1. Transmission Media
Dr. Atiqur Rahman
ড. আতিক
ু র রহমান
PhD(CQUPT, China), MS.Engg.(CU), B.Sc.(CU)
Associate Professor
Department of Computer Science and Engineering
University of Chittagong
2. Unguided Media
• Unguided medium
transport waves without
using a physical
conductor
• Often referred to
wireless communication
• Signals are normally
broadcast through free
space and thus are
available to anyone who
has a device capable of
receiving them
5. Wireless Propagation
• Signal travels along three routes
-Ground wave
Follows contour of earth
Up to 2MHz
AM radio
-Sky wave
Amateur radio, BBC world service, Voice of America
Signal reflected from ionosphere layer of upper atmosphere
-Line of sight
Above 30Mhz
May be further than optical line of sight due to refraction
11. Radio Waves
• Electromagnetic waves
ranging in frequencies
between 3 kHz and 1
GHz are normally called
radio waves
• Electromagnetic waves
ranging in frequencies
between 1 and 300 GHz
are called microwaves
15. Microwaves
• Electromagnetic waves
having frequencies
between 1 and 300 GHz
are called microwaves
• Microwaves are
unidirectional
• When an antenna
transmits microwaves,
they can be narrowly
focused
20. Satellite Microwave
• Satellite is relay station
• Satellite receives on one frequency, amplifies or repeats signal and transmits
on another frequency
• Requires geo-stationary orbit
-Height of 35,784km
• Television
• Long distance telephone
• Private business networks
28. Infrared
• Infrared waves, with
frequencies from 300
GHz to 400 THz
(wavelengths from 1 mm
to 770 nm), can be used
for short-range
communication
• Infrared waves, having
high frequencies, cannot
penetrate walls
• Prevents interference
between one system and
another