具有低复杂度的LDPC已编码非相干酉空时调制系统设计

LDPC-coded unitary space-time modulation with low-complexity iterative demodulate-decoding scheme

提出一种克服无线信道瑞利衰落和高斯白噪声干扰的非相干编码调制MIMO系统方案。纠错码采用IEEE802．16e中的非规则QC-LDPC码，非相干调制采用基于三角函数的酉空时调制（SC．USTM）。在接收端，推导出SC-USTM的最大后验概率（MAP）解调算法；为了降低复杂度，构造了SC-USTM的双解调器方案；为了改善双解调的性能，在置信传播（BP）迭代解码器和MAP解调器之间引入了迭代反馈机制。仿真实验表明LDPC己编码SC-USTM的MIMO系统比未编码USTM的MIMO系统在10-5误码率时，性能改善15～17dB，并且整个系统具有较低的计算复杂度。

A practical low-density parity-check（LDPC） coded unitary space-time modulation （USTM） noncoherent MIMO communication system over Rayleigh flat fading and additive white Gaussian noise （AWGN） channel was con- structed, where the LDPC code is selected from IEEE 802.16e Standard and USTM is constructed by the unitary matrix based on the sinc-cosinc function, SC-USTM for short. At the receiver, the maximum a posteriori probability （MAP） de- modulating algorithm of the SC-USTM was first designed; for reducing the complexity of MAP demodulator, the dual demodulator was then conceived; for improving the performance, the iterative feedback between the belief propagation （BP） decoder and the MPA demodulator was finally introduced. The simulation test shows that the system of the LDPC coded SC-USTM is superior to the uncoded SC-USTM about 15-17 dB at BER10-5 , and this system has very low complexity.