TOBB ETU Bil557 Kablosuz Aglar

1
TOBB ETU Bil557 Kablosuz Aglar

• Bahar 2007
• Çarsamba 0830 1200
• Sinif 175
• Bülent Tavli
• Oda 169
• btavli_at_etu.edu.tr

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Ders Bilgileri - I

• Bu derste neler ögrenecegiz?
• Geleneksel cep telefonu (cellular networks) ve
  kablosuz aglari (wireless networks) olanakli
  kilan kavramlar nelerdir?
• Kablosuz iletisim sistemi tasarimlarindaki temel
  yapilar ve sistem performansini yükseltme
  yöntemleri nelerdir?
• Kablosuz iletisimi konusunda en son asama
  (state-of-the-art) arastirma nasil yapilir?
• Bu ders için nasil bir altyapi gerekli?
• Temel matematiksel analiz
• Isaret isleme (signal processing)
• Elektronik iletisim (Telecommunications)
• Programlama (C/C ve Matlab)
• Eger bu konularda yetersizseniz ?
• Bu dersi yine de alabilirsiniz
• Ama ek çaba ve zaman harcamaniz gerekecek
• Bilgi dagarciginizi genisletmek için ve son
  derece popüler bir konuda verimli arastirma
  yapabilmek için mükemmel bir firsat

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Ders Bilgileri - II

• Ana kaynak
• Wireless Communications and Networks, 2nd
  Edition, Prentice Hall by W. Stallings
• Bu kitaptan kesinlikle bir tane edinmelisiniz!
• http//williamstallings.com/Wireless/Wireless2e.ht
  ml
• Yardimci kaynaklar
• Wireless Communications Principles and Practice
  , 2nd Edition, Prentice Hall by T. Rappaport
• Ad Hoc Wireless Networks Architectures and
  Protocols, Prentice Hall by C. S. R. Murthy and
  B. S. Manoj
• Mobile Ad Hoc Networks Energy-Efficient
  Real-Time Data Communications, Springer by B.
  Tavli and W. B. Heinzelman
• Derste dagitilacak makaleler ve diger belgeler
• Network Simulator (ns-2)
• http//nsnam.isi.edu/nsnam/index.php/User_Informat
  ion

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Ders Bilgileri - III

• Notlandirma
• Ödevler (iki haftada bir) 20
• Proje (rapor sunum) 30
• Arasinav 25
• Sonsinav 25
• Projeler kablosuz iletisim ve aglar hakkinda
  olmali
• Derinlemesine literatür taramasi, Benzetim
  (simulation), Analiz, Uygulama
• Tek basiniza veya en fazla üç kisilik gruplar
  halinde
• Dönem sonunda konferans bildirisi formatinda bir
  rapor verilecek ve konferans sunumu seklinde bir
  sunum yapilacak
• Proje takvimi
• Subat sonuna kadar projenizi belirleyip onay alin
• Dönemin son haftasi proje sunumu yapilacak
• Akademik ahlak
• Yardimlasmaniz tesvik edilmekle beraber kopye
  çekmeniz kesinlikle yasaktir

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Introduction to Wireless

• Chapter 1

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What is wireless communication?

• Any form of communication that does not require
  the transmitter and receiver to be in physical
  contact through guided media
• Electromagnetic wave propagated through
  free-space
• Radar, RF, Microwave, IR, Optical
• Simplex one-way communication (e.g., radio, TV)
• Half-duplex two-way communication but not
  simultaneous (e.g., push-to-talk radios)
• Full-duplex two-way communication (e.g.,
  cellular phones)
• Frequency-division duplex (FDD)
• Time-division duplex (TDD) simulated full-duplex

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Electromagnetic Specturm
1017
1019
109
1012
4.3x1014
7.5x1014
http//imagine.gsfc.nasa.gov/docs/ science/know_l1
/emspectrum.html
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Why use wireless communication?

• Provides mobility
• A user can send and receive messages no matter
  where he/she is located
• Added convenience / reduced cost
• Enables communications without adding expensive
  infrastructure
• Can easily setup temporary wireless LANs
  (disaster situations)
• Developing nations use cellular telephony rather
  than laying wires to each home
• Use resources only when sending or receiving
  signal

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Why is wireless different than wired?

