• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.481-482
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• 2020

다양한 재난경보 전달 매체 중 재난문자 서비스는 재난 발생 시 재난 지역과 관련된 대국민 대상으로 재난경보를 빠르고 신뢰성 있게 전송할 수 있는 보편 매체이다. 현재 국내 재난문자 서비스는 2G/4G 셀룰러 환경에서 셀룰러 이동 단말기에 재난문자를 전송한다. 특히 4G 이상의 셀룰러 시스템은 재난문자 전송을 위하여 SIB를 이용한다. 그러나 현 재난문자 서비스는 셀룰러 이동 단말기만 수신이 가능한 한계를 보인다. 재난경보 수신의 성공률을 높이기 위하여 다양한 수신 단말기의 재난문자 서비스 지원이 필수적이다. 현재 NB-IoT는 4G 셀룰러 환경을 기반으로 광범위한 지역에 저전력 서비스를 제공한다. 본 논문에서는 NB-IoT가 재난문자 수신을 위하여 필요한 프로토콜 규격과 NB-IoT 기반의 재난문자 서비스를 위한 네트워크 구조를 제시한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2021.11a
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• pp.116-118
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• 2021

초고속 해상무선통신망(LTE-Maritime)은 바다 어민의 안전과 항해 중인 선박의 편의 서비스 제공을 위해 대한민국 연안으로부터 최대 100km 까지 해역을 LTE(Long Term Evolution) 통신 체계로 구축한 세계 최초의 해상 무선통신망이다. 본 논문은 초고속 해상무선통신망의 활용성을 높이기 위해 다용한 용도로 개발된 무선설비의 호환성, 신뢰성, 안정성을 확보하기 위한 상호운용성 시험 방안을 논의해보고자 한다. 본 논문은 이종 통신장비 및 이종 무선설비 간의 상호운용성을 단말(무선설비)과 시스템의 종단간 통신품질 측정을 통해 서비스 커버리지 성능, 무선데이터 전송 속도 및 전송성공률 등을 검토해 보고, 각 품질 지표를 검증할 수 있는 시험 구성 방안, 시험 항목 및 절차, 측정 결과 분석 방법 등을 다각도로 살펴보고자 한다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.68-76
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• 2008

It is difficult to maintain mutes in the mobile ad hoc network (MANET) due to the high probability of disconnected routes break by frequent change of topology. The links can have the different reliability about data transmission due to these characteristics. Hence a measure which can evaluate this reliability and a algorithm which reflects this are required. In this paper, we propose routing algorithm based on reliability about transmission. First the bayesian inference which infers the hypothesis by past information is considered to obtain the link's transmission reliability. The other is that the link-based reliability estimation model which considers each link's reliability additionally is proposed while the standard uses only Dijkstra's shortest path algorithm. the simulation results using NS-2 show that the performance of proposed algorithm is superior to the standard OLSR in terms of throughput and stability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.1
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• pp.268-278
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• 2017

In this paper, we propose two novel detection schemes with low-complexity based on the unified receiver architecture which minimizes a fundamental tradeoff at rate-energy region in SWIPT system. The proposed detection schemes are twofold: The two-stage detection scheme and Euclidean distance combination detection scheme. The two-stage detection scheme detects amplitude information of symbols from rectified signals for energy harvesting. In the sequel, it detects symbols based on phase information of baseband signals for information decoding. The Euclidean distance combination detection scheme detects symbols using linear positive-weighted sum of two metrics: Euclidean distance based on baseband signals for information decoding and Euclidean distance based on rectified signals for energy harvesting. For numerical results, we confirm that the proposed detection scheme can achieve better performance than the conventional scheme in terms of symbol error rate, symbol success rate-energy region and achievable rate-energy region.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.2839-2846
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• 2014

