The satellite-based automatic identification system (AIS) receiver has to encounter the frequency offset caused by the Doppler effect and the oscillator instability. This paper proposes a non-coherent sequence detecti...The satellite-based automatic identification system (AIS) receiver has to encounter the frequency offset caused by the Doppler effect and the oscillator instability. This paper proposes a non-coherent sequence detection scheme for the satellite-based AIS signal transmitted over the white Gaussian noise channel. Based on the maximum likelihood estimation and a Viterbi decoder, the proposed scheme is capable of tolerating a frequency offset up to 5% of the symbol rate. The complexity of the proposed scheme is reduced by the state-complexity reduction, which is based on per-survivor processing. Simulation results prove that the proposed non-coherent sequence detection scheme has high robustness to frequency offset compared to the relative scheme when messages collision exists.展开更多
The influence of cells groupings factor to the performance of the cells groupings time-shift pilot scheme is researched for the multiple cells large scale antennas systems（LSAS）. The former researches have confirmed...The influence of cells groupings factor to the performance of the cells groupings time-shift pilot scheme is researched for the multiple cells large scale antennas systems（LSAS）. The former researches have confirmed that the cells groupings time-shift pilots scheme is effective to reduce inter-cell interference, especially pilot contamination, which results from the pilot reuse in adjacent cells. However, they have not specified reasonable cells groupings factor, which plays a critical role in the general performance of the LSAS. Therefore, this problem is researched in details. The time for reverse-link data transmission will be compressed, when the groupings factor surpasses a certain range. Thus it is not always beneficial to increase the cells groupings factor without limitation. Furthermore,a reasonable cells groupings factor is deduced from the perspective of optimization to enhance the system performance. Simulations verify the proposed cell grouping factor.展开更多
泵站、长距离供水等有压输水系统中,精准、高效的水力计算对于系统水力安全、智慧调控至关重要。然而,现有的水锤计算大多基于稳态摩阻假定,低估了水锤衰减;尤其是采用的特征线法因插值计算或调整波速,常会引起计算误差。为了精准、高...泵站、长距离供水等有压输水系统中,精准、高效的水力计算对于系统水力安全、智慧调控至关重要。然而,现有的水锤计算大多基于稳态摩阻假定,低估了水锤衰减;尤其是采用的特征线法因插值计算或调整波速,常会引起计算误差。为了精准、高效地模拟水锤问题,构建了Urbanowicz and Zarzycki简化加权类动态摩阻水锤模型,采用二阶Godunov格式进行模型求解,并设计搭建了水锤试验台,将所建模型计算结果与Zielke模型、Brunone模型、传统的特征线法结果、试验结果进行对比分析。结果表明,所建模型可以精准仿真水锤压力的波动峰值与周期,与试验结果基本吻合;Zielke模型与所建模型具有基本一致的计算精度,纳什效率系数可达0.94,但Zielke模型计算耗时量巨大;Brunone模型计算效率略优于所建模型,但计算精度较差,纳什效率系数为0.87;当库朗数小于1时,特征线法会出现严重的数值耗散,而本文模型仅有轻微的数值衰减。可见,所建模型提供了一种精准、高效、稳定的水锤模拟方法。展开更多
文摘The satellite-based automatic identification system (AIS) receiver has to encounter the frequency offset caused by the Doppler effect and the oscillator instability. This paper proposes a non-coherent sequence detection scheme for the satellite-based AIS signal transmitted over the white Gaussian noise channel. Based on the maximum likelihood estimation and a Viterbi decoder, the proposed scheme is capable of tolerating a frequency offset up to 5% of the symbol rate. The complexity of the proposed scheme is reduced by the state-complexity reduction, which is based on per-survivor processing. Simulation results prove that the proposed non-coherent sequence detection scheme has high robustness to frequency offset compared to the relative scheme when messages collision exists.
基金supported by the National Natural Science Foundation of China(6110602261574013)
文摘The influence of cells groupings factor to the performance of the cells groupings time-shift pilot scheme is researched for the multiple cells large scale antennas systems（LSAS）. The former researches have confirmed that the cells groupings time-shift pilots scheme is effective to reduce inter-cell interference, especially pilot contamination, which results from the pilot reuse in adjacent cells. However, they have not specified reasonable cells groupings factor, which plays a critical role in the general performance of the LSAS. Therefore, this problem is researched in details. The time for reverse-link data transmission will be compressed, when the groupings factor surpasses a certain range. Thus it is not always beneficial to increase the cells groupings factor without limitation. Furthermore,a reasonable cells groupings factor is deduced from the perspective of optimization to enhance the system performance. Simulations verify the proposed cell grouping factor.
文摘泵站、长距离供水等有压输水系统中,精准、高效的水力计算对于系统水力安全、智慧调控至关重要。然而,现有的水锤计算大多基于稳态摩阻假定,低估了水锤衰减;尤其是采用的特征线法因插值计算或调整波速,常会引起计算误差。为了精准、高效地模拟水锤问题,构建了Urbanowicz and Zarzycki简化加权类动态摩阻水锤模型,采用二阶Godunov格式进行模型求解,并设计搭建了水锤试验台,将所建模型计算结果与Zielke模型、Brunone模型、传统的特征线法结果、试验结果进行对比分析。结果表明,所建模型可以精准仿真水锤压力的波动峰值与周期,与试验结果基本吻合;Zielke模型与所建模型具有基本一致的计算精度,纳什效率系数可达0.94,但Zielke模型计算耗时量巨大;Brunone模型计算效率略优于所建模型,但计算精度较差,纳什效率系数为0.87;当库朗数小于1时,特征线法会出现严重的数值耗散,而本文模型仅有轻微的数值衰减。可见,所建模型提供了一种精准、高效、稳定的水锤模拟方法。