• Noisy, time-varying channel
• BER varies by orders of magnitude
• Enviromental conditions affect transmission
• Shared medium
• Other users create interference
• Must develop ways to share the channel
• Bandwidth is limited
• TÜK, FCC determines the frequency allocation
• ISM band for unlicensed spectrum (902-928 MHz,
  2.4-2.5 GHz, 5.725-5.875 GHz)
• Requires intelligent signal processing and
  communications to make efficient use of limited
  bandwidth in error-prone environment

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Early forms of wireless communication

• Primitive
• Sound (e.g., beating of drums)
• Sight (e.g., smoke signals)
• PA (public address) system
• Disadvantages of these forms of communication
• Limited alphabets
• Noisy
• Broadcast (no privacy or security)
• Limited distance (or requires relaying which is
  unreliable)
• Require line-of-sight between transmitter and
  receiver

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Wireless Comes of Age

• 1893 Nikola Tesla demonstrated the first ever
  wireless information transmission in New York
  City
• 1897 Marconi demonstrated transmission of radio
  waves to a ship at sea 29 km away
• 1915 Wireless telephony established-- VA and
  Paris
• 1920's Radio broadcasting became popular
• 1930's TV broadcasting began
• 1946 First public mobile telephone service in US
• 1960's Bell Labs developed cellular concept--
  brought mobile telephony to masses
• 1960s Communications satellites launched
• Late 1970's IC technology advances enable
  affordable cellular telephony-- ushers in modern
  cellular era
• Early 1990s Cellular telephony in Türkiye
• 2007 ISTCell cellular service is introduced by
  TürkCell ?

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Some Milestones in Wireless Communications
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Modern Cellular Standards

• First generation (1G) systems (analog)
• 1979 NTT (Japan), FDMA, FM, 25 kHz channels,
  870-940 MHz)
• 1981 NMT (Sweden and Norway), FDMA, FM, 25 kHz,
  450-470 MHz
• 1983 AMPS (US), FDMA, FM, 30 kHz channels,
  824-894 MHz
• 1985 TACS (Europe), FDMA, FM, 25 kHz channels,
  900 MHz
• Second generation (2G) systems (digital)
• Supported voice and low-rate data (up to 9.6
  kbps)
• 1990 GSM (Europe), TDMA, GMSK, 200 kHz channels,
  890-960 MHz
• 1991 USDC/IS-54 (US), TDMA, p/4 DQPSK, 30 kHz
  channels, 824-894 MHz
• 1993 IS-95 (US), CDMA, BPSK/QPSK, 1.25 MHz
  channels, 824-894 MHz and 1.8-2.0 GHz
• 1993 CDPD (US) FHSS GMSK 30 kHz channels 824-894
  Mhz
• Enhanced 2G (2.5G) systems
• Increased data rates
• General Packet Radio System (GPRS) packet-based
  overlay to GSM, up to 171.2 kbps
• Enhanced Data rates for GSM Evolution (EDGE)
  modulation enhancements to GSM to support up to
  180 kbps
• 3rd generation (3G) systems
• Up to 2 Mbps
• Internet, VoIP
• 2004-2005 IMT-2000, 2000 MHz range - W-CDMA
  (UMTS), cdma2000, TD-SCMA

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Fast facts Cellular subscribers
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Fast facts cellular growth
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Wireless data standards

• IEEE 802.11 wireless LAN/ad-hoc networking, 1, 2
  or 11 Mbps, DSSS or FHSS with CSMA/CA
  RTS-CTS-ACK, 2.4 - 2.4835 GHz
• Bluetooth replacement for cables, short low
  power (1 or 100 mW), low cost, 1 piconets with
  master-slave operation
• HomeRF wireless home networking, 150 feet range,
  up to 10 devices, SWAP protocol
• IEEE 802.15 wireless PAN, modes for low (lt 10
  kbps, ZigBee), medium (up to 200 kbps), and high
  (gt 20 Mbps) data rates
• CDPD TCP/IP compatible packet transmission via
  digital overlay to existing analog cellular
  network, 19.2 kbps
• PCS modified cellular protocols, goals--low
  power, voice and moderate-rate data, small,
  inexpensive terminals, large coverage area
• MobileIP "routing support to permit IP nodes
  (hosts and routers) using either IPv4 or IPv6 to
  seamlessly roam among IP subnetworks and media
  types...maintenance of active TCP connections and
  UDP port bindings."
• WAP communications protocol and application
  environment, enables viewing of Internet content
  in special text format on special WAP-enabled
  devices

