Most GPS positioning errors can be eliminated or removed by the differential technique or the modeling method,but the multipath effect is a special kind of system or gross error,so it is difficult to be simulated or e...Most GPS positioning errors can be eliminated or removed by the differential technique or the modeling method,but the multipath effect is a special kind of system or gross error,so it is difficult to be simulated or eliminated.In order to improve the accuracy of GPS positioning,the single-epoch pseudorange multipath effects at GPS station were calculated,and firstly modeled based on the spherical cap harmonic（SCH）,which is the function of satellite longitude and latitude with the robust method.The accuracy of the kinematic point positioning technique was improved by correcting pseudorange observations with the multipath effect calculated by the SCH model,especially in the elevation direction.The spherical cap harmonic can be used to model the pseudorange multipath effect.展开更多
ABSTRACT The multipath has long been considered a major error source in GPS applications .The characteristics 0f the GPS signal multipath effects are analyzed. based on which an experiment that considers the characte...ABSTRACT The multipath has long been considered a major error source in GPS applications .The characteristics 0f the GPS signal multipath effects are analyzed. based on which an experiment that considers the characteristics of dynamic deformation monitoring has been carried out. The solution results of observation data in two successive days are processed by a method,which combines the wavelet filtering and the differential correction betweentwo successive days. The research demonstrates that the multipath errors have stronger repeatability on successive days;after significantly mitigating the influence of multipath effects,the accuracy of three-dimensional positioning for GPS dynamic deformation monitoring can attain the mm level,an obvious accuracy improving particularly invertical component.The characteristics of GPS signal multipath,th eexperimental scheme and the qualitative and quantitative analysis of results are detailed.展开更多
The electrical system in a launch vehicle contains multiple wireless communications systems. A large number of prelaunch tests are needed to verify the correctness and reliability of electric systems at the launch sit...The electrical system in a launch vehicle contains multiple wireless communications systems. A large number of prelaunch tests are needed to verify the correctness and reliability of electric systems at the launch site. The complex electromagnetic environment at a launch site will inevitably cause multipath effect which interfere with prelaunch tests. Theory analysis and simulation of multipath effect, combined with engineering practice, can effective identify and quickly correct abnormal situations, and identify methods and measures to eliminate the influence of multipath interference.展开更多
This paper discusses the time-of-arrival(TOA) based indoor visible light communication(VLC) positioning system in a non-line-of-sight environment. The propagation delay is assumed to be gamma distributed. The generali...This paper discusses the time-of-arrival(TOA) based indoor visible light communication(VLC) positioning system in a non-line-of-sight environment. The propagation delay is assumed to be gamma distributed. The generalized Cramer–Rao lower bound for multipath propagation is derived as the theoretical accuracy limitation. The performance of the positioning system is affected by the shape parameter and the scale parameter of gamma distribution.The influences on positioning accuracy of multipath effects are analyzed through discussing the physical meaning of the gamma distribution parameters. It is concluded that the lower bound of positioning accuracy is attained when variance of the non-line-of-sight propagation-induced path lengths is zero. The simulation result provesthat the theoretical positioning accuracy is in the order of centimeters with the given scenario.展开更多
