The blue-green light in the 450 nm to 550 nm band is usually used in underwater wireless optical communication (UWOC). The blue-green light transmission in seawater is scattered by the seawater effect and can achieve ...The blue-green light in the 450 nm to 550 nm band is usually used in underwater wireless optical communication (UWOC). The blue-green light transmission in seawater is scattered by the seawater effect and can achieve communication in non-line-of-sight (NLOS) transmission mode. Compared to line-of-sight (LOS) transmission, NLOS transmission does not require alignment and can be adapted to various underwater environments. The scattering coefficients of seawater at different depths are different, which makes the scattering of light in different depths of seawater different. In this paper, the received optical power and bit error rate (BER) of the photodetector (PD) were calculated when the scattering coefficients of blue-green light in seawater vary from large to small with increasing depth for NLOS transmission. The results show that blue-green light in different depths of seawater in the same way NLOS communication at the same distance, the received optical power and BER at the receiver are different, and the received optical power of green light is greater than that of blue light. Increasing the forward scattering coverage of the laser will suppress the received optical power of the PD, so when performing NLOS communication, appropriate trade-offs should be made between the forward scattering coverage of the laser and the received optical power.展开更多
针对超宽带(ultra wide band,UWB)定位中影响定位精度的非视距(non line of sight,NLoS)传播误差问题,提出了一种基于Kalman滤波的NLoS误差二次消除方法.该方法利用NLoS误差与测量误差之间的相互独立性,借助Kalman滤波将NLoS误差从总误...针对超宽带(ultra wide band,UWB)定位中影响定位精度的非视距(non line of sight,NLoS)传播误差问题,提出了一种基于Kalman滤波的NLoS误差二次消除方法.该方法利用NLoS误差与测量误差之间的相互独立性,借助Kalman滤波将NLoS误差从总误差中单独分离出来,对其进行实时估计,并将该NLoS误差估计值作为NLoS误差辨别及测距值修正的依据.通过Kalman滤波对到达时间(time of arrival,TOA)测距值进行二次估计、鉴别及修正以提高TOA测距精度,从而实现室内复杂环境下的UWB精准实时定位.仿真实验结果表明:该方法不仅能够对NLoS误差实现良好的跟踪估计,对视距(line of sight,LoS)/NLoS环境转变也具有较强的灵敏感知能力,同时NLoS误差测距值在应用该方法后的定位性能逼近于LoS环境下的理想状态.展开更多
在无线通信定位中,无线信号中引入的非视距(Non-Line of Sight,NLOS)误差会严重降低系统的定位精度。针对上述问题,首先引入信息阈值和缩放因子,细分非视距误差的影响程度,对卡尔曼迭代过程中的增益进行更为精准的实时调整,利用改进后...在无线通信定位中,无线信号中引入的非视距(Non-Line of Sight,NLOS)误差会严重降低系统的定位精度。针对上述问题,首先引入信息阈值和缩放因子,细分非视距误差的影响程度,对卡尔曼迭代过程中的增益进行更为精准的实时调整,利用改进后的卡尔曼滤波算法更大程度上消除了NLOS误差和系统测量误差;其次引入基于测距残差的加权系数对线性位置线(Linear Line of Position,LLOP)和Taylor定位方法的计算结果进行综合处理,进一步提高定位精度和稳健性。实验结果表明,在NLOS环境下,所提算法优于经典的LLOP算法、Chan算法、LLOP-Taylor算法和基于卡尔曼滤波的LLOP算法。展开更多
文摘The blue-green light in the 450 nm to 550 nm band is usually used in underwater wireless optical communication (UWOC). The blue-green light transmission in seawater is scattered by the seawater effect and can achieve communication in non-line-of-sight (NLOS) transmission mode. Compared to line-of-sight (LOS) transmission, NLOS transmission does not require alignment and can be adapted to various underwater environments. The scattering coefficients of seawater at different depths are different, which makes the scattering of light in different depths of seawater different. In this paper, the received optical power and bit error rate (BER) of the photodetector (PD) were calculated when the scattering coefficients of blue-green light in seawater vary from large to small with increasing depth for NLOS transmission. The results show that blue-green light in different depths of seawater in the same way NLOS communication at the same distance, the received optical power and BER at the receiver are different, and the received optical power of green light is greater than that of blue light. Increasing the forward scattering coverage of the laser will suppress the received optical power of the PD, so when performing NLOS communication, appropriate trade-offs should be made between the forward scattering coverage of the laser and the received optical power.
文摘针对超宽带(ultra wide band,UWB)定位中影响定位精度的非视距(non line of sight,NLoS)传播误差问题,提出了一种基于Kalman滤波的NLoS误差二次消除方法.该方法利用NLoS误差与测量误差之间的相互独立性,借助Kalman滤波将NLoS误差从总误差中单独分离出来,对其进行实时估计,并将该NLoS误差估计值作为NLoS误差辨别及测距值修正的依据.通过Kalman滤波对到达时间(time of arrival,TOA)测距值进行二次估计、鉴别及修正以提高TOA测距精度,从而实现室内复杂环境下的UWB精准实时定位.仿真实验结果表明:该方法不仅能够对NLoS误差实现良好的跟踪估计,对视距(line of sight,LoS)/NLoS环境转变也具有较强的灵敏感知能力,同时NLoS误差测距值在应用该方法后的定位性能逼近于LoS环境下的理想状态.
文摘在无线通信定位中,无线信号中引入的非视距(Non-Line of Sight,NLOS)误差会严重降低系统的定位精度。针对上述问题,首先引入信息阈值和缩放因子,细分非视距误差的影响程度,对卡尔曼迭代过程中的增益进行更为精准的实时调整,利用改进后的卡尔曼滤波算法更大程度上消除了NLOS误差和系统测量误差;其次引入基于测距残差的加权系数对线性位置线(Linear Line of Position,LLOP)和Taylor定位方法的计算结果进行综合处理,进一步提高定位精度和稳健性。实验结果表明,在NLOS环境下,所提算法优于经典的LLOP算法、Chan算法、LLOP-Taylor算法和基于卡尔曼滤波的LLOP算法。