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Underlying concepts

• Electromagnetics
• Antennas, wave propagation, channel modeling
• Signals and systems
• Filtering, Fourier transforms, block-diagram
  design
• Digital signal processing
• Equalization, spread-spectrum, source coding
• Communications
• Modulation, noise analysis, channel capacity,
  channel coding

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Enabling Technologies

• Digital integrated circuits
• RF generation devices (efficient power amps,
  sleep modes, improved oscillators, smart
  antennas)
• Source coding (data compression)
• Modulation (improved efficiency)
• Multiple-access techniques (increase number of
  users)
• Channel coding/forward error correction (improve
  probability of successful reception)
• Software programmable radios

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Protocol stack - I
Source coding
Application
Packet re-ordering (e.g., TCP)
Transport
Routing (e.g., IP)
Network
Error correction, encryption
Data Link (MAC)
Modulation, power control, filtering
Physical
Channel

• Provides abstraction when designing layers
• We'll discuss each layer in turn...

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Protocol Stack - II
Application
Transport
Network
MAC
Physical
Channel
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Course Outline
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Part One Background

• Provides preview and context for rest of the
  course
• Covers basic topics
• Data Communications
• TCP/IP

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Chapter 2 Transmission Fundamentals

• Basic overview of transmission topics
• Data communications concepts
• Includes techniques of analog and digital data
  transmission
• Channel capacity
• Transmission media
• Multiplexing

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Chapter 3 Communication Networks

• Comparison of basic communication network
  technologies
• Circuit switching
• Packet switching
• Frame relay
• ATM

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Chapter 4 Protocols and the TCP/IP Protocol Suite

• Protocol architecture
• Overview of TCP/IP
• Open systems interconnection (OSI) reference
  model
• Internetworking

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Part Two Wireless Communication Technology

• Underlying technology of wireless transmission
• Encoding of analog and digital data for wireless
  transmission

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Chapter 5 Antennas and Propagation

• Principles of radio and microwave
• Antenna performance
• Wireless transmission modes
• Fading

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Chapter 6 Signal Encoding Techniques

• Wireless transmission
• Analog and digital data
• Analog and digital signals

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Chapter 7 Spread Spectrum

• Frequency hopping
• Direct sequence spread spectrum
• Code division multiple access (CDMA)

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Chapter 8 Coding and Error Control

• Forward error correction (FEC)
• Using redundancy for error detection
• Automatic repeat request (ARQ) techniques

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Part Three Wireless Networking

• Examines major types of networks
• Satellite-based networks
• Cellular networks
• Cordless systems
• Fixed wireless access schemes
• Use of mobile IP and Wireless Access Protocol
  (WAP) to provide Internet and Web access

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Chapter 9 Satellite Communications

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

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Chapter 10 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

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Chapter 11 Cordless Systems and Wireless Local
Loop

• Cordless systems
• Wireless local loop (WLL)
• Sometimes called radio in the loop (RITL) or
  fixed wireless access (FWA)

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Chapter 12 Mobile IP and Wireless Access Protocol

• Modifications to IP protocol to accommodate
  wireless access to Internet
• Wireless Application Protocol (WAP)
• Provides mobile users access to telephony and
  information services including Internet and Web
• Includes wireless phones, pagers and personal
  digital assistants (PDAs)

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Part Four Wireless Local Area Networks

• Examines underlying wireless LAN technology
• Examines standardized approaches to local
  wireless networking

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Chapter 13 Wireless LAN Technology

• Overview of LANs and wireless LAN technology and
  applications
• Transmission techniques of wireless LANs
• Spread spectrum
• Narrowband microwave
• Infrared

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Chapter 14 IEEE 802.11 Wireless LAN Standard

• Wireless LAN standards defined by IEEE 802.11
  committee

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Chapter 15 Bluetooth

• Bluetooth is an open specification for wireless
  communication and networking
• Personal computers
• Mobile phones
• Other wireless devices

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Advanced Topics

• Ad Hoc Networks
• Sensor Networks

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Part One

• Technical Background

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Transmission Fundamentals

• Chapter 2

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Electromagnetic Signal

• Function of time
• Can also be expressed as a function of frequency
• Signal consists of components of different
  frequencies

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Time-Domain Concepts

• Analog signal - signal intensity varies in a
  smooth fashion over time
• No breaks or discontinuities in the signal
• Digital signal - signal intensity maintains a
  constant level for some period of time and then
  changes to another constant level
• Periodic signal - analog or digital signal
  pattern that repeats over time
• s(t T ) s(t ) -lt t lt
• where T is the period of the signal

