Definition: Coherence bandwidth is a statistical measure 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 W_c in hertz is given approximately by the equation: Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... Amplitude is a nonnegative scalar measure of a waves magnitude of oscillation, that is, magnitude of the maximum disturbance in the medium during one wave cycle. ... Look up second in Wiktionary, the free dictionary. ... The hertz (symbol: Hz) is the SI unit of frequency. ...

The coherence bandwidth varies over cellular or PCS communications paths because the multipath spread D varies from path to path. Cellular redirects here. ...

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 W_c 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. General Information Generically (as a multiplexing scheme), code division multiple access (CDMA) is any use of any form of spread spectrum by multiple transmitters to send to the same receiver on the same frequency channel at the same time without harmful interference. ... MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ...

Example: If the delay spread D over a particular cellular communication path in an urban environment is 3 µs, then using equation above, the coherence bandwidth is approximately 53 kHz, which is only about 4.2% of the IS-95 bandwidth. A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ...