An analysis of the lifetime of OLSR networks

The Optimized Link State Routing (OLSR) protocol is a well-known route discovery protocol for ad-hoc networks. OLSR optimizes the flooding of link state information through the network using multipoint relays (MPRs). Only nodes selected as MPRs are responsible for forwarding control traffic. Many research papers aim to optimize the selection of MPRs with a specific purpose in mind: e.g., to minimize their number, to keep paths with high Quality of Service or to maximize the network lifetime (the time until the first node runs out of energy). In such analyzes often the effects of the network structure on the MPR selection are not taken into account. In this paper we show that the structure of the network can have a large impact on the MPR selection. In highly regular structures (such as grids) there is even no variation in the MPR sets that result from various MPR selection mechanisms. Furthermore, we study the influence of the network structure on the network lifetime problem in a setting where at regular intervals messages are broadcasted using MPRs. We introduce the ’maximum forcedness ratio’, as a key parameter of the network to describe how much variation there is in the lifetime results of various MPR selection heuristics. Although we focus our attention to OLSR, being a widely implemented protocol, on a more abstract level our results describe the structure of connected sets dominating the 2-hop neighborhood of a node

Heuristics for Network Coding in Wireless Networks

Multicast is a central challenge for emerging multi-hop wireless architectures such as wireless mesh networks, because of its substantial cost in terms of bandwidth. In this report, we study one specific case of multicast: broadcasting, sending data from one source to all nodes, in a multi-hop wireless network. The broadcast we focus on is based on network coding, a promising avenue for reducing cost; previous work of ours showed that the performance of network coding with simple heuristics is asymptotically optimal: each transmission is beneficial to nearly every receiver. This is for homogenous and large networks of the plan. But for small, sparse or for inhomogeneous networks, some additional heuristics are required. This report proposes such additional new heuristics (for selecting rates) for broadcasting with network coding. Our heuristics are intended to use only simple local topology information. We detail the logic of the heuristics, and with experimental results, we illustrate the behavior of the heuristics, and demonstrate their excellent performance

Study of Multipoint-to-Point and Broadcast Traffic Performance in RPL

Recent trends in Wireless Sensor Networks (WSNs) have suggested converging to such being IPv6-based. to this effect, the Internet Engineering Task Force has chartered a Working Group to develop a routing protocol specification, enabling IPv6-based multi-hop Wireless Sensor Networks. This routing protocol, denoted RPL, has been under development for approximately a year, and this memorandum takes a critical look at the state of advancement hereof: it provides a brief algorithmic description of the protocol, and discusses areas where -- in the authors view -- further efforts are required in order for the protocol to become a viable candidate for general use in WSNs. Among these areas is the lack of a proper broadcast mechanism. This memorandum suggests two such broadcast mechanisms, both aiming at (i) exploiting the existing routing state of RPL, while (ii) requiring no additional state maintenance, and studies the performance of RPL and of these suggested mechanisms.Les tendances récentes dans les réseaux de capteurs sans fil (Wireless Sensor Networks --WSNs) suggèrent une convergence vers des réseaux IPv6. A cet effet, l'IETF (Internet Engineering Task Force) a mis sur pied un groupe de travail pour élaborer la spécification d'un protocole de routage s'appliquant aux réseaux de capteurs sans fil multi-hop basés sur IPv6. Ce protocole de routage, appelé RPL, est en cours de développement depuis environ un an. Cet article présente un examen critique de son état d'avancement. Après une brève description algorithmique du protocole, une discussion est proposée sur des domaines, où selon les auteurs, des efforts supplémentaires sont nécessaires pour que le protocole puisse devenir candidat viable à une utilisation généralisée dans les réseaux de capteurs sans fil. Parmi ces domaines se trouve l'absence d'un mécanisme de diffusion approprié. Cet article suggère deux mécanismes de diffusion, tous deux avec l'objectif (i) de pouvoir exploiter l'état de routage actuel du protocole RPL (ii) sans requérir à une maintenance supplémentaire de cet état. Il étudie également les performances de RPL et des deux mécanismes de diffusion proposés