Papers by Thierry Turletti
Theory and Practice of Logic Programming, 2006
The software approach to developing Digital Signal Processing (DSP) applications brings some grea... more The software approach to developing Digital Signal Processing (DSP) applications brings some great features such as flexibility, re-usability of resources and easy upgrading of applications. However, it requires long and tedious tests and verification phases because of the increasing complexity of the software. This implies the need of a software programming environment capable of putting together DSP modules and providing facilities to debug, verify and validate the code. The objective of the work is to provide such facilities as simulation and verification for developing DSP software applications. This led us to develop an extension toolkit, EPspectra, built upon Pspectra, one of the first toolkits available to design basic software radio applications on standard PC workstations.
The emerging widespread use of real-time multimedia applications over wireless networks makes the... more The emerging widespread use of real-time multimedia applications over wireless networks makes the support of Quality of Service (QoS) a key problem. In this paper, we focus on QoS support mechanisms for IEEE 802.11 Wireless ad-hoc networks. First, we review limitations of the upcoming IEEE 802.11e Enhanced DCF (EDCF) and other enhanced MAC schemes that have been proposed to support QoS for 802.11 adhoc networks. Then, we describe a new scheme called adaptive fair EDCF that extends EDCF, by increasing the contention window during deferring periods when the channel is busy, and by using an adaptive fast backoff mechanism when the channel is idle. Our scheme computes an adaptive backoff threshold for each priority level by taking into account the channel load. The new scheme significantly improves the quality of multimedia applications. Moreover, it increases the overall throughput obtained both in medium and high load cases. Simulation results show that our new scheme outperforms EDCF and other enhanced schemes. Finally, we show that the adaptive fair EDCF scheme achieves a high degree of fairness among applications of the same priority level.
IEEE 802.16 WiMAX is a promising new wireless technology for providing broadband ubiquitous netwo... more IEEE 802.16 WiMAX is a promising new wireless technology for providing broadband ubiquitous network access. As more and more researchers and industrials are interested in simulating such networks, a number of WiMAX simulators have been emerged in the networking community. One of the most recent WiMAX simulator is the one developed for ns-3. This module provides a standard compliant and well designed implementation of the standard and benefits from the major enhancements provided by ns-3 (compared to other network simulators) which has all the capabilities of becoming the leading network simulator in near future. However, this WiMAX module still lacks some important features which motivated this work. In this paper, we first provide a snapshot of existing WiMAX simulators available in the public domain, while highlighting their limitations. Then, we describe the new features and enhancements we have integrated within the ns-3 WiMAX module, and in particular: a realistic and scalable physical model, an IP packet classifier for the convergence sub-layer, efficient uplink and downlink schedulers, support for multicast traffic and pcap packet tracing functionality. The new design of the physical layer has improved the simulation time by several magnitude orders while still providing a realistic implementation of the standard. Furthermore, the IP classifier has enabled the simulation of an unlimited number of service flows per subscriber station, while the proposed schedulers improve the management of the QoS requirements for the different service flows.
Proceedings of the 7th ACM international symposium on Modeling, analysis and simulation of wireless and mobile systems - MSWiM '04, 2004
Today, three different physical (PHY) layers for the IEEE 802.11 WLAN are available (802.11a/b/g)... more Today, three different physical (PHY) layers for the IEEE 802.11 WLAN are available (802.11a/b/g); they all provide multi-rate capabilities. To achieve a high performance under varying conditions, these devices need to adapt their transmission rate dynamically. While this rate adaptation algorithm is a critical component of their performance, only very few algorithms such as Auto Rate Fallback (ARF) or Receiver Based Auto Rate (RBAR) have been published and the implementation challenges associated with these mechanisms have never been publicly discussed. In this paper, we first present the important characteristics of the 802.11 systems that must be taken into account when such algorithms are designed. Specifically, we emphasize the contrast between low latency and high latency systems, and we give examples of actual chipsets that fall in either of the different categories. We propose an Adaptive ARF (AARF) algorithm for low latency systems that improves upon ARF to provide both short-term and long-term adaptation. The new algorithm has very low complexity while obtaining a performance similar to RBAR, which requires incompatible changes to the 802.11 MAC and PHY protocol. Finally, we present a new rate adaptation algorithm designed for high latency systems that has been implemented and evaluated on an AR5212-based device. Experimentation results show a clear performance improvement over the algorithm previously implemented in the AR5212 driver we used.
