• Journal of Advanced Marine Engineering and Technology
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• v.39 no.2
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• pp.187-194
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• 2015

Accurate relative location estimation is a key requirement in indoor localization systems based on wireless sensor networks (WSNs). However, although these systems have applied not only various optimization algorithms but also fusion with sensors to achieve high accuracy in position determination, they are difficult to provide accurate relative azimuth and locations to users because of cumulative errors in inertial sensors with time and the influence of external magnetic fields. This paper based on ultra-wideband positioning system, which is relatively suitable for indoor localization compared to other wireless communications, presents an indoor localization system for estimating relative azimuth and location of location-unaware nodes, referred to as target nodes without applying any algorithms with complex variable and constraints to achieve high accuracy. In the proposed method, the target nodes comprising three mobile nodes estimate the relative distance and azimuth from two reference nodes that can be installed by users. In addition, in the process of estimating the relative localization information acquired from the reference nodes, positioning errors are minimized through a novel modified rounding estimation technique in which Kalman filter is applied without any time consumption algorithms. Experimental results show the feasibility and validity of the proposed system.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.12
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• pp.1353-1358
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• 2014

Tremendous amount of dummy packets are generally generated for faking over a wireless sensor network so as to keep the location privacy of nodes on the communication paths against the global eavesdropping. In this paper, a scoped-flooding protocol is designed for transferring data between each source and mobile sink(aka, basestation) where, the only nodes within the scope are allowed to issue dummy packets at every idle time so that the location privacy of the nodes on the paths is kept and the amount of dummy packets is reduced to the extend of the flooding scope. The size of the flooding diameter can be taken into consideration of the privacy level and the communication cost. We design a detailed specification of the protocol and verify several properties.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2243-2250
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• 2014

In wireless sensor networks(WSNs), geographical routing algorithms can enhance the network capacity. However, in real WSNs, it is difficult for each node to know its physical location accurately. Especially, indoor environments contain various obstacles such as concrete wall, furniture which cause non-line-of-sight(NLOS) conditions. To solve the problem, we propose location error compensation algorithm by using two difference topology constructions. First topology is based on mobile node's location which is obtained from anchor nodes. Second topology is based on mutual distance from neighbor nodes. The proposed algorithm efficiently detects and corrects the location errors and significantly enhances the network performance of geographic routing in the presence of location errors.

• Journal of the Institute of Convergence Signal Processing
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• v.15 no.1
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• pp.15-22
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• 2014

This paper presents the implementation of a control system of pellet boiler using wood pellet as carbon neutral material. The system also has the additional features to provide remote controlling and monitoring based on home networking technology through either public switched telephone networks or mobile communication networks. It consists of three kinds of sub-modules; a main controller provides basic and additional features such as a setting of temperature, a supplying of wood pellet, a controlling of ignition and fire-power, and a removing of soot. The second is temperature controller of individual rooms which is connected to the main controller through RS-485 links. And interface modules with PSTN and mobile networks can support remote controlling and monitoring the functions. The test results under the heating area of $172m^2$ show a thermal efficiency of 93.6%, a heating power of 20,640kcal/hr, and a fuel consumption of 5.54kg/hr. These results are superior to those of the conventional pellet boilers. In order to obtain the such high performance, we newly applied a 3-step ignition flow, a flame detection by $C_dS$ sensor, and a fire-power control by fine controlling of shutter to our pellet boiler.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.557-560
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• 2013

MANTET(Mobile Ad-Hoc Networks), which is configured and operated by each terminals with no support of communication infra-structures, is recently expanded its application fields from terrestrial communications to underwater environments with technical advances of Wi/Fi and minimized portable terminals. Underwater sensor network, undersea environment explorations and probes, information transmission for underwater area, etc., is typical application fields of underwater MANET. Especially, Performance measurement and analysis on this application fields is one of important research area and base of design, implementation and operation for underwater MANET. However, the research results are focued on various transmission parameters on network level, and its objects of analysis are also performance of network level. In this paper, transmission performances for application levels are measured and analyzed for user levels on underwater MANET. In this study, voice traffic is assumed as object application traffic, computer simulation which is based on NS-2 having additional implemented functions for underwater communications is used. on some defined scale of MANET, transmission performances according to varying traffic environments are measured and analyzed, operation conditions on underwater MANET is suggested with the analysis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.10
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• pp.1469-1476
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• 2022

