1. Lecture 7
Overview of Analog and Digital Technologies

2. Overview of Analog Technology

3. AREAS OF APPLICATION
• Old telephone networks
• Most television broadcasting at present
• Radio broadcasting

4. ANALOG SIGNALS: THE BASICS
Cycle
Time
Signal
Amplitude
Frequency =
Cycles/Second
A typical
sine wave

5. AMPLITUDE AND CYCLE
• Amplitude
• Distance above reference line
• Cycle
• One complete wave

6. FREQUENCY
• Frequency
• Cycles per second
• Hertz is the unit used for expressing frequency
• Frequency spectrum
• Defines the bandwidth for different analog
communication technologies

7. INFORMATION REPRESENTATION USING ANALOG
SIGNALS
• Information can be represented using analog signals
• Analog signals cannot be manipulated easily
• Analog signals must be digitized for computer processing
• They must also be presented in binary form for
computer processing

8. ANALOG TO DIGITAL CONVERSION
1 0 1 1 0 1 0 0
A to D Converters, Digital
Signal Processors (DSP) etc.

9. DATA TRANSMISSION USING ANALOG
TECHNOLOGY
Digital
0s and 1s
Analog
0s and 1s
Digital-to-Analog Modulation
and vice versa
Computer Modem

10. VOICE TRANSMISSION EXAMPLE
Voice
Carrier Wave
AM Radio Transmission
Analog-to-Analog Modulation

11. Frequency Spectrum
and Bandwidth

12. FREQUENCY SPECTRUM DEFINED
• Available range of frequencies for communication
• Starts from low frequency communication such as voice
and progresses to high frequency communication such
as satellite communication
• The spectrum spans the entire bandwidth of
communicable frequencies

13. FREQUENCY SPECTRUM
Low Frequency High Frequency
Radio
Frequency
Coaxial
Cable
MHz
Satellite
Transmission
Microwave
MHz
Voice
KHz

14. FREQUENCY SPECTRUM
• Low-end
• Voice band
• Middle
• Radio wave
• High-end
• Satellite communication

15. BANDWIDTH DEFINITION
• Bandwidth, in general, represents a range of
frequencies
300 MHz 700 MHz
Bandwidth is 400 MHz

16. USAGE OF THE TERM BANDWIDTH
• To specify the communication capacity
• A medium such as a coaxial cable is associated with
a bandwidth
• To indicate the bandwidth of a technology
• Voice grade circuits have a bandwidth of 4 KHz (0-
4000 Hz)

17. DIGITIZATION CONSIDERATION
• Sample at twice the rate of bandwidth for acceptable
quality digitization of voice
• Sampling rate for voice transmission is there 8000 Hz
• If each sample is represented by 8-bits, the bandwidth
required for transmission is 64000 bps – Approximately
64K bps

18. COMMUNICATION CAPACITY
• Bandwidth is indicative of the communication capacity
• Communication speed is proportional to bandwidth
• Shannon's law
• Units used to represent bandwidth are Hz, bps etc.

19. COAXIAL CABLE EXAMPLE
• Bandwidth of 300 MHz
• Comparison with twisted pair
• Higher bandwidth
• Supports faster communication speeds

20. LIMITING FACTORS ON COMMUNICATION SPEED
Communicatio
n SpeedBandwidth Technology

21. IMPACT OF BANDWIDTH AND TECHNOLOGY ON
COMMUNICATION SPEED
• Bandwidth limitation
• Use better technology such as data compression
used in modems to increase speed of communication
• Bandwidth and technology limitation
• Move to higher bandwidth media such as fiber cables

22. SPEED DEPENDENCY ON BANDWIDTH AND
TECHNOLOGY
Medium 1
Technology Medium 2
Higher Bandwidth
Medium 1 example can be shielded twisted
pair and medium 2 example can be fiber.

23. IMPLICATION
• Whenever a new technology with higher communication
speed is introduced, it is first introduced on a medium of
higher bandwidth
• Example: Optical fiber
• It is then moved to a widely used medium with further
advancement of the technology
• Example: Copper wire

24. An Overview of Digital Technology

25. AREAS OF APPLICATION
• Computers
• New telephone networks
• Phased introduction of digital television technology

26. DIGITAL TECHNOLOGY
• Basics
• Digital signals that could be assigned digital values
• Digital computer technology
• Digital signals
• Binary representation
• Encoded into ones and zeros

27. DIGITAL ADVANTAGE
• Processing using computer technology
• Programmable services
• Better quality due to being able to reconstruct exact
digital patterns at the receiving end
• Faster communication speeds are possible

28. DIGITAL SIGNAL
1 0 1 1 0 1 0 0
Pulse
Time
SignalStrength
Pulse Duration

29. DIGITAL TERMS
• Pulse
• Pulse duration
• Pulse amplitude
• Signal strength

30. CLOCK SPEED AND PULSE DURATION
Pulse
Duration
MHz

31. CLOCK SPEED AND EXECUTION SPEED
• Pulse duration is inversely proportional to the clock
frequency
• Faster the clock speed, the smaller the pulse duration
• Smaller the pulse duration, the faster the execution in
general

32. CLOCK SPEED AND COMMUNICATION SPEED
• Faster the clock speed, smaller the pulse duration
• Smaller the pulse duration, smaller the time taken to
transmit one bit of information
• Therefore, faster the clock speed measured in MHz,
faster the communication speed measured in Mbps in
general

33. CLOCK SPEED AND COMPUTER
OPERATION
• Computer operations are timed by a clock, namely by the
clock speed measured in HZ
• Faster the speed, the smaller the pulse duration
• Computer operations are timed by the pulse duration
• Therefore, faster the clock speed, faster the computer
operation
• A 3 GHz computer is faster than a 2 GHz computer

34. Digital-to-Analog and
Analog-to-Digital Conversion

35. THE NEED FOR CONVERSION
• Analog-to-Digital Conversation
• Connection of a computer to an analog
communication line
• Digital-to-Digital Interface
• Connection of a computer to a digital ISDN line
• Connection of different networks using a router

36. DIGITAL-TO-DIGITAL INTERFACE
Comp.
Sys. 1
Comp.
Sys. 2
DSL
Router
DSL
Router
Digital
IEEE 802.3
Digital
IEEE 802.3
Digital
Internet

37. DATA AND SIGNALS
• Usually use digital signals for digital data and analog signals for analog
data
• Can use analog signal to carry digital data
• Modem
• Sender  Modulation
• Receiver  Demodulation
• Can use digital signal to carry analog data
• CODEC
• Sender  Coding
• Receiver  Decoding

38. ANALOG SIGNALS CARRYING ANALOG
AND DIGITAL DATA

39. DIGITAL SIGNALS CARRYING ANALOG
AND DIGITAL DATA