Research On Reducing Peak-to-average Power Ratio Of Orthogonal Frequency Division Multiplexing System In Power Line

Power Line Communications, also called PLC, refers to a mode of transmission ofsignals, such as language and data etc., by power lines. Orthogonal Frequency DivisionMultiplexing, also called OFDM, is a critical technology for the realization of PLC. TheOFDM, which has an excellent resistance against multipath fading and interference, is animportant technique of data transmission. However, the high peak to average power ratio(PAPR) reduces OFDM system performance. To improve the performance of Power LineCommunication, we must reduce PAPR of the OFDM signal. In this paper, the research ismainly that characteristic of the Power Line Channel in Power Line OFDM system andhow to reduce peak to average power ratio of this system.Firstly, an improved selective mapping method based on bit selective mappingmethod is given. The improved bit selective mapping method separates the odd bits fromeven bits of input signals, then carries on phase rotation operation and regroups. Thus thismethod can produce more transmission sequences, and reduce the PAPR of the OFDMsystem of the power line. The simulation results showed that, having ensured theperformance of bit error rate, the modified scheme can achieve the aim that reducing thePAPR in Power Line OFDM system.Secondly, due to this shortcoming of traditional selective mapping method to sendside information, this paper proposes a constellation extension selective mapping method.Begin this paper improves the constellation extension technique to generate the narrowedamplitude signals by mapping, and takes the improved constellation extension techniqueapplied to the traditional selective mapping method. Using selective expansion mappingmethod transmits the sequence containing smaller amplitude signals to reduce the PAPRof the system. The simulation results showed that, having ensured the performance of biterror rate, the modified scheme can reduce much more the PAPR in Power Line OFDMsystem.Finally, this paper takes the improved constellation expansion technology applied tothe part transmit sequence method. Using constellation extension technique to choose the segmented signals for extending mapping, thus the amplitude of transmitting signals isreduced partly. The simulation results showed that, having ensured the performance of biterror rate, the modified scheme can reduce much more the PAPR in Power Line OFDMsystem compared with the conventional part transmit sequence method.