• 한국전자통신학회논문지
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• 제8권1호
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• pp.55-64
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• 2013

본 논문에서는 UWB 기술 기반 무선 USB(WUSB) 프로토콜에서, 디바이스들의 이동성으로 인해 발생하는 Private Distributed Reservation Protocol (DRP) 예약 충돌 현상을 분석한다. 그리고 Private DRP 예약 충돌시 발생하는 성능 저하를 감소시키기 위해 Private DRP 릴레이 통신 기술을 제안한다. 본 논문에서 제안하는 Private DRP 릴레이 통신 프로토콜은 충돌대상 디바이스에게 예약된 자원을 유지할 수 있도록 Direct Link 뿐만 아니라, Private DRP 예약 충돌 시 릴레이 노드를 경유하여 또 다른 Indirect Link 링크를 빠르게 예약할 수 있는 분산적인 자원 예약 프로토콜을 제안한다.

• Journal of Communications and Networks
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• 제17권3호
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• pp.231-240
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• 2015

To facilitate the base station planning in high speed railway communication systems, it is necessary to consider the functional relationships between the base station transmit power and space parameters such as train velocity and cell radius. Since these functions are able to present some inherent system properties determined by its spatial topology, they will be referred to as the power-space functions in this paper. In light of the fact that the line-of-sight path persists the most power of the received signal of each passing train, this paper considers the average transmission rate and bounds on power-space functions based on the additive white Gaussian noise channel (AWGN) model. As shown by Monte Carlo simulations, using AWGN channel instead of Rician channel introduces very small approximation errors, but a tractable mathematical framework and insightful results. Particularly, lower bounds and upper bounds on the average transmission rate, as well as transmit power as functions of train velocity and cell radius are presented in this paper. It is also proved that to maintain a fixed amount of service or a fixed average transmission rate, the transmit power of a base station needs to be increased exponentially, if the train velocity or cell radius is increased, respectively.

• Wind and Structures
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• 제31권1호
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• pp.21-29
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• 2020

The wind field measurement of severe winds such as hurricanes (or typhoons), thunderstorm downbursts and other gales is important issue in wind engineering community, both for the construction and health monitoring of the wind-sensitive structures. Although several wireless data transmission systems have been available for the wind field measurement, most of them are not specially designed for the wind data measurement in structural wind engineering. Therefore, the field collection is still dominant in the field of structural wind engineering at present, especially for the measurement of the long-term and high-frequency wind speed data. In this study, for remote wind field measurement, a novel wireless long-term and high-frequency wind data acquisition system with the functions such as remote control and data compression is developed. The system structure and the collector are firstly presented. Subsequently, main functions of the collector are introduced. Also novel functions of the system and the comparison with existing systems are presented. Furthermore, the performance of this system is evaluated. In addition to as the wireless transmission for wind data and hardware integration for the collector, the developed system possesses a few novel features, such as the modification of wind data collection parameters by the remote control, the remarkable data compression before the data wireless transmission and monitoring the data collection by the cell phone application. It can be expected that this system would have wide applications in wind, meteorological and other communities.

• 한국인터넷방송통신학회논문지
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• 제8권4호
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• pp.15-24
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• 2008

본 논문은 모바일 ad-hoc 무선 센서 네트워크에서 전력 절약 고속의 멀티미디어 서비스를 지원하는 Cross-Layer 전송 구조(CLTA)를 제안한다. 본 논문의 주요한 목적은 모바일 ad-hoc 무선 센서 네트워크에서 경로들의 생존시간(lifetime)을 증가시키기 위해서 노드들의 이동성 기반위에서 경로의 안정성을 결정하는 방법과 전송전력을 절약하는 방법을 제안하고 보여주는 것이다. 이러한 목적을 달성하기 위해서 본 연구에서는 네트워크 계층 기술과 물리계층 기술의 융합과 상호 유기적인 관계로 인해서 시너지 효과를 얻을 수 있는 Cross-Layer 구조 전략을 제안한다. 기존의 연구들은 주로 고정된 노드들로 구성된 센서 필드 환경에서 연구가 진행된 반면에, 본 논문은 센서 필드에서 고정된 노드들뿐만 아니라 이동 센서노드들도 함께 고려한 좀 더 실제적인 환경에서 연구가 진행된다. 제안된 구조(CLTA)의 성능평가는 시뮬레이션과 이론적인 분석을 통하여 이루어진다.