Multipath and continuous wave (CW) interference may cause severe performance degradation of global navigation satellite system (GNSS) receivers. This paper analyzes the code tracking performance of early-minus-late po...Multipath and continuous wave (CW) interference may cause severe performance degradation of global navigation satellite system (GNSS) receivers. This paper analyzes the code tracking performance of early-minus-late power (EMLP) discriminator of GNSS receivers in the presence of multipath and CW interference. An analytical expression of the code tracking error is suggested for EMLP discriminator, and it can be used to assess the effect of multipath and CW interference. The derived expression shows that the combined effects include three components: multipath component;CW interference component and the combined component of multipath and CW interference. The effect of these components depends on some factors which can be classified into two categories: the receiving environment and the receiver parameters. Numerical results show how these factors affect the tracking performances. It is shown that the proper receiver parameters can suppress the combined effects of multipath and CW interference.展开更多
In this paper, multipath temporal spreading distributions of laser pulses are calculated when they travel through the seawater. Individual photon is followed in Monte Carlo calculation A modified Henyey-Greenstein （H...In this paper, multipath temporal spreading distributions of laser pulses are calculated when they travel through the seawater. Individual photon is followed in Monte Carlo calculation A modified Henyey-Greenstein （HG） function is applied to represent the scattering phase function of seawater. This paper proposes a new scaling method, which uses the effective scattering thickness τd to replace the optical thickness used in the traditional scaling technique. This paper compares the temporal spreading distributions of photons on conditions of different attenuation coefficients and target depths. The experiments reveal that these mutual deviations are changing in the range from 0.5% to 5%, so long as the corresponding effective scattering thicknesses τd remains the same. Therefore, a conclusion can be obtained, that the temporal spreading distribution is only dependent on the effective diffusion thickness τd .展开更多
The fifth generation (5G) wireless communication requires the massive multiple input multiple output (MIMO) technique. The massive MIMO antenna array of the millimeter wave (mm-wave) is recognized as a key enabler bec...The fifth generation (5G) wireless communication requires the massive multiple input multiple output (MIMO) technique. The massive MIMO antenna array of the millimeter wave (mm-wave) is recognized as a key enabler because of its high spectral efficiency. The higher the frequencies of the RF signal, the lower the distance it travels in free space caused by path loss, and it is more easily absorbed by obstacles, which are needed for high-gain transmitters. The advantage of the physical properties of higher New Radio (NR) frequencies is that 5G can utilize more spectrum, more antennas, and higher-order modulation schemes. The massive antennas and radio frequency chains improve the implementation of the cost of 5G wireless communication systems and result in an intense mutual coupling effect among antennas because of the limited space for deploying antennas. The upper bound of the effective capacity is derived for 5G multimedia massive MIMO communication systems. Two antennas that receive diversity gain models, the mutual coupling matrix, and the spacing antenna distance are built and analyzed. The impacts and affections of the antenna spacing the number of antennas, the quality-of-service (QoS) statistical exponent, and the number of independent incident directions on the upper effective capacity of 5G multimedia massive MIMO communication systems are analyzed. It is shown that for MIMO systems with compact transmit antenna arrays, the mutual coupling seriously degrades system capacity to mitigate the capacity degradation. In case of improvement in the mutual coupling by 99%, the system performance is kept stationary and enhances system capacity. However, the improvement of the mutual coupling is still about 87.5% today, which means the mutual coupling should be considered in 5G massive MIMO networks.展开更多
为提升低空突防作战场景下分布式多输入多输出(Multiple Input and Multiple Output,MIMO)雷达系统的目标检测效能,提出一种合作博弈功率分配(Cooperative Game Power Allocation,CGPA)算法。基于带误差的支援信息建立了低空多径环境下...为提升低空突防作战场景下分布式多输入多输出(Multiple Input and Multiple Output,MIMO)雷达系统的目标检测效能,提出一种合作博弈功率分配(Cooperative Game Power Allocation,CGPA)算法。基于带误差的支援信息建立了低空多径环境下的分布式MIMO雷达信号模型,并推导了基于奈曼皮尔逊准则的检测模型。结合Max-Min准则以信干噪比(Signal to Interference plus Noise Ratio,SINR)为优化模型的效用函数。在此基础上,利用加权方法简化了联盟利益Shapley值的计算,得到满足帕累托最优性和公平性的合作资源分配方案。通过对发射功率资源的细致化管理,有效减小多径效应引起接收信号幅度的参差与衰落。在改善接收信号的稳定性的同时,挖掘并利用多径环境下丰富的散射特性,有效提升了雷达系统的探测效能。仿真实验验证了分布式MIMO雷达系统低空多径目标检测的出色性能,所提功率分配算法能够有效提升系统检测性能,并具有较好的实时性。展开更多
