Introduction.ppt wireless

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1. Wireless Networks
CS 6710
Spring 2010
Rajmohan Rajaraman

2. Outline of the course: Basic topics
Transmission Fundamentals
oAnalog and digital transmission
oChannel capacity
oAntennas, propagation modes, and fading
oSignal encoding techniques
Spread spectrum technology
Coding and error control
Cellular networks
Wireless LANs
oIEEE 802.11
oBluetooth

3. Outline: Advanced topics
WiMAX, Zigbee, UWB, 3G and 4G
Mobile Application platforms
Mobile IP, TCP for wireless
Multihop ad hoc networks
oMAC and routing protocols
oPower control and topology control
oCapacity of ad hoc networks
Sensor networks
oInfrastructure, MAC, and routing protocols
oAlgorithms for query processing

4. Wireless Comes of Age
Guglielmo Marconi invented the wireless telegraph in 1896
oCommunication by encoding alphanumeric characters in analog
signal
oSent telegraphic signals across the Atlantic Ocean
Communications satellites launched in 1960s
Advances in wireless technology
oRadio, television, mobile telephone, communication satellites
More recently
oSatellite communications, wireless networking, cellular
technology, ad hoc networks, sensor networks

5. Wireless communication systems
Target information systems: “Anytime, Anywhere,
Any form”
Applications: Ubiquitous computing and
information access
Market in continuous growth:
o35-60% annual growth of PCS
oNumber of subscribers:
•By 2001: over 700M mobile phones
•By 2003: 1 billion subscribers
•By 2005: 2 billion
•By 2009: 4.6 billion
Large diversity of standards and products
Confusing terminology

6. Limitations and difficulties
Wireless is convenient and less expensive
Limitations and political and technical
difficulties inhibit wireless technologies
Lack of an industry-wide standard
Device limitations
oE.g., small LCD on a mobile telephone can only
displaying a few lines of text
oE.g., browsers of most mobile wireless devices
use wireless markup language (WML) instead of
HTML
oSwitching speed of the material (e.g., silicon)

7. a
d
h
o
c
IMT200, WLAN,
GSM, TETRA, ...
Personal Travel Assistant,
PDA, laptop, GSM, cdmaOne,
WLAN, Bluetooth, ...

8. Wireless & Mobility
Wireless:
oLimited bandwidth
oBroadcast medium: requires multiple access schemes
oVariable link quality (noise, interference)
oHigh latency, higher jitter
oHeterogeneous air interfaces
oSecurity: easier snooping
Mobility:
oUser location may change with time
oSpeed of mobile impacts wireless bandwidth
oNeed mechanism for handoff
oSecurity: easier spoofing
Portability
oLimited battery, storage, computing, and UI

9. Classification of Wireless Systems
Personal communication systems
oFocus on voice communication
oLimited bit-rate data transmission
oLarge-scale mobility and coverage
oOperate over licensed frequency bands
Wireless LANs
oDesigned for high bit-rate transmission
oIP oriented
oLow-scale coverage
oUse unlicensed ISM frequency bands
Multihop ad hoc networks
oHave little or no infrastructure
oLow-scale coverage
oNeed new routing protocols
oEmerging applications

10. Transmission fundamentals
Electromagnetic signals
oTime domain
oFrequency domain
Data rate and bandwidth
Channel capacity
oNyquist theorem
oShannon capacity theorem
Analog and digital data transmission
Transmission media

12. QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.

13. Analog signaling

14. Digital signaling

16. Classification of transmission media
Transmission medium
oPhysical path between transmitter and receiver
Guided media
oWaves are guided along a solid medium
oE.g., copper twisted pair, copper coaxial cable, optical
fiber
Unguided media
oProvides means of transmission but does not guide
electromagnetic signals
oUsually referred to as wireless transmission
oE.g., atmosphere, outer space

17. Unguided media
Transmission and reception are achieved
by means of an antenna
Configurations for wireless transmission
oDirectional
oOmnidirectional

18. General frequency ranges
Microwave frequency range
o1 GHz to 40 GHz
oDirectional beams possible
oSuitable for point-to-point transmission
oUsed for satellite communications
Radio frequency range
o30 MHz to 1 GHz
oSuitable for omnidirectional applications
Infrared frequency range
oRoughly, 3x10
11
to 2x10
14
Hz
oUseful in local point-to-point multipoint applications within
confined areas

19. Terrestrial microwave
Description of common microwave antenna
oParabolic "dish", 3 m in diameter
oFixed rigidly and focuses a narrow beam
oAchieves line-of-sight transmission to receiving antenna
oLocated at substantial heights above ground level
Applications
oLong haul telecommunications service
oShort point-to-point links between buildings

20. Satellite microwave
Description of communication satellite
oMicrowave relay station
oUsed to link two or more ground-based microwave
transmitter/receivers
oReceives transmissions on one frequency band (uplink),
amplifies or repeats the signal, and transmits it on
another frequency (downlink)
Applications
oTelevision distribution
oLong-distance telephone transmission
oPrivate business networks

21. Broadcast radio
Description of broadcast radio antennas
oOmnidirectional
oAntennas not required to be dish-shaped
oAntennas need not be rigidly mounted to a precise
alignment
Applications
oBroadcast radio
•VHF and part of the UHF band; 30 MHZ to 1GHz
•Covers FM radio and UHF and VHF television

22. Infrared
Beyond the EHF spectrum
o10
12
to 10
14
Hz
Transceivers must be within line of sight or
reachable via reflection
oDoes not penetrate walls