New VHF band for use in VDE is determined by WRC-12 due to the overload of AIS VDL, and the system characteristics of the VDE is recommended as ITU-R M. 1842-1. CS-TDMA, a multiple access method of AIS class B, is recommended as that of the VDE. It is inefficient for CS-TDMA just applying the report interval used in AIS class B to transmit high speed data with higher payload in the aspect of efficiency. In this paper, a simulation is executed in order to determine adequate report interval according to the number of active ships that affects directly network traffic. To this end, the performance of CS-TDMA, which includes the number of received packets, reception success rate, channel utilization, and collision rate, is investigated via a simulation.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.4
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• pp.86-94
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• 2012

VANETs can provide traffic warring service to help drivers drive safely based on the information of the traffic condition. The driver can drive safely through the warning service information provided by the VANET and know the traffic condition exactly more than through only the sight of driver. In this paper we suggest a new mechanism of updating the table to broadcast the message more rapidly based on the table driven method as the way of sending the emergency message in the VANETs. When updating the table, nodes sends only based on the message transmission success rate. In the result of simulation we could find that the suggested mechanism would reduce the delay time of the emergency message broadcast compared to the existing mechanism.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1589-1598
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• 2014

To support the WBAN, IEEE 802.15 Task Group 6 announced standardized documents on technical requirements of the PHY and MAC. In the IEEE 802.15.6 MAC protocol, CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance) algorithm is performed based on the eight-level priorities according to the type of traffics of the periodic data from medical sensor nodes. Several nodes, which detected the changed bio signals, transmit emergency data at the same time, so latency could be higher than emergency latency and energy consumption will increase. In this thesis, we proposed a CSMA/CA algorithm in WBAN to solve these problems. Simulations are performed using a Castalia based on the OMNeT++ network simulation framework to estimate the performance of the proposed superframe and algorithms. Performance evaluation results show that the packet transmission success rate and energy efficiency are improved by reducing the probability of collision using the proposed MAC protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.9
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• pp.606-613
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• 2014

The Internet of Things (IoT), which has recently attracted attention as next-generation IT industry, is based on a wired and wireless network platform that can connect various Things. However, it is challenging to implement the IoT platform because of the heterogeneity of the network. Particularly, the ZigBee transmission may be significantly harmed due to Wi-Fi with the relatively much higher power, and this is one of the reason making the platform implementation difficult. In this paper, the ZigBee transmission is measured and analyzed by the BEB algorithm for finding the slot time when ZigBee can transmit, and an actual transmission happens stochastically depending on the network environment. The simulation results show that it guarantees high success rate of the ZigBee transmission by overcoming Wi-Fi interference in the 2.4 GHz frequency band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.712-721
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• 2012

In this paper, we propose an Enhanced cross-layer Geographic Forwarding (EGF) protocol for wireless sensor networks (WSNs). EGF uses an optimal back-off time to make the packet forwarding decisions using only source and destination's location information and energy cost without information about neighbor nodes' location or the number of one hop neighbor nodes. EGF is also a cross-layer protocol by combining efficient asynchronous MAC and geographic routing protocol. The proposed protocol can find optimal next hop location quickly without broadcasting node's location update and with minimizing overhead. In our performance evaluation, EGF has better performance in terms of packet success ratio, energy efficiency and end-to-end delay in wireless sensor networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.4
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• pp.833-838
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• 2003

This paper presents novel methods of recognizing license plates of passing vehicles outdo(n. In particular, the proposed method is much robust for inclined plates caused by the changes of camera placement. To acquire fine images of quickly passing vehicles under a wide range of illumination conditions, we developed a sensing system having superb characteristics. We expanded the dynamic range and eliminated the blurring of images of fast moving vehicles by synthesizing a pair of synchronized images with different intensities. furthermore, to extend the flexibility of the positioning of the TV camera, we propose a recognition algorithm that can be applied to inclined plates. The performance of the integrated system was investigated on real images of vehicles captured under various illumination conditions. The recognition rates of over 99% (conventional plates) and over 97% (highly inclined plates) shows that the developed system is effective for license plate recognition.