This paper introduces time stream Pdtri nets (TS treamPN), a model for the formal specification o... more This paper introduces time stream Pdtri nets (TS treamPN), a model for the formal specification of multimedia synchronization scenarios. This new model extends time Pdtri nets to formally describe the timed behaviour of multimedia objects and streams in asynchronous distributed systems. The proposed approach uses time intervals to label the arcs exiting from the places of the net, and typed transitions to define different firing rules. This model allows a complete and accurate specification of synchronization constraints between multimedia streams and can be used at different levels of granularity.
2009 Ieee International Symposium on a World of Wireless Mobile and Multimedia Networks Workshops, Jun 15, 2009
WIMAX (Worldwide Interoperability for Microwave Access) is a promising new networking technology ... more WIMAX (Worldwide Interoperability for Microwave Access) is a promising new networking technology that potentially offers high speed and wide area wireless access services that complement consistently the 3G and WiFi access networks capabilities. The standard proposes an adaptive modulation scheme which allows WiMax nodes to communicate from various modulation coding schemes according to the link quality. However, the standard does not define a detailed link adaptation algorithm and currently, the most largely used modulation adaptation technique is based on a channel quality lookup table. We argue that this method is not able to make the best adaptation decisions and delivers a sub-optimal goodput in numerous communication contexts. In this paper, we propose a novel cross layer based modulation adaptation mechanism which incorporates the use of adaptive erasure code with the physical layer information to significantly improve the goodput and transmission efficiency. Simulation results show that our proposal adapts more efficiently to real environments and achieves a significant gain on the goodput delivered to mobile nodes.
Computer Networks the International Journal of Computer and Telecommunications Networking, Oct 1, 2007
In the next generation Internet, the network will evolve from a plain communication medium into o... more In the next generation Internet, the network will evolve from a plain communication medium into one that provides endless services to the users. These services will be composed of multiple cooperative distributed application elements. We name these services overlay applications. The cooperative application elements within an overlay application will build a dynamic communication mesh, namely an overlay association. The Quality of Service (QoS) perceived by the users of an overlay application greatly depends on the QoS experienced on the communication paths of the corresponding overlay association. In this paper, we present super-peer alternate path discovery (SPAD), a distributed middleware architecture that aims at providing enhanced QoS between end-points within an overlay association. To achieve this goal, SPAD provides a complete scheme to discover and utilize composite alternate end-to-end paths with better QoS than the path given by the default IP routing mechanisms.
Ž. A Partial Order and partial reliable Connection POC is an end-to-end transport connection auth... more Ž. A Partial Order and partial reliable Connection POC is an end-to-end transport connection authorized to deliver objects in an order that can differ from the transmitted one. Such a connection is also authorized to lose some objects. The POC concept is motivated by the fact that heterogeneous best-effort networks such as Internet are plagued by unordered delivery of packets and losses, which tax the performances of current applications and protocols. It has been shown, in several Ž. research works, that out of order delivery is able to alleviate with respect to CO service the use of end systems' communication resources. In this paper, the efficiency of out-of-sequence delivery on MPEG video streams processing is Ž. studied. Firstly, the transport constraints in terms of order and reliability that can be relaxed by MPEG video decoders, for improving video transport, are detailed. Then, we analyze the performance gain induced by this approach in terms of blocking times and recovered errors. We demonstrate that POC connections fill not only the conceptual gap between TCP and UDP but also provide real performance improvements for the transport of multimedia streams such MPEG video.
Proceedings of the 5th International Icst Conference, Jul 28, 2008
Congestion control is a fundamental mechanism for the stability of the Internet and is a central ... more Congestion control is a fundamental mechanism for the stability of the Internet and is a central mechanism for TCP. However, this congestion control mechanism focuses mainly on the core network state and is blind to the characteristics of wireless and mobile access networks. Moreover, TCP window based congestion control ignores totally application layer QoS needs and entails throughput variations which are not compliant with application layer QoS constraints such as bandwidth, delay and jitter. The TCP-Friendly Rate Control protocol (TFRC) was originally designed in the context of wired networks. This protocol is one of the most convincing attempt to provide a congestion control mechanism adapted to multimedia flows, although limited in its capacity to fully address these issues. After an identification and evaluation of the subtle counterproductive interactions between the WLANs MAC layer and the transport layer, this paper shows a new approach towards congestion control for WLANs. This paper also introduces a specialization of TFRC (MTFRC: Mobile TFRC), which is adapted to wireless access networks. This TFRC specialization requires only slight changes to the standard TFRC protocol. Simulation results show substantial improvements for applications over TFRC in scenarios where the bottleneck situates on the MAC layer of the mobile nodes.
