Ie 418 518 telecommunication concepts
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IE 418/518: Telecommunication Concepts. Lecture Notes #4 Transmission Media. Transmission Media - Overview. Transmission Medium Physical path between transmitter and receiver Guided Media Waves are guided along a solid medium Unguided Media

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IE 418/518: Telecommunication Concepts

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Ie 418 518 telecommunication concepts

IE 418/518:Telecommunication Concepts

Lecture Notes #4

Transmission Media


Transmission media overview

Transmission Media - Overview

  • Transmission Medium

    • Physical path between transmitter and receiver

  • Guided Media

    • Waves are guided along a solid medium

  • Unguided Media

    • Provides means of transmission but does not guide electromagnetic signals

    • Employ an antenna for transmission


Transmission media overview1

Transmission Media - Overview

  • Characteristics and quality determined by medium and signal

  • For guided

  • For unguided

  • Key concerns are


Design factors

Design Factors

  • Bandwidth

    • All other factors remaining constant, higher bandwidth gives higher data rate

  • Transmission impairments

    • Attenuation

  • Interference

  • Number of receivers

    • In guided media

    • More receivers (multi-point) introduce more attenuation


Electromagnetic spectrum

Electromagnetic Spectrum


Transmission characteristics

Transmission Characteristics

  • Guided Media


Transmission media

Transmission Media

  • Guided media

    • Twisted-pair

    • Coaxial Cable

    • Optical Fiber

  • Unguided media

    • Satellites

    • Terrestrial Microwave

    • Broadcast Radio


Guided transmission media

Guided Transmission Media

  • Transmission Capacity

    • Either in terms of

      • Bandwidth, or

      • Data Rate

    • Depends critically on

      • Distance

      • Type of medium

        • Point-to-point

        • Mutipoint


Twisted pair

Twisted Pair

  • Most common medium

  • Two insulated wires twisted together in a helical manner (like DNA)

  • Advantages

  • Disadvantages


Twisted pair1

Twisted Pair

  • Separately insulated

  • Often bundled into cables

  • Usually installed in buildings during construction


Twisted pair applications

Twisted Pair - Applications

  • Telephone network

    • Between house and local exchange

  • Within buildings

    • To private branch exchange (PBX)

  • For local area networks (LAN)

    • 10 Mbps or 100 Mbps


Twisted pair transmission characteristics

Twisted Pair - Transmission Characteristics

  • Analog

    • Amplifiers every 5 km to 6 km

  • Digital

    • Use either analog or digital signals

    • Repeater every 2 km or 3 km

  • Limited in

    • Distance

    • Bandwidth (1 MHz)

    • Data rate (100 Mbps)

  • Susceptible to interference and noise


Unshielded and shielded tp

Unshielded and Shielded TP

  • Unshielded Twisted Pair (UTP)

    • Ordinary telephone wire

    • Cheapest

    • Easiest to install

    • Suffers from external Electromagnetic (EM) interference

  • Shielded Twisted Pair (STP)

    • Metal braid or sheathing that reduces interference

    • More expensive

    • Harder to handle (thick, heavy)


Utp vs stp

UTP vs. STP


Utp categories

UTP Categories

  • Cat 3

    • Up to 16 MHz

    • Voice grade found in most offices

    • Twist length of 7.5 cm to 10 cm

  • Cat 4

    • Up to 20 MHz

  • Cat 5

    • Up to 100 MHz

    • Commonly pre-installed in new office buildings

    • Twist length 0.6 cm to 0.85 cm


Comparison of utp stp

Comparison of UTP & STP


Near end crosstalk next

http://www.cabletesting.com

Near End Crosstalk (NEXT)

  • Coupling of signal from one pair to another

  • The tighter the twist in the cable, the more effective the cancellation


Coaxial cable applications

Coaxial Cable Applications

  • Most versatile medium


Coaxial cable applications1

Coaxial Cable Applications

  • Television distribution

    • Cable TV

  • Long distance telephone transmission

    • Can carry 10,000 voice calls simultaneously

    • Being replaced by fiber optic

  • Short distance computer systems links

  • LANs


Coaxial cable transmission characteristics

Coaxial Cable - Transmission Characteristics

  • Analog

    • Amplifiers every few km

    • Closer if higher frequency

    • Up to 500 MHz

  • Digital

    • Repeater every 1 km

    • Closer for higher data rates


Optical fiber

Optical Fiber

  • Greater capacity

    • Data rates of hundreds of Gbps

  • Smaller size & weight

  • Lower attenuation

  • Electromagnetic isolation

  • Greater repeater spacing

    • 10s of km at least


Optical fiber1

Optical Fiber

  • System components:

    • Transmission medium - fiber optic cable

    • Light source - LED or laser diode

    • Detector - photodiode


Optical fiber applications

Optical Fiber - Applications

  • Telephone Network Applications

    • Long-haul, metropolitan, rural, and subscriber loop circuits

  • Local Area Networks

    • Optical fiber networks

    • Data rates from 100 Mbps to 1 Gbps

    • Support hundreds (or even thousands) of stations


Optical fiber transmission characteristics

Optical Fiber - Transmission Characteristics

  • Light Sources

    • Light Emitting Diode (LED)

      • Cheaper

      • Wider operating temp range

      • Last longer

    • Injection Laser Diode (ILD)

      • More efficient

      • Greater data rate

  • Wavelength Division Multiplexing


Attenuation in guided media

Attenuation in Guided Media


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