Ch 7. Transmission Media

klapdorothypondMobile - Wireless

Nov 23, 2013 (3 years and 6 months ago)

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Ch 7. Transmission Media

Transmission Media (1)


Broad definition


Anything that can carry information


In data communication:


Free space, metallic cable, fiber
-
optic cable

Transmission Media (2)


History


19
th

century


telegraph by Morse


1869


telephone by Bell


1895


wireless communication by Hertz


Modern communication media


twisted
-
pair,
coaxial cable, and optical fiber


Classification


Telegraph

http://www.youtube.com/watch?v=Lki3jxNL
VCI

Twisted
-
pair Cable


Two metal conductors: one for signal, the other for ref
erence (ground)


Twisted for the equal amount of exposure of each li
ne to the noise





Unshielded twisted
-
pair (UTP) vs. shielded twisted
-
pair
(STP)

Categories of UTP cables

UTP Performance

Coaxial Cable


Carry signals of a
higher frequency
than
UTP


Central core conductor and outer conductor

Categories of coaxial
cables

Coaxial Cable Performance

UTP vs. Coaxial

Coaxial cables

UTP

Fiber
-
Optical Cable


Bending of light ray






Guide light ray

Optical Fiber Performance


Better performance than Coaxial and UTP (1/10)









Provide cost
-
effective solution for data transfer


Using WDM, at a rate of 1600
Gbps

7.2 Unguided Media: Wireless


Transport electro
-
magnetic waves without
using a physical conductor


Propagation methods

Wireless Transmissions


Radio waves (3K ~ 1GHz)


Long
-
distance, low rate communication


Radio, TV, paging


Microwaves (1G ~ 300GHz)


Short
-
distance, high rate communication


Cellular, satellite, wireless LANs


Infrared waves (300G ~ 400THz)


Very short range communication


Line
-
of
-
sight is required


In
-
door communication (e.g. remote controller)

Antennas


Omni
-
directional

(directionless)



Uni
-
directional