RTXP : A Localized Real-Time Mac-Routing Protocol for Wireless Sensor Networks

Protocols developed during the last years for Wireless Sensor Networks (WSNs) are mainly focused on energy efficiency and autonomous mechanisms (e.g. self-organization, self-configuration, etc). Nevertheless, with new WSN applications, appear new QoS requirements such as time constraints. Real-time applications require the packets to be delivered before a known time bound which depends on the application requirements. We particularly focus on applications which consist in alarms sent to the sink node. We propose Real-Time X-layer Protocol (RTXP), a real-time communication protocol. To the best of our knowledge, RTXP is the first MAC and routing real-time communication protocol that is not centralized, but instead relies only on local information. The solution is cross-layer (X-layer) because it allows to control the delays due to MAC and Routing layers interactions. RTXP uses a suited hop-count-based Virtual Coordinate System which allows deterministic medium access and forwarder selection. In this paper we describe the protocol mechanisms. We give theoretical bound on the end-to-end delay and the capacity of the protocol. Intensive simulation results confirm the theoretical predictions and allow to compare with a real-time centralized solution. RTXP is also simulated under harsh radio channel, in this case the radio link introduces probabilistic behavior. Nevertheless, we show that RTXP it performs better than a non-deterministic solution. It thus advocates for the usefulness of designing real-time (deterministic) protocols even for highly unreliable networks such as WSNs

About the Capacity of Flat and Self-Organized Ad Hoc and Hybrid Networks

Ad hoc networking specific challenges foster a strong research effort on efficient protocols design. Routing protocols based on a self-organized structure have been studied principally for the robustness and the scalability they provide. On the other hand, self-organization schemes may decrease the network capacity since they concentrate the traffic on privileged links. This paper presents four models for evaluating the capacity of a routing schemes on 802.11 like networks. Our approach consists in modeling the radio resource sharing principles of 802.11 like MAC protocols as a set of linear constraints. We have implemented two models of fairness. The first one assumes that nodes have a fair access to the channel, while the second one assumes that on the radio links. We then develop a pessimistic and an optimistic scenarii of spatial re-utilization of the medium, yielding a lower bound and an upper bound on the network capacity for each fairness case. Our models are independent of the routing protocols and provide therefore a relevant framework for their comparison. We apply our models to a comparative analysis of the well-known shortest path base flat routing protocol OLSR against two main self-organized structure approaches, VSR, and Wu & Li's protocols. This study concludes on the relevance of self-organized approaches from the network capacity point of view

Resilient networking in wireless sensor networks

This report deals with security in wireless sensor networks (WSNs), especially in network layer. Multiple secure routing protocols have been proposed in the literature. However, they often use the cryptography to secure routing functionalities. The cryptography alone is not enough to defend against multiple attacks due to the node compromise. Therefore, we need more algorithmic solutions. In this report, we focus on the behavior of routing protocols to determine which properties make them more resilient to attacks. Our aim is to find some answers to the following questions. Are there any existing protocols, not designed initially for security, but which already contain some inherently resilient properties against attacks under which some portion of the network nodes is compromised? If yes, which specific behaviors are making these protocols more resilient? We propose in this report an overview of security strategies for WSNs in general, including existing attacks and defensive measures. In this report we focus at the network layer in particular, and an analysis of the behavior of four particular routing protocols is provided to determine their inherent resiliency to insider attacks. The protocols considered are: Dynamic Source Routing (DSR), Gradient-Based Routing (GBR), Greedy Forwarding (GF) and Random Walk Routing (RWR)

On the Performances of the Routing Protocols in MANET: : Classical versus Self-Organized Approaches

International audienceMobile Ad Hoc Networks (MANET) are spontaneous wireless networks of mobile nodes without any fixed infrastructure. MANET are promised to a large spectrum of military or civilian utilizations. Routing is a key topic in such networks: overhead must be minimized, optimizing the delay and reducing the packet losses. Several routing protocols were proposed in the literature but, recently, new routing protocols based on a self-organization, like Virtual Structure Routing (VSR), were proposed. VSR is based on a self-organized structure with an important stability and persistence. In this paper, we aim to quantify the contribution of the self-organization on the routing behavior and performances. We oppose VSR as a self-organized protocol to the classical one: reactive (AODV), proactive (OLSR) and clustered (CBRP). The impact of the mobility and the density, the horizontal and the vertical scalabilities are studied

Structure virtuelle pour une auto-organisation dans les réseaux ad hoc et hybrides

