Learning Objectives:

• Understand the fundamentals of digital communication systems and their importance in modern telecommunications.

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Why Digital communication is preferred over analog communication?

• It is difficult to distinguish the noise from the analog signal
• It is easy to distinguish the noise from a digital signal. Digital receiver only need to make a threshold decision (‘0’ or ‘1’?)
• No loss of signal quality:
• Complete clean-up and regeneration is possible
• Advanced processing is possible, such as:
  • Channel coding
  • Source coding
  • Encryption
  • Multiplexing different users (TDMA, CDMA…)
  • Multiplexing data from different sources (voice, video, data, medical…)
  • Lossless storing and retrieval

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Solved Example: 9164-01

The bit rate of the digital communication system is M kbps. The modulation used is 16 QAM. The minimum bandwidth required for ideal transmission is:

A. M/2 kHz

B. M/16 kHz

C. M kHz

D. M/8 kHz

Correct Answer: A

Solved Example: 9164-02

In digital transmission, the modulation technique that requires the minimum bandwidth is:

A. PCM

B. PAM

C. DPCM

D. Delta modulation

Correct Answer: D