Hicham Lakhlef

Distributed and efficient algorithm for self-reconfiguration of MEMS microrobots

Self-reconfiguration for moving MEMS microrobots currently needs a positioning system and a map of the target shape. Traditional positioning solutions like GPS or multilateration are not applicable in the micro-world and maps sharing does not scale. In this paper we present self-reconfiguration method where nodes are unaware of their positions, and where they do not have the final coordinates of each microrobots. In other words, nodes do not store the correct positions that build the target shape. Consequently memory usage for each node is reduced to O(1). This algorithm does not need message exchange to achieve the self-reconfiguration from a chain to square configuration (microrobots are organized in square shape) that represents the optimal logical topology for messages sending and it ensures a Snap-connectivity. Obtained results show a rapid convergence of the algorithm. The worst-case time complexity is of n movement rounds, where n represents the number of microrobots. Our algorithm is implemented in the declarative language MELD and executed in the simulator DPRSim.

Parallel self-reconfiguration for MEMS microrobots

MEMS microrobots are low-power and low-memory capacity devices that can sense and act. One of the most difficult challenges in MEMS microrobot applications is the self-reconfiguration, especially when the efficiency, parallelism and the scalability of the algorithm are required. Self-reconfiguration with shared map does not scale. Because the map (predefined position of the target shape) consists of P positions, and each node must have a memory capacity, at least, of P positions. Therefore, if P is very high, the self-reconfiguration will be not feasible. In this paper, we present an efficient reconfiguration algorithm, without predefined positions of the target shape, which reduces memory usage to O(1). This algorithm ensures the networks connectivity throughout all its execution time. This solution improves the execution time and the number of movements by using movement of different microrobots at the same time that we call parallelism of movement. Our algorithm is implemented in Meld, a declarative language, and executed in a real environment simulator called DPRSim.

Distributed and Dynamic Map-less Self-reconfiguration for Microrobot Networks

MEMS micro robots are low-power and low memory capacity devices that can sense and act. One of the most challenges in MEMS micro robot applications is the self-reconfiguration, especially when the efficiency and the scalability of the algorithm are required. In the literature, if we want a self-reconfiguration of micro robots to a target shape consisting of P positions, each micro robot should have a memory capacity of P positions. Therefore, if P equals to millions, each node should have a memory capacity of millions of positions. Therefore, this is not scalable. In this paper, nodes do not record any position, we present a self-reconfiguration method where a set of micro robots are unaware of their current position and do not have the map of the target shape. In other words, nodes do not store the positions that build the target shape. Consequently, memory usage for each node is reduced to O(1). An algorithm of self-reconfiguration to optimize the communication is deeply studied showing how to manage the dynamicity (wake up and sleep of micro robots) of the network to save energy. Our algorithm is implemented in Meld, a declarative language, and executed in a real environment simulator called DPRSim.

Dynamicity to Save Energy in Microrobots Reconfiguration

In this paper we present a dynamic self reconfiguration protocol for MEMS micro robots. The protocol presented in this paper is without map of the target shape which makes it efficient and scalable. In other words, nodes do not store the positions that build the target shape. Consequently, memory usage for each node is reduced to a constant complexity. An algorithm of self-reconfiguration is deeply studied showing how to manage the dynamicity (wake up and sleep of micro robots)of the network to save energy. Our algorithm is implemented in Meld, a declarative language, and executed in a real environment simulator called DPRSim.

Robust Parallel Redeployment Algorithm for MEMS Microrobots

In this paper we propose a distributed and robust parallel redeployment algorithm for MEMS micro robots. MEMS micro robots are low-power and low-memory capacity devices that can sense and act. To deal with the MEMS micro robots characteristics, in this paper, we present an efficient redeployment algorithm without predefined positions of the target shape, which reduces the memory usage to a constant complexity. This algorithm optimizes the energy consumption by minimizing the amount of displacement and the number of messages. This solution improves the memory usage (number of states), the execution time and the number of movements by using movement of different micro robots at the same time. In addition, we show how to predict the number of movement for each node to make the algorithm robust.

Agent-based broadcast protocols for wireless heterogeneous node networks

Abstract Internet of Things (IoT) is a wireless network composed of a variety of heterogeneous objects such as Connected Wearable Devices (sensors, smartwatches, smartphones, PDAs ...), Connected Cars, Connected Homes,...etc. These things use generally wireless communication to interact and cooperate with each other to reach common goals. IoT(T, n) is a network of things composed of T things with n items (packets) distributed randomly on it. The aim of the permutation routing is to route to each thing, its items, so it can accomplish its task. In this paper, we propose two agent-based broadcast protocols for mobile IoT, using a limited number of communication channels. The main idea is to partition the things into groups where an agent in each group manages a group of things. This partitioning is based on the memory capacities for these heterogeneous nodes. The first protocol uses a few communication channels to perform a parallel broadcasting and requires O ( n k ) memory space, where k is the number of communication channels. The second protocol uses an optimal complexity of memory space for each thing to achieve the permutation routing with a parallel broadcasting using less number of channels. We give an estimation of the upper and lower bounds of the number of broadcast rounds in the worst case and we discuss experimental results.

