Abstract
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 an AWGN channel using the coherent detection scheme and also can be adapted to the differential detection scheme for the phase part. In addition, the multiple-symbol differential detection scheme based on the MAP criterion is a good choice for the amplitude part to improve the performance over a fading channel, since the differential detection scheme cannot be applied to the amplitude part of the (4,12) QAM. In this paper, we show its performance by using envelope amplitude/coherent phase detection over an AWGN channel and compare it with other constellations, particularly with the star QAM. Next, we construct the decision rule of the multiple-symbol differential detection for the amplitude part and show that the coefficient that is related to the a priori probability in view of the signal constellation is influential in estimating amplitude sequences. The performance with the sequence length equal to 6 is close to that of the envelope amplitude detection, and we also confirm its performance over a Rayleigh fading channel by computer simulation. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 81(9): 1–9, 1998
Published Version
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