• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.1
• /
• pp.343-347
• /
• 2012

Non-linear equalization techniques using decision feedback structure are highly demanded for cancellation of intersymbol interferences occurred in severe channel environments. In this paper decision feedback structure is applied to the linear blind equalizer algorithm that is based on information theoretic learning and a randomly generated symbol set. At the decision feedback equalizer (DFE) the random symbols are generated to have the same probability density function (PDF) as that of the transmitted symbols. By minimizing difference between the PDF of blind DFE output and that of randomly generated symbols, the proposed DFE algorithm produces equalized output signal. From the simulation results, the proposed method has shown enhanced convergence and error performance compared to its linear counterpart.

• The Journal of the Acoustical Society of Korea
• /
• v.30 no.6
• /
• pp.308-314
• /
• 2011

This paper presents techniques for estimating directions of multiple sound sources ranging from $0^{\circ}$ to $360^{\circ}$ using circular probability distributions having a periodic property. Phase differences containing direction information of sources can be modeled as mixtures of multiple probability distributions and source directions can be estimated by maximizing log-likelihood functions. Although the von Mises distribution is widely used for analyzing this kind of periodic data, we define a new class of circular probability distributions from Gaussian and Laplacian distributions by adopting a modulo operation to have $2{\pi}$-periodicity. Direction estimation with these circular probability distributions is done by implementing corresponding EM (Expectation-Maximization) algorithms. Simulation results in various reverberant environments confirm that Laplacian distribution provides better performance than von Mises and Gaussian distributions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.10 no.7
• /
• pp.1074-1084
• /
• 1999

In this paper the bit error probability of noncoherent M-ary FSK system is derived from the probability density function of the envelope of the received signal over a frequency-nonselective slowly m-distributed Nakagami fading channel. Also, the performance of coherent M-ray FSK system is theoretically analyzed, using union bound over the similar fading channel. Then we compare uncoded performance results for M-ary FSK and DPSK signals in Nakagami fading channel.

• The Journal of the Acoustical Society of Korea
• /
• v.41 no.6
• /
• pp.662-667
• /
• 2022

Computing music similarity is an indispensable component in developing music search service. This paper focuses on learning a music similarity function in order to boost cover song identification performance. By using the probabilistic linear discriminant analysis, we construct a latent music space where the distances between cover song pairs reduces while the distances between the non-cover song pairs increases. We derive a music similarity function by testing hypothesis, whether two songs share the same latent variable or not, using the probabilistic models with the assumption that observed music features are generated from the learned latent music space. Experimental results performed on two cover music datasets show that the proposed music similarity improves the cover song identification performance.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.5 no.3
• /
• pp.36-47
• /
• 1994

The error performance of BPSK and QPSK signals with diversity reception in mobile-satellite channel is investigated considering nonlinearity of TWT (Traveling Wave Tube) amplifier in the presence of AWGN(Additive White Gaussian Noise) on the uplink and downlink paths. It is assumed that the fading on the dounlink path forms a Rician distribution. The Rician distribution is approximated by discrete probability values. The values are firstly found by Classical Moment Technique.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.2 no.1
• /
• pp.51-57
• /
• 2009

Blind equalization techniques have been widely used in wireless communication systems. In this paper, we investigate the information potentials in the criterion of minimizing Euclidian distance between two PDFs criterion for adaptive blind equalizers and evaluate BER performance of the method that has utilized an appropriate balance between the two information potentials, one from output samples and ramdomly generated desired samples at the receiver and another from the interactions among output samples. The balanced information potential method has shown in the BER performance results that it can produce significantly enhanced BER performance in blind equalization applications.

• Proceedings of the Korea Society for Simulation Conference
• /
• 2001.05a
• /
• pp.134-134
• /
• 2001

