BDSec:Security Authentication Protocol for BeiDou-Ⅱ Civil Navigation Message

Due to the lack of authentication mechanism in BeiDou navigation satellite system(BDS),BD-Ⅱ civil navigation message(BDⅡ-CNAV) are vulnerable to spoofing attack and replay attack.To solve this problem,we present a security authentication protocol,called as BDSec,which is designed by using China’s cryptography Shangyong Mima(SM) series algorithms,such as SM2/4/9 and Zu Chongzhi(ZUC)algorithm.In BDSec protocol,both of BDⅡ-CNAV and signature information are encrypted using the SM4 algorithm(Symmetric encryption mechanism).The encrypted result is used as the subject authentication information.BDSec protocol applies SM9 algorithm(Identity-based cryptography mechanism) to protect the integrity of the BDⅡ-CNAV,adopts the SM2 algorithm(Public key cryptosystem) to guarantee the confidentiality of the important session information,and uses the ZUC algorithm(Encryption and integrity algorithm) to verify the integrity of the message authentication serial number and initial information and the information in authentication initialization sub-protocol respectively.The results of the SVO logic reasoning and performance analysis show that BDSec protocol meets security requirements for the dual user identity authentication in BDS and can realize the security authentication of BDⅡ-CNAV.

Construction of BDS Spatiotemporal Information Agricultural Product Digital Credit System

Spatiotemporal information,positioning and navigation services have become important elements of new type infrastructure.The rapid development of global digital trade provides a large-scale application scenario for the use of Beidou Navigation Satellite System(BDS)spatiotemporal information to support the certification of origin of agricultural products.The BDS spatiotemporal information agricultural product digital credit system uses such modules as BDS,spatiotemporal information collection,spatiotemporal coding,and spatiotemporal blockchain.It incorporates multi-level joint supervision mechanisms such as government,associations,and users.Starting from the initial production link of agricultural products,it realizes the correspondence and locking of online and offline products,effectively improves the integrity and credibility of information in the production process,finished product quality and circulation process of products,effectively manages the green production and anti-channel conflicts of producers,and provides credible information for consumers,thus realizing the digital credit certification of products.The successful practice of characteristic agricultural products in Yunnan Province has verified the application ability of the BDS spatiotemporal information agricultural product digital credit system.This system has played a significant role in promoting the online and offline locking,credible information,effective supervision and high quality and high price of characteristic agricultural products from the field.The BDS provides services for global digital trade and contributes to the further enhancement of the global application scale of GNSS.

BDS PPP技术在云南民航通信导航应用中的探索

北斗卫星导航系统(BDS)是我国重要空间战略基础设施。为探究北斗精密单点定位(BDS PPP)技术在云南地区民航通信导航中的应用前景,本文基于云南4个地基北斗站动态和静态结果进行评估。静态结果显示,北斗静态定位在北向、东向和天向误差平均为2.1 mm、2.2 mm和5.7 mm,相当于6.5 mm三维定位误差;动态结果显示,北斗动态定位在北向、东向和天向误差平均为0.8 cm、1.0 cm和2.4 cm,相当于2.7 cm三维定位误差。此外,利用北斗系统进行静态和动态定位精度均略优于GPS,可能与北斗系统在我国可见卫星数更充足有关。本文实验结果在一定程度上证明了高精度的BDS PPP技术在云南地区民航通信导航中的应用前景。

BDS技术在铁路工程测量中的应用研究

对BDS技术在铁路工程控制测量中的技术可行性和成果可靠性进行分析研究,以某铁路施工项目为研究对象,布设铁路项目基础平面控制网(CPⅠ)、铁路线路平面控制网(CPⅡ),对基于BDS单星座、GPS单星座、BDS/GPS混合星座卫星系统的基线质量和控制网平差成果精度进行对比分析,结果表明:基于BDS单星座解算的基线质量略高于GPS单星座,BDS/GPS混合星座能够在一定程度上改善单一星座的基线质量;基于BDS单星座解算的铁路CPⅠ和CPⅡ控制网平差精度与GPS单星座精度基本一致,略低于BDS/GPS混合星座,但均具有较高精度,满足铁路工程控制测量规范及施工要求,可靠性较高,能够为铁路工程控制测量提供可靠的基准数据。

