Optimization of signal constellations with amplitude-phase shift keying in communication channels with non-fluctuating interference

Objectives. Multi-position amplitude-phase shift keying (APSK) with a ring-shaped signal constellation is one of the most effective ways for transmitting discrete information in satellite systems. The use of APSK is regulated by several standards. The main are DVB-S2 and VSAT which define both the modulation parameters, and the parameters of the signal constellations. The aim of the paper is to determine the best constellations of 16-APSK and 32-APSK, and provide a minimum BER for cases when the communication channel, along with noise, contains non-fluctuating interference. Methods. Methods of statistical radio engineering, the theory of optimal signal reception, and computer modeling were used. Results. The optimization of ring-shaped constellations of 16-APSK and 32-APSK signals is attained by changing the distribution of points along the radius and phase for a case in which the communication channel, along with noise, contains non-fluctuating interference: frequency-shift keyed, retransmitted, phase-shift keyed, and harmonic ones. The best constellations of 16-APSK and 32-APSK are determined, and a minimum bit error rate is provided. Conclusions. In order to improve the quality of communication in information transmission systems in the presence of non-fluctuating interference, the existing constellations 16-APSK (4, 12) and 32-APSK (4, 12, 16) can be used by changing the ratios between the radii of circles 2.5 for 16-APSK and 2.5/3.9 for 32-APSK. Due to the more efficient use of signal power, the use of constellations with a zero-amplitude point for 16-APSK allows reception noise immunity to be increased. For example, when using constellation (1, 5, 10), the energy gain compared to the standard constellation (4, 12) can reach 1 dB.