A Study on the Low Power Line Modulation and Power Line Channel Modeling

저압 전력선 통신 변조 기법 및 전력선 채널 특성

This thesis is about power line communication(PLC) over the low voltage grid. The main advantage with power line communication is the use of an existing infrastructure. The PLC channel can be modeled as having multi-path propagation with frequency-selective fading, typical power lines exhibit signal attenuation increasing with length and frequency. OFDM(Orthogonal Frequency Division Multiplexing) is a modulation technique where multiple low data rate carriers are combined by a transmitter to form a composite high data rate transmission. To implement the multiple carrier scheme using a bank of parallel modulators would not be very efficient in analog hardware. Each carrier in an OFDM is a sinusoid with a frequency that is an integer multiple of a base or fundamental sinusoid frequency. Therefore, each carrier is a like a Fourier series component of the composite signal. In fact, it will be shown later that an OFDM signal is created in the frequency domain, and then transformed into the time domain via the Discrete Fourier Transform(DFT).

본 연구는 저압 전력선에서의 데이터 통신에 적합한 변조 방식으로 주목받고 있는 다중 반송 변조의 일종인 OFDM(Orthogonal Frequency Division Multiplexing)의 변조를 실험하고, 이들 데이터를 전달 할 매체인 전력선을 채널 모델링 하였다. 전력선은 각종 전자기기에 의해 분기 연결되어 지연 전파의 경우와 임펄스성 잡음원이 존재하는 것으로 알려져 있다. 반송 주파수와 전력선의 길이에 의해 주파수 선택적 페이딩이 발생함을 알 수 있다.