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

Broadcast Strategies with Probabilistic Delivery Guarantee in Multi-Channel Multi-Interface Wireless Mesh Networks

Multi-channel multi-interface Wireless Mesh Networks permit to spread the load across orthogonal channels to improve network capacity. Although broadcast is vital for many layer-3 protocols, proposals for taking advantage of multiple channels mostly focus on unicast transmissions. In this paper, we propose broadcast algorithms that fit any channel and interface assignment strategy. They guarantee that a broadcast packet is delivered with a minimum probability to all neighbors. Our simulations show that the proposed algorithms efficiently limit the overhead

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

Topologie Virtuelle pour Réseaux Hybrides

La gestion de la mobilité dans les réseaux hybrides, réseaux sans fil multisauts connectés à Internet, reste un problème complexe. Il est en effet nécessaire que tout noeud d'un réseau ad hoc puisse joindre et =EAtre joignable d'Internet. La plupart des propositions existantes essaient de calquer les approches des réseaux filaires, bien qu'elles soient peu optimisées pour les réseaux sans fil multisauts. Dans ce mémoire, nous proposons en premier lieu la création d'un backbone virtuel. Il nous permet de réduire les dépenses en énergie, de hiérarchiser les rôles et d'optimiser les communications de broadcast problématiques dans les réseaux ad hoc. Nous intégrons de plus les points d'accès wifi à ce backbone afin de créer un prolongement naturel de la connexion Internet. Puis, dans un deuxième temps, nous regroupons les noeuds proches géographiquement pour créer de véritables zones de services, intégrées au backbone. Ces zones de services, avec des chefs attitrés, peuvent prendre en charge des fonctionnalités de localisation des mobiles, de paging, de diffusion des informations de topologie Ces structures maintenues dynamiquement constituent un véritable socle pour développer de nouvelles fonctionnalités à destination des réseaux hybrides

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

Mobility management in Multihops Wireless Access Networks

International audienceAd hoc networks are spontaneous networks of mobile nodes which use wireless communications. The nodes must collaborate to route and forward data packets from a source to a destination. We consider multihops wireless access networks which are ad hoc networks connected to the Internet via Access Points (AP). A terminal can send and receive data packets to and from the Internet. To achieve this goal, we propose here a micro-mobility management solution. The solution uses a virtual backbone to disseminate information and to limit the overhead. The proposition mixes the reactive and the proactive approaches to propose a trade-off between the delay and the overhead. In upload, each node has a default proactive route toward the AP introducing no latency. In download, the AP initiates a reactive localization to find a route to the destination inside the ad hoc area, reducing the overhead. A solution of paging with several AP and a solution of power-energy saving are also proposed

About the Self-Stabilization of a Virtual Topology for Self-Organization in Ad Hoc Networks

International audienceAd hoc networks are spontaneous wireless networks without any wired infrastructure, composed of mobile terminals. We assume that nodes must collaborate to set up an efficient network, such a collaboration requiring a self-organization in the network. We proposed a virtual structure to organize the network: the backbone is a connected structure helping to optimize the control traffic flooding. Clusters form services area, hierarchizing the network, electing one leader per cluster. Since the ad hoc topology is volatile, the self-stabilization of the algorithms is vital. The algorithms for both the construction and the maintenance are analytically studied to prove the self-stabilization of the proposed self-organization. Thus, the virtual structure is efficient and very scalable, a local topology change impacting only locally the virtual structure. Finally , simulations investigate the behavior and the performances of the 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

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