Let us understand what Frequency-Division Multiplexing (FDMA) is.
Frequency-Division Multiplexing is an analog method used when the channel’s bandwidth is higher than the consolidated bandwidths of the signals to be broadcasted.
In FDMA, there are several frequencies that are combined into an individual combined signal and shared on the channel. At the receiver end, the reverse procedure is used to receive the single frequencies back for operating.
The entire bandwidth of the channel is divided into logical channels, and each sending device is given with the possession of a logical channel.
When the signal appears at the receiver in the composite architecture, it has to be disconnected into individual signals. This is done by a device referred to as a demultiplexer.
There are various applications of FDMA which are as follows −
A widespread application of FDM is AM and FM radio transmission. Radios use the air as the transmission medium. A unique band, from 530 to 1700 kHz, is authorized to AM radio. All radio stations are required to send this band.
Each AM station requires 10 kHz of bandwidth. Each station uses multiple carrier frequencies, which represent it is drifting its signal and multiplexing.
The signal which goes to the air is a sequence of all signals.
A receiver makes all these signals but penetrates (by tuning) only the acquired. Without multiplexing, just one AM station can be communicated to the shared connection, the air.
The situation is similar to FM broadcasting. FM uses a wider band, 88 to 108 MHz due to each station requiring higher bandwidth, 200 kHz.
The first creation of cellular telephones also uses FDM. Each client has authorized two 30 kHz mediums, one for transmitting voice and one for receiving.
The voice signal with a bandwidth of 3 kHz (from 300 to 330 Hz) is adjusted by utilizing FM.
TDM is a digital procedure. In TDM, each sender is given the entire possession of the whole bandwidth of the channel for a fixed duration of time. After this, the control is moved to the next sender, and the procedure continues on a round-robin basis.
An example of TDM is the television broadcast. In a television serial, generally, a 10 minutes serial is followed by a 5 minutes advertisement. The time in which the serial is being advertised, the whole frequency is dedicated to the serial.
The variants on TDM are as follows −
ATDM (Asynchronous Time Division Multiplexing) − Multiplexing in which the data is transmitted asynchronously.
STDM (Statistical Time Division Multiplexing) − A multiplexing method that polls nodes and immediately skips any nodes with nothing to send.
STM (Synchronous Transfer Node) − It is designed for use in BISDN (broadband ISDN) and also provided in the SONET (Asynchronous Optical Network) architecture.