Frequency Division Multiplexing (FDM)
The frequency spectrum is divided among the logical channels and each user has exclusive access to his channel. It sends signals in several distinct frequency ranges and carries multiple video channels on a single cable. Each signal is modulated onto a different carrier frequency and carrier frequencies are separated by guard bands. The bandwidth of the transmission medium exceeds the required bandwidth of all the signals. Usually, for frequency division multiplexing analog signaling is used in order to transmit the signals, i.e. more susceptible to noise. Assignment of non-overlapping frequency ranges to each user or signal on a medium. Thus, all signals are transmitted at the same time, each using different frequencies.
The multiplexer is attached to the high-speed communication line. The frequency spectrum is divided up among the logical channels where each user hangs onto a particular frequency. The radio spectrum is an example of the media and the mechanism for extracting information from the medium.
Advantages of FDM
- The process is simple and easy to modulate.
- A corresponding multiplexer or de-multiplexer is on the end of the high-speed line and separates the multiplexed signals.
- For frequency division multiplexing analog signaling is used in order to transmit the signals.
Disadvantages of FDM
- One problem with FDM is that it cannot utilize the full capacity of the cable.
- It is important that the frequency bands do not overlap.
- There must be a considerable gap between the frequency bands in order to ensure that signals from one band do not affect signals in another band.
Multiplexing (Channel Sharing) in Computer Network
Multiplexing means multiple sources but one link. An alternative approach is a Direct point-to-point connection, but it has several problems as it requires an I/O port for each device, a need line for each device, and also a large amount of wiring needed if on different floors. Instead, if we use a multiplexer approach then all devices are connected to MUX and one line to the host, the link carries multiple channels of information and several lines equal to the number of lines out.