• Journal of Institute of Control, Robotics and Systems
• /
• v.19 no.3
• /
• pp.268-274
• /
• 2013

In this paper, the performance analysis of optics-based sensor node localization using ToF (Time of Flight) scheme is conducted. Generally, the position of the sensor node is calculated on the base station. And the base station scans neighboring sensor nodes with a laser. The laser which is reflected from one sensor node, however, can be reached to the base station at different angles according to the scanning resolution. This means that the error of the reached angle can increase and one node may be recognized as different nodes. Also the power of laser can decrease because the laser signal spread. Thus the sensor node which is located at a long distance from the base station cannot be detected. In order to overcome these problems which can be occurred in localization using ToF, the beam spot, the scanning resolution, the size of reflector and the power of laser at the sensor node were analyzed. It can be expected that the consequence of analysis can be provided in acquisition of accurate position of sensor node and construction of optics-based sensor node localization system.

• Journal of Korea Multimedia Society
• /
• v.15 no.2
• /
• pp.242-249
• /
• 2012

Recently, value added location based service and convergence monitoring and control system is growing. The cases include increasing usage of smart-phone for taking picture, wireless network, GPS and digital map. Especially, Smart-phone is appropriate for using image information and location information. However it is possible to be exploited for forgery and manipulation. So we experimented on transferring modified data on the smart-phone as image and location information in EXIF and researched the technology for data verification. In addition, we have designed security monitoring and control prototype considering axis-address matching analysis used geocoding, watermarking verification, encryption.

• Convergence Security Journal
• /
• v.10 no.2
• /
• pp.27-35
• /
• 2010

We implemented an application system which is able to verify visitor identification for remote bundle control based on OSGi and web camera control using embedded linux system. This system are designed open Oscar framework by porting java on the embedded linux system and implemented web camera system in local area networks. Also This system can verify information of visitor from receiving the data of RFID reader and designed the wireless internet system in home. Basically, in this paper we expect that home network system development and the period of application service development are reduced with integrated service provision based on OSGi.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.708-713
• /
• 2004

This research develops a sensorless hydraulic servo system of Parallel-Typed robot for harbour construction. Purpose of the robot is to mechanize the construction, which is accomplished through a joystick's operating by a stoneworker (or diver). The robot is attached on the end of an excavator as its attachment or transported by a crane to reach the desired place. The embedded compact controller is installed on the robot body and controlled by wireless telecommunication. For underwater work, it is necessary to waterproof the robot and its sensors. Especially, a sensor waterproof is a main drawback for the underwater robot. This leads us to develop a hydraulic robot position controller using an observer which gives the position information without any position sensor. We design a neural network to identify the displacement change according to the command voltage to servo valve. To verify the sensorless controller, this paper presents the performance of the sensorless control for which the position is given by the observer comparing with that of the sensor control for which the position is measured by LVDT sensors.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.5 no.1
• /
• pp.74-80
• /
• 2010

We implemented an application system which is able to verify visitor identification for remote bundle control based on OSGi and web camera control using embedded linux system. This system are designed open Oscar framework by porting java on the embedded linux system and implemented web camera system in local area networks. Also This system can verify information of visitor from receiving the data of RFID reader and designed the wireless internet system in home. Basically, in this paper we expect that home network system development and the period of application service development are reduced with integrated service provision based on OSGi.

• Journal of Information Technology Applications and Management
• /
• v.24 no.4
• /
• pp.57-69
• /
• 2017

Due to the development of technology even in learning and education area, many studies have begun to make a new attempts to research by using SNS, breaking away from traditional learning methods. However, the limitations of these studies are restricted only to the use of wireless Internet and writing on Web sites. This study aims to conduct a research on English learning activities that utilize various technologies such as Bigdata, Facebook, Social Network Services (SNS) and English applications. In addition, this study looks into how these modern technologies can be integrated in the classrooms and which activities can be applied in the English classroom. This research is to suggest effective English learning methods through a thorough investigation on the effectivity of various technologies based on the Web 2.0 such as Flickr, blogs, MySpace, and online discussion board within the context of the English learning. To verify the effect of the study, the subjects are divided into experimental and control group. The experiment is proceeded with pre- and post-test. The experimental group is designed to verify the effects using SNS tools such as Facebook, Bigdata, and Online Massive Learning. A survey is conducted to determine the preference of utilizing social networking sites and to analyze the effects in class. The result is that the average scores for experimental group have improved more than the average of control group. The comparison of pre and post-test of the experimental group shows that the significance of the higher and median group was statistically significant at the p<0.01.

