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1.
为了克服NLOS信号对移动无线电定位的影响,对TD-SCDMA系统中联合DOA与TOA实现移动终端定位的方案进行了研究,基于NLOS信号识别的算法有效地解决了NLOS信号对实施定位的影响,提出了一种对多基站时间加权定位算法,通过仿真实验证明了所采用算法的可行性,在NLOS情况下也可满足FCC对E-911业务的要求。  相似文献   

2.
一种在NLOS环境下提高精度的TDOA定位方法   总被引:2,自引:0,他引:2  
根据NLOS传播环境下附加传播时延和均方根时延扩展的统计特性,对NLOS误差的均值和方差进行了估计,并对TDOA(到达时间差)的测量值和方差进行了修正,在一定程度上消除了NLOS误差的影响。采用Chan算法对移动台(MS)位置进行定位。仿真结果表明,该方法能够提高Chan算法在NLOS传播环境下的定位精度。  相似文献   

3.
一种改进的减小NLOS影响的定位算法   总被引:1,自引:0,他引:1  
根据蜂窝网络中非视距(NLOS)传播时延服从指数分布的统计特性,在视距重构/平滑算法的基础上,提出了一种改进的减小NLOS影响的定位方法.该方法首先根据NLOS传播时延的统计特性,估计NLOS传播时延的均值和方差;然后对到达时间差(TDOA)测量值进行修正,进而估计移动台(MS)位置;最后对不同时刻估计的移动台位置进行加权处理,进一步减小NLOS的影响.仿真结果证明该方法能够有效提高定位算法的定位精度.  相似文献   

4.
针对蜂窝系统移动定位中扩展卡尔曼(EKF)受非直达波(NLOS)影响大,文章提出了一种改进扩展卡尔曼滤波(MEKF)算法;MEKF算法对标准的EKF进行改进,通过加大LOS基站测量值的权值能有效抑制NLOS导致的误差,显著地提高定位精度。文章对算法本身进行了分析,并给出了仿真结果。  相似文献   

5.
为了解决非视距(non-line of sight,NLOS)环境下超宽带(ultra-wideband,UWB)室内定位精度低的问题,提出一种基于到达时间差(time difference of arrival,TDOA)的UWB室内定位算法来削减NLOS误差,提高定位精度。利用卡尔曼滤波算法,初次估计移动标签节点与各锚节点间的TDOA值;基于TDOA差值进行NLOS误差判别,依据判别结果对受NLOS误差影响的测量值进行视距(line of sight,LOS)重构,并利用仅受LOS误差影响的历史值更新卡尔曼滤波的协方差阵;利用Chan-Taylor算法进行迭代计算,得到最终精确的定位结果。实验结果表明,在LOS环境下,提出的算法能达到分米级的定位精度;在受NLOS影响的环境下,该算法能有效提高定位精度,减小定位误差,具有更好的稳定性。  相似文献   

6.
在蜂窝网的移动终端定位中,非视距(NLOS)环境造成的误差是导致定位精度下降的主要原因.为降低NLOS误差的影响,本文提出了一种基于带符号残差加权的定位方法.该方法采用Chan算法算出移动台的初始位置,用带符号残差加权模型进行修正,再应用带符号残差辅助的泰勒级数展开法进行迭代,得到移动台的最终估计位置.仿真实验结果表明,与基于平方残差加权的方法相比,基于带符号残差加权的方法的定位精度平均提高约14.82%,可更加有效地抑制NLOS的影响.   相似文献   

7.
李炜 《科学技术与工程》2013,13(21):6260-6264
为了提高无线移动定位精度,提出一种基于最小二乘支持向量机修改误差的TDOA-AOA定位算法。该方法首先通过非线性学习能力强的最小二乘支持向量机对测量误差和NLOS误差进行修正,然后利用TDOA-AOA算法对移动端点位置进行估计,最后通过仿真实验测试LSSVM-TDOA-AOA的定位性能。仿真结果表明,LSSVM-TDOA-AOA提高了移动端点位置估计精度,定位误差明显低于对比算法,可以较好地满足实际无线移动通信定位要求。  相似文献   

8.
在室内环境下,移动台精确定位面临的主要问题是非视距(NLOS)和多径的影响.在非视距距离比例缩放(NLOS-Range-Scaling)算法的基础上,利用更多基站的信息,提出了适合室内情况的NLOS-Range-Scaling算法(ENRSA),研究了ENRSA算法在不同NLOS误差下的表现,结果表明该算法能更有效的降低NLOS误差的影响,定位精度比其他算法有显著提高.  相似文献   

9.
由于无线网络环境中客观存在非视距(NLOS)误差,采用传统的定位方式会对移动台位置的定位造成很大 的误差。通过对NLOS误差产生的原因及特点的分析,找出了鉴别NLOS误差及其抑制NLOS的方法---无约束 条件的非线性加权最小二乘算法,减少了NLOS对定位精度的影响,从而提高了无线定位技术的准确度。  相似文献   

10.
为了克服非视距信号(NLOS)对移动定位的影响,提出了一种基于卡尔曼滤波器的平滑技术.首先对到达时间(TOA)测量数据进行周期性的NLOS环境判决标识,然后根据不同结果利用不同形式的卡尔曼滤波对TOA测量数据进行平滑.将处理后的TOA代入到TDOA算法中进行定位估计.后面的跟踪虽然不能提高定位的精度,但可以平滑移动轨迹.仿真表明,该技术可以达到FCC对定位服务的要求.  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

13.
AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…  相似文献   

14.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

15.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

16.
本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。  相似文献   

17.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.  相似文献   

18.
19.
The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to  相似文献   

20.
Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with  相似文献   

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