1 / 145

Chapter

Chapter. Overview of Analog and Digital Technologies. 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

nantai
Download Presentation

Chapter

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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

More Related