Transmission mediaGuided and Unguided By Norrima Mokhtar

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Transmission media-Guided and UnguidedBy
Norrima Mokhtar
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Objectives

• Present the functions and features of leading
  transmission media, both guided and open
  media(unguided)
• Guided media
• Twisted pair, coaxial cable, optical fiber and
  mixed cabling
• Open media (space)
• RF, Ultraviolet, Microwave and satellite

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Introduction

• Transmission media
• physical path between transmitter and receiver
• Examples
• the path between the satellite and the ground
  station in satellite communication systems
• the path between two computers

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Transmission media
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Introduction their effects

• The quality of transmission is determined by both
  the
• characteristics of the medium
• characteristics of the signal
• For guided media, the medium itself is more
  important in determining the limitations of
  transmission
• For unguided media, the bandwidth of the signal
  is more important than the medium because the
  medium is shared by many applications

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Operating frequencies
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Electromagnetic spectrum
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Guided Transmission Media

• Twisted Pair
• Coaxial Cable
• Optical Fiber
• Mixed Cabling

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MODULE

• Twisted Pair Wire

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Twisted pair cable
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Special terms

• Shielding (Conductive material)
• Insulation (Non-conductive material)
• Casing (Plastic material)

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Types and Purpose of Twisting

• Types
• Unshielded twisted pair (UTP)
• Shielded twisted pair (STP)
• Twisting
• Minimizes the effect of electromagnetic
  interference
• The electromagnetic field from one wire
  counterbalances the field from the other wire

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Effect of Noise on Parallel Lines
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Shielding and Insulation

• The cables are shielded from electro magnetic
  interference
• In both directions, from outside as well as
  inside
• The plastic casing is not to be considered as
  shielding
• It is not an insulation

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Unshielded Twisted Pair Cable
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UTP cable standard
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Shielded Twisted-Pair Cable
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Characteristics

• Cheap
• Easy to install
• Generally speaking, different frequencies may not
  be assigned to carry different channels on the
  same twisted pair wire
• Compared to coaxial cables, twisted pair wires
  have a lower bandwidth
• But, recent improvements have contributed to an
  increase in bandwidth
• Speed is proportional to bandwidth

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Quality and Categorization of the Wires

• Twisted pair wires are categorized according to
  their quality
• Category 3 wires are of the lower quality
• Category 5 wires are of higher quality
• Partly achieved by having a larger number of
  twists in the cable
• Higher category wires such as Cat 6 etc. are now
  available

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Areas of Application

• Phone lines
• Used extensively in telecommunications
• LANs

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Typical Twisted Pair Connection
Hub
Twisted Pair Wire
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Reasons for Its Increasing Popularity

• Better quality UTP is being produced
• Ease of installation superseding its other
  limitations
• A LAN to be configured with twisted pair wires
  requires a hub
• A hub based implementation is preferred because
  it is easy to install and manage

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Important Areas of Application for Twisted Pair
Wires

• LAN
• RJ 45
• 10baseT LANs operating at 10 Mbps
• 100baseTX LANs operating at 100 Mbps
• 8 wires
• Telephone wiring connections
• RJ 11 (4 wires)
• RJ 14 (6 wires)

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MODULE

• Coaxial Cable

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Types of Coaxial Cables

• Thin coaxial
• Lighter version
• Thin Ethernet cable
• RG-58 Thin Ethernet
• Thick coaxial
• Original version
• Standard Ethernet cable
• RG-8, RG-9, RG-11 Thick Ethernet
• RG-59 TV

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Thin Coaxial Cable

• Higher bandwidth than twisted pair wires
• Lower bandwidth compared with the thick coaxial
  able
• More flexible compared to thick coaxial cable
• Cheaper

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Type of Thin Coaxial Cable Used in LAN

• Standardized
• 10Base2 cable
• 10M bps
• Ethernet
• Bus topology

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Thick Coaxial Cable

• Compared to thin coaxial cable
• Higher bandwidth
• Less maneuverable
• More expensive

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Thick Coaxial Cables Used in Networks

• Standardized
• 10Base5
• 10M bps
• Ethernet
• Bus topology

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Overall Characteristics of the Coaxial Cables

• Relatively cheap compared to fiber-optic cables
• Wider bandwidth compared to twisted pair wires
• Good transmission characteristics
• Used in high-speed synchronous transmission
• Supports broadband communication
• Can be tapped for multi-drop connection

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A Typical Coaxial Connection
Bus LAN
Coaxial Cable
A multi-drop connection
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Components Used in Connecting a Computer to a
Coaxial Cable
Thin coaxial cable
T connector
Network Interface Card
Terminator
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An Example of the Use of Thick Coaxial Cables
Switch
Coaxial Cable
Router
Backbone
Thick coaxial cable
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Areas of Application for Coaxial Cables

• Ethernet bus LANs
• Telephone trunks
• Mainframe networks
• Cable TVs

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Future of Coaxial Cables

• Overall use is on the decline
• LANs (Lower End)
• Replaced by newer and better twisted pair wires
• Telephone trunks (Higher End)
• Fiber cables are replacing coaxial cables
• Mainframes of today
• Connected to peripheral devices over larger
  networks built on fiber-optic cables and twisted
  pair wires

