Cluster-based Scheduling for Cognitive Radio Sensor Networks

International audienceIn this paper, we define a cluster based scheduling algorithm for Cognitive Radio Sensor Networks (CRSNs). To avoid inter-clusters collision, we assign fixed channels only to nodes having one-hop neighbors out of their clusters. We denote these nodes as specific nodes. Previous studies assign distinct channels to whole neighbor clusters to avoid inter-clusters collision. Our objective is to optimize the spatial reuse and to increase the network throughput while saving sensors energy. We start by assigning channels only to the specific nodes. Once the problem of inter-clusters collision is solved, each cluster head (CH) schedules the transmissions in its cluster independently. For the cluster members that are specific nodes, the CH assigns only time slots because the channel assignment is already done. For other cluster members (CMs) (not specific nodes), the CH assigns the pair (channel, slot). Two solutions are proposed in this paper to schedule the CMs: The Frame Intra Cluster Multichannel Scheduling algorithm denoted Frame-ICMS and the Slot Intra Cluster Multichannel Scheduling algorithm denoted Slot-ICMS. We evaluate the performance of these algorithms in case of accurate PUs activity detection and in case of bad PUs activity estimation. We prove that our proposals outperform an existing one especially in terms of energy saving

Optimization of IEEE 802.15.4 : overview, theoretical study and simulation

In this paper we study, through theoretical analysis and simulation, the impact of Beacon Order (BO) and Superframe Order (SO) parameters of IEEE 802.15.4 on the networks performance and we investigate their optimal values for different classes of traffic. The traffic is dimensioned according to the requirements of the CANet project in which a cane becomes a mean of communication and a surveillance system embedding several sensors to monitor the elderly health and environment(voice, pressure, temperature, etc.). The cane's sensors impose different QoS constraints. Depending on the expected throughput, a sensor's traffic will fall within one of three classes that we defined. Therefore, in order to ease the understanding of our optimization, we introduce a classification scheme which applies to the existing quality of service algorithms. We derive by theoretical study the optimal values of BO and SO that should be used to fit each traffic class QoS requirements and we validate our results by simulation

Link Availability Aware Routing Metric For Wireless Mesh Networks

International audienceThis paper investigates the design of effective routing metrics in the purpose of network resources optimization and the satisfaction of users QoS requirements. Using several real experiments, we point out the shortcoming of the Expected Transmission Count (ETX) metric for eventual optimizations towards a more efficient routing. Experiments were carried out into an heterogeneous IEEE 802.11n based network running with OLSR routing protocol and have shown that ETX presents several shortcoming resulting in inaccurate estimation of the link quality and then of the routing decision. This paper presents improvements of the ETX metric based on link availibility for accurately finding high-throughput paths in multihop wireless mesh networks

Impact des interférences dans un réseau sans fil multi-sauts

National audienceCe papier introduit le problème des interférences dans les réseaux sans fil multi-sauts. Nous nous adressons à deux types d'interférences : intra-flux et inter-flux et nous discutons de leur impact sur l'estimation des ressources disponibles notamment la bande passant

Transmission de la voix sur des liens sans fil IEEE 802.15.4

National audienceL'évolution de la technologie au niveau des composants électroniques et informatiques a permis la naissance de plusieurs projets comme CANet qui a comme but l'amélioration des conditions de vie, particulièrement pour les personnes âgées. Ce projet permet aux personnes âgées de conserver les mêmes conditions de vie, tout en surveillant leur état de santé sans les déranger. Une des fonctionnalités de CANet est de dialoguer oralement avec une personne via sa canne de marche en utilisant un lien sans fil. Dans ce papier, nous étudions le meilleur codec qui doit être utilisé avec la norme IEEE 802.15.4

