Abdoreza Kiani - Department of Electrical Engineering, Abadan Branch,Islamic Azad University, Abadan, Iran
Fatemeh Geran - Faculty of Electrical and Computer EngineeringShahid Rajaee Teacher Training University, Tehran, Iran

Power-line communication (PLC) carries data on a conductor that is also used simultaneously for AC electric power transmission or electric power distribution to consumers. Power-line communications systems operate by adding a modulated carrier signal to the wiring system. Different types of power-line communications use different frequency bands. Since the power distribution system was originally intended for transmission of AC power at typicalfrequencies of 50 or 60 Hz, power wire circuits have only a limited ability to carry higher frequencies. Data rates and distance limits vary widely over many power-line communication standards. Low-frequency (about 100– 200 kHz) carriers impressed on high-voltage transmission lines may carry one or two analog voice circuits, or telemetry and control circuits with an equivalent data rate of a few hundred bits per second; however, these circuits may be many miles long. Higher data rates generally imply shorter ranges; a localarea network operating at millions of bits per second may only cover one floor of an office building, but eliminates the need for installation of dedicated network cabling. Reliable and high speed communication over power lines requires a robust modulation scheme, like a Discrete Wavelet Transform (DWT)based modulation technique, hence the quality of data communication over the noisy in-home power line network can be improved. This paper investigates the performance of conventional Orthogonal Frequency Division Multiplexing(OFDM) and Discrete Wavelet Transform-based OFDM (DWT-OFDM) systems in the presence of background and impulsive noise in multipath power lines as a communication channels. The time and frequency localization properties of thewavelet transform mitigates narrowband and heavy impulsive noise in the power lines which results in performance improvement. Simulation results in terms of PAPR, PSD, and Bit Error Rate (BER) show that DWT-OFDM is more robust against interference and multipath effects compared to DFTOFDM,and increasing the length of the basis function improves BER and PAPR.

DWT-OFDM,BPL,Multipath,Noise,BER,PAPR,PSD