National audienceAd hoc networks are spontaneous wireless networks without any wired infrastructure of mobile terminals. We assume that an efficient network is achieved through a self-organization. Thus, we propose here a virtual structure allowing a self-organization, constituted by both a backbone and services areas. The backbone constitutes a connected structure to gather and disseminate the control traffic, representing a natural prolongation of backbone in wired networks. Services areas structure the network in separating the network in homogeneous zones managed by a clusterhead. Since terminals are mobile, we propose both construction and maintenance procedures in order to maintain an efficient and stable virtual structure, during all the network life. In order to create a stable virtual structure, we introduce a stability metric, depending on several criteria. Finally, a power-energy saving solution is proposed to optimize the network lifetime.Les réseaux ad hoc sont des réseaux spontanés sans fil et sans infrastructure fixe de terminaux mobiles. Nous pensons que l'utilisation efficace d'un tel réseau doit passer par son auto-organisation. Nous proposons ici une topologie virtuelle d'auto-organisation constituée à la fois d'une dorsale et de zones de services. La première, véritable prolongation des dorsales des réseaux filaires, permet de collecter le trafic de contrôle. Les zones de services structurent le réseau en le découpant en zones homogènes possédant chacune un chef. Puisque les terminaux sont mobiles, nous proposons à la fois une procédure de construction et de maintenance afin de maintenir une structure virtuelle stable et efficace tout au long de la vie du réseau. Afin de construire une structure virtuelle stable, nous introduisons une métrique de stabilité, dépendant de plusieurs critères. Enfin, nous proposons une solution d'économie d'énergie afin d'optimiser la durée de vie du réseau

Robustness and Reliability for Virtual Topologies in Wireless Multihop Access Networks

International audienceMobile ad hoc networks (MANet) are a spontaneous collection of mobile terminals. Each node must collaborate in order to structure information exchange. An hybrid network is a MANet connected to Internet via an Access Point (AP). We propose to organize MANet and hybrid networks through a virtual topology. We consider a virtual topology as a hierarchical organization based on the integration of both backbone and clusters. Construction and maintenance procedures of such a virtual topology are detailed and deal with robustness and reliability issues. We present a proactive gratuitous maintenance for our backbone and a new maintenance algorithm for clusters presenting a reduced overhead. Moreover, this improved solution allows to integrate multiple APs in hybrid networks , deleting the previous single point of failure. A method to interconnect backbones is described, which is useful for many applications

Virtual structure routing in ad hoc networks

International audienceRouting protocols are the main issue of ad hoc networks. Because flat propositions (reactive, proactive) are not sufficient and suffer from a lack of performance, new solutions should he investigated and proposed. On the other hand, virtual topologies propose to structure the network and to give a hierarchy between the strongest and the weakest nodes. We propose a new routing protocol, virtual structure routing (VSR), based on a virtual topology including both a backbone and clusters. The backbone is used to collect control traffic and to reduce overhead for route discovery. VSR uses clusters to define a route as a list of cluster IDs. This cluster topology is more stable than the physical topology. Hence, routes are more robust. VSR combines the assets of both flat approaches; intra-cluster routing is proactive while inter-cluster routing is reactive. Finally, routes are computed dynamically and a mechanism for route repair is proposed

A self-organization structure for Hybrid Networks

International audienceThis paper focuses on the self-organization of ad hoc and hybrid networks. We propose to organize networks with two integrated virtual structures: a backbone and clusters. The backbone helps to optimize the flooding of control packets, and to offer a natural prolongation of the backbone of wired networks. Clusters help to hierarchize the network, each of which is managed logically by its clusterhead. Since MANETs are mobile, we propose distributed algorithms for both the construction and the maintenance to preserve an efficient virtual structure despite topology changes. Simulations results exhibit the robustness and persistence of the proposed virtual structure

A virtual structure for hybrid networks

International audienceHybrid networks are heterogeneous networks merging both wireless and ad hoc nodes and where the interconnection to the IP world is an important topic through gateways called AP (access point). Indeed, each node can be contacted and can contact another node in the Internet. To reach that, architectures that support mobility management are studied. The solutions inspired by wired networks are not particularly suited to hybrid networks. We propose to use a virtual dynamic infrastructure including both backbone and clusters. A backbone is suited to spare energy, optimize control traffic diffusion and hierarchize participants. The clusters are intended to create service areas and to handle particularly the mobility management. We present algorithms to both construct and maintain such structure. This dynamic topology is robust according to mobility, and is well suited to implement mobility management and localization procedure. Finally, the number of backbone members and clusters are completely parameterizable according to the environment

The Gain of Network Coding in Wireless Sensor Networking

Wireless Sensor Networks have some well known features such as low battery consumption, changing topology awareness, open environment, non reliable radio links, etc.In this paper, we investigate the benefits of Network Coding Wireless Sensor networking, especially resiliency.One of our main concern is the resiliency in Wireless Sensor Networks.We have seen that resiliency could be described as a multi dimensional metric \cite{5478822,erdene2011enhancing,6423640} taking parameters such as Average Delivery Ratio, Delay Efficiency, Energy Efficiency, Average Throughput and Delivery Fairness into account.Resiliency can then be graphically represented as a kiviat diagram created by the previous weighted parameters.In order to introduce these metrics, previous works have been leaded on the Random Gradient Based Routing, which proved good resiliency in malicious environment.We look for seeing the improvements in term of resiliency, when adding network coding in the Random Gradient Based Routing with malicious nodes