• Journal of electromagnetic engineering and science
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• 제11권4호
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• pp.250-256
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• 2011

This paper applies a compressed algorithm to improve the spectrum sensing performance of cognitive radio technology. At the fusion center, the recovery error in the analog to information converter (AIC) when reconstructing the transmit signal from the received time-discrete signal causes degradation of the detection performance. Therefore, we propose a subspace pursuit (SP) algorithm to reduce the recovery error and thereby enhance the detection performance. In this study, we employ a wide-band, low SNR, distributed compressed sensing regime to analyze and evaluate the proposed approach. Simulations are provided to demonstrate the performance of the proposed algorithm.

• Journal of electromagnetic engineering and science
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• 제12권2호
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• pp.148-154
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• 2012

In this paper, we propose an algorithm to conserve resources of the common control channel in a cognitive radio network by rejecting the redundant users using cooperative spectrum sensing. The proposed scheme is investigated under the paradigm of active spectrum sensing and a sequential detection technique. The algorithm is based on the J-divergence between the hypotheses of non primary user operation and the otherwise case. We select the most significant eigenvalues, which primarily affect the global statistical test. For the case where interference is from a secondary system transmission, a match filter is first employed to remove the degradation, and then the proposed algorithm is employed to remove the cooperative sensing nodes. Numerical results are provided and compared with conventional cases in order to validate the performance of the proposed algorithm.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1332-1333
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• 2003

• 전기전자학회논문지
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• 제5권2호
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• pp.182-189
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• 2001

Single-pass VDD 심장 박동기(pacemaker)는 하나의 리드만 이식하는 수술 과정의 단순함과 하나의 리드만으로 심방 탈분극파를 적절히 검출하여 심방-심실 탈분극의 연속성(A-V sequence)을 이를 수 있다는 이유로 널리 사용되고 있으나, 검출의 신뢰도에 대해서는 여전히 논의의 대상이 되고 있다. 본 논문에서는 논의의 대상이 되고 있는 심방 탈분극파 검출을 개선하기 위하여 자동화된 심장 박동기 심파 검출 알고리즘을 9명의 환자로부터 얻은 Single-pass VDD 심파에 적용하고, 실제 심파 검출과정에서의 동작 특성을 관찰하였다. 자동화된 검출 알고리즘은 최근에 검출된 두 개의 intrinsic 탈분극파 진폭의 평균치를 계산하여 그 평균치의 50%로 검출 문턱치를 매 박동마다 조정하는 매우 단순한 방법으로, 자동화된 검출 알고리즘의 핵심인 문턱 전압 검출치의 자동적 조정만으로도 Single-pass VDD 심방 탈분극파 검출을 개선할 수 있음을 확인하였다.

• 대한원격탐사학회지
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• 제24권5호
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• pp.427-436
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• 2008

This paper presents radar remote sensing of soil moisture and surface roughness for vegetated surfaces. A precise volume scattering model for a vegetated surface is derived based on the first-order radiative transfer technique. At first, the scattering mechanisms of the scattering model are analyzed for various conditions of the vegetation canopies. Then, the scattering model is simplified step by step for developing an appropriate inversion algorithm. For verifying the scattering model and the inversion algorithm, the polarimetric backscattering coefficients at 1.85 GHz, as well as the ground truth data, of a tall-grass field are measured for various soil moisture conditions. The genetic algorithm is employed in the inversion algorithm for retrieving soil moisture and surface roughness from the radar measurements. It is found that the scattering model agrees quite well with the measurements. It is also found that the retrieved soil moisture and surface roughness parameters agree well with the field-measured ground truth data.

