Faculty Publications
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Item Construction of minimum power 3-connected subgraph with k backbone nodes in wireless sensor networks(Springer International Publishing, 2019) Shetty D, D.; Lakshmi, M.Minimizing the total power in a wireless sensor network (WSN) has great significance, since the nodes are powered by a small battery of limited capacity. By using an appropriate topology, the energy utilization of the network can be minimized which results in an increased lifetime of a WSN. In reality, WSN is modeled as an undirected graph in which each vertex represents a sensor node and an edge represents the link between the two sensor nodes. We define a distance function that maps a pair of vertices to a positive real number, i.e., Euclidean distance between the two vertices. On this initial topology, we construct a reduced topology satisfying special connectivity constraints like bi-connectivity, k-connectivity, bounded diameter, degree restricted, etc. We assign power to each node as the maximum distance of all its adjacent edges, and total power of the network is the sum of the powers of all the vertices. Fault tolerance addresses the issue of a node or link failure in a WSN. Fault-tolerant network aims at k-connectivity in the network so that there exist at least k vertex disjoint paths between any two sensor nodes of the network. Minimum power 2-connected subgraph (MP2CS) problem is to contrive a 2-connected network with minimum total power. It is proved that MP2CS problem is NP-hard. Minimum power k backbone node 2-connected subgraph (MPkB2CS) problem is a special case of MP2CS problem, which seeks a power assignment satisfying 2-connectivity with k backbone nodes. In this paper, the problem of finding a 3-connected network for a given set of nodes, which minimizes the total power with k backbone nodes, is addressed which is termed as MPkB3CS problem. We propose an algorithm for MPkB3CS problem and establish that the proposed algorithm has an approximation ratio of 4k + 1, for k ≥ 3. © Springer Nature Switzerland AG 2019.Item Improved Algorithm for Minimum Power 2-Connected Subgraph Problem in Wireless Sensor Networks(Institute of Electrical and Electronics Engineers Inc., 2018) Lakshmi, M.; Shetty D, D.A Wireless Sensor Network (WSN) consists of small sensor nodes which communicate with each other using wireless radio channel and are used to monitor certain environmental parameters. Since the nodes are powered by a small battery of limited capacity, it is important to minimize the energy consumption in a WSN. By using an appropriate topology the energy utilization of the network can be minimized which results in an increased lifetime of a WSN. In practice, the transmission power of a sensor node can be tuned to obtain a required topology that satisfies certain connectivity constraints and this problem is known as Range Assignment Problem. For a given network, a reduced topology is constructed satisfying some connectivity constraints like k-connectivity, bounded diameter etc. Fault tolerance addresses the issue of node or link failure which aims at k-connectivity so that, the network has at least k vertex disjoint paths between any two nodes of the network. With the motivation of achieving fault tolerant network with minimum transmission energy, we consider Minimum power 2-connected subgraph (MP2CS) problem which is proved to be NP-hard. A polynomial time heuristic is proposed in this paper for the MP2CS problem and simulation is performed to compare with the existing algorithm. © 2018 IEEE.Item Approximation algorithm for receiver interference problem in dual power Wireless Sensor Networks(Springer Verlag service@springer.de, 2019) Shetty D, D.; Lakshmi, M.P.The problem of assigning power levels to the nodes of a wireless sensor network from a given a set of two power levels is called Dual power management problem and the underlying network is called Dual power network. We consider the problem of minimizing the maximum receiver interference of such a network. The interference disrupts the communication and forces the data packets to be retransmitted. The motivation is to conserve the energy by minimizing the interference and maintaining the connectivity of the dual power network. Receiver interference problem is proved to be NP-hard. In this paper, an approximation algorithm is derived for minimizing the maximum receiver interference of a dual power network by utilizing the approximation algorithm for Dual Power Management Problem. The proposed algorithm is supported by the simulation results. We term this problem as Dual Power Receiver Interference Problem and show that it is NP-complete using a polynomial time reduction from Degree Constrained Minimum Spanning Tree problem. We also prove the NP-completeness of Dual Power Management Problem by a polynomial reduction from Vertex Cover Problem. © 2019, Korean Society for Computational and Applied Mathematics.Item Optimal algorithm for minimizing interference with two power levels in wireless sensor networks(Engineering and Technology Publishing, 2019) Lakshmi, M.P.; Shetty D, D.Interference is a major hindrance to the communication in wireless sensor networks which needs to be optimized in order to minimize the total power consumption of the network. A sensor node in a WSN is assigned certain transmission range for sensing and transmission of data. If the transmission between any two nodes is affected by a third node, then it leads to interference. Sender interference of a node in WSN is the number of nodes that lie within the transmission range of that vertex. The receiver interference of a node x is the number of other nodes which include x in their transmission range. In recent days WSNs are operated by a discrete set of power levels in which a limited number of power levels are available which can be assigned to a node. The problem of minimizing the maximum sender interference of a WSN using only two power levels is studied in this paper. An optimal algorithm is presented in this paper which assigns transmission power to the sensor nodes of a given network such that the maximum sender interference is minimized and it results in a connected topology. An algorithm for receiver interference is also proposed using a similar concept, and an extensive simulation is performed to compare the maximum sender and receiver interference for the same instances. © 2019 Journal of Communications.