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16APSK modulation is used in the DVB-SH standard, in the satellite transmission mode (mode SH-B). The signal constellation for 16APSK is shown in the figure below.
One important parameter of the 16APSK modulation is the radio of the radii of the two concentric circles where the constellation points are located. The radius ratio parameter is selected based on the code rate used in the system. The values below show the optimum values of the radius ratio for each of the code rates used in the DVB-SH standard.
Code RateModulation spectral efficiencyRadius ratio2/32.663.153/42.992.855/63.322.708/93.552.609/103.592.57
The signal constellation is calculated in the Global Definitions window and then used in QAM_TX blocks to map and modulate a bit stream. QAM_TX allows the user to define any of the available pulse shapes, which are needed in real-world communication systems. A QAM_RX block is used to perform matched filtering and demodulate the 16APSK signal.