Within Reddit, Change My View is a specific debate forum where anyone can expose her or his view on a given topic and ask the crowd to provide counter-arguments with the aim of potentially changing this view. CMV uses a dual reward system according to which a) anyone, often the person who had asked the initial question, can highlight and acknowledge an argument (a post) by giving it a "delta" (Δ) and b) anyone can up- or down-vote one or several posts in a discussion. We take advantage of this dual reward system to investigate a phenomenon we call the Consent of the Crowd. Our results provide evidence on the use of the up-vote reward system by the crowd in order to express a dissent against the Δ reward. This phenomenon may be observed when not enough contributors got a chance to join the discussion before the Δ is granted. Our result highlights the necessity for forum moderators to foster discussion between as many participants as possible before closing discussions.

We address online scheduling for servers of Cloud service providers. Each server is composed of several variable-speed processors whose power function is convex. The servers may be busy, idle or switched off. The objective of our scheduling is to minimize the energy consumed by a Cloud computing platform. To achieve this goal, we try to anticipate computing demands by predicting a workload, then we modify the set of available servers to fit this prediction and finally we schedule our jobs on the available servers. To schedule jobs we have developed the POD (Predict Optimize Dispatch) algorithm. We evaluate its performance for real-life traces in the presence of different types of prediction. The analysis shows that our scheduling reduces energy consumption considerably.

Among other modalities, online coordination can notably rely on discussions and forums. However, and notwithstanding increasing research efforts, direct approaches that would help communities and moderators distinguish between gossip and serious debates are still largely missing. We present an innovative methodology to detect the different structures of online discussions in the sub-Reddit Change My View. Applying a clustering algorithm to the author networks, we highlight three distinct classes characterized by alternative behaviors. To better understand the underlying social dynamics, we implement a relational event model that provides evidence for three effects whose influence can affect the structure of online discussions.

We are interested in Quantum Annealing (QA), an algorithm inspired by quantum theory and Simulated Annealing (SA). It is based on quantum replicas, which explore an energy surface, and are less prone to be trapped in local minima. Moreover, kinetic energy helps replicas to find a global minimum. This method has proved its efficiency for several optimization problems. We start this study by presenting the application of QA to a new problem: the Multidimensional Knapsack Problem (MKP). We then present a new idea to speed up the quantum annealing process by detecting the resemblance between replicas. If many of the replicas exhibit the same properties, our assumption is that these properties will also be present with a high probability in a global solution. Consequently, the QA may restrict certain mutations in order to preserve those similarities. We call this algorithm Restrictive Quantum Annealing (RQA). We establish that RQA has better performances than QA and SA by carrying out an adequate analysis of the RQA performance, taking the Traveling Salesman Problem (TSP) and the above-mentioned MKP as references. We also advance guidelines indicating types of NP-hard problems for which our algorithm is particularly well adapted.

Due to wireless propagation condition, users in a cell experience different channel condition. Thus cell-center users have optimal condition whereas cell-edge users suffer from a severe path-loss and a low bit-rate. In this paper, a fair scheme to allocate Resource Blocks (RB) on the downlink in LTE networks is proposed. The problem addresses maximising the overall system throughput while ensuring the fair resource allocation among UEs (User Equipment). We use a new fairness criterion which is based upon the concept of the Nash Bargaining Solution (NBS) model. Our idea is to bring in a compensating factor to overcome the path-loss influence. The performance evaluation confirms that our method is able to spread resources fairly over the entire cell.

We present our work on the dimensioning of a packet-switching wavelength division multiplexing ring in order to reduce its infrastructure (capital expenditure) cost. We study a new all-optical architecture: the packed optical add-drop multiplexer (POADM). We aim to minimize the overall cost of the network by reducing the number of indispensable devices in the nodes and the number of required wavelengths. We formalize the packing problems underlying the ring dimensioning. The elements to be packed are made up of transmissions that share the same destination. We assume that elements can be cut before being packed into boxes. We furnish a complete theoretical analysis of the complexity and approximability of these problems. We define also several measures of quality for a cut and provide an optimal cutting strategy, according to these measures. Our subsequent contribution is a heuristic solution that solves the bi-criteria packing problem (the number of boxes and the number of cuts are minimized simultaneously). The exhaustive numerical results of this heuristic algorithm come next. We rely on our optimal cutting strategy to appraise the efficiency of other strategies. We also adapt the only existing POADM dimensioning algorithm, more restrictive than ours, and we confront it with our solution. The analysis of results allows us to provide network design guidelines to perform the dimensioning in the most efficient way.

Private Mobile Radio (PMR) networks are cellular infrastructures dedicated to be used by professionals, such as public safety, military, industry and transportation organizations. In those networks, resources are scarce, and there are strong Quality of Service (QoS) requirements. The emergence of new services which need more bandwidth has made the world PMR leader focus on the LTE-Advanced protocol. In order to ensure the QoS despite resource shortage, we propose an algorithm of Resource Blocks (RBs) allocation with spatial frequency reuse whose scheme takes into account users' (UEs') interference possibility and probability. We start by defining the underlying problem, which we call Weighted Fractional Coloring Problem (WFCP), in terms of graph theory. Next, we prove its NP-hardness. As obtaining an exact solution of such a problem in reasonable time is unrealistic, we propose a heuristic algorithm. In order to evaluate the performance of our algorithm we use a rigorous validation procedure. We compare its performance with that of a random one which we propose as a reference and the exact one which can be run on very small networks. Thanks to the results obtained we believe that the proposed algorithm can establish a solid starting point to conceive its distributed versions for novel PMR protocols.

