• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.3638-3654
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• 2014

Cognitive Radio (CR) users need to sense the environment or channel at regular time interval for sharing the spectrum band of the primary users (PUs). Once find the spectrum idle, CR users start their transmission through it. Even while transmitting, they need to continue the sensing process so that they can leave the spectrum immediately whenever find a PU wanting to use the band. Therefore, detecting PUs is one of the main functions of cognitive radio before transmission and higher the detection probability ensures better protection to the primary users. However, it is not possible to attain a high detection probability (or a low miss detection probability) and low false alarm probability simultaneously as there is a tradeoff between false alarm probability ($P_{fa}$) and the probability of detection ($P_d$). In this paper, the author has provided a comprehensive study on different sensing techniques and discussed their advantages and disadvantages. Moreover, it is expected that, with this article, readers can have a through understanding of sensing techniques in CR and the current research trends in this area.

• Genomics & Informatics
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• 제6권3호
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• pp.130-135
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• 2008

The haplotypes of a 200 kb region in the human chromosome X terminal band (q28) were analyzed using the International HapMap Project Phasell data, which had been collected for three analysis panels (YRI, CEU, and CHB＋JPT). When multiple linkage disequilibrium blocks were encountered for a panel, the neighboring haplotypes that had crossover rate of 5% or more in the panel were combined to generate 'haploid' configurations. This resulted in 8, 7, and 5 'haploid' configurations for the panels of YRI, CEU, and CHB＋JPT, respectively. The multiple sequence alignment of these 'haploids' was used for the calculation of allele-sharing distances and the subsequent principal coordinate analysis. Two 'haploids' in CEU and CHB＋JPT were hypothesized as 'parental' in light of the observations that the successive recombinants of these haploids can model two other haploids in CEU and CHB＋JPT, and that their configurations were consistent with those in YRI. This study demonstrates the utility of haplotype phylogeny in understanding population evolution.

• Journal of electromagnetic engineering and science
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• 제6권1호
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• pp.76-81
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• 2006

Ultra wideband(UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geo-location, 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 wireless systems sharing the frequency bands such as Broadcasting system. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a orthogonal frequency division Multiplex UWB source and an impulse radio UWB source, to a Broadcasting transmission system. The receive power degradations of broadcasting system are presented. From these experimental results, we show that in all practical cases UWB system can coexist 35 m distance in-band broadcasting network.

• 전자통신동향분석
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• 제34권3호
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• pp.65-74
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• 2019

The Earth Stations in Motion (ESIM) system is one of the most modern satellite systems, providing high-speed and high-capacity communication with mobility. To facilitate ESIM in the Ka band, operational, technical, and regulatory studies have been conducted in the International Telecommunication Union Radiocommunication Sector (ITU-R) since 2016. In this paper, we introduce the ESIM and discuss its system characteristics and frequency sharing issues with respect to existing services in the same frequency bands. Taking into account current standardization activity in the ITU-R, we provide the latest study results of ESIM operation based on the Conference Preparatory Meeting Report for the World Radiocommunication Conference-19.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2006년도 하계종합학술발표회 논문 초록집
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• pp.385-385
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• 2006

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1060-1068
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• 2018

Droop control schemes have been widely employed in the control strategies for Multi-Terminal Direct Current (MTDC) system for its high reliability. Under the conventional DC voltage-active power droop control, the droop slope applies a proportional relationship between DC voltage error and active power error for power sharing. Due to the existence of DC network impedance and renewable resource fluctuation, there is inevitably a DC voltage deviation from the droop characteristic, which in turn results in inaccurate control of converter's power. To tackle this issue, a piecewise droop control with DC voltage dead band or active power dead band is implemented into controller design. Besides, an advanced droop control scheme with versatile function is proposed, which enables the converter to regulate DC voltage and AC voltage, control active and reactive power, get participated into frequency control, and feed passive network. The effectiveness of the proposed control method has been verified by simulation results.

