chapter communication direction, bandwidth and channels
TRANSCRIPT
CHAPTERCHAPTER
Communication Communication Direction, Bandwidth Direction, Bandwidth
and Channels and Channels
© N. Ganesan, Ph.D. , All rights reserved.
Chapter
Frequency Spectrum and Bandwidth
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
© N. Ganesan, Ph.D. , All rights reserved.
MODULE
Direction of Communication
Direction Of Flow
Simplex
Half-duplex
Full-duplex
A B
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 END OF MODULE
© N. Ganesan, Ph.D. , All rights reserved.
MODULE
The Concepts of Channels in Communication
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
Channel 1
Channel 2
One physical medium (Coaxial cable).
Frequency F1
Frequency F2
Guard Band
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
Channel 1
Channel 2
One cable with a bandwidth of 220 MHz.
50 Mhz
150 Mhz
5 Mhz
5 Mhz
10 Mhz
Guard Bands
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
TV 1 TV 2 TV 3
Cable TV (carries multiple channels)
Tuned toChannel 33 at Frequency f33
Tuned toChannel 65 at Frequency f65
Tuned toChannel 77 at Frequency f77
An Example of Multiple Channel Communication in
Space
TV1
TV2
Channel 4At freq.. F4
Channel 11At freq.. F11
Regular TVTransmission
TransmissionTowers
END OF MODULEEND OF MODULE
© N. Ganesan, Ph.D. , All rights reserved.
MODULE
Baseband and Broadband Transmission
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
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© N. Ganesan, Ph.D. , All rights reserved.
MODULE
Frequency Spectrum
Frequency Spectrum
• Spectrum of frequencies available for communication
• Ranges from voice to high speed optical communication
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END OF CHAPTER END OF CHAPTER