CHAPTER Communication Direction, Bandwidth and Channels

Frequency Spectrum and Bandwidth 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

Direction of Communication MODULE Direction of Communication

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

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The Concepts of Channels in Communication 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 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 3 TV 1 TV 2 Tuned to Channel 77 at Frequency f77 Tuned to Channel 33 at Frequency f33 Tuned to Channel 65 at Frequency f65

An Example of Multiple Channel Communication in Space At freq.. F4 TV1 Regular TV Transmission TV2 Channel 11 At freq.. F11 Transmission Towers

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Baseband and Broadband Transmission 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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MODULE Frequency Spectrum

Frequency Spectrum Spectrum of frequencies available for communication Ranges from voice to high speed optical communication

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