Editing Fading (section)

===Block fading===
'''Block fading''' is where the fading process is approximately constant for a number of symbol intervals.<ref>{{cite book |last1=Biglieri |first1=Ezio |last2=Caire |first2=Giuseppe |author2-link=Giuseppe Caire |last3=Taricco |first3=Giorgio |chapter=Coding for the Fading Channel: a Survey |editor1-last=Byrnes |editor1-first=Jim S. |title=Signal Processing for Multimedia |date=1999 |publisher=IOS Press |page=253 |isbn=978-90-5199-460-5 }}</ref> A channel can be 'doubly block-fading' when it is block fading in both the time and frequency domains.<ref>{{cite conference
|url = https://www.mit.edu/~medard/manndd1.pdf
|title = Spreading in block-fading channels
|last1 = Médard
|first1 = Muriel |author1-link=Muriel Médard
|first2 = David N. C.
|last2 = Tse
|conference = 34th Asilomar Conference on Signals, Systems and Computers, Oct 29 – Nov 1, 2000, Pacific Grove, CA, USA
|volume = 2
|book-title = Conference Record of the Thirty-Fourth Asilomar Conference on Signals, Systems and Computers
|pages = 1598–1602
|isbn = 0-7803-6514-3
|doi = 10.1109/ACSSC.2000.911259
|access-date = 2014-10-20
}}</ref> Many wireless communications channels are dynamic by nature, and are commonly modeled as block fading. In these channels each block of symbol goes through a statistically independent transformation. Typically the slowly-varying channels based on jakes model of Rayleigh spectrum <ref>{{Cite journal |last=Sklar |first=Bernard |date=July 1997 |title=Rayleigh fading channels in mobile digital communication systems .I. Characterization |url=https://ieeexplore.ieee.org/document/601747 |journal=IEEE Communications Magazine |volume=35 |issue=7 |pages=90–100 |doi=10.1109/35.601747 }}</ref> is used for block fading in an [[Orthogonal frequency-division multiplexing|OFDM]] system.