Multiplexing techniques

Multiplexing is a technology to transfer digital or analog data in daily use devices like telephone and television. Here, we discuss the various multiplexing technologies used for data transmission.

Multiplexing is a method of combining multiple analog massage signals or digital data streams into one signal. The objective of this technology is to share an expensive medium for transmitting multiple signals. Actually, the low-level communication signals are divided into high-level logical channels using this technology. Furthermore, each channel is then used for transmitting one message signal or data stream.
Time Division
The time division multiplexing technology uses a multiplexor to collect and store incoming signals from the slow lines connected to it by distributing a time slot on the fast link to each in turn. The message signals are sent one after another. They are then received and separated by a demultiplexor according to the time slot provided for each signal. The transmission speed of the fast link is equal to the sum of all the slow speed signals coming into the multiplexor.
There are two methods of time division multiplexing.
Synchronous TDM
The multiplexor used in this method distributes equal time to each device connected to it. It gives the time slot for the device, too, that doesn’t transmit any signal at a particular time, which means this method gives a time slot to each device whether they are transmitting signals or not. This is the main drawback of this system because there would be many times when the distributed time slices are not being used. Therefore, this method doesn’t provide maximum line usage and efficiency. It is used basically in T1 and E1 connections.
Asynchronous TDM
The asynchronous multiplexing technique is far better than synchronous multiplexing. In this system, time slots are allocated only for devices that have something to transfer. Therefore, this technique requires more processing time than synchronous TDM. However, we achieve maximum efficiency and line usage using this technique. Asynchronous Transfer Mode network is a well-known data transfer system that uses this technology.


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