• MALSORI
• /
• no.52
• /
• pp.111-120
• /
• 2004

This paper focuses on the DSP implementation of an HMM-based speech recognizer that can handle several hundred words of vocabulary size as well as speaker independency. First, we develop an HMM-based speech recognition system on the PC that operates on the frame basis with parallel processing of feature extraction and Viterbi decoding to make the processing delay as small as possible. Many techniques such as linear discriminant analysis, state-based Gaussian selection, and phonetic tied mixture model are employed for reduction of computational burden and memory size. The system is then properly optimized and compiled on the TMS320C6711 DSP for real-time operation. The implemented system uses 486kbytes of memory for data and acoustic models, and 24.5 kbytes for program code. Maximum required time of 29.2 ms for processing a frame of 32 ms of speech validates real-time operation of the implemented system.

• Proceedings of the IEEK Conference
• /
• 2004.08c
• /
• pp.576-580
• /
• 2004

In this paper, we present a design and implementation of a TV-Anytime compliant STB to provide personalized content consumption according to user preferences and various terminal/network conditions. This paper mainly details with a metadata engine which consists of meta data de-multiplexing, metadata decoding, and metadata-based content browsing. For personalized content consumption, the proposed metadata engine provides the following key functionalities: advanced EPG, non-linear segment navigation wirh Tables-of-Content and/or event-based summary, automatic recommendation of user-preferred programs, and etc. The implemented STB employing the metadata engine is successfully tested with a set of service scenarios in an end-to-end broadcasting test-bed.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
• /
• 1991.11a
• /
• pp.40-48
• /
• 1991

McEliece 공개키 암호체계에 대한 새로운 암호해독적 공격이 제시되어진다. 기존의 암호해독 algorithm이 exponential-time의 complexity를 가지는 반면, 본고에서 제시되어지는 algorithm은 polynomial-time의 complexity를 가진다. 모든 linear codes에는 systematic generator matrix가 존재한다는 사실이 본 연구의 동기가 된다. Public generator matrix로부터, 암호해독에 사용되어질 수 있는 새로운 trapdoor generator matrix가 Gauss-Jordan Elimination의 역할을 하는 일련의 transformation matrix multiplication을 통해 도출되어진다. 제시되어지는 algorithm의 계산상의 complexity는 주로 systematic trapdoor generator matrix를 도출하기 위해 사용되는 binary matrix multiplication에 기인한다. Systematic generator matrix로부터 쉽게 도출되어지는 parity-check matrix를 통해서 인위적 오류의 수정을 위한 Decoding이 이루어진다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2012.07a
• /
• pp.377-380
• /
• 2012

격자 감소 (lattice reduction) 알고리즘은 주어진 기저 벡터를 직교에 가까운 기저 벡터로 바꾸어 준다. 그중 대표적인 알고리즘으로 LLL (Lenstra, Lenstra & Lovasz) 알고리즘이 있다. 격자 감소 알고리즘을 이용하여 다중 안테나 입출력 (MIMO) 통신시스템의 선형 수신기(linear detector)의 성능을 향상 시킬 수 있다. 스피어 복호 알고리즘 (sphere decoding algorithm)은 MIMO 통신 시스템에서 사용되는 복호기중 최대 우도 복호기 (Maximum Likelihood Detector)와 비슷한 BER(bit error rate)성능을 가지고 복잡도를 줄일 수 있어서 많이 연구되어 왔다. 이때 스피어의 반지름의 설정이나 트리 검색 구조 방식 등은 복잡도에 큰 영향을 미친다. 본 논문에서는 LLL 알고리즘에 기반하여 스피어의 반지름 설정 및 트리 검색 노드 수를 제한하는 방식으로 스피어 복호 알고리즘의 복잡도를 기존 알고리즘에 비해 크게 낮추면서도 비트 오류률 (BER) 성능 열화를 최소한으로 한 알고리즘을 제안하고 전산 실험을 통해 검증한다.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.55 no.8
• /
• pp.369-374
• /
• 2006

Due to development of internet network environments and data compression techniques, the size and amount of multimedia data has greatly increased. They are compressed before transmission or storage. Dealing with these compressed data such as video retrieval or indexing requires decompression procedure in most cases. This causes additional computations and increases the processing time. In various applications a histogram is one of the most frequently used tools. Efficiency of extracting such histograms will drop down if decompression is involved. We propose a novel scheme for extracting histograms from images that are transformed into the compressed domain by 8x8 DCT(Discrete Cosine Transform). In this scheme an averaged version of original image is obtained by a simple linear combination of DCT coefficients with the sets of coefficients we designed.

