• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.423-429
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• 2011

Cooperative spectrum sensing is proposed to overcome some problem such as multipath fading and shadowing and to improve spectrum sensing performance. There are different combining methods for cooperative spectrum sensing: hard decision method and soft decision method. In this paper, we analysis the performance of cooperative spectrum sensing with distance based weight that is kind of a soft decision rule for cognitive radio(CR) systems and CR systems sense the spectrum of the licensed user by using a energy detection method. Threshold is determined in accordance with the constant false alarm rate(CFAR) algorithm for energy detection. The signal of licensed user is OFDM signal and the wireless channel between a licensed user and CR systems is modeled as Gaussian channel. From the simulation results, the cooperative spectrum sensing with distance based weight combining(DWC) and equal gain combing(EGC) methods shows higher spectrum sensing performance than single spectrum sensing does. And the detection probability performance with the DWC is higher than that with the EGC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7B
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• pp.538-549
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• 2008

Recently IEEE 802.22 WG has considered Cognitive Radio (CR) technology to overcome shortage of communication channels. For using CR technology, accurate and rapid sensing method selection is extremely important. According to the channel sensing method, it is of the utmost importance because it can affect the incumbent system protection. So, optimum selection of channel sensing method is very important. IEEE 802.22 gives the solution, name of fine sensing, but the solution can not adapt to various networks. So in this paper we propose Policy-based Channel Sensing Architecture and Algorithms for Cognitive Radio Networks. The proposed channel sensing architecture and algorithms can reduce both primary system detection time and quiet time in our simulation. Among the proposed sensing algorithm, channel division round robin sensing reduce average detection time up to 70% compare to fine sensing method in IEEE 802.22.

• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.91-97
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• 2014

In this paper, we propose weighted detection probability with distance between primary user and secondary users by using cooperative spectrum sensing based on energy detection. And we analysis and simulate the result. We suggest different distance between primary user and secondary users and the wireless channel between primary user and secondary users is modeled as Gaussian channel. From the simulation results of the cooperative spectrum sensing with weighted method make coverage bigger compared with non-weight, and We show higher sensing efficiency when we put weight detection probability than before method.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.344-348
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• 2009

Cognitive Radio(CR)는 특정 주파수 대역을 사용하도록 할당된 유저가 사용하지 않을 때, 이를 탐지하여 해당 주파수 대역을 이용함으로써 주파수 스펙트럼 효율을 향상시킬 수 있는 기술이다. 특히, CR에서 스펙트럼 센싱(Spectrum Sensing)은 중요한 기술의 하나라고 말할 수 있다. 기존의 스펙트럼 센싱 성능을 향상시키기 위한 방법으로, 다수의 노드가 각각 판정한 결과를 이용하는 OR-Rule, AND-Rule 등의 기법이 제안된 바 있다. 본 논문에서는 수신 다이버시티 기법 중의 하나인 Equal Gain Combiner(EGC) 알고리듬 이용하여 스펙트럼 센싱 성능을 알아보고 특히, 기존의 방법은 각 노드에서 판정 후 판정부에서 그 결과를 결합하여 최종 판정하는 방법이나, 본 논문에서 적용한 EGC 기법은 각 노드에서 수신된 신호에 대한 검출된 에너지 값을 융합센터(Fusion Center)로 보내어 최종 판정하는 방법이다. 각 노드에서 검출된 에너지 값을 융합센터가 수신한 신호에는 실질적으로 잡음이 섞이게 되므로 이로 인하여 발생할 수 있는 전송 오류를 추가적으로 고려하였다. 또한, 각 노드에서 검출한 에너지 값이 융합센터로 전송될 때에는 양자화 되어서 전송된다. 이에 따라서 양자화 bit수와 관련된 센싱 성능과 데이터의 반복 전송의 필요성, 그리고 그 횟수에 대해 제시하고자 한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.37-43
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• 2012

In this paper, we analysis wideband spectrum sensing with distance based weight combining for Cognitive Radio (CR) systems. CR systems is implemented the spectrum of the Primary User(PU) by using a energy detection method. Threshold is determined in accordance with the constant false alarm rate (CFAR) algorithm for energy detection. The signal of PU is BPSK signal and the wireless channel between a PU and CR systems is modeled as Gaussian channel. From the simulation results, the wideband sensing with distance based and Distance based weight Combing (DWC) methods shows higher spectrum sensing performance than single CR user spectrum sensing.

