Multiplexing in Mobile Computing

Mobile Computing Tutorial



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Multiplexing : Introduction

  • Multiplexing is a technique in which, multiple simultaneous analog or digital signals are transmitted across a single data link.
  • The concept behind it is very simple: Proper Resource Sharing and its Utilization.
  • It can be classified into four types. These are:

 

This image describes the different techniques of multiplexing in mobile computing.

Multiplexing : Mobile Computing

 

Multiplexing : Frequency Division Multiplexing(FDM)

  • In Frequency Division , the frequency dimension spectrum is split into bands of smaller frequency.
  • FDM is used because of the fact that, a number of frequency band can work simultaneously without any time constraint.

 

This image describes the frequency division multiplexing in mobile computing.

Frequency Division

 

Advantages of FDM

  • This concept is applicable on both analog signals as well as digital signals.
  • Simultaneous signal transmission feature.

 

Disadvantages of FDM

  • Less Flexibility.
  • Bandwidth wastage is high and can be an issue.

For Example : Frequency Division Multiplexing can be used for radio station in a particular region as every radio station will have their own frequency and can work simultaneously without having any constraint of time.

 

Multiplexing : Time Division Multiplexing(TDM)

  • Time Division  is used for a particular amount of time in which the whole spectrum is used.
  • Time frames of same intervals are made such that the entire frequency spectrum can be accessed at that time frame.

 

This image describes the time division multiplexing in mobile computing.

Time Division

 

Advantages of TDM

  • Single user at a time.
  • Less complex and more flexible architecture.

Disadvantages of TDM

  • Difficult to implement.

For Example : ISDN(Integrated Service for Digital Network) telephonic service.

 

Multiplexing : Code Division Multiplexing(CDM)

  • In Code Division Multiplexing, every channel is allotted with a unique code so that each of these channels can use the same spectrum simultaneously at same time.

 

This image describes the code division multiplexing in mobile computing.

Code Division

 

Advantages of CDM

  • Highly Efficient.
  • Less Inference.

Disadvantages of CDM

  • Less data transmission rates.
  • Complex in nature.

For Example : Cell Phone Spectrum Technology(2G, 3G etc.).

 

Multiplexing : Space Division Multiplexing(SDM)

  • Space Division can be called as the combination of concepts of Frequency Division Multiplexing and Time Division Multiplexing.
  • In SDM, the goal is to pass messages or data parallelly with the use of specific frequency at certain interval of time.
  • It means, a particular channel for some amount of time will be used against a certain frequency band.

 

Advantages of SDM

  • High Data transmission rate.
  • Optimal Use of Time and Frequency bands.

Disadvantages of SDM

  • Inference Problems.
  • High inference losses.

For Example : GSM(Global Service For Mobile) Technology.