• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.123-129
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• 2017

This paper proposes a new nonnegative matrix factorization (NMF) based direction-of-arrival (DOA) estimation method for multiple sound sources using a dual microphone array. First of all, sound signals coming from the dual microphone array are segmented into consecutive analysis frames, and a steered-response power phase transform (SRP-PHAT) beamformer is applied to each frame so that stereo signals of each frame are represented in a time-direction domain. The time-direction outputs of SRP-PHAT are stored for a pre-defined number of frames, which is referred to as a time-direction block. Next, In order to estimate DOAs robust to noise, each time-direction block is normalized along the time by using a block subtraction technique. After that, an unsupervised NMF method is applied to the normalized time-direction block in order to cluster the directions of each sound source in a multiple sound source environments. In particular, the activation and basis matrices are used to estimate the number of sound sources and their DOAs, respectively. The DOA estimation performance of the proposed method is evaluated by measuring a mean absolute error (MAE) and the standard deviation of errors between the oracle and estimated DOAs under a three source condition, where the sources are located in [$-35{\circ}$, 5m], [$12{\circ}$, 4m], and [$38{\circ}$, 4.m] from the dual microphone array. It is shown from the experiment that the proposed method could relatively reduce MAE by 56.83%, compared to a conventional SRP-PHAT based DOA estimation method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.80-83
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• 2010

This paper describes an analysis of decoding performance of multi-mode LDPC(Low Density Parity Check) decoder which supports three block lengths (648, 1296, 1944) and four code rates (1/2, 2/3,3/4, 5/6) for IEEE 802.11n WLAN system. A fixed-point model of LDPC decoder which adopts min-sum algorithm and layered decoding scheme is implemented using Matlab. From fixed-point simulation results for various bit-width parameters such as internal bit-width, bit-width of integer and fractional parts, an optimal design condition and decoding performance of LDPC decoder are analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.568-577
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• 2005

In this paper, we propose the transmission scheme for the space-time block coded spatial multiplexing systems that have adaptive rate and power allocation per each transmit antenna through the use of feedback information related to channel state. Simulation results show that the adaptive power and rate transmission scheme gain more than 4.5 dB over conventional equal-power and rate transmission scheme.

• Journal of Broadcast Engineering
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• v.7 no.1
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• pp.37-44
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• 2002

In this paper. we propose a new video coding scheme with multi-resolution motion compensation and residual quantization. The main functional blocks of the proposed scheme include multi-level wavelet decomposition. motion estimation and motion compensation. raster scanning within each subband. formation of block trees and blocking partitioning. and adaptive arithmetic coding. Although the proposed ceding scheme is simple and requires low computational complexity, it produces bitstreams tilth good features. such as the embedded structure and SNR scalability. Experimental results demonstrate that the proposed coding scheme is quote competitive to and often outperforms other wavelet-based video coding schemes in the literature.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.279-282
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• 2012

로컬 히스토그램 평활화(LHE)는 영상에서 로컬 정보를 강조하기 위한 효율적인 알고리즘 중 하나이다. 그러나 이 알고리즘은 스펙클 노이즈를 증폭시키는 단점을 가진다. 따라서, 기존의 로컬 히스토그램 평활화 기법을 확장한 다중 레이어 블록 오버랩 히스토그램 평활화 기법을 이용하여 기존 로컬 히스토그램 평활화 기법들의 문제점을 해결하고자 하였다. 이 방법은 3단계-컨트라스트 향상 단계, 노이즈 제거 단계, 통합 단계로 이루어진다. 제안된 방법에서는 기존 방법의 컨트라스트 향상 단계에서 일반적인 로컬 히스토그램 평활화 방법이 아닌 컨트라스트를 제한하는 적응적인 히스토그램 평활화 기법을 적용하고, 노이즈 제거 단계에서 새로운 바이레터럴 필터를 적용하였다. 즉, 기존 방법의 문제점들을 해결하도록 알고리즘을 변형하여 기존 알고리즘의 성능을 개선하였다. 실험 결과는 제안된 방법이 기존의 방법 및 잘 알려진 로컬 히스토그램 평활화 기법들과 비교하여 좋은 성능을 내는 것을 확인하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2006.11a
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• pp.197-200
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• 2006

