Chul-Yong Lee

Owing to the high cost of radio frequency (RF) chains and power consumption of broadband signals, it is suitable to include both analogue and digital processing for millimetre wave (mmWave) beamforming. In this study, hybrid beamforming (HBF) schemes are considered for multi‐user downlink mmWave systems. RF beamforming schemes are proposed for HBF transmission with perfect channel state information at transmitter (CSIT) and limited feedback information in the multi‐user mmWave channel. Simulatio

Generalized iterative methods for reducing noise in contaminated chaotic signals are proposed. These methods minimize a cost function composed of two parts: one containing information that represents how close enhanced signals are to the observed signal and another composed of constraints that fit the dynamics of the system. The convergence conditions and the error systems of the proposed methods are investigated. The proposed methods are compared via numerical experiments with Farmer's method w

An iterative method for reducing noise in contaminated chaotic signals is proposed. This method estimates the deviation of the observed signal from the nearest noise-free signal satisfying the system dynamics in order to get a noise-reduced (or enhanced) signal. To calculate the deviation we minimize a cost function composed of two parts: one containing information that represents how close the enhanced signal is to the observed signal and another including constraints that fit the dynamics of t

The inter-user interference is a critical performance degradation factor in a full-duplex multi-user system. However, the conventional pre-processing filters, such as null space projection filter and regularized channel inversion filter, are unsuitable for user pre-processing filter when each user has the same number of transmit and receive antennas. Thus, we propose an inter-user-interference cancellation scheme applicable to the users with the same number of transmit and receive antennas. By s

Since previous secure communications methods using chaotic systems require very high SNRs, knowledge of the initial conditions, and/or chaotic systems with the self-synchronization property, their application is limited. In this paper, a new secure communications scheme based on chaotic switching is discussed. The proposed scheme makes decisions on the incoming bits by comparing the power level of the dynamical error for each symbol signal after applying a noise reduction method based on the kno

In simultaneous wireless information and power transfer system (SWIPT), additional resource allocation for power transfer degrades system performance. Therefore, how to allocate power and time to data transmission and energy transfer is very important for the performance of time switching-based SWTPT system. In this paper, we propose a time switching-based full-duplex SWIPT system combined with self-energy recycling since self-interference harvesting is more efficient than simultaneous data tran

Abstract We propose a spatial domain interference cancelation scheme for full duplex bi-directional communication systems. Although the conventional pre-processing filters, such as null space projection and minimum mean square error (MMSE), can eliminate self interference, they require the spatial dimensions more than the number of receive antennas. However, proposed scheme requires only one spatial dimension regardless of the number of receive antennas, which enables more efficient antenna allo

본 논문은 MMSE 수신기를 가지는 MIMO MC-CDMA시스템에서의 출력 SINR을 분석한다. 단일 안테나에서의 분석을 위한 가정들이 다중안테나에 바로 확장 적용되지 않기 때문에 단일 안테나를 가지는 MC-CDMA시스템에 대한 기존의 성능 분석은 MIMO MC-CDMA 시스템에 바로 적용하지 못한다. 그러므로 본 논문에서는 Marcenko Pastur law와 확장된 Haar 유니터리 행렬의 특성을 이용하여 MIMO system에 대한 성능 분석을 시도한다. 분석을 통해 확산 코드 길이가 무한대로 갈 때 출력 SINR이 특정값으로 접근함을 보이고 그 값을 freeness가정을 통해 구하여 비트 오차확률을 구하고 실험과 비교한다.

채널 추정 오차가 존재하는 상황에서 MIMO 시스템의 채널 용량을 수식적으로 분석한다. 수식적인 분석에 의해, 채널 용량은 평균 신호 대 잡음비 (SNR) 와 함께 채널 추정 오차 (MSE)에 영향을 받음을 알 수 있다. 또한, 본 논문에서는 평균 SNR과 채널 용량의 손실량이 제한되어 있을 경우, 허용가능한 채널 추정 오차를 구함으로써 주어진 시스템에 적합한 채널 추정기법을 선택하는 기준을 제시한다. 실험 결과로부터 1 bps/Hz 채널용량의 손실에 대해 허용 가능한 채널 추정 오차는 20dB와 40dB의 평균 신호 대 잡음비에서 각각 와 임을 확인 할 수 있다.