BDS-3不同双频组合动态PPP定位性能分析

基于北斗三号(BDS-3)的精密单点定位(PPP)技术在智能驾驶、智慧交通等领域具有广泛的应用前景。但目前对北斗三号不同信号双频组合基于不同PPP模型的动态定位性能研究与分析较少。因此,该文采用国产接收机实测静态和动态数据,基于无电离层组合模型(IF)和非差非组合模型(UDUC),分析BDS-3双频信号组合B1C/B2a、B1C/B3I、B1I/B2a和B2a/B3I的定位性能。实验结果显示,在静态、仿动态和动态数据处理模式下,B1C/B2a组合2种PPP模型定位性能都要优于其他3种双频信号组合,在定位精度上较其他3种组合改善都在7.5%以上,最大达到48.7%;在收敛时间上较其他3种组合提升都在4.5%以上,最大达到54.8%;在静态、仿动态和动态数据处理模式下,IF模型4种组合的PPP定位性能要优于UDUC模型,对于静态、仿动态和动态数据处理,IF模型4种组合的平均定位精度较UDCU模型分别改善25.9%、7.4%和18.9%,平均收敛时间分别提高84.6%、61.5%和4.9%。

基于Hatch滤波的改进矩阵变换法在BDS多频模糊度解算中的应用

长基线条件下,空间相关性弱,电离层延迟残差和噪声影响变大,致使矩阵变换法模糊度解算过程中,窄巷组合受噪声影响大,单历元模糊度解算成功率低。因此,削弱电离层残差及噪声影响可以一定程度提高模糊度解算成功率。本文在分析矩阵变换算法基础上,利用Hatch滤波有效抑制伪距测量噪声和多径效应特点,结合弱电离层、低噪声的载波组合,通过相位平滑伪距代替组合伪距值参与解算,从而削弱电离层残差及观测噪声影响。通过实测数据分析,本文算法可有效提高矩阵变换法模糊度解算成功率。

顾及BDS-3星钟约束的GNSS超快速轨道钟差解算方法

BDS-3高稳定星载原子钟作为北斗星座的显著技术优势,在GNSS数据处理中尚未得到充分利用。针对严格时效性限制下GNSS超快速轨道钟差参数精度受限问题,本文提出顾及BDS-3星钟约束的GNSS超快速轨道钟差解算方法。首先,以GNSS轨道钟差参数间相关性为基础,构建顾及BDS-3星钟参数特性的GNSS定轨模型;然后,基于GNSS精密钟差产品,分析星钟约束对GNSS轨道钟差参数精度的影响规律;最后,为克服预报钟差精度与约束筛选对定轨影响,建立BDS-3星钟建模与GNSS超快速轨道钟差估计的同步处理方法。试验结果表明,在BDS-3星钟参数最优约束下,BDS-3与GPS轨道钟差精度可分别提升27.5%、5.1%和20.2%、5.2%;且较传统BDS-3星钟单历元处理策略,基于BDS-3星钟建模与GNSS超快速定轨同步处理方法,GNSS超快速轨道钟差精度可分别提升至4.8%与34.2%,轨道精度实现了毫米级改善。因此,顾及BDS-3星钟约束的GNSS超快速轨道钟差解算方法可有效对BDS-3高稳星钟信息模型化,并实现GNSS超快速轨道钟差精度的优化处理。

Data-Driven Heuristic Assisted Memetic Algorithm for Efficient Inter-Satellite Link Scheduling in the BeiDou Navigation Satellite System

Inter-satellite link(ISL)scheduling is required by the BeiDou Navigation Satellite System(BDS)to guarantee the system ranging and communication performance.In the BDS,a great number of ISL scheduling instances must be addressed every day,which will certainly spend a lot of time via normal metaheuristics and hardly meet the quick-response requirements that often occur in real-world applications.To address the dual requirements of normal and quick-response ISL schedulings,a data-driven heuristic assisted memetic algorithm(DHMA)is proposed in this paper,which includes a high-performance memetic algorithm(MA)and a data-driven heuristic.In normal situations,the high-performance MA that hybridizes parallelism,competition,and evolution strategies is performed for high-quality ISL scheduling solutions over time.When in quick-response situations,the data-driven heuristic is performed to quickly schedule high-probability ISLs according to a prediction model,which is trained from the high-quality MA solutions.The main idea of the DHMA is to address normal and quick-response schedulings separately,while high-quality normal scheduling data are trained for quick-response use.In addition,this paper also presents an easy-to-understand ISL scheduling model and its NP-completeness.A seven-day experimental study with 10080 one-minute ISL scheduling instances shows the efficient performance of the DHMA in addressing the ISL scheduling in normal(in 84 hours)and quick-response(in 0.62 hour)situations,which can well meet the dual scheduling requirements in real-world BDS applications.