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Time-Domain Concepts

• Aperiodic signal - analog or digital signal
  pattern that doesn't repeat over time
• Peak amplitude (A) - maximum value or strength of
  the signal over time typically measured in volts
• Frequency (f )
• Rate, in cycles per second, or Hertz (Hz) at
  which the signal repeats

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Time-Domain Concepts

• Period (T ) - amount of time it takes for one
  repetition of the signal
• T 1/f
• Phase (?) - measure of the relative position in
  time within a single period of a signal
• Wavelength (?) - distance occupied by a single
  cycle of the signal
• Or, the distance between two points of
  corresponding phase of two consecutive cycles

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Sine Wave Parameters

• General sine wave
• s(t ) A sin(2?ft ?)
• Figure 2.3 shows the effect of varying each of
  the three parameters
• (a) A 1, f 1 Hz, ? 0 thus T 1s
• (b) Reduced peak amplitude A0.5
• (c) Increased frequency f 2, thus T ½
• (d) Phase shift ? ?/4 radians (45 degrees)
• note 2? radians 360 1 period

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Sine Wave Parameters
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Time vs. Distance

• When the horizontal axis is time, as in Figure
  2.3, graphs display the value of a signal at a
  given point in space as a function of time
• With the horizontal axis in space, graphs display
  the value of a signal at a given point in time as
  a function of distance
• At a particular instant of time, the intensity of
  the signal varies as a function of distance from
  the source

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Frequency-Domain Concepts

• Fundamental frequency - when all frequency
  components of a signal are integer multiples of
  one frequency, its referred to as the
  fundamental frequency
• Spectrum - range of frequencies that a signal
  contains
• Absolute bandwidth - width of the spectrum of a
  signal
• Effective bandwidth (or just bandwidth) - narrow
  band of frequencies that most of the signals
  energy is contained in

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Frequency-Domain Concepts

• Any electromagnetic signal can be shown to
  consist of a collection of periodic analog
  signals (sine waves) at different amplitudes,
  frequencies, and phases
• The period of the total signal is equal to the
  period of the fundamental frequency

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Relationship between Data Rate and Bandwidth

• The greater the bandwidth, the higher the
  information-carrying capacity
• Conclusions
• Any digital waveform will have infinite bandwidth
• BUT the transmission system will limit the
  bandwidth that can be transmitted
• AND, for any given medium, the greater the
  bandwidth transmitted, the greater the cost
• HOWEVER, limiting the bandwidth creates
  distortions

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Data Communication Terms

• Data - entities that convey meaning, or
  information
• Signals - electric or electromagnetic
  representations of data
• Transmission - communication of data by the
  propagation and processing of signals

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Examples of Analog and Digital Data

• Analog
• Video
• Audio
• Digital
• Text
• Integers

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Analog Signals

• A continuously varying electromagnetic wave that
  may be propagated over a variety of media,
  depending on frequency
• Examples of media
• Copper wire media (twisted pair and coaxial
  cable)
• Fiber optic cable
• Atmosphere or space propagation
• Analog signals can propagate analog and digital
  data

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Digital Signals

• A sequence of voltage pulses that may be
  transmitted over a copper wire medium
• Generally cheaper than analog signaling
• Less susceptible to noise interference
• Suffer more from attenuation
• Digital signals can propagate analog and digital
  data

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Analog Signaling
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Digital Signaling
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Reasons for Choosing Data and Signal Combinations

• Digital data, digital signal
• Equipment for encoding is less expensive than
  digital-to-analog equipment
• Analog data, digital signal
• Conversion permits use of modern digital
  transmission and switching equipment
• Digital data, analog signal
• Some transmission media will only propagate
  analog signals
• Examples include optical fiber and satellite
• Analog data, analog signal
• Analog data easily converted to analog signal

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Analog Transmission

• Transmit analog signals without regard to content
  
• Attenuation limits length of transmission link
• Cascaded amplifiers boost signals energy for
  longer distances but cause distortion
• Analog data can tolerate distortion
• Introduces errors in digital data

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Digital Transmission

• Concerned with the content of the signal
• Attenuation endangers integrity of data
• Digital Signal
• Repeaters achieve greater distance
• Repeaters recover the signal and retransmit
• Analog signal carrying digital data
• Retransmission device recovers the digital data
  from analog signal
• Generates new, clean analog signal

