Wireless and Mobile Computing

Sajjad Ali Mushtaq

What is Wireless Communication ? Transmitting voice, data, video and other services data

using electromagnetic waves in open space (atmosphere)

Electromagnetic waves Travel at speed of light (c = 3x108 m/s) Has a frequency (f) and wavelength (λ)

c = f x λ Where c = wave speed

Higher frequency means higher energy The higher the energy the more penetrating are the

radiations

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Types of Wireless Communication

Celullar Wireless computer

network

Radio service

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Multiservice Point-to-Multipoint Wireless Network

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Electromagnetic Radiation Spectrum

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The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object has a different meaning, and is instead the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object.

Wavelength of Some Technologies

GSM Phones: frequency ~= 900

Mhz wavelength ~= 33cm

PCS Phones frequency ~= 1.8 Ghz wavelength ~= 17.5 cm

Bluetooth: frequency ~= 2.4Gz wavelength ~= 12.5cm

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Wireless Media Standards

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Types of Electromagnetic Carriers When the distance between the sender and receiver is short (e.g.

TV box and a remote control) infrared waves are used For long range distances between sender and receiver (e.g. TV

broadcasting and cellular service) both microwaves and radio waves are used

radio waves are ideal when large areas need to be covered and obstacles exist in the transmission path

microwaves are good when large areas need to be covered and no obstacles exist in the transmission path

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Wireless Applications (Services)

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Advantages and Disadvantages of Wireless Communication

advantages: mobility a wireless communication network is a solution in

areas where cables are impossible to install (e.g. hazardous areas, long distances etc.)

easier to maintain disadvantages:

has security vulnerabilities high costs for setting the infrastructure unlike wired comm., wireless comm. is influenced by

physical obstructions, climatic conditions, interference from other wireless devices

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Wireless RevolutionCellular is the fastest growing sector of communicationindustry (exponential growth since 1982,

Four generations of wireless (5G is on its way)

First Generation (1G): Analog 25 or 30 KHz FM, voice only, mostly vehicular communication

Second Generation (2G): Narrowband TDMA and CDMA, voice and low bit-rate data, portable units.2.5G increased data transmission capabilities

Third Generation (3G): Wideband TDMA and CDMA, voice and high bit-rate data, portable units

4G/5G

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THE RADIO PATENTS

Tesla filed his basic radio patent applications in 1897. They were granted in 1900.

Marconi's first patent application in America, filed on November 10, 1900, was turned down. Marconi's revised applications over the next three years were repeatedly rejected because of the priority of Tesla and other inventors.

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PATENTS

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Magnifying Transmitter

What was Magnified?

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History: Historical Overview It Started with the Telegraph ... “We call the electric telegraph the most perfect

invention of modern times ... as anything more perfect than this is scarcely conceivable, and we really begin to wonder what will be left for the next generation…”

An electrical telegraph is a telegraphy that uses electrical signals, usually conveyed via telecommunication lines or radio. The electromagnetic telegraph is a device for human-to-human transmission of coded text messages.

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Critical Attributes of Telecommunications Systems

Speed Ability to transmit information in real-time Electronic transmission: faster than transportation

Coverage Beyond regional: national and international in scale Metcalf’s Law: the more connected, the more useful

Reliability Cost Security

Transmitted information as knowledge, news, secrets Always an element of government oversight and control

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Origins of Coded Transmission

1793, Revolutionary France Aerial Telegraph, invented by Claude Chappe Extensive network throughout France

1840s, Samuel F. B. Morse Coded transmission via electronic means Rapidly spread throughout US and Europe International Telegraph Union (ITU) formed in

1865

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Submarine Telegraphy: High

Tech of the late 19th Century

1850: Dover-to-Calais, first submarine line 1858: First transatlantic cable

Breaks after 3 months! 1866: Relaid with higher quality cable Development of

cable materials, technology of laying, repair Typical “Performance”: 1870: London to Bombay in 4 minutes, 22 seconds 1901: London to British Guiana, 22 minutes 1924: Telegram around the world in 80 seconds

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Radio Telegraphy(also know as “Wireless”)

Radio technology Communicate with ships and other moving vehicles Messages sprayed into the “ether” crossing boundaries Downfall of the nationally supported monopolistic

telegraph companies 1896: Guglielmo Marconi

First demonstration of wireless telegraphy Built on work of Maxwell and Hertz to send and receive

Morse Code Based on long wave (>> 1 km), spark transmitter

technology, requiring very large, high power transmitters First used by British Army and Navy in the Boer War

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Wireless 1907: Commercial Trans-Atlantic Wireless Service

Huge ground stations: 30 x 100m antenna masts Beginning of the end for cable-based telegraphy

WW I: Rapid development of communications intelligence, intercept technology, cryptography

1920: Marconi discovers shortwave (<100 m) radio Longwave follow contour of land

Very high transmit power, 200 KW+ Shortwaves reflect, refract, and absorb, like light

Bounce off ionosphere Higher frequencies made possible by vacuum tube

(1906) Cheaper, smaller, better quality transmitters

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Broadband Wireless Technology

Higher data rates obtainable with broadband wireless technology Graphics, video, audio

