ITT300 Chapter 5: Multiplexing

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Questions and Answers

What is the primary purpose of multiplexing in data communication?

To eliminate the need for multiple data links.

To allow simultaneous transmission of multiple signals over a single link. (correct)

To enhance the security of data transmissions.

To reduce the overall bandwidth of the connected devices.

What role does a multiplexer (MUX) play in a multiplexing system?

It combines multiple signals into a single stream. (correct)

It separates composite signals into individual components.

It regulates the bandwidth allocation among devices.

It generates carrier frequencies for the modulated signals.

What is the function of a demultiplexer (DEMUX) in data communication?

To manage the bandwidth allocation for sending devices.

To combine various data streams into one.

To separate a composite signal back into its original channels. (correct)

To convert analog signals into digital form.

In Frequency Division Multiplexing (FDM), what does each signal modulate?

A unique carrier frequency. Signup and view all the answers

How does multiplexing contribute to the efficiency of bandwidth usage?

By allowing multiple devices to share a single link's bandwidth. Signup and view all the answers

What does the term 'link' specifically refer to in the context of multiplexing?

The physical path for data transmission. Signup and view all the answers

What is the minimum required bandwidth for four channels with three guard bands?

69 kHz Signup and view all the answers

How much bandwidth does an individual television channel require?

6 MHz Signup and view all the answers

What technology is used to multiplex and demultiplex optical signals in fiber-optic cables?

Wavelength-Division Multiplexing Signup and view all the answers

What is the primary difference between FDM and WDM?

FDM transmits signals in electrical form while WDM transmits in optical form. Signup and view all the answers

Which of the following correctly describes a feature of Time-Division Multiplexing (TDM)?

TDM allows several low-rate connections to share the high bandwidth of a link. Signup and view all the answers

What device allows a television to select which channel to receive in a cable system?

Demultiplexer Signup and view all the answers

What role do prisms play in wavelength-division multiplexing?

They combine and split light signals based on frequency. Signup and view all the answers

What is the approximate bandwidth of a coaxial cable used in cable television?

500 MHz Signup and view all the answers

What is the frame rate of the multiplexer when each channel sends data at a rate of 100 bytes/s?

100 frames per second Signup and view all the answers

What is the bit rate achieved by the multiplexer when each frame carries 4 bytes?

3200 bps Signup and view all the answers

What does TDM interleaving allow in the context of data transmission?

Synchronized sending and receiving of data units Signup and view all the answers

What is one drawback of synchronous TDM described in the content?

It may result in empty slots in output frames Signup and view all the answers

What does synchronous TDM primarily share among input connections?

Time Signup and view all the answers

What is a challenge when using TDM with input data rates that are not the same?

Determining how to handle differing data rates Signup and view all the answers

What are the two switches in the TDM interleaving process responsible for?

Rotating in opposite directions to synchronize connections Signup and view all the answers

In synchronous TDM, what does each input connection occupy?

One output time slot Signup and view all the answers

If the data rate of each input connection is 1 kbps, what is the duration of each input unit?

1 ms Signup and view all the answers

How is the duration of each output time slot calculated if the data rate of the output link is three times faster than the input?

It is one-third the input time slot Signup and view all the answers

What is the duration of each frame in synchronous TDM when it carries three output time slots?

1 ms Signup and view all the answers

If four channels are multiplexed with each sending 100 bytes/s, what is the size of each frame if one byte is multiplexed per channel?

400 bytes Signup and view all the answers

What does a complete cycle of time slots in synchronous TDM refer to?

A frame Signup and view all the answers

Which characteristic makes synchronous TDM not the most efficient method?

Dedicated time slots Signup and view all the answers

What is the data rate of each source in bits per second?

2000 bps Signup and view all the answers

What is the duration of each character in seconds?

4 ms Signup and view all the answers

How many frames are sent per second by the link?

250 frames/s Signup and view all the answers

What is the duration of each frame in seconds?

4 ms Signup and view all the answers

How many bits are there in each frame before adding the synchronizing bit?

33 bits Signup and view all the answers

What is the data rate of the link in kilobits per second?

300 kbps Signup and view all the answers

How many bits does Channel A contribute to the multiplexed output frame?

1 bit Signup and view all the answers

Which channel has a bit rate of 200 kbps?

Channel B Signup and view all the answers

Study Notes

Multiplexing Overview

Allows simultaneous transmission of multiple signals over a single data link to prevent bandwidth wastage.
Utilizes multiplexers (MUX) to combine signals into one stream and demultiplexers (DEMUX) to separate the stream back into individual transmissions.

Link and Channel

A link refers to the physical path, while a channel is a portion of a link that carries transmission between lines.
A single link can have multiple channels.

Basic Multiplexing Techniques

Three main techniques: Frequency Division Multiplexing (FDM), Wavelength Division Multiplexing (WDM), and Time-Division Multiplexing (TDM).

Frequency Division Multiplexing (FDM)

An analog technique that uses different carrier frequencies to modulate signals, allowing transmission through a common medium.
Requires guard bands to prevent overlapping, with a formulated bandwidth requirement for effective transmission.
Commonly used in cable television and AM/FM radio broadcasting.

Wavelength Division Multiplexing (WDM)

Applies high-data-rate capabilities of fiber-optic cables, optimizing bandwidth usage.
Combines narrow bands of light for transmission and separates them at the receiver using prisms, exploiting different frequencies.

Time-Division Multiplexing (TDM)

A digital multiplexing technique that shares time slots among multiple connections on high-bandwidth links.
Each data flow is allocated specific time slots for transmission, enhancing efficiency but may lead to empty slots if sources have no data to send.

Synchronous TDM

Divides each input connection's data into units, with each occupying one time slot.
Frames group time slots, with the output data rate needing to be n times that of connected inputs.

TDM Example Calculations

Frame duration equals the duration of input units; for a rate of 1 kbps, input slot = 1 ms, output slot = 1/3 ms, frame = 1 ms.
For multiple channels sending data, the frame size and bit rate calculations determine overall efficiency.

Efficiency and Interleaving in TDM

Incorporates interleaving through synchronized switches that open and allow data transmission from sources.
Handles disparities in data rates through strategies like adjusting time slots or using alternate multiplexing methods.

Statistical Time-Division Multiplexing

Unlike synchronous TDM, statistical TDM does not reserve fixed slots for each input, resulting in better bandwidth utilization when sources are varied.

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Description

Explore the fundamentals of multiplexing in data communication and networking. This chapter delves into techniques that enable simultaneous transmission of multiple signals over a single data link. Enhance your understanding of how multiplexers work and their role in efficient bandwidth utilization.