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Tuesday, August 6, 2013

PPT On Classification of Communication System


Classification of Communication System Presentation Transcript:
1.Classification of Communication System
Communication systems are classified based on the type of signals sent on channel.

2.Modulation and Digitization

3. Advantages

4.Analog Baseband System
Analog:   m(t) can assume any value in a continuous range of values at any point in time t.
Baseband:  m(t) has a frequency-domain spectrum clustered around zero frequency (the base).

5.Analog Baseband Systems
An analog baseband systems sends the analog baseband signal m(t) as is (without any modifications).
- Simplest possible system
- Inexpensive to build
Usually used for short distance communication.

6.Example: Analog Baseband Systems

7.Modulation and Digitization

In modulation, signal m(t) is combined with high frequency signals called the carrier.
Hence, frequencies are shifted.

9.Analog and Digital Carrier System
Modulation (Analog and digital carrier systems) advantages:
Allow the use of reasonable antenna length.
Allow multiplexing  (FDM) as well as CDMA and OFDMA in digital systems.

10.Example Carrier System
Analog carrier system:
AM and FM radio broadcasting
Analog TV broadcasting.
Digital broadcasting:
Digital radio broadcasting
Digital TV broadcasting
WiMAX metropolitan area network
Wi-Fi wireless local area network
Cellular telephony.
ADSL modems

11.Modulation and Digitization

To convert the analog baseband signal into a digital baseband signal:
Encoding (coding)
Pulse Shaping

13.Digital baseband Advantages
Immunity to Noise
Allows Multiplexing at baseband level
More bandwidth efficient (compression and line coding).

14.Source and Destination

15.Bandwidth & Rate of Transmission
Bandwidth:  Range of frequencies that it can transmit with reasonable fidelity.
Rate of information transmission is directly proportional to bandwidth B.

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