• ETRI Journal
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• 제26권5호
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• pp.405-412
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• 2004

MC-CDMA, a multicarrier (MC) modulation scheme based on code division multiple access (CDMA), is the most likely candidate for the next generation of mobile radio communications. The rate compatible punctured turbo (RCPT) coded hybrid automatic repeat request (HARQ) has been found to give improved throughput performance in a direct sequence (DS) CDMA system. However, the extent to which the RCPT HARQ improves the throughput performance of an MC-CDMA system has not been fully understood. In this paper, we apply the RCPT HARQ to MC-CDMA and evaluate by computer simulations its performance in a frequency selective Rayleigh fading channel. We found that the performance of RCPT HARQ MC-CDMA is almost insensitive to channel characteristics. The performance can be drastically improved with receive diversity combined with space-time transmit diversity. In addition, the comparison of RCPT HARQ MC-CDMA, orthogonal frequency division multiplexing, and DS-CDMA shows that under similar conditions the throughput of MC-CDMA is the best in a frequency selective fading channel.

• 한국산업정보학회논문지
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• 제9권2호
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• pp.89-95
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• 2004

CDMA(Code Division Multiple Access)는 이동통신에서 다수의 사용자들이 동시에 시간과 주파수를 공유하며 접속이 가능한 다중접속(Multiple Access) 방식의 하나이다. 그렇지만 이동통신은 주파수라는 한정된 자원을 이용하기 때문에 용량이 제한된 가용 주파수 자원을 여러 사람이 효율적으로 공유할 수 있도록 하는 다중접속이 이동통신에서는 필수적인 기술이다. CDMA는 홈네트워크, 군사용, 상업용뿐만 아니라 의료분야에까지도 다양하게 응용되어가고 있다. 본 논문은 기존 양면보드 방식이 아닌 PCB 8계층의 적층방식을 단면보드 회로로 구성하여 RF(Radio Frequency)특성을 유지하며, 슬롯형의 커넥터를 적용한 Cellular Band의 CDMA 모듈의 설계 및 성능 분석 결과를 제시한다.

• Journal of Communications and Networks
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• 제18권2호
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• pp.201-209
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• 2016

In wireless sensor networks (WSNs) duty cycling has been an imperative choice to reduce idle listening but it introduces sleep delay. Thus, the conventional WSN medium access control protocols are bound by the energy-latency tradeoff. To break through the tradeoff, we propose a radio wave sensor called radio frequency (RF) wakeup sensor that is dedicated to sense the presence of a RF signal. The distinctive feature of our design is that the RF wakeup sensor can provide the same sensitivity but with two orders of magnitude less energy than the underlying RF module. With RF wakeup sensor a sensor node no longer requires duty cycling. Instead, it can maintain a sleep state until its RF wakeup sensor detects a communication signal. According to our analysis, the response time of the RF wakeup sensor is much shorter than the minimum transmission time of a typical communication module. Therefore, we apply duty cycling to the RF wakeup sensor to further reduce the energy consumption without performance degradation. We evaluate the circuital characteristics of our RF wakeup sensor design by using Advanced Design System 2009 simulator. The results show that RF wakeup sensor allows a sensor node to completely turn off their communication module by performing the around-the-clock carrier sensing while it consumes only 0.07% energy of an idle communication module.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.3751-3774
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• 2014

With the rapid development of wireless communication, the confliction between the scarce frequency resources and the low spectral efficiency caused by the stationary spectrum sharing strategies seriously restricts the evolution of the future mobile communication. For this purpose, cognitive radio (CR) emerges as one of the most promising inventions which can overcome the spectrum shortage. As the key technology and main objective of CR, spectrum sharing can make full use of the limited spectrum, alleviate the scarcity of frequency resources and improve the system utilities, playing thereby an important role in improving the system performance of cognitive radio networks (CRNs). In this survey, the spectrum sharing in CRNs is discussed in terms of the sharing process, mainstream sharing technologies and spectrum sharing models. In particular, comparisons of different spectrum sharing strategies are concluded, as well as that of different spectrum sensing schemes in sharing procedure. Moreover, some application examples of the spectrum sharing in CRNs, such as smart grid, public safety, cellular network and medical body area networks are also introduced. In addition, our previous related works are presented and the open research issues in the field of spectrum sharing are stated as well.