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.
This paper introduces a STIgmergy based Routing protocol (STIR) for Content Centric Delay Toleran... more This paper introduces a STIgmergy based Routing protocol (STIR) for Content Centric Delay Tolerant Networks. STIR makes the most of spatio-temporal interactions between nodes to set up bio-inspired gradient fields between content producers and content users. STIR routing follows this gradient field to efficiently route information in Delay Tolerant Networks. The validation of this protocol has been coupled with the definition of a new mobility parametric model that makes possible to easily express the preferential locations and movements commonly observed in real human mobility traces. Performance evaluations by simulations demonstrate that STIR delivers better performances than traditional protocols even in case of highly dynamic networks.
Proceedings. Fourth International Conference on Peer-to-Peer Computing, 2004. Proceedings., 2000
In this paper, we present the idea of a programmable structured P2P architecture. Our proposed sy... more In this paper, we present the idea of a programmable structured P2P architecture. Our proposed system allows the key-based routing infrastructure, which is common to all structured P2P overlays, to be shared by multiple applications. Furthermore, our architecture allows the dynamic and on-demand deployment of new applications and services on top of the shared routing layer.
2007 Ieee International Conference on Communications, 2007
Pervasive communications are increasingly sent over mobile devices and personal digital assistant... more Pervasive communications are increasingly sent over mobile devices and personal digital assistants. This trend has been observed during the last football world cup where cellular phones service providers have measured a significant increase in multimedia traffic. To better carry multimedia traffic, the IETF standardized a new TCP Friendly Rate Control (TFRC) protocol. However, the current receiver-based TFRC design is not well suited to resource limited end systems. We propose a scheme to shift resource allocation and computation to the sender. This sender based approach led us to develop a new algorithm for loss notification and loss rate computation. We demonstrate the gain obtained in terms of memory requirements and CPU processing compared to the current design. Moreover this shifting solves security issues raised by classical TFRC implementations. We have implemented this new sender-based TFRC, named TFRC light , and conducted measurements under real world conditions.
This paper introduces time stream Pdtri nets (TS treamPN), a model for the formal specification o... more This paper introduces time stream Pdtri nets (TS treamPN), a model for the formal specification of multimedia synchronization scenarios. This new model extends time Pdtri nets to formally describe the timed behaviour of multimedia objects and streams in asynchronous distributed systems. The proposed approach uses time intervals to label the arcs exiting from the places of the net, and typed transitions to define different firing rules. This model allows a complete and accurate specification of synchronization constraints between multimedia streams and can be used at different levels of granularity.
2009 Ieee International Symposium on a World of Wireless Mobile and Multimedia Networks Workshops, Jun 15, 2009
WIMAX (Worldwide Interoperability for Microwave Access) is a promising new networking technology ... more WIMAX (Worldwide Interoperability for Microwave Access) is a promising new networking technology that potentially offers high speed and wide area wireless access services that complement consistently the 3G and WiFi access networks capabilities. The standard proposes an adaptive modulation scheme which allows WiMax nodes to communicate from various modulation coding schemes according to the link quality. However, the standard does not define a detailed link adaptation algorithm and currently, the most largely used modulation adaptation technique is based on a channel quality lookup table. We argue that this method is not able to make the best adaptation decisions and delivers a sub-optimal goodput in numerous communication contexts. In this paper, we propose a novel cross layer based modulation adaptation mechanism which incorporates the use of adaptive erasure code with the physical layer information to significantly improve the goodput and transmission efficiency. Simulation results show that our proposal adapts more efficiently to real environments and achieves a significant gain on the goodput delivered to mobile nodes.
Computer Networks the International Journal of Computer and Telecommunications Networking, Oct 1, 2007
In the next generation Internet, the network will evolve from a plain communication medium into o... more In the next generation Internet, the network will evolve from a plain communication medium into one that provides endless services to the users. These services will be composed of multiple cooperative distributed application elements. We name these services overlay applications. The cooperative application elements within an overlay application will build a dynamic communication mesh, namely an overlay association. The Quality of Service (QoS) perceived by the users of an overlay application greatly depends on the QoS experienced on the communication paths of the corresponding overlay association. In this paper, we present super-peer alternate path discovery (SPAD), a distributed middleware architecture that aims at providing enhanced QoS between end-points within an overlay association. To achieve this goal, SPAD provides a complete scheme to discover and utilize composite alternate end-to-end paths with better QoS than the path given by the default IP routing mechanisms.
