• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.517-520
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• 2005

Wireless sensor network combines sensing and computing technology which can sense light, temperature, vibration, magnetic field and wind etc, as each purpose of using those. Wireless nodes operate signal processing skill which has proceeded sensed information from the sensor, transmission which makes information reached to observer and limited energy managing skill which is needed on account of using battery to operate wireless. To make responsible measuring and sensing out of them, efficient energy management is so important to maintain life time of network. In this paper, after explaining CSMA/CA(Carrier Sense Multiple Access/Collision Avoidance) traditional wireless MAC protocol, and ER-MAC(Energy Rate Medium Access Control) which are not managing resource of hardware but MAN(Medium Access Control), data-link layer out of OSI 7 layer. We would like to analyze those efficiency of power saving comparing with each protocol.

• The KIPS Transactions:PartC
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• v.16C no.2
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• pp.209-216
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• 2009

In the wireless sensor network, flooding is required for the dissemination of queries and event announcements. The simple flooding causes the implosion and the overlap problems, so the simple flooding may result in the reduced network lifetime. Therefore, in this paper, we propose the flooding overlay structure (FOS) so that the overhead caused by flooding can be reduced. We propose two variants of FOS mechanisms, the centralized FOS (CFOS) and the distributed FOS (DFOS). In CFOS, the sink collects the network topology information and selects forwarding nodes based on that information. On the other hand, DFOS allows each sensor node to decide whether to act as a forwarding node or not based on its local information. For the performance evaluation of our proposed mechanisms, we carry out NS-2 based simulations and compare ours with the simple flooding and the gossiping. The simulation results indicate that the proposed FOS mechanisms outperform the simple flooding in terms of the network lifetime and the gossiping in terms of the data delivery ratio.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.11
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• pp.2107-2112
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• 2006

As growing up of elderly population, the interesting on healthcare system in normal life using W is increasing. An integrated u-healthcare service architecture with IEEE 802.11 and IEEE 802.15.4 based sensor network and code divisi(m multiple access(CDMA) public mobile telecommunication networks was designed and developed. Sensor nodes with electrocardiogram(ECG), body core temperature sensors are attached on the patients' body. The healthcare parameters are transferred to web server via CDMA mobile network or through existed LAN network. The existed LAN network is suggested to be used for continuous monitoring of patient's health status in hospital while mobile networks can be used for general purpose at home or outdoor where infra networks unavailable. This system enable healthcare personal to be able to continuously access, review, monitor and transmit the patients information whereever they are, whenever they want. And immediately check their status by using cellular phone and obtain detail information by communication with medical information server through CDMA. By using this developed integrated u-healthcare service architecture, we can monitor patients' health status for 24 hours.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.6
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• pp.1055-1059
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• 2006

In Wireless Sensor Networks(WSNs), a sensor node broadcasts the acquisited sensing data to neighboring other nodes and it makes serious data duplication problem that increases network traffic loads and data loss. This problem is concerned with the conflict condition for supporting both the reliability of data transfer and avoidance of network congestion. To solve the problem, a reliable congestion control protocol is necessary that considers critical factors affecting on data transfer reliability such as reliable data transmission, wireless loss, and congestion loss for supporting effective congestion control in WSNs. In his paper, we proposes a reliable congestion protocol, called HRCCP, based on hop-hop sequence number, and DSbACK by minimizing useless data transfers as an energy-saved congestion control method.

• Journal of Internet Computing and Services
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• v.14 no.2
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• pp.53-59
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• 2013

Harvesting energy from the environment is essential for many applications to slow down the deterioration of energy in sensor networks. Energy from the environment is an inexhaustible supply which, if properly managed and harvested from the sources, can allow the system to last for a longer period. Many simulators simulate whole sensor networks where the nodes rely on energy harvesting for their source of power. It is important to be able to assume and simulate a node that can harvest energy from different sources of ambient energy. It is also essential to be able to keep track of the energy levels of the node and adjust node activities based on its energy status. This study aims to develop a prototype for a single node simulator that will show the effects of harvesting from different sources of energy. The results of this study can later be extended for more complicated simulations.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.4
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• pp.289-293
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• 2009

