20561350 transmission media ppt final

8/4/2019 20561350 Transmission Media Ppt Final

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COMMUNICATION

Cruz. Leah

Gacias Rose Ann

Lim, Keer

Roque, Jeremias Jr

Velilla, Michael


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Figure 7.1 COMMUNICATION medium and physical layer


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DEFINITIONS OF COMMUNICATION MEDIA

The COMMUNICATION medium is the physical path by which amessage travels from sender to receiver.

A COMMUNICATION medium (plural COMMUNICATION media) is amaterial substance (solid, liquid, gas, or plasma) that

can propagateenergywaves. For example, the COMMUNICATIONmedium for sound received by the ears is usually air, but solids andliquids may also act as COMMUNICATION media for sound.

The term COMMUNICATION medium also refers to a technical device

that employs the material substance to transmit or guide waves. Thus,an optical fiber or a copper cable is a COMMUNICATION medium.
http://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Wave_propagationhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Wave_propagationhttp://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Solid


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TYPES OF COMMUNICATION MEDIA

COMMUNICATION media is divided into two: Wired orWireless

Wired Media is the most common and is further divided intothree different types of cabling: Coaxial, Twisted Pairs, andFiber Optic Cables

Wireless media, which is, in a sense, no media at all, is alsogaining popularity. Wireless transmissions use radio waves orinfrared light to transmit data.


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TYPES OF COMMUNICATION MEDIA

COMMUNICATION

MEDIA

Guided (Wired) Unguided (Wireless)

Copper Media Fiber Optics FixedPoint-Point

OmnidirectionalPoint-Multipoint

Coaxial

Twisted Wire


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COAXIAL CABLE



COAXIAL CABLE

Coaxial cables were the first cable types used incommunications technology. It consists of two conductors that

share a common axis

The components of a coaxial cable are as follows:

Center conductor Outer conductor Insulation layer Plastic encasement/jacket



COAXIAL CABLE

Types of Coaxial Cable

Thinnet is a light and flexible cabling medium that isinexpensive and easy to install. This is thinner and it can havemaximum segments length of 185 meters.

Thicknet is thicker and does not bend as readily as Thinnet,Thicknet cable is harder to work with. A thicker center core,however, means that Thicknet can carry more signals a longerdistance than Thinnet. The thicknet coaxial cable segments (while

joining the nodes of a network) can be up to 500 meters long.


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COMMUNICATION Media contd.

Advantages :-

Much less susceptible to interference than twistedpair

Co-axial cables can be used for a shared cablenetwork.

Coaxial cable can be used for broadbandCOMMUNICATION i.e. several channel can betransmitted simultaneously.

Offer higher bandwidths up to 400 MBPS.
http://../My%20Documents/Downloads/coax.doc


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COMMUNICATION Media contd.DISADVANTAGES :-

Expensive compared to twisted pair.Not compatible with twisted pair cables.



TWISTED PAIR CABLE



TWISTED PAIR CABLE

A basic twisted-pair cable consists of two strands of copperwire twisted together. This twisting reduces the sensitivity of

the cable to EMI. Twisted-pair cable is inexpensive to installand offers the lowest cost per foot of any cable type.

Two types of twisted-pair cable are used: shielded andunshielded.



SHIELDED TWISTED PAIR CABLE




Shielded twisted-pair cabling consists of one or more twistedpairs of cables enclosed in a foil wrap and woven copper

shielding.

shield further reduces the tendency of the cable to radiate EMIand thus reduces the cables sensitivity to outside

interference.





STP Characteristics

CostSTP cable costs more than thin coaxial or unshielded twisted-pair cable. STP is less costly, however, than thick coax orfiber-optic cable.





STP Characteristics

CapacityThe most common data rate for STP cable is 16 MbpsAttenuationAll varieties of twisted-pair cable have attenuationcharacteristics that limit the length of cable runs to a fewhundred meters, although a 100-meter limit is most common.

EMI CharacteristicsThe shield in STP cable results in good EMI characteristics for

copper cable.

UNSHIELDED TWISTED PAIR CABLE




The characteristics of the Unshielded Twisted Pair cables(UTP) are similar in many ways to STP, differing primarily in

attenuation and EMI. Several twisted-pairs can be bundledtogether in a single cable. These pairs typically are color codedto distinguish them.


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The Electronic Industries Association (EIA) hasdeveloped standards to grade UTP.

1. Category 1. The basic twisted-pair cablingused in telephone systems. This level ofquality is fine for voice but inadequate for dataCOMMUNICATION.

2. Category 2. This category is suitable for voiceand data COMMUNICATION of up to 2Mbps.

3. Category 3.This category is suitable for dataCOMMUNICATION of up to 10 Mbps. It is now

the standard cable for most telephonesystems.

4. Category 4. This category is suitable for dataCOMMUNICATION of up to 20 Mbps.

5. Category 5. This category is suitable for data


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Table 7.1 Categories of unshielded twisted-pair cables

Category Bandwidth Data Rate Digital/Analog Use

1 very low < 100 kbps Analog Telephone

2 < 2 MHz 2 Mbps Analog/digital T-1 lines

3 16 MHz 10 Mbps Digital LANs



6 (draft) 200 MHz 200 Mbps Digital LANs

7 (draft) 600 MHz 600 Mbps Digital LANs





UTP Characteristics

InstallationUTP cable is easy to install.CostUTP cable is the less costly, although properly installedCategory 5 tends to be fairly expensive.


