Multiplexing may be defined as the process of transmitting many low speed data streams on a higher speed data streams.
In telecommunications and computer networks , multiplexing is a terms used to refer to a process where multiple analog message signals or digital data streams are combined into one signal over a shared medium. The aim is to share an expensive resource.
For example , in telecommunications , several phone calls may be transferred using one wire.
The two most basic forms of multiplexing are time-division Multiplexing (TDM) and Frequency-division Multiplexing(FDM) , both either in analog or digital form. FDM requires modulation of each signal.
Time-division Multiplexing(TDM):-
This is a type of digital or analog multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel , but are physically taking turns on the channel.
The time domain is divided into several recurrent timeslots of fixed length, one for each sub-channel. A sample byte or data blocks of sub-channel 1 is transmitted during timeslot 1, sub - channels 2 during timeslot 2 , etc. One TDM frame consists of timeslot per sub - channel. After the last sub - channel the cycle starts all over again with a new frames, starting with the second sample , byte or data block from sub - channel 1, etc.
Frequency division Multiplexing (FDM):-
This is a fixed user in the complete channel bandwidth. This technique is mainly used for modulated signal. the reason is that , a modulated signal can be placed in any frequency band by just changing the carrier frequency. However at the receiver end , these frequency multiplexed signals can be separated by the use of tuned circuits i. e., band pass filters of their respective frequency band. and for every band , there are independent tuned circuits and demodulators.
In optical networks communications , FDM is referred to as wavelength - division - multiplexing (WDM).
Digital bit streams can be transferred over an analog channel by means of code - division - multiplexing (CDM) techniques such as Frequency - Hopping Spread Spectrum (FHSS) and direct - sequence spread spectrum (DSSS).
In telecommunications and computer networks , multiplexing is a terms used to refer to a process where multiple analog message signals or digital data streams are combined into one signal over a shared medium. The aim is to share an expensive resource.
For example , in telecommunications , several phone calls may be transferred using one wire.
The two most basic forms of multiplexing are time-division Multiplexing (TDM) and Frequency-division Multiplexing(FDM) , both either in analog or digital form. FDM requires modulation of each signal.
Time-division Multiplexing(TDM):-
This is a type of digital or analog multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel , but are physically taking turns on the channel.
The time domain is divided into several recurrent timeslots of fixed length, one for each sub-channel. A sample byte or data blocks of sub-channel 1 is transmitted during timeslot 1, sub - channels 2 during timeslot 2 , etc. One TDM frame consists of timeslot per sub - channel. After the last sub - channel the cycle starts all over again with a new frames, starting with the second sample , byte or data block from sub - channel 1, etc.
Frequency division Multiplexing (FDM):-
This is a fixed user in the complete channel bandwidth. This technique is mainly used for modulated signal. the reason is that , a modulated signal can be placed in any frequency band by just changing the carrier frequency. However at the receiver end , these frequency multiplexed signals can be separated by the use of tuned circuits i. e., band pass filters of their respective frequency band. and for every band , there are independent tuned circuits and demodulators.
In optical networks communications , FDM is referred to as wavelength - division - multiplexing (WDM).
Digital bit streams can be transferred over an analog channel by means of code - division - multiplexing (CDM) techniques such as Frequency - Hopping Spread Spectrum (FHSS) and direct - sequence spread spectrum (DSSS).
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