DIGITAL COMMUNICATION INTRODUCTION AND DETAILS ABOUT ANALOG AND DIGITAL COMMUNICATION

1. EC8501/DIGITAL COMMUNICATION
ROEVER ENGINEERING COLLEGE
ELAMBALUR, PERAMBALUR- 621 220
DEPARTMENTOFELECTRONICSANDCMMUNICATIONENGINEERING
Presented by
Mr.T.Azhagesvaran, AP (Sr.G)/ECE
Roever Engineering College
Perambalur

2. Communication Systems
.
EC 8501-DIGITAL COMMUNICATION
1. S. Haykin, “Digital Communications”, John Wiley, 2005
Communication Systems
⚫ Basic components:
⚫ Transmitter
⚫ Channel or medium
⚫ Receiver
⚫ Noise degrades or interferes with transmitted information.

3. Communication Systems
Communication Systems
Ageneral model of all communication systems.

4. Communication Systems
Communication Systems
Transmitter
⚫The transmitter is a collection of electronic components
and circuits that converts the electrical signal into a signal
suitable for transmission over a given medium.
⚫Transmitters are made up of oscillators, amplifiers, tuned
circuits and filters, modulators, frequency mixers, frequency
synthesizers, and other circuits.

5. Communication Systems
Communication Systems
Communication Channel
⚫The communication channel is the medium by which the
electronic signal is sent from one place to another.
⚫Types of media include
⚫ Electrical conductors
⚫ Optical media
⚫ Free space
⚫ System-specific media (e.g., water is the medium for sonar).

6. Communication Systems
Communication Systems
Receivers
⚫A receiver is a collection of electronic components and
circuits that accepts the transmitted message from the channel
and converts it back into a form understandable by humans.
⚫Receivers contain amplifiers, oscillators, mixers, tuned
circuits and filters, and a demodulator or detector that
recovers the original intelligence signal from the modulated
carrier.

7. Communication Systems
Communication Systems
Transceivers
⚫A transceiver is an electronic unit that incorporates
circuits that both send and receive signals.
⚫Examples are:
• Telephones
• Fax machines
• Cell phones
• Computer modems

8. Communication Systems
Communication Systems
Attenuation
⚫ Signal attenuation, or degradation, exists in all media of wireless
transmission. It is proportional to the square of the distance between the
transmitter and receiver.
Noise
⚫ Noise is random, undesirable electronic energy that enters the
communication system via the communicating medium and interferes
with the transmitted message.

9. Types of Electronic Communication
1. SIMPLEX
2. HALF-DUPLEX
3. FULL-DUPLEX
⚫ The simplest method of electronic communication is referred to as simplex.
⚫ This type of communication is one-way. Examples are:
⚫ Radio
⚫ TV broadcasting
⚫ Beeper (personal receiver)
1)Simplex Communication

10. Types of Electronic Communication
⚫ The form of two-way communication in which only one party transmits at a
time is known as half duplex. Examples are:
⚫ Police, military, etc. radio transmissions
⚫ Citizen band (CB)
⚫ Family radio
⚫ Amateur radio
2) Half Duplex Communication

11. Types of Electronic Communication
⚫ Most electronic communication is two-way and is referred to as
duplex.
⚫ When people can talk and listen simultaneously, it is called full duplex.
The telephone isan exampleof this typeof communication.
3) Full Duplex Communication

12. Basic Blocks of Digital Communication System
Information
Source
A / D
Converter
Source
Encoder
Channel
Encoder
Modulator
Information
Sink
D / A
Converter
Source
Decoder
Channel
Decoder
Demodulator
Channel

13. Basic Blocks of Digital Communication System
⚫ Information source
⚫ Analog Data: Microphone, speech signal, image, video etc…
⚫ Discrete (Digital) Data: keyboard, binary numbers, hex numbers, etc…
⚫ Analog to Digital Converter (A/D)
⚫ Sampling:
⚫ Converting continuous time signal to a digital signal
⚫ Quantization:
⚫ Converting the amplitude of the analog signal to a digital value
⚫ Coding:
⚫ Assigning a binary code to each finite amplitude in the analog signal

14. Basic Blocks of Digital Communication System
⚫ Source encoder
⚫ Represent the transmitted data more efficiently and remove redundant
information
Two types of encoding:
⚫ Lossless data compression (encoding)
⚫ Data can be recovered without any missing information
⚫ Lossy data compression (encoding)
⚫ Smaller size of data
⚫ Data removed in encoding can not be recovered again

