Publications Scientifiques

In WSN, it is not often desirable to use the GPS technology. Indeed, the use of GPS is expensive and may reduce the overall network performance. Moreover, indoor reception of the GPS signal is not possible. The Link Quality Indicator (LQI) is defined in the 802.15.4 standard, but its context of use is not specified in this standard. Some works on the LQI, few of which are field experiments, have shown that the LQI decreases as the distance increases. However, the challenge of clustering mechanisms is to form the smallest number of clusters by maximizing distances separating cluster heads to provide an efficient cover of the network and also minimizes the cluster overlaps. This reduces the amount of channel contention between clusters, and also improves the efficiency of algorithms that run at the level of the cluster heads. Therefore we propose an analytical model based on the use of the LQI in order to derive an optimally one-dominating set in which the smaller distance separating two cluster heads is improved.

The Link Quality Indicator (LQI) is defined in the 802.15.4 standard, but its context of use is not specified in this standard. Some works on the LQI, few of which are field experiments, have shown that the LQI decreases as the distance increases. In WSN, it is not often desirable to use the GPS technology. Indeed, the use of GPS is expensive and may reduce the overall network performance. Moreover, indoor reception of the GPS signal is not possible. However, in cluster formation, it is quite important to sufficiently outspread the clusterheads (or caryommes) in order to improve the network efficiency. Therefore we propose a LQI based d-clustering protocol (LQI-DCP) which produces clusters of which each clusterhead has a better positioning regarding the locations of other clusterheads. Simulation results show that the caryommes resulting from LQI-DCP are sufficiently outspread. LQI-DCP also reduces the density of clusterheads and then improves the WSN energy efficiency, while each sensor remains still at less than d-hops from a caryomme.

The Link Quality Indicator (LQI) is defined in the 802.15. 4 standard, but its context of use is not specified in this standard. Some works on the LQI, few of which are field experiments, have shown that the LQI decreases as the distance increases. In WSN, it is not often desirable to use the GPS technology. Indeed, the use of GPS is expensive and may reduce the overall network performance. Moreover, indoor reception of the GPS signal is not possible. However, in cluster formation, it is quite important to sufficiently outspread the clusterheads (or caryommes) in order to improve the network efficiency. Therefore we propose a LQI based d-clustering protocol (LQIDCP) which produces clusters of which each clusterhead has a better positioning regarding the locations of other clusterheads. Simulation results show that the caryommes resulting from LQIDCP are sufficiently outspread. LQI-DCP also reduces the density of clusterheads and then improves the WSN energy efficiency, while each sensor remains still at less than d-hops from a caryomme.

In this paper, we propose two database updating models for homogeneous and auto configurable sensor network deployed in a truck without base station. In the first model, a Virtual Base Station (VBS) is periodically elected to act as classical base station for a given period of time. VBS election algorithm is based on the remaining energy level of each node at the time of selection of the VBS. The second idea deals with Energy aware Wait and See (WaS) protocol which manages update requests to avoid collisions. Like VBS, this protocol is also based on energy. Simulation results show that VBS and WaS models introduce very low overhead with respect to the classical network with permanent base station.

UNIV-PARIS1 INRAP UNIV-TLSE2 CNRS TELECOM-SUDPARIS UT1-CAPITOLE LARA IRIT IRIT-RMESS IRIT-T2RS UMR8215 IRIT-ASR IRIT-INPT TOULOUSE-INP UNIV-UT3 UT3-TOULOUSEINP INSTITUT-MINES-TELECOM

In a classical wireless sensor network, a base station is often present to ensure efficient data collection. Endowed with typical hardware feature, especially with high energy level and good stockpiling capabilities, the base station completes the architecture as a required component for a wide range of applications. However, there are some projects where base station deployment should be avoided without reducing network efficiency. Thus, in a cold chain supervision project, itŠs not necessary to add base station to a wireless sensors network deployed inside a food or a medical truck. In this manner, it is a low-budget sensors network deployment. Moreover, such applications have to replicate data across all nodes and to maintain same information as well. In this paper, we propose databases updating model for homogeneous wireless sensors network deployed in a food truck without any base station. In this model, Virtual Base Station (VBS) is the node which is elected to act as classical base station during a specific period of time. Virtual Base Station (VBS) electionŠs algorithm is based on the remaining energy for each node and latest Virtual Bases Station (VBS) to reduce overall energy spent by network. Simulation results (using MATLAB) show that VBS model introduces very low overhead with respect to the classical network with permanent Base Station (BS).