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.

Dynamic Characteristics of Inter-Satellite Links in LEO Networks

To establish an efficient inter-satellite link (ISL) in an LEO network, the effect of geometric characteristics of ISL on the ISLs and the devices on the LEO satellite should be examined. Because of the continuous movement of the LEO satellite, the time-varying behaviours of the ISL's geometric charactersistics continuously change with the changes of the satellite's position on the orbit. These dynamic geometric characteristics of the ISLs are important for ISL's performance analyzing and the design of the devices on the LEO satellite. This paper describes dynamic geometric characteristics of ISL, analyzes the impact of these regulations on the tracking system of the satellite's antenna and the power adjusting system of the satellite's transmitter, with the Iridium system as an example.

Inter-satellite Link Topology Design and Relative Navigation for Satellite Clusters

A distributed relative navigation approach via inter-satellite sensing and communication for satellite clusters is proposed. The inter-satellite link(ISL)is used for ranging and exchanging data for the relative navigation,which can improve the autonomy of the satellite cluster. The ISL topology design problem is formulated as a multi-objective optimization problem where the energy consumption and the navigation performance are considered. Further,the relative navigation is performed in a distributed fashion,where each satellite in the cluster makes observations and communicates with its neighbors via the ISL locally such that the transmission consumption and the computational complexity for the navigation are reduced. The ISL topology optimization problem is solved via the NSGA-Ⅱ algorithm,and the consensus Kalman filter is used for the distributed relative navigation. The proposed approach is flexible to varying tasks,with satellites joining or leaving the cluster anytime,and is robust to the failure of an individual satellite. Numerical simulations are presented to verify the feasibility of the proposed approach.

Adaptive frame length algorithm for inter-satellite links

In view of the low ranging efficiency of the conventional fixed frame-length algorithm in the inter-satellite link,an adaptive frame-length algorithm is proposed. The frame length is adjusted adaptively according to the results of ranging and velocity measuring to improve ranging efficiency. Buffers which enable the frame length to be selected discretely and adaptively are introduced to avoid frequent hopping of the frame-length.Frame length marker is created to automatically identify the frame-length for frame synchronization procedures in receivers. The feasibility and the validity of the proposed algorithm to improve the efficiency of ranging are verified through both theoretic analysis and simulation,and the efficiency improves up to 88% when there are five buffers. This improvement can be further enhanced by increasing the number of buffers. Proper allocation of inter-satellite buffers is required to make a balance between the ranging efficiency and the system complexity.

基于SIMULINK的空空导弹无线电修正通道仿真

中远程空对空导弹中制导阶段通常采用惯导+指令制导复合制导方式。在某型空对空导弹研制中,要在不同攻击弹道的情况下对无线电数据链路的传输情况进行仿真,以分析导弹无线电修正通道的工作效能,确定改进方案,计算导弹的最大攻击距离。本文基于S imu link建立了导弹、载机和目标三者空中运动平台,并在此平台中建立了无线电修正通道数据链路。最后,给出了无线电修正通道数据链路中导弹的无线电数据链路与载机-导弹距离、导弹姿态角和导弹弹道之间的关系的数字仿真结果。

Impacts of inter-satellite links on the ECOM model performance for BDS-3 MEO satellites

Inter-satellite link(ISL)plays an essential role in current and future Global Navigation Satellite System(GNSS).In this study,we investigate the impact of ISL observations on precise orbit determination for BeiDou-3 Navigation Satellite System(BDS-3)Medium Earth Orbit(MEO)satellites based on different Extended CODE Orbit Models(ECOM).Thanks to the better observation geometry of the Ka-band ISL data compared to the L-band data for BDS-3 MEO satellites,the ISL solution substantially reduces Orbit Boundary Discontinuity(OBD)errors,except for C30,which suffers from unstable Ka-band hardware delay.From the external quality analysis,ISL significantly enhances the reliability of the orbit of MEO satellites manufactured by the China Academy of Space Technology(CAST).The standard deviation(STD)of the satellite laser ranging(SLR)residuals is approximately 2.5 cm,and the root mean square(RMS)is reduced by 10–23%compared to L-band solutions.Besides,the Sun-elongation angle dependent systematic error in SLR residuals nearly vanishes based on the reduced 5-parameter ECOM(ECOM1)or extended 7-parameter ECOM(ECOM2)with ISL data.This is because the ISL reduces the correlation between state parameters and solar radiation pressure(SRP)parameters as well as those among SRP parameters,leading to a more accurate estimation of both orbit and SRP perturbations,particularly those along B direction.This confirms that the deficiency of the SRP models for BDS-3 CAST satellites can be compensated by using better observation geometry from ISL data.On the other hand,for the satellite manufactured by Shanghai Engineering Center for Microsatellites(SECM),the ISL allows for a more accurate estimation of the Bc_(1)parameter in the ECOM1 model.This only reduces linear systematic error,possibly because the impact generated by the satellite bus cannot be entirely absorbed by the B-direction parameters.

