• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1349-1354
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• 2021

An All-in-one LED lantern is a light device to determine the fairway of ships in operation. The current all-in-one LED lantern powered by solar energy is challenged by insufficient power capacity due to limited sun hours. This article presents an all-in-one 9-Nautical mile LED lantern driven by solar and wind power that is abundant maritime renewable energy. Furthermore, the remote smart monitoring system is developed. A smart control system capable of remote control of the lantern was implemented by using the LED lantern device and monitoring system as IoT. This technology that realtime condition monitoring and remote control are developed for safe ship navigation. We expect that maintaining the accuracy and consistency of LED lanterns prevents marine accidents and reduces social costs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.7
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• pp.1032-1039
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• 2022

In this paper, we designed and implemented a cavity bandpass filter combined with a cross-coupling equalizer structure to enhance Group delay for 5G mobile network repeater, which can replace the SAW (Surface Acoustic Wave) type bandwidth filter used in the existing mobile communication system. Using the 3D EM simulation tool (HFSS), the resonance frequency, the coupling coefficient between resonators, and external quality coefficient between resonators were calculated. Based on this, a 12th bandpass filter was constructed to have attenuation characteristics of more than 20dB at the edge end of both sides of the band with a metal cavity structure with a frequency band of 3500MHz to 3600MHz and bandwidth of 97.85MHz. The designed bandpass filter satisfies the group delay time requirement for the 5G mobile communication standard and the in-band and out-band frequency responses.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1129-1139
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• 2022

Collision accidents happen frequently. The majority of ships involved in collisions in the coastal areas of Korea are middle and small size ships. The proportion of collision accidents is only 9% of all types of marine accidents; however, the number of casualties resulting from collisions is 34.4% of all human life damages. Generally, as reported by the people involved in these collisions, the navigation lights of the opponent ships were poor and invisible when the accident happened even though the weather and visibility were good. Furthermore, there are many insistences for poor navigation light conditions of the opponent ship in the bay or harbor. Therefore, it is necessary to analyze the present conditions and safety of navigation lights. Therefore, in this study, we examined the rules and books of navigation lights and compared it to that of other transportation systems, such as aircraft, trains, and road vehicles. Furthermore, we analyzed the current marine traf ic circumstances and ship collision accidents that happened in the past 5 years. Additionally, a questionnaire was prepared to gather the opinion of ship experts and secure the objectivity for improvement methods of navigation lights. Finally, methods to improve the navigation lights on ships were devised.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.12
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• pp.1898-1907
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• 2022

Every year, many shipping companies provide seaman safety education programs periodically to reduce ocean-traffic accidents. However, undertaking the regular safety training for seaman has been difficult because of litimation of space and time. Recently, VR technolgy is received attentions to overcome previous problems. It can provide users educational interactions between a user and virtual environment and fulfill sustainable teaching. In this paper, VR-based safety education content for sailors has been developed, and it includes four programs. Also, survey was conducted with four questionnaires such as immersiveness, easy to experience, satisfaction of education contents, comparative evaluation between traditional education program and VR education contents. As the result, immersiveness questionnaire could be gain 53.83% positive assessment, and easy to experience could be gain 65.38% positive assessment, and satisfaction could be gain 69.23% positive assessment. Lastly, comparative evaluation between traditional education program and VR education contents could be gain about 46% positive and 34% neutral assessments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.2C
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• pp.160-169
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• 2002

An ATM-PON (Passive Optical Network) system consists of an OLT (Optical Line Termination), multiple ONUs (Optical Network Units) and the optical fiber which has a PON (Passive Optical Network)configuration with a passive optical splitter. To avoid cell collisions on the upstream transmission, an elaborate procedure called as ranging is needed when a new ONU is installed. The ONU can send upstream cells according to the grant provided by the OLT after the procedure. To prevent collisions being generated by the variation of several factors, OLT must performs continuously the cell phase monitoring. It means that the OLT predicts the expected arrival time, monitors the actual arrival time for all upstream cells and calculates the error between the times. Accordingly, TC (Transmission Convergence) chip in the OLT needs a predictor which predicts the time that the cell will arrive for the current grant. In this paper, we implement the predictor by using shift registers of which the length is equivalent to the equalized round trip delay. As each register consists of 8 bit, OLT can identify which ONU sends what type of cell (ranging cell, user cell, idle cell, and mini-slot). Also, TC chip is designed to calculate the effective bandwidth for all ONUs by using the function of predictor. With the time simulation and the measurement of an implemented optical board, we verify the operation of the predictor.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8B
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• pp.473-481
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• 2007

We are interested in the PON which is easy to install and inexpensive to maintain, as it is a solution of the FTTH that is a core technology of the BcN access network. When a new ONU is connected, TDMA PON has a procedure called ranging that OLT measures the distance and allocates the equalized delay to it in order to provide the same logical distance to all ONUs. For the procedure, the OLT has to open a time window several times and already activated ONUs cannot transmit a data to the upstream during the periods. Accordingly, it is important to reduce the window size for saving the bandwidth and providing a user the service smoothly. In this paper, we investigate the ONU activation method of G-PON based on ITU-T G984.3 and suggest an advanced method(algorithm I) that minimizes the window size without information of ONU distance. The size can be reduced by calculating the pre-assigned delay obtained during Serial number state. Also, we compare it with another(algorithm II) with information of distance. As a result, the window size reduces to $50{\sim}90%$ for the algorithm I and 99% for algorithm II during the ONU activation process.

