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The Types of Multiplexing Explained

Matthew George | Thursday, February 17, 2022

The Types of Multiplexing Explained

Telecommunication and computer networks use multiplexing to transmit and receive steams of information. combining multiple messages simultaneously on the same physical or logical transmission medium. With the sheer volume of modern communications like computer networks, telephone, and television, which all provide fast communication across large distances almost instantly, multiplexing allows the shared use of wires so that we can send and receive signals for phone, television and computer networking. A signal is an electromagnetic or electrical current that carries data from one system or network to another.

Long before multiplexing, the first technology that provided fast communication across large distances almost instantly was the telegraph, and each communication signal traveled over a wire. As long as a signal was being sent through a wire, no other signal could go through that wire. So if 10 people wanted to send a message at 5:01 p.m., if there was only one wire, only one of them would be able to send the message at that time. In the late 1870s, each phone had its own wire. It was chaos as cities had thousands of wires strung across poles to accommodate each phone. Today, with all the various mediums and forms of technologies, were there not multiplexing in existence, cities would have millions of wires, or, cables, to transmit these signals for each of these.

Multiplexing allows multiple signals to travel over just one wire. With the rise of remote work during the COVID-19 pandemic and shift toward 5G telecommunications, organizations increasingly need to consolidate millions of signals. Fortunately, IT departments can use multiplexing to share lines as an effective and cost-efficient means for network engineers to build networks that transmit exceedingly higher volumes of data. 

Multiplexing is the sharing of a medium or bandwidth, and is the process in which multiple signals coming from multiple sources are combined and transmitted over a single communication line. This way, you don’t need a separate communication line for each different type of signal. A signal is an electric current or electromagnetic field used to convey data from one place to another. Multiplexing divides one link into multiple channels and is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link.

With the rise of remote work during the COVID-19 pandemic and the shift toward 5G telecommunications, organizations increasingly need to consolidate millions of signals. Fortunately, IT departments can use multiplexing as an effective and cost-efficient means for network engineers to build and manage networks that transmit exceedingly higher volumes of data. The ongoing digital transformation driving innovation in Web3 and the metaverse has also created a scramble for the in-demand skills of network engineers.

There are two ways to leverage multiplexing to transmit multiple signals at once. For example, the analog method uses frequency-division multiplexing. Digital and analog multiplexing provide different options depending on the medium, complexity, and other requirements.

What is Multiplexing?

Multiplexing, also known as muxing, is used by telecommunication and computing networks to send a large stream of information over a shared medium, such as a coaxial, metallic conductor or a wireless link. A signal is an electromagnetic or electrical current that carries data from one system or network to another.

 Multiplexing is a popular networking method because it divides channels into multiple logical channels. A logical channel is one that would be most suitable for transferring the type of data it carries. Each of the channels transfers a different message or data stream. The process of multiplexing divides a communication channel into several logical channels, allotting each one for a different message signal or a data stream to be transferred. This allows you to use your bandwidth to the fullest extent.

Multiplexing requires a device called a multiplexer, which combines multiple input lines into one output line through a conductor, such as a fiber optic cable or a copper wire.

The process of multiplexing, whether digital or analog, consolidates various signals into one composite signal to transmit over a common medium, for instance, radio waves or fiber optic cable. Once it reaches the destination, the process of demultiplexing, or demuxing, separates the signals to transmit through individual lines. Demultiplexing then restores the respective signals to boost the load for processing.

Although multiplexing uses numerous techniques, they all operate on the same conceptual level. Typically, there are two primary reasons why organizations implement multiplexing on their networks:

  • To allow devices to communicate with one another without requiring a dedicated transmission path.
  • To use expensive or scarce network resources more efficiently
  • Cable or fiber strands running between major metropolitan areas, for example, use multiplexing to improve efficiency.

Organizations that need to use scarce IT resources or improve their bandwidth need to know when to use multiplexing in networking.

The Two Types of Multiplexing

Organizations can choose from various forms of multiplexing. The form that works best depends on several factors, such as the type of signal they need to transmit — digital or analog — and the medium they’re using, such as a microwave link, fiber optic cable, or coaxial cable.

There are mainly two types of multiplexers: analog and digital.  If the analog signals are multiplexed, then it is called as analog multiplexing. If the digital signals are multiplexed, then it is called digital multiplexing.

1. Analog Multiplexing

Analog multiplexing is typically used for telecommunications. Telephones and televisions are examples of technologies that process analog signals. Analog forms of multiplex use either Frequency Division Multiplexing (FDM) or Wavelength Division Multiplexing (WDM).

FDM is the most popular analog multiplexing technique. It involves combining different frequencies to join data streams to send them as a single signal. The collection of single-frequency signals is referred to as carriers.

WDM, a less common form of analog multiplexing, multiplexes a number of optical carrier signals onto a single optical fiber by using different colors of laser light to send various data streams at different wavelengths. WDM is most commonly used in high-capacity communication networks. Optical fibers join various wavelengths into one light for communicating.

2. Digital Multiplexing

Digital multiplexing is used in computer networking to help organizations send multiple signals over a single channel. A digital channel may be used to transmit data, but if that channel gets too much data pushed through it at one time, it could cause the system to crash. By using the available bandwidth of other communication channels through time-division multiplexing, rather than overflowing one particular channel, IT departments prevent crashes.

Digital telephony primarily utilizes Time-Division Multiplexing (TDM) to send multiple data streams, or messages, in a single communication path. TDM is based signals being transmitted in tiny increments of time. TDM is split into two separate categories: synchronous and asynchronous. 

In Synchronous TDM, there are a set number of connections that divide the frame into that many time slots. Each time slot runs for an equal amount of time the network engineer has programed each slot to run, usually about a millisecond. There are an equal number of devices to time slots. The transmission of the devices’ messages continually run in round robin fashion for their allotted millisecond. If a device doesn’t have data for a particular time slot, the empty slot will be transmitted and no message will be received. This could potentially waste slots if certain connections often don’t have data to transmit or receive. The most popular forms of Synchronous TDM are SONET multiplexing, T-1 multiplexing, and ISDN multiplexing.

Asynchronous TDM, sometimes called Statistical TDM, uses a technique in which time slots aren’t fixed. Time slots are only allocated to those devices that have data to send. If one device has nothing to transmit  then that space can be allotted to another device.  That means all the slots can be fully utilized, unlike Synchronous TDM. However, while Asynchronous TDM does more effectively use slots than Synchronous TDM, it is more challenging to provide service guarantees because it varies based on current usage.

Build Efficient Networks at Scale

Multiplexing is critical for maintaining bandwidth, preventing system crashes, and improving internal communication. Although developed initially for analog telecommunications, it is now used more often for digital applications. Multiplexing improves how we transmit information, especially as digital communication and computer networks are increasingly becoming critical for remote teams.

There are a variety of multiplexing techniques that can enable efficient and effective networking. Although broadly divided into analog and digital types, organizations can choose from multiple methods within these two types of multiplexing to create the ideal network.

With the increasing prominence of multiplexing in business, IT professionals benefit from enrolling in networking training courses to learn the latest in-demand skills. ExitCertified offers vendor-certified IT training courses in leading technologies.

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