2002 IEEE International Symposium on Circuits and Systems. Proceedings (Cat. No.02CH37353), 2002
This paper addresses the problem of rate and congestion control for video transmission in large m... more This paper addresses the problem of rate and congestion control for video transmission in large multicast groups. A classification of the receivers is performed according to a predefined similarity measure (e.g. packet loss rate observed or TCP-friendly bandwidth share). The RTCP receiver reports are then filtered accordingly. The classification of receivers done by feedback aggregation agents helps in solving the feedback implosion problem in large multicast groups. The clustering and feedback aggregation mechanisms are coupled with an FGS layered video coding system in which the number of layers as well as their respective rates are adapted dynamically to aggregated feedback. The algorithm has been validated via NS 2 simulations. INRIA, 2004 route des Lucioles -BP 93,
2006 International Symposium on a World of Wireless, Mobile and Multimedia Networks(WoWMoM'06), 2006
Network coding is a new transmission paradigm that proved its strength in optimizing the usage of... more Network coding is a new transmission paradigm that proved its strength in optimizing the usage of network resources. In this paper, we evaluate the gain from using network coding for file sharing applications running on top of wireless mesh networks. With extensive simulations carried out on a simulator we developed specifically for this study, we confirm that network coding can improve the performance of the file sharing application, but not as in wired networks. The main reason is that nodes over wireless cannot listen to different neighbors simultaneously. Nevertheless, one can get more from network coding if the information transmission is made more diverse inside the network. We support this argument by varying the loss rate over wireless links and adding more sources.
14th IEEE Proceedings on Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003., 2003
~Ihsrruci-~rhe IEEE 802.1 I Medium Access Control (MAC) protucol provides a contention-based dist... more ~Ihsrruci-~rhe IEEE 802.1 I Medium Access Control (MAC) protucol provides a contention-based distributed channel access mechanism for mobile stations to share the wireless medium, which may introduce a lot of collisions in ease of overloaded active stations. Slow Contention Window (CW) decrease scheme is a simple and efficient solution for this problem. In this paper, we use an analytical model to compare the slow CW decrease scheme t u the IEEE 802.11 MAC protocol. Several parameters are invcrtigdted such as thc number of Svations, the initial CW size. the decrease factor value. the maximum bdckoff stage and the coexistence with the RequestToSend and ClearToSend (RlSICTS) mechanism. The results show that the slow CW decl-ease scheme can efficiently improve the throughput of IEEE 802.11. a n d that the throughput gain is higher when the -decrease hctor is larger. Moreover, the initial CW size and maximum backoff stage also affect tlie performance of slow CW decrease scheme. K q w i r d s -IEEE X02.11; DCF; slow CW decrease scheme; ~r s m s
Proceedings of the 2006 SIGCOMM workshop on Large-scale attack defense - LSAD '06, 2006
The recently proposed coordinates-based systems for network positioning have been shown to be acc... more The recently proposed coordinates-based systems for network positioning have been shown to be accurate, with very low distance prediction error. However, these systems often rely on nodes coordination and assume that information reported by probed nodes is correct. In this paper, we identify different attacks against coordinates embedding systems and study the impact of such attacks on the recently proposed Vivaldi decentralized positioning system. We present a simulation study of attacks carried out by malicious nodes that provide biased coordinates information and delay measurement probes. We experiment with attack strategies that aim to (i) introduce disorder in the system, (ii) fool honest nodes to move far away from their correct positions and (iii) isolate a particular node in the system through collusion. Our findings confirm the susceptibility of the Vivaldi System to such attacks.
