Considering that channel estimation can play a crucial role in coherent detection of the information symbols in each data block, a blind channel estimation approach is proposed for redundant precoded orthogonal freque...Considering that channel estimation can play a crucial role in coherent detection of the information symbols in each data block, a blind channel estimation approach is proposed for redundant precoded orthogonal frequency-division multiplexing （OFDM） systems. A redundant linear frequency-domain precoder is applied to each pair of blocks before they enter the OFDM system. Because of the introduced structure, the frequency-selective channel can be identified at the receiver based on autocorrelation operations, singular value decomposition （SVD）, and by resolving the scalar ambiguity. The proposed channel estimation method has low computational complexity and requires no prior statistical information on channel or noise. And the proposed blind method has high spectral efficiency owing to exploiting no training sequence. Computer simulations confirm that this proposed blind channel estimation method can identify the frequency-selective channels perfectly and obtain a good performance.展开更多
采用气相色谱–质谱联用法检测塑料及其制品中阻燃剂三(2-氯乙基)磷酸酯的含量。样品采用微波萃取,萃取温度为100℃,时间为10 min,浓缩样品溶液至近干后定容至1 m L,用0.45μm滤膜过滤,采用气相色谱–质谱联用仪进行定性定量分析。三(2...采用气相色谱–质谱联用法检测塑料及其制品中阻燃剂三(2-氯乙基)磷酸酯的含量。样品采用微波萃取,萃取温度为100℃,时间为10 min,浓缩样品溶液至近干后定容至1 m L,用0.45μm滤膜过滤,采用气相色谱–质谱联用仪进行定性定量分析。三(2-氯乙基)磷酸酯的质量浓度在0.1~10.0μg/mL范围内与色谱峰面积呈良好的线性,线性相关系数为0.999 8,检出限为0.02 mg/kg。空白样品加标回收率为85.1%~94.6%,测定结果的相对标准偏差在1.60%~4.15%(n=7)之间。该方法准确度高,重现性好,可作为塑料及其制品中三(2-氯乙基)磷酸酯的检测方法。展开更多
基金This project was supported by the National Natural Science Foundation of China (60572157)National Hi-Tech Research and Development Program (863) of China (2003AA123310).
文摘Considering that channel estimation can play a crucial role in coherent detection of the information symbols in each data block, a blind channel estimation approach is proposed for redundant precoded orthogonal frequency-division multiplexing （OFDM） systems. A redundant linear frequency-domain precoder is applied to each pair of blocks before they enter the OFDM system. Because of the introduced structure, the frequency-selective channel can be identified at the receiver based on autocorrelation operations, singular value decomposition （SVD）, and by resolving the scalar ambiguity. The proposed channel estimation method has low computational complexity and requires no prior statistical information on channel or noise. And the proposed blind method has high spectral efficiency owing to exploiting no training sequence. Computer simulations confirm that this proposed blind channel estimation method can identify the frequency-selective channels perfectly and obtain a good performance.