• Journal of electromagnetic engineering and science
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• 제8권2호
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• pp.41-46
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• 2008

A bandwidth and power efficient high speed ubiquitous sensor network(USN) for realizing a ubiquitous society is a great challenge for researcher community. In this paper we incorporate a cooperative transmission protocol within a special type of multi-code modulation to meet these requirements. Multi-code(Mc) modulation has been developed for high-speed data transmission over wireless channels. We proposed a new class of orthogonal codes for multi-code modulation which is an orthogonal subset of orthogonal codes(OSOC). Our proposed OSOC structure allows us to use only one relay to cooperate M nodes that effectively reduces the bandwidth and power requirement. This protocol is similar to spread-spectrum(SS) technique that can reduce both broad and narrow band jamming.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.131-132
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• 2008

It is necessary to develop a high-speed wireless transmission system, which is able to send medical informations to the emergency medical center during emergency patient transportation. In this research, a system which transmits patient’s vital signs and a real-time audio/video contents of the event has been designed, developed, and the suitability of the system has been verified. Test results indicate that the system is capable of transmitting vital signal data, including 17 numeric data, 12 waveforms and 113 events, reading the affected part by forwarding a $320{\times}240$ pixel image at 2fps. Also, the full-duplex voice transmission of the system at 8bit/64kbps is enough to make stable communication between emergency medical technicians and hospital professionals possible. After numerous hours of driving, the packet loss of patient vital signs is 0.013%.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 추계학술대회
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• pp.139-140
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• 2010

This paper presents an indoor prototype for wireless digital signal transmission using Visible Light Communications (VLC) in which high power Light Emitting Diode (LED) is used. Using low cost and off-the-shelf components, the transmitter module is constructed using an AVR Atmega128 microcontroller and commercial white beam LEDs. Modulating the light intensity of the LED enables digital signals to be transmitted across the optical link. The receiver module employs a high speed PIN photodetector for optical signal detection and a recovery circuit for optical-electro signal conversion. By sending digitalized data via VLC technology, many applications can be realized in the areas of consumer advertising, traffic safety information and disaster control.

• Wind and Structures
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• 제20권6호
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• pp.739-749
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• 2015

Field measurement of wind characteristics is of great significance for the wind engineering community. High-frequency anemometers such as ultrasonic anemometers are widely used to obtain the high-frequency fluctuating wind speed time history. However, conventional instrumentation systems may suffer from low efficiency, non-real time transmission and higher maintenance cost, and thus are not very appropriate in the field measurement of strong winds in remote areas such as mountain valleys. In order to improve the field measurement performance in those remote areas, a wireless high-frequency anemometer instrumentation system for field measurement has been developed. In this paper, the architecture of the proposed instrumentation system, and measured data transmission and treatment will be presented firstly. Then a comparison among existing instrumentation systems and the proposed one is made. It shows that the newly-developed system has considerable advantages. Furthermore, the application of this system to the bridge site located in the mountain valley is discussed. Finally, typical samples of measured data from this area are presented. It can be expected that the proposed system has a great application potential in the wind field measurement for remote areas such as the mountainous or island or coastal area, and hazardous structures such as ultra-voltage transmission tower, due to its real-time transmission, low cost and no manual collection of data and convenience.

• 한국항행학회논문지
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• 제12권2호
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• pp.154-163
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• 2008

이동 광대역 무선접속 네트워크에서 다수의 사용자들은 한 기지국에 접속하여 다양한 서비스를 이용하게 되는데, 기지국은 고속인 유선 링크와 저속인 무선 링크의 데이터 전송을 중계하므로, 많은 사용자가 통시에 여러 서비스를 이용하게 될 경우 기지국의 버퍼 공간이 부족해 패킷이 손실된다. 하지만 종단간 신뢰성 보장을 위해 유무선을 막론하고 널리 쓰이는 TCP는 패킷 손실이 발생될 경우, 단순히 망의 혼잡에 의한 것으로 판단하여 전송률을 줄이게 되고, 이후 전송률을 다시 올리는 정도에 차이가 발생하게 되어 TCP fairness가 악화된다. 본 논문에서는 TCP 송신단의 전송률에 따라 차등적으로 그 전송률을 제어하여, 망이 혼잡해 지는 것을 미연에 방지하고 일정 수준의 TCP fairness를 보장하는 기법을 제안한다. 시뮬레이션을 통해 그 성능을 분석한 결과, 제안하는 기법이 쓰이지 않을 때에 비해, 각각의 TCP flow별 처리율이 비슷하게 유지되어, TCP fairness가 일정한 수준으로 향상됨을 확인할 수 있었다.

• 한국정보기술응용학회:학술대회논문집
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• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
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• pp.187-190
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• 2005

Ultra wideband (UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geolocation, and other applications. The energy of UWB signal is extremely spread from near DC to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional mobile wireless systems sharing the frequency bands such as WCDMA system. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a direct-sequence spread-spectrum UWB source and an impulse radio UWB source, to a WCDMA digital transmission system. The average frame error rate degradations are presented. From these experimental results, we show that in all practical cases UWB system can coexist with WCDMA terminal without causing any dangerous interference.