Kyong-Hoe Kim

Mitigation of effect of impulsive noise for OFDM systems over power line channels

Impulsive noise introduces significant time variance into the power line channel and causes performance degradation of orthogonal frequency division multiplexing (OFDM) systems. In this paper, we provide a performance analysis for OFDM-based power line communications in the presence of impulsive noise. Performance degradation of coherent M-ary PSK and differential MPSK can be mitigated by a signal level limiter. Simulation results present that the optimum signal level can significantly improve the performance of OFDM systems over power line channels with impulsive noise.

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.

Coordinated Beamforming with Limited BS Cooperation for Multicell Multiuser MIMO Broadcast Channel

The capacity of downlink multi-input multi-output (MIMO) systems is significantly limited by inter-cell co-channel interference (CCI). Improving the performance of cell edge users who suffers strong inter-cell CCI is still a crucial issue. In this paper, coordinated beamforming (CBF) algorithm for multicell multiuser MIMO system is proposed to cope with the presence of intel-cell CCI. In multicell environment with MIMO channel, limited base station (BS) cooperation is considered to design optimal transmit and receive beamformers which make interference-free at the receiver. Simulation results show that the proposed algorithms can improve the capacity of cell edge user effectively as well as the overall system capacity for multiuser multicell MIMO system.

Performance Analysis of LDPC Coded DMT Systems with Bit-loading Algorithms for Powerline Channel

This paper deals with two different approaches to overcome unfavorable channel characteristics and to obtain higher performance of PLC systems: Low density parity check (LDPC) coding and bit-loading algorithms for discrete multitone (DMT) modulation. We analyze the performance of LDPC coded DMT systems with bit-loading algorithms in terms of bit-error rate and data rate. Simulations are performed with statistically modeled in-home PLC channel and noise. Several bit-loading scenarios and LDPC coding schemes are also considered. The performances of the proposed DMT systems with and without LDPC codes are analyzed for the broadband PLC system design.

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.

Design and implementation of analyzing instrument for broadband powerline communications

This paper deals with the design and implementation of the analyzing instrument for the broadband powerline communication. This instrument has integrated functions for channel estimation, noise power spectrum measurement, and impedance measurement. It consists of a digital board with high speed DSP and FPGA chips, an analog board as a front-end adaptation to the powerline medium, and a Windows GUI application for presenting measurement results. This paper gives measurement algorithms used in this system and a description of the hardware and software prototype.