• ETRI Journal
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• 제38권1호
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• pp.141-148
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• 2016

This paper proposes a method to estimate directly the incoherent scattered intensity and radar cross section (RCS) from the effective permittivity of a random media. The proposed method is derived from the original concept of incoherent scattering. The incoherent scattered field is expressed as a simple formula. Therefore, to reduce computation time, the proposed method can estimate the incoherent scattered intensity and RCS of a random media. To verify the potential of the proposed method for the desired applications, we conducted a Monte-Carlo analysis using the method of moments; we characterized the accuracy of the proposed method using the normalized mean square error (NMSE). In addition, several medium parameters, such as the density of scatterers and analysis volume, were studied to understand their effect on the scattering characteristics of a random media. The results of the Monte-Carlo analysis show good agreement with those of the proposed method, and the NMSE values of the proposed method and Monte-Carlo analysis are relatively small at less than 0.05.

• ETRI Journal
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• 제35권1호
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• pp.69-79
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• 2013

For real-time interactive multimedia operations, such as video uploading, video play, fast-forward, and fast-rewind, solid state disk (SSD)-based storage systems for video streaming servers are becoming more important. Random access rates in storage systems increase significantly with the number of users; it is thus difficult to simultaneously serve many users with HDD-based storage systems, which have low random access performance. Because there is no mechanical operation in NAND flash-based SSDs, they outperform HDDs in terms of flexible random access operation. In addition, due to the multichannel architecture of SSDs, they perform similarly to HDDs in terms of sequential access. In this paper, we propose a new SSD-based storage system for interactive media servers. Based on the proposed method, it is possible to maximize the channel utilization of the SSD's multichannel architecture. Accordingly, we can improve the performance of SSD-based storage systems for interactive media operations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.321-323
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• 2006

The IEEE 802.15.4 uses a CSMA/CA algorithm on access of media. The CSMA/CA algorithm does Random Backoff before the data is transmitted to avoid collisions. The random backoff is a kind of unavoidable delays and introduces the side effect of energy consumptions. To cope with those problems we propose a new media access algorithm, the Priority Based Ordered Media Access (PBOMA) algorithm, which uses different IFSs. The PBOMA algorithm uses Sampling Rate and Beacon Interval to get a different access probability(or IFS). The access probability is higher, the IFS is shorter. Note that The transfer of urgent data uses tone signal to transmit it immediately. The proposed algorithm is expected to reduce the energy consumptions and the delay.

• 스마트미디어저널
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• 제12권4호
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• pp.59-59
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• 2023

• 한국통신학회논문지
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• 제40권9호
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• pp.1786-1792
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• 2015

랜덤 선형 네트워크 코딩(Random Linear Network Coding, RLNC)은 멀티캐스트의 신뢰성을 높이는 방법으로 널리 사용되고 있다. RLNC 구현에 있어서 효율적인 연산을 위해 Galois Field (GF)를 사용한다. 상용 컴퓨터에서의 연산을 고려하였을 때 GF($2^m$)의 크기 m이 32보다 작을 경우, 곱셈과 나눗셈에 대해 사전에 계산된 table을 사용하면 모든 사칙 연산이 m에 관계없이 상수 복잡도를 가진다. 이로부터 RLNC의 연산 복잡도는 m에 반비례하는 것을 보인다. 추가적으로, m이 커짐에 따라 발생하는 헤더 길이 증가, 메모리 사용량 증가 등의 추가적인 오버헤드를 고려하여 실용적인 GF의 크기를 선택한다. 이를 바탕으로 상용 컴퓨터에 RLNC를 구현하고 곱셈/나눗셈 연산 시에 사용되는 table의 종류와 한 번에 인코딩 되는 원본 패킷의 개수에 따른 성능을 실측한다.

