With the rapid demand for underwater optical communication(UOC), studies of UOC degradation by oceanic turbulence have attached increasing attention worldwide and become a research hot-spot in recent years. Previous s...With the rapid demand for underwater optical communication(UOC), studies of UOC degradation by oceanic turbulence have attached increasing attention worldwide and become a research hot-spot in recent years. Previous studies used a simplified and inaccurate oceanic turbulence spectrum, in which the eddy diffusivity ratio between temperature and salinity is assumed to be unity and the outer scale of turbulence is assumed to be infinite. However, both assumptions are not true in most of the actual marine environments. In this paper, based on the Rytov theory in weak turbulence, we derive analytical expressions of "the aperture-averaged scintillation index"(SI) for both plane and spherical waves, which can clearly demonstrate how SI is influenced by several key factors in UOC. Then, typical fade statistics of the UOC system in weak turbulence is discussed including the probability of fade, the expected number of fades per time, the mean fade time,signal-to-noise ratio and bit error rate. Our results show that spherical wave is preferable in the UOC system in weak turbulence compared to plane wave, and the aperture-averaged effect has a significant impact on UOC system's performance.Our results can be used to determine those key parameters for designing the UOC system over reasonable ranges.展开更多
Zero Crossing Digital Phase Locked Loop with Arc Sine block (AS-ZCDPLL) is used to linearize the phase difference detection, and enhance the loop performance. The loop has faster acquisition, less steady state phase e...Zero Crossing Digital Phase Locked Loop with Arc Sine block (AS-ZCDPLL) is used to linearize the phase difference detection, and enhance the loop performance. The loop has faster acquisition, less steady state phase error, and wider locking range compared to the conventional ZCDPLL. This work presents a Zero Crossing Digital Phase Locked Loop with Arc Sine block (ZCDPLL-AS). The performance of the loop is analyzed under mobile faded channel conditions. The mobile channel is assumed to be two path fading channel corrupted by additive white Gaussian noise (AWGM). It is shown that for a constant filter gain, the frequency spread has no effect on the steady state phase error variance when the loop is subjected to a phase step. For a frequency step and under the same conditions, the effect on phase error is minimal.展开更多
The different realistic propagation channels are faced frequently the multipath fading environments. The main goal of this system design (cognitive radio network) is to improve the efficiency of spectrum access on a n...The different realistic propagation channels are faced frequently the multipath fading environments. The main goal of this system design (cognitive radio network) is to improve the efficiency of spectrum access on a non-interfering basis. This system achieves high utilization for the limited spectrum in order to fulfill needs for all users’ demands which are considered as a problem in wireless communications due to rapidly increasing in wireless applications and service. This system is exposed to attack due to the vulnerabilities existence in this system. So, the main outcome of this paper is to investigate the performance of the cooperative sensing in cognitive radio networks under malicious attacks over different channel impairments, and to illustrate the most suitable individual probability of detection in real faded channel by using Nakagami model. This paper illustrates the effectiveness of the attacks and fading on the performance of spectrum sensing process.展开更多
According to the list of beauty & personal care brand operation results announced by Tmall in April, OLAY ranked first in terms of beauty categoty, and L’Oreal and SK-II entered the Top 10 while no any Korean cos...According to the list of beauty & personal care brand operation results announced by Tmall in April, OLAY ranked first in terms of beauty categoty, and L’Oreal and SK-II entered the Top 10 while no any Korean cosmetic brands appeared. Specifically, OLAY, L'Oreal Paris, SK-II, Estée Lauder, Shiseido, Lanc?me, Maybelline, Chioture, Meiking and Chando were the TOP 10 brands. According to the survey's results in China, it is not that optimistic in terms of the sales of Korean cosmetics in Tmall apart from those in duty-free store and department stores.展开更多
Libya’s rebels face major challenges of unity when their many factions negotiate for power WHEN NATO jet fighters dropped the first bomb over Tripoli on March 19,no one expected Libyan strongman Muammar Gaddafi ]to d...Libya’s rebels face major challenges of unity when their many factions negotiate for power WHEN NATO jet fighters dropped the first bomb over Tripoli on March 19,no one expected Libyan strongman Muammar Gaddafi ]to doggedly resist a combined force of rebel militia and some of the world’s most advanced air munitions for more than five months.Yet the combined barrage eventually took its toll and the Gaddafi era has ended. The fluid situation in Libya changed seemingly overnight.On展开更多
Stochastic iterative learning control(ILC)is designed for solving the tracking problem of stochastic linear systems through fading channels.Consequently,the signals used in learning control algorithms are faded in the...Stochastic iterative learning control(ILC)is designed for solving the tracking problem of stochastic linear systems through fading channels.Consequently,the signals used in learning control algorithms are faded in the sense that a random variable is multiplied by the original signal.To achieve the tracking objective,a two-dimensional Kalman filtering method is used in this study to derive a learning gain matrix varying along both time and iteration axes.The learning gain matrix minimizes the trace of input error covariance.The asymptotic convergence of the generated input sequence to the desired input value is strictly proved in the mean-square sense.Both output and input fading are accounted for separately in turn,followed by a general formulation that both input and output fading coexists.Illustrative examples are provided to verify the effectiveness of the proposed schemes.展开更多
