In this paper, a new timing offset estimation method for Orthogonal FrequencyDivision Multiplexing ( OFDM) systems are presented. Upon the receipt of just one trainingsequence, this presence of a signal and the start ...In this paper, a new timing offset estimation method for Orthogonal FrequencyDivision Multiplexing ( OFDM) systems are presented. Upon the receipt of just one trainingsequence, this presence of a signal and the start of the frame can be detected. The performances ofthe timing estimator in additive white Gaussian noise and the mo bile multipath channel areevaluated by simulation . The results delivered by this algorithm are compared with thosedelivered by Schmidl and Cox.展开更多
We experimentally demonstrate all-optical clock recovery for 100 Gb/s return-to-zero on-off keying signals based on a monolithic dual-mode distributed Bragg reflector （DBR） laser, which can realize both mode spacing...We experimentally demonstrate all-optical clock recovery for 100 Gb/s return-to-zero on-off keying signals based on a monolithic dual-mode distributed Bragg reflector （DBR） laser, which can realize both mode spacing and wavelength tuning. By using a coherent injection locking scheme, a 100 GHz optical clock can be recovered with a timing jitter of 530 fs, which is derived by an optical sampling oscilloscope from both the phase noise and the power fluctuation. Furthermore, for degraded injection signals with an optical signal-to-noise ratio as low as 4.1 dB and a 25 km long distance transmission, good-quality optical clocks are all successfully recovered.展开更多
An all-optical clock recovery scheme based on monolithic amplified feedback DFB laser （AFL） diode is proposed for nonreturn-to-zero （NRZ） quadrature phase shift keying （QPSK） format signals. By using a preproces...An all-optical clock recovery scheme based on monolithic amplified feedback DFB laser （AFL） diode is proposed for nonreturn-to-zero （NRZ） quadrature phase shift keying （QPSK） format signals. By using a preprocessing stage, clock recovery （CR） is successfully demonstrated for 40-Gbaud NRZ-QPSK signals based on this scheme. The dependence of the timing jitter of the recovered clock on the optical power of the injected signal is investigated. A minimum timing jitter of 362.8 fs （integrated within a frequency range from 10 Hz to 10 MHz） is obtained.展开更多
基金国家自然科学基金面上项目(8127387681473800)+3 种基金"十二五"国家科技支撑计划课题(2013BAI02B10)supported by National Natural Science Foundation of China(8127387681473800)National 12th Five Year Science and Technology Program(2013BAI02B10)
文摘目的对比重症急性肾损伤（acute kidney injury,AKI）早期与晚期应用肾脏替代法（renal replacement therapy,RRT）治疗后的生存率与肾功能恢复情况。方法使用Meta分析方法,检索中国知网、万方、MEDLINE、Pub Med、EMBASE、Web of Science（1985年1月至2015年5月）数据库中相关随机对照试验（randomized controlled trial,RCT）及观察性研究文献,并扩展至所有涉及的参考文献,进行双人交叉文献纳入、排除,提取最终获得的文献的效应量,使用STAT11.0进行合并、数据分析。结果获得参考文献1 494篇,经过纳入、排除后,最终获得符合要求的文献15篇（2篇RCT、4篇前瞻队列研究、9篇回顾队列研究）。文献整体方法学质量不高。早期应用肾脏替代法患者比晚期应用患者的28日存活率显著提高（合并OR值=0.45,95%CI：0.28～0.72,P〈0.001）。各研究间异质性较大（I2=78%）。以收治重症加强护理病房（intensive care unit,ICU）类别、研究设计分别进行亚组分析未发现各亚组差异有统计学意义（P〈0.05）。提取有次要结局指标的报道（7篇）的肾功能恢复效应量进行合并,并未发现早期应用比晚期应用肾脏替代法对肾功能恢复有显著提升（OR=0.62,95%CI：0.34～1.13,I2=69.6%）。结论 1）早期应用体外RRT治疗重症急性肾损伤,有助于提高患者存活率,提高幅度明显;2）现有证据表明,早期开展RRT无助于重症AKI患者肾功能恢复;3）提供现有证据的研究大部分样本量较小,研究设计不统一,质量参差不齐。在设计合理的大规模多中心RCT证据出现之前,现有的关于RRT使用时机的结论并不一定能完全代表客观事实;4）有必要展开相关研究,明确定义RRT治疗时机中的＂早期＂与＂晚期＂。
文摘In this paper, a new timing offset estimation method for Orthogonal FrequencyDivision Multiplexing ( OFDM) systems are presented. Upon the receipt of just one trainingsequence, this presence of a signal and the start of the frame can be detected. The performances ofthe timing estimator in additive white Gaussian noise and the mo bile multipath channel areevaluated by simulation . The results delivered by this algorithm are compared with thosedelivered by Schmidl and Cox.
基金supported by the National 973 Program of China(Nos.2011CB301702 and 2011CB301703)the National Natural Science Foundation of China(Nos.61201103,61335009,and 61321063)
文摘We experimentally demonstrate all-optical clock recovery for 100 Gb/s return-to-zero on-off keying signals based on a monolithic dual-mode distributed Bragg reflector （DBR） laser, which can realize both mode spacing and wavelength tuning. By using a coherent injection locking scheme, a 100 GHz optical clock can be recovered with a timing jitter of 530 fs, which is derived by an optical sampling oscilloscope from both the phase noise and the power fluctuation. Furthermore, for degraded injection signals with an optical signal-to-noise ratio as low as 4.1 dB and a 25 km long distance transmission, good-quality optical clocks are all successfully recovered.
基金This work was supported by the National ＂973＂ Program of China （No. 2011CB301702）, in part by the National ＂863＂ Program of China （No. 2013AA014202）, and the National Natural Science Foundation of China （Nos. 61201103, 61335009, 61274045, and 61205031）.
文摘An all-optical clock recovery scheme based on monolithic amplified feedback DFB laser （AFL） diode is proposed for nonreturn-to-zero （NRZ） quadrature phase shift keying （QPSK） format signals. By using a preprocessing stage, clock recovery （CR） is successfully demonstrated for 40-Gbaud NRZ-QPSK signals based on this scheme. The dependence of the timing jitter of the recovered clock on the optical power of the injected signal is investigated. A minimum timing jitter of 362.8 fs （integrated within a frequency range from 10 Hz to 10 MHz） is obtained.
