• Electronics and Telecommunications Trends
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• v.23 no.6
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• pp.59-69
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• 2008

IT 혁명의 근간이 되는 무선통신기술은 개인간의 통신을 가능하게 하여, 단순 정보 전달에서 음성 및 화상 통화가 언제, 어느 곳에서도 가능하게 되었다. 그러나 이런 단말기를 작동하게 하는 전력 또는 에너지는 여전히 유선으로 공급하거나 전지를 충전하여 사용한다. 만일 무선 통신뿐만 아니라 무선 에너지 전송까지 가능하다면 IT 기술은 또 다른 도약을 하게 될 것이다. 무선 에너지 전송은 백 년 전의 테슬라로부터 시작되어 지금까지 지속되어온 인류의 꿈이었다. 본 기고문에서는 20세기 초 무선 에너지 전송을 상상한 테슬라로부터 근래의 다양한 무선 에너지 전송 기술을 소개한다. 전자기파 방사를 이용한 기술과 전자기 유도현상을 이용한 무선 에너지 전송 기술을 개괄하고, 이러한 기존 기술을 넘어 근거리에서 공진 현상을 이용한 비방사 방식으로 에너지를 전송하는 MIT의 무선 에너지 전송 기술을 소개한다.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.425-430
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• 2013

Robust and high speed underwater communication is severely limited when compared to communications in terrestial. In free space, RF communication operates over long distances at high data rates. However, the obstacle in seawater is the severe attenuation due to the conducting nature. Acoustic modems are capable of long range communication up to several tens of kilometers, but it has low data-rate, high power consumption and low propagation speed. An alternative means of underwater communication is based on optics, wherein high data rates are possible. In this paper, the characteristics of underwater channel in the range of visible wavelength is investigated. And the possibility of optical wireless communication in underwater is also described. The LED-based transceiver and CMOS sensor module are integrated in the system, and the performance of image transmission was demonstrated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.2
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• pp.171-176
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• 2003

Meteor Burst Communication can provide effective and economical means of communication where long distance VHF NLOS(None Line of sight) data transmission is needed; often ranges more than 1200 km. It has been, however, so far considered unsuitable for distance as short as 700km application because of phenomenal decrease in burst durations, which leads to decreation of total duty rate of the system. This paper introduce experimental characteristics of very shot distance MB(Meteor Hurst) path. Also the occurring rate and average length measured on 50km paths between kyongsan-city to Andong-city shows that Meter Burst communication is useful communication system in mountain and valley communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.2
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• pp.160-170
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• 1988

This paper describes the outboard NIU(Network Interface Unit) using microprocessor and the hardware and software of concentrator for constructing star typed LAN(Local Area Network) based on token ring method. The NIU adapter can adapter up to four parallel and serial typed terminals. Because it has PAD function on input output data, any type of terminals can be adapted. Since the concentrator has logical switching circuit which enables data to bypass the faulted NIU adapter, this network prevents communication break. When user transmits and receives data, the concentrator constructs star typed LAN which connct both transmitting and receiving sides. A s result, this network eliminated ring latency time in other NIU exculding transmitting and receiving NIU. So the throughput of this LAN is increased. Because this LAN system consists of several modultes according to it's function, the expansion of function or the modification of method is easy.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11b
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• pp.1475-1478
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• 2002

멀티캐스트는 현재 일-대-일 통신서비스로 부터 일-대-다 또는 다-대-다 통신서비스에서 신뢰성을 요구하는 새로운 요구가 많아지고 있다. 그리고 최근 대두되고 있는 멀티미디어 응용을 지원하기 위해서는 광대역 네트워크의 링크, 실시간 전송, 보나 효과적인 멀티캐스트 프로토콜이 요구된다. 그러나 DVMRP, MOSPF, CBT, PIM 구조의 멀티캐스팅 프로토콜은 단지 송수신의 패킷의 경로비용으로 라우터 자체의 근거리 알고리즘이 적용되기 때문에 멀티캐스트가 수행될 때 통신의 전반적 사항인 통신처리능력, 대역폭, QoS(quality of service)대한 능력이 부족하다. 그러므로 멀티미디어에서 사용되는 패킷의 계층적 특성이 제외된 상태로 데이터가 전송되는 단점이 있다. 본 연구에서는 액티브 네트워크를 이용해서 카 데이터 패킷 전송을 위한 공정하고 실용적인 대역폭 사용하고 대역폭과 데이터처리능력을 액티브 전송 패킷을 통해서 액티브 라우터로 전송된 데이터를 필터링 해서 보나 효과적인 멀티미디어 데이터 패킷을 카 계층에 따라 다양한 수신자가 데이터 패킷을 전송 받고 액티브 라우터로부터 공정한 대역폭 전송할 수 있는 라우터를 시뮬레이션 상에서 구현하고 성능을 평가한다.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.7
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• pp.754-759
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• 2015

