CHAPTER Communication Direction, Bandwidth and Channels

1. CHAPTERCommunication Direction, Bandwidth and Channels

2. Chapter Frequency Spectrum and Bandwidth

3. 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

4. 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

5. Chapter Modules • Direction of communication • Communication channels • Baseband and broadband channels

6. MODULE Direction of Communication

7. Direction Of Flow Simplex A B Half-duplex Full-duplex

8. 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

9. END OF MODULE

10. MODULE The Concepts of Channels in Communication

11. A Definition of a Communication Medium • One that allows the propagation of information carried by either electromagnetic or optical signals

12. 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

13. Presence of Multiple Channels in a Physical Media Guard Band Channel 1 Frequency F1 Channel 2 Frequency F2 One physical medium (Coaxial cable).

14. 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

15. 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.

16. 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

17. 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

18. An Example of Multiple Channel Communication in Space Channel 4 At freq.. F4 TV1 Regular TV Transmission TV2 Channel 11 At freq.. F11 Transmission Towers

19. END OF MODULE

20. MODULE Baseband and Broadband Transmission

21. 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

22. 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

23. END OF MODULE

24. MODULE Frequency Spectrum

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

26. END OF MODULE

27. END OF CHAPTER