Optimal 2-Circular 16QAM constellation design

For high data rate transmission, high dimensional modulation is becoming one of preferred choice in the future mobile communication, while the much more signal amplitudes also have become one of the barriers to implement AGC and A/D transfer for the CDMA systems. Compared with the rectangular QAM constellation, the circular QAM constellation has fewer kinds of amplitude, which may be of great benefit to the problem above. In this paper, the 2-Circular 16QAM constellation will be studied. From the point of view of decision region for every bit, the optimal design criteria for the 2-Circular 16QAM constellation, namely maximal minimum decision region criteria, is presented and verified by reduction to absurdity. Simulations are done in the LAS/CDMA system with turbo code over AWGN channel. The results indicate that the 2-Circular 16QAM constellation under the proposed design criteria has the best BER performance. What's more, under the same average transmit power the proposed constellation has fewer amplitude dynamic range.