Nowadays, short distance communication systems with low power energy (LPE) are developed for identification and monitoring of site identification of vessel crews and passengers (SIVCP). LPE communication modules, such as Bluetooth low energy (BLE) and Zigbee, are used for short distance communications with LPE. These modules enable 1:N communications and their popularity is growing since the modules can be mounted on movable objects, such as mobile devices and human body. When these modules are used, the important factor that affects their operation time and design are the capacity and size of battery. Therefore, they must be made as small as possible, and the battery should be selected to be slightly smaller than the module. In this study, we calculate the theoretical life of batteries used in SIVCP BLE modules using data sheet and discharge characteristic graph under the condition of a 1/250 transmission-ratio (TR). We thus calculate experimental life by measuring transmission current for the same TR, and low speed mode current for a 1/5000 TR and measure long-term experimental life using 1/25 TR for days. Through these experiments, we verify experimental methods for the prediction and extension of battery life that would enable us to select appropriate sizes of batteries based on vessel usage and passenger types. The selections of the module TR and battery size are important factors affecting the cost reduction of module design, the battery maintenance, and passenger convenience.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.788-801
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• 1998

Meteor Burst Communication can provide effective and economical means of communication where long distance VHF NLOS data transmission is needed ; often ranges more than 1000 km. It has been, however, so far considered unsuitable for short distance application because of phenomenal decrease in burst durations, which leads to decreation of total duty rate of the system. This paper extensively analyzes characteristics of shot distance MB(Meteor Burst) path and shows the low duty rate may be improved by increasing burst rate through adapting antennal beam width to cover entire hot-spot region in the space and, by compensating effective burst length throughcutting down man-made noises introduced by antennal. Based on the analysis, we are developed a small-opening-cavity antennal, especially designed for short distance MB path. In operation, the antenna is to be buried under ground surface so as to improve directivity and reduces noise introduction. The antennal exhibits power gain of 3 dB with 90 degree beam width and thus enables to illuminate entire hot-spot regions with the elevation angle of 8-90 degree which is the case of transmission less than 100 km. Directivity horizontal to earth surface is suppressed to minimum which enables to cut man-made noises from near-by sources down to more than 3 dB from the level reported with conventional 4 element Yagi. A series of experiments performed on 100km MB paths have conformed that, with the antenna installed at receiving site, the burst rate and duration time have been noticed to increase by 10 and 20 percent respectively from the values obtained by conventional 4-element Yagi antennal under same testing condition.

• The KIPS Transactions:PartC
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• v.11C no.2
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• pp.229-234
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• 2004

In this study, the performance is compared between RFC compatible normal TCP and several speed constraints Ignored TCP. To do these, the main algorithms that constraints the transmit rate of TCP are modified. We have modified TCP protocol stack in a Linux kernel to compare the speeds between the standard TCP and our modified TCP. We find that if the destination is short distance away from the source and packet error is scarce then the speed differences between normal and modified TCP nay be negligible. However, if the destination is far away from the source and slow start algorithm is not adopted then the transfer time for small file is different greatly In addition, if packet error occurred frequently, our modified TCP is faster than the standard TCP regardless of distance.

• Journal of Navigation and Port Research
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• v.35 no.10
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• pp.811-816
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• 2011

In this paper, we analysis to consider the performance of PSPM (Phase Shift Pulse-position Modulation), the one of the low power communication technique, in near-field underwater sound channel by sea trial. PSPM is a QPSK(Quadrature Phase Shift Keying) modulation combined with PPM(Pulse Position Modulation) for low power communication in WBAN(Wireless Body Area Network). It is known that the bandwidth efficiency of PSPM is lower than conventional PSK but the power efficiency increases. In this paper, we will analyze the BER performance of PSPM using data acquired from the sea trials. The BER of QPSK was $6.04{\times}10^{-2}$, PSPM was $3.5{\times}10^{-1}$. Also, PSNR of QPSK was 9.37 dB and in case of PSPM was 9.11 dB.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.43-51
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• 2002

UWB 무선 기술은 매우 좁은 폭의 펄스를 기저대역에서 직접 변조하여 전송함으로써 근거리에서 매우 높은 데이터 전송 특성과 정확한 거리 및 위치 추정을 위한 높은 해상도를 제공하며 다중경로에 따른 페이딩 영향에도 강인한 특성을 보인다. 또한 매우 넓은 대역폭에 걸쳐 기존의 무선 시스템과 비교하여 상대적으로 매우 낮은 스펙트럼 전력 밀도가 분포함으로 기존의 협대역 및 광대역 시스템과 상호 간섭 없이 주파수를 공유할 수 있는 새로운 무선 기술로 급부상되고 있다. 본 논문에서는 UWB 신호의 스펙트럼 전력 밀도 및 다중 경로 전파 특성을 분석 고찰함으로써 향후 무선통신 시장의 새로운 변화를 가져올 UWB 무선 기술의 전파 특성을 소개 하고자 한다.