Browsing by Author "Younis, Mohamed"
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Item Accurate Anchor-Free Node Localization in Wireless Sensor Networks(2006-02-10T16:51:23Z) Youssef, Adel; Younis, Mohamed; Agrawala, AshokThere has been a growing interest in the applications of wireless sensor networks in unattended environments. In such applications, sensor nodes are usually deployed randomly in an area of interest. Knowledge of accurate node location is essential in such network setups in order to correlate the reported data to the origin of the sensed phenomena. In addition, awareness of the nodes’ positions can enable employing efficient management strategies such as geographic routing and conducting important analysis such as node coverage properties. In this paper, we present an efficient anchor-free protocol for localization in wireless sensor networks. Each node discovers its neighbors that are within its transmission range and estimates their ranges. Our algorithm fuses local range measurements in order to form a network wide unified coordinate systems while minimizing the overhead incurred at the deployed sensors. Scalability is achieved through grouping sensors into clusters. Simulation results show that the proposed protocol achieves precise localization of sensors and maintains consistent error margins. In addition, we capture the effect of error accumulation of the node’s range estimates and network’s size and connectivity on the overall accuracy of the unified coordinate system.Item The Overlapped K-hop (OK) Clustering Algorithm(2006-02-09T17:16:41Z) Youssef, Adel; Youssef, Moustafa; Younis, Mohamed; Agrawala, A.Clustering is a standard approach for achieving efficient and scalable performance in wireless sensor networks. Clustering algorithms are mostly heuristic in nature and aim at generating the minimum number of disjoint clusters. In this report, we formulate the overlapping multi-hop clustering problem as an extension to the k-dominating set problem. Then we propose a fast, randomized, distributed multi-hop clustering algorithm (OK) for organizing the sensors in a wireless sensor network into overlapping clusters with the goal of minimizing the overall communication overhead, and processing complexity. OK assumes a quasi-stationary network where nodes are location-unaware and have equal significance. No synchronization is needed between nodes. OK is scalable; the clustering formation terminates in a constant time regardless of the network topology or size. The protocol incurs low overhead in terms of processing cycles and messages exchanged. We analyze the effect of different parameters (e.g. node density, network connectivity) on the performance of the clustering algorithm in terms of communication overhead, node coverage, and average cluster size. The results show that although we have overlapped clusters, the OK clustering algorithm still produces approximately equal-sized clusters.