On Cross-Layer Routing in Wireless Multi-Hop Networks

International audienc

On Delay Fairness for Multiple Network Coding Transmissions

This paper studies the unfairness issues of network coding in multi hop wireless networks. Most of the work on network coding focuses on the obtained throughput gain. They show that mixing lineally the packets at the intermediate nodes is capacity-achieving. However, network coding schemes designed only to maximize the throughput could be unfairly biased. The reason is that by mixing different flows, packets destined to one destination in order to be decoded need to wait for the reception of the whole mixed set of encoded packets that may be totally independent in terms of final destination. This may lead to highly unfair delay for small block data. To mitigate this unfairness, relay nodes may mix only packets going to the same destination. We call this strategy FairMix. Although FairMix may limit the maximum attainable throughput, it aims to make distinct for decoding delay of each destination corresponding to the size of the data block. In order to investigate this trade off, we compare the FairMix performance with a naive network coding which mixes packets destined to different destinations. The simulation under lossy wireless links, limited memory and bandwidth resources, and different block sizes shows that FairMix is effective in improving fairness among destinations in comparison to naive network coding

A Link Quality and Congestion-aware Cross layer Metric for Multi-Hop Wireless Routing

International audienceWireless networks suffer from random variations in channel and network condition. This leads to poor performance in multi-hop wireless networks specially with a conventional non-flexible routing. To cope with instability of wireless links, a cross-layer routing that supports adaptivity and optimization across lower layers of protocol stack is needed. Cross layer routing intends to play an essential role in improving the performance of wireless networks but requires a careful attention on the choice of the metric. In this paper we propose a new link-quality and congestion aware metric for multi-hop wireless routing which is obtained from MAC layer. We show that still having a path with reasonable length our proposed metric improves the performance of routing in terms of end-to-end delay and throughput in comparison to minimum-hop count metric

Link-Quality aware routing in IEEE 802.11 multi-hop networks

Les réseaux sans fil multi-sauts grâce à leur flexibilité et leur rapidité de mise en œuvre permettent le déploiement à faible coût d'une infrastructure routage pouvant notamment servir à étendre la couverture des réseaux filaires. Leurs caractéristiques et les perspectives qu'ouvrent de tels réseaux ont attiré l'attention de la communauté de la recherche afin d'évaluer et de proposer des solutions notamment en termes de routage afin de permettre un développement efficace. La qualité des communications sans fil dépend de nombreux facteurs comme les effets de la propagation multi chemins ou les interférences entre les transmissions des différents utilisateurs. Aussi cette qualité de transmission peut varier de manière plus ou moins drastique au cours du temps en fonction des modifications de l'environnement d'exécution. Les singularités de ces transmissions radios ne permettent donc pas l'utilisation telle quelle des protocoles de routage développés originellement pour les réseaux filaires. En effet, ceux-ci se révèlent même extrêmement inefficaces dans ces nouveaux environnements. L'utilisation du nombre de sauts comme métrique de routage ne permet en effet pas de prendre en compte la diversité et la variabilité de la qualité des liens sans fil. Une solution prometteuse pour traiter ce problème consiste à intégrer au routage des informations relatives à la qualité des liens. Aussi, les protocoles des différentes couches doivent alors interagir pour s'échanger des informations. La couche réseau prend ainsi conscience du statut des couches inférieures et c'est que nous appellerons dans cette thèse le routage basé sur la qualité des liens. Le but principal de cette thèse est donc de montrer comment le routage inter-couche, au travers de l'utilisation d'une métrique adaptée et grâce à une méthode de mesure pertinente peut considérablement améliorer les performances du routage. Néanmoins, elle met en évidence également les effets secondaires de l'adaptation des chemins en montrant notamment en quoi une grande oscillation entre les chemins peut être nocif pour des applications sensibles aux délais.Après un court état de l'art sur les différents protocoles de routage, nous définissons dans ce mémoire différents critères pour définir une métrique pertinente basée sur la qualité des liens. Nous présentons ensuite une étude sur les méthodes de mesure de ces métriques, puis nous proposons une métrique réaliste de qualité des liens, basée sur l'efficacité de la transmission des trames (FTE) observée au niveau de la couche MAC. Cette nouvelle métrique reflète ainsi les variations du taux d'erreur de transmission liées soit à une faible qualité du lien, soit à un important taux de congestion dans la cellule. Nous montrons que l'utilisation de cette métrique inter-couche permet d'améliorer sensiblement les performances du routage. Nous proposons également un schéma de méthodes de mesures précises et générant un faible surcoût appelé QualRoute. Celui-ci utilise la nature en diffusion des supports de communication sans fil pour mettre en place un mécanisme coopératif de mesure de la qualité des liens pour lesquels on ne dispose de pas assez de trafic de données pour évaluer le taux d'erreur de transmission. Il utilise l'information observée par chaque noeud sur le trafic émis par ses voisins pour estimer à faible coût la qualité des liens avec ces derniers. Nous avons enfin évalué l'effet de la fluctuation du choix des chemins sur le routage basé sur la qualité des chemins. Nous avons défini et montré en quoi la sensibilité d'une métrique ou la fréquence de mise à jour de métrique pouvait augmenter le débit des applications. Cependant cette optimisation du débit se fait en modifiant fréquemment le choix du chemin, et peut conduire à une diminution importante de la gigue qui peut s'avérer néfaste pour les applications sensibles aux variations de délaisPARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Mathématiques rech (751052111) / SudocSudocFranceF