基于鲁棒双参数指数平滑法的BDS卫星钟差预报

为提高北斗(BDS)卫星钟差预报精度与稳定性,基于BDS卫星钟工作原理与数据特征,提出了一种基于鲁棒双参数指数平滑法的BDS卫星钟差预报方法。将双参数指数平滑法引入BDS钟差预报,并通过鲁棒化建模与优化初始值选取方式提升了双参数指数平滑法的抗差与适应能力,减小了数据异常干扰对钟差预报性能的影响。与常用的多项式模型、谱分析模型、灰色预测模型及超快速钟差预报产品进行对比分析,结果表明:所提方法适用于不同BDS轨道与类型的卫星钟差预报,取得了良好的预报精度与稳定性,其对BDS卫星钟的6h平均预报精度分别提升了40.3%、31.7%、63.6%和36.6%,预报稳定性分别提升了43.8%、38.9%、65.4%和33.1%。

BDS-2/BDS-3卫星观测数据联合处理关键技术研究

高质量卫星观测数据及高精度轨道钟差等产品作为全球导航与位置服务的核心,对整个系统的服务能力起到了至关重要作用。论文针对BDS-2/BDS-3卫星观测数据联合处理中空间构型、快速与高精度处理、轨道钟差精化及观测数据偏差等关键技术进行了深入探讨与系统研究。

顾及BDS-3/GNSS星钟状态的超快速钟差参数估计模型

高质量卫星轨道与钟差参数是实现导航系统可靠PNT服务的前提之一。针对多系统超快速定轨中钟差参数易受观测数据质量与模型配置影响的问题,本文提出一种顾及BDS-3/GNSS星钟状态的超快速钟差参数估计模型。首先,在固定的轨道、站坐标等参数基础上,构建顾及钟差速度与加速度的观测方程;然后,利用相位时间差分与模型奇异值分解算法,建立钟差参数质量控制与历元间传递模型;最后,引入钟差状态转移方程并顾及BDS-3/GNSS星钟频率稳定性,实现钟差及其状态参数的单历元同步估计。试验表明,本文提出的BDS-3/GNSS超快速钟差估计模型至少可实现钟差估计精度提升46.9%;且利用估计的钟差状态参数可导出历元间任意时刻钟差。相较于传统的超快速钟差产品,基于估计的BDS-3/GNSS钟差参数可实现四系统动态PPP测站的E、N与U方向定位精度与收敛性能分别提升1.7%、6.0%、31.2%与44.9%、33.3%、38.9%;且预报钟差精度也得到了改善,基于钟差及其状态序列的预报钟差参数可分别降低四系统静态PPP的E、N与U方向定位残差与收敛时间6.3%、13.5%、11.3%与14.5%、1.6%、12.4%。因此,本文提出的BDS-3/GNSS超快速钟差估计方法可有效提升钟差质量,并实现实时与近实时服务能力的提升。

Tropospheric Wet Refractivity Tomography Based on the BeiDou Satellite System

This paper presents a novel approach for assessing the precision of the wet refractivity field using BDS （BeiDou navigation satellite system） simulations only,GPS,and BDS＋GPS for the Shenzhen and Hongkong GNSS network.The simulations are carried out by adding artificial noise to a real observation dataset.Instead of using the δ and σ parameters computed from slant wet delay,as in previous studies,we employ the Bias and RMS parameters,computed from the tomography results of total voxels,in order to obtain a more direct and comprehensive evaluation of the precision of the refractivity field determination.The results show that：（1） the precision of tropospheric wet refractivity estimated using BDS alone （only 9 satellites used） is basically comparable to that of GPS; （2） BDS＋GPS （as of current operation） may not be able to significantly improve the data＇s spatial density for the application of refractivity tomography; and （3） any slight increase in the precision of refractivity tomography,particularly in the lower atmosphere,bears great significance for any applications dependent on the Chinese operational meteorological service.

