Attenuation and Amplification

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In computer networking, attenuation is a loss of communication signal strength measured in decibels (dB). One of the methods used to increase signal strength to prevent attenuation issues is amplification.

Attenuation Demystified

Attenuation occurs on computer networks for several reasons:

  • Range - both wireless and wired transmissions gradually dissipate in strength over longer reaches
  • Interference - on wireless networks, radio interference or physical obstructions like walls also dampen communication signals
  • Wire size - on wired networks, thinner wires suffer from higher (more) attenuation than thicker wires

On DSL networks, line attenuation measures signal loss between the home and the DSL provider's access point (central exchange). Attenuation becomes especially important on DSL networks as the data rates a given household can obtain may be restricted if the line attenuation values are too large. Typical values for line attenuation on a DSL connection are between 5 dB and 50 dB (lower values are better). Some broadband routers display these line attenuation values on their console pages, although they tend to be of interest only to advanced network administrators when troubleshooting connection problems

Wi-Fi supports a feature called dynamic rate scaling that automatically adjusts the maximum data rate of the connection up or down in fixed increments depending on the line's transmission quality. In high attenuation scenarios, a 54 Mbps connection can de-rate down as low as 6 Mbps, for example.

The word "attenuation" sometimes applies in other environments besides computer networks. For example, audiophiles and professional sound mixers may use attenuation techniques to manage sound levels when blending different audio recordings together.

Amplification Demystified

Signal amplification works in opposition to signal attenuation, electrically increasing the strength of a line signal by any of several technical methods. Different forms of amplification introduce more or less noise into the signal. On computer networks, amplification typically includes logic for noise reduction to ensure the underlying message data does not get corrupted in the process.

Network repeater devices typically integrate a signal amplifier into their circuitry. The repeater works as an intermediate between two message endpoints. It receives data from the original sender (or another upstream repeater), processes it through the amplifier, and then transmits the stronger signal forward to its eventual destination.

So-called signal boosters help amplify wireless signals being received. Besides repeaters, directional antennas and other antenna upgrades work well as boosters.

A separate concept from signal amplification, DNS amplification is a kind of Distributed Denial of Service (DDoS) attack where a malicious attacker or a botnet uses the Domain Name System (DNS) to flood a target server with bogus message data. Amplification, in this case, refers to the behavior of DNS in responding to relatively small request messages by sending relatively large amounts of response data.

The term privacy amplification (separate from both signal and DNS amplification) refers to an advanced concept in computer network security and information theory where two parties can work together to mutually figure out the value of a secret key.

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