offline
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Mobility
With regard to devices, the term wireless is used. This only describes the way ofaccessing a network or other communication partners, i.e., without a wire. Thewire is replaced by the transmission of electromagnetic waves through the air.
A communication device can thus exhibit one of the following characteristics:
Fixed and wired: This configuration describes the typical desktop computer in anoffice. Neither weight nor power consumption of the devices allow for mobileusage.
Mobile and wired: Many of todays laptops fall into this category; users carry thelaptop from one hotel to the next, reconnecting to the companys network via thetelephone network and a modem.
Fixed and wireless: wireless LANs in historic buildings
Mobile and wireless: Personal Digital Assistant (PDA), smart phones
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Why wireless network?
User Mobility and Flexibility
Reduced Cost (cheap infrastructure)
Cheaper to install and maintain.
Easily Expandable
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Applications
Emergencies: (an ambulance with a high-quality wireless connection to a
hospital) early transmission of patient data to the hospital,current status, first diagnosis.
replacement of a fixed infrastructure in case of earthquakes,hurricanes, fire etc.
Vehicles: position via GPS local ad-hoc network with vehicles close-by to prevent
accidents. In case of an accident, not only will the airbag be triggered, but
the police and ambulance service will be informed via anemergency call to a service provider.
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Digital Audio/Video Broadcasting-Terrestrial
Universal Mobile Telecommunication System
Global Positioning System
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Applications
Entertainment, education, ... outdoor Internet access
intelligent travel guide with up-to-datelocation dependent information
ad-hoc networks formulti user games
Replacement of fixed networks remote sensors, e.g., weather, earth activities.
It is impossible to wire remote sensors for weather forecasts or toprovide any environmental information.
Wireless connections (via satellite) can help this situation
cabling takes a long time and frequently proves to be tooinflexible.
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Mobile & Wireless Devices
Sensor
Embedded Controller
Pager Mobile Phones
Personal Digital Assistant (PDA)
Pocket Computer Notebook/Laptop
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Mobile devices
performance
Pager
receive only
tiny displays simple text
messages
Mobile phones
voice, data
simple text displays
PDA
simple graphical displays
character recognition simplified WWW
Palmtop
tiny keyboard
simple versions
of standard applications
Laptop
fully functional
standard applications
Sensors,
embedded
controllers
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Thank You
End of Chapter 1