Han-Byul Lee

Channel adaptation for time-varying powerline channel and noise synchronized with AC cycle

Broadband Power Line Communications (PLC) technology allows the usage of electrical power supply networks for communications purposes, such as audio/video streaming and broadband internet access. The powerline has an inherent characteristic that is the cyclic variation of channel and noise with the phase of the AC line cycle. To achieve either high throughput or high robustness, we apply dynamic channel adaptation scheme that exploits the cyclic variation of powerline characteristics. In this paper, we introduce an expedient, dynamic channel adaptation which is robust against the short-time variation of the AC synchronized powerline channel and noise. We analyze the performance enhancement for the measured powerline channel and noise when the proposed adaptation scheme is applied to the Korean standard on high speed powerline communications.

Cooperative Multihop AF Relay Protocol for Medium-Voltage Power-Line-Access Network

This paper proposes a cooperative multihop amplify-and-forward (AF) relay protocol for a medium-voltage (MV) power-line access network. The relay transmission scheme is a promising protocol since it provides enhanced network channel capacity which exploits cooperative diversity by combining the relayed signal and the direct signal. We propose a new signaling model for the cooperative multihop AF relay protocol and derive a closed-form expression of the channel capacity. The channel capacity of the proposed protocol is analyzed over the MV power-line channel and noise models. Numerical simulations show that the proposed protocol introduces a notable capacity increase compared to conventional multihop schemes.

PHY abstraction methodology for the performance evaluation of PLC channels

In this paper we present the abstraction model of physical (PHY) layer of an Orthogonal Frequency Division Multiplexing (OFDM)-based powerline communication (PLC) system. This paper describes the PHY abstraction methodology suitable to predict the PHY layer error performance in a realistic powerline channel environment including frequency-selective interference. The approach to predict the PHY layer performance and the process to obtain the detailed parameters of PHY abstraction models are presented. The parameters of developed PHY abstraction models for several modulation and coding schemes used in the OFDM-based PLC PHY layer are presented in this paper. The validation result of the proposed PHY abstraction methodology shows that the developed PHY abstraction model provides a high accuracy of error performance prediction for PLC channel models in the powerline noise environment. Therefore the developed PHY abstraction model can be used for the further system-level simulations or MAC simulations regarding both error performance prediction and for fast link adaptation purposes.

Superresolution TOA Estimation With Computational Load Reduction

Although the superresolution multipath delay profile (MDP) estimation technique enhances the time resolution of a low-resolution MDP by using matrix computations, the computational load for the matrix computations is a problem, because it drastically increases with the length of the MDP. Because positioning systems require the time of arrival (TOA) of the first path only, it is possible to reduce the computational load by applying the matrix computations only to the part of the MDP that is narrowed but still includes the TOA of the first path. This paper proposes a scheme for determining the observation window of MDP from the low-resolution TOA estimates, which are obtained from the MDPs produced by the pseudonoise correlation method. The proposed scheme makes use of the random nature of the low-resolution TOA estimates to further reduce the observation window. The computational efficiency and estimation accuracy of the proposed scheme are examined by channel simulations based on the Saleh-Valenzuela indoor channel model and are also compared with the computational efficiency and estimation accuracy of the conventional superresolution technique without the observation window reduction.

Ensemble of Deep Convolutional Neural Networks for Prognosis of Ischemic Stroke

We propose an ensemble of deep neural networks for the two tasks of automated prognosis of post-treatment ischemic stroke, as imposed by the ISLES 2016 Challenge. For lesion outcome prediction, we employ an ensemble of three-dimensional multiscale residual U-Net and a fully convolutional network, trained using image patches. In order to handle class imbalance, we devise a multi-step training strategy. For clinical outcome prediction, we combine a convolutional neural network (CNN) and a logistic regression model. To overcome the small sample size and the need for whole brain image, we use the CNN trained using patches as a feature extractor and trained a shallow network based on the extracted features. Our ensemble approach demonstrated an appealing performance on both problems, and is ranked among the top entries in the Challenge.

Capacity analysis of relay channels for medium voltage powerline access network

To ensure the reliable data communication and increase the efficiency of resources which is an essential requirement for the future smart grid services, this paper describes a cooperative relaying scheme for the medium voltage (MV) powerline access network. We analyze the capacity of cooperative relaying protocol over the MV powerline channel model. Numerical results show that the cooperative relaying protocol introduces a notable capacity increase compared with conventional schemes.

Active secondary user selection algorithm of simo opportunistic spatial orthogonalization in fading cognitive radio networks

The opportunistic spatial orthogonalization (OSO) scheme, proposed by Cong Shen and Michael P. Fitz, allows the existence of secondary users during the period in which the primary user is occupying all licensed bands. This paper introduces an active secondary user selection algorithm which mitigates the interference from the primary user transmitter to the secondary user receiver. In order to select the active secondary user, we adopt a fusion center concept, which is utilized for the cooperative spectrum sensing. A proposed algorithm guarantees the minimum average throughput of the primary user and overcomes the average sum throughput of a conventional OSO. We have numerically analyzed the average throughput under various constraints.

Active Secondary User Selection Algorithm of Opportunistic Spatial Orthogonalization Considering Interference by a Primary User

The opportunistic spatial orthogonalization (OSO) scheme, proposed by Cong Shen and Michael P. Fitz, allows the existence of secondary users during the period in which the primary user is occupying all licensed bands. This paper introduces an active secondary user selection algorithm which mitigates the interference from the primary user transmitter to the secondary user receiver based on single-input multi-output system without altering a primary user`s transmission strategy. A proposed algorithm guarantees the minimum average throughput of the primary user and overcomes the average sum throughput of a conventional OSO. We have numerically analyzed the average throughput under various constraints.

The design of the relay system based on interference alignment and block diagonalization in multiuser MIMO channel

We have introduced various relay operation and proposed a precoding for the multiuser MIMO relay system. The proposed scheme based on IA and BD suppresses the intercell interference and multiuser interference, which makes it possible to support multiple users at the same time. The proposed relay operation scheme has higher complexity for IA and BD but better performance over the conventional scheme. Numerical results show that the sum rate of conventional relay model without IA converges though channel gains of BS-MS link and BS-RS link increase, since total overall sum-rate is limited by channel of BS-RS link.