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-Quadrature amplitude modulation (QAM) is a highly developed modulation scheme used in the communication industry in which data is transmitted over radio frequencies. For wireless communications, QAM is a signal in which two carriers (two sinusoidal waves) shifted in phase by 90 degrees (a quarter out of phase) are modulated and the resultant output consists of both amplitude and phase variations. These variations form the basis for the transmitted binary bits, atoms of the digital world, that results in the information we see on our devices.

By varying these sinusoidal waves through phase and amplitude, radio engineers can construct signals that transmit an ever-higher number of bits per hertz (information per signal). Systems designed to maximize spectral efficiency care a great deal about bits/hertz efficiency and thus are always employing techniques to construct ever denser QAM constellations to increase data rates. Put simply, higher QAM levelsincrease throughput capabilities in wireless devices. By varying the amplitude of the signal as well as the phase, Wi-Fi radios are able toconstruct the following constellation diagram that shows the values associated with the different states for a 16 QAM signal.

- 16-QAM constellation example


While the older Wi-Fi 5 (802.11ac) standard is limited to 256-QAM, the new Wi-Fi 6 (802.11ax) standard incorporates an extremely high optional modulation scheme (1024-QAM), with each symbol (a point on the constellation diagram) encoding a larger number of data bits when using a dense constellation. In real-world terms, 1024-QAM enables a 25% data rate increase (throughput) in Wi-Fi 6 (802.11ax) access points and devices. With over 30 billion connected “things” expected by 2020, higher wireless throughput facilitated by 1024-QAM is critical to ensuring quality-of-service (QoS) in high-density locations such as
stadiums, convention centers, transportation hubs, and auditoriums. Indeed, applications such as 4K video streaming (which is becoming the norm) are expected to drive internet traffic to 278,108 petabytes per month by 2021.