Isabelle Augé-Blum

Implementation of Gradient Routing in Wireless Sensor Networks

IETF ROLL has recently proposed gradient routing as a fundamental building block for data collection in Wireless Sensor Networks. This paper seconds this choice by presenting an implementation of gradient routing on current hardware, and by showing experimentally that gradient routing is robust against topological changes. n nTo stress its self-healing quality, we design and implement a complete communication stack in which neighbor tables are built in a purely reactive fashion. We quantify the resulting topological changes, and show how gradient routing elegantly handles these dynamics. n nThis paper presents, to the best of our knowledge, the first experimental study on gradient routing as advocated by IETF ROLL.

Dual-mode real-time MAC protocol for wireless sensor networks: a validation/simulation approach

Several wireless sensor network applications are currently appearing in various domains. Their goal is often to monitor a geographical area. When a sensor detects a monitored event, it informs a sink node using alarm messages. The area surveillance application needs to react to such an event with a finite, bounded and known delay: these are real-time constraints. This work proposes a real-time MAC protocol with realistic assumptions for a random linear network, where sensors are deployed randomly along a line. We present a formal validation of this protocol both for initialization and run-time, and present simulation results on a realistic scenario.

Proposition of a hard real-time MAC protocol for wireless sensor networks

Many wireless sensor network applications are emerging nowadays. For critical, safety related applications, the network needs to provide bounded transmission delays. Hard real-time guarantees need therefore to be given by wireless sensor network communication protocols. In this paper, we propose a new hard real-time MAC protocol, and we give the time constraints that can be reached.

1-hopMAC: An Energy-Efficient MAC Protocol for Avoiding 1 -hop Neighborhood Knowledge

Wireless sensor networks (WSNs) have witnessed a tremendous upsurge in recent years, both in academia and industry; this is mainly attributed to their unprecedented operating conditions and a variety of commercially viable applications. Because of their dependence on scarce battery power, communication protocols need to be energy efficient. However, finding the optimal solution is challenging as it needs to consider the whole communication stack at once. In this paper, we propose an approach that aims at optimizing jointly L2 (link) and L3 (routing) protocols. We design 1-hopMAC, a communication architecture grouping MAC and routing layers which avoids 1-hop neighborhood knowledge. 1-hopMAC can be combined, among others, with a geographic or gradient based routing protocols. We present an analytical study of energy consumption to point out the optimal configuration of 1-hopMAC

Centroid virtual coordinates - A novel near-shortest path routing paradigm

Geographic routing has received increasing attention in the context of Wireless Sensor Networks since it frees the network from the energy-demanding task of building and maintaining a structure. It requires however each node to know its position, which may be a prohibitive assumption for many applications. To this end, some prior work has focused on inferring a nodes location from a set of location-aware anchor nodes. In this work, we free ourselves from positioning techniques and anchor nodes altogether, and introduce and analyze the concept of virtual coordinates. These coordinates are chosen randomly when a node is switched on, and are updated each time the node relays a packet. As this process goes on, the virtual coordinates of the nodes converge to a near-optimal state. When using a greedy geographic approach on top of these coordinates, we show that the number of hops to reach the destination exceeds the shortest path by a few percent only. Moreover, our approach guarantees delivery even when nodes appear/disappear in the network, and under realistic transmission models. We analytically prove the correctness of our protocol. Moreover, extensive simulations are used to show that our position-free solution outperforms existing geographic protocols - such as Greedy-Face-Greedy (GFG) or Greedy Perimeter Stateless Routing (GPSR) - in terms of energy-efficiency, path length and robustness.

On using Virtual Coordinates for Routing in the Context of Wireless Sensor Networks

For low-energy, low-throughput Wireless Sensor Networks, geographic forwarding avoids creating and maintaining a structure using clustering or gradient construction. Yet, geographic forwarding assumes position-awareness, which may be not realistic. In this paper, we propose to use virtual coordinates. Each node determines its [x,y] position in a virtual space based on a random or pseudo-random process. It uses these coordinates to route information with geographical-inspired routing protocols. Extensive simulation shows that this approach can be very efficient for low-throughput WSN.

Capillary networks: a novel networking paradigm for urban environments

In this paper, we present our vision of the networking challenges that are yielded by the rise of Smart Cities. Smart Cities leverage massive data collected by sensors, connected devices, social applications,... for proving a whole set a new services to the citizens. However, there is a lack of reflexion on the networking solutions that enable these services, from the gathering of sensed data to the dissemination of digital services. We identify the emerging needs of Smart Cities, focus on the capillary networks paradigm which unify the wealth of wireless connectivity available in urban environment, and present the research issues it yields.

Geographic Forwarding in Wireless Sensor Networks with Loose Position-Awareness

Geographic-based routing techniques are promising for wireless sensor networks, which suffer from severe energy constraints and a low throughput nature. In its simplest form, greedy geographic forwarding faces the problem of a low delivery ratio. Other protocols use the right hand rule to guarantee delivery. They nevertheless assume nodes know their exact position, whereas positioning systems offer only limited accuracy. In this paper, we propose to use path-recording mechanisms, where nodes append their identifier to the header of the message, together with geographic forwarding. While yielding a comparable number of hops for a message to reach destination than existing routing protocols with guaranteed delivery, this technique offers guaranteed delivery regardless of the positioning accuracy. This makes path-recording particularly suitable for real-world wireless sensor network implementations.

Temporal Bounds for TTA : Validation

In the context of real-time fault-tolerant architecture, as TTA (Time-Triggered Architecture), the temporal validation of the system behavior is very important. Indeed, the fault-tolerant mechanism execution must respects several temporal constraints. To validate the mechanism behaviors, and to give their maximum execution time (temporal bound), we propose here a temporal validation methodology for TTA. This methodology uses the UPPAAL tool, based on the timed automata and the model-checking analysis. This methodology allows us to extract the temporal bounds of the TTA services.

Using virtual coordinates for wireless sensor networks: Proof-of-concept experimentation

Routing in a multi-hop wireless network with lowcost nodes is still a challenging task, and specific ultra-low power solutions need to be investigated for WSNs. Geographic routing protocols have been designed, analyzed and simulated. Yet, early experimental trials show that they fail dramatically when faced with real-world constraints such as lossy links. Experimental studies are needed as a complement to analysis and simulation.