A simple soft decision method for the 2-circular 16QAM constellation

For high data rate transmission, high dimensional modulation is becoming one of the preferred choice in the future mobile communication, while the much more signal amplitudes have become one of the barriers to implement AGC and A/D transfer, and also result in the heavy performance degradation in the time-varying channel for CDMA systems. In this paper, the 2-circular 16QAM constellation and it´s soft decision method will be studied. From the point of view of decision region for every bit, the maximum minimal decision region criteria for the 2-circular 16QAM constellation is presented and the corresponding simple soft decision method are also introduced. 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, compared with the other soft decision method, the proposed soft decision method has better performance while it performs more simply.