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About Channel Capacity

• Impairments, such as noise, limit data rate that
  can be achieved
• For digital data, to what extent do impairments
  limit data rate?
• Channel Capacity the maximum rate at which data
  can be transmitted over a given communication
  path, or channel, under given conditions

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Concepts Related to Channel Capacity

• Data rate - rate at which data can be
  communicated (bps)
• Bandwidth - the bandwidth of the transmitted
  signal as constrained by the transmitter and the
  nature of the transmission medium (Hertz)
• Noise - average level of noise over the
  communications path
• Error rate - rate at which errors occur
• Error transmit 1 and receive 0 transmit 0 and
  receive 1

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Nyquist Bandwidth

• For binary signals (two voltage levels)
• C 2B
• With multilevel signaling
• C 2B log2 M
• M number of discrete signal or voltage levels

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Signal-to-Noise Ratio

• Ratio of the power in a signal to the power
  contained in the noise thats present at a
  particular point in the transmission
• Typically measured at a receiver
• Signal-to-noise ratio (SNR, or S/N)
• A high SNR means a high-quality signal, low
  number of required intermediate repeaters
• SNR sets upper bound on achievable data rate

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Shannon Capacity Formula

• Equation
• Represents theoretical maximum that can be
  achieved
• In practice, only much lower rates achieved
• Formula assumes white noise (thermal noise)
• Impulse noise is not accounted for
• Attenuation distortion or delay distortion not
  accounted for

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Example of Nyquist and Shannon Formulations

• Spectrum of a channel between 3 MHz and 4 MHz
  SNRdB 24 dB
• Using Shannons formula

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Example of Nyquist and Shannon Formulations

• How many signaling levels are required?

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Classifications of Transmission Media

• Transmission Medium
• Physical path between transmitter and receiver
• Guided Media
• Waves are guided along a solid medium
• E.g., copper twisted pair, copper coaxial cable,
  optical fiber
• Unguided Media
• Provides means of transmission but does not guide
  electromagnetic signals
• Usually referred to as wireless transmission
• E.g., atmosphere, outer space

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Unguided Media

• Transmission and reception are achieved by means
  of an antenna
• Configurations for wireless transmission
• Directional
• Omnidirectional

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General Frequency Ranges

• Microwave frequency range
• 1 GHz to 40 GHz
• Directional beams possible
• Suitable for point-to-point transmission
• Used for satellite communications
• Radio frequency range
• 30 MHz to 1 GHz
• Suitable for omnidirectional applications
• Infrared frequency range
• Roughly, 3x1011 to 2x1014 Hz
• Useful in local point-to-point multipoint
  applications within confined areas

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Terrestrial Microwave

• Description of common microwave antenna
• Parabolic "dish", 3 m in diameter
• Fixed rigidly and focuses a narrow beam
• Achieves line-of-sight transmission to receiving
  antenna
• Located at substantial heights above ground level
  
• Applications
• Long haul telecommunications service
• Short point-to-point links between buildings

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Satellite Microwave

• Description of communication satellite
• Microwave relay station
• Used to link two or more ground-based microwave
  transmitter/receivers
• Receives transmissions on one frequency band
  (uplink), amplifies or repeats the signal, and
  transmits it on another frequency (downlink)
• Applications
• Television distribution
• Long-distance telephone transmission
• Private business networks

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Broadcast Radio

• Description of broadcast radio antennas
• Omnidirectional
• Antennas not required to be dish-shaped
• Antennas need not be rigidly mounted to a precise
  alignment
• Applications
• Broadcast radio
• VHF and part of the UHF band 30 MHZ to 1GHz
• Covers FM radio and UHF and VHF television

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Multiplexing

• Capacity of transmission medium usually exceeds
  capacity required for transmission of a single
  signal
• Multiplexing - carrying multiple signals on a
  single medium
• More efficient use of transmission medium

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Multiplexing
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Reasons for Widespread Use of Multiplexing

• Cost per kbps of transmission facility declines
  with an increase in the data rate
• Cost of transmission and receiving equipment
  declines with increased data rate
• Most individual data communicating devices
  require relatively modest data rate support

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Multiplexing Techniques

• Frequency-division multiplexing (FDM)
• Takes advantage of the fact that the useful
  bandwidth of the medium exceeds the required
  bandwidth of a given signal
• Time-division multiplexing (TDM)
• Takes advantage of the fact that the achievable
  bit rate of the medium exceeds the required data
  rate of a digital signal

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Frequency-division Multiplexing
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Time-division Multiplexing
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