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Multiplexing is a way of transmitting multiple signals through a channel. But the transmission of multiple signals is very challenging. But, the multiplexing technique makes it feasible.
Analog Multiplexing
When multiple analog signals are combined into a single analog signal, the process is called analog multiplexing. The multiplexing is done according to their frequency or wavelength.
Multiplexing needs multiple signals to be kept separately in a way that they are not overlapped. This leads to separation at the endpoint. This goal is reachable by separating the frequencies of the signals.
Analog multiplexing itself is divided into two sub-categories: Frequency Division Multiplexing (FDM), and Wavelength Division Multiplexing (WDM). Among these categories, FDM is more popular.
Digital Multiplexing
Digital multiplexing refers to the operation of combining multiple digital signals into a single signal. The most well-known method of digital multiplexing is Time Division Multiplexing (TDM). Synchronous TDM and Asynchronous TDM are two types of Time Division Multiplexing.
Applications of Multiplexing
Data transmission techniques based on multiplexing are widely used in sending communication signals. Below are some of these applications.
- Multiplexing in satellites
- Multiplexing in telemetry
- Multiplexing in radio broadcasting
- Multiplexing in telephone networks
- Multiplexing in computer memories to carry the data from a memory location.
- Multiplexing in TV broadcastings
- Multiplexing in telecommunication systems
- Multiplexing in video processing
Advantages of Multiplexing
The advantages of using multiplexing include the following.
- The use of multiplexing reduces the complexity of the circuit and its components, decreasing the costs of the communication system.
- This system makes optimal use of bandwidth.
- A multiplexing system can pass several signals through one channel at the same time.
Disadvantages of Multiplexing
When transmitting data analog or digitally using a multiplexer, the signals must be synchronized.
The following figure shows the multiplexing process using the FDM method.
Unlike Frequency Division Multiplexing where signals of different frequencies are transmitted together, in Time Division Multiplexing, signals are transmitted at the same frequencies but at different times.
Synchronous TDM
In synchronous Time Division Multiplexing, all transmitters are assigned with fixed time intervals. The device must send data within the allocated time slot. Even if they do not have a signal to transmit, this time is assigned to them and in this case, the time slot of the device without data is empty.
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