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  1. Chapter Overview of Analog and Digital Technologies

  2. Chapter Objectives • Explain the basic concepts of analog and digital technology • Show the importance of frequency spectrum to communication along with an explanation of the concept of bandwidth • Give an overview of the interface technology between analog and digital technology • Describe the process of digitizing data, audio, image and video • Discuss quality retention in digital transmission

  3. Module Overview of Analog Technology

  4. Areas of Application • Old telephone networks • Most television broadcasting at present • Radio broadcasting

  5. Amplitude Cycle Analog Signals: The Basics Signal Frequency = Cycles/Second A typical sine wave Time

  6. Amplitude and Cycle • Amplitude • Distance above reference line • Cycle • One complete wave

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

  8. 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

  9. 1 0 1 1 0 1 0 0 A to D Converters, Digital Signal Processors (DSP) etc. Analog to Digital Conversion

  10. Data Transmission Using Analog Technology Computer Modem Analog 0s and 1s Digital 0s and 1s Digital-to-Analog Modulation and vice versa

  11. Voice Carrier Wave AM Radio Transmission Analog-to-Analog Modulation Voice Transmission Example

  12. End of Module

  13. Module Frequency Spectrum and Bandwidth

  14. 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

  15. Low Frequency High Frequency Radio Frequency Satellite Transmission Voice KHz MHz MHz Microwave Coaxial Cable Frequency Spectrum

  16. Frequency Spectrum • Low-end • Voice band • Middle • Microwave • High-end • Satellite communication

  17. Signal Propagation • Low frequency • Omni-directional • High frequency (In general) • Unidirectional

  18. Bandwidth is 400 MHz 300 MHz 700 MHz Bandwidth Definition • Bandwidth, in general, represents a range of frequencies

  19. 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)

  20. 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

  21. 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.

  22. Coaxial Cable Example • Bandwidth of 300 MHz • Comparison with twisted pair • Higher bandwidth • Supports faster communication speeds

  23. Limiting Factors on Communication Speed Communication Speed Technology Bandwidth

  24. 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

  25. Higher Bandwidth Medium 1 Technology Medium 2 Speed Dependency on Bandwidth and Technology Medium 1 example can be shielded twisted pair and medium 2 example can be fiber.

  26. 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

  27. End of Module

  28. Module An Overview of Digital Technology

  29. Areas of Application • Computers • New telephone networks • Phased introduction of digital television technology

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

  31. 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

  32. Digital Signal 1 0 1 1 0 1 0 0 Signal Strength Pulse Time Pulse Duration

  33. Digital Terms • Pulse • Pulse duration • Pulse amplitude • Signal strength

  34. Pulse Duration MHz Clock Speed and Pulse Duration

  35. 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

  36. 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

  37. 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

  38. End of Module

  39. Module Digital-to-Analog and Analog-to-Digital Conversion

  40. 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

  41. Digital-to-Analog Interface POTS Comp. Sys. 2 Comp. Sys. 1 Modem Modem Analog ITU V.90 Digital Serial RS-232C Digital Serial RS-232C

  42. Digital-to-Digital Interface Comp. Sys. 2 Comp. Sys. 1 DSL Router DSL Router Digital Internet Digital IEEE 802.3 Digital IEEE 802.3

  43. Digital to Digital Interface Network 2 Network 1 Router

  44. Digital to Digital Interface • In general, in digital to digital interface, protocol conversion takes place • Example: Connecting an Ethernet network to a campus backbone network using a router

  45. End of Module

  46. Module Overview of Digitization of Information

  47. Digitization of Information • Information need to be digitized for computer processing and the transmission of information

  48. Components of Information • Alphanumeric data • Image • Audio • Video

  49. Digital Information Processing Data Digitized and Encoded Digital Transmission Audio Image Video

  50. The Advantages of Digitization • Information can be processed by the computer • Easy transmission of information over the Internet and other computer networks • Minimize loss of quality during transmission