Fabrice Valois

Optimized Data Aggregation in WSNs Using Adaptive ARMA

Wireless sensor networks (WSNs) are data centric networks to which data aggregation is a central mechanism. Nodes in such networks are known to be of low complexity and highly constrained in energy. This requires novel distributed algorithms to data aggregation, where accuracy, complexity and energy need to be optimized in the aggregation of the raw data as well as the communication process of the aggregated data. To this end, we propose in this work a distributed data aggregation scheme based on an adaptive Auto-Regression Moving Average (ARMA) model estimation using a moving window technique and running over suitable communications protocols. In our approach, we balance the complexity of the algorithm and the accuracy of the model so as to facilitate the implementation. Subsequent analysis shows that an aggregation efficiency of up to 60% can be achieved with a very fine accuracy of 0.03 degree. And simulation results confirm that this distributed algorithm provides significant energy savings (over 80%) for mass data collection applications.

Performance Analysis of an Efficient MAC Protocol With Multiple-Step Distributed In-Band Channel Reservation

It is well known that the performance of most of contention-based medium-access-control (MAC) protocols are significantly influenced by packet collisions. In this paper, we propose an efficient MAC protocol for wireless local area networks (LANs) to handle packet collisions. Different from traditional reservation-based MAC protocols, where only one-step channel reservation is considered, we propose a multiple-step distributed in-band channel-reservation mechanism, which is called m-DIBCR, where m represents the number of steps considered in the channel reservation. In m-DIBCR, each node maintains m timers, each of which serves as the backoff timer for one of the next m packets to be sent. A node broadcasts the values of these timers by piggybacking them in data packets, and simultaneous transmissions can be avoided when its neighboring nodes overhear these values. Another contribution of this paper is that important performance measurements such as packet collision probabilities and average packet transmission delays are obtained based on in-depth analyses. Moreover, practical implementation methods such as an efficient ¿virtual packet collision¿ resolution scheme and a simple ¿packet delay variation¿ control scheme, are proposed. Results obtained from both performance analyses and simulations show that, compared with one-step channel reservation, the system throughput is significantly improved by multiple-step channel reservation, particularly in networks with high transmission error probabilities and/or a large number of contending nodes.

A New Metric to Quantify Resiliency in Networking

In network protocol engineering resiliency is still a relatively new and somewhat ill-defined concept. Insofar only few studies attempt to define some metric to measure and thus quantify resiliency. In this paper we propose to quantify network resiliency along multiple parameters and further we introduce a two dimensional graphical representation with multiple axes forming an equiangular polygon surface. This method allows to aggregate meaningfully several parameters and makes it easier to visually discern various tradeoffs thus greatly simplifying the process of protocol comparison. Finally, this method is flexible and can be applied to various networking contexts.

Efficient Route Redundancy in DAG-Based Wireless Sensor Networks

Wireless Sensor Networks (WSN) need to be organized in order to be more resource-efficient and scalable. Directed Acyclic Graphs (DAG) are of interest for WSN organization because of their route redundancy to the root. A recent routing protocol for WSNs coming from the IETF ROLL Working Group specifies the use of DAGs and proposes to improve the route redundancy even further by routing through sibling nodes as well. In this paper, we investigate the effectiveness of routing through sibling nodes and we propose a new use of siblings which preserves most of the performance but reduces algorithmic complexity and memory requirements.

Channel holding time characterization in real GSM network

This paper presents a realistic characterization of the channel holding time in an operating GSM network covering an urban area. Our approach is entirely statistical: the data set to be fitted has been provided by the OMC (operations and maintenance center). The Kolmogorov Smirnov goodness of fit test is used in order to test the suitability of the exhibited distribution. From this statistical analysis, it can be concluded that the negative exponential distribution is a good approximation for describing the channel holding time.