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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