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UTP Characteristics

EMI CharacteristicsBecause UTP cable lacks a shield, it is more sensitive to EMIthan coaxial or STP cables.


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COMMUNICATION Media

TWISTED PAIR CABLE

Advantages:-

It is simple and easy to install.

It is physically flexible. It has low weight.

It can be easily connected.

It is very inexpensive. Readily available


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COMMUNICATION Media contd.Disadvantage :-

Because of high attenuation, it is incapableof carrying a signal over long distances

without the use of repeaters.

Low bandwidth hence unsuitable forBroadband connection.

Susceptibility to interference and noise

.

FIBER OPTIC CABLE
http://../My%20Documents/Downloads/UTP.doc



FIBER-OPTIC CABLE

FIBER OPTIC CABLE



FIBER-OPTIC CABLE

Fiber-optic cable is the ideal cable for dataCOMMUNICATION because it accommodates extremely high

bandwidths, has no problems with EMI, supports durablecables and cable runs as long as several kilometers.Optical fiber cables dont transmit electrical signals. Instead,

the data signals must be converted into light signals.

The center conductor of a fiber-optic cable is a fiber that consists of

highly refined glass or plastic. The fiber is coated with a cladding

that reflects signals back into the fiber to reduce signal loss. A plastic

sheath protects the fiber.


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Figure 7.10 Fiber optics:Bending of light ray


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Figure 7.11 Optical fiber


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Fiber Optic Advantages

greater capacity (bandwidth of up to 2Gbps)

smaller size and lighter weight

lower attenuation immunity to environmental interference

highly secure due to tap difficulty and lack

of signal radiation


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Fiber Optic Disadvantages

expensive over short distance

requires highly skilled installers

adding additional nodes is difficult

UNGUIDED MEDIA


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UNGUIDED MEDIA

Unguided Media or Wireless Communication consists of ameans (e.g. air, space) for the data signals to travel, where

there is nothing to guide them along a specific path, like inwires. Unbounded media is electromagnetic waves in form ofradio, microwave, infrared or others.

Wireless communication is used where cables are difficult touse or install.

CLASSIFICATIONS OF WIRELESS COMMUNICATION


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Classification by Propagation Fixed (Directional)

Mobile (Omnidirectional)

Classification by Method Infrared Laser Radio waves Satellite Microwaves


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Wireless (Unguided Media)COMMUNICATION

COMMUNICATION andreception are achieved bymeans of an antenna

directional transmitting antenna puts out

focused beam

transmitter and receiver must bealigned

Omni directional signal spreads out in all directions

can be received by many antennas



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The infrared light transmits data through the air and can propagatethrough a room (bouncing of surfaces) but will not penetrate walls.

e.g

. TV remote, Wireless speakers etc.

Infrared light can be transmitted across relatively short distances

and can be either beamed between two points or broadcast from one

point to many receivers.



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Laser COMMUNICATION

Laser COMMUNICATION requires direct line of sight.

It is unidirectional like microwave, but has much higher speed than

microwaves

It is point-to-point COMMUNICATION, typically between

buildings.



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Radio Wave :- uses continuous sine waves to transmit information

(Audio, Video & Data). A radio setup has two parts :

Transmitter

Receiver

Both transmitter and receiver uses antennas to radiate and capture

the radio signal.

Radio frequencywaves often are used for data signaling. Radio

frequencies can be transmitted across electrical cables or by using

radio broadcast COMMUNICATION.

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


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Propagation of Radio Waves

Radio technology considers the earth as surroundedby two layers of atmosphere: the troposphere andthe ionosphere.

The troposphere is the portion of the atmosphereextending outward approximately 30 miles from theearth's surface.

The troposphere contains what we generally think of

as air. Clouds, wind, temperature variations, andweather in general occur in the troposphere.

The ionosphere is the layer of the atmosphere abovethe troposphere but below space.

Propagation methods


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Propagation methods


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Ground propagation. In ground propagation, radio waves travel

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

These low-frequency signals emanate in all directions from thetransmitting antenna and follow the curvature of the planet. Thedistance depends on the power in the signal.

In Sky propagation, higher-frequency radio waves radiate upwardinto the ionosphere where they are reflected back to earth. Thistype of COMMUNICATION allows for greater distances with lower

power output. Signal reflected from ionospherelayer of upper atmosphere

In Line-of-Sight Propagation, very high frequency signals aretransmitted in straight lines directly from antenna to antenna.

Above 30Mhz


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Line of Sight Propagation



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Satellite :- The satellite act as relay stationsfor communication signals. The satelliteaccept data/signal transmitted from an

earth station, amplify them and retransmitthem to another earth station. Areacovered is quite large.



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Microwave :

Microwave COMMUNICATION is line of sight

COMMUNICATION. ( A line of sight signal passes through theatmosphere, originates from a dish antenna, travels in straight linefree of material obstacles and received by another dish antenna.)

It consists of Transmitter, Receiver and Atmosphere.

With a 100m high tower, distances of 100 Km between towers arefeasible.

REASONS FOR WIRELESS TECHNOLOGY


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Spaces where cabling would be impossible orinconvenient.

People who move around a lot within their workenvironment.

Temporary installations.

People who travel outside of the work environment andneed instantaneous access to network resources.

Di d


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Disadvantages

Are subject to a lot more errors than guidedmedia channels.

Interference is one cause for errors, can becircumvented with high SNR.

The higher the SNR the less capacity isavailable for COMMUNICATION due to thebroadcast nature of the channel.

Channel also subject to fading and nocoverage holes.