• Journal of IKEEE
• /
• v.26 no.1
• /
• pp.36-42
• /
• 2022

This study presents an analysis of the human body channel as an electric signal path using body impulse response (BIR). The human body communications (HBC) has recently emerged as an effective signal transmission method to create wireless body area networks (WBAN). We provide body channel characteristics based on measured BIR in a proper experimental environment for the HBC using capacitive coupling with a customized channel sounding device, which can be applied as a guideline for the HBC system design. The frequency response of the BIR, extracted by a customized signal processing for the measure signals, shows the channel path loss (CPS) between 0 MHz and 100 MHz with an average CPS of approximately 46.8 dB. In addition, the relative noise power distributions can provide estimations on the signal to noise ratio at the HBC receiver in terms of capacitor and resistor values in the measured frequency band and the frequency band lower than 3 MHz considering the baseband signal detection.

• The Journal of the Acoustical Society of Korea
• /
• v.27 no.3
• /
• pp.154-162
• /
• 2008

Signals in an underwater channel get distorted by multipath propagation. In this paper, pre-coding method is suggested which helps comprehending the signals with minimum equalization. The signals are transformed based on the knowledge of the impulse response of the channel. Proposed pre-coding method is tested by simulations based on the ray theory and through water tank experiments. In weak multipath environment, in case of an SNR of about 20 dB, BER is $10^{-3}{\sim}10^{-4}$, while in strong multipath environment, similar BER is achieved with SNR of about 30 dB. In order for the pre-coding method to be used for underwater vehicles, channel prediction method utilizing the waveguide invariant is suggested and tested.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.47 no.3
• /
• pp.23-31
• /
• 2010

The increasing demands on low-power, and low-complexity video encoder have been motivating extensive research activities on distributed video coding (DVC) in which the encoder compresses frames without utilizing inter-frame statistical correlation. In DVC encoder, contrary to the conventional video encoder, an error control code compresses the video frames by representing the frames in the form of syndrome bits. In the meantime, the DVC decoder generates side information which is modeled as a noisy version of the original video frames, and a decoder of the error-control code corrects the errors in the side information with the syndrome bits. The noisy observation, i.e., the side information can be understood as the output of a virtual channel corresponding to the orignal video frames, and the conditional probability of the virtual channel model is assumed to follow a Laplacian distribution. Thus, performance improvement of DVC systems depends on performances of the error-control code and the optimal reconstruction step in the DVC decoder. In turn, the performances of two constituent blocks are directly related to a better estimation of the parameter of the correlation channel. In this paper, we propose an algorithm to estimate the parameter of the correlation channel and also a low-complexity version of the proposed algorithm. In particular, the proposed algorithm minimizes squared-error of the Laplacian probability distribution and the empirical observations. Finally, we show that the conventional algorithm can be improved by adopting a confidential window. The proposed algorithm results in PSNR gain up to 1.8 dB and 1.1 dB on Mother and Foreman video sequences, respectively.

• The Journal of the Acoustical Society of Korea
• /
• v.29 no.7
• /
• pp.458-467
• /
• 2010

In this paper, a new audio reproduction system was developed in which the cross-talk signals would be reasonably cancelled at an arbitrary listener position. To adaptively remove the cross-talk signals according to the listener's position, a method of tracking the listener position was employed. This was achieved using the two microphones, where the listener direction was estimated using the time-delay between the two signals from the two microphones, respectively. Moreover, room reverberation effects were taken into consideration where linear prediction analysis was involved. To remove the cross-talk signals at the left-and right-ears, the paths between the sources and the ears were represented using the KEMAR head-related transfer functions (HRTFs) which were measured from the artificial dummy head. To evaluate the usefulness of the proposed listener tracking system, the performance of cross-talk cancellation was evaluated at the estimated listener positions. The performance was evaluated in terms of the channel separation ration (CSR), a -10 dB of CSR was experimentally achieved although the listener positions were more or less deviated. A real-time system was implemented using a floating-point digital signal processor (DSP). It was confirmed that the average errors of the listener direction was 5 degree and the subjects indicated that 80 % of the stimuli was perceived as the correct directions.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2014.11a
• /
• pp.224-225
• /
• 2014

본 논문에서는 양자 통신을 실제적인 환경에서 구현하고자 하는 노력의 일환으로 개발된 연속 변수 양자 통신 기법에 대해 소개한다. 연속 변수 양자 통신 전반에 대한 설명에 이어 이를 이용한 최신 응용 기술들을 소개한다. 연속 변수 환경에서 구현된 다중 접속 채널, 최소 제곱 예측법, 그리고 다중 반송파 기법을 소개하고 그 효과와 한계를 서술한다.