基于空时分组码的Link-16全空域增强传输方案

飞机间利用Link-16进行战术与指挥控制信息交互时,若只采用单天线通信,在一些场景中由于信号受机体遮挡会导致通信质量严重下降,甚至通信中断,无法实现全空域通信.针对这一问题,提出在机背和机腹各安装一幅天线,利用双天线进行信号收发,并结合Link-16时隙结构,采用空时分组码技术,在不降低系统频谱效率的同时实现全空域通信.仿真结果表明,在单天线通信受机体遮挡影响的场景下,采用空时分组码的双天线Link-16增强系统可有效实现全空域通信.

CC-Link在天线开闭所控制中的应用

本文主要介绍CC-Link在低频发信系统天线开闭所控制中的应用,阐述了控制系统的结构组成,通信方式及其实现。实际应用表明该系统稳定可靠、结构简单、可扩展性强,达到了运行数据共享、人机界面友好、远程控制便捷的目的。

Correction Factor for Power Gain in Antenna Arrays

Antenna array gain is a relative measure of performance defined differently in various literature. Most definitions of gain are not power consistent, and thus cannot be used directly in link budget analysis. In this short paper, we present a power correction factor for common definitions of power gain of antenna arrays that allows them to be used in standard link budget calculations.

An RVT-based power allocation method for dynamic LEO-MEO links

Optimizing the power resources allocation method of low earth orbit(LEO)satellites to medium earth orbit(MEO)satellite'links is a significant way to construct efficient satellite constellations for satellite communication.A game theory power allocation method based on remaining visible time(RVT)of LEO-MEO satellites is proposed.Firstly,one LEO-MEO satellite network is classified as a cluster in which the RVT of LEO satellites is modeled.Secondly,the cost function of RVT concerning the character of orbit and throughput in each LEO satellite is mainly designed,which gives greater punishment of utility value to LEO satellites with less RVT and is an essential part of the reasonable utility function applied in diverse motion scenes.Meanwhile,the existence of Nash equilibrium for the proposed utility function in game theory area is proved.Thirdly,an off-cluster scheme for LEO satellites through the proposed threshold is raised to ensure the overall utility value of the whole LEO satellites in cluster.Finally,the performance improvement of the proposed algorithm to the baseline algorithm is verified through simulations in different scenarios.

油气管道VSAT卫星链路计算方法研究

为了解决VSAT卫星链路完全依靠卫星厂家进行计算且无法核对厂家提供的数据是否正确的问题,针对VSAT卫星链路计算的可靠性和健壮性,提出了一种油气管道VSAT卫星链路计算方法。该方法采用“功带平衡”算法,将VSAT卫星链路的带宽占用比等同于功率占用比,计算出卫星转发器最大输出功率,进而计算等效功率密度,根据每载波占用卫星的ERIP值公式,计算出饱和通量密度,匹配出卫星天线尺寸及功放矩阵,根据匹配的卫星天线及功放计算VSAT卫星链路总载噪比,将VSAT卫星链路总载噪比和系统最低载噪比进行对比,VSAT卫星链路总载噪比大者为合适的卫星天线及功放,反之为不合适选项,用推算出的卫星天线及功放推算出功率占用比,功率占用比与带宽占用比差别较大时,需调整卫星天线及功放的选择,计算功率占用比,直到卫星天线及功放达到功率占用比等于带宽占用比,即为最优的卫星天线和功放。通过最终的计算可得出卫星天线与功放的匹配矩阵,在实际工程中需从中选取合适的卫星天线与功放中的最小值达到最经济、可靠的匹配。该计算方法通过软件编程进行了界面可视化显示,并在诸多工程中进行了详细验证,结果表明此方法准确可靠,很好地提升了VSAT卫星链路计算的可靠性和健壮性。

Autonomous satellite constellation orbit determination using the star sensor and inter-satellite links data

A method of autonomous orbit determination for a satellite constellation using a star sensor combined with inter satellite links(ISLs) is studied.Two types of simulated observation data,Three-Satellite Constellation ISLs and background stellar observations by a CCD star sensor,are first produced.Based on these data,an observation equation is built for the constellation joint autonomous orbit determination,in which the simulations are run.The accuracy of this method with different orbital determination models are analyzed and compared with regard to the effect of potential measurement errors.The results show that autonomous satellite constellation orbit determination using star sensor measurement and ISLs data is feasible.Finally,this paper arrives at several conclusions which contribute to extending this method to a more general satellite constellation.

