For faster navigation, this Iframe is preloading the Wikiwand page for Coherence bandwidth.

Coherence bandwidth

This article does not cite any sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.Find sources: "Coherence bandwidth" – news · newspapers · books · scholar · JSTOR (May 2009) (Learn how and when to remove this message)

Coherence bandwidth is a statistical measurement of the range of frequencies over which the channel can be considered "flat", or in other words the approximate maximum bandwidth or frequency interval over which two frequencies of a signal are likely to experience comparable or correlated amplitude fading. If the multipath time delay spread equals D seconds, then the coherence bandwidth in rad/s is given approximately by the equation:

Also coherence bandwidth in Hz is given approximately by the equation:

It can be reasonably assumed that the channel is flat if the coherence bandwidth is greater than the data signal bandwidth. The coherence bandwidth varies over cellular or PCS communications paths because the multipath spread D varies from path to path.

Application

Frequencies within a coherence bandwidth of one another tend to all fade in a similar or correlated fashion. One reason for designing the CDMA IS-95 waveform with a bandwidth of approximately 1.25 MHz is because in many urban signaling environments the coherence bandwidth Bc is significantly less than 1.25 MHz. Therefore, when fading occurs it occurs only over a relatively small fraction of the total CDMA signal bandwidth. The portion of the signal bandwidth over which fading does not occur typically contains enough signal power to sustain reliable communications. This is the bandwidth over which the channel transfer function remains virtually constant.

Example

If the delay spread D over a particular cellular communication path in an urban environment is 1.9 μs, then using equation above, the coherence bandwidth is approximately 0.53 MHz, which results in frequency selective fading over the IS-95 bandwidth.

See also

References

{{bottomLinkPreText}} {{bottomLinkText}}
Coherence bandwidth
Listen to this article

This browser is not supported by Wikiwand :(
Wikiwand requires a browser with modern capabilities in order to provide you with the best reading experience.
Please download and use one of the following browsers:

This article was just edited, click to reload
This article has been deleted on Wikipedia (Why?)

Back to homepage

Please click Add in the dialog above
Please click Allow in the top-left corner,
then click Install Now in the dialog
Please click Open in the download dialog,
then click Install
Please click the "Downloads" icon in the Safari toolbar, open the first download in the list,
then click Install
{{::$root.activation.text}}

Install Wikiwand

Install on Chrome Install on Firefox
Don't forget to rate us

Tell your friends about Wikiwand!

Gmail Facebook Twitter Link

Enjoying Wikiwand?

Tell your friends and spread the love:
Share on Gmail Share on Facebook Share on Twitter Share on Buffer

Our magic isn't perfect

You can help our automatic cover photo selection by reporting an unsuitable photo.

This photo is visually disturbing This photo is not a good choice

Thank you for helping!


Your input will affect cover photo selection, along with input from other users.

X

Get ready for Wikiwand 2.0 ๐ŸŽ‰! the new version arrives on September 1st! Don't want to wait?