Editing Quadrature amplitude modulation (section)

== Interference and noise ==

In moving to a higher order QAM constellation (higher data rate and mode) in hostile [[RF]]/[[microwave]] QAM application environments, such as in [[broadcasting]] or [[telecommunications]], [[multipath interference]] typically increases. There is a spreading of the spots in the constellation, decreasing the separation between adjacent states, making it difficult for the receiver to decode the signal appropriately. In other words, there is reduced [[Noise#Electronic noise|noise]] immunity. There are several test parameter measurements which help determine an optimal QAM mode for a specific operating environment. The following three are most significant:<ref>{{cite web| title = Hitless Space Diversity STL Enables IP+Audio in Narrow STL Bands| url = http://www.moseleysb.com/mb/whitepapers/friedenberg.pdf| work = 2005 National Association of Broadcasters Annual Convention| author = Howard Friedenberg and Sunil Naik| access-date = April 17, 2005| archive-url = https://web.archive.org/web/20060323141431/http://www.moseleysb.com/mb/whitepapers/friedenberg.pdf| archive-date = March 23, 2006| url-status = dead}}</ref>
* [[Carrier signal|Carrier]]/interference ratio
* [[Carrier-to-noise ratio]]
* Threshold-to-noise ratio