• Journal of Communications and Networks
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• 제11권2호
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• pp.115-121
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• 2009

In cognitive radio (CR) systems, cognitive users can use the frequency bands when the primary users are not present. Hence, reliable detection of available spectrum is foundation of cognitive radio technology. To ensure unimpaired operation of primary users, cooperative spectrum sensing is needed. To reduce the network overhead of cooperative spectrum sensing, a novel cooperative spectrum sensing algorithm based on credibility is proposed. In particular, the close-form expressions for probability of detection and false-alarm are derived for the novel algorithm, and expression for the average overhead used for cooperation is given. The thresholds design method for the algorithm is also discussed. The conclusion is proved by computer simulations.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.224-227
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• 2004

From 1980's, the DWT(Discrete Wavelet Transform) is applied to the data/image processing. Many people use the DWT in remote sensing for diversity purposes and they are satisfied with the wavelet theory. Though the algorithm for wavelet is very diverse, many people use the standard wavelet such as Daubechies D4 wavelet and biorthogonal 9/7 wavelet. We will overview the wavelet theory for discrete form which can be applied to the image processing. First, we will introduce the basic DWT algorithm and review the wavelet algorithm: EZW (Embedded Zerotree Wavelet), SPIHT(Set Partitioning in Hierarchical Trees), Lifting scheme, Curvelet, etc. Finally, we will suggest the properties of wavelet algorithm; and wavelet filter for each image processing in remote sensing.

• ETRI Journal
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• 제38권1호
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• pp.30-40
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• 2016

Co-channel interference between macro-femtocell networks is an unresolved problem, due to the frequency reuse phenomenon. To mitigate such interference, a secondary femtocell must acquire channel-state knowledge about a co-channel macrocell user and accordingly condition the maximum transmit power of femtocell user. This paper proposes a pilot-based spectrum sensing (PSS) algorithm for overlaid femtocell networks to sense the presence of a macrocell user over a channel of interest. The PSS algorithm senses the pilot tones in the received signal through the power level and the correlation metric comparisons between the received signal and the local reference pilots. On ensuring the existence of a co-channel macrocell user, the maximum transmit power of the corresponding femtocell user is optimized so as to avoid interference. Time and frequency offsets are carefully handled in our proposal. Simulation results show that the PSS algorithm outperforms existing sensing techniques, even at poor received signal quality. It requires less sensing time and provides better detection probability over existing techniques.

• 한국컴퓨터정보학회논문지
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• 제20권11호
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• pp.63-68
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• 2015

In this paper, we propose a new energy efficient scheme which can prolong the life of sensor networks, it should be able to reduce the number of sensing. We use the concept of safe zone for manage the appropriate range of properties. We measure the distance between the sensed temperature value and the center of the zone, and calculate the next sensing interval based on this distance. We name our proposed scheme "VIS". To assess the performance of the proposed scheme the actual temperature data was collected using the sensor node. The algorithm was implemented through the programming and was evaluated in a variety of settings. Experimental results show that the proposed algorithm is to significantly reduce the number of sensing in terms of energy efficiency while having the ability to know the state of the sensor nodes periodically. Our VIS algorithm can be useful in applications which will require the ability of control to the temperature within a proper range.

• Journal of Information Processing Systems
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• 제15권2호
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• pp.410-421
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• 2019

Distributed compressed sensing (DCS) states that we can recover the sparse signals from very few linear measurements. Various studies about DCS have been carried out recently. In many practical applications, there is no prior information except for standard sparsity on signals. The typical example is the sparse signals have block-sparse structures whose non-zero coefficients occurring in clusters, while the cluster pattern is usually unavailable as the prior information. To discuss this issue, a new algorithm, called backtracking-based adaptive orthogonal matching pursuit for block distributed compressed sensing (DCSBBAOMP), is proposed. In contrast to existing block methods which consider the single-channel signal reconstruction, the DCSBBAOMP resorts to the multi-channel signals reconstruction. Moreover, this algorithm is an iterative approach, which consists of forward selection and backward removal stages in each iteration. An advantage of this method is that perfect reconstruction performance can be achieved without prior information on the block-sparsity structure. Numerical experiments are provided to illustrate the desirable performance of the proposed method.