• The Journal of the Acoustical Society of Korea
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• v.35 no.3
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• pp.167-174
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• 2016

Underwater communication is difficult to increase the communication capacity because the carrier frequency is lower than that of radio communications on land. This is limited to the bandwidth of the signal under the influence of the characteristics of an ocean medium. As the high transmission speed and large transmission capacity have become necessary in the limited frequency range, the studies on MIMO (Multiple Input Multiple Output) communication have been actively carried out. The performance of the MIMO communication is lower than that of the SIMO (Single Input Multiple Output) communication because cross-talk occurs due to multiusers along with inter symbol interference resulting from the channel characteristics such as delay spread and doppler spread. Although the adaptive equalizer considering multi-channels is used to mitigate the influence of the cross-talk, the algorithm is normally complicated. In this paper, time reversal mirror technique with the characteristic of a self-equalization will be applied to simplify the compensation algorithm and relieve the cross-talk in order to improve the communication performance when the signal transmitted from two channels is received over interference on one channel in the same time. In addition, the performance of the MIMO communication based on the time reversal mirror is verified using data from the SAVEX15(Shallow-water Acoustic Variability Experiment 2015) conducted at the northern area of East China Sea in May 2015.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.11
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• pp.51-62
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• 2003

This paper presents a novel survivor memeory management and decoding techniques with sequential backward state transition control in the trace back Viterbi decoder. The Viterbi algorithm is an maximum likelihood decoding scheme to estimate the likelihood of encoder state for channel error detection and correction. This scheme is applied to a broad range of digital communication such as intersymbol interference removing and channel equalization. In order to achieve the area-efficiency VLSI chip design with high throughput in the Viterbi decoder in which recursive operation is implied, more research is required to obtain a simple systematic parallel ACS architecture and surviver memory management. As a method of solution to the problem, this paper addresses a progressive decoding algorithm with sequential backward state transition control in the trace back Viterbi decoder. Compared to the conventional trace back decoding techniques, the required total memory can be greatly reduced in the proposed method. Furthermore, the proposed method can be implemented with a simple pipelined structure with systolic array type architecture. The implementation of the peripheral logic circuit for the control of memory access is not required, and memory access bandwidth can be reduced Therefore, the proposed method has characteristics of high area-efficiency and low power consumption with high throughput. Finally, the examples of decoding results for the received data with channel noise and application result are provided to evaluate the efficiency of the proposed method.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.3
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• pp.1-13
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• 2020

When pedestrians cross a pedestrian crossing during a pedestrian signal, there is a problem that pedestrians are exposed to the danger of traffic accidents due to permissive-left turning and right-turning vehicles. In order to solve this problem, there is an increasing demand to improve the traffic signal system to increase pedestrian safety at the signal crossing. This study aims to examine the feasibility of introducing a leading pedestrian interval(LPI) to prevent conflict between unprotected left and right turn vehicles and pedestrians. In this study, the need for LPI was surveyed by experts and the general public. As a result of the survey, many opinions indicated that the introduction of LPI was necessary. In addition, after selecting the non-protected left and right turn pilot operation targets, LPI was installed on two signal intersections. After installation, the speed analysis of the arrival vehicle in the pedestrian crossing and the violation rate of the pedestrian signal were analyzed. As a result of analysis, when the walking signal was equalized, the speed of the arriving vehicle in the pedestrian crossing was reduced, and the violation rate of the walking signal was improved.

• Journal of Advanced Navigation Technology
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• v.6 no.1
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• pp.37-43
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• 2002

This paper describes the performance evaluation and analysis of Wireless Local Area Network (W-LAN) in the 5 GHz ISM-band in compliance with IEEE 802.11a. At present, most W-LAN products are based on 2.4 GHz band, but low speed (11Mbps) has the limitation to serve systems demanding high-speed data transmission. To solve this problem, it is necessary to design next generation W-LAN system with 54Mbps in the 5GHz. It is sure that implementation of next generation W-LAN will bring competitive advantages. In particular, it will support telecommunications for high-speed mobile environments as well as for fixed places such as a school zone, a lecture room, a hospital and other premises. A few simulation methods are applied to more accurate and reliable performance analysis of next generation W-LAN. To verify if continuous data service is supported for a high-speed mobile notebook, multi-path fading channels between wireless Access Point (AP) and wireless Network Interface Card (NIC) are modeled. In addition, low interference is analyzed via convolutional codes and Orthogonal Frequency-Division Multiplexing (OFDM). Also, to obtain reliable Bit Error Rate (BER), a single tap Least Mean Square (LMS) equalizer is applied. Given the above simulation, next generation W-LAN is an ideal solution for continuous data transmission in high-speed mobile environments.