Hyunsook Kim

A power efficient routing protocol based on balanced tree in wireless sensor networks

A wireless sensor network consisting of a large number of nodes with limited battery power should minimize energy consumption at each node to prolong the network lifetime. In this paper, we propose a routing protocol based on a balanced tree, called BATR (balanced aggregation tree routing), which uses near optimal minimal spanning tree for balancing the power consumptions over all nodes. Our key idea is that a near optimal data aggregation can be achieved in terms of network lifetime when power consumption at each node can be nicety balanced. Simulation results show that the BATR can lengthen system lifetime as compared with the conventional data aggregation protocols.

An energy efficient tracking method in wireless sensor networks

Since it is difficult to replace batteries of the sensor nodes that are once deployed in the field, energy saving is one of the most critical issues for object tracking in wireless sensor networks. It is desirable that only the nodes surrounding the mobile target should be responsible for observing the target to save the energy consumption and extend the network lifetime as well by reducing the number of participating nodes. The number of nodes participating in object tracking can be reduced by an accurate estimation of the target location. In this paper, we propose a tracking method that can reduce the number of participating sensor nodes for target tracking. We show that our tracking method performs well in terms of energy saving regardless of mobility pattern of the mobile target.

Atlas of Vega: 3850―6860 Å

We present a high resolving power (λ/Δλ = 90,000) and high signal-to-noise ratio (~700) spectral atlas of Vega covering the 3850–6860 A wavelength range. The atlas is a result of averaging of spectra recorded with the aid of the echelle spectrograph BOES fed by the 1.8 m telescope at Bohyunsan Observatory (Korea). The atlas is provided only in machine-readable form (electronic data file) and will be available in the SIMBAD database upon publication.

A target tracking method to reduce the energy consumption in wireless sensor networks

Reducing the energy consumption is one of the most critical issues in wireless sensor networks and an accurate prediction is especially required in tracking. It is desirable that only the nodes surrounding the mobile target should be responsible for observing the target to save the energy consumption and extend the network lifetime as well. In this paper, we propose an efficient tracking method based on prediction through the error correction, which can minimize the number of participating sensor nodes for target tracking. We show that our tracking method performs well in terms of saving energy regardless of mobility pattern of the mobile target.

A zone-based clustering method for ubiquitous robots based on wireless sensor networks

In this paper, we propose a topology configuration method for wireless sensor networks with an objective of well balancing energy consumption over all sensor nodes without generating any isolated sensor nodes. Our scheme has some attractive features: First, a high density node having good many neighbor nodes can be selected as a clusterhead in a zone. Second, reconfiguration of cluster can be carried out in a single zone, not all over network field, to reduce the number of nodes that participate in changing clusterheads. Third, multiple-hop transmissions between nodes or between clusterheads are possible. Finally, the proposed method can be applicable to various ubiquitous computing services including the ubiquitous robot (UR) based on wireless sensor networks. Simulation results show that our method outperforms LEACH and PEGASIS in terms of the system lifetime.

An energy efficient method for tracking mobile ubiquitous robots using wireless sensor network

In general, it requires lots of complicated and expensive processing functions to find the exact location of a mobile target. For example, Ubiquitous Robotic Companion (URC) system should be equipped with powerful resources or be given an aid from the external servers to find its location for itself. Sensor network that consists of inexpensive low-power sensors can provide an efficient solution to find the exact location of such a mobile target at a low price. In such applications, if all sensor nodes have to always wake up to find location of the mobile robot, we have to pay a lot of waste of resources such as battery power and channel utilization. In this paper, we propose a cheap and energy efficient location tracking method of a mobile robot by minimizing the number of sensor nodes participating in the task of target tracking.

A power efficient routing protocol in wireless sensor networks

Saving energy consumption for a long network lifetime is one of the most important issues in design of wireless sensor networks because they usually consist of a large number of nodes with limited battery power. In this paper, we propose a balanced tree construction scheme called BATR (Balanced Aggregation Tree Routing), which uses near optimal minimal spanning tree for balancing the power consumptions over all nodes. Our main idea is that if energy consumed for transmission and reception can be nicely balanced over all nodes, an optimal data aggregation can be achieved in terms of network lifetime. Simulation results assure that the BATR can lengthen system lifetime as compared with the conventional data aggregation protocols.

Two types of a zone-based clustering method for wireless sensor networks

In this paper, we propose a zone-based clustering method to balance the amount of energy consumptions over all sensor nodes in the wireless sensor network field. In our method, a network field is divided into several zones with two types of shape: arc and square. And, the number of clusterheads selected in each zone is determined depending on its area. These contribute to distributing clusterheads evenly over the network field. Simulation results show that our zone method can outperform LEACH and PEGASIS in terms of network lifetime and connectivity.

An Adaptive Polling Scheme for IEEE 802.11 Wireless LAN

The point coordination function of IEEE 802.11 is defined to support time bounded traffic in wireless LANs. However, current WLAN standard does not consider the traffic characteristics such as time bound traffic, null poll, and priority. In the case of time bounded traffic, PCF must evolve to support degrees of priority. In this paper, we proposed an adaptive polling scheme to increase the performance of wireless LANs. Moreover, we focused to a polling schedule to serve voice traffic. The simulation results show that the proposed scheme is more efficient than using only standards.