• Journal of electromagnetic engineering and science
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• 제12권1호
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• pp.70-76
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• 2012

We compare the detection probabilities of the time-reversal(TR) detection system and the conventional radar system. The target is assumed to be hidden inside a random medium such as a forest. We propose a TR detection system based on the SAR(Synthetic Aperture Radar) algorithm. Unlike the conventional SAR images, the proposed TR-SAR system has an interesting property. Specifically, the target-related signal components due to the time-reversal refocusing characteristics, as well as some of clutter-related signal components are concentrated at the time-reversal reference point. The remaining clutter-related signal components are scattered around that reference point. In this paper, we model the random media as a collection of point scatterers to avoid unnecessary complexities. We calculate the detection probability of the TR radar system based on the proposed simple random media model.

• 한국통신학회논문지
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• 제21권4호
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• pp.893-910
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• 1996

Recently, there ary many researches on local area multichannel network as WDM technology developes. An ideal media access protocol in a multichannel network is one that shows short access delay under low load and high throughput under heavy load. This paper proposed a new media access protocol for WDM passive star coupler network. The proposed one is a random access rpotocol based on reservation. Access delay is short under low load by using random access method, and high throughput is achieved under heavy load by usin greservation access. Analytic model for the performance analysis of the proposed protocol is developed and performance of the proposed protocol is compared with the previous ones. The effect on the performance of the number of the nodes and channels, and the number of transceivers in each node are analyzed.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 추계학술대회
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• pp.187-190
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• 2009

네트워크 코딩 중 RLC (random linear coding)은 다양한 연구들에서 이미 그 효용성이 입증되었으며 실제 유/무선 네트워크 환경에서 RLC를 적용하는 연구들이 최근 활발하게 진행되고 있다. RLC는 간단한 방법론적인 특성과 그 효용성으로 인해 많은 관심을 받고 있지만, 실제 환경에서 RLC 디코딩 과정이 요구하는 높은 성능 복잡도로 인하여 실용성에 한계를 가진다. 이러한 상황에서 최근 병행 방법 (Parallelized method)을 이용해 RLC 디코딩 과정의 복잡도를 개선하고 이를 실제적인 비디오 전송에 적용하는 연구들이 진행되고 있다. 본 논문에서는 이러한 연구들과 더불어 무선 환경에서의 실시간 비디오 전송을 위한 비디오의 특성을 고려하는 RLC 기반의 실시간 비디오 전송 시스템을 제안한다. 또한 제안한 시스템 실험적으로 구현하고, 이를 실제 무선 네트워크 환경에서 검증하였다.

• 대한기계학회논문집B
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• 제20권9호
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• pp.3015-3029
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• 1996

The notion of effective transport property of a heterogeneous medium implies that the medium is large enough that the ergodic theorem holds and local fluctuation of the property can be neglected. In case that the medium is not large enough compared to its characteristic microstructure length scale, the effective property fluctuates and differs from the value of the medium being large enough. As a representative transport phenomenon, diffusion was considered and the fluctuation of varying effective diffusion property, diffusion coarseness $C_k$, was defined as a quantifying parameter. Scaled effective diffusion property, $^*$>/k$_1$ and $C_k$ were computed for the two phase random media consisting of matrix of diffusion coefficient k$_1$ and spheres of diffusion coefficient k$_2$. Numerical simulations were performed by use of the so-called first passage time technique and data were collected for existing microstructure models of hard spheres(HS), overlapping spheres(OS) and penetrable concentric shells(PCS).

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.197-202
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• 2007

Most of seismic reflection prospecting assumes subsurface formation to be homogeneous media. These models are not capable of estimating small scale heterogeneity which is verified by well log data or drilling core. And those synthetic seismograms by homogeneous media are limited to explain various changes at field data. So we developed a inhomogeneous velocity model which can estimate inhomogeneity of background medium to implement numerical modeling from homogeneous medium and inhomogeneous medium on the model. Background medium using three autocorrelation functions in order to generate inhomogeneous velocity media was according to dominant wavelength of background medium and correlation length of random medium. And then we compared shot gathers. The results show that numerical modeling implemented at inhomogeneous medium depicts complex wave propagation of field data.