Wireless Communication and
Networks
Introduction
Outline of the course: Basic
topics
Transmission Fundamentals
o Analog and digital transmission
o Channel capacity
o Antennas, propagation modes, and fading
o Signal encoding techniques
Spread spectrum technology
Coding and error control
Cellular networks
Wireless LANs
o IEEE 802.11
o Bluetooth
Outline: Advanced topics
WiMAX, Zigbee, UWB, 3G and 4G
Mobile Application platforms
Mobile IP, TCP for wireless
Multihop ad hoc networks
o MAC and routing protocols
o Power control and topology control
o Capacity of ad hoc networks
Sensor networks
o Infrastructure, MAC, and routing
protocols
o Algorithms for query processing
Wireless Comes of Age
Guglielmo Marconi invented the wireless telegraph
in 1896
o Communication by encoding alphanumeric characters in
analog signal
o Sent telegraphic signals across the Atlantic Ocean
Communications satellites launched in 1960s
Advances in wireless technology
o Radio, television, mobile telephone, communication
satellites
More recently
o Satellite communications, wireless networking,
cellular technology, ad hoc networks, sensor networks
Wireless communication
systems
Target information systems: “Anytime,
Anywhere, Any form”
Applications: Ubiquitous computing and
information access
Market in continuous growth:
o 35-60% annual growth of PCS
o Number 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
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
o E.g., small LCD on a mobile telephone can
only displaying a few lines of text
o E.g., browsers of most mobile wireless
devices use wireless markup language (WML)
instead of HTML
o Switching speed of the material (e.g.,
silicon)
oc
IMT200, WLAN, h
GSM, TETRA, ... ad
Personal Travel Assistant,
PDA, laptop, GSM, cdmaOne,
WLAN, Bluetooth, ...
Wireless & Mobility
Wireless:
o Limited bandwidth
o Broadcast medium: requires multiple access schemes
o Variable link quality (noise, interference)
o High latency, higher jitter
o Heterogeneous air interfaces
o Security: easier snooping
Mobility:
o User location may change with time
o Speed of mobile impacts wireless bandwidth
o Need mechanism for handoff
o Security: easier spoofing
Portability
o Limited battery, storage, computing, and UI
Classification of Wireless
Systems
Personal communication systems
o Focus on voice communication
o Limited bit-rate data transmission
o Large-scale mobility and coverage
o Operate over licensed frequency bands
Wireless LANs
o Designed for high bit-rate transmission
o IP oriented
o Low-scale coverage
o Use unlicensed ISM frequency bands
Multihop ad hoc networks
o Have little or no infrastructure
o Low-scale coverage
o Need new routing protocols
o Emerging applications
Transmission fundamentals
Electromagnetic signals
o Time domain
o Frequency domain
Data rate and bandwidth
Channel capacity
o Nyquist theorem
o Shannon capacity theorem
Analog and digital data transmission
Transmission media
Analog signaling
Digital signaling
Classification of transmission
media
Transmission medium
o Physical path between transmitter and receiver
Guided media
o Waves are guided along a solid medium
o E.g., copper twisted pair, copper coaxial
cable, optical fiber
Unguided media
o Provides means of transmission but does not
guide electromagnetic signals
o Usually referred to as wireless transmission
o E.g., atmosphere, outer space
Unguided media
Transmission and reception are
achieved by means of an antenna
Configurations for wireless
transmission
o Directional
o Omnidirectional
General frequency ranges
Microwave frequency range
o 1 GHz to 40 GHz
o Directional beams possible
o Suitable for point-to-point transmission
o Used for satellite communications
Radio frequency range
o 30 MHz to 1 GHz
o Suitable for omnidirectional applications
Infrared frequency range
o Roughly, 3x1011 to 2x1014 Hz
o Useful in local point-to-point multipoint
applications within confined areas
Terrestrial microwave
Description of common microwave antenna
o Parabolic "dish", 3 m in diameter
o Fixed rigidly and focuses a narrow beam
o Achieves line-of-sight transmission to
receiving antenna
o Located at substantial heights above ground
level
Applications
o Long haul telecommunications service
o Short point-to-point links between buildings
Satellite microwave
Description of communication satellite
o Microwave relay station
o Used to link two or more ground-based microwave
transmitter/receivers
o Receives transmissions on one frequency band
(uplink), amplifies or repeats the signal, and
transmits it on another frequency (downlink)
Applications
o Television distribution
o Long-distance telephone transmission
o Private business networks
Broadcast radio
Description of broadcast radio antennas
o Omnidirectional
o Antennas not required to be dish-shaped
o Antennas need not be rigidly mounted to a
precise alignment
Applications
o Broadcast radio
• VHF and part of the UHF band; 30 MHZ to 1GHz
• Covers FM radio and UHF and VHF television
Infrared
Beyond the EHF spectrum
o 1012 to 1014 Hz
Transceivers must be within line of
sight or reachable via reflection
o Does not penetrate walls