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MODULE

• Fiber Cables

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Refraction
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Critical Angle
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Optical fiber
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1.core(62.5um,50um,8.3um) 2.cladding(125um) 3.Coa
ting(250um)
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Fiber types
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Light source

• Sending device called light source
• Receiving device called photosensitive cell
• (photodiode)
• Light source
• Light-emitting diode (LED)
• Cheap but unfocused
• Short distance
• Injection Laser diode (ILD)
• Expensive but focused
• Preserve the signal (long distance)

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Characteristics

• Very broad bandwidth
• Higher transmission speeds are possible
• Signals travel a longer distance
• No Electro-magnetic field
• No interference
• Signals are difficult to tap
• Smaller size

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Fiber Optics Transmission

• Light travels along the path of the fiber by
  bouncing around its edges
• Propagation methods
• Multi-mode step index
• Multi-mode graded index
• Single mode

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1.single-mode (8.3/125um,9.3/125um,10/125um)laser
2.Multi-mode (62.5/125um,50/125um)led 3.plastic
fiber optic laser(500um-2mm)
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A Simple Fiber LAN
Source Black Box
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Types and Cost

• Types
• Regular glass fibers
• Plastic fibers
• Purer the fibers the better the transmission
  characteristics
• Cost
• Fiber cables are costlier than twisted pair wires
  and coaxial cables
• The cost has declined over a period of time
• Plastic fiber cables are cheaper than glass fiber
  cables

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MODULE

• Mixed Cabling

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Mixed Cabling

• LANs may be constructed with different segments
  having different cable types
• Devices are available for interfacing the
  different media
• Optical fiber is often used for high speed links
  within a LAN of mixed speed ratings

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Media Interface
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A Mixed Media LAN
Source Black Box
Identify the components and relate to the
previous slide.
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Listing of Media and Communication Network
Services
Web Research Find the meaning of the above terms
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Unguided media
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Unguided media

• Omnidirectional
• Signal radiates in all directions
• Good for broadcast
• Inexpensive antenna
• Directional
• Signal radiates in a single direction
• Usually requires parabolic (dish) antenna
• 2-40 GHz (microwave)
• Also works with lasers

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Bands
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MODULE

• Microwave

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Frequency Range and Propagation

• Microwave frequency range
• 10e8 to 10e11
• Bandwidth is nearly 10e11 Hz
• Propagation
• Over space
• At higher frequencies the waves tend to behave
  like light waves

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Line-of-Sight Requirement
Line of sight is required.
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What is line of sight

• Two antennae are shown each having the same
  height.
• Line-of-sight transmission means the transmitting
  and receiving antennae can "see" each other as
  shown.
• The maximum distance at which they can see each
  other, dLOS, occurs when the sighting line just
  grazes the earth's surface.

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Characteristics

• Advantage
• Cable laying is not required
• Disadvantage
• Can easily be tapped
• Encryption is one way of securing the data from
  eavesdropping

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Applications Areas

• Telecommunications
• Used extensively
• LAN
• Used for wireless connections
• WANs benefit from microwave
• Usage on the increase
• LANs and WANs area
• Fueled by FCC's(federal communications
  comission-US) reassignment of part of the
  microwave bandwidth from military to civilian use

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MODULE

• Satellite Communication

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Types

• Geosynchronous Earth Orbit (GEO)
• Medium Earth Orbit (MEO)
• Low Earth Orbit (LEO)

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Geosynchronous Earth Orbit (GEO)

• First satellites to be launched
• Remain stationary with respect to the position of
  the earth at a high altitude
• Balance between the gravity of the moon and the
  earth
• Appear to be stationary with respect to a
  position on earth

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Medium Earth Orbit

• Fall to earth after a certain number of years of
  service

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Low Earth Orbit

• Todays focus
• Touted to play an important role in global
  communications
• Several being launched under the Iridium project
• Usher a new era in global communications
• Support computer systems and personal
  communicant devices in communicating with one
  another

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Propagation

• Requires line-of-sight
• GEO
• At least 3 satellites are required to provide
  total global coverage

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Total Global Coverage Using GEO Satellites
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Upload
16GHZ
12 GHZ
Down load
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III
3 satellites are required to cover the earth
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Salient Features of Satellite Communications

• Uploading and downloading
• Uploading at 12 GHz
• Downloading at 16 Ghz
• Basic function
• Receive the signals from an earth station,
  amplify them and then transmit them back to
  another earth station

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Applications

• Telecommunications
• Especially for inter-continental communication
• TV broadcast
• Usage is increasing
• Navigation and other similar local applications
• GPS

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Transmission Impairment for both type guided and
unguided

• Attenuation
• Distortion
• Noise

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Attenuation
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Why dB?
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Distortion
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Noises
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Assignment by group- Must be submitted on
Monday2pm

• Describe transmission media for guided and
  unguided.
• Gives and describe transmission media
  considerations.
• Tutorial must be done in two sessions-mon4-6pm
  and wed4-6pm