Independent operator networks are called either Autonomous Systems (AS) or domains. Numerous studies based on complex measurement platforms have been carried out for over ten years now in order to discover the Internet topology on domain level. The routing realized by Border Gateway Protocol (BGP) is strongly influenced by commercial relationships which exist between domains, because domain operators do not want to make public the routes they know, as announcing certain routes would deprive them of a possible financial benefit. Consequently, routes available in BGP tables are valley-free and they are “spanned” on the inter-domain hierarchy. This property of BGP routes has an impact on the performance of protocols which are proposed to assure the QoS. We examined the existing Internet topologies gathered on the domain level over the six year period in the context of their hierarchy. We used aSHIIP, our random hierarchical topology generator, to induct the hierarchy into the collected topologies. We proposed new methods for detecting the core of a network. Thanks to this analysis we have been able to put forward solid inter-domain hierarchy induction methods which are implemented in our publicly available tool.

The multi-user medium access mechanism OFDMA has to provide each node with a given amount of radio resources. In this paper we present a new distributed algorithm for the allocation of resource blocks in an OFDMA ad hoc network. We are principally interested in allocating resources fairly because the ad hoc networks which we work on are dedicated to be deployed in the areas of natural or man-made disasters and where the guarantee of connectivity is an important issue. Contrary to the commonly applied approach, we consider a resource allocation on the links under a two hop interference distance. The proposed allocation procedure is coupled with our other algorithm which detects and corrects two hop interferences and which has been revised and improved. The performance of our algorithm is evaluated by simulation for different topologies. We observed that simultaneous allocations in large networks allow a constant convergence time to be kept despite the networks size.

Numerous studies based on complex measurement platforms have been carried out for over ten years now in order to discover the Internet topology on domain level. It turns out that this topology exhibits certain invariant properties such as a distribution of node degree. This distribution follows a power law. Moreover, the revealed topology is hierarchical. The hierarchy is caused by commercial contracts signed between domain operators. The routing realized by Border Gateway Protocol (BGP) is strongly influenced by these commercial relationships because operators do not want to make public the routes they know, as announcing certain routes would deprive them of a possible financial benefit. Consequently, routes available in BGP tables are of particular shape (valley-free). This fact has an impact on the performance of protocols which are proposed notably to assure the Quality of Service (QoS). In order to evaluate the performance of new protocols in the inter-domain context their designers have to have at their disposal a random topology generator which is able to furnish a random graph whose nodes' degree follows a power law typical for the Internet, and to impose the commercial hierarchy on it. Our aSHIIP (autonomous Supélec Hierarchy Inter-domain Program) does both: its synthetic topologies are realistic and the hierarchy, which it introduces, corresponds to the one of the Internet. After explaining the reasons for our study, we present the methods which we propose to use for the flat Internet topology generation which satisfies the realism of the Internet. Next, we explain our algorithm used to induct the commercial hierarchy. The algorithm is heuristic because, as we prove in this paper, the underlying problem is NP-complete. We then evaluate the topologies generated with aSHIIP. The result is a reliable flat Internet-like topology generator which also allows the modeler to introduce the realistic hierarchy. We are convinced we can recommend it to modelers dealing with performance evaluation of protocols for the Internet on domain level.

Numerous studies based on complex measurement platforms have been carried out for over ten years now in order to discover the Internet topology on domain level. It turns out that this topology exhibits certain invariant properties such as a distribution of node degree. This distribution follows a power law. Moreover, the revealed topology is hierarchical. The hierarchy is caused by commercial contracts signed between domain operators. The routing realized by BGP is influenced by these relationships because operators do not want to make public the routes they know, as announcing certain routes would deprive them of a possible financial benefit. Consequently, routes available in BGP tables are valley-free. This fact has an impact on the performance of protocols which are proposed notably to assure the QoS. In order to evaluate the performance of new protocols in the inter-domain context their designers have to have at their disposal a random topology generator which is able to furnish a random graph whose nodes' degree follows a power law typical for the Internet, and to impose the commercial hierarchy on it. Our a SHIIP (autonomous Supelec Hierarchy Inter-domain Program) does both. It is a reliable flat Internet-like topology generator which also allows the modeler to introduce the realistic hierarchy.

This paper presents a novel model to analyze the performance of the asynchronous optical CSMA/CA protocol with variable packet sizes. The model combines Continuous Time Markov Chain (CTMC) approach and probabilistic approximation for FIFO scheduling. Realistic simulation models were developed in order to identify the difficulties in modelling CSMA/CA scheme and to show the errors introduced by the probabilistic service discipline. Although the service discipline is approximate, the proposed model includes all factors felt to be important in dimensioning the memory size at access points so as to meet access delay and throughput criteria.