中国科学院国家授时中心运行着多手段融合世界时UT1(universal time 1)测量系统,例行提供世界时UT1服务。系统主要包括位于吉林、海南和喀什的3个甚长基线干涉测量(very long baseline interferometry,VLBI)站和国际GNSS监测评估系统(in...中国科学院国家授时中心运行着多手段融合世界时UT1(universal time 1)测量系统,例行提供世界时UT1服务。系统主要包括位于吉林、海南和喀什的3个甚长基线干涉测量(very long baseline interferometry,VLBI)站和国际GNSS监测评估系统(international GNSS Monitoring and Assessment System,iGMAS)等。与VLBI站并址运行的iGMAS扩展跟踪站,与VLBI站并址观测,对于VLBI和iGMAS测量的世界时UT1融合解算至关重要。从数据完整率、观测噪声、多路径效应、周跳比等多个方面,对3个iGMAS扩展跟踪站观测BDS-3(BeiDou Navigation Satellite System)和GPS(Global Positioning System)系统的数据质量进行全面分析评估。2023年9月1日至30日共30 d观测数据分析结果表明,3个跟踪站的观测数据完整率优于90%,多路径误差小于0.3 m,码伪距观测噪声较小,载波相位观测噪声小于0.005周,大部分时段的周跳比大于500,单点定位精度(single point positioning,SPP)优于5 m。上述数据质量指标均满足北斗专项标准《全球连续监测评估系统(iGMAS)接入技术要求第1部分:跟踪站》的相关要求,因此,吉林、海南和喀什可作为iGMAS扩展跟踪站,后续可用于世界时UT1的测量、iGMAS的监测评估等。展开更多
基金Project (41374009) supported by the National Natural Science Foundation of ChinaProjects (TJES1101,TJES1203) supported by the Key Laboratory of Advanced Engineering Surveying of NASMG,China+1 种基金Project (ZR2013DM009) supported by the Shandong Natural Science Foundation of ChinaProject (201412001) supported by the Public Benefit Scientific Research Project of China
文摘Most GPS positioning errors can be eliminated or removed by the differential technique or the modeling method,but the multipath effect is a special kind of system or gross error,so it is difficult to be simulated or eliminated.In order to improve the accuracy of GPS positioning,the single-epoch pseudorange multipath effects at GPS station were calculated,and firstly modeled based on the spherical cap harmonic（SCH）,which is the function of satellite longitude and latitude with the robust method.The accuracy of the kinematic point positioning technique was improved by correcting pseudorange observations with the multipath effect calculated by the SCH model,especially in the elevation direction.The spherical cap harmonic can be used to model the pseudorange multipath effect.
文摘ABSTRACT The multipath has long been considered a major error source in GPS applications .The characteristics 0f the GPS signal multipath effects are analyzed. based on which an experiment that considers the characteristics of dynamic deformation monitoring has been carried out. The solution results of observation data in two successive days are processed by a method,which combines the wavelet filtering and the differential correction betweentwo successive days. The research demonstrates that the multipath errors have stronger repeatability on successive days;after significantly mitigating the influence of multipath effects,the accuracy of three-dimensional positioning for GPS dynamic deformation monitoring can attain the mm level,an obvious accuracy improving particularly invertical component.The characteristics of GPS signal multipath,th eexperimental scheme and the qualitative and quantitative analysis of results are detailed.
文摘The electrical system in a launch vehicle contains multiple wireless communications systems. A large number of prelaunch tests are needed to verify the correctness and reliability of electric systems at the launch site. The complex electromagnetic environment at a launch site will inevitably cause multipath effect which interfere with prelaunch tests. Theory analysis and simulation of multipath effect, combined with engineering practice, can effective identify and quickly correct abnormal situations, and identify methods and measures to eliminate the influence of multipath interference.
基金supported by the National Key Basic Research Program of China (973 program) under grant 2013CB32920the Natural Science Foundation of China under grant 61375083
文摘This paper discusses the time-of-arrival(TOA) based indoor visible light communication(VLC) positioning system in a non-line-of-sight environment. The propagation delay is assumed to be gamma distributed. The generalized Cramer–Rao lower bound for multipath propagation is derived as the theoretical accuracy limitation. The performance of the positioning system is affected by the shape parameter and the scale parameter of gamma distribution.The influences on positioning accuracy of multipath effects are analyzed through discussing the physical meaning of the gamma distribution parameters. It is concluded that the lower bound of positioning accuracy is attained when variance of the non-line-of-sight propagation-induced path lengths is zero. The simulation result provesthat the theoretical positioning accuracy is in the order of centimeters with the given scenario.
