The portion of the signal bandwidth over which fading does not occur typically contains enough signal power to sustain reliable communications. Therefore, when fading occurs it occurs only over a relatively small fraction of the total CDMA signal bandwidth. 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 B c is significantly less than 1.25 MHz. The coherence bandwidth varies over cellular or PCS communications paths because the multipath spread D varies from path to path.įrequencies within a coherence bandwidth of one another tend to all fade in a similar or correlated fashion. It can be reasonably assumed that the channel is flat if the coherence bandwidth is greater than the data signal bandwidth. If the multipath time delay spread equals D seconds, then the coherence bandwidth W c JSTOR ( May 2009) ( Learn how and when to remove this template message)Ĭoherence 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.Unsourced material may be challenged and removed.įind sources: "Coherence bandwidth" – news Please help improve this article by adding citations to reliable sources.
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