15. Basic Blocks of Digital Communication System
⚫ Channel encoder:
⚫ To control the noise and to detect and correct the errors that can occur in
the transmitted data due the noise.
⚫ Modulator:
⚫ Represent the data in a form to make it compatible with the channel
⚫ Carrier signal “high frequency signal”
⚫ Demodulator:
⚫ Removes the carrier signal and reverse the process of the Modulator

16. Basic Blocks of Digital Communication System
⚫ Channel decoder:
⚫ Detects and corrects the errors in the signal gained from the channel
⚫ Source decoder:
⚫ Decompresses the data into it’s original format.
⚫ Digital toAnalog Converter:
⚫ Reverses the operation of theA/D
⚫ Needs techniques & knowledge quantization, and coding methods.
⚫ Information Sink
⚫ The User

17. Why shouldwe use digital communication?
⚫ Ease of regeneration
⚫ Pulses “ 0 , 1”
⚫ Easy to use repeaters
⚫ Noise immunity
⚫ Better noise handling when using repeaters that repeats the original
signal
⚫ Easy to differentiate between the values “either 0 or 1” High
Bandwidth
⚫ High BW
⚫ Ease of Transmission
⚫ Less errors Faster Better productivity

18. Why shouldwe use digital communication?
⚫ Ease of multiplexing
⚫ Transmitting several signals simultaneously
⚫ Use of modern technology
⚫ Less cost !
⚫ Ease of encryption
⚫ Security and privacy guarantee
⚫ Handles most of the encryption techniques

19. Types of Transmission
1)Baseband Transmission
⚫ Baseband information can be sent directly and unmodified over the
medium or can be used to modulate a carrier for transmission over
the medium.
⚫ In telephone or intercom systems, the voice is placed on
the wires and transmitted.
⚫ In some computer networks, the digital signals are applied
directly to coaxial or twisted-paircables for transmission.

20. Types of Transmission
2) Broadband Transmission
⚫ A carrier is a high frequency signal that is modulated by audio, video, or
data.
⚫ A radio-frequency (RF) wave is an electromagnetic signal that is able to
travel long distances through space.

21. Difference between Analog Communication and Digital Communication
S.No. ANALOG COMMUNICATION DIGITAL COMMUNICATION
01.
In analog communication analog signal is used for
information transmission.
In digital communication digital signal is used for
information transmission.
02.
Analog communication uses analog signal whose
amplitude varies continuously with time from 0 to
100.
Digital communication uses digital signal whose
amplitude is of two levels either Low i.e., 0 or either
High i.e., 1.
03.
It gets affected by noise highly during
transmission through communication channel.
It gets affected by noise less during transmission
through communication channel.
04.
In analog communication only limited number of
channels can be broadcasted simultaneously.
It can broadcast large number of channels
simultaneously.
05.
In analog communication error Probability is
high.
In digital communication error Probability is low.
06. In analog communication noise immunity is poor. In digital communication noise immunity is good.

22. Difference between Analog Communication and Digital Communication
07. In analog communication coding is not possible.
In digital communication coding is possible. Different
coding techniques can be used to detect and correct
errors.
08.
Separating out noise and signal in analog
communication is not possible.
Separating out noise and signal in digital
communication is possible.
09.
Analog communication system is having complex
hardware and less flexible.
Digital communication system is having less complex
hardware and more flexible.
10.
In analog communication for multiplexing Frequency
Division Multiplexing (FDM) is used.
In Digital communication for multiplexing Time
Division Multiplexing (TDM) is used.
11. Analog communication system is low cost. Digital communication system is high cost.

23. Difference between Analog Communication and Digital Communication
12. It requires low bandwidth. It requires high bandwidth.
13. Power consumption is high. Power consumption is low.
14. It is less portable. Portability is high.
15.
No privacy or privacy is low, so it is not highly
secured.
Privacy is high, so it is highly secured.
16. Not assures an accurate data transmission. It assures a more accurate data transmission.
17. Synchronization problem is hard. Synchronization problem is easier.

24. UNIT-I- INFORMATION THEORY
Discrete Memoryless source, Information, Entropy,
Information - Discrete Memoryless channels –
Mutual
Binary
Symmetric Channel, Channel Capacity - Hartley - Shannon law -
Source coding theorem - Shannon - Fano & Huffmancodes

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