CHAPTER CHAPTER Communication MediaCommunication Media
Chapter Objectives
• Present the functions and features of leading transmission media, both guided and open media
• Guided media– Twisted pair, coaxial cable, optical
fiber and mixed cabling• Open media (space)
– RF, Ultraviolet, Microwave and satellite
Chapter Modules
• Twisted Pair • Coaxial Cable • Optical Fiber • Mixed Cabling • Wireless • Microwave • Satellite Communication
MODULE
Twisted Pair Wire
Questions• What are the two different types of twisted
pair wires that are in use?• Why are the wires twisted?• Name the categories of wires and their
respective uses• What is the role played by bandwidth in the
quality of the wires?• What is a Plenum wire? Where is it used?• Name the types of twisted pair wires that
could be used in high speed LANs such as the Gigabit Ethernet LAN
• Describe the properties of the newer categories of twisted pair wires
Terminology to Remember
• Shielding (Conductive material)• Insulation (Non-conductive
material)– Casing (Plastic material)
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
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 an insulation against electric
shock
Twisted Pair Cable Illustration
Source: Black Box
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
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, 5e, 6 etc. 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
Areas of Application
• Phone lines• Used extensively in
telecommunications• LANs
Typical Twisted Pair Connection
Hub/Switch
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
Gigabit Ethernet Medium
• IEEE 802.3ab Twisted Pair– Cat 5e (350 MHz/ 1Gbps)
• IEEE 802.3z Fiber Optics
LAN Speed
• The following questions apply to the LAN shown in the next slide
• What is the speed of the network?• How could it be upgraded to a
higher speed?
Source: Black Box
Important Areas of Application for Twisted
Pair Wires• LAN
– RJ 45• 10baseT LANs operating at 10 Mbps • 100baseTX LANs operating at 100 Mbps• 1000baseT LANs operating at 1 Gbps • 8 wires
• Telephone wiring connections– RJ 11 (4 wires)– RJ 14 (6 wires)
Wiring a Building or Home
Questions• What are the two different types of twisted
pair wires that are in use?• Why are the wires twisted?• Name the categories of wires and their
respective uses• What is the role played by bandwidth in the
quality of the wires• What is a Plenum wire? Where is it used?• Name the types of twisted pair wires that
could be used in high speed LANs such as the Gigabit Ethernet LAN
• Describe the properties of the newer categories of twisted pair wires
END OF MODULEEND OF MODULE
MODULE
Coaxial Cable
Questions
• Name the two types of coaxial cables– Name different use for each type of cable
• Are they shielded?• What is the difference between
shielding and insulation? • Explain the current replacements for
coaxial cables both at the lower and higher end of the coaxial cable
Questions
• List the uses for thin and thick coaxial cables
• Name the types of LANs that use coaxial cables
A Description of the Coaxial Cable
Copper conductor
InsulatorShielding
Outer casing
Types of Coaxial Cables
• Thin coaxial – Lighter version– Thin Ethernet cable
• Thick coaxial– Original version– Standard Ethernet cable
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
Type of Thin Coaxial Cable
Used in LAN
• Standardized• 10Base2 cable
– 10M bps– Ethernet– Thin coaxial cable– Bus topology
Thick Coaxial Cable
• Compared to thin coaxial cable– Higher bandwidth – Less maneuverable – More expensive
Thick Coaxial Cables Used in Networks
• Standardized• 10Base5
– 10M bps– Ethernet– Thick coaxial cable – Bus topology
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
A Typical Coaxial Connection
Bus LAN
Coaxial Cable
A multi-drop connection
Components Used in Connecting a Computer to
a Coaxial Cable
Thin coaxial cable
T connector
Terminator
NetworkInterface
Card
An Example of the Use of Thick Coaxial Cables
Router
Backbone
Coaxial CableSwitch
Thick coaxial cable
Areas of Application for Coaxial Cables
• Ethernet bus LANs• Telephone trunks• Mainframe networks • Cable TVs
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 yesterday or perhaps
today as well – Connected to peripheral devices over
larger networks built on fiber-optic cables and twisted pair wires
Questions
• Name the two types of coaxial cables– Name different use for each type of cable
• Are they shielded?• Are they insulated?• Explain the current replacements for coaxial
cables both at the lower and higher end of the coaxial cable
• List the uses for thin and thick coaxial cables• Name the types of LANs that use coaxial
cables
END OF MODULEEND OF MODULE
MODULE
Fiber Cables
Questions• How does light travel in a fiber cable?
