Low-Earth-Orbit satellite constellation networks(LEO-SCN)can provide low-cost,largescale,flexible coverage wireless communication services.High dynamics and large topological sizes characterize LEO-SCN.Protocol develo...Low-Earth-Orbit satellite constellation networks(LEO-SCN)can provide low-cost,largescale,flexible coverage wireless communication services.High dynamics and large topological sizes characterize LEO-SCN.Protocol development and application testing of LEO-SCN are challenging to carry out in a natural environment.Simulation platforms are a more effective means of technology demonstration.Currently available simulators have a single function and limited simulation scale.There needs to be a simulator for full-featured simulation.In this paper,we apply the parallel discrete-event simulation technique to the simulation of LEO-SCN to support large-scale complex system simulation at the packet level.To solve the problem that single-process programs cannot cope with complex simulations containing numerous entities,we propose a parallel mechanism and algorithms LP-NM and LP-YAWNS for synchronization.In the experiment,we use ns-3 to verify the acceleration ratio and efficiency of the above algorithms.The results show that our proposed mechanism can provide parallel simulation engine support for the LEO-SCN.展开更多
This paper addresses the problem of sensor search scheduling in the complicated space environment faced by the low-earth orbit constellation.Several search scheduling methods based on the commonly used information gai...This paper addresses the problem of sensor search scheduling in the complicated space environment faced by the low-earth orbit constellation.Several search scheduling methods based on the commonly used information gain are compared via simulations first.Then a novel search scheduling method in the scenarios of uncertainty observation is proposed based on the global Shannon information gain and beta density based uncertainty model.Simulation results indicate that the beta density model serves a good option for solving the problem of target acquisition in the complicated space environments.展开更多
A dynamic multi-beam resource allocation algorithm for large low Earth orbit(LEO)constellation based on on-board distributed computing is proposed in this paper.The allocation is a combinatorial optimization process u...A dynamic multi-beam resource allocation algorithm for large low Earth orbit(LEO)constellation based on on-board distributed computing is proposed in this paper.The allocation is a combinatorial optimization process under a series of complex constraints,which is important for enhancing the matching between resources and requirements.A complex algorithm is not available because that the LEO on-board resources is limi-ted.The proposed genetic algorithm(GA)based on two-dimen-sional individual model and uncorrelated single paternal inheri-tance method is designed to support distributed computation to enhance the feasibility of on-board application.A distributed system composed of eight embedded devices is built to verify the algorithm.A typical scenario is built in the system to evalu-ate the resource allocation process,algorithm mathematical model,trigger strategy,and distributed computation architec-ture.According to the simulation and measurement results,the proposed algorithm can provide an allocation result for more than 1500 tasks in 14 s and the success rate is more than 91%in a typical scene.The response time is decreased by 40%com-pared with the conditional GA.展开更多
Survivability is used to evaluate the ability of the satellite to complete the mission after failure,while the duration of maintaining performance is often ignored.An effective backup strategy can restore the constell...Survivability is used to evaluate the ability of the satellite to complete the mission after failure,while the duration of maintaining performance is often ignored.An effective backup strategy can restore the constellation performance timely,and maintain good network communication performance in case of satellite failure.From the perspective of network utility,the low Earth orbit(LEO)satellite constellation survivable graphical eva-luation and review technology(GERT)network with backup satel-lites is constructed.A network utility transfer function algorithm based on moment generating function and Mason formula is proposed,the network survivability evaluation models of on-orbit backup strategy and ground backup strategy are established.The survivable GERT model can deduce the expected mainte-nance time of LEO satellite constellation under different fault states and the network utility generated during the state mainte-nance period.The case analysis shows that the proposed surviv-able GERT model can consider the satellite failure rate,backup satellite replacement rate,maneuver control replacement ability and life requirement,and effectively determine the optimal sur-vivable backup strategy for LEO satellite constellation with limi-ted resources according to the expected network utility.展开更多
In the design problem of low earth orbit(LEO) reconnaissance satellite constellation, optimization of coverage performance is the design goal in most current methods. However,in the using process, the user only concer...In the design problem of low earth orbit(LEO) reconnaissance satellite constellation, optimization of coverage performance is the design goal in most current methods. However,in the using process, the user only concerns with the detection capabilities rather than coverage performance. To establish the relationship between these two aspects, the reconnaissance processes of normal stochastic targets are considered and the mathematic models of detection processes are built. The indicators of coverage performance are used to evaluate the detection probability and expectation of detection time delay, which are important factors in reconnaissance constellation estimation viewed from military intelligence discipline. The conclusions confirmed by the final simulation will be useful in LEO reconnaissance constellation design, optimization and evaluation.展开更多
