Multiplexing is combining several separate signals so that they can share one transmission channel.

Describe frequency division multiplexing.

The channel's bandwidth is divided into separate frequency bands and each source is carried on its own band, so all of them travel simultaneously without interfering.

What does statistical time division multiplexing do better than plain time division multiplexing?

It allocates slots only to the sources that actually have data waiting, so capacity is not wasted on sources that are idle.

State the job of a multiplexer and of a demultiplexer.

The multiplexer combines the incoming streams onto the shared line, and the demultiplexer separates them again at the far end and delivers each to the correct destination.

WJEC A-Level Computer Science 601-5345-3

Hardware: Architecture, Memory and Storage

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Networks and Data Transmission

Multiplexing and switching

3 things to know
AS Unit 1

Overview

Time division multiplexing, frequency division multiplexing and job of a multiplexer and of a demultiplexer.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Define multiplexing.

Key term

Why is multiplexing needed?

Key term

Describe time division multiplexing.

Questions from this subtopic

Each one with the model answer underneath.

1
Define multiplexing.
Model answer
Multiplexing is combining several separate signals so that they can share one transmission channel.
2
Why is multiplexing needed?
Model answer
Providing a separate physical line for every conversation would be enormously expensive, and a single high-capacity line would otherwise sit idle for most of the time.
3
Describe time division multiplexing.
Model answer
Each source is given the whole channel for a short slot in a repeating rotation, so the sources take strict turns fast enough that each appears continuous.
4
Describe frequency division multiplexing.
Model answer
The channel's bandwidth is divided into separate frequency bands and each source is carried on its own band, so all of them travel simultaneously without interfering.
5
What does statistical time division multiplexing do better than plain time division multiplexing?
Model answer
It allocates slots only to the sources that actually have data waiting, so capacity is not wasted on sources that are idle.
6
State the job of a multiplexer and of a demultiplexer.
Model answer
The multiplexer combines the incoming streams onto the shared line, and the demultiplexer separates them again at the far end and delivers each to the correct destination.

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