ABSTRACT Content distribution and retrieval in opportunistic networks is a promising paradigm due... more ABSTRACT Content distribution and retrieval in opportunistic networks is a promising paradigm due to its large spectrum of potential applications. In particular, routing in this paradigm needs efficient solutions due to the numerous challenges raised by opportunistic networks. In this paper, we introduce and demonstrate the potentiality of the swarm intelligence approach applied for this difficult communication context. First, we formalize the notion of optimal spatio-temporal path in opportunistic networks and propose an algorithm based on the adjacency matrix to compute the length of such path. Based on this definition, we introduce a simple swarm routing protocol which allows nodes in an opportunistic network that use a publish/subscribe communication paradigm to find the optimal path to route content towards subscribers. The protocol works in a decentralized way in which each node does not have any knowledge about the global topology. Via opportunistic contacts nodes update a dynamic scalar value (i.e. an utility function) which synthesizes their spatio-temporal proximity from subscribers of a given content (i.e. how close the node is in space and time to a subscriber of this content). This individual behavior applied by each node leads collectively to the formation of gradient fields between content users and content providers. Therefore, content routing simply sums up to follow the lowest gradient slope along this field to reach the users who are located at the minimum of the field. Via simulations, we demonstrate the existence and relevance of such gradient field and show that in highly sparse and localized networks the spatio-temporal gradient field can stabilize and helps to improve routing performance and resources compared to classical diffusion schemes. This proposition is a first brick towards more sophisticated and high performing swarm optimization techniques applied for opportunistic networks.
This paper introduces a XML-based specification language called XQoS suited to describe the appli... more This paper introduces a XML-based specification language called XQoS suited to describe the application requirements and the available resources of the communication system in terms of quality of service. The design of this language is oriented by the need of a global QoS specification technique able to provide a complete description of applications QoS requirements that can be easily mapped
ABSTRACT Abstract In this work, we propose a modelling framework which captures the most fundamen... more ABSTRACT Abstract In this work, we propose a modelling framework which captures the most fundamental behavioural and structural properties of mobile opportunistic networks from mobility to structural level. First, we introduce Spatio-TEmporal Parametric Stepping (STEPS) – a simple parametric mobility model which can cover a large spectrum of human mobility patterns. STEPS abstracts the fundamental spatio-temporal behaviours of human mobility, i.e., preferential attachment and attractors, by using a power law to drive nodes’ movement. We show that the model makes it possible to express key peer-to-peer properties of opportunistic networks such as inter-contact/contact time distributions. Leveraging on the expressive and modelling power of STEPS, we analyse how fundamental structural properties can emerge from the combination of elementary node’s mobility behaviour. Specifically, we bring out one sufficient condition of the emergence of the famous small-world structure in opportunistic networks. We also show that this special dynamic network structure improves significantly the communication capacity of opportunistic networks.
ABSTRACT The semantics of hypermedia documents depends mainly on the satisfaction of both logical... more ABSTRACT The semantics of hypermedia documents depends mainly on the satisfaction of both logical and temporal synchronization constraints. Therefore, the specification and verification of temporal and logical properties of hypermedia systems is a fundamental stage that must be done before implementation. In this paper we propose a formal model, called HTSPN (Hierar- chical Time Stream Petri Net), that allows a complete and accurate formal specification of both temporal and logical synchronization within hypermedia distributed systems to be done. More- over, this model provides means for the simulation and analysis of hypermedia systems behaviour. In this paper we show, through a case study, the contributions of the HTSPN formal model for hypermedia system design.
ABSTRACT Content distribution and retrieval in opportunistic networks is a promising paradigm due... more ABSTRACT Content distribution and retrieval in opportunistic networks is a promising paradigm due to its large spectrum of potential applications. In particular, routing in this paradigm needs efficient solutions due to the numerous challenges raised by opportunistic networks. In this paper, we introduce and demonstrate the potentiality of the swarm intelligence approach applied for this difficult communication context. First, we formalize the notion of optimal spatio-temporal path in opportunistic networks and propose an algorithm based on the adjacency matrix to compute the length of such path. Based on this definition, we introduce a simple swarm routing protocol which allows nodes in an opportunistic network that use a publish/subscribe communication paradigm to find the optimal path to route content towards subscribers. The protocol works in a decentralized way in which each node does not have any knowledge about the global topology. Via opportunistic contacts nodes update a dynamic scalar value (i.e. an utility function) which synthesizes their spatio-temporal proximity from subscribers of a given content (i.e. how close the node is in space and time to a subscriber of this content). This individual behavior applied by each node leads collectively to the formation of gradient fields between content users and content providers. Therefore, content routing simply sums up to follow the lowest gradient slope along this field to reach the users who are located at the minimum of the field. Via simulations, we demonstrate the existence and relevance of such gradient field and show that in highly sparse and localized networks the spatio-temporal gradient field can stabilize and helps to improve routing performance and resources compared to classical diffusion schemes. This proposition is a first brick towards more sophisticated and high performing swarm optimization techniques applied for opportunistic networks.
This paper introduces a XML-based specification language called XQoS suited to describe the appli... more This paper introduces a XML-based specification language called XQoS suited to describe the application requirements and the available resources of the communication system in terms of quality of service. The design of this language is oriented by the need of a global QoS specification technique able to provide a complete description of applications QoS requirements that can be easily mapped
ABSTRACT Abstract In this work, we propose a modelling framework which captures the most fundamen... more ABSTRACT Abstract In this work, we propose a modelling framework which captures the most fundamental behavioural and structural properties of mobile opportunistic networks from mobility to structural level. First, we introduce Spatio-TEmporal Parametric Stepping (STEPS) – a simple parametric mobility model which can cover a large spectrum of human mobility patterns. STEPS abstracts the fundamental spatio-temporal behaviours of human mobility, i.e., preferential attachment and attractors, by using a power law to drive nodes’ movement. We show that the model makes it possible to express key peer-to-peer properties of opportunistic networks such as inter-contact/contact time distributions. Leveraging on the expressive and modelling power of STEPS, we analyse how fundamental structural properties can emerge from the combination of elementary node’s mobility behaviour. Specifically, we bring out one sufficient condition of the emergence of the famous small-world structure in opportunistic networks. We also show that this special dynamic network structure improves significantly the communication capacity of opportunistic networks.
ABSTRACT The semantics of hypermedia documents depends mainly on the satisfaction of both logical... more ABSTRACT The semantics of hypermedia documents depends mainly on the satisfaction of both logical and temporal synchronization constraints. Therefore, the specification and verification of temporal and logical properties of hypermedia systems is a fundamental stage that must be done before implementation. In this paper we propose a formal model, called HTSPN (Hierar- chical Time Stream Petri Net), that allows a complete and accurate formal specification of both temporal and logical synchronization within hypermedia distributed systems to be done. More- over, this model provides means for the simulation and analysis of hypermedia systems behaviour. In this paper we show, through a case study, the contributions of the HTSPN formal model for hypermedia system design.
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