Transmission MediaTransmission Media

Semester: 131Semester: 131

Course: CSET 221 Computer NetworkingCourse: CSET 221 Computer Networking

Instructor: Farhan KhanInstructor: Farhan Khan

Computer Science & Engineering Technology UnitComputer Science & Engineering Technology Unit

Hafr Al-Batin Community CollegeHafr Al-Batin Community College

OutlineOutline Guided MediaGuided Media

Twisted-Pair CableTwisted-Pair Cable UTPUTP STPSTP

Coaxial CableCoaxial Cable Fiber-Optic CableFiber-Optic Cable

MultimodeMultimode Single ModeSingle Mode

Unguided MediaUnguided Media Radio WavesRadio Waves MicrowavesMicrowaves InfraredInfrared

22

33

Physical LayerPhysical Layer

Transmission Media and Physical Transmission Media and Physical LayerLayer Computer and other Computer and other

telecommunication devices use telecommunication devices use signals to represent data. signals to represent data.

Signals are transmitted from one Signals are transmitted from one device to another in the form of device to another in the form of electromagnetic energy, which is electromagnetic energy, which is propagated through transmission propagated through transmission media.media.

44

55

Classes of Transmission Classes of Transmission MediaMedia

66

Guided MediaGuided Media Guided media are those that provide a Guided media are those that provide a

conduit from one device to another. conduit from one device to another. Signal travelling along any of these Signal travelling along any of these

media is directed and contained by media is directed and contained by the physical limits of the medium.the physical limits of the medium.

IncludeInclude twisted-pair cablestwisted-pair cables coaxial cablescoaxial cables fiber-optic cablesfiber-optic cables

77

Twisted-Pair CableTwisted-Pair Cable

Twisted-Pair CableTwisted-Pair Cable A twisted pair consists of two A twisted pair consists of two

conductors (normally copper), each conductors (normally copper), each with its own plastic insulation, with its own plastic insulation, twisted together.twisted together.

Twisting cancels out electrical noise Twisting cancels out electrical noise from adjacent pairs (crosstalk) and from adjacent pairs (crosstalk) and from other noise sources.from other noise sources.

88

99

UTP – Unshielded Twisted Pair STP –Shielded Twisted Pair

UTP and STP CablesUTP and STP Cables

UTP and STP CablesUTP and STP Cables STP cable has a metal foil or braided-STP cable has a metal foil or braided-

mesh covering that encases each mesh covering that encases each pair of insulated conductors.pair of insulated conductors.

Although metal casing improves the Although metal casing improves the quality of cable by preventing the quality of cable by preventing the penetration of noise or crosstalk, it is penetration of noise or crosstalk, it is bulkier and more expensive.bulkier and more expensive.

1010

1111

Categories of UTP/STP Categories of UTP/STP CablesCables

1212

Categories of UTP/STP Categories of UTP/STP CablesCables

CategoryCategory BandwidthBandwidth Digital/AnalogDigital/Analog UseUse

11 very lowvery low AnalogAnalog TelephoneTelephone

22 < 2 MHz< 2 MHz Analog/digitalAnalog/digital 4Mbps token ring4Mbps token ring

33 16 MHz16 MHz DigitalDigital 10-100 Mbps Ethernet10-100 Mbps Ethernet

44 20 MHz20 MHz DigitalDigital 16 Mbps token ring16 Mbps token ring

55 100 MHz100 MHz DigitalDigital 100 – 1000 Mbps Ethernet100 – 1000 Mbps Ethernet

5E5E 100 MHz100 MHz DigitalDigital 100 – 1000 Mbps Ethernet100 – 1000 Mbps Ethernet

66 250 MHz250 MHz DigitalDigital 1 – 10 Gbps Ethernet1 – 10 Gbps Ethernet

6A6A 500 MHz500 MHz DigitalDigital 1 – 10 Gbps Ethernet1 – 10 Gbps Ethernet

77 600 MHz600 MHz DigitalDigital 10 Gbps Ethernet10 Gbps Ethernet

7A7A 1000 MHz1000 MHz DigitalDigital 40-100 Gbps Ethernet40-100 Gbps Ethernet

UTP ConnectorsUTP Connectors RJ45 (Registered Jack) is the most common UTP connector.RJ45 (Registered Jack) is the most common UTP connector. RJ45 is a keyed connector, meaning the connector can be RJ45 is a keyed connector, meaning the connector can be

inserted in only one way.inserted in only one way.

1313

RJ – Registered Jack

1414

Coaxial CableCoaxial Cable

Coaxial CableCoaxial Cable Coax has a central core conductor of solid Coax has a central core conductor of solid

or stranded wire (usually copper) enclosed or stranded wire (usually copper) enclosed in an insulating sheath, which is, in turn, in an insulating sheath, which is, in turn, encased in an outer conductor of metal encased in an outer conductor of metal foil, braid, or a combination of the two.foil, braid, or a combination of the two.