Ž. A Partial Order and partial reliable Connection POC is an end-to-end transport connection auth... more Ž. A Partial Order and partial reliable Connection POC is an end-to-end transport connection authorized to deliver objects in an order that can differ from the transmitted one. Such a connection is also authorized to lose some objects. The POC concept is motivated by the fact that heterogeneous best-effort networks such as Internet are plagued by unordered delivery of packets and losses, which tax the performances of current applications and protocols. It has been shown, in several Ž. research works, that out of order delivery is able to alleviate with respect to CO service the use of end systems' communication resources. In this paper, the efficiency of out-of-sequence delivery on MPEG video streams processing is Ž. studied. Firstly, the transport constraints in terms of order and reliability that can be relaxed by MPEG video decoders, for improving video transport, are detailed. Then, we analyze the performance gain induced by this approach in terms of blocking times and recovered errors. We demonstrate that POC connections fill not only the conceptual gap between TCP and UDP but also provide real performance improvements for the transport of multimedia streams such MPEG video.
Proceedings of the 5th International Icst Conference, Jul 28, 2008
Congestion control is a fundamental mechanism for the stability of the Internet and is a central ... more Congestion control is a fundamental mechanism for the stability of the Internet and is a central mechanism for TCP. However, this congestion control mechanism focuses mainly on the core network state and is blind to the characteristics of wireless and mobile access networks. Moreover, TCP window based congestion control ignores totally application layer QoS needs and entails throughput variations which are not compliant with application layer QoS constraints such as bandwidth, delay and jitter. The TCP-Friendly Rate Control protocol (TFRC) was originally designed in the context of wired networks. This protocol is one of the most convincing attempt to provide a congestion control mechanism adapted to multimedia flows, although limited in its capacity to fully address these issues. After an identification and evaluation of the subtle counterproductive interactions between the WLANs MAC layer and the transport layer, this paper shows a new approach towards congestion control for WLANs. This paper also introduces a specialization of TFRC (MTFRC: Mobile TFRC), which is adapted to wireless access networks. This TFRC specialization requires only slight changes to the standard TFRC protocol. Simulation results show substantial improvements for applications over TFRC in scenarios where the bottleneck situates on the MAC layer of the mobile nodes.
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.
This paper introduces a STIgmergy based Routing protocol (STIR) for Content Centric Delay Toleran... more This paper introduces a STIgmergy based Routing protocol (STIR) for Content Centric Delay Tolerant Networks. STIR makes the most of spatio-temporal interactions between nodes to set up bio-inspired gradient fields between content producers and content users. STIR routing follows this gradient field to efficiently route information in Delay Tolerant Networks. The validation of this protocol has been coupled with the definition of a new mobility parametric model that makes possible to easily express the preferential locations and movements commonly observed in real human mobility traces. Performance evaluations by simulations demonstrate that STIR delivers better performances than traditional protocols even in case of highly dynamic networks.
Proceedings. Fourth International Conference on Peer-to-Peer Computing, 2004. Proceedings., 2000
In this paper, we present the idea of a programmable structured P2P architecture. Our proposed sy... more In this paper, we present the idea of a programmable structured P2P architecture. Our proposed system allows the key-based routing infrastructure, which is common to all structured P2P overlays, to be shared by multiple applications. Furthermore, our architecture allows the dynamic and on-demand deployment of new applications and services on top of the shared routing layer.
2007 Ieee International Conference on Communications, 2007
Pervasive communications are increasingly sent over mobile devices and personal digital assistant... more Pervasive communications are increasingly sent over mobile devices and personal digital assistants. This trend has been observed during the last football world cup where cellular phones service providers have measured a significant increase in multimedia traffic. To better carry multimedia traffic, the IETF standardized a new TCP Friendly Rate Control (TFRC) protocol. However, the current receiver-based TFRC design is not well suited to resource limited end systems. We propose a scheme to shift resource allocation and computation to the sender. This sender based approach led us to develop a new algorithm for loss notification and loss rate computation. We demonstrate the gain obtained in terms of memory requirements and CPU processing compared to the current design. Moreover this shifting solves security issues raised by classical TFRC implementations. We have implemented this new sender-based TFRC, named TFRC light , and conducted measurements under real world conditions.
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Papers by Patrick Senac