Modems: Standards, Data Compression, Error Correction, and Practical Applications, Slides of Data Communication Systems and Computer Networks

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Modems

Chapter Objectives

• Discuss basic modem related issues
  • Standards, Hayes compatibility etc.
• Describe the different types of practical modems available
  • Internal, external, null, short-haul modems etc.
• Present the profile of sample practical modems
  • Asynchronous and synchronous modems
• Show the establishment of a fiber-optic communication link using the fiber-optic interface

END OF CHAPTER INTRODUCTION

MODULE

Modem Functional Considerations

Major Modem Standards

• ITU standard
  • Universal standard
  • Currently in use
• Bell standard
  • Earlier low speed modem standard
  • No more in use

Standards in Modem Communication

• Modulation standard
• Data compression standard
• Error correction Standard

Data Compression Standards in Modem

• MNP 5

• ITU V.42 bis

Error Correction Standard

• MNP 2- 4

Command Translation for PCs and Modems

• Commands for the PC
  • Translated into machine language and executed
    • E.G. Identifying a file for transmission
• Commands for the modem
  • Generated in Hayes AT command set form and transmitted to the modem for execution - E.G. Command instructing the modem to dial

Command Translation

Software Intel Micro Modem

Intel Machine Code

Hayes AT Command

END OF MODULE

MODULE

Internal, External and Portable Modems

Internal Modems

Source: Black Box docsity.com

External Modems

Source: Black Box docsity.com