Publications de Patrick Thiran

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We consider the problem of jointly allocating channel center-frequencies and bandwidths for IEEE 802.11 wireless LANs (WLANs). The bandwidth used on a link significantly affects both the capacity experienced on this link and the interference produced on neighboring links. Therefore, when jointly assigning both center frequencies and channel widths, a trade-off must be found between interference mitigation and the potential capacity offered on each link. We study this trade-off and present SAW (spectrum assi

Power-line communications are becoming a key component in home networking. The dominant MAC protocol for high data-rate power-line communications, IEEE 1901, employs a CSMA/CA mechanism similar to the backoff process of 802.11. Existing performance evaluat ...

Failure restoration at the IP layer in IP-over-WDM networks requires to map the IP topology on the WDM topology in such a way that a failure at the WDM layer leaves the IP topology connected. Such a mapping is called survivable. Finding a survivable mappin ...

Hierarchical community detection consists in finding a tree of communities where deeper levels of the hierarchy reveal finer-grained structures. There are two main classes of algorithms for this task. Divisive (topdown) algorithms recursively partition nodes into smaller communities until a stopping criterion indicates that no further splits are necessary. In contrast, agglomerative (bottom-up) algorithms first identify the smallest community structures and then repeatedly merge the communities by using a l

We model some lossless queuing systems arising in guaranteed service networks as non-linear min-plus systems that can be bounded by linear systems. We introduce the distinction between space and time methods for such systems. Space methods are related to min-plus system theory, while time methods borrow from dynamic programming and exploit the causality of the operators. We apply this to the window flow control problem previously studied by Cruz and Okino

Connection Admission Control (CAC) algorithms are used to decide whether an incoming connection should be accepted or rejected in a node of a network offering reservation based services in order to maintain the guaranteed Quality of Service (QoS) in the network. In this paper, we consider the statistical CAC algorithm proposed by Elwalid et al. [ 2 ]. The traffic model is made of ON-OFF sources and the QoS parameter is the loss probability. Based on the traffic descriptors of existing and incoming connectio

We address the problem of calculating link loss rates from end-to-end measurements. Contrary to existing works that use only the average end-to-end loss rates or strict temporal correlations between probes, we exploit second-order moments of end-to-end flo ...

We consider a wireless sensor network, where nodes switch between an active (on) and a sleeping (off) mode, to save energy. Their switching on/off schedules are completely non-coordinated. Their positions are distributed according to a Poisson process, and their connectivity range is larger or equal to their sensing range. The durations of active and sleeping periods are such that the number of active nodes at any particular time is so low that the network is always disconnected. Is it possible to use such

Wireless Mesh Networks (WMNs) are based on packet forwarding and therefore require efficient multi-hop protocols for their deployment. Toward this objective, we study the flow of packets through the network and using an analogy with fluid physics we classify them as being either laminar in the case of a smooth propagation or turbulent otherwise. Following this terminology, we present the tendency of current 802.11 to generate turbulent flows, i.e. to queue packets at the intermediate nodes for a non-determi

Numerous approaches have been proposed to manage Quality of Service in the Internet. However, none of them was successfully deployed in a commercial IP backbone, mostly because of their complexity. In this paper, we take advantage of the excess network bandwidth to offer a degraded class of traffic. We identify and analyze the impact of link failures on such a service and show that under a variety of circumstances failures provide a natural mechanism for service differentiation. We simulate our QoS scheme o

Continuum percolation models in which pairs of points of a two-dimensional Poisson point process are connected if they are within some range to each other have been extensively studied. This paper considers a variation in which a connection between two poi ...

We model traffic on an uncongested backbone link of an IP network using Poisson Shot-noise process and M/G/

\infty

queue. We validate the model by simulation. We analyze the model accuracy with real traffic traces collected on the Sprint IP backbone network. We show that despite its simplicity, our model provides a good approximation of the real traffic observed on OC-3 links. This model is also very easy to use and requires few simple parameters to be input.

In wireless sensor networks (WSNs), the base station (BS) is a critical sensor node whose failure causes severe data losses. Deploying multiple fixed BSs improves the robustness, yet requires all BSs to be installed with large batteries and large energy-ha ...

In recent years, multipath routing, i.e., employing several paths simultaneously, has emerged as an efficient way to provide significant throughput gains in local networks. This has been observed both with technologies that are not subject to interference, ...

We consider online predictions of vote results, where regions across a country vote on an issue under discussion. Such online predictions before and during the day of the vote are useful to media agencies, polling institutes, and political parties, e.g., t ...

Consider a set of probes, called “agents”, who sample, based on opportunistic contacts, a population moving between a set of discrete locations. An example of such agents are Bluetooth probes that sample the visible Bluetooth devices in a population. Based on the obtained measurements, we construct a parametric statistical model to jointly estimate the total population size (e.g., the number of visible Bluetooth devices) and their spatial density. We evaluate the performance of our estimators by using Bluet

In multi-hop ad hoc networks, the efficiency of a medium access control protocol under heavy traffic load depends mainly on its ability to schedule a large number of simultaneous non-interfering transmissions. However, as each node has only a local view of ...

We study analytically and experimentally the throughput of the packetized time-varying discrete erasure channel with feedback, which closely captures the behavior of many practical physical layers. We observe that the channel variability at different time ...

Energy efficiency of wireless sensor networks (WSNs) can be improved by moving base stations (BSs), as this scheme evenly distributes the communication load in the network. However, physically moving BSs is complicated and costly. In this paper, we propose a new scheme: virtually moving the BSs. We deploy an excessive number of BSs and adaptively re-select a subset of active BSs so as to emulate the physical movement. Beyond achieving high energy-efficiency, this scheme obviates the difficulties associated

Requiring all nodes of a wireless multihop network to be connected is expensive and results in a poor scalability of properties such as transport capacity. We show however that it is no longer the case if we only slightly loosen the connectivity requirement, by just imposing that most nodes be connected to each other (so that the network percolates). This feature is found in models neglecting interferences, taking interferences as noise or taking a more information theoretic approach.

Patrick Thiran

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SAW: Spectrum Assignment for WLANs

On the MAC for Power-Line Communications: Modeling Assumptions and Performance Tradeoffs

Survivable Routing of Mesh Topologies in IP-over-WDM Networks by Recursive Graph Contraction

When does bottom-up beat top-down in hierarchical community detection?

A note on Time and Space Methods in Network Calculus

Regulation of a Connection Admission Control Algorithm

Network Loss Inference with Second Order Statistics of End-to-End Flows

Latency of wireless sensor networks with uncoordinated power saving mechanisms

Promiting Fluidity in the Flow of Packets of 802.11 Wireless Mesh Networks

Network Availability Based Service Differentiation

Percolation in the signal to interference ratio graph

A flow-based model for Internet backbone traffic

The Beauty of the Commons: Optimal Load Sharing by Base Station Hopping in Wireless Sensor Networks

Optimal Number of Paths with Multipath Routing in Hybrid Networks

Online Collaborative Prediction of Regional Vote Results

Opportunistic Sampling for Joint Population Size and Density Estimation

A Packing Approach to Compare Slotted and Non-Slotted Medium Access Control

Impacts of Channel Variability on Link-Level Throughput in Wireless Networks

Virtually Moving Base Stations for Energy Efficiency in Wireless Sensor Networks

The Costly Path from Percolation to Full Connectivity