Lecture Notes in Computer Science, 2005
Lecture Notes in Computer Science, 2005
We propose the so-called backup tree algorithm to compute a set of n-1 backup multicast delivery ... more We propose the so-called backup tree algorithm to compute a set of n-1 backup multicast delivery trees from the default multicast tree for application level multicast. For each backup multicast tree exactly one link of the default multicast tree is replaced by a backup link from the set of available links. The backup tree algorithm calculates the n-1 trees with a complexity of O (m log n).
A multi-platform event-driven controller for network experiments
Proceedings of the 2012 ACM conference on CoNEXT student workshop - CoNEXT Student '12, 2012
ABSTRACT Network researchers rely on a wide variety of experimentation platforms, ranging from si... more ABSTRACT Network researchers rely on a wide variety of experimentation platforms, ranging from simulators to emulators and live testbeds, to validate new ideas. Many experiment management frameworks have been created to ease up the complexity and time cost of deploying experiments on different platforms. However, providing flexible deployment capabilities for arbitrary platforms remains a challenging problem. In this work we propose an experiment controller architecture based on event scheduling, designed to enable flexible experiment deployment on diverse platforms. This architecture is capable of handling arbitrary deployment dependencies, both imposed by user requirements and by platform restrictions. It additionally enables flexible resource provisioning, at any point in time during experiment execution, and flexible experiment monitoring events.
Proceedings of the 3rd International ICST Conference on Simulation Tools and Techniques, 2010
IEEE 802.16 WiMAX is a promising new wireless technology for providing broadband ubiquitous netwo... more IEEE 802.16 WiMAX is a promising new wireless technology for providing broadband ubiquitous network access. As more and more researchers and industrials are interested in simulating such networks, a number of WiMAX simulators have been emerged in the networking community. One of the most recent WiMAX simulator is the one developed for ns-3. This module provides a standard compliant and well designed implementation of the standard and benefits from the major enhancements provided by ns-3 (compared to other network simulators) which has all the capabilities of becoming the leading network simulator in near future. However, this WiMAX module still lacks some important features which motivated this work. In this paper, we first provide a snapshot of existing WiMAX simulators available in the public domain, while highlighting their limitations. Then, we describe the new features and enhancements we have integrated within the ns-3 WiMAX module, and in particular: a realistic and scalable physical model, an IP packet classifier for the convergence sub-layer, efficient uplink and downlink schedulers, support for multicast traffic and pcap packet tracing functionality. The new design of the physical layer has improved the simulation time by several magnitude orders while still providing a realistic implementation of the standard. Furthermore, the IP classifier has enabled the simulation of an unlimited number of service flows per subscriber station, while the proposed schedulers improve the management of the QoS requirements for the different service flows.
2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004
The emerging widespread use of real-time multimedia applications over wireless networks makes the... more The emerging widespread use of real-time multimedia applications over wireless networks makes the support of Quality of Service (QoS) a key problem. In this paper, we focus on QoS support mechanisms for IEEE 802.11 Wireless ad-hoc networks. First, we review limitations of the upcoming IEEE 802.11e Enhanced DCF (EDCF) and other enhanced MAC schemes that have been proposed to support QoS for 802.11 adhoc networks. Then, we describe a new scheme called adaptive fair EDCF that extends EDCF, by increasing the contention window during deferring periods when the channel is busy, and by using an adaptive fast backoff mechanism when the channel is idle. Our scheme computes an adaptive backoff threshold for each priority level by taking into account the channel load. The new scheme significantly improves the quality of multimedia applications. Moreover, it increases the overall throughput obtained both in medium and high load cases. Simulation results show that our new scheme outperforms EDCF and other enhanced schemes. Finally, we show that the adaptive fair EDCF scheme achieves a high degree of fairness among applications of the same priority level.
