Making Connections Efficient: Multiplexing and Compression

1
Making Connections Efficient Multiplexing and
Compression

• Chapter 5

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Objectives

• Define Multiplexing
• Characteristics of Multiplexing
• Types of Multiplexing
• Frequency Division
• Time Division
• Synchronous Time Division
• Statistical Time Division
• Wavelength time division
• Code division
• Comparison of multiplexing techniques
• Compression (Lossless vs. Lossy) -- SKIP

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What is Multiplexing?

• Technique of transmitting multiple signals over a
  single medium
• Medium is divided, giving each signal a portion
  of total bandwidth
• Performed at the network access layer of the
  TCP/IP model

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Multiplexors (MUX)

• Break one high-speed communications circuit into
  several lower speed circuits so that many
  different devices can use it simultaneously (to
  send and receive data)

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Other characteristics

• Multiplexing is done in multiples of 4
• Capacity of multiplexer ? of the capacity of
  circuits it combines
• Used with analog signaling
• Guard bands are used to prevent interference

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Types of Multiplexing

• Frequency Division Multiplexing (FDM)
• Time Division Multiplexing (TDM)
• Synchronous TDM
• T-1 multiplexing
• ISDN multiplexing
• SONET
• Statistical TDM
• Wavelength division multiplexing
• Code division multiplexing

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Frequency Division Multiplexing

• Oldest, simplest, and most widely used
• Divides circuit capacity horizontally
• Medium is divided into separate channels by
  assigning each channel a different frequency used
  to transmit users signals
• Applications

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Frequency Division Multiplexing (continued)
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Time Division Multiplexing

• Used for digital transmission
• Doesnt need guard bands
• Divides available transmission time on a medium
  among users
• Only one user at a time transmits

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Synchronous TDM

• Take turns in round-robin fashion
• Types of sync TDM
• T-1 multiplexing
• ISDN multiplexing
• SONET
• Developed by ANSI
• Transmission over fiber optic cable

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Synchronous Time Division Multiplexing (continued)
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Statistical TDM

• Transmission speed is selected based on a
  statistical analysis of the usage requirements of
  the circuits to be multiplexed
• Only transmits data from active users

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Statistical Time Division Multiplexing (continued)
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Wavelength division multiplexing

• Multiplexes multiple data streams onto a single
  fiber optic line
• Uses different wavelength (or frequency)
  (colored) lasers to transmit multiple signals at
  the same time over a single medium
• Wavelength laser is known as lambdas

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Code division multiplexing

• Assigns unique digital codes to each user
• Based on spread spectrum technology
• Used by military, cell telephone companies

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Comparison of Multiplexing Techniques
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Comparison of Multiplexing Techniques (continued)