• Proceedings of the IEEK Conference
• /
• 1999.06a
• /
• pp.179-182
• /
• 1999

전력 증폭기의 3차나 5차 비선형성은 인접 통신 채널에 직접적인 영향을 미치므로 선형화 기법을 이용하여 출력단의 혼변조 신호를 감쇄시켜야 한다. 본 논문에서는 전력 증폭기의 입력 신호를 기저대역에서 왜곡시켜 전력 증폭기를 선형화 시키는 디지털 사전 왜곡기를 구현하였다. 측정에 앞서, 모의실험을 통하여 시스템 변수에 따른 선형화기의 성능을 예측하고, 1차원 참조표(look-up table)를 사용한 사전 왜곡기의 측정 결과, 약 9 dB의 ACPR 개선 효과를 얻을 수 있었다.

• Information and Communications Magazine
• /
• v.28 no.2
• /
• pp.10-16
• /
• 2011

본고에서는 앞으로의 무선통신 환경의 변화를 예측하고 변화에 대응하기 위한 해결방안으로 무선통신 시스템의 '지능화'와 '3차원화'를 제안한다. 그리고 이를 바탕으로 지능형 인프라, 지능형 단말기, 협동통신, 3차원 채널 모델링의 4가지 요소로 구성된 지능형 3차원 무선통신 시스템에 대해 소개하고 현재 진행중인 관련 연구에 대해 살펴본다.

• Proceedings of the Optical Society of Korea Conference
• /
• 2001.02a
• /
• pp.12-13
• /
• 2001

인터넷의 대중화로 폭발적으로 증가하는 데이터 및 영상 정보를 수용하기 위해 초고속 전송 시스템이 요구되고 있다. 그림 1은 1996년을 기준으로 통신네트워크의 트래픽 증가 추세를 나타내었다. 데이터를 포함한 총 트래픽은 매년 2배 이상씩 증가하므로 2006년에는 현재보다 100 배 많은 트래픽이 예측된다. 그러므로 2.5 Gb/s 16 ～ 32 채널 WDM (Wavelength Division Multiplexing) 광전송 시스템이 주로 사용되고 있는 현시점과 비교하면 2006년에는 4 Tb/s 이상의 WDM 광전송 시스템이 필요할 것이다. (중략)

• Proceedings of the IEEK Conference
• /
• 2006.06a
• /
• pp.213-214
• /
• 2006

To reduce the feedback overhead of predicted CSI (channel status information) of adaptive OFDM (orthogonal frequency division multiplexing), we use partial data of CSI and employ linear interpolation. Simulation results show estimated CSI and its MSE.

• Proceedings of the Korea Multimedia Society Conference
• /
• 2003.05b
• /
• pp.532-535
• /
• 2003

아웃바운드(Outbound) 형 콜 센터는 서비스 지향의 인바운드(Inbound) 형 콜 센터와는 달리 전화를 거는 주체가 고객에게 접촉하고자 하는 목적을 뚜렷하게 가진 상태에서 제품 또는 서비스, 정보제공 등을 전화나 기타 커뮤니케이션 채널을 통해 전달하는 업무를 담담한다. 본 논문에서는 아웃바운드 형 콜 센터 시스템을 예측 다이얼링(Predictive Dial Ing) 방식에 기반하여 개선된 콜 전략을 제안한다 개선된 콜 전략은 콜 센터 업무의 중심 역할인 콜링 리스트(Call ing List)를 데이터 추출 모듈을 사용하여 테이블로 구성한 뒤, 시간 활용을 통한 효율적 대응과 다양한 고객들의 정보를 바탕으로 고객과의 접촉확률을 증가시킬 수 있다.