• 한국인터넷방송통신학회논문지
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• 제13권6호
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• pp.17-22
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• 2013

무전기간의 음성교신을 위해서는 동일한 무선 주파수와 통신 프로토콜을 사용해야 하나 재난관리기관에서는 용도와 목적 등 여러 가지 이유로 다양한 무전기를 사용하고 있다. 이에 이종의 무전기간의 음성을 연계하는 여러 가지 방안들이 연구되어 왔으나 단순한 아날로그 음성라인 연결 방식이나 디지털 기반의 부분 네트워크 연결 방식이었다. 이에 본 논문에서는 확장성과 표준 개방성을 위해 SIP/RTP를 이용하여 IP 네트워크를 통해 전송하는 무전기별 All-IP 기반의 음성패킷 전달 방안을 제시하고 이를 시제품으로 개발하여 검증하였다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.45-50
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• 2005

This paper make an analysis of UWB Communication System. In case endoscope, medical equipment, is applied to UWB, We could study through body-channel that frequency transmitted of received signal is differ from wireless in the existing air. It suggested TR-UWB form, non-coherent received method in dispersion-medium like humans bodies by accomplishing ability analysis of BPM, TR, BER of Differential, UWB Communication modulation and demodulation form.

• 천문학논총
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• 제15권1호
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• pp.35-60
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• 2000

We have analyzed the frequency sharing in the range of 71-275 GHz, which was adopted as a main topic of the WARC-2000 at the previous conference WARC-97. Though the technology of the active services has not been fully developed in this frequncy range, the heavy usage of this technology is expected in foreseeable future. To protect the passive services from spurious and out-of-band emissions of active services, realignment of the spectrum between 71 GHz and 275 GHz is strongly required. In addition, some effort should be made to allocate special bands for the radio astronomy service.

• 한국전자통신학회논문지
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• 제8권6호
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• pp.923-931
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• 2013

RFID(Radio Frequency Identification)는 버스카드, 출입문 카드, 물류유통, 건축자재 관리 등 일상생활에서 다양하게 사용되는 태그의 일종으로 ID정보를 무선 주파수(RF, Radio Frequency)를 사용하여 인식하는 무선인식장치이다. RFID는 투과성과 인식률, 메모리 크기, 다중태그 인식률, 외부 오염 먼지, 외부 충격 등에 따라 크기와 성능이 달라지고, 이와 같은 요소들을 고려한 RFID 보호를 위한 패키징이 필요하다. 현재 RFID는 건축자재의 효과적인 관리를 위해서도 다양하게 사용되고 있는데, 건축자재에 RFID를 부착하기 위해서는 외부로 부터의 충격에 강건한 건축자재용 RFID 패키징 제작이 요구되고 있다. 본 논문에서는 외부 충격에 강하고, 고장 시 RFID의 교체가 가능하도록 패키징 틀과 본체를 분리하여 설계된 건축자재용 RFID 패키징을 제안한다. 제안된 RFID 패키징을 위한 상세한 설계도를 제시하였으며, 3D 프린터를 사용하여 설계된 패키징을 직접 제작하여 성능 평가를 실시하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1294-1302
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• 2008

Talk-Back systems comprised of master-equipment at the control room and slave-equipment at turnouts refer to the intercommunication facilities that optimize mutual communication between maintenance staff on trackside and the control room to facilitate quickness and accuracy of train operation control and its maintenance within depot and on mainlines with turnouts for direction switching of the trains in operation. The weakness lies in additional maintenance costs of cables since the Talk-Back system installed on line 1 along with line 2-4 has a profound effect on the voice quality leading to the attenuation and crosstalk of the system due to the deterioration of cables and environmental factors. This paper discusses the Talk-Back system in a radio communication environment with the application of RF(Radio Frequency) communication system from the wire communication system by cables to ameliorate these problems, and deals with the energy saving environmentally friendly facilities in consideration of replacing power section at salve-equipment with solar batteries benefitting the system in light of energy consumption.

• Journal of information and communication convergence engineering
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• 제9권1호
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• pp.27-31
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• 2011

This paper describes the optimization of spectrum sensing in terms of the throughput of a cognitive radio (CR) system. Dealing with the optimization problem of spectrum sensing, this paper evaluates the throughput of a CR system by considering such situations as the penalty time of a channel search and incumbent user (IU) detection delay caused by a missed detection of an incumbent signal. Also, this paper suggests a serial channel search scheme as the search method for a vacant channel, and derives its mean channel search time by considering the penalty time due to the false alarm of a vacant channel search. The numerical results suggest the optimum sensing time of the channel search process using the derived mean channel search time of a serial channel search in the case of a sensing hardware structure with single radio frequency (RF) path. It also demonstrates that the average throughput is improved by two separate RF paths in spite of the hardware complexity of an RF receiver.