Transcript CHAPTER Frequency Spectrum and Bandwidth

CHAPTER
Communication Direction,
Bandwidth and Channels
Chapter
Frequency Spectrum and
Bandwidth
© N. Ganesan, Ph.D. , All rights reserved.
Chapter Objectives
• Explain the different types of directional
flows in signal propagation
• Define bandwidth and the use of the
terminology in communications
• Discuss communication channels and the
splitting of bandwidth to accommodate
multiple channels
• Describe baseband and broadband
transmission and present practical examples
in each case
Chapter Objectives (continued)
• Discuss communication channels and
the splitting of bandwidth to
accommodate multiple channels
• Describe baseband and broadband
transmission and present practical
examples in each case
Chapter Modules
• Direction of communication
• Communication channels
• Baseband and broadband channels
MODULE
Direction of Communication
© N. Ganesan, Ph.D. , All rights reserved.
Direction Of Flow
Simplex
A
B
Half-duplex
Full-duplex
Direction Of Flow Details
• Simplex
– One direction only
– Radio broadcast
• Half-duplex
– One direction at any one point in time
– CB radio
• Full duplex
– Both directions at the same time
– Telephone lines
END OF MODULE
MODULE
The Concepts of Channels in
Communication
© N. Ganesan, Ph.D. , All rights reserved.
A Definition of a Communication
Medium
• One that allows the propagation of
information carried by either
electromagnetic or optical signals
Types of Media
• Physical medium and the space or open
medium
• Physical medium
– Also know as the guided medium
– Coaxial cable, Optical fiber etc.
• Open Medium
– Denotes the space above the earth
– The term space is galactic in scope
• Multiple channels can be established in
each of these media for communication
Presence of Multiple Channels in
a Physical Media
Guard Band
Channel 1
Frequency F1
Channel 2
Frequency F2
One physical medium (Coaxial cable).
Channel Characteristics
• A sub-bandwidth is assigned for each
channel for communication
• Channel differentiation
– Each channel transmits using a different
frequency
– The transmission frequency chosen for a
channel is usually near the middle of the
assigned bandwidth for the channel
• Guard bands are present around each
channel to minimize interference
Low and High-speed Channels in
Medium
Guard Bands
5 Mhz
Channel 1
50 Mhz
10 Mhz
Channel 2
150 Mhz
5 Mhz
One cable with a bandwidth of 220 MHz.
Channel Characteristics of the
Example
• Channel speeds within a medium need
not be the same
• Channel 2 in the previous example is
faster than channel 1
– Channel 2 speed is Proportional to 150 Hz
– Channel 1 speed is Proportional 50 Hz
• Total bandwidth of the medium is
computed as follows:
– 5 + 150 + 10 +50+5 =220 MHz
An Example of Multiple Channels
in a Physical Medium
Cable TV (carries multiple channels)
TV 1
Tuned to
Channel 33 at
Frequency f33
TV 2
Tuned to
Channel 65 at
Frequency f65
TV 3
Tuned to
Channel 77 at
Frequency f77
An Example of Multiple Channel
Communication in Space
Channel 4
At freq.. F4
TV1
Regular TV
Transmission
TV2
Transmission
Towers
Channel 11
At freq.. F11
END OF MODULE
MODULE
Baseband and Broadband
Transmission
© N. Ganesan, Ph.D. , All rights reserved.
Baseband Transmission
• Single channel transmission
– The physical medium carries one and only
one channel
• A good example is the LAN
– Ethernet LAN for instance uses baseband
transmission
Broadband Transmission
• The presence of Multiple channels over
a single physical medium
• One physical line is shared by multiple
channels
• Cable TV
• Internet
– Due to packet switching, one is given the
impression of the presence of multiple
channels
– Virtual broadband communication
END OF MODULE
MODULE
Frequency Spectrum
© N. Ganesan, Ph.D. , All rights reserved.
Frequency Spectrum
• Spectrum of frequencies available for
communication
• Ranges from voice to high speed optical
communication
END OF MODULE
END OF CHAPTER