• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권1호
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• pp.325-339
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• 2018

In this paper, we propose a joint adaptive combining and variable tap-length multiuser detector (MUD) for amplify-and-forward (AF) underwater acoustic cooperative interleave-division multiple access (IDMA) communication system. The proposed MUD jointly realizes tap-length adjustment, adaptive combining, and multiuser detection. In contrast to the existing methods, the proposed detector can adaptively combine the received signals from different nodes at destination, and does not need the assumption that full and perfect channel state information (CSI) of all the links at the receiver is known. Moreover, the proposed detector can adaptively adjust the tap coefficient vector and tap-length of each branch according to the specific channel profile of each branch. Simulation results validate the feasibility and show the advantages of the proposed detector against existing counterparts.

• Journal of Platform Technology
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• 제9권3호
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• pp.18-23
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• 2021

초연결사회로 발전됨에 따라 정보통신의 역할이 크게 증대되고 통신재난이 발생할 경우 사회 인프라, 국가핵심기반의 서비스 중단 및 국민생활에 지대한 영향을 초래한다. 또한 정보통신분야는 산업구조가 고도화되면서 이에 대한 의존도가 급격히 증대하였기 때문에 재난으로부터 안전한 정보통신 환경 조성을 위해서는 체계적인 관리가 필요하다. 본 논문에서는 체계적인 관리를 위해서 정보통신, 금융, 보건 및 의료 등 국가핵심기반 및 다양한 분야에서 중요한 역할을 수행하고 있는 정보통신인프라에 발생할 수 있는 재난의 유형 및 위험에 대하여 분석하였다. 정보통신인프라에 재난이 발생할 경우 국가핵심기반의 서비스 중단 및 국민생활에 지대한 영향을 초래할 것으로 사료된다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 춘계학술대회
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• pp.738-740
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• 2017

가시광 통신은 빛을 사용한 통신방식이며, RF 통신에 비해 단일 공간 내 보안성을 보장하는 장점이 있다. 하지만 빛의 가시선을 벗어난 영역의 경우 통신단절 현상이 발생한다. 이에 본 논문에서는 가시광 통신의 커버리지 확장과 통신단절 현상을 극복하기 위해 릴레이 모듈을 제안한다. 제안하는 릴레이 모듈은 target ID를 포함한 데이터 패킷을 인접한 가시광 모듈을 통해 순차적으로 전달함으로써 데이터를 송수신한다. 데이터 전송 실험을 통해 전송범위의 확장과 가시선을 벗어난 영역에서의 데이터 수신을 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.17-18
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• 2007

Mobile WiMAX technology is the key solution for providing high speed internet services at anytime and anywhere in mobile environments as 3.5th wireless technology between 3rd generation and 4th generation wireless technology, and the service demands shall be rapidly increased in future some years. This paper analyzed the QoS performance of Mobile WiMAX technology recommended by IEEE 802.16e specification under the restricted simulation conditions and environments. The major metrics for analyzing QoS performance of Mobile WiMAX are 1) total packet drop rates; 2) transmission / receive packet sizes; 3) end to end delay in node 2; 4) packet drop rate by mobile terminal mobility.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권3호
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• pp.256-265
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• 2017

In this paper, an ascheme is proposed for multiuser underwater acoustic communication by using the multi-chirp rate signals. It differs from the well known TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access) or CDMA (Code Division Multiple Access), by assigning each users with different chirp-rate carriers instead of the time, frequency or PN code. Multi-chirp rate signals can be separated from each other by FrFT (Fractional Fourier Transform), which can be regarded as the chirp-based decomposing, and superior to the match filter in the underwater acoustic channel. VTRM (Virtual Time Reverse Mirror) is applied into the system to alleviate the ISI caused by the multipatch and make the equalization more simple. Results of computer simulations and pool experiments prove that the proposed multiuser underwater acoustic communication based on the multi-chirp rate exhibit well performance. Outfield experments carrie out in Xiamen Port show that using about 10 kHz bandwidth, four users could communicate at the same time with 425 bps with low BER and can match the UAC application.

• Journal of Information Processing Systems
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• 제14권6호
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• pp.1347-1360
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• 2018

Owing to limited energy in wireless devices power saving is very critical to prolong the lifetime of the networks. In this regard, we designed a cross-layer optimization mechanism based on power control in which source node broadcasts a Route Request Packet (RREQ) containing information such as node id, image size, end to end bit error rate (BER) and residual battery energy to its neighbor nodes to initiate a multimedia session. Each intermediate node appends its remaining battery energy, link gain, node id and average noise power to the RREQ packet. Upon receiving the RREQ packets, the sink node finds node disjoint paths and calculates the optimal power vectors for each disjoint path using cross layer optimization algorithm. Sink based cross-layer maximal minimal residual energy (MMRE) algorithm finds the number of image packets that can be sent on each path and sends the Route Reply Packet (RREP) to the source on each disjoint path which contains the information such as optimal power vector, remaining battery energy vector and number of packets that can be sent on the path by the source. Simulation results indicate that considerable energy saving can be accomplished with the proposed cross layer power control algorithm.

