• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 1998.11a
• /
• pp.398-402
• /
• 1998

본 논문에서는 유ㆍ무선 통신 채널을 통한 데이터 전송시 발생하는 비선형 왜곡을 적응 필터를 이용하여 보상하였다. 특히 통신채널에서는 심볼간 간섭(ISI)이 발생하는데 이러한 간섭을 비선형 필터를 이용하여 제거하였다. 비선형 채널을 모델링하는 방법에는 볼테라급수를 이용하는 방법과 쌍선형 방법이 있다. 쌍선형 방법은 볼테라 방법에 비하여 계산량이 적은 장점을 지니고 있다. 따라서 쌍선형 필터에 적응 알고리듬을 적용하여 신호의 왜곡을 보상하였다. 적응 알고리듬에는 LMS 계열과 LS 계열 알고리듬이 있으나 통신 채널에서는 알고리듬의 안정도가 중요하므로 LMS 계열 알고리듬을 적용하였다. 또한 적응 알고리듬은 입력 데이터의 상관성과 데이터 수에 의존하여 수렴속도와 안정도가 결정된다. 알고리듬의 수렴속도를 증가시키기 위하여 입력신호를 신호파형으로부터 다량의 데이터를 검출하는 방법을 적용하였다. 이러한 방법을 입증하기 위하여 입력신호는 2진 랜덤 가우시안 데이터를 이용하였고, 통신채널에서 채널간 간섭을 발생시켰으며 화이트 가우시안 잡음을 부가 시켰다. 이러한 신호를 수신한 수신기에 적응 등화기를 설계하여 대량의 데이터를 생성시키고, 적응 알고리듬을 적용하여 채널의 왜곡을 빠른 속도로 보상하였다.

• Journal of Broadcast Engineering
• /
• v.18 no.4
• /
• pp.619-630
• /
• 2013

In this paper, we propose an edge directed color demosaicing algorithm considering color channel correlation. The proposed method consists of local region classification step and edge directional interpolation step. In the first step, each region of a given Bayer image is classified as normal edge, pattern edge, and flat regions by using intra channel and inter channel gradients. Especially, two criteria and verification process for the normal edge and pattern edge classification are used to reduce edge direction estimation error, respectively. In the second step, edge directional interpolation process is performed according to characteristics of the classified regions. For horizontal and vertical directional interpolations, missing color components are obtained from interpolation equations based on intra channel and inter channel correlations in order to improve the performance of the directional interpolations. The simulation results show that the proposed algorithm outperforms conventional approaches in both objective and subjective terms.

• The Journal of the Acoustical Society of Korea
• /
• v.31 no.2
• /
• pp.107-113
• /
• 2012

In this paper, we have analyzed the performance of space diversity technologies using experimental data in order to analyze the usability of space diversity techniques in underwater channel environments. After analyzing the experimental data we found out that high diversity gain should not be expected when using a stationary transmitter with a stationary receivers in swallow underwater channel. And we also find out that the distance between sensors should be at least 8 wavelengths apart to take advantage of diversity gain in underwater moving channel environments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.8
• /
• pp.761-769
• /
• 2009

In this paper, we report on the channel capacity and diversity gain of the vehicle on-glass antenna for FM radio reception. The correlation coefficient and channel capacity were obtained using the simulated 3D radiation pattern of each antenna and the Rayleigh channel model for urban environment. To examine the channel capacity we used two antennas which are a simple straight antenna and L-type antenna. Then we observed the available channel capacity by varying the position of feeds and the shape of the L-type antenna. The sample antenna, which has a maximum feed distance with different polarizations, was built and the receiving performance was measured in the weak FM field area. From the results we confirmed that the distance between the feeds should be placed as far as possible for the high channel capacity. If the distance between the feeds are greater than a certain threshold value than the polarizations of the two antennas are getting more important for determining the channel capacity.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.2C
• /
• pp.247-254
• /
• 2004

We introduce a new space-time signal processing scheme that uses both transmitter diversity technique and transmitter beamforming technique for code-division multiple access (CDMA) systems. Over complex Gaussian Rayleigh channel, the introduced scheme achieves the diveristy gain through the transmitter diversity technique. and the SNR gain by th transmitter beamforming technique. Bit error rate (BER) analyses are given to each of the three cases in which the transmitter diversity scheme, the transmitter beamforming scheme and the introduced scheme are used, in the slowly varying Rayleigh frequency nonselective fading channel. The Monte-Carlo simulation results are shown to match to the analytic results. When the channels between distant antennas are independent, analytic results show that the introduced scheme achieves the lowest $E_{b/}$ $N_{0}$ at target BER 10$^{-6}$ . When the channels between distant antennas are correlated, analytic and simulation results show that the introduced scheme is more robust to the change of channel correlation.n.

