Antenna Group Delay Variation(AGDV)is a hardware error source that affects the performance of Dual-Frequency Multi-Constellation(DFMC)Ground-based Augmentation System(GBAS),and these errors are difficult to distinguis...Antenna Group Delay Variation(AGDV)is a hardware error source that affects the performance of Dual-Frequency Multi-Constellation(DFMC)Ground-based Augmentation System(GBAS),and these errors are difficult to distinguish from multipath errors.Currently,AGDV is usually modeled as a part of the multipath error,which is called the multipath-AGDV model.However,because of the inconsistency of AGDV and multipath when switching among different positioning modes of GBAS,and because the traditional model does not consider the impact of the azimuth on AGDV,using the traditional multipath-AGDV model will cause the protection levels to be inaccurately calculated.In this paper,azimuth-based modeling of AGDV is conducted by using anechoic chamber measurements.The biases and standard deviations of AGDV based on azimuths are analyzed and modeled,and the calculation method for the DFMC GBAS protection level is optimized.The results show that the azimuth-based AGDV model and protection level optimization algorithm can better avoid the error exceeding the protection level than the multipath-AGDV model.Compared with AGDV elevation model,the VPLs of the B1C signal are increased by 0.24 m and 0.06 m,and the VPLs of the B2a signal are reduced by 0.01 m and 0.16 m using the 100 s and 600 s DFree filtering positioning modes,respectively.The changes in the B1C and B2a protection levels reflect the changes in AGDV corresponding to the azimuth for the respective frequencies,further ensuring the integrity of airborne users,especially when they turn near the airport.展开更多
Delay and throughput are the two network indicators that users most care about.Traditional congestion control methods try to occupy buffer aggressively until packet loss being detected,causing high delay and variation...Delay and throughput are the two network indicators that users most care about.Traditional congestion control methods try to occupy buffer aggressively until packet loss being detected,causing high delay and variation.Using AQM and ECN can highly reduce packet drop rate and delay,however they may also lead to low utilization.Managing queue size of routers properly means a lot to congestion control method.Keeping traffic size varying around bottleneck bandwidth creates some degree of persistent queue in the router,which brings in additional delay into network unwillingly,but a corporation between sender and router can keep it under control.Proper persistent queue not only keeps routers being fully utilized all the time,but also lower the variation of throughput and delay,achieving the balance between delay and utilization.In this paper,we present BCTCP(Buffer Controllable TCP),a congestion control protocol based on explicit feedback from routers.It requires sender,receiver and routers cooperating with each other,in which senders adjust their sending rate according to the multiple bit load factor information from routers.It keeps queue length of bottleneck under control,leading to very good delay and utilization result,making it more applicable to complex network environments.展开更多
Differing from the source oriented algorithms, the Core Based Tree (CBT) multicast routing architecture establishes a single shared tree for multiple connections on a multicast group, which results in higher ratio of ...Differing from the source oriented algorithms, the Core Based Tree (CBT) multicast routing architecture establishes a single shared tree for multiple connections on a multicast group, which results in higher ratio of network resources utilization. In alluding to the problem of Core Placement, we propose a simple method (QOCP) to locate an optimal core node, which can minimize the multicast delay and inter destination delay variation simultaneously. The simulation results show that our method is very effective, and outperforms the other algorithms studied in this paper.展开更多
A class of networked control systems is investigated whose communication network is shared with other applications. The design objective for such a system setting is not only the optimization of the control performanc...A class of networked control systems is investigated whose communication network is shared with other applications. The design objective for such a system setting is not only the optimization of the control performance but also the efficient utilization of the communication resources. We observe that at a large time scale the data packet delay in the communication network is roughly varying piecewise constant, which is typically true for data networks like the Internet. Based on this observation, a dynamic data packing scheme is proposed within the recently developed packet-based control framework for networked control systems. As expected this proposed approach achieves a fine balance between the control performance and the communication utilization: the similar control performance can be obtained at dramatically reduced cost of the communication resources. Simulations illustrate the effectiveness of the proposed approach.展开更多
基金the National Key Research and Development Program of China(No.2023YFB3907001)the financial support from the National Natural Science Foundation of China(Nos.62371029,U2233217 and 62101019)the Civil Aviation Security Capacity Building Fund Project of China(Nos.CAAC Contract 2021(77)and CAAC Contract 2022(110)).