ATSC DTV시스템에서는 심볼타이밍 동기를 위해서 ATSC규격에 소개되어있는 $77.3{mu}s$ 마다 반복적으로 삽입되어있는 세그먼트 싱크를 이용하는 세그먼트 동기 방법 또는 QAM과 같은 다중레벨을 가지는 신호에 일반적으로 사용되는 가드너(Gardner)방법을 사용한다. 이중 가드너 방법은 매심볼마다 타이밍 에러성분을 추출하므로 다중경로 채널에서 타이밍동기를 추적하면서 유지하는데 유리한 방식이어서 일반적으로 사용한다. 가드너 방법을 이용하는 ATSC DTV시스템에서 가드너 방법에 에러를 검출하기 위해 사용되는 가드너 타이밍 에러 검출기(Timing Error Detector)는 수신단의 파워레벨이 기준 파워레벨에서 크게 벗어날 경우 에러를 검출 할 수 없는 문제점을 가지고 있다. 이를 해결 하기 위해 가드너 타이밍 에러 검출기 블록 앞에 송신파워 레벨과 수신파워 레벨의 비를 이용하여 정상적인 수신 파워 레벨로 수신학 수 있도록 보정하는 블록을 추가하여 전체적인 동기성능을 향상시키는 알고리즘을 제안한다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.88-94
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• 2009

This paper proposes real time object detection and tracking algorithm that can be applied to security and supervisory system field. A proposed system is devide into object detection phase and object tracking phase. In object detection, we suggest Adaptive background subtraction method and Adaptive block based model which are advanced motion detecting methods to detect exact object motions. In object tracking, we design a multiple vehicle tracking system based on Kalman filtering. As a result of experiment, motion of moving object can be estimated. the result of tracking multipul object was not lost and object was tracked correctly. Also, we obtained improved result from long range detection and tracking.

• The KIPS Transactions:PartC
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• v.13C no.7 s.110
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• pp.865-872
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• 2006

Cooperative communications (CC) have received a great deal of attention recently as an efficient way to obtain the spatial diversity without physical arrays. Thus, space-time block codes (STBC) which are well-known for use in co-located multi-antenna systems can be still utilized for single-antenna users in a distributed fashion. In this paper, we propose a cooperative signaling structure using the $\frac{3}{4}$-rate STBC and derive closed-form BER expression which takes the effect of network geometry and transmit power constraint into account. A variety of simulated and numerical results demonstrated the cooperation considerably outperforms the direct transmission when partners are located in appropriate positions.

• Smart Media Journal
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• v.12 no.9
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• pp.38-44
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• 2023

In this paper, a blockchain-based platform of NFT(Non-Fungible Token) reports was proposed to ensure the reliable performance contents of field study trip. It is possible to identify and manage the personal multi biomeric authentication user ID of activity records for students in a mobile IP-based metaverse with the linkage of extended reality(XR). At this time, many quests and incentives of platform are provided to induce students to experience smart and fun field studying facilities by linking real trip experiences and virtual extended_reality studies in the metaverse interworking.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.48-58
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• 2012

New digital predistortion technique is proposed for power amplifier linearization in multi-band transmission systems. We consider a system where muli-band signals are combined and amplified by a single power amplifier (PA). In this system, the PA output is distorted by the nonlinear cross-products between different band signals as well as their own nonlinear self-products. To compensate these nonlinear effects, we propose a multiple PD structure. Each PD removes the nonlinear cross-products and self-products to mitigate the spectral regrowth for the corresponding band. Since the PD parameters for different bands are linked together, it is difficult to find the PD parameters separately. Thus, we propose an iterative method for finding the PD parameters jointly. For demonstration of the proposed method, multi-band characteristics of PA are extracted from a commercial power amplifier. Computer simulation was executed based on the PA parameters. The simulation results show that the proposed method can effectively linearize the PA and remove spectral regrowth at each signal band.