Shares same advantages of all wireless services: convenience and reduced cost Service can be deployed faster than

fixed service No cost of cable plant Service is mobile, deployed almost

anywhere27

Limitations and Difficulties of Wireless Technologies

Wireless is convenient and less expensive Limitations and political and technical

difficulties inhibit wireless technologies Lack of an industry-wide standard Device limitations

E.g., small LCD on a mobile telephone can only displaying a few lines of text

E.g., browsers of most mobile wireless devices use wireless markup language (WML) instead of HTML

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Wireless Networks Compared to Fixed Networks

Higher loss-rates due to interference other EM signals, objects in path (multi-path, scattering)

Limited availability of useful spectrum frequencies have to be coordinated, useful frequencies are

almost all occupied Low transmission rates Higher delays, higher jitter

connection setup time for cellular in the second range, several hundred milliseconds for wireless LAN systems

Lower security, simpler active attacking radio interface accessible for everyone base station can be simulated, thus attracting calls from mobile

phones Always shared medium

secure access mechanisms important 30

Shifting Trends

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Impressive Wireless Infrastructure!

Satellite

Macro-CellMicro-Cell

UrbanIn-Building

Pico-Cell

Global

Suburban

dik ©In-Room(BlueTooth)

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Wireless Network Overlay

Satellite

Macro-CellMicro-Cell

Urban

In-Building

Pico-Cell

Global

Suburban

dik ©

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GSM Base Stations in Europe

Nokia PrimeSite

Ericsson RBS 2000

September 1997 35

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Design Challenges Hardware Design

Precise components Small, lightweight, low power Cheap High frequency operations System Design

Converting and transferring information High data rates Robust to noise and interference Supports many users

Network Design Connectivity and high speed Energy and delay constrains 37

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Text Book

WIRELESS COMMUNICATIONSAND NETWORKS

By William Stallings2nd Edition

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Transmission Fundamentals Signals for Conveying Information

Relationship between Data Rate and Bandwidth Analog and Digital Data Transmission

Analog and Digital Data Analog and Digital Signaling Analog and Digital Transmission

Channel Capacity Nyquist Bandwidth Shannon Capacity Formula

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Transmission Media Transmission media Transmission media classification Transmission Media characteristics and

design specifications Guided and Unguided media Wireless Transmission Frequencies Antennas Wireless Propagation

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Wireless Transmission Wireless Transmission Wireless Transmission Examples

terrestrial microwave satellite microwave broadcast radio Infrared

Wireless Transmission Systems Comparison Wireless Propagation Modes Multiplexing TDM, FDM WDM

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Communication Networks Comparison of basic communication

network technologies Circuit switching Packet switching Frame relay ATM

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Protocols and the TCP/IP Protocol Suite

Requirement of Protocol Why Layered Approach is Adopted Key Features of a Protocol Simple Protocol Architecture Addressing TCP/IP and OSI model General Networking Terminology

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Wireless Communication Technology

Underlying technology of wireless transmission

Encoding of analog and digital data for wireless transmission

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Antennas and Propagation Principles of radio and microwave

Antenna performance Wireless transmission modes Fading

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Antennas and Propagation Electric and Magnetic Field Coupling EM Radiations Period, Frequency, and Wavelength Phase Lag and Phase Lead Antennas Why??? Antenna Analogy Why Separate TX and RX Antennas Transmission are Required Transmission Line as an Antenna Working of an Antenna Far And Near Fields Antennas Characteristics

Polarization Antenna and Wavelength Antenna Gain Antenna Length 47

Signal Encoding Techniques Wireless transmission

Analog and digital data Analog and digital signals

Signal encoding techniques digital data, digital signal

NRZ, multilevel binary, biphase, modulation rate analog data, digital signal

PCM, DM digital data, analog signal

ASK, FSK, BFSK, PSK analog data, analog signal

AM, FM, PM48

Spread Spectrum Frequency Hopping Direct Sequence Spread Spectrum (DSSS) Code Division Multiple Access (CDMA)

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Coding and Error Control Forward Error Correction (FEC) Using redundancy for error detection Automatic Repeat Request (ARQ)

techniques

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Satellite Communications Geostationary satellites (GEOS) Low-earth orbiting satellites (LEOS) Medium-earth orbiting satellites (MEOS) Capacity allocation

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Cellular Wireless Networks Cellular wireless network design issues First generation analog (traditional

mobile telephony service) Second generation digital cellular

networks Time-division multiple access (TDMA) Code-division multiple access (CDMA)

Third generation networks Fourth generation networks

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GSM Global System for Mobile Communication

Digital Transmission ISDN compatibility Worldwide roaming in other GSM networks Provides a model for 3G Cellular systems (UMTS)

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Network Simulator 2• ns -2 stands for Network Simulator version 2.• ns -2:

• Is a discrete event simulator for networking research• Work at packet level.• Provide substantial support to simulate bunch of protocols

like TCP, UDP, FTP, HTTP and DSR.• Simulate wired and wireless network.• Is primarily Unix based but can also be used with Windows via Cygwin.

• Use TCL as its scripting language.• ns -2 is a standard experiment environment in research community.• NS2 is also being used for Network on Chip Simulations e.g. flit arrival rate, latency, jitter evaluation and topology comparison

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Software Defined RadiosApplication of Learned Concepts

Application of most of the concepts A Software Defined Radio (SDR) is a system

where components that have been typically implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, etc.) are instead implemented by means of software on a personal computer or embedded system.

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Thank You

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