How do FDM and TDM differ

Multiplex and multiplexing

Multiplexing is about the division of the transmission paths in communication technology in order to make optimal use of them. Multiplexing includes processes that bundle or time interleave several signals in order to transmit them simultaneously or together on the transmission medium. This reduces costs, increases reliability, increases bandwidth and some technical solutions are only feasible.

Difference: multiplexing and multiple access

In connection with multiplexing, we speak of multiplexing and also of multiple access. The multiplexing and multiple access methods are used to share the transmission medium and are essentially the same.

At Multiplexing are processes in which a multiplexer bundles several signals at the beginning of a transmission path. At the end of the transmission path, a demultiplexer divides them again into individual signals.

At Multiple access it is about participants sharing the transmission medium and access to it being regulated independently. There are two ways of doing this. Either a central component decides on the allocation of access rights or the participants work with a collision detection system that takes effect when two participants send at the same time.

Overview: multiplex method (incomplete)

SDM - Space Division Multiplex (space division multiplex)

The space division multiplex process involves the transmission or switching of several signals or connections via several available transmission paths. A transmission path is made exclusively available to a signal. A distinction can be made between wired and wireless room multiplex.

TDM - Time Division Multiplex (time division multiplex method)

In time division multiplex systems, the bandwidth on the transmission medium is divided over time. In so-called channels, the data streams get a certain time for a certain time
Bandwidth available. Time division multiplex transmits the connections over time-interleaved channels. Time division multiplex is therefore very suitable for digital signals. The data stream can be divided and reassembled as required.

FDM - Frequency Division Multiplex (frequency division multiplex method)

In frequency division multiplexing, a wide frequency band is divided into several narrow frequency bands. Every single frequency band has a carrier frequency. A single data channel is assigned to this carrier frequency. The data are transmitted simultaneously and independently of one another.

CDM - Code Division Multiplex (Code Division Multiplex)

CDM is also known as code division multiplexing. It is similar to the time division multiplex method. The signals are transmitted with a different coding. Based on the coding, the receiver can recognize the signal that is being sent to it.

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The communication technology primer is a book about the basics of communication technology, transmission technology, networks, radio technology, mobile communications, broadband technology and Voice over IP.

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