• 한국정보통신학회논문지
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• 제23권4호
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• pp.423-430
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• 2019

자동차산업과 ICT 기술의 융합 분야는 크게 상용서비스 분야와 Cooperative-ITS (C-ITS) 서비스 분야로 나뉠 수 있다. C-ITS 서비스 분야는 더 안전한 운송, 더 친환경적이고 효율적인 교통, 및 더 예측가능하고 생산적인 이동성을 제공하는 것을 목표로 하는 분야로서 V2X 통신기술이 사용되고 있다. 최근 이슈가 되고 있는 자율주행자동차와 커넥티드 카의 융합을 위해서는 높은 데이터 전송율과 낮은 전송 지연, 그리고, 낮은 전송 오류율을 요구한다. 이를 위하여 최근의 WAVE와 C-V2X (LTE-V2X, 5G-V2X) 성능 비교에 관심이 증폭되고 있으며, 통신 기술별 응용서비스들이 연구되고 있다. 본 논문에서 하이브리드 V2X 통신시스템의 응용서비스 성능평가 방법에 대해 설계하였고, 패킷에러율(PER) 성능의 감소는 차량속도가 아닌 통신 거리의 증가에 의해 발생하는 것으로 보이는 결과 등을 확인하였다.

• Journal of Communications and Networks
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• 제18권5호
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• pp.818-825
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• 2016

Network management and anomaly detection are challenges in high-speed networks due to the high volume of packets that has to be analysed. Flow-based analysis is a scalable method which reduces the high volume of network traffic by dividing it into flows. As sampling methods are extensively used in flow generators such as NetFlow, the impact of sampling on the performance of flow-based analysis needs to be investigated. Monitoring using sampled traffic is a well-studied research area, however, the impact of sampling on flow-based anomaly detection is a poorly researched area. This paper investigates flow sampling methods and shows that these methods have negative impact on flow-based anomaly detection. Therefore, we propose an efficient probabilistic flow sampling method that can preserve flow traffic distribution. The proposed sampling method takes into account two flow features: Destination IP address and octet. The destination IP addresses are sampled based on the number of received bytes. Our method provides efficient sampled traffic which has the required traffic features for both flow-based anomaly detection and monitoring. The proposed sampling method is evaluated using a number of generated flow-based datasets. The results show improvement in preserved malicious flows.

• 한국해양공학회지
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• 제18권6호
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• pp.44-50
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• 2004

A small, highly-trained crew working on the ship's automation has contributed to the improvement of operations and the labor environment on board ship. However, at the same time, having a small crew adds more responsibility to the ship's officers to safely operate and manage the ship. With the use of information and computer technology, efforts are being made towards the development of a system that will concentrate important information from the various pieces of navigational equipment. The purpose of this study is to set up and implement an integrated marine data networking and communication system on the training-research ship. Information relating to navigation, engine and office automation are investigated and analyzed, and implementation methods associated with navigation, engine and management information system were designed and presented. In addition, the networking system of the navigational signal interface unit for the integrated communication system, and the data communication method between the ship and land are also discussed.

• 한국정보기술학회 영문논문지
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• 제10권2호
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• pp.111-123
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• 2020

The core competencies for the 21st century are creativity, critical thinking, collaboration, and communication. In recent classes where ICT (information, communication, and technology) is grafted, a lot of efforts are also being made to increase such competencies. According to a research work, ICT is most often used as a communication channel between teachers and students or as an online collaboration tool among students. However, ICT has only played a role as a guideline for instruction, but not included in the curriculum until now. The research on methods how to integrate technology into teaching and learning is in full swing due to the development of technology and the advent of Covid-19. In this paper, we propose a technology integration hierarchy model, namely K-TIHM that can be combined with STEAM education. Since only learning environments have been proposed in the existing research for technology-based STEAM education, our model proposes a series of technology integration hierarchy that can be applied by school age along with STEAM. Also, we analyze the differences in among the Korea's ICT education operation guidelines, the Korea's Software education guidelines, and ours. The proposed model can help developing the primary and secondary school curriculum integrated with technology.