• Journal of Communications and Networks
• /
• v.8 no.3
• /
• pp.275-285
• /
• 2006

Suitable for multi-input multi-output (MIMO) communications, the joint beamforming space-time block coding (JBSTBC) scheme is proposed for high-speed downlink transmission. The major functionality of the scheme entails space-time block encoder and joint transmit and receive eigen-beamformer (EBF) incorporating with block-ordered layered decoder (BOLD), and its operating principle is described in this paper. Within these functionalities, the joint EBFs will be utilized for decorrelating fading channels to cause an enhancement in the spatial diversity gain. Furthermore, to fortify the capability of layered successive interference cancellation (LSIC) in block-ordered layered decoding process, this paper will develop a simple ad-hoc transmit power discrimination scheme (TPDS) based on a particular power discrimination function (PDF). To confirm the superior behavior of the proposed JBSTBC scheme employing ad-hoc TPDS, computer simulations will be conducted under various channel conditions with the provision of detailed mathematical derivations for clarifying its functionality.

• Journal of Korea Multimedia Society
• /
• v.14 no.5
• /
• pp.642-649
• /
• 2011

Among the various aspects of offline handwritten character patterns, it is the great variety of writing styles and variations that renders the task of computer recognition very hard. The immense variety of character shape has been recognized but rarely studied during the past decades of numerous research efforts. This paper tries to address the problem of measuring image distortions and handwritten character patterns with respect to reference patterns. This work is based on mass-spring mesh model with the introduction of simulated electric charge as a source of the external force that can aid decoding the shape distortion. Given an input image and a reference image, the charge is defined, and then the relaxation procedure goes to find the optimum configuration of shape or patterns of least potential. The relaxation process is based on the fourth order Runge-Kutta algorithm, well-known for numerical integration. The proposed method of modeling is rigorous mathematically and leads to interesting results. Additional feature of the method is the global affine transformation that helps analyzing distortion and finding a good match by removing a large scale linear disparity between two images.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.42 no.1
• /
• pp.268-278
• /
• 2017

In this paper, we propose two novel detection schemes with low-complexity based on the unified receiver architecture which minimizes a fundamental tradeoff at rate-energy region in SWIPT system. The proposed detection schemes are twofold: The two-stage detection scheme and Euclidean distance combination detection scheme. The two-stage detection scheme detects amplitude information of symbols from rectified signals for energy harvesting. In the sequel, it detects symbols based on phase information of baseband signals for information decoding. The Euclidean distance combination detection scheme detects symbols using linear positive-weighted sum of two metrics: Euclidean distance based on baseband signals for information decoding and Euclidean distance based on rectified signals for energy harvesting. For numerical results, we confirm that the proposed detection scheme can achieve better performance than the conventional scheme in terms of symbol error rate, symbol success rate-energy region and achievable rate-energy region.

• Journal of Biomedical Engineering Research
• /
• v.28 no.2
• /
• pp.212-217
• /
• 2007

As a preliminary study for the development of electrical stimulation strategy of artificial retina, we set up a method fur the reconstruction of input intensity variation from retinal ganglion cell(RGC) responses. In order to estimate light intensity variation, we used an optimal linear filter trained from given stimulus intensity variation and multiple single unit spike trains from RGCs. By applying ON/OFF stimulation(ON duration: 2 sec, OFF duration: 5 sec) repetitively, we identified three functional types of ganglion cells according to when they respond to the ON/OFF stimulus actively: ON cell, OFF cell, and ON-OFF cell. Experiments were also performed using a Gaussian random stimulus and a binary random stimulus. The input intensity was updated once every 90 msec(i. e. 11 Hz) to present the stimulus. The result of reconstructing 11 Hz Gaussian and binary random stimulus was not satisfactory and showed low correlation between the original and reconstructed stimulus. In the case of ON/OFF stimulus in which temporal variation is slow, successful reconstruction was achieved and the correlation coefficient was as high as 0.8.

• Journal of the Korea Society of Computer and Information
• /
• v.13 no.4
• /
• pp.169-175
• /
• 2008

The existing block encryption algorithms have been designed for the encryption key value to be unchanged and applied to the round functions of each block. and enciphered. Therefore, it has such a weak point that the plaintext or encryption key could be easily exposed by differential cryptanalysis or linear cryptanalysis, both are the most powerful methods for decoding block encryption of a round repeating structure. Dynamic cipher has the property that the key-size, the number of round, and the plaintext-size are scalable simultaneously. Dynamic network is the unique network satisfying these characteristics among the networks for symmetric block ciphers. We analyze the strength of Dynamic network for meet-in-the-middle attack, linear cryptanalysis, and differential cryptanalysis. Also, In this paper we propose a new network called Dynamic network for symmetric block ciphers.