CHAPTER Communication 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

Source:

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

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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 Insulator Shielding 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 Network Interface Card

An Example of the Use of Thick Coaxial Cables Router Backbone Coaxial Cable Switch 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

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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 Increasing Speed

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 Fiber Optics 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 ndex.html ndex.html b_premises.htm b_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?

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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 to get more information on fiber cableswww.corning.com

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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 offset Earths curvature. Line of sight is required.

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

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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 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

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 GHZ 16GHZ Upload 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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