The transmitter end contains multiple transmitters and the receiver end contains multiple receivers. The below figure shows the schematic diagram of an FDM system. A guard band is a narrow frequency range that separates two signal frequencies. In other words, there exists a frequency gap between two adjacent signals to prevent signal overlapping. In other words, each user owns a sub-channel.Įach logical sub-channel is separated by an unused bandwidth called Guard Band to prevent overlapping of signals. In this technique, each logical sub-channel (individual signal frequency) is allotted to each user. The individual signals are filtered and then modulated (frequency is shifted), in order to fit exactly into logical sub-channels. Each logical sub-channel is allotted for a different signal frequency. The frequency division multiplexing divides the bandwidth of a channel into several logical sub-channels. In this technique, the bandwidth of the communication channel should be greater than the combined bandwidth of individual signals. Frequency division multiplexing is also known as FDM. This technique combines multiple signals into one signal and transmitted over the communication channel.
We use this technique extensively in TV and radio transmission. It is the most popular multiplexing technique. There are two types of analog multiplexing:įrequency division multiplexing is an analog technique. This can be achieved by separating the signal in frequency. Multiplexing requires that the multiple signals be kept apart so that they do not overlap with each other and thus can be separated at the receiving end. It multiplexes the analog signals according to their frequency or wavelength. The process of combining multiple analog signals into one signal is called analog multiplexing.
The time division multiplexing is again classified into two types: In digital multiplexing, the Time Division Multiplexing is the most popular technique. Multiplexing is mainly classified into two types:Īnalog multiplexing is again classified into two types: In this technique, the bandwidth is effectively used. Thus, it uses only one communication channel to carry 3 signals (multiple signals). The below figure shows the communication system with multiplexing. In this technique, a large amount of bandwidth is wasted. Thus, it uses three communication channels to carry three signals. The communication system without multiplexing carries only one signal at any moment in time.
The below figure shows the communication system without multiplexing. Without Multiplexing vs With Multiplexing The multiplexer combines n input lines to generate one output line. Multiplexing is done by using a device called Multiplexer or MUX. Multiplexing has-been used for many years in long-distance telephony. Thus, the multiple signals are sent simultaneously over a shared communication channel (medium). Each logical sub-channel is dedicated to an individual signal. The multiplexing technique divides the communication channel into several logical sub-channels. Multiplexing is also sometimes referred to as muxing. Multiplexing is a technique which combines multiple signals into one signal, suitable for transmission over a communication channel such as coaxial cable or optical fiber. By using the multiplexing technique, we can easily send multiple signals simultaneously over a communication channel (medium). However, we can overcome this drawback by using a technique called multiplexing. Generally, a communication channel such as an optical fiber or coaxial cable can carry only one signal at any moment in time.