Definition

attenuation

Contributor(s): Linda Rosencrance

Attenuation is a general term that refers to any reduction in the strength of a signal. Attenuation occurs with any type of signal, whether digital or analog. Sometimes called loss, attenuation is a natural consequence of signal transmission over long distances.

In conventional and fiber optic cables, attenuation is specified in terms of the number of decibels per foot, 1,000 feet, kilometer, or mile. The less the attenuation per unit distance, the more efficient the cable.

When it is necessary to transmit signals over long distances via cable, one or more repeaters can be inserted along the length of the cable. The repeaters boost the signal strength to overcome attenuation. This greatly increases the maximum attainable range of communication.

Attenuation in networking

Attenuation in computer networking is the loss of communication signal strength that is measured in decibels (dB). As the rate of attenuation increases, the transmission, such as an email a user is trying to send or a phone call, becomes more distorted.

Attenuation occurs on computer networks because of:

  • Range – over longer distances both wired and wireless transmissions gradually dissipate in strength
  • Interference – radio interference or physical obstructions, such as walls, dampen communication signals on wireless networks
  • Wire size – thinner wires suffer from more attenuation than thicker wires on wired networks

Line attenuation on a digital subscriber line (DSL) network measures signal loss between a DSL provider’s access point and a home, for example. Attenuation is critical on DSL networks because if the line attenuation values are too large, the data rates a household can obtain may be restricted. Values for line attenuation on a DSL connection are typically between 5 dB and 50 dB – the lower the values, the better.

Wi-Fi supports what’s called dynamic rate scaling that enhances the distance at which wireless devices can connect to each other in exchange for lower network performance at the longer distances. Depending on the transmission quality of the line, dynamic rate scaling automatically regulates the connection’s maximum data rate up or down in fixed increments.

Attenuation in other contexts

The word “attenuation” is also used in contexts other than computer networking. For instance, sound mixers and audiophiles may use attenuation techniques to manage sound levels when they blend together different audio recordings.

Attenuation is also frequently used in the radiology field to discuss the characteristics of an anatomical structure represented in an X-ray.

In brewing, attenuation refers to the process of converting sugars into alcohol and carbon dioxide by fermentation. The greater the attenuation, the more sugar has been converted into alcohol. If a beer is more attenuated, then it is drier and more alcoholic than a beer that is less attenuated.

The importance of attenuation

Attenuation is important in telecommunications and ultrasound applications because it’s critical to determining signal strength as a function of distance. Minimizing the loss of attenuation is important in microwave, wireless and cellular applications because to function correctly an optical data link depends on modulated light reaching the receiver with enough power to be correctly demodulated. This power is reduced through attenuation, resulting in a loss of the light signal that’s being transmitted.

How to measure attenuation

The extent of attenuation is usually expressed in units called decibels (dBs).

If Ps is the signal power at the transmitting end (source) of a communications circuit and Pd is the signal power at the receiving end (destination), then Ps > Pd. The power attenuation Ap in decibels is given by the formula:

Ap = 10 log10(Ps/Pd)

Attenuation can also be expressed in terms of voltage. If Av is the voltage attenuation in decibels, Vs is the source signal voltage, and Vdis the destination signal voltage, then:

Av = 20 log10(Vs/Vd)

How to increase signal strength to prevent attenuation

One of the techniques that can be used to increase signal strength to prevent attenuation is amplification.

Signal amplification electrically increasing the strength of a line signal by one of several technical methods. Typically, on computer networks, amplification includes logic for noise reduction to prevent the underlying message data from becoming corrupted in the process.

A network repeater device integrates a signal amplifier into its circuitry, acting as an intermediary between two message endpoints. The repeater receives data from the original sender (or other upstream repeater), processes it through the amplifier then transmits the stronger signal forward to its ultimate destination. In addition to repeaters, directional antennas and other antenna upgrades also work well to boost signals.

This was last updated in June 2019

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