2005 International Conference on Wireless Networks, Communications and Mobile Computing, 2005
We propose a closed-loop, dynamic rate adaptation algorithm that can be implemented in all IEEE 8... more We propose a closed-loop, dynamic rate adaptation algorithm that can be implemented in all IEEE 802.11 a/b/g compliant wireless local area networks. Our proposed algorithm is a culmination of the best attributes of the transmitter-based Auto-Rate Fall-back (ARF) and the Receiver-based Auto-Rate (RBAR) control mechanisms with additional practical features to facilitate multipath fading channel sensing and feedback control signalling. Unlike ARF, our technique supports real-time feedback information beyond frame acknowledgments through the use of reserved bits in the SERVICE field of the Physical Layer Convergence Protocol (PLCP) header. Unlike RBAR, no modification of the medium-access control (MAC) frame format is necessary for feedback control since the initial channel state information is conveyed via these same reserved bits. Our proposed scheme is transparent in the sense that devices using our technique can co-exist with other 802.11-compliant devices in the same basic service area. By combining RTS/CTS handshake with data fragmentation, we differentiate data loss (and reduction in goodput) due to MAC collision from data corruption due to bad physical channel state and poor rate selection. The goodput gains of our approach, when compared to ARF and RBAR, are measured via simulation for various traffic load conditions in stationary and non-stationary multipath fading channel models.
Accurate and explicit differentiation of wireless and congestion losses
23rd International Conference on Distributed Computing Systems Workshops, 2003. Proceedings., 2003
Abstract In recent years mobile computing has experienced an explosive growth, mainly due to the ... more Abstract In recent years mobile computing has experienced an explosive growth, mainly due to the integration of wireless networks with the wired Internet. To deploy bandwidth-greedy multimedia applications on such heterogeneous environments, efficient congestion ...
Demonstrating a unified ICN development and evaluation framework
Proceedings of the 1st international conference on Information-centric networking - INC '14, 2014
2013 Third International Conference on Communications and Information Technology (ICCIT), 2013
Content dissemination is the primary usage of the Internet today, whereas the existing Internet a... more Content dissemination is the primary usage of the Internet today, whereas the existing Internet architecture based on TCP/IP is mainly designed for point-to-point communications. Information-Centric Networking (ICN) has been proposed to conciliate Internet usage and technology. The idea behind ICN is to omit the notion of host and location and establish content as the first class citizen of the network. ICN advocates innetwork caching, i.e., to cache content on the path from content providers to requesters. This on-path caching achieves good overall performance but is not optimal as content may be replicated on routers so reducing the total volume of content that can be cached. To overcome this limitation, we introduce the notion of off-path caching where we allocate content to well defined off-path caches within the network and deflect the traffic off the optimal path toward these caches that are spread across the network. Off-path caching improves the global hit ratio by efficiently utilizing the network-wide available caching capacity and permits to reduce egress links' bandwidth usage.
Automated Deployment and Customization of Routing Overlays on Planetlab
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2012
Controllable Packet Prioritization on PlanetLab Using NEPI
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2012
Hidden nodes are a fundamental problem that can potentially affect any wireless network where nod... more Hidden nodes are a fundamental problem that can potentially affect any wireless network where nodes cannot hear each other. Although the hidden node problem is well known, so far only few papers have quantified its effects in a comprehensive manner. This paper represents a first step towards getting a quantitative insight into the impact of hidden nodes on the performance of wireless networks. We first carry out an exact queuing-theoretic analysis for a 4-node segment and derive analytical expressions for the probability of packet collision, the mean packet delay, and the maximum throughput, based on a model that closely follows the IEEE 802.11 standard. We then extend the analysis and provide an approximation for a general linear topology that is asymptotically exact at low load. Finally, we perform detailed simulations to validate our analytical results and show their applicability to predict the performance of IEEE 802.11 networks with hidden nodes. The simulation and analysis closely match. Moreover, they reveal that the impact of hidden nodes propagates through the network causing some nodes to saturate at load as low as 15% of the capacity.
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Papers by Thierry Turletti