混合星座对BDS PPP和ZTD估计的影响分析

针对北斗卫星导航系统BDS,研究了不同星座组合对精密单点定位PPP和天顶对流层延迟ZTD估计的影响。设计了MEO、MEO+GEO、MEO+IGSO以及MEO+GEO+IGSO等4种卫星组合方案,利用4个MGEX测站的观测数据进行了BDS静态PPP试验。结果表明:1)基于MEO卫星的BDS PPP三维位置精度最优;增加IGSO卫星可明显提高E坐标精度并缩短PPP收敛时间,但是U坐标精度略有降低。2)基于MEO卫星的BDS PPP估计的ZTD精度最优,其标准差在10 mm以内;增加GEO卫星使得ZTD估计的标准差明显增大;IGSO卫星对ZTD估计的精度影响较小。

LEO多星座增强BDS精密单点定位性能评估

针对不同构型的低轨星座(LEO)增强北斗卫星导航系统BDS的精密单点定位PPP性能开展研究。通过IGS高、中、低纬度6测站实测数据、精密轨道及钟差产品,生成BDS、“鸿雁”HY、“微厘空间”CS精密星历、卫星钟差、观测量等实验仿真数据,构建了LEO增强BDS PPP数学模型,实现了BDS、BDS+HY、BDS+CS、BDS+HY+CS不同组合PPP。实验结果表明,在10、60 min静态PPP定位精度以及平均可视卫星数、PDOP值等方面均有不同程度的提升,HY对高纬度KIRU站改善效果显著,收敛时间减至2 min以内,CS对低纬度FAA1站测站收敛时间的提升最大,从46 min 50 s缩短至2 min,HY+CS增强BDS的效果最好,10 min定位精度均能达到毫米级,除FAA1站外其他测站均收敛在1 min以内。

地基BDS/GNSS水汽监测在水利领域的研究进展与展望

地球上几乎所有的水汽都集中在对流层,水汽含量对全球气温、降水等气象要素都有很大的影响,在一定程度上可以影响地球气候变化,在全球范围内调节热量平衡.对对流层水汽监测、水资源管理、极端天气预警和气候变化研究等具有十分重要的作用.在北斗卫星导航系统(BeiDou Navigation Satellite System, BDS)/GNSS技术持续发展和完善的过程中,BDS/GNSS大气可降水量反演(precipitable water vapor,PWV)逐渐成为一种新型的水汽探测技术,相较于传统水汽探测技术可实现对水汽高精度、近实时的监测.本文对BDS/GNSS PWV反演的发展历程及研究现状进行了系统地综述,阐明其反演原理与方法,主要从高精度水汽监测、降水短临预报、气候变化及旱涝监测方面分析地基BDS/GNSS水汽监测在水利领域中的应用与发展方向.

BDS锚碇浮标监测海洋大气水汽初步探究

精细化、动态化监测海洋大气水汽含量对全球海洋气候相关研究具有重要意义。为探究基于北斗卫星导航系统(BDS)的锚碇浮标平台在海洋水汽探测应用中的潜力,本研究利用白龙浮标搭载的测量型接收机,分别在岸基静态模式和海面动态模式下,对获取的BDS和全球定位系统(GPS)观测数据进行精密单点定位处理,并进行大气可降水量(PWV)反演,同时以欧洲中期天气预报中心第五代全球气候再分析数据集(ERA5)获取的PWV为参考值进行精度评估。结果表明:岸基静态模式下利用BDS观测值反演的PWV精度为0.7 mm,GPS反演的PWV精度为0.6 mm。海面动态模式下利用BDS观测值反演的PWV精度为1.2 mm,GPS反演的PWV精度为2.0 mm,与岸基静态模式探测的水汽产品精度基本相符。初步证明了利用BDS锚碇浮标在海洋动态观测条件下进行水汽含量监测的可行性,但仍需更长期更充分的观测以进一步验证。