Optimal Collision/Conflict-Free Distance-2 Coloring in Wireless Synchronous Broadcast/Receive Tree Networks

This article is on message-passing systems where communication is (a) synchronous and (b) based on the “broadcast/receive” pair of communication operations. “Synchronous” means that time is discrete and appears as a sequence of time slots (or rounds) such that each message is received in the very same round in which it is sent. “Broadcast/receive” means that during a round a process can either broadcast a message to its neighbors or receive a message from one of them. In such a communication model, no two neighbors of the same process, nor a process and any of its neighbors, must be allowed to broadcast during the same time slot (thereby preventing message collisions in the first case, and message conflicts in the second case). From a graph theory point of view, the allocation of slots to processes is known as the distance-2 coloring problem: a color must be associated with each process (defining the time slots in which it will be allowed to broadcast) in such a way that any two processes at distance at most 2 obtain different colors, while the total number of colors is “as small as possible”. The paper presents a parallel message-passing distance-2 coloring algorithm suited to trees, whose roots are dynamically defined. This algorithm, which is itself collision-free and conflictfree, uses Δ + 1 colors where Δ is the maximal degree of the graph (hence the algorithm is color-optimal). It does not require all processes to have different initial identities, and its time complexity is O(dΔ), where d is the depth of the tree. As far as we know, this is the first distributed distance-2 coloring algorithm designed for the broadcast/receive round-based communication model, which owns all the previous properties. Index Terms-Broadcast/receive communication, Collision, Conflict, Distance-2 graph coloring, Message-passing, Network traversal, Synchronous system, Time slot assignment, Tree network, Wireless network.

Efficient Parallel Self-Reconfiguration Algorithm for MEMS Microrobots

In this paper we propose a distributed and efficient parallel self-reconfiguration algorithm for MEMS microrobots. MEMS microrobots perform various missions and tasks in a wide range of applications including odor localization, firefighting, medical service, surveillance and security, and search and rescue. To achieve these tasks the self-reconfiguration for MEMS microrobots is required. The self-reconfiguration with shared map does not scale. Because with the map (predefined positions of the target shape) each node should store all predefined positions of the target shape, therefore this is not always possible as MEMS nodes have a low-memory capacity. In this paper, we present an efficient self-reconfiguration algorithm without predefined positions of the target shape, which reduces the memory usage to a constant complexity. This algorithm improves the energy consumption by minimizing the amount of displacement and the number of messages.

Cliques and clusters based hierarchical scheme for sensor networks partitioning

The hierarchical clustering for wireless sensors networks is treated to solve the scalability problem in routing protocols for multi-hop wireless networks. Also a clustering-based technique is proposed to provide location management of devices for QoS support. To the best of our knowledge there is no protocol that combines the hierarchical partitioning into clusters and cliques taking into account the size of cliques and clusters (a clique is a network where every node can communicate directly with every other node in the same clique). In this paper, we propose a new partitioning scheme motivated by the need to have minimum and maximum size for cliques and clusters. In fact, this size has a direct effect on energy consumption. Indeed, for a large size of clique or cluster the cluster head should register the identities of its cluster members and manage them. That is not always feasible because sensor networks have a very limited memory capacity and energy. In addition, limiting the number of sensors in each clique or cluster avoids a significant number of cluster head re-election where the energy will be the parameter of election. So the characteristics of WSN are not satisfied, the aim of our work is to deal with these cases.

Providing Collision-Free and Conflict-Free Communication in General Synchronous Broadcast/Receive Networks

This work considers the problem of communication in dense and large scale wireless networks composed of resource-limited nodes. In this kind of networks, a massive amount of data is becoming increasinglyavailable, and consequently implementing protocols achievingerror-free communication channels constitutes an importantchallenge. Indeed, in this kind of networks, the prevention of messageconflicts and message collisions is a crucial issue. In terms ofgraph theory, solving this issue amounts to solve the distance-2coloring problem in an arbitrary graph. The paper presents adistributed algorithm providing the processes with such acoloring. This algorithm is itself collision-free and conflict-free. It is particularly suited to wireless networks composed of nodes with communication or local memory constraints.