• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권9호
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• pp.2081-2100
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• 2013

In this paper, we propose a cooperative hybrid spectrum sharing protocol by jointly considering interweave (opportunistic) and underlay schemes. In the proposed protocol, secondary users can access the licensed spectrum along with the primary system. Our network scenario comprises a single primary transmitter-receiver (PTx-PRx) pair and a group of M secondary transmitter-receiver (STx-SRx) pairs within the transmission range of the primary system. Secondary transmitters are divided into two groups: active and inactive. A secondary transmitter that gets an opportunity to access the secondary spectrum is called "active". One of the idle or inactive secondary transmitters that achieves the primary request target rate $R_{PT}$ will be selected as a best decode-and-forward (DF) relay (Re) to forward the primary information when the data rate of the direct link between PTx and PRx falls below $R_{PT}$. We investigate the ergodic capacity and outage probability of the primary system with cooperative relaying and outage probability of the secondary system. Our theoretical and simulation results show that both the primary and secondary systems are able to achieve performance improvement in terms of outage probability. It is also shown that ergodic capacity and outage probability improve when the active secondary transmitter is located farther away from the PRx.

• Journal of Communications and Networks
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• 제16권2호
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• pp.130-139
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• 2014

Due to the unpredictable nature of channel availability, carrying delay-sensitive traffic in cognitive radio networks (CRNs) is very challenging. Spectrum leasing of radio resources has been proposed in the so called coordinated CRNs to improve the quality of service (QoS) experienced by secondary users (SUs). In this paper, the performance of coordinated CRNs under fixed-rate with hard-delay-constraints traffic is analyzed. For the adequate and fair performance comparison, call admission control strategies with fractional channel reservation to prioritize ongoing secondary calls over new ones are considered. Maximum Erlang capacity is obtained by optimizing the number of reserved channels. Numerical results reveal that system performance strongly depends on the value of the mean secondary service time relative to the mean primary service time. Additionally, numerical results show that, in CRNs without spectrum leasing, there exists a critical utilization factor of the primary resources from which it is not longer possible to guarantee the required QoS of SUs and, therefore, services with hard delay constraints cannot be even supported in CRNs. Thus, spectrum leasing can be essential for CRN operators to provide the QoS demanded by fixed-rate applications with hard delay constraints. Finally, the cost per capacity Erlang as function of both the utilization factor of the primary resources and the maximum allowed number of simultaneously rented channels is evaluated.

• 한국방재학회 논문집
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• 제6권3호
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• pp.29-35
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• 2006

교량의 지진응답해석시 단면의 비선형 거동특성에 따른 휨변형을 정밀하게 구현하기 위해 섬유요소를 이용한 해석이 수행되었다. 2주형 다주교각을 섬유요소로 모델링하여 지진하중에 대한 비선형 정적해석을 수행하였으며 소성힌지 영역에서의 파괴 메카니즘을 분석하였다. 비선형 정적해석으로 얻어진 하중-변위 곡선을 이용하여 역량스펙트럼 방법에 의한 지진응답해석을 수행되었다. 또한 교량 전체 시스템을 섬유요소를 이용하여 모델링하고 동일한 응답스펙트럼을 가지는 지진파를 입력하여 비선형 시간이력 해석을 수행되었으며 이는 역량스펙트럼 방법과 유사한 결과를 보인다.

• Journal of the Optical Society of Korea
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• 제7권4호
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• pp.249-252
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• 2003

A simple multi-channel spectrum analyzer using an InGaAs array sensor and a diffraction grating is proposed and developed for high-capacity optical transport networks. With the developed multichannel spectrum analyzer, we could measure signal power, wavelength, and optical signal-to-noise ratio of each channel for multi-channel optical signals with 100 GHz and 50 GHz channel spacing, simultaneously. We could measure each channel power and wavelength with a deviation of less than 0.2 dB and 0.063 nm, respectively. We have obtained optical signal-to-noise ratio with a deviation of less than 1.0 dB compared with conventional optical spectrum analyzer in the wide input power range between -42 dBm and -27 dBm per channel.