多路径误差对BDS-3变形监测精度的影响

为定量分析BDS-3观测值多路径误差对变形监测精度的影响,选取包含7个站点的某水利工程2022年共128 d的BDS-3监测数据,对监测站点周围树木裁剪树枝前后BDS-3观测值多路径误差、变形监测精度及二者的相关性进行研究。结果表明:1)多路径误差与BDS-3变形监测精度间存在强相关性,与其平面和高程精度的相关系数分别大于0.93和0.81;2)监测站点周围树枝裁剪后,使用B1I和B3I观测值的平均多路径误差从0.676 m、0.426 m降低至0.329 m、0.230 m,N、E、U方向的平均监测精度分别达0.9 mm、0.8 mm、1.7 mm和1.1 mm、1.0 mm、2.2 mm,较裁剪树枝前分别提高63%、69%、58%和52%、61%、48%;3)改变周围观测环境削弱多路径误差的影响后,使用B1I观测值的精度优于使用B3I观测值的精度,因此在BDS-3短基线变形监测的应用中推荐使用B1I观测值。

Modeling and Prediction of Inter-System Bias for GPS/BDS-2/BDS-3 Combined Precision Point Positioning

The combination of Precision Point Positioning(PPP)with Multi-Global Navigation Satellite System(MultiGNSS),called MGPPP,can improve the positioning precision and shorten the convergence time more effectively than the combination of PPP with only the BeiDou Navigation Satellite System(BDS).However,the Inter-System Bias(ISB)measurement of Multi-GNSS,including the time system offset,the coordinate system difference,and the inter-system hardware delay bias,must be considered for Multi-GNSS data fusion processing.The detected ISB can be well modeled and predicted by using a quadratic model(QM),an autoregressive integrated moving average model(ARIMA),as well as the sliding window strategy(SW).In this study,the experimental results indicate that there is no apparent difference in the ISB between BDS-2 and BDS-3 observations if B1I/B3I signals are used.However,an obvious difference in ISB can be found between BDS-2 and BDS-3 observations if B1I/B3I and B1C/B2a signals are used.Meanwhile,the precision of the Predicted ISB(PISB)on the next day of all stations is about 0.1−0.6 ns.Besides,to effectively utilize the PISB,a new strategy for predicting the PISB for MGPPP is proposed.In the proposed strategy,the PISB is used by adding two virtual observation equations,and an adaptive factor is adopted to balance the contribution of the Observed ISB(OISB)and the PISB to the final estimations of ISB.To validate the effectiveness of the proposed method,some experimental schemes are designed and tested under different satellite availability conditions.The results indicate that in open sky environment,the selective utilization of the PISB achieves almost the same positioning precision of MGPPP as the direct utilization of the PISB,but the convergence time of MGPPP is reduced by 7.1%at most in the north(N),east(E),and up(U)components.In the blocked sky environment,the selective utilization of the PISB contributes to more significant improvement of the positioning precision and convergence time than that in the open sky environment.Compared with the direct utilization of the PISB,the selective utilization of the PISB improves the positioning precision and convergence time by 6.7%and 12.7%at most in the N,E,and U components,respectively.

BDS-3 B2b-PPP URA评估精化与播发方法

用户距离精度指数(URAI)作为导航系统定位服务完好性标识,在提供卫星可用性信息的同时,也反映了卫星的轨道钟差精度。本文提出将B2b电文中随轨道改正数播发的URAI信息恢复为用户距离精度(URA),并用于B2bPPP的随机模型构建。对其进行定位性能评估,发现B2b自身播发的URA精度较差。针对该问题,利用分布在中国及周边区域的多个全球卫星导航系统(GNSS)监测站对B2b的URA参数进行重估计。实验结果表明:精化后的URA能显著提升B2b-PPP的服务性能。相比于仅考虑观测噪声和高度角的随机模型,使用精化后的URA作为随机模型,动态和静态定位模式下的收敛时间提升分别达到18.9%、14.5%;收敛后定位精度提升分别达到11.2%、8.9%。在此基础上,进一步结合北斗卫星导航系统(BDS)短报文,提出一种精化后URA的播发方法,结合现有短报文通信效率进一步分析了精化URA的用户使用性能。

一种顾及时空变化的BDS PPP多路径误差建模方法

根据BDS GEO、IGSO、MEO三种星座卫星轨道运行特性,使用多路径误差半天球格网点模型(multi-point hemispherical grid model,MHGM)和恒星日滤波(sidereal filtering,SF)方法建立BDS混合星座的多路径误差改正模型。使用该模型改正多路径误差后,BDS精密单点定位(precise point positioning,PPP)的载波相位验后残差显著减小,E、N、U方向定位精度分别提升41%、37%、38%,收敛速度整体提升31%。