Browsing by Author "Wang, Lusheng"

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    Optimal Relay Location for Resource-Limited Energy-Efficient Wireless Communication
    (2002-03-26) Cardei, Ionut; Cardei, Mihaela; Wang, Lusheng; Xu, Baogang; Du, Ding-Zhu
    In the design of wireless networks, techniques for improving energy efficiency and extending network lifetime have great importance, particularly for defense and civil/rescue applications where resupplying transmitters with new batteries is not feasible. In this paper we study a method for improving the lifetime of wireless networks by minimizing the length of the longest edge in the interconnecting tree with deploying additional relay nodes.Let P={p1, ..., pn} be a set of n terminals in the Euclideanplane. For a positive integer k, the bottleneck Steinertree problem (BSTP) asks to find a Steiner tree with atmost k Steiner points such that the length of the longest edge in the tree is minimized. We give a ratio - sqrt(3) + e polynomial time approximation algorithm for BSTP, where e is an arbitrary positive number.Keywords:wireless networks, power efficient, approximation algorithms, Steiner tree, bottleneck Steiner tree.
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    Relay Sensor Placement in Wireless Sensor Networks
    (2002-01-22) Cheng, Xiuzhen; Du, Ding-Zhu; Wang, Lusheng; Xu, Baogang
    In this paper, we propose a novel idea of maintaining connectivity by introducing relay sensors in a wireless sensor network. We restrict our consideration to a very important class of wireless sensor networks such as biomedical sensor networks, in which the locations of the sensors are fixed and the placement can be pre-determined. We formulate our problem to the NP-hard network optimization problem named Steiner Minimum Tree with Minimum number of Steiner Points (SMT-MSP) and present two approximate solutions. Meanwhile, we study the topology improvement in a wireless sensor network when relay sensors are introduced. In other words, we restrict transmission power of each sensor to a small value and use relay sensors to guarantee connectivity. The performance parameters under consideration are $P$, the total per node minimum power needed to maintain connectivity, and $D$, the maximum degree in the minimum power topology (maintained by $P$).Simulation study shows that with the introduction of relay sensors, we achieve better performance, especially for sparse topology.