The outer metallic wrapping serves both The outer metallic wrapping serves both as a shield against noise and as a second as a shield against noise and as a second conductor, which completes the circuit. conductor, which completes the circuit.

This outer conductor is also enclosed in an This outer conductor is also enclosed in an insulating sheath, and the whole cable is insulating sheath, and the whole cable is protected by a plastic cover.protected by a plastic cover.

1515

Categories of Coaxial Categories of Coaxial CablesCables Each Radio Government (RG) number denotes a unique set Each Radio Government (RG) number denotes a unique set

of physical specifications, including the wire gauge of the of physical specifications, including the wire gauge of the inner conductor, the thickness and type of the inner inner conductor, the thickness and type of the inner insulator, the construction of the shield, and the size and insulator, the construction of the shield, and the size and type of the outer casing.type of the outer casing.

1616

RG – Radio Government

1717

BNC ConnectorsBNC Connectors BBayonet ayonet NNetwork etwork CConnectoronnector

aka. Bayonet Neil-Concelmanaka. Bayonet Neil-Concelman Used with coaxial cablesUsed with coaxial cables Three popular types are BNC connector, BNC T Three popular types are BNC connector, BNC T

connector, BNC Terminator.connector, BNC Terminator.

1818

Optical FiberOptical Fiber Fiber-Optic cable is made of glass or Fiber-Optic cable is made of glass or

plastic and transmits signals in the plastic and transmits signals in the form of light.form of light.

Based on physics of lightBased on physics of light

Optical FiberOptical Fiber A glass or plastic core is surrounded by a A glass or plastic core is surrounded by a

cladding of less dense glass or plastic. cladding of less dense glass or plastic. The difference in density of the two The difference in density of the two

materials must be such that a beam of materials must be such that a beam of light moving through the core is reflected light moving through the core is reflected off the cladding instead of being refracted off the cladding instead of being refracted into it.into it.

1919

Propagation ModesPropagation Modes

2020

Propagation ModesPropagation Modes Multimode is so named because multiple beams Multimode is so named because multiple beams

from a light source move through the core in from a light source move through the core in different paths.different paths.

Multimode step-index fiberMultimode step-index fiber Density of the core remains constant from the Density of the core remains constant from the

center to the edgescenter to the edges Beam of light moves through this constant Beam of light moves through this constant

density in a straight line until it reaches the density in a straight line until it reaches the interface of the core and the cladding.interface of the core and the cladding.

At the interface, there is an abrupt change to a At the interface, there is an abrupt change to a lower density that alters the angle of the lower density that alters the angle of the beam’s motion. The term step index refers to beam’s motion. The term step index refers to the suddenness of this change.the suddenness of this change.

2121

Propagation ModesPropagation Modes Multimode graded-index FiberMultimode graded-index Fiber

The word index here refers to the index of The word index here refers to the index of refraction that is related to density.refraction that is related to density.

A graded-index fiber, is one with varying A graded-index fiber, is one with varying densities. Density is highest at the center of the densities. Density is highest at the center of the core and decreases gradually to its lowest at the core and decreases gradually to its lowest at the edge. edge.

Single mode FiberSingle mode Fiber Single mode uses step-index fiber and a highly Single mode uses step-index fiber and a highly

focused source of light that limits beams to a focused source of light that limits beams to a small range of angles, all close to the horizontal.small range of angles, all close to the horizontal.

2222

2323

Propagation ModesPropagation Modes

2424

Fiber SizesFiber Sizes

2525

Fiber ConstructionFiber Construction

Fiber ConstructionFiber Construction Outer jacket is made of either PVC or Outer jacket is made of either PVC or

Teflon.Teflon. Inside the jacket are Kevlar strands to Inside the jacket are Kevlar strands to

strengthen the cable. Kevlar is a strong strengthen the cable. Kevlar is a strong material used in the fabrication of material used in the fabrication of bulletproof vests.bulletproof vests.

Below the Kevlar is another plastic Below the Kevlar is another plastic coating to cushion the fiber. The fiber is coating to cushion the fiber. The fiber is at the center of the cable, and it at the center of the cable, and it consists of cladding and core.consists of cladding and core.

2626

2727

Fiber-Optic Cable Fiber-Optic Cable ConnectorsConnectors

Fiber-Optic Cable Fiber-Optic Cable ConnectorsConnectors

Subscriber channel (SC) connector is Subscriber channel (SC) connector is used in cable TV. It uses a push/pull used in cable TV. It uses a push/pull locking system.locking system.

Straight-tip (ST) connector is used for Straight-tip (ST) connector is used for connecting cable to networking devices. connecting cable to networking devices. It uses a bayonet locking system and is It uses a bayonet locking system and is more reliable than SC.more reliable than SC.

