In offshore maritime communication sys-tems,base stations(BSs)are employed along the coastline to provide high-speed data service for ves-sels in coastal sea areas.To ensure the line-of-sight propagation of BS-vessel ...In offshore maritime communication sys-tems,base stations(BSs)are employed along the coastline to provide high-speed data service for ves-sels in coastal sea areas.To ensure the line-of-sight propagation of BS-vessel links,high transceiver an-tenna height is required,which limits the number of geographically available sites for BS deployment,and imposes a high cost for realizing effective wide-area coverage.In this paper,the joint user association and power allocation(JUAPA)problem is investigated to enhance the coverage of offshore maritime systems.By exploiting the characteristics of network topology as well as vessels’motion in offshore communica-tions,a multi-period JUAPA problem is formulated to maximize the number of ships that can be simultane-ously served by the network.This JUAPA problem is intrinsically non-convex and subject to mixed-integer constraints,which is difficult to solve either analyt-ically or numerically.Hence,we propose an iterative augmentation based framework to efficiently select the active vessels,where the JUAPA scheme is iteratively optimized by the network for increasing the number of the selected vessels.More specifically,in each itera-tion,the user association variables and power alloca-tion variables are determined by solving two separate subproblems,so that the JUAPA strategy can be up-dated in a low-complexity manner.The performance of the proposed JUAPA method is evaluated by exten-sive simulation,and numerical results indicate that it can effectively increase the number of vessels served by the network,and thus enhances the coverage of off-shore systems.展开更多
Evacuated Tube Transportation(ETT)systems have been claimed to have considerable strengths,including ultra-highspeed,safety,and environmentally-friendly.However,the frequent handover caused by the high-speed brings a ...Evacuated Tube Transportation(ETT)systems have been claimed to have considerable strengths,including ultra-highspeed,safety,and environmentally-friendly.However,the frequent handover caused by the high-speed brings a challenge for ETT mobile wireless communication to preserve steady link performance.Moreover,in such a special scenario,the wireless link between the base station and the passengers on the train needs to experience fading from both metal pipe and train,thus the free-wave coverage with antennas in traditional high-speed rail wireless communication systems is not suitable for ETT.Based on the characteristics of ETT,an improved architecture of wireless communication network is proposed,using distributed base stations with remote radio units(RRUs)and baseband units(BBUs)and leaky waveguides to form stable coverage.And a redundant BBUs or RRUs structure is designed for coverage enhancement.Based on this redundant architecture,a fast handover scheme is proposed to resolve the handover problem.The analytical and simulation results show that the proposed scheme is capable of reducing communication outage probability and handover failure probability remarkably.展开更多
Consistent bio-optical properties across multiple ocean color satellites are the key prerequisite to merging products from these satellites,thereby enhancing spatial coverage and extending temporal spans.However,due t...Consistent bio-optical properties across multiple ocean color satellites are the key prerequisite to merging products from these satellites,thereby enhancing spatial coverage and extending temporal spans.However,due to factors such as sensor specifics and separate data processing algorithms,bio-optical properties(e.g.,remote sensing reflectance,R_(rs))from different ocean color missions exhibit varying discrepancies in oceanic,coastal,and inland waters.Here,we introduce a cross-satellite atmospheric correction(CSAC)scheme,which could greatly improve the consistency of R_(rs)products between MODIS-Aqua and other satellite ocean color missions.Specifically,using an inclusive high-quality R_(rs)dataset of oceanic waters obtained from MODIS-Aqua as the reference,and as an example,top-of-atmosphere reflectance from SeaWiFS(Sea-Viewing Wide Field-of-View Sensor)is directly processed to MODIS-Aqua-equivalent R_(rs)(R^(MA−eqv)_(rs))via CSAC.As a demonstration,for independent space-time matched measurements between MODIS-Aqua and SeaWiFS,the mean absolute percent difference(MAPD)between RMA−eqv rs and MODIS-Aqua R_(rs)ranges from 5.9%to 22.2%across wavelengths from 412 to 667 nm.In contrast,the MAPD values between the NASA standard SeaWiFS and MODIS-Aqua R_(rs)products range from 10.1%to 55.1%for the same spectral bands.These results highlight the potential of CSAC in obtaining consistent R_(rs)products and,subsequently,R_(rs)-derived bio-optical properties,from various ocean color satellites,facilitating extensive and long-term ocean color observations of the global ocean.展开更多
基金supported by the National Key Research and Development Program of China under Grant 2018YFA0701601by the Program of Jiangsu Province under Grant NTACT-2024-Z-001.