• Asian-Australasian Journal of Animal Sciences
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• 제17권9호
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• pp.1204-1209
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• 2004

Random amplification of polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) analysis was carried out using DNA samples of 30 animals of Rathi cattle and 42 animals of Tharparkar cattle. Genomic DNA was isolated as per standard protocol and evaluated for its quality, purity and concentration. Twenty three random primers were screened out of which 15 primers yielded satisfactory amplifications and were used for further analysis. Average numbers of polymorphic fragments per primer were 7.07${\pm}$0.86 in Rathi and 6.80${\pm}$0.61 in Tharparkar cattle. The percentage of polymorphic bands in these two cattle breeds were 86 and 87%, respectively. Within breed genetic similarities for pooled over primers in the animals of Rathi and Tharparkar breeds were .577${\pm}$0.30 and 0.531${\pm}$0.02, respectively on the basis of band frequency (BF) and 0.645${\pm}$0.04 and 0.534${\pm}$0.04, respectively on the basis of band sharing (BS). Averages of between breed genetic similarities for pooled over primers were 0.97 and 0.92 according to BF and BS, respectively, which reflect higher degree of genetic similarity between Rathi and Tharparkar cattle breeds. Index of genetic distance based on BF and BS for pooled over primers was 0.030${\pm}$0.011 and 0.088${\pm}$0.031, respectively. Percentage of polymorphic bands and within-breed genetic similarities on the basis of band frequency (BF) and band sharing (BS) for pooled over primers revealed higher genetic similarity in Rathi than Tharparkar cattle population. High estimates of between breed genetic similarities for pooled over primers indicated that either Rathi is having decent from Tharparkar or both the cattle breeds are having common descent. Low value of Index of genetic distances between these two cattle breeds may be due to the fact that Rathi and Tharparkar cattle breeds are the native of Thar Desert in Northwest India. The results of between breed genetic distances also confirm the existence of high degree of genetic similarity between these two breeds of cattle.

• 한국전자통신학회논문지
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• 제10권12호
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• pp.1315-1320
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• 2015

본 논문은 군통신 데이터링크 장비에 대해서 주파수 자원을 효율적으로 이용하기 위하여 고속도약기법, 주파수환경센싱기법, 수신2채널기법, 수신필터뱅크부 적용 등을 이용하여 동일한 주파수 대역을 사용하는 레이다 등의 타장비와 공유할 수 있는 기법을 소개한다. 사전에 운용대역의 주파수 환경을 실시간 측정 및 분석하였고, 일차적으로 개발하려는 장비가 기존 운용하고 있는 레이다에 간섭영향성이 최소화하는 방법을 분석하였으며, 반대로 레이다가 간섭을 주는 환경에서 본 논문에서 제시한 주파수 공유기법을 사용하여 최대한 통신확률을 높이는 구조를 제시한다. 최종적으로 설계된 RF송수신기의 잡음지수, 상호혼변조(IMD)와 같은 주요 규격에 대한 모의실험을 통하여 만족여부를 사전 검증하였다.

• 한국위성정보통신학회논문지
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• 제8권4호
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• pp.58-63
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• 2013

무선통신 시스템 간의 주파수 간섭은 시스템의 성능을 감소시키거나 운용을 제한할 수 있으므로 신규 시스템의 도입 이전에 기존 시스템들과의 주파수 양립성 평가가 반드시 수행되어야 한다. 본 논문에서는 1.6 GHz 대역 무선항행위성업무 시스템의 인접대역에서 신규 이동통신업무 시스템을 운용하기 위한 양립성 평가 알고리즘을 제시하였으며, 동일 지역 내에서 운용되는 이동통신업무시스템과 무선항행위성업무 시스템 상호 간의 최소결합손실 (Minimum Coupling Loss; MCL) 분석 결과로부터 두 시스템 간의 주파수 공유를 위한 조건을 도출하였다.

• 한국인터넷방송통신학회논문지
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• 제11권5호
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• pp.179-184
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• 2011

본 논문에서는 인접채널에서 다른 통신 시스템이 공존할 수 있는 방안으로 공유 파라미터를 분석하였다. 이 기종 시스템에서 간섭 송신기의 다양한 밀도와 전송출력에 따른 성능 결과를 분석하였다. 두 시스템간의 간섭밀도와 허용 최대 송신출력의 관계를 분석하기 위해 간섭 송신기가 WiBro이고 WLAN이 희생 수신기인 경우를 고려하였다. WLAN의 중심주파수가 687MHz이고 간섭원 밀도가 50개/$km^2$ 인 경우 요구되는 보호대역은 10MHz 이었다. 분석된 상호 공존 결과는 향후 동일 주파수 환경에서 다양한 통신 프로토콜을 이용하는 무선기기에 대한 상호 공존 조건을 마련하는 기술개발에 활용할 수 있을 것이다.