• Journal of Broadcast Engineering
• /
• v.19 no.6
• /
• pp.826-835
• /
• 2014

Recently, spatial modulation (SM) schemes are considered to improve the reception performance in spatially correlated channel environments. SM schemes utilize a switching method between multiple transmitters to reduce the correlation among multiple transmitters to reduce the correlation of each received signals and can support transmission additional bits using antenna combinations without extra bandwidth. Therefore, SM schemes can overcome correlation interference of conventional MIMO in urban wireless channels. However, the performance comparisons between SM schemes are not yet performed in correlated urban wireless channels. In this paper, some representative SM schemes are compared and a suitable SM-MIMO system in correlated urban wireless channels is proposed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.10 s.89
• /
• pp.931-937
• /
• 2004

This study examines the channel capacity of a multiple antenna system based on OFDM(Othogonal Frequency Division Multiplexing) when there are correlations among received signals in the frequency selective Rayleigh fading. As for a case that two transmitting and two receiving antennas are used, the channel capacity is derived as a function of correlation in a closed-form and the effect on channel capacity is analyzed when the mean value of the of received signal power is identical/ non-identical between the two receiving antennas. Analytical results show that the channel capacity decreases with the correlation coefficient of the received signals, and the decreasing rate is accelerated when the correlation coefficient of the received signals is greater than 0.7. In addition, the channel capacity reaches its peak when the received mean signal power of each branch is identical.

• The Journal of the Acoustical Society of Korea
• /
• v.32 no.1
• /
• pp.79-85
• /
• 2013

Feature extraction of CASA system uses time continuity and channel similarity and makes correlogram of auditory elements for the use. In case of using feature extraction with cross correlation coefficient for channel similarity, it has much computational complexity in order to display correlation quantitatively. Therefore, this paper suggests feature extraction method using non-parametric correlation coefficient in order to reduce computational complexity when extracting the feature and tests to segregate target speech by CASA system. As a result of measuring SNR (Signal to Noise Ratio) for the performance evaluation of target speech segregation, the proposed method shows a slight improvement of 0.14 dB on average over the conventional method.

• Proceedings of the IEEK Conference
• /
• 2002.06a
• /
• pp.29-32
• /
• 2002

본 논문은 수평적 시공간 부호화 기법(Horizontal Space-Time Coding)과 송수신단에 별도의 빔형성 기법을 결합한 JBSTC(Joint Beamforming Space-Time Coding) 구조에 대한 제안 및 동작원리를 기술하고 성능을 분석하였다. JBSTC는 MIMO(Multi-Input Multi-Output) 송수신 시스템 채널 모델링을 기반으로 송신측 안테나간 상호 상관 행렬과 수신측 안테나간 상호 상관 행렬을 이용하여 송수신 빔형성기의 안테나 가중치들을 계산한다. 본 논문에서 제안하는 JBSTC 방식은 송수신단에서 발생하는 안테나 간격과 각퍼짐에 따른 상호 상관 값을 효과적으로 보정함으로써 기존의 수평적 시공간 부호화 기법보다 우수함을 알 수 있다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.8
• /
• pp.748-757
• /
• 2015

MIMO systems utilizing multiple antenna transmission and reception is one of the key technologies to enhance the capacity of 5G wireless communications. In order to obtain an appropriate performance evaluation of MIMO techniques, the usage of wireless channel model reflecting spatial channel characteristics is required, such as the 3-dimensional spatial channel model(3D SCM) proposed by 3GPP TR36.873 documentation. In this paper, we implement and verify the channel simulation environment based on 3D SCM, to present and compare the characteristics of UMi and UMa environments. We also apply MIMO transmission to the UMa scenario to investigate the channel correlation among antenna elements with different array distances and to identify the corresponding throughput changes. By evaluating the channel power correlations for randomly distributed users within the sector for different horizontal and vertical antenna distances, we present the statistical characteristics which determine the transmission performance under the SCM environment.