What is Multiplexing & How it works?
Multiplexing is a technique in which multiple signals are combined into a single signal and transmitted over a shared medium. Multiplexing is commonly used in networking to increase the efficiency of the transmission medium, as it allows multiple users to share the same communication link. In the physical layer of the network, there are different types of multiplexing techniques used. In this article, we will discuss each type of multiplexing in detail.
- Frequency Division Multiplexing (FDM)
Frequency division multiplexing (FDM) is a technique in which multiple signals are transmitted over a shared medium using different frequency bands. Each signal is assigned a separate frequency band, and the signals are combined at the transmitter end and then separated at the receiver end. FDM is commonly used in analog communication systems, such as radio and television broadcasting.
In FDM, each signal is modulated onto a different carrier frequency, and the modulated signals are then combined using a mixer. The combined signal is transmitted over a shared medium, such as a cable or airwaves. At the receiver end, the signal is separated using a demultiplexer, which extracts the individual signals and their carrier frequencies.
- Time Division Multiplexing (TDM)
Time division multiplexing (TDM) is a technique in which multiple signals are transmitted over a shared medium using different time slots. In TDM, the signals are divided into fixed-size time slots, and each signal is transmitted in a different time slot. TDM is commonly used in digital communication systems, such as telephony and digital subscriber lines (DSL).
In TDM, each signal is sampled at a regular interval, and the samples are grouped into frames. Each frame consists of a fixed number of time slots, and each time slot is assigned to a different signal. The frames are transmitted over a shared medium, such as a cable or airwaves. At the receiver end, the frames are separated using a demultiplexer, which extracts the individual signals from the time slots.
- Statistical Time Division Multiplexing (STDM)
Statistical time division multiplexing (STDM) is a variation of TDM that is used when the data rate of the signals varies over time. In STDM, the time slots are not fixed in size, and they are allocated to the signals based on their data rate. Signals with a high data rate are given more time slots than signals with a low data rate.
STDM is commonly used in digital communication systems, such as Ethernet networks. In STDM, each signal is assigned a priority level, and the signals with higher priority are given more time slots. This ensures that the high-priority signals are transmitted with minimal delay, while the low-priority signals are transmitted only when there is spare capacity on the communication link.
- Code Division Multiplexing (CDM)
Code division multiplexing (CDM) is a technique in which multiple signals are transmitted over a shared medium using different code sequences. In CDM, each signal is assigned a unique code sequence, and the signals are combined using a code division multiplexer. The combined signal is transmitted over a shared medium, such as a cable or airwaves.
At the receiver end, the signal is separated using a code division demultiplexer, which extracts the individual signals using their unique code sequences. CDM is commonly used in digital communication systems, such as code division multiple access (CDMA) mobile networks.
Multiplexing is a powerful technique that is widely used in networking to increase the efficiency of the transmission medium. Each type of multiplexing has its own advantages and disadvantages, and the choice of multiplexing technique depends on the requirements of the communication system. Network administrators should carefully evaluate the different types of multiplexing available and select the most appropriate one for their specific needs. By using multiplexing, multiple signals can be transmitted over the same medium, which reduces the need for additional communication links and lowers the overall cost of the communication system.
In addition to the types of multiplexing discussed above, there are also other types of multiplexing techniques used in networking, such as wavelength division multiplexing (WDM) and space division multiplexing (SDM). These techniques are used in more advanced communication systems, such as fiber optic networks and wireless communication systems.
Overall, multiplexing is an essential technique that allows multiple users to share the same communication link, which increases the efficiency of the transmission medium and reduces the cost of the communication system. By understanding the different types of multiplexing available, network administrators can select the most appropriate technique for their specific needs and ensure that their communication system operates efficiently and effectively.