Rahim Kacimi

Experimental Study: Link Quality and Deployment Issues in Wireless Sensor Networks

In this paper, we highlight the extent of the effects of topological specificities on the deployed solutions, which can be useful to refine already proposed models as well as to carry out protocol tuning or adjustments. We present, an intensive experimental study on wireless Link Quality Indicator (LQI). Using Moteivs Tmote Sky sensors, we deployed multiHopLQI algorithm of TinyOS in various network configurations: homogeneous and heterogeneous; straight-line and grid topologies with various transmission power levels and distances. Initially, we study LQI time-varying and try to understand the relationship between transmission power level, distance and link quality and present how some random disturbances due to external (physical changes) or internal phenomena (node movement,power variation) may affect the dynamics of the network. Later, we address impacts and side effects of position and power transmission level of some important nodes in the network like the Base Station in such LQI based algorithms.

Energy-Aware Self-Organization Algorithms for Wireless Sensor Networks

Wireless sensor networks (WSN) have received much attention during the last few years especially with regard to energy consumption and scalability. In this paper, we will focus on mechanisms which may be implemented for small WSNs. So, in the present work, we design energy-aware self-organization algorithms for WSNs in such a context. These algorithms can be used to design effective and adaptive protocols. The first protocol concerns the initialization or the setting up of the network topology under a chain form. The second one (steady-state protocol) implements the communication part or the information exchange between the different nodes of the chain. Our algorithms were dimensioned and validated by an analytical model. We also perform a detailed study of these algorithms by using TOSSIM, a simulation environment for TinyOS, the operating system for the Berkeley sensor nodes. Finally, we achieve an experimental test using Tmote Sky nodes, a popular commercial hardware platform for wireless sensor systems. The results emphasize the interest of the proposed algorithms.

Load-Balancing Strategies for Lifetime Maximizing in Wireless Sensor Networks

The lifetime of Wireless Sensor Networks (WSN) is crucial. The goal of all WSN application scenarios is to have sensor nodes deployed, unattended, for months or years. In this work, we investigate the problem of energy consumption and lifetime maximizing in a many-to-one sensor network. In such network pattern, all sensor nodes generate and send data to a single sink via multihop transmissions. In our previous experimental studies, we noticed that, since all the sensor data has to be forwarded to a base station via multihop routing, the traffic pattern is highly nonuniform, putting a high burden on the sensor nodes close to the base station. In this paper, we analyze and propose some strategies that balance the energy consumption of these nodes and ensure maximum network lifetime by balancing the load as equally as possible.

Proportion based protocols for load balancing and lifetime maximization in wireless sensor networks

This paper presents the problem of minimizing energy consumption and maximizing lifetime in a many-to-one sensor network. In such network pattern, all sensor nodes generate and send data to a single and fixed base station (BS), via multi-hop transmissions. When all the sensor data have to be forwarded to a single BS via multi-hop routing, the traffic pattern is highly non-uniform, putting a high burden on the sensor nodes close to the BS. Some strategies that balance the energy consumption of the nodes and ensure maximum network lifetime by balancing the load are proposed and analyzed. The key element of the research is the use of multiple transmission power levels. We studied an optimal solution for calculating the hop-by-hop traffic proportions for the particular case of nodes having just two transmission power levels, and compared the results given by the heuristics with those from the optimal analytical case. Another goal is to propose and implement a systematic approach for the construction of the sensor network based on real sensor nodes. The neighbor discovery phase, the way in which the BS finds out the network topology and than impose the strategy and decide whether the nodes to act locally or respect the instruction from the sink are part of the protocol that is described in the paper.

Using Energy-Efficient Wireless Sensor Network for Cold Chain Monitoring

Temperature control is a major concern in cold chain monitoring and traceability services for the largest cause of food poisoning. Considerable work has examined the use of wireless solutions in warehouses. However, the maintaining of the chain during the transportation phase remains very crucial. In this paper, we present new wireless sensor network (WSN) solution for cold chain monitoring. This solution is based on self-organizing protocols and aims at saving energy in order to increase the sensor lifetime and as a result the global network longevity within the given context. Furthermore, this solution does not need any base station or central equipment. To save energy, periodical active/sleep schedule is adopted in the design of our protocols which were dimensioned and validated by an analytical model described in this paper.