Cross Layering in Wireless Multi-hop Networks

International audienc

A Content-based Network Coding to Match Social Interest Similarities in Delay Tolerant Networks

Abstract—Considering users ’ social characteristics leads to better exploitation of network coding in delay tolerant networks. We present a content-based network coding that aims to match the social interests similarities (i.e., same profession, hobbies, interests, etc.) of people in a community. We aim to provide a more adaptive-to-social-network coding and lower decoding delay for the users that are interested in different contents. This approach has the potential to open interesting research horizons. I

Towards a Fault-Tolerant Wireless Sensor Network Using Fault Injection Mechanisms: A Parking Lot Monitoring Case

A Wireless Sensor Network (WSN) requires a high level of robust and fault tolerant sensing and actuating capabilities, specially when the application aims to gather delicate and urgent data with reasonable latency. Hence, verifying the behavior properties under the presence of faults remains an important step in developing an application over a WSN. A comprehensive study on characterization and understanding of all the possible faults is required in order to generate and inject 'any' known error to the system. In order to ensure appearance of all the faults and possible bugs in the system, conception and developing a fault injector which generates and injects any requested fault to the system is promising. This becomes more important and critical when the fault happens very rarely, while due to Murphy's law it happens certainly along the network life. Considering that occurrence of faults depends heavily on the specifications of the use case, in this paper we concentrate on a sensor network which aims to detect the presence of vehicles on parking lots. We try to categorize and characterize the faults driven by this system as the first step of developing a fault injector

On the Link-Quality Aware Routing in Wireless Multi-Hop Networks: A Throughput-Stability Trade-Off Study

International audienceThere are considerable researches focused on routing in wireless multi-hop networks dealing with random and unpredictable channel variations. As it is well-known that using the shortest path in terms of number of hops often leads to poor performance, most of the recent research efforts propose various link quality aware metrics. Yet, there is not many works addressing the stability issue of link quality aware routing which can be extremely important specially in providing quality of service for jitter sensitive applications. In this paper, we address the stability vs. throughput trade-off. We argue that a more reactive routing responds faster to link quality changes. This leads to detect the lossy channel faster and so converges to the higher quality path in a shorter time. Meanwhile, fast reacting to channel variations may produce higher path flapping and consequently higher jitter level

Link Quality Measurement Enhacement for Routing in Wireless Mesh Networks

International audienceIn this paper we introduce a novel distributed and robust link-quality measurement framework, called QualRoute. It exploits the existing traffic in the network in order to estimate accurately the quality of the links. Different from existing methods, our proposed scheme takes advantage of the broadcast nature of the wireless medium, and sets up an asynchronous cooperation between neighbors without any extra signaling between the node pairs. The simulation results suggest that the route derived from QualRoute yields to noticeably better performance than the traditional shortest path routes. Moreover, a comparison with a similar link-quality metric which is measured differently confirms the significant impact of the measurement scheme on the overall performance

On using network coding in multi-hop wireless networks

International audienceThis paper studies the unfairness issues of network coding in multi hop wireless networks. Most of the work on network coding focuses on the obtained throughput gain. They show that mixing lineally the packets at the intermediate nodes is capacity-achieving. However, network coding schemes designed only to maximize the throughput could be unfairly biased. The reason is that by mixing different flows, packets destined to one destination in order to be decoded need to wait for the reception of the whole mixed set of encoded packets that may be totally independent in terms of final destination. This may lead to highly unfair delay for small block data. To mitigate this unfairness, relay nodes may mix only packets going to the same destination. We call this strategy FairMix. Although FairMix may limit the maximum attainable throughput, it aims to make distinct for decoding delay of each destination corresponding to the size of the data block. In order to investigate this trade off, we compare the FairMix performance with a naive network coding which mixes packets destined to different destinations. The simulation under lossy wireless links, limited memory and bandwidth resources, and different block sizes shows that FairMix is effective in improving fairness among destinations in comparison to naive network coding