With the advancements of software defined network(SDN)and network function virtualization(NFV),service function chain(SFC)placement becomes a crucial enabler for flexible resource scheduling in low earth orbit(LEO)sat...With the advancements of software defined network(SDN)and network function virtualization(NFV),service function chain(SFC)placement becomes a crucial enabler for flexible resource scheduling in low earth orbit(LEO)satellite networks.While due to the scarcity of bandwidth resources and dynamic topology of LEO satellites,the static SFC placement schemes may cause performance degradation,resource waste and even service failure.In this paper,we consider migration and establish an online migration model,especially considering the dynamic topology.Given the scarcity of bandwidth resources,the model aims to maximize the total number of accepted SFCs while incurring as little bandwidth cost of SFC transmission and migration as possible.Due to its NP-hardness,we propose a heuristic minimized dynamic SFC migration(MDSM)algorithm that only triggers the migration procedure when new SFCs are rejected.Simulation results demonstrate that MDSM achieves a performance close to the upper bound with lower complexity.展开更多
Recent years have witnessed an explosive growth in mobile video-based services and efficient and reliable video delivery draws more and more attention. As a type of rateless codes, fountain codes can automatically ada...Recent years have witnessed an explosive growth in mobile video-based services and efficient and reliable video delivery draws more and more attention. As a type of rateless codes, fountain codes can automatically adapt to wireless channel conditions with- out any knowledge of channels. This paper provides an overview of several typical Foi-ward Error Correction （FEC） codes, such as Reed-Solomon （RS） code, Tornado code, Luby-Transform （LT） code, and Raptor code. We focus on a novel delay-aware fountain coding （DAF） technique that maxinfizes the code word length under the constraint of a given delay. Based on DAF, this paper also presents Unequal Error Protection DAF （UEP-DAF） which improves the Peak Signal to Noise Ratio （PSNR） without additional co- ordination between the encoder and the decoder, as well as Model Predictive Control DAF （MPC-DAF） which reduces the compu- tational complexity to an affordable level for real-time video comnmnications. Moreover, we review- video streaming technologies, then introduce Dynamic Adaptive Streaming over HTTP （DASH） and DASH over Multiple Content Distribution Servers （MCDS- DASH） in detail. Based on MCDS-DASH that adapts video bitrate at the block level to alleviate video fluctuation, we propose a novel approach to integrating fountain codes with MCDS-DASH, which is capable of achieving unprecedented high throughput.展开更多
Due to rapid development in the past decade, air transportation system has attracted considerable research attention from diverse communities. While most of the previous studies focused on airline networks, here we sy...Due to rapid development in the past decade, air transportation system has attracted considerable research attention from diverse communities. While most of the previous studies focused on airline networks, here we systematically explore the robustness of the Chinese air route network, and identify the vital edges which form the backbone of Chinese air transportation system.Specifically, we employ a memetic algorithm to minimize the network robustness after removing certain edges, and hence the solution of this model is the set of vital edges. Counterintuitively,our results show that the most vital edges are not necessarily the edges of the highest topological importance, for which we provide an extensive explanation from the microscope view. Our findings also offer new insights to understanding and optimizing other real-world network systems.展开更多
In recent years,unmanned aerial vehicles(UAVs)have developed rapidly and UAVs have an expanding range of applications in areas including photography,cargo delivery,inspection,agricultural plant protection and communic...In recent years,unmanned aerial vehicles(UAVs)have developed rapidly and UAVs have an expanding range of applications in areas including photography,cargo delivery,inspection,agricultural plant protection and communications.However,in the face of increasingly complex application environment and diversified demands,the application range of a single UAV is limited by its own hardware and software condition.展开更多
基金supported in part by the National Natural Science Foundation of China(NSFC)under grant numbers U22A2007 and 62171010the Open project of Satellite Internet Key Laboratory in 2022(Project 3:Research on Spaceborne Lightweight Core Network and Intelligent Collaboration)the Beijing Natural Science Foundation under grant number L212003.
文摘With the advancements of software defined network(SDN)and network function virtualization(NFV),service function chain(SFC)placement becomes a crucial enabler for flexible resource scheduling in low earth orbit(LEO)satellite networks.While due to the scarcity of bandwidth resources and dynamic topology of LEO satellites,the static SFC placement schemes may cause performance degradation,resource waste and even service failure.In this paper,we consider migration and establish an online migration model,especially considering the dynamic topology.Given the scarcity of bandwidth resources,the model aims to maximize the total number of accepted SFCs while incurring as little bandwidth cost of SFC transmission and migration as possible.Due to its NP-hardness,we propose a heuristic minimized dynamic SFC migration(MDSM)algorithm that only triggers the migration procedure when new SFCs are rejected.Simulation results demonstrate that MDSM achieves a performance close to the upper bound with lower complexity.
文摘Recent years have witnessed an explosive growth in mobile video-based services and efficient and reliable video delivery draws more and more attention. As a type of rateless codes, fountain codes can automatically adapt to wireless channel conditions with- out any knowledge of channels. This paper provides an overview of several typical Foi-ward Error Correction （FEC） codes, such as Reed-Solomon （RS） code, Tornado code, Luby-Transform （LT） code, and Raptor code. We focus on a novel delay-aware fountain coding （DAF） technique that maxinfizes the code word length under the constraint of a given delay. Based on DAF, this paper also presents Unequal Error Protection DAF （UEP-DAF） which improves the Peak Signal to Noise Ratio （PSNR） without additional co- ordination between the encoder and the decoder, as well as Model Predictive Control DAF （MPC-DAF） which reduces the compu- tational complexity to an affordable level for real-time video comnmnications. Moreover, we review- video streaming technologies, then introduce Dynamic Adaptive Streaming over HTTP （DASH） and DASH over Multiple Content Distribution Servers （MCDS- DASH） in detail. Based on MCDS-DASH that adapts video bitrate at the block level to alleviate video fluctuation, we propose a novel approach to integrating fountain codes with MCDS-DASH, which is capable of achieving unprecedented high throughput.
基金supported by the National Natural Science Foundation of China (Nos. 91538204, 61425014, 61521091)National Key Research and Development Program of China (No. 2016YFB1200100)National Key Technology R&D Program of China (No. 2015BAG15B01)
文摘Due to rapid development in the past decade, air transportation system has attracted considerable research attention from diverse communities. While most of the previous studies focused on airline networks, here we systematically explore the robustness of the Chinese air route network, and identify the vital edges which form the backbone of Chinese air transportation system.Specifically, we employ a memetic algorithm to minimize the network robustness after removing certain edges, and hence the solution of this model is the set of vital edges. Counterintuitively,our results show that the most vital edges are not necessarily the edges of the highest topological importance, for which we provide an extensive explanation from the microscope view. Our findings also offer new insights to understanding and optimizing other real-world network systems.
文摘In recent years,unmanned aerial vehicles(UAVs)have developed rapidly and UAVs have an expanding range of applications in areas including photography,cargo delivery,inspection,agricultural plant protection and communications.However,in the face of increasingly complex application environment and diversified demands,the application range of a single UAV is limited by its own hardware and software condition.
