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 research explores media users＇ cognition of ＂time＂ and ＂space＂ across different media platforms, and conducts a comparison among media genres including mass media and intemet media based on user＇s interacti...This research explores media users＇ cognition of ＂time＂ and ＂space＂ across different media platforms, and conducts a comparison among media genres including mass media and intemet media based on user＇s interactivities. Especially, this research focused on the internet＇s space and time perception based on communication genres such as e-mail, Blogs, portals, news-media, e-commerce, and social media （SNS）. The research adopted two theories （construal level theory of time and space）. The time related theory is ＂temporal distance theory＂. The space related theory is ＂media space＂. The research is designed to measure user＇s perception of interactivity, time-construal level and its media space cognition while using the media. There are two independent variables： Interactivities （contents, user, and media levels） and user involvement （CMC-user vs. user, HCI-user vs. media）; there are two dependent variables： Cognition of spatial and temporal levels. This research also seeks the associated variables relationship among those variables through the structural equation model （SEM）. The 307 data was collected and analyzed to test the research question. The results show that the dimension of the media side＇s interactivity affected media＇s usage time and space perception. There are 2 ~ 2 factors variables to affect time and space. One is human and media interaction （HC1） and human to human communication （CMC）; the other is traditional mass media （one-way communication） and interuet media （two-ways communication）. The results prove the user＇s perception for media time and space is based on the levels of interactivity. The levels of interactivities depend on media usage： one-one, one-many, synchronous, asynchronous, interpersonal, and social network communication. Online media provides greater social space; while traditional media tends toward para-space perception. On the other hand, the users＇ time cognitions between online media are different such as fixed time versus cyber-time.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
This paper presents a new spatial steganography model for covert communications over voice over internet protocol(Vo IP), providing a solution to the issue of increasing the capacity of covert Vo IP channels without c...This paper presents a new spatial steganography model for covert communications over voice over internet protocol(Vo IP), providing a solution to the issue of increasing the capacity of covert Vo IP channels without compromising the imperceptibility of the channels. Drawing from Orthogonal Modulation Theory in communications, the model introduced two concepts, orthogonal data hiding features and data hiding vectors, to covert Vo IP communications. By taking into account the variation characteristics of Vo IP audio streams in the time domain, a hiding vector negotiation mechanism was suggested to achieve dynamic self-adaptive steganography in media streams. Experimental results on Vo IP steganography show that the proposed steganographic method effectively depicted the spatial and temporal characteristics of Vo IP audio streams, and enhanced robustness against detection of steganalysis tools, thereby improving the security of covert Vo IP communications.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.
文摘This research explores media users＇ cognition of ＂time＂ and ＂space＂ across different media platforms, and conducts a comparison among media genres including mass media and intemet media based on user＇s interactivities. Especially, this research focused on the internet＇s space and time perception based on communication genres such as e-mail, Blogs, portals, news-media, e-commerce, and social media （SNS）. The research adopted two theories （construal level theory of time and space）. The time related theory is ＂temporal distance theory＂. The space related theory is ＂media space＂. The research is designed to measure user＇s perception of interactivity, time-construal level and its media space cognition while using the media. There are two independent variables： Interactivities （contents, user, and media levels） and user involvement （CMC-user vs. user, HCI-user vs. media）; there are two dependent variables： Cognition of spatial and temporal levels. This research also seeks the associated variables relationship among those variables through the structural equation model （SEM）. The 307 data was collected and analyzed to test the research question. The results show that the dimension of the media side＇s interactivity affected media＇s usage time and space perception. There are 2 ~ 2 factors variables to affect time and space. One is human and media interaction （HC1） and human to human communication （CMC）; the other is traditional mass media （one-way communication） and interuet media （two-ways communication）. The results prove the user＇s perception for media time and space is based on the levels of interactivity. The levels of interactivities depend on media usage： one-one, one-many, synchronous, asynchronous, interpersonal, and social network communication. Online media provides greater social space; while traditional media tends toward para-space perception. On the other hand, the users＇ time cognitions between online media are different such as fixed time versus cyber-time.
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.
基金supported by the National Natural Science Foundation of China(Grant Nos.61271392U1405254&61272469)the British Government(Grant No.ktp008263)
文摘This paper presents a new spatial steganography model for covert communications over voice over internet protocol(Vo IP), providing a solution to the issue of increasing the capacity of covert Vo IP channels without compromising the imperceptibility of the channels. Drawing from Orthogonal Modulation Theory in communications, the model introduced two concepts, orthogonal data hiding features and data hiding vectors, to covert Vo IP communications. By taking into account the variation characteristics of Vo IP audio streams in the time domain, a hiding vector negotiation mechanism was suggested to achieve dynamic self-adaptive steganography in media streams. Experimental results on Vo IP steganography show that the proposed steganographic method effectively depicted the spatial and temporal characteristics of Vo IP audio streams, and enhanced robustness against detection of steganalysis tools, thereby improving the security of covert Vo IP communications.
