Multiplexing in Mobile Computing

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:

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.

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.

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.

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.