文摘Multipath and continuous wave (CW) interference may cause severe performance degradation of global navigation satellite system (GNSS) receivers. This paper analyzes the code tracking performance of early-minus-late power (EMLP) discriminator of GNSS receivers in the presence of multipath and CW interference. An analytical expression of the code tracking error is suggested for EMLP discriminator, and it can be used to assess the effect of multipath and CW interference. The derived expression shows that the combined effects include three components: multipath component;CW interference component and the combined component of multipath and CW interference. The effect of these components depends on some factors which can be classified into two categories: the receiving environment and the receiver parameters. Numerical results show how these factors affect the tracking performances. It is shown that the proper receiver parameters can suppress the combined effects of multipath and CW interference.
基金Supported by the National Natural Science Foundation of China (60572015)
文摘In this paper, multipath temporal spreading distributions of laser pulses are calculated when they travel through the seawater. Individual photon is followed in Monte Carlo calculation A modified Henyey-Greenstein （HG） function is applied to represent the scattering phase function of seawater. This paper proposes a new scaling method, which uses the effective scattering thickness τd to replace the optical thickness used in the traditional scaling technique. This paper compares the temporal spreading distributions of photons on conditions of different attenuation coefficients and target depths. The experiments reveal that these mutual deviations are changing in the range from 0.5% to 5%, so long as the corresponding effective scattering thicknesses τd remains the same. Therefore, a conclusion can be obtained, that the temporal spreading distribution is only dependent on the effective diffusion thickness τd .
文摘The fifth generation (5G) wireless communication requires the massive multiple input multiple output (MIMO) technique. The massive MIMO antenna array of the millimeter wave (mm-wave) is recognized as a key enabler because of its high spectral efficiency. The higher the frequencies of the RF signal, the lower the distance it travels in free space caused by path loss, and it is more easily absorbed by obstacles, which are needed for high-gain transmitters. The advantage of the physical properties of higher New Radio (NR) frequencies is that 5G can utilize more spectrum, more antennas, and higher-order modulation schemes. The massive antennas and radio frequency chains improve the implementation of the cost of 5G wireless communication systems and result in an intense mutual coupling effect among antennas because of the limited space for deploying antennas. The upper bound of the effective capacity is derived for 5G multimedia massive MIMO communication systems. Two antennas that receive diversity gain models, the mutual coupling matrix, and the spacing antenna distance are built and analyzed. The impacts and affections of the antenna spacing the number of antennas, the quality-of-service (QoS) statistical exponent, and the number of independent incident directions on the upper effective capacity of 5G multimedia massive MIMO communication systems are analyzed. It is shown that for MIMO systems with compact transmit antenna arrays, the mutual coupling seriously degrades system capacity to mitigate the capacity degradation. In case of improvement in the mutual coupling by 99%, the system performance is kept stationary and enhances system capacity. However, the improvement of the mutual coupling is still about 87.5% today, which means the mutual coupling should be considered in 5G massive MIMO networks.
文摘为提升低空突防作战场景下分布式多输入多输出(Multiple Input and Multiple Output,MIMO)雷达系统的目标检测效能,提出一种合作博弈功率分配(Cooperative Game Power Allocation,CGPA)算法。基于带误差的支援信息建立了低空多径环境下的分布式MIMO雷达信号模型,并推导了基于奈曼皮尔逊准则的检测模型。结合Max-Min准则以信干噪比(Signal to Interference plus Noise Ratio,SINR)为优化模型的效用函数。在此基础上,利用加权方法简化了联盟利益Shapley值的计算,得到满足帕累托最优性和公平性的合作资源分配方案。通过对发射功率资源的细致化管理,有效减小多径效应引起接收信号幅度的参差与衰落。在改善接收信号的稳定性的同时,挖掘并利用多径环境下丰富的散射特性,有效提升了雷达系统的探测效能。仿真实验验证了分布式MIMO雷达系统低空多径目标检测的出色性能,所提功率分配算法能够有效提升系统检测性能,并具有较好的实时性。
