Delay/Disruption-Tolerant Networking(DTN) originated from research on Interplanetary Internet and still today space applications are the most important application field and research stimulus. This paper investigates ...Delay/Disruption-Tolerant Networking(DTN) originated from research on Interplanetary Internet and still today space applications are the most important application field and research stimulus. This paper investigates DTN communications between the Earth and the far side of the Moon, by means of a lunar orbiter acting as relay. After an introductory part, the paper presents a comprehensive analysis of the DTN performance that can be achieved on the identified communication scenario. The focus is on the evaluation of the stateof-the-art ability of Interplanetary Overlay Network(ION), the NASA DTN implementation of Bundle Protocol(BP) and Contact Graph Routing(CGR), to meet the many challenges of the space communication scenario investigated(and more generally of a future interplaynetary Internet): intermittent links, network partitioning, scarce bandwidth, long delays, dynamic routing, handling of high priority and emergency traffic, interoperability issues. A study of security threats and Bundle Security Protocol(BSP) countermeasures complete the work.The many results provided, confirm the essential role of DTN in future space communications.展开更多
This paper investigates the cross-correlation characteristics of large-scale parameters(LSPs) and small-scale fading(SSF) for high-speed railway(HSR) multilink propagation scenarios, based on realistic measurements co...This paper investigates the cross-correlation characteristics of large-scale parameters(LSPs) and small-scale fading(SSF) for high-speed railway(HSR) multilink propagation scenarios, based on realistic measurements conducted on Beijing to Tianjin HSR line in China. A long-term evolution-based channel sounding system is utilized in the measurements to obtain the channel data. By applying a proposed time-delay based dynamic partition method, multi-link channel impulse responses are extracted from the raw channel data. Then, the statistical results of LSPs, including shadow fading, K-factor, and root-mean-square delay spread are derived and the cross-correlation coefficients of these LPSs are calculated. Moreover, the SSF spatial correlation and cross-correlation of SSF are analyzed. These results can be used to exploit multi-link channel model and to optimize the next-generation HSR communication system.展开更多
The invention of the World Wide Web, especially the Web 2.0, originally led some sociologists to believe that this tool would have favoured the creation of a ＂collective intelligence＂ able to spread and increase the...The invention of the World Wide Web, especially the Web 2.0, originally led some sociologists to believe that this tool would have favoured the creation of a ＂collective intelligence＂ able to spread and increase the level of democracy in the society. Nowadays, as a matter of fact, Information and Communications Technologies （ICTs） continue excluding part of the population and contribute to a top-down organisation of the main streams of information neutralising active potentialities and risking, paradoxically, to isolate users who are not aware of the mechanisms of the lnternet. The ＂doxic＂ acceptance of web contents, structures, and tools indeed precludes some kinds of knowledge and some different models of participation, with significant consequences on the social construction of reality. As a result, a tendency emerges towards a virtual-only participation and the click-tivism seems more and more to be turning into a form of slack-tivism.展开更多
文摘Delay/Disruption-Tolerant Networking(DTN) originated from research on Interplanetary Internet and still today space applications are the most important application field and research stimulus. This paper investigates DTN communications between the Earth and the far side of the Moon, by means of a lunar orbiter acting as relay. After an introductory part, the paper presents a comprehensive analysis of the DTN performance that can be achieved on the identified communication scenario. The focus is on the evaluation of the stateof-the-art ability of Interplanetary Overlay Network(ION), the NASA DTN implementation of Bundle Protocol(BP) and Contact Graph Routing(CGR), to meet the many challenges of the space communication scenario investigated(and more generally of a future interplaynetary Internet): intermittent links, network partitioning, scarce bandwidth, long delays, dynamic routing, handling of high priority and emergency traffic, interoperability issues. A study of security threats and Bundle Security Protocol(BSP) countermeasures complete the work.The many results provided, confirm the essential role of DTN in future space communications.
基金supported by the Beijing Municipal Natural Science Foundation under Grant 4174102the National Natural Science Foundation of China under Grant 61701017+1 种基金the Open Research Fund through the National Mobile Communications Research Laboratory, Southeast University, under Grant 2018D11the Fundamental Research Funds for the Central Universities under Grant 2018JBM003
文摘This paper investigates the cross-correlation characteristics of large-scale parameters(LSPs) and small-scale fading(SSF) for high-speed railway(HSR) multilink propagation scenarios, based on realistic measurements conducted on Beijing to Tianjin HSR line in China. A long-term evolution-based channel sounding system is utilized in the measurements to obtain the channel data. By applying a proposed time-delay based dynamic partition method, multi-link channel impulse responses are extracted from the raw channel data. Then, the statistical results of LSPs, including shadow fading, K-factor, and root-mean-square delay spread are derived and the cross-correlation coefficients of these LPSs are calculated. Moreover, the SSF spatial correlation and cross-correlation of SSF are analyzed. These results can be used to exploit multi-link channel model and to optimize the next-generation HSR communication system.
文摘The invention of the World Wide Web, especially the Web 2.0, originally led some sociologists to believe that this tool would have favoured the creation of a ＂collective intelligence＂ able to spread and increase the level of democracy in the society. Nowadays, as a matter of fact, Information and Communications Technologies （ICTs） continue excluding part of the population and contribute to a top-down organisation of the main streams of information neutralising active potentialities and risking, paradoxically, to isolate users who are not aware of the mechanisms of the lnternet. The ＂doxic＂ acceptance of web contents, structures, and tools indeed precludes some kinds of knowledge and some different models of participation, with significant consequences on the social construction of reality. As a result, a tendency emerges towards a virtual-only participation and the click-tivism seems more and more to be turning into a form of slack-tivism.
