(4,12)-CIRCULAR-SIGNAL-SET CONSTELLATION FOR 16APSK AND ITS PERFORMANCE

A (4,12) circular-signal-set constellation (the (4, 12) QAM) that has 4 signals on the inner ring and 12 signals on the outer ring has been proposed for 16APSK;. This constellation shows good performance over a n AWGN channel using the coherent detection scheme and also can be ada pted to the differential detection scheme for the phase part. In addit ion, the multiple-symbol differential detection scheme based on the MA P criterion is a good choice for the amplitude part to improve the per formance over a fading channel, since the differential detection schem e cannot be applied to the amplitude part of the (4,12) QAM. In this p aper, we show its performance by using envelope amplitude/coherent pha se detection over an AWGN channel and compare it with other constellat ions, particularly with the star QAM. Next, we construct the decision rule of the multiple-symbol differential detection for the amplitude p art and show that the coefficient that is related to the a priori prob ability in view of the signal constellation is influential in estimati ng amplitude sequences. The performance with the sequence length equal to 6 is close to that of the envelope amplitude detection, and we als o confirm its performance over a Rayleigh fading channel by computer s imulation. (C) 1998 Scripta Technica.