引入Star-QAM的高码率差分酉空时编码调制

随着码率的不断增加,酉空时码群中的各个星座点之间的乘积距离会变得越来越小,从而导致性能恶化.为了改变这一特点,引入了Star-QAM(Quadrature Amplitude Modulation)星座图.与M-PSK(MultiplePhase Shift Keying)的一个重要区别就是,Star-QAM星座图的每个信号星座点都具有不同的能量,即具有多幅度特征,不同的星座点可位于多个不同半径的圆上,从而增加了幅度自由度.可根据不同情况找到最优的内外半径比,进而提高整个系统的性能.仿真结果表明,在BER(Bit Error Rate)为10-3时,改进的差分酉码调制的性能比传统的好2.3 dB,而在BER为10-2时,改进方案的性能要好1.8 dB.

Differential Unitary Space-Time Modulation with High Code Rate Based on Star-QAM

With the increase of the code rate, the production distance between the constellation of the unitary group code decreases rapidly and deteriorates the performance of the system. In order to improve its performance,we introduce the idea of Star-QAM ( Quadrature Amplitude Modulation) into the conventional unitary space-time modulation, Star-QAM is distinct from M-PSK ( Multiple-Phase Shift Keying) for every constellation point having different energy, that is, Star-QAM has the character of multiple amplitude, and its constellation points can be located in circles with different radius. So the freedom of amplitude is increased. We can find the optimum radius ratio of the inner circle and the outer circle according to different condition, and improve the performance of the system. According to the simulation, the proposed method will perform 2.3 dB better than conventional method at BER ( Bit Error Rate) RBER = 10 -3 and even can outperform 1.8 dB at RBER = 10 -2.