Analysis of the connectivity and robustness of inter-satellite links in a constellation

In the design of new constellation configurations or research of existing constellation performance,the connectivity and robustness of inter-satellite links (ISL) are needed for analysis.In this paper,graph theory is used to analyze the connectivity and robustness of the ISL in constellations,which are measured under the requirements of a short average distance and a small range of ISL azimuth angles,elevation angles and distances.The method to determine ISL connectivity by using the adjacency matrix of graph theory is put forward for the first time,and the standards of the ISL performance are given using:the number of ways between any two satellites,cutting point,cutting edge,k-connectivity degree and k-edge connectivity degree of graph theory.Finally,in the simulation,the ISLs in the Walker 24/6/1 constellation and the ISLs in the Walker 24/3/1 constellation are established from the optimal perspective of the azimuth angle,elevation angle and distance,and the characteristics of ISL in the Walker 24/6/1 and Walker 24/3/1 constellations are compared.The conclusions of this paper can be used as a reference for the design of new constellation configurations and analysis of existing ISLs.

Orbit determination and time synchronization for BDS-3 satellites with raw inter-satellite link ranging observations

To provide competitive global positioning and timing services under the condition that monitoring stations are confined to Chinese territory,inter-satellite link(ISL)technology is used by the third-generation BeiDou Navigation Satellite System(BDS-3).The ISL,together with the dual one-way links between satellites and anchor stations,may enable autonomous navigation for BDS-3.In this paper,we propose a general observation model for orbit determination(OD)and time synchronization(TS)directly using non-simultaneous observations,such as raw ISL pseudoranges.With the proposed model,satellite orbits,clocks,and hardware delay biases of ISL equipment can be determined simultaneously by jointly processing inter-satellite one-way pseudorange data and observation data from ground monitoring stations.Moreover,autonomous OD and TS are also achievable with one-way pseudorange data from anchor stations and satellites.Data from eight BDS-3 satellites,two anchor stations,and seven monitoring stations located in China were collected to validate the proposed method.It is shown that by jointly processing data from the ISL and seven monitoring stations,the RMS of overlap orbit differences in radial direction is 0.019 m,the overlap clock difference(95%)is 0.185 ns,and the stability of the estimated hardware delay biases for each satellite is greater than 0.5 ns.Compared with the results obtained with the seven stations,the improvements of orbits in radial direction and clocks are 95.7%and 90.5%,respectively.When the hardware delay biases are fixed to predetermined values,the accuracies of orbits and clocks are further improved.By jointly processing pseudoranges from the satellites and the two anchor stations,the RMS of overlap orbit differences is 0.017 m in the radial direction,and the overlap clock difference(95%)is 0.037 ns.It has also been demonstrated that under the condition of one-way ranging links,the accuracies of orbits and clocks obtained by the above two modes are still significantly better than those obtained by using the data from the monitoring stations alone.

Inter-satellite link augmented BeiDou-3 orbit determination for precise point positioning

Precise Point Positioning(PPP) requires precise products, including high-accuracy satellite orbit and clock parameters. It is impossible to obtain an orbit solution that is sufficiently accurate for PPP services with a regional tracking network;therefore, satellite orbits are usually estimated by a global tracking network with a large number of ground stations. However, it is expensive to build globally distributed stations. Fortunately, BeiDou-3 satellites carry an InterSatellite Link(ISL) payload, which can track the whole arc of the BeiDou-3 satellites and enhance the orbit determination accuracy with regional ground stations. In this contribution, a novel orbit determination strategy for BeiDou-3 PPP is proposed, in which the BeiDou-3 satellite orbits are enhanced by the ISL. First, the generation of precise satellite products is demonstrated in detail.In addition, the products are assessed by Satellite Laser Ranging(SLR) residuals and overlap comparisons. Moreover, the products are used for receivers in China's Mainland to carry out the static and kinematic modes to research the PPP performance of Bei Dou-3’s 3IGSO/24MEO constellation.The SLR validations of the satellite orbits demonstrate an accuracy better than 0.1 m in the radial component, and the orbit overlap comparisons show accuracies of 0.016 m in the radial component,0.088 m in the along-track component and 0.087 m in the cross-track component. The Standard Deviation(STD) in the differences in overlapping arcs for the estimated satellite clocks is approximately 0.10 ns. The static PPP results demonstrate that the error in both the horizontal and vertical components is smaller than 10 cm after 30 minutes of convergence. After 24 hours of convergence,the errors are 0.70 cm, 0.63 cm and 1.99 cm for the north, east and up components, respectively.The kinematic PPP experiment illustrates that the Root Mean Square(RMS) position errors in the north, east and up components are approximately 3.23 cm, 5.27 cm and 8.64 cm, respectively,after convergence. The obtainable positioning and convergence performances are comparable to those using products generated by global tracking networks.

