- Amplitude and phase-shift keying
Amplitude and Phase-shift keying or Asymmetric Phase-shift keying, (APSK), is a
digital modulation scheme that conveys data by changing, or modulating, both theamplitude and the phase of a reference signal (thecarrier wave ). In other words, it combines bothAmplitude-shift keying (ASK) andPhase-shift keying (PSK) to increase the symbol-set. It can be considered as a subclass ofQuadrature amplitude modulation (QAM). The advantage over conventional QAM, for example 16-QAM, is lower number of possible amplitude levels, resulting in less problems with non-linear amplifiers.Applications
The
DVB-S2 specification permits the use of16APSK and32APSK modes, allowing 16 and 32 different symbols respectively and are intended for mainly professional, semi-linear applications. They can be also used for broadcasting but they require a higher level of available C/N and an adoption of advanced pre-distortion methods in the uplink station in order to minimize the effect of transponder non-linearity.Figure - Bit mapping into constellations - (see Ref.2)
References
* [http://www.ebu.ch/en/technical/trev/trev_300-morello.pdf DVB-S2 — ready for lift off] , article in the EBU technical review
* [http://public.ccsds.org/publications/archive/131x2o1.pdf Flexible Serially Concatenated Convolutional Turbo Codes with Near-Shannon bound performance for telemtery applications ] ,
CCSDS -131.2-O-1.
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