一种改进的差分酉空时编码技术

差分酉空时码不需要任何信道状态信息，在通信终端处于高速移动环境下的快变衰落信道中仍能保持较好的性能。传统的差分酉空时码仅考虑了单电平发射功率，限制了高信噪比时性能的提高。通过在码字内引入多电平相位因子，提出了一种两发射天线以上的多电平差分酉空时码星座构造方案，扩大了码字之间的最小距离，提高了星座的分集乘积。仿真结果表明在译码复杂度略高的情况下改进方案的性能比传统差分酉空码有明显的改善。

An improved differential unitary space-time coding technique

Differential unitary space-time code(DUSTC) keeps good performance in rapidly fading channels when neither the transmitter nor the receiver knows the channel state information.The traditional DUSTC code considers but one level of amplitude,which may degrade the performance of codes when the signal-to-noise ratio is high.This paper proposes a new DUSTC through relaxing this constraint to allow the information symbols to have multiple amplitude levels.The minimal distance between constellations can be enlarged and the constellation diversity product is enhanced.The simulation results demonstrate that the improved DUSTC outperforms the traditional DUSTC.