Recently, many researches have been conducted to estimate blood pressure using ECG(Electrocardiogram) and PPG(Photoplentysmography) signals. In this paper, we designed and implemented a mobile system to monitor blood pressure in real time by using 1-D convolutional neural networks. The proposed model consists of deep 11 layers which can learn to extract various features of ECG and PPG signals. The simulation results show that the more the number of convolutional kernels the learned neural network has, the more detailed characteristics of ECG and PPG signals resulted in better performance with reduced mean square error compared to linear regression model. With receiving measurement signals from wearable ECG and PPG sensor devices attached to the body, the developed system receives measurement data transmitted through Bluetooth communication from the devices, estimates systolic and diastolic blood pressure values using a learned model and displays its graph in real time.

• Journal of KIISE:Information Networking
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• v.35 no.1
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• pp.34-45
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• 2008

In dynamic wireless sensor networks where sources and sinks are moving or are created/died, control overheads for route establishment are increased and thus become one of the major factors for energy consumption. This study introduces prefetching and pruning for Directed Diffusion to remove redundant control messages. Prefetching collects path information for each event with "AnyEvent" in advance and gives quick responses without further flooding of requests. Pruning accumulates history information from previous requests and replies, and then stops forwarding a request towards where the event does not exist. Simulation results with ns show that it is possible to build implicit and soft infrastructures within a Directed Diffusion system through these active collection and passive accumulation and they improve energy consumption more as control overhead goes higher.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.117-121
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• 2008

In ad hoc network, the scarce energy management of the mobile devices has become a critical issue in order to extend the network lifetime. Therefore, the energy consumption is important in the routing design, otherwise cluster schemes are efficient in energy conserving. For the above reasons, an Energy conserving Context aware Clustering algorithm (ECC) is proposed to establish the network clustering structure, and a routing algorithm is introduced to choose the Optimal Energy Routing Protocol (OERP) path in this paper. Because in ad hoc network, the topology, nodes residual energy and energy consuming rate are dynamic changing. The network system should react continuously and rapidly to the changing conditions, and make corresponding action according different conditions. So we use the context aware computing to actualize the cluster head node, the routing path choosing. In this paper, we consider a novel routing protocol using the cluster schemes to find the optimal energy routing path based on a special topology structure of Resilient Ontology Multicasting Routing Protocol (RODMRP). The RODMRP is one of the hierarchical ad hoc network structure which combines the advantage of the tree based and the mesh based network. This scheme divides the nodes in different level found on the node energy condition, and the clustering is established based on the levels. This protocol considered the residual energy of the nodes and the total consuming energy ratio on the routing path to get the energy efficiently routing. The proposed networks scheme could get better improve the awareness for data to achieve and performance on their clustering establishment and messages transmission. Also, by using the context aware computing, according to the condition and the rules defined, the sensor nodes could adjust their behaviors correspondingly to improve the network routing.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.7
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• pp.93-102
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• 2017

Recently increasing usage of smartphones makes the Internet of Things (IoT) a leading technology that can collect and share data through sensor networks and wireless communication such as low-power Bluetooth (BLE). BLE-based application can provide operators more precise information on Automatic Door system by remotely diagnosing the system faults through wireless sensor networks and sensors around the Automatic Door. In this paper, a smart device with extended BLE module is implemented which can monitor and Control the system states and faults remotely without on-site diagnostic. while maintaining system integrity so that increase efficiency of time and costs for system management. We can use the results of this research as a basis in evaluating reliability of data between devices, extending communication module in Controller of obsolete Door systems, and establishing centralized monitoring systems in near future with multi-channel Door Controls.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.6
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• pp.640-651
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• 2016

We propose an effective ToA-based localization method considering accuracy in indoor environments. The purpose of the localization system is to estimate the coordinates of the geographic location of target device. In indoor environments, accurately estimating the location of a target device is not easy due to various errors. The accuracy of wireless localization is influenced by NLOS errors. ToA-based localization measures the location of a target device using the distances between a mobile device and three or more base stations. However, each of the NLOS errors along a distance estimated from a target device to a base station is different because of dissimilar obstacles. To accurately estimate the target's location, an optimized localization process is needed in indoor environments. In this paper, effective ToA-based localization method process is proposed for improving accuracy in wireless sensor networks. Performance evaluations are presented, and the experimental localization system results are proved through comparisons of various localization methods with the proposed methods.