Notes On Chapter Five -- Overview of Data Communications

• 5.0 Study Guide
  
  
  • Understand that because we need multiple streams of possibly different kinds of information to be transmitted over different types of shared media, we require a range of types of encoding/decoding, encryption/decryption, multiplexing/demultiplexing, and modulation/demodulation.
  
  
• 5.1 Introduction
  
  
  • Transmission of information across media
  
  
  
  
• 5.2 The Essence of Data Communication
  
  
  • The subject involves concepts from mathematics, physics and electrical engineering.
  
  
• 5.3 Motivation and Scope of the Subject
  
  
  • sources of info can be of arbitrary types
  • transmission uses a physical system
  • multiple sources of information may be able to share a medium
  • real physical systems have limitations
  
  
• 5.4 The Conceptual Pieces of a Communication System
  
  
  • Transmitting multiple sources of information across a shared medium is not as simple as it may seem. It doesn't "just work" if a bunch of people shout at each other in a hallway.
  • Issues:
    • encoding information (e.g. digitizing)
    • encrypting information
    • error detection and correction
    • multiplexing/demultiplexing
  
  
  
  
  
  
• 5.5 The Subtopics of Data Communications
  
  
  • Sources of information can be analog or digital.
  • There are reasons to transform one digital form into another, for example to achieve compression.
  • Security considerations may require the addition of encryption.
  • Channel coding for detection and correction of errors in bit values
  • Mulitplexing/Demultiplexing - ways to combine different streams of information for transmission and separate them out at the destination.
  • Modulation/Demodulation - e.g digitizing for transmission and then translating back into analog at the destination.
  • Properties of Physical Channels - e.g. bandwidth, noise, interference, channel capacity, and transmission modes: serial and parallel.