Multiplexing

By: Muhammad Hanif

Agenda

Multiplexing MUX and DEMUX Frequency Division Multiplexing Wavelength Division Multiplexing Time Division Multiplexing

Multiplexing Multiplexing is the set of techniques that

allows the simultaneous transmission of multiple signals across a single data link.

Using one data link for multiple signals to transmit.

A Multiplexer (MUX) is a device that combines several signals into a single signal.

A Demultiplexer (DEMUX) is a device that performs the inverse operation.

Categories of Multiplexing

Frequency-division Multiplexing (FDM)

FDM is an analog technique that can be applied when the bandwidth of a link is greater than the combined bandwidths of the signals to be transmitted.

A number of signals are carried simultaneously on the same medium by allocating to each signal a different frequency band.

Frequency-division Multiplexing (FDM) In FDM signals

generated by each device modulate different carrier frequencies. These modulated signals are combined into a single composite signal that can be transported by the link.

FDM is an analog multiplexing technique that combines signals.

Modulating (Modulation) Digital information is modulated (changed) on the

carrier signal by modifying one or more of its characteristics (amplitude, frequency, phase).

This kind of modification is called modulation and the information signal is called a modulating signal.

Demodulation Vice versa

Modulation Time-domain description

Wave-division Multiplexing (WDM) Wave-division multiplexing is conceptually the

same as FDM, except that multiplexing and demultiplexing involve light signals transmitted through fiber-optic channels.

The purpose is to combine multiple light sources into one single light at the multiplexer and do the reverse at the demultiplexer.

Combining and splitting of light sources are easily handled by a prism.

Time-division Multiplexing (TDM)

Time-division multiplexing (TDM) is a digital process that can be applied when the data rate capacity of the transmission medium is greater than the data rate required by the sending and receiving devices.

TDM

TDM is a digital multiplexing technique to combine data.

Time-division Multiplexing (TDM) TDM can be implemented in two ways:

synchronous TDM and asynchronous TDM. In synchronous time-division multiplexing, the

term synchronous means that the multiplexer allocates exactly the same time slot to each device at all times, whether or not a device has anything to transmit.

FramesTime slots are grouped into frames. A frame

consists of a one complete cycle of time slots, including one or more slots dedicated to each sending device.

TDM frames

TDM frames

Asynchronous TDM

Synchronous TDM does not guarantee that the full capacity of a link is used. Because the time slots are preassigned and fixed, whenever a connected device is not transmitting, the corresponding slot is empty.

Asynchronous time-division multiplexing, or statistical time-division multiplexing, is designed to avoid this type of waste.

Like synchronous TDM, asynchronous TDM allows a number of lower-speed input lines to be multiplexed to a single higher-speed line.

•In an asynchronous system, if we have n input lines, the frame contains no more than m slots, with m less than n.

•In this case any slot is available to any of the attached input lines that has data to send.

Summary

Multiplexing MUX and DEMUX Frequency Division Multiplexing Wavelength Division Multiplexing Time Division Multiplexing