1. DATA COMMUNICATION
Lecture-24

2. Recap of Lecture 23 MODEM Standards Bell Modems ITU-T Modems
Traditional Modems
56k Modems

3. Overview of Lecture 24 Cable Modems Electromagnetic Spectrum
Transmission Media and its Types
Guided Media
Twisted Pair
Coaxial Cable
Optical Fiber

4. Cable Modem Cable TV uses a coaxial cable
Bandwidth up to 750 MHz (cf. 4KHz telephone line)
Each band is 6MHz; Multiplexed by FDM

5. Cable Modem

6. Cable Modem Downloading Uploading
64-QAM: 6 MHz * 6 bits/baud = 36 Mbps maximum
Uploading
Uploading band uses lower frequency range: Noisy
QPSK: 6 MHz * 2 bits/baud = 12 Mbps maximum

7. Electromagnetic Energy
Signals are transmitted in the form of electromagnetic energy, which can travel through
Metal cables (voice-band frequency)
Air/space (radio frequency)
Fiber-optic cable (visible light)

8. Electromagnetic Spectrum

9. Classes of Transmission Media

10. Categories of Guided Media

11. Twisted-Pair Cable Two forms Unshielded twisted-pair (UTP)
Shielded twisted-pair (STP)

12. Frequency of Twisted-Pair Cable

13. Unshielded Twisted-Pair (UTP) Cable

14. Parallel Flat Wire

15. Noise Effect on Twisted-Pair

16. Advantage of UTP
Advantages of UTP are:
Cost
Ease of Use

17. UTP Cable

18. Categories of UTP Cable
Category 1
Category 2
Category 3
Category 4
Category 5

19. UTP Connectors

20. Summary Cable Modems Electromagnetic Spectrum
Transmission Media and its Types
Guided Media
Twisted Pair
Coaxial Cable
Optical Fiber

21. Suggested Reading
Section 6.6, 7.1, “Data Communications and Networking” 2nd Edition by Behrouz A. Forouzan