wireless networks(introduction)

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

wireless networks(introduction)

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