Performance evaluation of IEEE 802.15.6 CSMA/CA-based CANet WBAN

International audienceIn the recent few years, Wireless Body Area networks (WBANs) showed what can be done remotely to greatly improve healthcare systems and facilitate the life to elderly. One of the recent ehealth projects is CANet which aims at embedding a WBAN into a cane to monitor elderly/patients. Our main goal in this paper is to evaluate the performances of the emerging standard IEEE 802.15.6 when applied on different sensors from CANet eHealth project. At this end, we defined a small scenario extracted from CANet, and we assigned IEEE 802.15.6 priorities to the selected cane sensors according to their inherent characteristics. We considered further the mandatory RAP period of IEEE 802.15.6 superframe under the beacon period with superframes mode since it supports both normal and urgent traffic. Our results showed that the contention access behavior of this considered model of simulation depends on several constraints (including the nature of the studied application and the traffic types and frequency). This would be necessarily taken into account to get the most advantage of all features offered by WBANs standard IEEE 802.15.6. Keywords—Medium Access Control (MAC), wireless body area networks (WBANs), E-health, CANet project, wireless sensor networks (WSN), IEEE 802.15.6

Presentation and analysis of a new technology for low-power wireless sensor network

International audienceThe tremendous and rapid development in sensors technology allowed their application in various fields requiring monitoring, such as, transportations, rare species surveillance, agriculture, military activities, medical field, etc. Due to their intrinsic constraints and limitations, several dedicated MAC protocols have been designed for wireless sensor networks and whose main objectives are bandwidth optimization while keeping very low energy consumption. One of the newest proposals is ANT which is emerging as a widely used MAC protocol for wellness and sports sensor devices. In this paper, we give a comprehensive overview of ANT/ANT+ and a comparison between ANT and two established standards: Bluetooth Low Energy (BLE) and 802.15.4/4a. We detail also some practical experiments we conducted to evaluate some characteristics of ANT

Experimental Performance Analysis of Routing Metrics in Wireless Mesh Networks

International audienceThis paper provides a description of a wireless mesh network testbed setup and a measurement-based performance evaluation of the Optimized Link State Routing (OLSR) protocol [7] under three different routing metrics. The considered metrics include hop-count, ETX and ETT. The network performances are evaluated in an indoor testbed formed by heterogeneous MIMO devices. A part of our tests was about the impact of 802.11n features on the network performances showing the importance of lower layers consideration. Our measurements point out the shortcoming of each metric and eventual optimizations towards a more efficient routing. Experimental results show that OLSRETT outperforms OLSR-ETX and OLSR-hopcount significantly in terms of packet loss, end-to-end delay, and efficiency

Alternance synchrone pour la conservation d'énergie dans les réseaux ad hoc

Les réseaux ad hoc sont des réseaux caractérisés par des ressources limitées en énergie. La conservation d'énergie s'avère donc être un facteur primordial pour la durée de vie du réseau. Plusieurs propositions existent à cet effet dont les plus efficaces se situent au niveau liaison de données comme le mécanisme PSM défini par le standard 802.11. Nous présentons dans ce rapport un nouveau mécanisme, appelé Power-Aware Alternation(PAA) qui se base sur l'élimination de l'activité réseau d'un ensemble de noeuds durant certaines périodes afin de conserver leur énergie. Les noeuds choisissent des noeuds supporteurs avec qui ils vont alterner des périodes d'activité et d'inactivité. Ce mécanisme a comme avantage de mieux conserver la connectivité du réseau. Nous détaillons dans ce rapport la conception de notre mécanisme et nous effectuons une évaluation de ses performances par simulation. Cette étude nous a permis de comparer les performances de PAA à celles de PSM et TA-PSM en terme de gain en énergie et en terme de blocage du trafic. Les résultas nous ont démontré que dans le cadre d'un réseau de noeuds peu mobiles et en présence de trafic uniformément distribué entre les noeuds du réseau, PAA apporte un gain en énergie meilleur que celui de PSM tout en assurant le même taux de délivrance du trafic

Towards an Optimized Traffic-Aware Routing in Wireless Mesh Networks

International audienceIn this paper we study through simulations the impact of PHY/MAC protocols on higher layers. In a comparative way, we investigate the effectiveness of some protocols when they coexist on a wireless mesh network environment. Results show that PHY/MAC parameters have an important impact on routing performances. Based on these results, we propose two tra c-aware routing metrics based on link availability. The information about the link availability/occupancy is picked up from lower layers using a cross-layer approach. The rst metric is load-sensitive and aims to balance the tra c load according to the availability of a link to support additional ows. The second metric reproduces better the capacity of a link since it is based on its residual bandwidth. Using several real experiments, we have shown that our proposals can accurately determine better paths in terms of throughput and delay. Our experiments are carried out into an heterogeneous IEEE 802.11n based network running with OLSR routing protocol