In sensor networks, many methods have been proposed to process in-network aggregation effectively. Contrary to normal aggregation queries, skyline query processing that compare multi-dimension data for producing result is very hard. It is important to filter unnecessary data for energy-efficient skyline query processing. Existing approach like MFTAC restricts unnecessary data transitions by deploying filters to whole sensors. However, network lifetime is reduced by energy consumption for filters transmission. In this paper, we propose a lazy filtering-based skyline query processing algorithm of in-network for reducing energy consumption by filters transmission. The proposed algorithm creates the skyline filter table (SFT) in the data gathering process which sends from sensor nodes to the base station and filters out unnecessary transmissions using it. The experimental results show that the proposed algorithm reduces false positive by 53% and improves network lifetime by 44% on average over MFTAC.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.8
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• pp.591-595
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• 2009

Most existing routing protocols for object detection and tracking in wireless sensor networks concentrate on finding ways to detect and track one and more individual objects, e.g. people, animals, and vehicles, but they do not be interested in detecting and tracking of continuous objects, e.g., poison gas and biochemical. Such continuous objects have quite different properties from the individual objects since the continuous objects are continuously distributed across a region and usually occupy a large area, Thus, the continuous objects could be detected by a number of sensor nodes so that sensing data are redundant and highly correlated. Therefore, an efficient data collection and report scheme for collecting and locally aggregating sensing data is needed, In this paper, we propose the Continuous Object Tracking Mechanism based on Dynamic Rectangle Zone for detecting, tracking, and monitoring the continuous objects taking into account their properties.

• Journal of Korea Multimedia Society
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• v.11 no.4
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• pp.544-553
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• 2008

The general sensor network uses bundle method to collect fixed information from sensor node. However, this method is difficult to actively cope with major sensing objects in healthcare environment including status and position change of person and change of surrounding environment. In order to support the healthcare environment, certain information should be provided in accordance with the change of status of person and surrounding circumstance and also must cope with the change of network type by movement of person. This paper analyzes LEACH protocol which guarantees effectiveness of network as it constitutes clusters between Agilla model that is a representative multi agent middle ware and surrounding nodes. Based on the result of this analysis, it suggests LEACH_Mobile protocol which guarantees node mobility that is the weakest point of LEACH protocol. Moreover, it designs mobility agent middleware which supports dynamic function change of node and mobility agent module which supports dynamic function change of mobile node as components of LEACH_Mobile routing module. In addition, it is definitely increase performance which in mobile node of transfer data rate through LEACH_Mobile protocol of simulation result.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.4
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• pp.118-129
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• 2008

This paper describes an IEEE 802.15.4-based hierarchical sensor network model for a VAWS(Vehicle Approach Warning System) which provides the drivers of vehicles approaching a sharp turn with the information about vehicles approaching the same turn from the opposite end. In the proposed network model, a tree-structured topology, that can prolong the lifetime of network is formed in a self-organizing manner by a topology control protocol. A simple but efficient routing protocol, that creates and maintains routing tables based on the network topology organized by the topology control protocol, transports data packets generated from the sensor nodes to the base station which then forwards it to a display processor. These protocols are designed as a network layer extension to the IEEE 802.15.4 MAC. In the simulation, which models a scenario with a sharp turn, it is shown that the proposed network model achieves a high-level performance in terms of both energy efficiency and throughput simultaneously.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.2
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• pp.133-140
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• 2016

In active sonar field, a target detection and localization based on a distributed sensor network has been much studied for the underwater surveillance of the coast. Zhou et al. proposed a target localization method utilizing the positions of target-detected sensors in distributed sensor network which consists of detection-only sensors. In contrast with a conventional method, Zhou's method dose not require to estimate the propagation model parameters of detection signal. Also it needs the lower computational complexity, and to transmit less data between network nodes. However, it has large target localization error. So it has been modified for reducing localization error by Ryu. Modified Zhou's method has better estimation performance than Zhou's method, but still relatively large estimation error. In this paper, a target localization method based on modified Zhou's method is proposed for reducing the localization error. The proposed method utilizes the geometry of the positions of target-detected sensors and a line that represents the bearing of target, a line can be found by modified Zhou's method. This paper shows that the proposed method has better target position estimation performance than Zhou's and modified Zhou's method by computer simulations.