Multiplexer

What Does Multiplexer Mean?

A multiplexer (MUX) is a network device that allows one or more analog or digital input signals to travel together over the same communications transmission link. The purpose of multiplexing is to combine and transmit signals over a single shared medium in order to optimize efficiency and decrease the total cost of communication.

Essentially, a MUX functions as a multiple-input, single-output switch that allows multiple analog and digital input signals and to be routed through a single output line. At the receiving end, another device called a demultiplexer recovers the original individual signals.

Techopedia Explains Multiplexer

Multiplexing techniques have become useful network optimization tools during the age of the Internet of Things, edge computing and 5G. It’s important to note, however, that multiplexing itself is quite old in terms of post-industrial technologies. In its earliest forms, multiplexing can be traced back to the 1800s and when it was first used to optimize legacy communication channels like the telegraph and radio.

Today, the following communication applications would be prohibitively expensive without multiplexing: telecom, satellites, telemetry and broadcasting.

Types of Multiplexing

Types of multiplexing technologies and processes include, but are not limited to:

• Time Division Multiplexing (TDM) – incoming signals are divided into equal fixed-length time slots.
• Inverse Multiplexing (IMUX) – breaks the combined signals into several concurrent lower-speed related signals or data streams.
• Wavelength Division Multiplexing (WDM) – allows multiple optical carrier signals to be transmitted through a single optical fiber. Each wavelength of light carries a different signal.
• Dense Wavelength Division Multiplexing (DWDM) – combines and transmits multiple signals simultaneously at different wavelength on the same fiber.
• Frequency Division Multiplexing (FDM) – each data stream uses a carrier signal at a discrete frequency.
• Orthogonal Frequency Division Multiplexing (OFDM) – makes use of a large number of closely spaced orthogonal subcarriers that are transmitted in parallel.
• Add/Drop Multiplexing (ADM) – can drop or remove low-bandwidth signals from the data stream and direct them to other network routes.

How Multiplexing Works

Today, frequency division multiplexing, time division multiplexing and wavelength division multiplexing are the types of multiplexing most closely associated with telecom.

For analog signals in telecommunications and signal processing, a time division multiplexer may select multiple samples of separate analog signals and combine them into one pulse amplitude modulated (PAM) wide-band analog signal. When there are two input signals and one output signal, a MUX is referred to as a 2-to-1 multiplexer; with four input signals it is a 4-to-1 multiplexer — and so on.

For digital signals in telecommunications on a computer network or with digital video, several variable bit-rate data streams of input signals (using packet mode communication) may be combined, or multiplexed, into one constant bandwidth signal. With an alternate method utilizing a TDM, a limited number of constant bit-rate data streams of input signals may be multiplexed into one higher bit-rate data stream.

A multiplexer requires a demultiplexer to complete the process, to separate multiplex signals carried by the single shared medium or device. Often a multiplexer and a demultiplexer are combined into a single device (also often just called a multiplexer) in order to allow the device to process both incoming and outgoing signals.

Alternately, a multiplexer’s single output may be connected to a demultiplexer’s single input over a single channel. Either method is often used as a cost-saving measure. Since most communication systems transmit in both directions, the single combined device, or two separate devices (as in the latter example), will be needed at both ends of the transmission line.

The Future of Multiplexing

One of the most fascinating new applications of multiplexing is to new communications paradigms like 5G, in which different hardware and setup capacities provide for different types of signal transfer. For example, waveform multiplexing for 5G involves partial and full connectivity designs that use sub-arrays connected to radiofrequency chains to optimize this type of multiple signal transmission.

Experts describe the use of small cell technologies offering wideband and multi-gigabyte rates for supporting data intensive activities like HDTV and wireless gaming. Digital beamforming architecture, they note, can be useful in downlink transmitters and other aspects of mobile applications.

In general, the future of multiplexing is tightly coupled with the types of connectivity that allow more diverse traffic on a given hardware system. For instance, virtual local area networks or VLANs are setups where a physical LANs, comprised of different hardware pieces, can carry more than one bandwidth trajectory across the network. So signals meant for different components are moving in the same lines, and effectively handled with virtualization schemes.

Multiplexing is similar in that it promotes the ability to transfer data coming from different pairs of equipment, in a kind of tunnel system where the multiplexer and demultiplexer complement each other.

Essentially, the idea of multiplexing is inherent in trying to find efficiencies for telecom or similar systems using a “pipeline” for communications. This type of traffic control is behind enormous advances in communications technology throughout the last several decades.