• Management & Information Systems Review
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• v.34 no.2
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• pp.79-95
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• 2015

The purpose of this paper is to evaluate the effects of perceived risk and brand attitude on licensing brands comparing with non-licensed brands(virtual brand). Data was collected through a self-administered questionnaire in quasi-experimental design setting. I designed the experimental setting that there were two virtual companies to sell the luxury bags(symbolic goods) or cruise tour(experiential goods) and to launch their goods with own brand or licensed brand. The experimental groups were composed of women consumers who were familiar with consuming experiential goods and symbolic goods. Results from the experiment suggest that consumer's perceived risk on brands gives a negative impact on brand attitude. And congruence in goods types and licensed brand values leads to difference in the level of perceived risk. In experiential goods, brand licensing from famous and experiential brands can reduce perceived risk. But in symbolic goods, brand licensing effect which reduces the perceived risk is less effective than in experiential goods. This findings suggest that brand licensing may lower the level of consumer's perceived risk, but incongruity in goods type and brand value may result in strategic failure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8C
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• pp.655-662
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• 2012

In this work, we propose an airborne cognitive radio system that searches a new spectrum band to avoid a communication interruption due to the interference from many radar signals. We develop a method of fast spectrum sensing based on an effective frequency by recognizing the interfering radar as well as geographical information. This effective frequency is calculated by the free-space path loss between a base station and a fighter with the speed parameter. From our analysis, it is verified that the maximum frequency searching time is reduced by half by using our method.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.2
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• pp.1-8
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• 2012

We propose a new frame length control scheme for cognitive radio systems. In the proposed algorithm, the property that the probability of a primary packet arrival continually increases as time elapses during the primary user's idle period is utilized. When reducing the secondary frame length in accordance with the increasing primary packet arrival probability, spectrum sensing is conducted more frequently as time elapses and the primary packet arrival is detected more quickly. We obtain the optimal frame lengths by maximizing the secondary throughput while satisfying the interference constraint. Numerical results show a significant throughput enhancement via the frame length control.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.5-11
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• 2006

Cognitive radio, which is designed to dynamically adapt its transmission to its environments is believed to be one of the fundamental techniques for the future spectrum utilization. As the first step of cognitive radio, spectrum sensing is treated as the most important technique. In this paper, we propose a spectral correlation based detection method for spectrum sensing. Based on the cyclostationarity of communication signals, spectral correlation function is used to minimize the effect of random noise and interference. The ROC performance of conventional energy detection is shown. Simulation result show that the proposed detection method outperforms the energy detection and more suitable for spectrum sensing in cognitive radios.

• Information and Communications Magazine
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• v.34 no.5
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• pp.27-35
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• 2017

자율 주행 자동차에 있어서 기능 안전을 위해서 필요한 다양한 고려 사항과 필수 센서인 모바일 라이다 센서에 대하여 분석한다. ISO 26262는 인간이 운전할 경우 기능적인 안전을 보장할 수 있는 신뢰를 제공하는 기능 안전 표준으로서, 자율 주행 자동차가 운전자의 개입없이 주변의 상황을 파악하고 인지한 후 스스로 판단하여 동작하는 경우 정확하게 수행되었다는 것을 판단하기가 어렵다. 자율 주행 자동차는 주변 환경 센싱, 처리 및 판단, 동작 수행의 과정을 거쳐서 자율 주행을 수행한다. 이 중에서 주변 환경 센싱과 동작 수행의 경우 기존의 자동차 기능 안전을 개선하여 적용이 가능할 것이다. 본고에서는 자율 주행 자동차에 대한 기능 안전의 상관성과 자율 주행 자동차가 주변 환경 센싱에 필수적으로 사용하는 모바일 라이다가 사용하는 다양한 기술들에 대하여 알아본다.