文摘In offshore maritime communication sys-tems,base stations(BSs)are employed along the coastline to provide high-speed data service for ves-sels in coastal sea areas.To ensure the line-of-sight propagation of BS-vessel links,high transceiver an-tenna height is required,which limits the number of geographically available sites for BS deployment,and imposes a high cost for realizing effective wide-area coverage.In this paper,the joint user association and power allocation(JUAPA)problem is investigated to enhance the coverage of offshore maritime systems.By exploiting the characteristics of network topology as well as vessels’motion in offshore communica-tions,a multi-period JUAPA problem is formulated to maximize the number of ships that can be simultane-ously served by the network.This JUAPA problem is intrinsically non-convex and subject to mixed-integer constraints,which is difficult to solve either analyt-ically or numerically.Hence,we propose an iterative augmentation based framework to efficiently select the active vessels,where the JUAPA scheme is iteratively optimized by the network for increasing the number of the selected vessels.More specifically,in each itera-tion,the user association variables and power alloca-tion variables are determined by solving two separate subproblems,so that the JUAPA strategy can be up-dated in a low-complexity manner.The performance of the proposed JUAPA method is evaluated by exten-sive simulation,and numerical results indicate that it can effectively increase the number of vessels served by the network,and thus enhances the coverage of off-shore systems.
基金the fundamental Research Funds for Central Universities under Grant 2018JBZ102.
文摘Evacuated Tube Transportation(ETT)systems have been claimed to have considerable strengths,including ultra-highspeed,safety,and environmentally-friendly.However,the frequent handover caused by the high-speed brings a challenge for ETT mobile wireless communication to preserve steady link performance.Moreover,in such a special scenario,the wireless link between the base station and the passengers on the train needs to experience fading from both metal pipe and train,thus the free-wave coverage with antennas in traditional high-speed rail wireless communication systems is not suitable for ETT.Based on the characteristics of ETT,an improved architecture of wireless communication network is proposed,using distributed base stations with remote radio units(RRUs)and baseband units(BBUs)and leaky waveguides to form stable coverage.And a redundant BBUs or RRUs structure is designed for coverage enhancement.Based on this redundant architecture,a fast handover scheme is proposed to resolve the handover problem.The analytical and simulation results show that the proposed scheme is capable of reducing communication outage probability and handover failure probability remarkably.
基金support from the National Natural Science Foundation of China(#42430107 and#42250710150)the National Key Research and Development Program of China(2022YFC3104903)Fujian Satellite Data Development,Co.,Ltd.,and Fujian Haisi Digital Technology Co.,Ltd.
文摘Consistent bio-optical properties across multiple ocean color satellites are the key prerequisite to merging products from these satellites,thereby enhancing spatial coverage and extending temporal spans.However,due to factors such as sensor specifics and separate data processing algorithms,bio-optical properties(e.g.,remote sensing reflectance,R_(rs))from different ocean color missions exhibit varying discrepancies in oceanic,coastal,and inland waters.Here,we introduce a cross-satellite atmospheric correction(CSAC)scheme,which could greatly improve the consistency of R_(rs)products between MODIS-Aqua and other satellite ocean color missions.Specifically,using an inclusive high-quality R_(rs)dataset of oceanic waters obtained from MODIS-Aqua as the reference,and as an example,top-of-atmosphere reflectance from SeaWiFS(Sea-Viewing Wide Field-of-View Sensor)is directly processed to MODIS-Aqua-equivalent R_(rs)(R^(MA−eqv)_(rs))via CSAC.As a demonstration,for independent space-time matched measurements between MODIS-Aqua and SeaWiFS,the mean absolute percent difference(MAPD)between RMA−eqv rs and MODIS-Aqua R_(rs)ranges from 5.9%to 22.2%across wavelengths from 412 to 667 nm.In contrast,the MAPD values between the NASA standard SeaWiFS and MODIS-Aqua R_(rs)products range from 10.1%to 55.1%for the same spectral bands.These results highlight the potential of CSAC in obtaining consistent R_(rs)products and,subsequently,R_(rs)-derived bio-optical properties,from various ocean color satellites,facilitating extensive and long-term ocean color observations of the global ocean.