文摘Antenna Group Delay Variation(AGDV)is a hardware error source that affects the performance of Dual-Frequency Multi-Constellation(DFMC)Ground-based Augmentation System(GBAS),and these errors are difficult to distinguish from multipath errors.Currently,AGDV is usually modeled as a part of the multipath error,which is called the multipath-AGDV model.However,because of the inconsistency of AGDV and multipath when switching among different positioning modes of GBAS,and because the traditional model does not consider the impact of the azimuth on AGDV,using the traditional multipath-AGDV model will cause the protection levels to be inaccurately calculated.In this paper,azimuth-based modeling of AGDV is conducted by using anechoic chamber measurements.The biases and standard deviations of AGDV based on azimuths are analyzed and modeled,and the calculation method for the DFMC GBAS protection level is optimized.The results show that the azimuth-based AGDV model and protection level optimization algorithm can better avoid the error exceeding the protection level than the multipath-AGDV model.Compared with AGDV elevation model,the VPLs of the B1C signal are increased by 0.24 m and 0.06 m,and the VPLs of the B2a signal are reduced by 0.01 m and 0.16 m using the 100 s and 600 s DFree filtering positioning modes,respectively.The changes in the B1C and B2a protection levels reflect the changes in AGDV corresponding to the azimuth for the respective frequencies,further ensuring the integrity of airborne users,especially when they turn near the airport.
基金supported in part by the National Key R&D Program of China(2018YFB1800602)the Ministry of Education-China Mobile Research Fund Project(MCM20180506)the CERNET Innovation Project(NGIICS20190101)and(NGII20170406)。
文摘Delay and throughput are the two network indicators that users most care about.Traditional congestion control methods try to occupy buffer aggressively until packet loss being detected,causing high delay and variation.Using AQM and ECN can highly reduce packet drop rate and delay,however they may also lead to low utilization.Managing queue size of routers properly means a lot to congestion control method.Keeping traffic size varying around bottleneck bandwidth creates some degree of persistent queue in the router,which brings in additional delay into network unwillingly,but a corporation between sender and router can keep it under control.Proper persistent queue not only keeps routers being fully utilized all the time,but also lower the variation of throughput and delay,achieving the balance between delay and utilization.In this paper,we present BCTCP(Buffer Controllable TCP),a congestion control protocol based on explicit feedback from routers.It requires sender,receiver and routers cooperating with each other,in which senders adjust their sending rate according to the multiple bit load factor information from routers.It keeps queue length of bottleneck under control,leading to very good delay and utilization result,making it more applicable to complex network environments.
文摘Differing from the source oriented algorithms, the Core Based Tree (CBT) multicast routing architecture establishes a single shared tree for multiple connections on a multicast group, which results in higher ratio of network resources utilization. In alluding to the problem of Core Placement, we propose a simple method (QOCP) to locate an optimal core node, which can minimize the multicast delay and inter destination delay variation simultaneously. The simulation results show that our method is very effective, and outperforms the other algorithms studied in this paper.
基金supported by the National Natural Science Foundation of China(Grant Nos.6142230761174061&61304048)+4 种基金the Scientific Research Starting Foundation for the Returned Overseas Chinese Scholars,Ministry of Education of Chinathe National Hi-Tech Research and Development Program of China("863"Project)(Grant No.2014AA06A503)the Youth Innovation Promotion Association,Chinese Academy of Sciences,in part by the Youth Top-Notch Talent Support Programthe 1000-Talent Youth ProgramZhejiang 1000-Talent Program
文摘A class of networked control systems is investigated whose communication network is shared with other applications. The design objective for such a system setting is not only the optimization of the control performance but also the efficient utilization of the communication resources. We observe that at a large time scale the data packet delay in the communication network is roughly varying piecewise constant, which is typically true for data networks like the Internet. Based on this observation, a dynamic data packing scheme is proposed within the recently developed packet-based control framework for networked control systems. As expected this proposed approach achieves a fine balance between the control performance and the communication utilization: the similar control performance can be obtained at dramatically reduced cost of the communication resources. Simulations illustrate the effectiveness of the proposed approach.
