comsats pcs previous lecture...twisted pair cable • it consists of two insulated copper wires...

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Principles of Communication Systems (PCS)

EEE 351

Lecture # 16 & 17

Transmission Channels/Media

Muhammad TilalDepartment of Electrical Engineering

CIIT Attock Campus

COMSATS Fall 2014 (Rev. 1.0)

The theme of this presentation is an inspiration from the one used in S2 Department of Chalmers University of Technology, Gothenburg, Sweden.

The COMSATS logo and “COMSATS” is the property of CIIT, Pakistan and subject to the copyrights and ownership of COMSATS.

Duplication & distribution of this work for Non Academic or Commercial use without prior permission is prohibited.

Previous Lecture

• Radio Transmitter

– Basic Building Blocks

• Antenna

• Radio Receivers

– Homodyne and Heterodyne Receivers.

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Session Overview


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Topic Transmission Media/ Channels

Concepts

Types of Transmission Channels, Types of Wired

Transmission Channels, Twisted Pair, Coaxial Cable, Optical

Fiber.

Recommended

Reading

Keywords Wired, Wireless, Twisted Pair, Coaxial Cable, Optical Fiber .

Transmission Channel

• Transmission medium or channel

is the path through which the

data/information is sent from

transmitter to receiver.

• The information transmitted by

the transmitter is in the form of

electromagnetic waves.

• These electromagnetic waves

travel through a path to reach the

receiver.


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• Communication channel might alsoinclude some electroniccomponents such as repeaters etc.

• Transmission channels are usuallymodeled as filter because the filtercan describe the frequencyresponse of channel in a betterway.

• Channel parameters can be

– Deterministic.

– Random.

– Time Variable.

– Linear/ Non- linear.

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Selection of Transmission Channel

• A lot of factors are considered

while selecting a transmission

channels.

• These factors include

– Amount of Traffic.

– Cost.

– Interference Levels.

– Mechanical Robustness.

– Point to point OR Networking.

– Power Transfer Capability.


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• These factors are not equallyimportant in a particular scenario.

• Certain systems might focus on theAmount of Traffic and Speed with alittle attention given to the cost.

• But a good transmission systemstakes into account most of thefactors to attain maximum goals.

Types of Transmission Channels

Transmission Channels/ Media

Guided

(Wired)

Media

Twisted Pair Cable

Coaxial CableOptical Fiber

Cable

Unguided

(Wireless)

Media

Radio Microwave Satellite


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Guided/Wired Transmission Channels

• A wired or guided medium is theone having physical existence. Aboundary/physical barrierconfines the transmitted signal init.

• Typical guided media include thecopper wire at basic level.

• Three fundamental guided mediainclude

– Twisted Pair Cable.

– Co-axial Cable.

– Optical Fiber Cable.


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• Each of these guided media hasits own properties such astransmission speed, effect ofnoise, physical appearance andcost.

Twisted Pair Cable

• It consists of two insulated

copper wires arranged in a

regular spiral pattern to minimize

the interference between

adjacent pairs.

• Used for voice and data

communications. Typical

applications include telephone

and Local Area Network (LAN).


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• Frequency Range is 0.4 to 2000MHz.

• Amplifier required after every 5-6Km for analog transmission whilerepeater required after every 2-3Km.

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Twisted Pair Cable

(Interference Reduction)


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Parallel Conductors

Twisted Pair Cable

Twisted Pair Cable (Pros and Cons)

Pros

• Cheap and easily available.

• Flexible and lightweight.

• Easy handling and installation.

Cons

• Low Bandwidth.

• Repeaters/amplifiers requiredafter short distances.


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STP and UTP

• Shielded Twisted Pair

The twisted pair is wrapped with

a metallic foil in order to reduce

electromagnetic interference.


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• Unshielded Twisted Pair

The twisted pair is insulatedindividually only and is encased inan outer coating without anymetallic foil.

Coaxial Cable

• It consists of an inner solid

conductor surrounded by a

braided outer conductor.

• Both conductors are separated by

a solid insulating material.


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• Both conductors have a commoncentral axis which gives it thename ‘Coaxial Cable’.

• Important aspects: BetterShielding, Easy tapping, Lessinterference than twisted pair,not suitable for long distances.

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Optical Fiber Cable

• Optical fiber is a very thin

plastic/glass cable capable of

conducting optical rays.

• Usually small fibers are bundled

together to make a large Optical

Fiber cable.


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• Optical fiber require theelectrical/optical interface, bothfor transmission and reception.

Optical Fiber Cable

Pros

• Greater capacity (BW: Gbps)

• Small sized and Light weight

• Lower attenuation

• Better Immunity toenvironmental interference

• Highly secure due to tap difficultyand lack of signal radiation

Cons

• Expensive for short distancetransmissions

• Highly skilled installers requiredfor installation.

• Addition of more nodes isdifficult.


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Wireless Transmission Media

• Wireless or unguided media andtransmission channels are theones which transmit or receivethe information over the air.

• The transmitter transmitsinformation which travelsthrough air and reaches thereceiver.

• There are no physical boundariesof wireless media/channels asopposed to the wired media.

• Susceptible to rain, atmosphericvariations, objects in thetransmission paths and noise.

• Advantages are

– Mobility.

– Accessibility to difficult terrain.

– Reduction in cable laying andequipment cost.

– Reduction in Right of the Waycosts.


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Wireless Transmission Media

• Indoor

– 10 - 50 Meters.

– Infrared, Bluetooth & WLAN.

• Short Range Outdoor

– 50 – 200 Meters.

– WLAN

• Mid Range Outdoor

– 200m – 5 Km

– GSM, CDMA, WiMax, WLANPoint to Point.

• Long Range Outdoor

– 5Km – 100Km.

– Microwave Point to Point.

• Long Distance Communications

– Intercontinental.

– Satellites.


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Frequency Bands (Wireless Media)


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Band Range Propagation Application

VLF 3–30 KHz Ground Long-range radio navigation

LF 30–300 KHz GroundRadio beacons and

navigational locators

MF 300 KHz–3 MHz Sky AM radio

HF 3–30 MHz SkyCitizens band (CB),

ship/aircraft communication

VHF 30–300 MHzSky and

line-of-sight

VHF TV,

FM radio

UHF 300 MHz–3 GHz Line-of-sightUHF TV, cellular phones,

paging, satellite

SHF 3–30 GHz Line-of-sight Satellite communication

EHF 30–300 GHz Line-of-sight Long-range radio navigation

Infrared Communications


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http://www.engineersgarage.com/sites/default/files/imagecache/Original/wysiwyg_imageupload/1/Infrared%20Communication.gif

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Bluetooth


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http:// http://www.itsans.com/sans/images/Bluetooth%20communication.jpg

Wireless Local Area Network (WLAN)


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InternetRouter

Switch

Access Point

Access Point

PC

PC

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Microwave Communications


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http://wwwen.zte.com.cn/endata/magazine/ztetechnologies/2012/no5/articles/201209/W020120912579203543218.jpg

Satellite Communications


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Next Lecture

• Channel Modeling


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References


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comsats pcs previous lecture...twisted pair cable • it consists of two insulated copper wires...

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