1. Computer Networks
Bhushan Trivedi, Director, MCA Programme, at the GLS Institute of Computer Technology, Ahmadabad

2. Data Communication Fundamentals
Chapter 3
Data Communication Fundamentals

3. The prerequisites to communication
Bandwidth and Data Rate
The frequency and the band
The media effect on the bandwidth of signal
The composite signals and Fourier components
Filters

4. Other factors affecting the data rate
Analog or digital signaling.
 Analog
Type of modulation
Amount of constellation points
Digital
number of levels

5. Other factors affecting the data rate
Sensitivity of the receiver
Resistance of the media and thus its temperature
How the wires are structured and shielded

6. Harmonics and composite wave

7. Properties of a channel
More the bandwidth of the media, more the number of harmonics that can pass through the media.
Higher the data rate, less will be the number of harmonics that can pass through the media.
MDR of a channel = 2 × Bandwidth × log2 (signal levels)
MDR of a channel = Bandwidth × log2 (1 + S/N)

8. Signal to noise ratio S/N =10 log (Ps/Pn) When Ps/Pn becomes 1
MDR = Bandwidth × log2 (1+10 × log e 1)
= Bandwidth × log 2 (1+0)
= Bandwidth × log 2 1
= 0 (as log21 = 0)

9. Filtering a specific frequency

10. Differentiating Analog and Digital
Analog and Digital Signaling
Analog Signaling
Digital signaling
Difference between Analog and Digital Signaling
Analog and Digital Transmission
Introduction to Transmission
Analog Transmission
Digital transmission
Digital signaling and errors

11. Digital and analog wave

12. Periodic waves, digital and analog

13. A periodic wave

14. Digital signaling and bit rate
If we use 2n different voltage signals, then
bit rate = baud rate × n
If we use n voltage signals, then
bit rate = baud rate × log2 n

15. Characteristics of Digital Signaling
Square waveforms
Limited discrete values of voltage levels
Need more bandwidth
Noise can be completely removed

16. Repeater reshapes, amplifier amplifies

17. Noise addition to waves

18. Signaling is different than transmission
Analog and digital transmission 
We can use digital signaling irrespective of whether the transmitted data is analog (voice or video) or digital (zeros and ones)
Similarly, analog signaling can be used for both analog and digital transmission
Coding mechanisms

19. Modulation Amplitude modulation Frequency modulation Phase Modulation
Modulation in Practice
Modulation in cable TV
Modulation in ADSL

20. Amplitude modulation

21. Amplitude modulation

22. A square wave to represent bits

23. A distorted square signal

24. Frequency modulation

25. Phase

26. Phase change to indicate bit

27. Constellation pattern for QPSK

28. QAM-16 constellation pattern

29. Frequency bands used in cable TV transmission

30. Multiplexing Multiplexing and de-multiplexing
Time Division Multiplexing
Frequency division multiplexing

31. Switching

32. Routing

33. Transmission Errors
Attenuation
Distortion
Noise