This paper discusses the significance and prospects of low altitude small satellite aerial vehicles to ensure smooth aerial-ground communications for next-generation broadband networks.To achieve the generic goals of ...This paper discusses the significance and prospects of low altitude small satellite aerial vehicles to ensure smooth aerial-ground communications for next-generation broadband networks.To achieve the generic goals of fifthgeneration and beyondwireless networks,the existing aerial network architecture needs to be revisited.The detailed architecture of low altitude aerial networks and the challenges in resource management have been illustrated in this paper.Moreover,we have studied the coordination between promising communication technologies and low altitude aerial networks to provide robust network coverage.We talk about the techniques that can ensure userfriendly control and monitoring of the low altitude aerial networks to bring forth wireless broadband connectivity to a new dimension.In the end,we highlight the future research directions of aerial-ground communications in terms of access technologies,machine learning,compressed sensing,and quantum communications.展开更多
A novel distributed packet routing algorithm for Low Earth Orbit (LEO) satellite networks based on spiderweb topology is presented. The algorithm gives the shortest path with very low computational complexity and with...A novel distributed packet routing algorithm for Low Earth Orbit (LEO) satellite networks based on spiderweb topology is presented. The algorithm gives the shortest path with very low computational complexity and without on-board routing tables, which is suitable and practical for on-board processing. Simulation results show its practicability and feasibility.展开更多
A new handover strategy named minimal-hops handover(MHH) strategy for the lowearth orbit(LEO) satellite constellations networks equipped with inter-satellite links(ISLs) is proposed.MHH strategy,which is based on the ...A new handover strategy named minimal-hops handover(MHH) strategy for the lowearth orbit(LEO) satellite constellations networks equipped with inter-satellite links(ISLs) is proposed.MHH strategy,which is based on the hops of the end-to-end connection paths and makes good use of theregularity of the constellation network topology,can appropriately combine the handover procedure withrouting and efficiently solve the inter-satellite handover issue.Moreover,MHH strategy can providequality of services(QoS) guarantees to some extent.The system performances of the MHH strategy,suchas time propagation delay and handover frequency,are evaluated and compared with that of otherprevious strategies.The simulation results show that MHH strategy performs better than other previoushandover strategies.展开更多
By deploying the ubiquitous and reliable coverage of low Earth orbit(LEO)satellite networks using optical inter satel-lite link(OISL),computation offloading services can be provided for any users without proximal serv...By deploying the ubiquitous and reliable coverage of low Earth orbit(LEO)satellite networks using optical inter satel-lite link(OISL),computation offloading services can be provided for any users without proximal servers,while the resource limita-tion of both computation and storage on satellites is the impor-tant factor affecting the maximum task completion time.In this paper,we study a delay-optimal multi-satellite collaborative computation offloading scheme that allows satellites to actively migrate tasks among themselves by employing the high-speed OISLs,such that tasks with long queuing delay will be served as quickly as possible by utilizing idle computation resources in the neighborhood.To satisfy the delay requirement of delay-sensi-tive task,we first propose a deadline-aware task scheduling scheme in which a priority model is constructed to sort the order of tasks being served based on its deadline,and then a delay-optimal collaborative offloading scheme is derived such that the tasks which cannot be completed locally can be migrated to other idle satellites.Simulation results demonstrate the effective-ness of our multi-satellite collaborative computation offloading strategy in reducing task complement time and improving resource utilization of the LEO satellite network.展开更多
A Low Earth Orbit(LEO)constellation augmenting satellite navigation is important in the future development of Global Navigation Satellite System(GNSS).GNSS augmented by LEO constellations can improve not only the accu...A Low Earth Orbit(LEO)constellation augmenting satellite navigation is important in the future development of Global Navigation Satellite System(GNSS).GNSS augmented by LEO constellations can improve not only the accuracy of Positioning,Navigation,and Timing(PNT),but also the consistency and reliability of secure PNT system.This paper mainly analyzes the diverse demands of different PNT users for LEO augmented GNSS,including the precision demand in real-time,the availability demand in special areas,the navigation signal enhancement demand in complex electromagnetic environments,and the integrity demand with high security.Correspondingly,the possible contributions of LEO constellations to PNT performance are analyzed from multiple aspects.A particular attention is paid to the special PNT user requirements that cannot be fulfilled with existing GNSS,such as the PNT service demand in the polar regions and the onboard GNSS orbit determination demand of some LEO satellites.The key technologies to be considered in the constellation design,function realization,and payload development of the LEO-augmented navigation system are summarized.展开更多