이동통신 망을 통한 멀티미디어 통신의 수요 급증으로, 차세대 이동통신 시스템에서는 패킷 교환에 기초한 망 구조가 사용될 것으로 예측된다. VOD(Voice Activity Detector)를 갖는 음성 단말은 데이터를 발생시키는 talk spurt(평균이 t$_1$인 지수분포를 따름)와 데이터를 발생시키지 않는 silence period(평균이 t$_2$인 지수분포를 따름)의 두가지 상태를 갖는 마코프 체인으로 모델링된다. Goodman at. al.은 음성 단말들이 talk spurt동안만 데이터를 전송하게 함으로써 더 많은 가입자들을 수용할 수 있는 PRMA(Packet Reservation Multiple Access) 기법을 제안되었다. PRMA 방식에서는 시간 축이 슬롯들로 구성되며 여러개의 슬롯들로 프레임이 형성된다. Silence period 상태에 있던 음성 단말은 talk spurt 상태가 되면 talk spurt의 첫 번째 데이터를 하나의 슬롯을 통해 전송하게 된다. 이때 단말들은 각 슬롯에서 데이터를 전송할 수 있는 확률을 나타내는 채널 접근 확률(channel access probability)에 의해 데이터를 전송하게 되며 전송에 성공하면 슬롯을 예약함으로서 다음 프레임부터는 동일한 위치의 슬롯을 통해 데이터들을 전송하게 된다. DS/CDMA(Direct Sequence/code Division Multiple Access)는 이동통신 단말의 수용 용량상의 이점, 소프트 핸드오버 능력, 보다 용이하게 셀 계획을 세울 수 있는 점 등에 의해 차세대 이동통신 망에서 채택될 예정이다. CDMA 시스템은 간섭(interference)에 의해 용량이 제한을 받게 되며, MAI(Multiple Access Interference)가 시스템의 성능에 많은 영향을 미치게 된다. Brand, et. al.은 간섭의 분산을 줄이기 위해 PRMA 개념을 DS/CDMA 환경으로 확장한 Joint CDMA/PRMA 프로토콜을 제안하였다. 이때 각 슬롯에서의 데이터 전송확률을 그 슬롯에서 예약상태에 있는 음성 단말의 수에 의존하게 하는 방식을 사용하였으며 데이터 전송확률을 나타내는 채널 접근 확률들을 시뮬레이션을 통해 유도하였다. 한편 음성 단말에게는 실시간 서비스를 제공해 주어야 하는 대신 데이터 단말에게는 실시간 서비스를 제공해 주지 않아도 되므로, 트래픽이 많을 때에는 음성 단말의 데이터 전송에 우선권을 주는 것이 바람직하다. 이를 위해서 Brand, et. al.은 채널 접근 확률을 각 슬롯의 트래픽 상태에 따라 적응적으로 산출하는 기법을 제안하였다. 본 연구에서는 Joint CDMA/PRMA의 성능이 채널 접근 함수의 효율성에 많이 의존하게 되므로 보다 효율적인 채널 접근 확률을 구하는 방법을 제안한다. 즉 채널 액세스 확률을 각 슬롯에서 예약상태에 있는 음성 단말의 수뿐만 아니라 각 슬롯에서 예약을 하려고 하는 단말의 수에 기초하여 산출하는 방법을 제안하고 이의 성능을 분석하였다. 시뮬레이션에 의해 새로 제안된 채널 허용 확률을 산출하는 방식의 성능을 비교한 결과 기존에 제안된 방법들보다 상당한 성능의 향상을 볼 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.17 no.3
• /
• pp.260-267
• /
• 1992

In this paper, the performance of frequency hopped(FH) M-ary frequency shift keyed(MFSK)system is analyzed with the fading channel and the multione famming. In general, the performance degradation of FH/MFSK system is due to the Rayleigh fading and the multitone jamming environment. In order to improve the system performance. the time diversity is used. When the time diversity is applied to the Rayleigh fading and the mulitone jamming, we get around 18dB and 19dB improvements. respectively. And when it is applied to both the Rayleigh fading and the multitone jamming, we get around 4 dB improvement.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.24 no.5
• /
• pp.305-318
• /
• 2012

Although the existing performance-based design method for the vertical breakwater evaluates an average sliding distance during an arbitrary time, it does not calculate the probability of the first occurrence of an event exceeding an allowable sliding distance(i.e. the first-passage probability). Designers need information about the probability that the structure is damaged for the first time for not only design but also maintenance and operation of the structure. Therefore, in this study, a time-dependent reliability design method based on a stochastic process is developed to evaluate the first-passage probability of caisson sliding. Caisson sliding can be formulated by the Poisson spike process because both occurrence time and intensity of severe waves causing caisson sliding are random processes. The occurrence rate of severe waves is expressed as a function of the distribution function of sliding distance and mean occurrence rate of severe waves. These values simulated by a performance-based design method are expressed as multivariate regression functions of design variables. As a result, because the distribution function of sliding distance and the mean occurrence rate of severe waves are expressed as functions of significant wave height, caisson width, and water depth, the first-passage probability of caisson sliding can be easily evaluated.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.6 no.4
• /
• pp.527-534
• /
• 2002

In this paper, efficiency in the acquisition of the PN code of the DS/CDMA system was analyzed by using the Nakagami-m probability density function that can model diverse fading channels. The system considers the fading environment that inevitably exists in the mobile communications channel environment. To analyze the efficiency of the system, the equations related to detection probability PD and false alarm probability PFA required for the acquisition of the PN code were induced by using the Nakagami-m probability density function. They were verified through simulation. For the DS/CDMA system an adaptive serial search technique was applied to acquire the PN code. To correct phase error, the equations related to detection probability PD and false alarm probability PFA that influence the time to acquire codes were induced after adding the PLL to each branch of the Rake Receiver. By using an induced equation, detection probability PD and false alarm probability PFA were verified through simulation.