• 전기학회논문지
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• 제62권12호
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• pp.1755-1757
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• 2013

Dynamically exploiting unused-spectrum, cognitive radio has been proposed to solve spectrum utilization problem. In cognitive radio, it is important to minimize the interference to primary service as well as to provide efficient channel allocation. In this paper, we propose a multi-channel allocation scheme based on spectrum hole prediction. Proposed scheme considered both interference length and channel capacity to limit the interference to primary user as well as to enhance system performance. Simulation results show the proposed scheme improves the system throughput.

• 한국인터넷방송통신학회논문지
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• 제10권2호
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• pp.39-44
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• 2010

본 논문에서는 디지털 워터마킹 기법을 이용하여 부가데이터를 전송하기 위해 일반화된 K 페이딩 채널에서의 채널용량 수식을 유도하였다. 대역확산 워터마킹 기법(Spread Spectrum Watermarking: SSW)은 디지털 워터마킹 기법 중의 하나로 무선 채널에서 잡음에 대해 강인한 특성을 지니며, 수신단에서의 신호 검출이 상관기에 의해 간단히 이루어지기 때문에 널리 사용되는 방식이다. 대역확산 워터마킹 기법에 의해 생성된 부가데이터를 무선통신 시스템에 적용하기 위해서는 워터마킹 신호가 무선 채널에 의해 받는 영향에 대한 연구가 필수적으로 요구된다. 모의실험 결과로부터 대역확산 워터마킹 시스템의 채널용량이 HWR, WNR, fx, 그리고 PN 시퀀스의 길이에 따라 변화함을 확인하였고, 또한 적정 데이터를 전송하기 위하여 필요한 HWR과 WNR의 레벨을 수식으로부터 결정할 수 있음을 보였다. 본 논문의 결과는 PN 시퀀스를 이용하는 일반적인 대역확산 워터마킹 시스템에 적용할 수 있다.

• Journal of Communications and Networks
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• 제11권4호
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• pp.368-374
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• 2009

This paper focuses on a distributed multiple spectrum pricing scheme to maximize system capacity in next generation multiaccess systems, where multimode user equipments (MUEs) can connect simultaneously to multiple base stations (BSs) with multiple radio access technologies (RATs). The multi-price based scheme provides a distributed decision making for an optimal solution where radio resource allocations are determined by each MUE, unlike most centralized mechanisms where BS controls the whole radio resource. By the proposed optimal solution, MUEs can decide their share of spectrum bands and power allocation according to the spectrum price of each RAT, and at the same time the multiaccess system can achieve maximized total throughput. Numerical analysis shows that the proposed scheme achieves the maximal capacity by distributed resource allocation for the multiaccess system.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.65-70
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• 2008

The capacity spectrum method (CSM) is a deterministic seismic analysis approach wherein the expected seismic response of a structure is established as the intersection of the demand and capacity curves. Recently, there are a few studies about a probabilistic CSM where uncertainties in design factors such as material properties, loads, and ground motion are being considered. However, researches show that soil-structure interaction also affects the seismic responses of structures. Thus, their uncertainties should also be taken into account. Therefore, this paper presents a probabilistic approach of using the CSM for seismic analysis considering uncertainties in soil properties. For application, a reinforced concrete bridge column structure is employed as a test model. Considering the randomness of the various design parameters, the structure's probability of failure is obtained. Monte Carlo importance sampling is used as the tool to assess the structure's reliability when subjected to earthquakes. In this study, probabilistic CSM with and without consideration of soil uncertainties are compared and analyzed. Results show that the analysis considering soil structure interaction yields to a greater probability of failure, and thus can lead to a more conservative structural design.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.260-267
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• 2001

In this study straightforward design procedure for unbond brace hysteretic dampers is developed. The required amount of equivalent damping to satisfy given performance acceptance criteria is obtained conveniently based on the capacity spectrum method without carrying out time-consuming nonlinear dynamic time history analysis. Then the size of the unbend braces is determined from the required equivalent damping. Parametric study is performed for the design variables such as natural period, yield strength, the stiffness after the first yield, yield stress of the unbond brace.

• 한국통신학회논문지
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• 제13권6호
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• pp.453-460
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• 1988

동기식 대역확산 다중출입 통신의 오류 확률을 특성함수를 이용하여 구했으며 변조 방식으로는 PSK가 사용되었다. 채널용량을 이용하여 성능을 분석하였고 신뢰성 있는 통신을 위한 최소 비트 신호대 잡음비를 계산하였다.