Influence of branching a power line on PHY rate for PLC system using OFDM

Abstract

In this study, we measured transmission loss characteristics of the power line and physical layer (PHY) rate through the power line communication (PLC) modem in order to examine how branching influences the PHY rate of the orthogonal frequency-division multiplexing (OFDM) signal. The branch of the power line was lengthened so that the attenuation peak was created in the frequency band used in the PLC modem, and the regular attenuation of 50dB also was inserted so that the PHY rate could be measured near the state of the transmission limit. Moreover, the transmission loss characteristic of the power line was calculated by using the 4 port pair network method, and the PHY rate of the PLC modem by MATLAB/Simulink software, and these calculation results were compared with the measurement ones. From these results, we found the following: (1) A sharp attenuation peak of −20dB or more was created in the frequency region of 2MHz to 30MHz for the power line, and this attenuation peak moved to the low frequency region as the branch lengthened; (2) the PHY rate of about 190Mbps to 200Mbps was achieved and almost totally corresponded to the ideal state of a PLC modem, even when inserting the attenuation of up to 30dB, but the PHY rates decreased about 20Mbps to 30Mbps when inserting the attenuation up to 50dB; and (3) results for the PHY rate for the PLC modem calculated by using the calculation software of MATLAB/Simulink agreed with the measurement ones, and so the method for calculating the PHY rate for the OFDM signal through PLC modem was confirmed to be effective.