• Journal of information and communication convergence engineering
• /
• v.11 no.3
• /
• pp.153-166
• /
• 2013

A hierarchical time division multiple access (HTDMA) medium access control (MAC) protocol is proposed for clustered mobile underwater acoustic networks. HTDMA consists of two TDMA scheduling protocols (i.e., TDMA1 and TDMA2) in order to accommodate mobile underwater nodes (UNs). TDMA1 is executed among surface stations (e.g., buoys) using terrestrial wireless communication in order to share mobility information obtained from UNs which move cluster to cluster. TDMA2 is executed among UNs, which send data to their surface station as a cluster head in one cluster. By sharing mobility information, a surface station can instantaneously determine the number of time slots in a TDMA2 frame up to as many as the number of UNs which is currently residing in its cluster. This can enhance delay and channel utilization performance by avoiding the occurrence of idle time slots. We analytically investigate the delay of HTDMA, and compare it with that of wellknown contention-free and contention-based MAC protocols, which are TDMA and Slotted-ALOHA, respectively. It is shown that HTDMA remarkably decreases delay, compared with TDMA and Slotted-ALOHA.

• Journal of Communications and Networks
• /
• v.13 no.5
• /
• pp.421-427
• /
• 2011

Problems encountered in IEEE 802.11 medium access control (MAC) design are interferences from neighboring or hidden nodes and collision from simultaneous transmissions within the same contention floors. This paper presents the selective decoding schemes in MAC protocol for multiple input multiple output ad-hoc networks. It is able to mitigate interferences by using a developed minimum mean-squared error technique. This interference mitigation combined with the maximum likelihood decoding schemes for the Alamouti coding enables the receiver to decode and differentiate the desired data streams from co-channel data streams. As a result, it allows a pair of simultaneous transmissions to the same or different nodes which yields the network utilization increase. Moreover, the presented three decoding schemes and time line operations are optimally selected corresponding to the transmission demand of neighboring nodes to avoid collision. The selection is determined by the number of request to send (RTS) packets and the type of clear to send packets. Both theoretical channel capacity and simulation results show that the proposed selective decoding scheme MAC protocol outperforms the mitigation interference using multiple antennas and the parallel RTS processing protocols for the cases of (1) single data stream and (2) two independent data streams which are simultaneously transmitted by two independent transmitters.

• Journal of Satellite, Information and Communications
• /
• v.12 no.2
• /
• pp.51-55
• /
• 2017

This paper aims to maximize the energy harvesting rate and channel capacity in RF-energy harvesting networks (RF-EHNs) under the constraints of maximum transmit power and minimum quality of service (QoS) in terms of rate capacity for each user. We study a multi-user RF-EHN with frequency division multiple access (FDMA) in a Rayleigh channel. An access point (AP) simultaneously transmitting wireless information and power in the RF-EHN serves a subset of active users which have a power-splitting antenna. To gauge the network performance, we define energy efficiency (EE) and propose an optimization solution for maximizing EE with Lagrangian dual decomposition theory. In simulation results, we confirm that the EE is effectively maximized by the proposed solution with satisfying the given constraints.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2022.05a
• /
• pp.310-313
• /
• 2022

In the pipeline for supplying purified water to each household, measurements such as flow meters and pressure meters are installed at important points to monitor in real time. The measured data acquired to the central control room through wireless or wired communication, but data may not be acquired due to intermittent communication failures. Since then, even if the communication network is restored, data during the failure period is not stored on the site, or even if it is stored, data cannot be automatically stored in the database. Low cost with universally installed in the field in order to address these data logging by developing a module is compatible with PLC, automatically would like to make sure that we can recover in the database.