CHAPTER Multiplexing

Chapter Objectives Describe direct and inverse multiplexing List and explain the different types of multiplexing techniques used in electronic and optical transmission Give illustrative examples of the use of multiplexers in the field

Chapter Modules Direct and inverse multiplexing Listing of multiplexing techniques and Frequency Division Multiplexing Time Division and Wave Division Multiplexing Practical multiplexer connections

Chapter 11 Direct and Inverse Multiplexing 4/24/2017 MODULE 1 Direct and Inverse Multiplexing (c) Copyright N Ganesan

Overview Of Direct Multiplexing Direct multiplexing or multiplexing is the same as channel splitting It means the splitting of one physical line into multiple communication channels A communication channel is one that engages in a communication session The usage of the term multiplexing in general means direct multiplexing

Direct Multiplexing Example Session 1 Session 1 Mux Mux Session 2 Session 2 Session 3 Session 3 One physical line carrying multiple channels. A B

Sample Application Areas Mainframe-based communication Long-distance links Fiber-optic communication A relatively new introduction Digital lines such as DSL

Overview Of Inverse Multiplexing Combination of multiple transmission lines or multiple communication channels to support a single communication session Binding of multiple transmission lines for the purpose of engaging in a single communication session

Inverse Multiplexing One communication channel Session 1 Session 1 Mux Inv.. Mux Multiple Transmission Lines A B

Bonding Inverse multiplexing is also known as bonding when it is done dynamically For example, this can be achieved in modem and ISDN transmission Bonding is normally carried out dynamically

Sample application Areas Video conferencing Conducted over ISDN lines T-1 line inverse multiplexing ATM inverse multiplexing

Inverse Multiplexing with Analog Lines The primary purpose is to increase the speed of Internet connection made over regular analog telephone lines Modems are being introduced to combine analog telephone lines Combination of two lines operating at 56K bps each results in an effective communication speed of 112K bps

In Summary Direct multiplexing Inverse multiplexing Maximize the economical use of cables Inverse multiplexing Increase the communication speed of a single communication session

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Chapter 11 Communication Lines, Channels and Sessions 4/24/2017 MODULE 2 Communication Lines, Channels and Sessions (c) Copyright N Ganesan

Lines, Channels and Sessions A transmission line is a physical medium that carries the information Coaxial cable A communication channel is a conduit for the flow of information Multiple channels in physical medium A communication session is the actual process of engaging in a communication task

One Transmission Line and Multiple Communication Channels Mainframe Coaxial cable Terminals

Multiple Transmission Lines and One Communication Session 2 B Channels each operating at 64K bps Micro Single Session Multiple ISDN lines (multiple B channels). Combined speed = 6 X 64 = 384K bps

One Transmission Line, One Channel and Multiple Sessions Internet Micro Data Packets Internet client engaged in multiple communication sessions.

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Frequency Division Multiplexing (FDM) MODULE 3 Frequency Division Multiplexing (FDM)

Multiplexing Techniques Frequency Division Multiplexing Time Division Multiplexing Statistical Time Division Multiplexing Wave Division Multiplexing

Direct Multiplexing Techniques Frequency Division Multiplexing Channel division is based on frequency Time Division Multiplexing Time slots are assigned for each channel Statistical Time Division Multiplexing A variation of Time Division Multiplexing concept that optimizes on the concept of Time Division multiplexing Wave Division Multiplexing, the multiplexing is based on different wavelengths of light

Frequency Division Multiplexing (FDM) Analog F1 F1 MUX MUX F2 F2 F3 F3 Each channel is assigned A different frequency (Half-duplex Example) A B

Computer Communication Using FDM Digital Analog Analog Modem MUX Micro One or Modems May Be Incorporated Within the Multiplexer As Well.

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Time Division and Wave Division Multiplexing MODULE 4 Time Division and Wave Division Multiplexing

Time Division Multiplexing in a Nutshell Time division simply allows a fixed period of time for communication for each channel

Time Division Multiplexing (TDM) Digital Analog T1 MUX Modem T2 T3 T1 T2 T3 T1 T2 T3 Time slots are equally divided among channels.

Salient Features of Time Division Multiplexing Each channel is assigned a fixed period of time for transmission The opportunity to transmit is given on a round-robin basis Time division multiplexers can therefore processes the information in digital form A modem is only required to connect a multiplexer to an analog line

Drawback with Time Division Multiplexing TDM assigns a fixed period of time for each channel When a channel does not have any information to transmit during the allocated time period, it still remains connected Either part or the entire portion of the allocated time period is wasted

Statistical Time Division Multiplexing Digital Analog T1 MUX Modem T2 T3 T1 T2 T3 T2 T3 Time slots are not equally divided among channels.

Statistical Time Division Multiplexing Properties STDM is similar to TDM except for one difference A time slice may be shortened due to the absence of data for transmission Each channel is initially assigned a fixed period of time The time period is forfeited in part or in full if there is no data to be transmitted Obviously, STDM is more efficient than TDM

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Wave Division Multiplexing MODULE 5 Wave Division Multiplexing

Wave Division Multiplexing (WDM) Similar to FDM Light waves are involved in place of electronic signals The term wave length is used instead of the term frequency Note that the wave length is inversely proportional to frequency Used in fiber optics transmission

Wave Division Multiplexing Connection Light rays of different wave lengths (frequencies) are assigned for different channels. W1 W1 W2 W2 W3 W3 Detect and differentiate light rays of different wave lengths at the receiving end.

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Practical Multiplexer Connections MODULE 6 Practical Multiplexer Connections

Module Objectives Provide practical examples in the use of multiplexers Use of multiplexers in a mainframe environment Use of multiplexers in Wide Area Networks (WAN)

Use Of Multiplexers in a Mainframe Environment MUX Modem Modem Controller Cluster MUX Terminal Terminal Terminal

Wide Area Multiplexing San Francisco 56 kbps FEP MUX MUX Mainframe MUX 56 Kbps Modem 112 kbps

Wide Area Multiplexing Cont. Los Angeles Long Beach 112 56 Mod. Mod. 56 18.6 28 18.6 18.6 28 Term. Term. Term. Term. Term.

Wide Area Multiplexing Observation Multiple channels are multiplexed and de-multiplexed A combination of multiplexers can be used in combining faster and slower channels

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