Ad hoc routing protocols with multipoint relaying

National audienceMultipoint relays have been introduced in the proactive protocol OLSR in order to optimize the flooding overhead of control traffic. In this paper we show that multipoint relaying can be used as well in reactive protocols in order to save overhead in route discovery. To this end we specify a very simple reactive protocol called MPRDV (Multipoint Relay Distance Vector protocol). In MPRDV route requests and route replies are all flooded via Multipoint Relays (MPR). They both open routes to their originators. Route repairs are performed by new route request flooding. We show with simulation that the use of MPR flooding does not lead to the control traffic explosion that we experience with basic reactive protocol in presence of frequent route discovery and failure. MPR provide also another optimization since it tends to offer optimal routes to data packets and so increases the protocol performances

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

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

Performance Evaluation of Broadcasting Protocols for Ad Hoc and Sensor Networks.

In ad hoc and sensor networks, the simplest and most widely used approach to broadcast is blind flooding, which lets every node in the network to rebroadcast a receiving packet to all its neighbors. This causes redundancy of broadcast packets and results in unnecessary collision and bandwidth waste. To overcome these problems, a number of research groups have proposed more efficient broadcasting schemes with the goal of minimizing the re-transmissions, while still guaranteeing that a broadcast packet is delivered to all the nodes in the network. Multipoint relay (MPR) and dominating set (DS) based broadcasting schemes can effectively improve the broadcasting efficiency while providing reliable broadcasting. The neighbor elimination scheme (NES) can improve any broadcasting protocol as an added feature. In this paper, we evaluate the performance of MPR (source dependent), MPR-DS (source-independent MPR), and DS based broadcasting protocols. We add NES to these three schemes separately and evaluate the performance of the resulted protocols. In our experiments, we use the random unit graphs to model the ad hoc and sensor networks. Each of the studied protocols has scenarios under which it has the best performance. Our experiments demonstrate that, without applying neighbor elimination scheme, MPR based protocol requires fewest retransmissions (however, each retransmission is with a longer message including list of forwarding neighbors). DS and MP-RDS schemes benefit significantly from the neighbor elimination technique in terms of the ratio of re-broadcasting nodes and the message redundancy on both transmitting and non-transmitting nodes, while MPR benefits marginally. After adding the neighbor elimination scheme, three new protocols behave almost equally well in terms of rebroadcast message counts. MPR-NES method is narrowly the best when the message that is broadcasted is very large one, and the network is dynamic. MPR-DS-NES is narrowly the best when the broadcast message is not very large, and the network is stable (this method requires the third round of preprocessing HELLO messages). Overall, DS-NES appears to be the most robust, taking all measurements and parameters into acount, because it remains competitive under all scenarios, and has significant advantages over MPR-DS-NES in dynamic scenarios, and significant advantages over MPR-NES when the broadcast message is not very large, because MPR has overhead in packet lengths