Research Reports

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    On optimal anchor placement for effecient area-based localization in wireless networks
    (CERIST, 2015-06-08) Lasla, Noureddine; Younis, Mohamed; Ouadjaout, Abdelraouf; Badache, Nadjib
    Area-based localization is a simple and efficient approach, where each node estimates its position based on proxim- ity information to some special nodes with known location, called anchors. Based on the anchors’ coordinates, each node first determines its residence area and then approximates its position as the centroid of that area. Therefore, the accu- racy of the estimated position depends on the size of the residence area; the smaller the residence area is, the bet- ter the accuracy is likely to be. Because the size of the residence area mainly depends on the number and the posi- tions of anchor nodes, their deployment should be carefully considered in order to achieve a better accuracy while mini- mizing the cost. For this purpose, in this paper we conduct a theoretical study on anchor placement for a very popular area based localization approach. We determine the optimal anchor placement pattern for increased accuracy and how to achieve a particular accuracy goal with the least anchor count. Our analytical results are further validated through simulation.
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    Intertwined Medium Access Scheduling of Upstream and Downstream Traffic in Wireless Sensor Networks
    (CERIST, 2013-12-25) Bagaa, Miloud; Younis, Mohamed; Djenouri, Djamel; Badache, Nadjib
    In wireless sensor networks, the sensor data are often aggregated en-route to the base-station in order to eliminate redundancy and conserve the network resources. The base-station not only acts as a destination for the upstream data traffic, but it also configures the network by transmit- ting commands downstream to nodes. The data delivery latency is a critical performance metric in time-sensitive applications and is considered by a number of data aggregation schemes in the literature. However, to the best of our knowledge, no solution has considered the scheduling of downstream packets, originated from the base-station, in conjunction with upstream traffic. This paper fills such a gap and proposes MASAUD, which intertwines the medium access schedule of upstream and downstream traffic in order to reuse time slots in a non-conflicting manner and reduce delay. MASAUD can be integrated with any scheme for data aggregation scheduling. The simulation confirms the effectiveness of MASAUD.
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    Efficient Multi-Path Data Aggregation Scheduling in Wireless Sensor Networks
    (CERIST, 2013) Bagaa, Miloud; Badache, Nadjib; Ouadjaout, Abdelraouf; Younis, Mohamed
    In wireless sensor networks, in-network data aggregation filters out redundant sensor readings in order to reduce the energy and bandwidth consumed in disseminating the data to the base-station. In this paper, we investigate the problem of reliable collection of aggregated data with minimal latency. The aim is to form an aggregation tree such that there are k disjoint paths from each node to the basestation and find a collision-free schedule for node transmissions so that the aggregated data reaches the base-station in minimal time. We propose a novel algorithm for Reliable and Timely dissemination of Aggregated Data (RTAD). RTAD intertwines the formation of the aggregation tree and the allocation of time slots to nodes, and assigns parents to the individual nodes in order to maximize time slot reuse. The simulation results show that RTAD outperforms competing algorithms in the literature.