– Name the different types of optical transmission methods
• What is the most appealing aspect of fiber cables?– What are their consequences?
• What are the two different types of fiber cable connections used in practice?
• What are the two different materials that could be used in the production of fiber cables?
• Where are fiber cables used mostly in a LAN?
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
IncreasingSpeed
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– Multiple fiber strands can be included in
a cable of very small diameter
Fiber-Optic Cable Bandwidth
FiberOptics
Part Of Ultraviolet
Visible
Part Of Infra-red ?
The laser beam could also travel along a fiber optic cable
Fiber Cables
Usage of Fiber Optic Cables
• Long distance telephone cabling (trunks)
• LANs– Used in large networks as the
backbone• An example is the FDDI backbone used in
a number of campuses
– Used for extending cable limitations applicable to networking and other computing devices
A Simple Fiber LAN
Source: Black Box
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
Fiber Usage
• Network backbones• Extending distance between
network connections• Connecting high speed switches
Web Research
• Visit the following link at Corning for a tutorial on fiber optic technology http://www.corning.com/prod_svcs/index.html
• http://www.corningfiber.com/library/lib_premises.htm
Questions• How does light travel in a fiber cable?
– Name the different types of optical transmission methods
• What is the most appealing aspect of fiber cables?– What are their implications?
• What are the two different types of fiber cable connections used in practice?
• What are the two different materials that could be used in the production of fiber cables?
• Where are fiber cables used in the implementation of a LAN?
END OF MODULEEND OF MODULE
MODULE
Mixed Cabling
Questions
• Name a few different types of cable conversions that could be performed using a media converter
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
Media Interface
A Mixed Media LAN
Source: Black Box
Identify the components and relate to the previous slide.
Listing of Media and Communication Network
Services
Web Research: Find the meaning of the above terms
Web Research
• Obtain information on twisted pair wires that are of a higher quality than category 5
• Visit www.corning.com to get more information on fiber cables
END OF MODULEEND OF MODULE
MODULE
Microwave
Frequency Range and Propagation
• Microwave frequency range – 10e8 to 10e11– Bandwidth is nearly 10e11 Hz
• Propagation– Over space– Requires line-of-sight
• At higher frequencies the waves tend to behave like light waves
Line-of-Sight Requirement
3o miles limit to offsetEarth’s curvature.
Line of sight isrequired.
Characteristics
• Advantage– Cable laying is not required
• Disadvantage– Can easily be tapped– Encryption is one way of securing the
data from eavesdropping
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 reassignment of part of the
microwave bandwidth from military to civilian use
END OF MODULEEND OF MODULE
MODULE
Satellite Communication
Types
• Geosynchronous Earth Orbit (GEO)• Medium Earth Orbit (MEO)• Low Earth Orbit (LEO)
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
Medium Earth Orbit
• Fall to earth after a certain number of years of service
Low Earth Orbit
• Today’s 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
Propagation• Requires line-of-sight • Frequencies in use are higher than
those used in microwave– Upload 12 GHz– Download 16 GHz
• GEO– At least 3 satellites are required to
provide total global coverage
Total Global Coverage Using GEO Satellites
I
IIIII
12 GHZ16GHZUpload
Down load
3 satellites are required to cover the earth
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
Applications• Telecommunications
– Especially for inter-continental communication
• TV broadcast– Usage is increasing
• Navigation and other similar local applications– GPS
Factors Contributing to Expansion of Satellite
Communication
• Reassignment of military frequencies to civilian use
• Anticipated progress in the Iridium project
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