Boundary node failure detection in wireless sensor networks

Wireless Sensor Networks (WSNs) are an important tool for monitoring strategic and dangerous sites where high security is required. Failure detection for sensor nodes in this specified application is a major concern. The failure of any system may cause losses such as economical, equipment damage and even risks for human lives. Moreover, failures are unavoidable in WSNs due to hardware constraints, hostile environment, unattended deployment and limited resources. This paper proposes a fully distributed approach, called Boundary Node Failure Detection (BNFD), for an efficient boundary control based on the determination of the WSN boundary. This one is determined using an algorithm which has the property to determine in each iteration the one-hop neighbor of the current boundary sensor. Hence, each boundary sensor knows its direct next boundary neighbor and can communicate with it in order to periodically test its presence. When a situation of failure is detected, a network restructuring will be launched to find a new boundary and an alarm will be triggered. The proposed approach has been implemented and simulated with the Castalia simulator. The simulation results show that the proposed method is energy efficient.

Fairness-aware UAV-assisted data collection in mobile wireless sensor networks

In this paper, we study data collection in mobile wireless sensor networks (WSNs) assisted by unmanned aerial vehicle (UAV). We focus on randomly deployed mobile sensors along a predefined path with different but constant velocities, and a flying UAV in different heights to collect data from the mobile sensors. As the network topology is changing under the mobility of the UAV and the sensor nodes, the design of efficient data collection protocols is a major concern. In this paper, we propose four data collection algorithms taking into account the multi-data-rate transmissions (DR) and the contact duration time (CDT) between the sensors and the UAV. Besides, we propose a fairness metric to evaluate the algorithms. Through extensive simulations, we examine the effectiveness of the proposed algorithms under different configurations and show how the algorithm combining DR and CDT outperforms the others in terms of number of collected packets and weighted fairness.

Energy optimization based on the redundancy in WSNs

Almost all WSNs (Wireless Sensor Networks) are deployed with some redundancy degree and redundancy is used only for robustness objectives. If not handled in an intelligent way, redundancy results in energy wasting because of (often unnecessary) redundant transmission and reception operations. We propose to take benefit from measurement redundancy to optimize the energy consumption and improve the end-to-end delay. We propose MR-LEACH (Measurement Redundancy aware LEACH) protocol, which is an extension to the well-known LEACH protocol to improve energy consumption in cluster-based WSNs. In addition to cluster formation according to LEACH protocol redundant nodes are grouped taking into account their redundancy and only a single node transmits data in each redundant group. This technique significantly improves the energy consumption and ensures a better end-to-end delay. Through intensive simulations, we discuss the performance of our approach and show how it outperforms the original LEACH protocol in terms of network lifetime and end-to-end delay.

Mobility-aware protocol for Wireless Sensor Networks in Health-care monitoring

Health-care monitoring with Wireless Sensor Networks (WSN) has become a major interest during the last few years. The use of efficient communication protocols is crucial in minimizing transmission delay and energy consumption of sensor nodes. In a heterogeneous WSN context, we propose, efficient mobility aware mechanisms which may be implemented in large three-tier WSN. These mechanisms must be designed to be optimal. The aim of this paper addresses common sensor behavior such as data exchange meanwhile responding to the mobility issue in the fore mentioned context. The mechanisms are based on two main protocols: topology creation and data collection in intra- and inter-tiers. Our mechanisms minimize collisions and optimize the duty-cycle of each node. Furthermore, a performance evaluation study detailed by an analytical model is presented in order to validate the designed protocols.

Performance evaluation of IEEE 802.15.4 PHY with impulsive network interference in cupcarbon simulator

IEEE 802.15.4 protocol is very much associated with ZigBee protocol and targets low data rate, low power consumption and low cost wireless networking that fits the requirements of wireless sensor networks (WSNs). Due to increase in radio frequency (RF) based communication devices and spectrum sharing between these devices makes it impossible to neglect the affect of interference on wireless communications. This paper provides brief description about technical features of IEEE standard 802.15.4 and ZigBee based physical layer structure and wireless channel impulsive interference modeling for wireless sensor networks in smart cities applications. For more accurate estimation of wireless channel characteristics, we have modeled it using alpha-stable distribution function. We have then estimated two out of four parameters of alpha-stable distribution depending on spatial density of wireless devices in specified area around the wireless node in a network. This allows better modeling and estimation of wireless channel conditions. We have analyzed IEEE standard 802.15.4 based communication system performance in terms of the bit error rate (BER). We have varied the total number of active nodes in specified area around sensor node and evaluates its affect on overall BER performance. We have also integrated this PHY layer based on IEEE standard 802.15.4 in the CupCarbon simulator with the consideration of impulsive network interference and its modeling using alpha-stable distribution.