为提高OFDM(Orthogonal Frequency Division Multiplexing)系统通信衰落信道估计性能,提出一种基于深度神经网络的信道估计模型DeReNet。通过串联深度密集网络和深度残差网络,抑制网络训练中出现的梯度爆炸和消失问题。将该模型与LS(Lea...为提高OFDM(Orthogonal Frequency Division Multiplexing)系统通信衰落信道估计性能,提出一种基于深度神经网络的信道估计模型DeReNet。通过串联深度密集网络和深度残差网络,抑制网络训练中出现的梯度爆炸和消失问题。将该模型与LS(Least Square)、FC-DNN(Full Connection Dense Neural Network)和SimNet(Simplified Deep Neural Networks)模型进行仿真实验对比,结果表明,在莱斯衰落环境下该模型的信道估计性能更好,能有效提高信道衰落的估计精度。展开更多
基金supported by the fund from Xi’an Institute of Optics and Precision Mechanics。
文摘With the rapid demand for underwater optical communication(UOC), studies of UOC degradation by oceanic turbulence have attached increasing attention worldwide and become a research hot-spot in recent years. Previous studies used a simplified and inaccurate oceanic turbulence spectrum, in which the eddy diffusivity ratio between temperature and salinity is assumed to be unity and the outer scale of turbulence is assumed to be infinite. However, both assumptions are not true in most of the actual marine environments. In this paper, based on the Rytov theory in weak turbulence, we derive analytical expressions of "the aperture-averaged scintillation index"(SI) for both plane and spherical waves, which can clearly demonstrate how SI is influenced by several key factors in UOC. Then, typical fade statistics of the UOC system in weak turbulence is discussed including the probability of fade, the expected number of fades per time, the mean fade time,signal-to-noise ratio and bit error rate. Our results show that spherical wave is preferable in the UOC system in weak turbulence compared to plane wave, and the aperture-averaged effect has a significant impact on UOC system's performance.Our results can be used to determine those key parameters for designing the UOC system over reasonable ranges.
文摘Zero Crossing Digital Phase Locked Loop with Arc Sine block (AS-ZCDPLL) is used to linearize the phase difference detection, and enhance the loop performance. The loop has faster acquisition, less steady state phase error, and wider locking range compared to the conventional ZCDPLL. This work presents a Zero Crossing Digital Phase Locked Loop with Arc Sine block (ZCDPLL-AS). The performance of the loop is analyzed under mobile faded channel conditions. The mobile channel is assumed to be two path fading channel corrupted by additive white Gaussian noise (AWGM). It is shown that for a constant filter gain, the frequency spread has no effect on the steady state phase error variance when the loop is subjected to a phase step. For a frequency step and under the same conditions, the effect on phase error is minimal.
文摘The different realistic propagation channels are faced frequently the multipath fading environments. The main goal of this system design (cognitive radio network) is to improve the efficiency of spectrum access on a non-interfering basis. This system achieves high utilization for the limited spectrum in order to fulfill needs for all users’ demands which are considered as a problem in wireless communications due to rapidly increasing in wireless applications and service. This system is exposed to attack due to the vulnerabilities existence in this system. So, the main outcome of this paper is to investigate the performance of the cooperative sensing in cognitive radio networks under malicious attacks over different channel impairments, and to illustrate the most suitable individual probability of detection in real faded channel by using Nakagami model. This paper illustrates the effectiveness of the attacks and fading on the performance of spectrum sensing process.
文摘According to the list of beauty & personal care brand operation results announced by Tmall in April, OLAY ranked first in terms of beauty categoty, and L’Oreal and SK-II entered the Top 10 while no any Korean cosmetic brands appeared. Specifically, OLAY, L'Oreal Paris, SK-II, Estée Lauder, Shiseido, Lanc?me, Maybelline, Chioture, Meiking and Chando were the TOP 10 brands. According to the survey's results in China, it is not that optimistic in terms of the sales of Korean cosmetics in Tmall apart from those in duty-free store and department stores.
文摘Libya’s rebels face major challenges of unity when their many factions negotiate for power WHEN NATO jet fighters dropped the first bomb over Tripoli on March 19,no one expected Libyan strongman Muammar Gaddafi ]to doggedly resist a combined force of rebel militia and some of the world’s most advanced air munitions for more than five months.Yet the combined barrage eventually took its toll and the Gaddafi era has ended. The fluid situation in Libya changed seemingly overnight.On
基金supported by the National Natural Science Foundation of China(61673045)the Fundamental Research Funds for the Central Universities(XK1802-4)
文摘Stochastic iterative learning control(ILC)is designed for solving the tracking problem of stochastic linear systems through fading channels.Consequently,the signals used in learning control algorithms are faded in the sense that a random variable is multiplied by the original signal.To achieve the tracking objective,a two-dimensional Kalman filtering method is used in this study to derive a learning gain matrix varying along both time and iteration axes.The learning gain matrix minimizes the trace of input error covariance.The asymptotic convergence of the generated input sequence to the desired input value is strictly proved in the mean-square sense.Both output and input fading are accounted for separately in turn,followed by a general formulation that both input and output fading coexists.Illustrative examples are provided to verify the effectiveness of the proposed schemes.
