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Amplitude and phase-shift keying or asymmetric phase-shift keying (APSK), is a digital modulation scheme that conveys data by changing, or modulating, both the amplitude and the phase of a reference signal (the carrier wave). In other words, it combines both Amplitude-shift keying (ASK) and Phase-shift keying (PSK) to increase the symbol-set. It can be considered as a superclass of Quadrature amplitude modulation (QAM). The advantage over conventional QAM, for example 16-QAM, is lower number of possible amplitude levels.

Moreover, a careful design of the constellation geometry enables to approach the Gaussian capacity when the constellation size grows to infinity. For the regular QAM constellations, a gap of 1.56 dB is observed. The previous solution, where the constellation has a Gaussian shape, is called constellation shaping.

References

DVB-Flexible Serially Concatenated Convolutional Turbo Codes with Near-Shannon bound performance for telemetry applications, CCSDS-131.2-O-1.
H. Méric, Approaching The Gaussian Channel Capacity With APSK Constellations, IEEE Communications Letters.

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 {{Refimprove|date=August 2008}}
 {{Modulation techniques}}
- '''Amplitude and phase-shift keying''' or '''asymmetric phase-shift keying''' ('''APSK'''), is a [[Digital data|digital]] [[modulation]] scheme that conveys [[Data#Uses of data in computing|data]] by changing, or modulating, both  the [[amplitude]] and the [[Phase (waves)|phase]] of a reference [[Signal (information theory)|signal]] (the [[carrier wave]]). In other words, it combines both [[Amplitude-shift keying]] (ASK) and [[Phase-shift keying]] (PSK) to increase the [[Symbol (data)|symbol-set]]. It can be considered as a superclass of [[Quadrature amplitude modulation]] (QAM). The advantage over conventional QAM, for example 16-QAM, is lower number of possible amplitude levels.
+'''Amplitude and phase-shift keying''' or '''asymmetric phase-shift keying''' ('''APSK'''), is a [[Digital data|digital]] [[modulation]] scheme that conveys [[Data#Uses of data in computing|data]] by changing, or modulating, both  the [[amplitude]] and the [[Phase (waves)|phase]] of a reference [[Signal (information theory)|signal]] (the [[carrier wave]]). In other words, it combines both [[Amplitude-shift keying]] (ASK) and [[Phase-shift keying]] (PSK) to increase the [[Symbol (data)|symbol-set]]. It can be considered as a superclass of [[Quadrature amplitude modulation]] (QAM). The advantage over conventional QAM, for example 16-QAM, is lower number of possible amplitude levels.
 Moreover, a careful design of the constellation geometry enables to approach the Gaussian capacity when the constellation size grows to infinity. For the regular QAM constellations, a gap of 1.56 dB is observed. The previous solution, where the constellation has a Gaussian shape, is called constellation shaping.
 ==References==
-* [http://www.ebu.ch/en/technical/trev/trev_300-morello.pdf DVB-Flexible Serially Concatenated Convolutional Turbo Codes with Near-Shannon bound performance for telemetry applications ], [[CCSDS]]-131.2-O-1.
+* [http://www.ebu.ch/en/technical/trev/trev_300-morello.pdf DVB-Flexible Serially Concatenated Convolutional Turbo Codes with Near-Shannon bound performance for telemetry applications], [[CCSDS]]-131.2-O-1.
 *H. Méric, [http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=7105353&newsearch=true&queryText=%20Approaching%20the%20Gaussian%20channel%20capacity%20with%20APSK%20constellations Approaching The Gaussian Channel Capacity With APSK Constellations], ''IEEE Communications Letters''.