MT-RJ is a new connector with the same MT-RJ is a new connector with the same size as RJ-45size as RJ-45

2828

Advantages of Fiber-Optic Advantages of Fiber-Optic CableCable Fiber-Optic cable has several advantages Fiber-Optic cable has several advantages

over metallic cableover metallic cable Higher bandwidth, less signal Higher bandwidth, less signal

attenuation, immunity to attenuation, immunity to electromagnetic interference, resistance electromagnetic interference, resistance to corrosive materials, light weight, to corrosive materials, light weight, more immune to tapping.more immune to tapping.

Disadvantages: Installation/maintenance Disadvantages: Installation/maintenance [need expertise], Unidirectional [need expertise], Unidirectional [propagation of light is unidirectional], [propagation of light is unidirectional], Cost.Cost.

2929

3030

Unguided Media: Unguided Media: WirelessWireless Transport electromagnetic waves Transport electromagnetic waves

without using a physical conductorwithout using a physical conductor Radio WavesRadio Waves MicrowavesMicrowaves InfraredInfrared

Often referred to as wireless Often referred to as wireless communicationcommunication

Electromagnetic Electromagnetic SpectrumSpectrum Figure shows the part of the electromagnetic Figure shows the part of the electromagnetic

spectrum, ranging from 3 kHz to 900 THz, used spectrum, ranging from 3 kHz to 900 THz, used for wireless communication. for wireless communication.

3131

3232

Propagation MethodsPropagation Methods

Ground PropagationGround Propagation In ground propagation, radio waves travel In ground propagation, radio waves travel

through the lowest portion of the through the lowest portion of the atmosphere, along the earth. atmosphere, along the earth.

These low-frequency signals emanate in These low-frequency signals emanate in all directions from the transmitting all directions from the transmitting antenna and follow the curvature of the antenna and follow the curvature of the planet. planet.

Distance depends on the amount of power Distance depends on the amount of power in the signal: The greater the power, the in the signal: The greater the power, the greater the distance. greater the distance.

3333

Sky PropagationSky Propagation In sky propagation, higher-frequency In sky propagation, higher-frequency

radio waves radiate upward into the radio waves radiate upward into the ionosphere (the layer of atmosphere ionosphere (the layer of atmosphere where particles exist as ions) where where particles exist as ions) where they are reflected back to earth. they are reflected back to earth.

This type of transmission allows for This type of transmission allows for greater distances with lower output greater distances with lower output power. power.

3434

Line-of-Sight Line-of-Sight PropagationPropagation In line-of-sight propagation, very In line-of-sight propagation, very

high-frequency signals are high-frequency signals are transmitted in straight lines directly transmitted in straight lines directly from antenna to antenna. from antenna to antenna.

Antennas must be directional, facing Antennas must be directional, facing each other, and either tall enough or each other, and either tall enough or close enough together not to be close enough together not to be affected by the curvature of the affected by the curvature of the earth. earth.

3535

BandsBands The section of the electromagnetic The section of the electromagnetic

spectrum defined as radio waves and spectrum defined as radio waves and microwaves is divided into eight microwaves is divided into eight ranges, called bands, each regulated ranges, called bands, each regulated by government authorities. by government authorities.

These bands are rated from very low These bands are rated from very low frequency (VLF) to extremely high frequency (VLF) to extremely high frequency (EHF). frequency (EHF).

3636

3737

BandsBands

3838

Wireless Transmission Wireless Transmission WavesWaves

Radio WavesRadio Waves Radio waves are electromagnetic waves Radio waves are electromagnetic waves

ranging in frequencies between 3 KHz and ranging in frequencies between 3 KHz and 1 GHz and those between 1 GHz and 300 1 GHz and those between 1 GHz and 300 GHz are called Microwaves.GHz are called Microwaves.

Radio wavesRadio waves Are Omnidirectional; Propagate to long Are Omnidirectional; Propagate to long

distancesdistances Can penetrate walls so we cannot Can penetrate walls so we cannot

isolate a communication to just inside or isolate a communication to just inside or outside a building. outside a building.

3939

Radio WavesRadio Waves

4040

• Radio waves are used for multicast communications, such as radio and television, and paging systems.

• They can penetrate through walls.• Highly regulated. • Use omnidirectional antennas

Omnidirectional AntennaOmnidirectional Antenna

7.7.4141

MicrowavesMicrowaves

4242

• Microwaves are used for unicast communication such as cellular telephones, satellite networks,and wireless LANs.

• Higher frequency ranges cannot penetrate walls.

• Use unidirectional antennas - point to point line of sight communications.

Unidirectional AntennasUnidirectional Antennas

InfraredInfrared Infrared are electromagnetic waves ranging in Infrared are electromagnetic waves ranging in

frequencies between 300 GHz and 400 THzfrequencies between 300 GHz and 400 THz

4444

Infrared signals can be used for short-range communication in a closed area

using line-of-sight propagation.

SummarySummary Guided MediaGuided Media

Twisted-Pair CableTwisted-Pair Cable Coaxial CableCoaxial Cable Fiber-Optic Cable Fiber-Optic Cable

Unguided MediaUnguided Media Radio WavesRadio Waves MicrowavesMicrowaves InfraredInfrared

4545