基金supported by Jiangsu Provincial Key Research and Development Program (No.BE20210132)the Zhejiang Provincial Key Research and Development Program (No.2021C01040)the team of S-SET
文摘Low-Earth-Orbit satellite constellation networks(LEO-SCN)can provide low-cost,largescale,flexible coverage wireless communication services.High dynamics and large topological sizes characterize LEO-SCN.Protocol development and application testing of LEO-SCN are challenging to carry out in a natural environment.Simulation platforms are a more effective means of technology demonstration.Currently available simulators have a single function and limited simulation scale.There needs to be a simulator for full-featured simulation.In this paper,we apply the parallel discrete-event simulation technique to the simulation of LEO-SCN to support large-scale complex system simulation at the packet level.To solve the problem that single-process programs cannot cope with complex simulations containing numerous entities,we propose a parallel mechanism and algorithms LP-NM and LP-YAWNS for synchronization.In the experiment,we use ns-3 to verify the acceleration ratio and efficiency of the above algorithms.The results show that our proposed mechanism can provide parallel simulation engine support for the LEO-SCN.
基金supported by the National Defense Pre-research Foundation (9140A21041110KG0148)
文摘This paper addresses the problem of sensor search scheduling in the complicated space environment faced by the low-earth orbit constellation.Several search scheduling methods based on the commonly used information gain are compared via simulations first.Then a novel search scheduling method in the scenarios of uncertainty observation is proposed based on the global Shannon information gain and beta density based uncertainty model.Simulation results indicate that the beta density model serves a good option for solving the problem of target acquisition in the complicated space environments.
基金This work was supported by the National Key Research and Development Program of China(2021YFB2900603)the National Natural Science Foundation of China(61831008).
文摘A dynamic multi-beam resource allocation algorithm for large low Earth orbit(LEO)constellation based on on-board distributed computing is proposed in this paper.The allocation is a combinatorial optimization process under a series of complex constraints,which is important for enhancing the matching between resources and requirements.A complex algorithm is not available because that the LEO on-board resources is limi-ted.The proposed genetic algorithm(GA)based on two-dimen-sional individual model and uncorrelated single paternal inheri-tance method is designed to support distributed computation to enhance the feasibility of on-board application.A distributed system composed of eight embedded devices is built to verify the algorithm.A typical scenario is built in the system to evalu-ate the resource allocation process,algorithm mathematical model,trigger strategy,and distributed computation architec-ture.According to the simulation and measurement results,the proposed algorithm can provide an allocation result for more than 1500 tasks in 14 s and the success rate is more than 91%in a typical scene.The response time is decreased by 40%com-pared with the conditional GA.
基金This work was supported by the National Natural Science Foundation of China(72271124,52232014,72071111,71801127,71671091).
文摘Survivability is used to evaluate the ability of the satellite to complete the mission after failure,while the duration of maintaining performance is often ignored.An effective backup strategy can restore the constellation performance timely,and maintain good network communication performance in case of satellite failure.From the perspective of network utility,the low Earth orbit(LEO)satellite constellation survivable graphical eva-luation and review technology(GERT)network with backup satel-lites is constructed.A network utility transfer function algorithm based on moment generating function and Mason formula is proposed,the network survivability evaluation models of on-orbit backup strategy and ground backup strategy are established.The survivable GERT model can deduce the expected mainte-nance time of LEO satellite constellation under different fault states and the network utility generated during the state mainte-nance period.The case analysis shows that the proposed surviv-able GERT model can consider the satellite failure rate,backup satellite replacement rate,maneuver control replacement ability and life requirement,and effectively determine the optimal sur-vivable backup strategy for LEO satellite constellation with limi-ted resources according to the expected network utility.
文摘In the design problem of low earth orbit(LEO) reconnaissance satellite constellation, optimization of coverage performance is the design goal in most current methods. However,in the using process, the user only concerns with the detection capabilities rather than coverage performance. To establish the relationship between these two aspects, the reconnaissance processes of normal stochastic targets are considered and the mathematic models of detection processes are built. The indicators of coverage performance are used to evaluate the detection probability and expectation of detection time delay, which are important factors in reconnaissance constellation estimation viewed from military intelligence discipline. The conclusions confirmed by the final simulation will be useful in LEO reconnaissance constellation design, optimization and evaluation.