Precise orbit determination for a large LEO constellation with inter-satellite links and the measurements from different ground networks:a simulation study

Geodetic applications of Low Earth Orbit(LEO)satellites requires accurate satellite orbits.Instead of using onboard Global Navigation Satellite System observations,this contribution treats the LEO satellite constellation independently,using Inter-Satellite Links and the measurements of different ground networks.Due to geopolitical and geographical reasons,a ground station network cannot be well distributed.We compute the impact of different ground networks(i.e.,global networks with different numbers of stations and regional networks in different areas and latitudes)on LEO satellite orbit determination with and without the inter-satellite links.The results are based on a simulated constellation of 90 LEO satellites.We find that the orbits determined using a high latitude network is worse than using a middle or low latitude network.This is because the high latitude network has a poorer geometry even if the availability of satellite measurements is higher than for the other two cases.Also,adding more stations in a regional network shows almost no improvements on the satellite orbits if the number of stations is more than 16.With the help of ISL observations,however,the satellite orbits determined with a small regional network can reach the same accuracy as that with the global network of 60 stations.Furthermore,satellite biases can be well estimated(less than 0.6 mm)and have nearly no impact on satellite orbits.It does thus not matter if they are not physically calibrated for estimating precise orbits.

基于有源超表面天线罩的窄截面方向图可重构天线

针对无人机数据链通信存在抗干扰性能差、防捕获能力弱等问题,提出了一种具有良好气动性能的基于有源超表面天线罩的窄截面方向图可重构天线。该天线由宽带平面印刷全向天线、窄截面有源超表面天线罩以及双频阻抗匹配网络组成。当超表面天线罩上二极管均截止(未加偏置电压)时,天线罩处于全透波状态,天线工作于宽带全向通信模式。当超表面天线罩特定区域二极管导通时,该区域天线罩处于全屏蔽状态,天线工作于双频定向通信模式,此时通过引入双频阻抗匹配网络显著改善天线的阻抗匹配。全向通信模式下,天线相对带宽达到44.6%,全向增益可达1.37 dBi,不圆度小于2.5 dBi;定向模式下,双频天线上下频带分别为1.4 GHz和1.8 GHz,相对带宽分别为9.1%和15.3%,最大定向增益达5.2 dBi。该天线具有窄截面、低成本等优点,能够在宽带全向通信和双频定向通信工作模式之间灵活切换,有望提高无人机抗干扰、防捕获的性能。

无人机机载测控天线自动选择算法

中大型无人机通常配备多幅天线来降低机体遮挡和空域覆盖不够的影响,传统地面测控站手动选择天线的方式存在准确性不高、时效性差、占用操控员精力等缺点。分析了先进无人机测控链路架构,提出基于无源天线方向图的自动天线选择算法,通过实测或仿真天线增益数据形成拟合曲线,根据地面站投影在飞机坐标系下的方位俯仰实现自适应天线选择。针对有源相控阵或定向天线,提出机体坐标系到相控阵天线坐标系的转换矩阵和波束指向算法。给出测控直扩波形信噪比计算方法,将信号质量算法作为卫星导航失效情况下自动天线选择的备份手段。所提算法在准确性、时效性和自动化水平上相对传统手动方式有较大提升,飞行试验数据表明本文算法有效支撑无人机与测控站的稳定可靠通信。

一种用于数据链定向增强功能的相控阵天线

结合现代战争对抗现状和需求,针对强干扰和通信距离扩展需求等典型应用,提出了数据链的定向增强方案,给出了相控阵天线的增益指标,对常见的几种天线形式进行了分析,对天线方向图进行了仿真,提出了校准子系统的设计思路。

多天线系统应用在无人卫星通信链路中的性能研究

随着无人卫星通信链路的发展,其信号衰减、干扰和链路可靠性成为关注焦点。深入探讨多天线系统在无人卫星通信链路中的应用,分析信道模型及其干扰,进而研究多天线系统的核心原理,如空时编码和多输入多输出(Multiple Input Multiple Output,MIMO)技术,并设计基于多天线的协议,强调其在信道估计和调制编码的重要性。实验对比表明,多天线系统在信号质量和传输速率上明显优于单天线系统,但在实际应用中还面临硬件和兼容性挑战。