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A multichannel MAC improves throughput in wireless mesh networks by multiplexing transmissions across orthogonal channels. In this paper, we propose an efficient way for constructing the wireless mesh structure associated with Molecular MAC, a multichannel MAC layer for efficient packet forwarding. Molecular MAC outperforms other classical approaches, but requires a specific structure for efficient operation. First, we propose a centralized protocol that provides an upper bound for constructing such a molecular structure through a MILP (Mixed Integer Linear Programming) formulation that maximizes network capacity. Then, we present two distributed self-stabilizing heuristic protocols derived from the protocols for constructing respectively a Maximum Independent Set and a Spanning Tree. We compare the performance of the proposed protocols in terms of network capacity and route length.

International audienceThe problem presented in this paper is a generalization of the usual coupled-tasks scheduling problem in presence of compatibility constraints. The reason behind this study is the data acquisition problem for a submarine torpedo. We investigate a particular configuration for coupled tasks (any task is divided into two sub-tasks separated by an idle time), in which the idle time of a coupled task is equal to the sum of durations of its two sub-tasks. We prove -completeness of the minimization of the schedule length, we show that finding a solution to our problem amounts to solving a graph problem, which in itself is close to the minimum-disjoint-path cover (min-DCP) problem. We design a (3a+2b)/(2a+2b)-approximation, where a and b (the processing time of the two sub-tasks) are two input data such as a>b>0, and that leads to a ratio between 3/2 and 5/4. Using a polynomial-time algorithm developed for some class of graph of min-DCP, we show that the ratio decreases to 1.37

A multi-channel MAC seems to be an interesting approach for improving network throughput by multiplexing transmissions over orthogonal channels. In particular, Molecular MAC has recently proposed to modify the standard IEEE 802.11 DCF access method to use dynamic channel switching for efficient packet forwarding over multiple hops. However, this MAC layer requires role and channel assignment to nodes: some of them use a static channel, while others dynamically switch to neighbor channels on-demand. To assign roles and channels, we extend the notion of the Weakly Connected Dominating Set, the structure already used in clustering. More precisely, we adapt the WCDS structure and introduce new constraints to define what we call a reversible WCDS (r-WCDS), which is particularly suitable for wireless mesh networks operating under Molecular MAC. We propose a divide-and-conquer scheme that partitions the network into clusters with one leader per cluster solving a MILP formulation to assign roles in its cluster. By appropriately defining the roles at the border of clusters, we maintain global connectivity in the r-WCDS. Finally, our simulations show that the performance of the propose scheme is close to a centralized algorithm.

Abstract. We consider the makespan minimization coupled-tasks problem in presence of compatibility constraints with a specified topology. In particular, we focus on stretched coupled-tasks, i.e. coupled-tasks having the same sub-tasks execution time and idle time duration. We study several problems in framework of classic complexity and approximation for which the compatibility graph is bipartite (star, chain, . . .).In such a context, we design some efficient polynomial-time approximation algorithms for an intractable scheduling problem according to some parameters.

This paper deals with broadcasting problem in Vehicular Ad hoc Networks (VANETs). This communication mode is commonly used for sending safety messages and traffic information. However designing an efficient broadcasting protocol is hard to achieve since it has to take into account some parameters related to the network environment, for example the network density, in order to avoid causing radio interferences. In this paper, we propose a novel Autonomic Dissemination Method (ADM) which delivers messages in accordance with given priority and density levels. The proposed approach is based on two steps: an offline optimization process and an adaptation to the network characteristics. The first step uses a genetic algorithm to find solutions that fit the network context. The second one relies on the Autonomic Computing paradigm. ADM allows each vehicle to dynamically adapt its broadcasting strategy not only with respect to the network density, but also in accordance to the priority level of the message to send. The experimental results show that ADM effectively uses the radio resources even when there are globally many messages to send simultaneously. Moreover, ADM allows to increase the message delivery ratio and to reduce the latency and radio interferences.

International audienceLet k >= 2 be an integer and T-1,..., T-k be spanning trees of a graph G. If for any pair of vertices {u, v} of V(G), the paths between u and v in every T-i, 1 <= i <= k, do not contain common edges and common vertices, except the vertices u and v, then T1,... Tk are completely independent spanning trees in G. For 2k-regular graphs which are 2k-connected, such as the Cartesian product of a complete graph of order 2k-1 and a cycle, and some Cartesian products of three cycles (for k = 3), the maximum number of completely independent spanning trees contained in these graphs is determined and it turns out that this maximum is not always k. (C) 2016 Elsevier B.V. All rights reserved

This paper presents a new consensus algorithm, Proof of Usage (PoU), for the blockchain technology. This consensus is introduced for permissioned (or private) blockchains and is designed for a user-centric personal data market. This market is subject to specific regulations with which conventional blockchains fail to comply. Proof of Usage aims to promote a new paradigm dedicated to usage incentivization, valuation, and control of user data in various sectors, such as banking and insurance. Other consensuses such as Proof of Stake or historical Proof of Work do not encourage coin spending and usage (in fact, Proof of Stake promotes the opposite). However, the value of the currency mainly depends on its use. This paper first introduces a contextualization of blockchain technology and decentralized consensus models. The motivation is then discussed for a new model of personal data exchange in a decentralized but supervised environment. The PoU protocol and its process flow are defined in detail. Furthermore, the paper explores two different approaches regarding the reward mechanism and the incentive model. Finally, the paper focuses on security requirements and how PoU meets such requirements in a permissioned-based blockchain system. 1 An asymmetric mathematical problem is a mathematical problem that is hard to solve but the solution of which is easy to verify.