文摘This paper discusses the significance and prospects of low altitude small satellite aerial vehicles to ensure smooth aerial-ground communications for next-generation broadband networks.To achieve the generic goals of fifthgeneration and beyondwireless networks,the existing aerial network architecture needs to be revisited.The detailed architecture of low altitude aerial networks and the challenges in resource management have been illustrated in this paper.Moreover,we have studied the coordination between promising communication technologies and low altitude aerial networks to provide robust network coverage.We talk about the techniques that can ensure userfriendly control and monitoring of the low altitude aerial networks to bring forth wireless broadband connectivity to a new dimension.In the end,we highlight the future research directions of aerial-ground communications in terms of access technologies,machine learning,compressed sensing,and quantum communications.
文摘A novel distributed packet routing algorithm for Low Earth Orbit (LEO) satellite networks based on spiderweb topology is presented. The algorithm gives the shortest path with very low computational complexity and without on-board routing tables, which is suitable and practical for on-board processing. Simulation results show its practicability and feasibility.
文摘A new handover strategy named minimal-hops handover(MHH) strategy for the lowearth orbit(LEO) satellite constellations networks equipped with inter-satellite links(ISLs) is proposed.MHH strategy,which is based on the hops of the end-to-end connection paths and makes good use of theregularity of the constellation network topology,can appropriately combine the handover procedure withrouting and efficiently solve the inter-satellite handover issue.Moreover,MHH strategy can providequality of services(QoS) guarantees to some extent.The system performances of the MHH strategy,suchas time propagation delay and handover frequency,are evaluated and compared with that of otherprevious strategies.The simulation results show that MHH strategy performs better than other previoushandover strategies.
基金This work was supported by the National Key Research and Development Program of China(2021YFB2900600)the National Natural Science Foundation of China(61971041+2 种基金62001027)the Beijing Natural Science Foundation(M22001)the Technological Innovation Program of Beijing Institute of Technology(2022CX01027).
文摘By deploying the ubiquitous and reliable coverage of low Earth orbit(LEO)satellite networks using optical inter satel-lite link(OISL),computation offloading services can be provided for any users without proximal servers,while the resource limita-tion of both computation and storage on satellites is the impor-tant factor affecting the maximum task completion time.In this paper,we study a delay-optimal multi-satellite collaborative computation offloading scheme that allows satellites to actively migrate tasks among themselves by employing the high-speed OISLs,such that tasks with long queuing delay will be served as quickly as possible by utilizing idle computation resources in the neighborhood.To satisfy the delay requirement of delay-sensi-tive task,we first propose a deadline-aware task scheduling scheme in which a priority model is constructed to sort the order of tasks being served based on its deadline,and then a delay-optimal collaborative offloading scheme is derived such that the tasks which cannot be completed locally can be migrated to other idle satellites.Simulation results demonstrate the effective-ness of our multi-satellite collaborative computation offloading strategy in reducing task complement time and improving resource utilization of the LEO satellite network.
基金funded by the National Natural Science Foundation of China(Grant No.42388102No.41931076)+1 种基金the National Key Research and Development Program of China(Grant No.2020YFB0505800)the Laoshan Laboratory(Grant No.LSKJ202205101).
文摘A Low Earth Orbit(LEO)constellation augmenting satellite navigation is important in the future development of Global Navigation Satellite System(GNSS).GNSS augmented by LEO constellations can improve not only the accuracy of Positioning,Navigation,and Timing(PNT),but also the consistency and reliability of secure PNT system.This paper mainly analyzes the diverse demands of different PNT users for LEO augmented GNSS,including the precision demand in real-time,the availability demand in special areas,the navigation signal enhancement demand in complex electromagnetic environments,and the integrity demand with high security.Correspondingly,the possible contributions of LEO constellations to PNT performance are analyzed from multiple aspects.A particular attention is paid to the special PNT user requirements that cannot be fulfilled with existing GNSS,such as the PNT service demand in the polar regions and the onboard GNSS orbit determination demand of some LEO satellites.The key technologies to be considered in the constellation design,function realization,and payload development of the LEO-augmented navigation system are summarized.
