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

Power line communication (PLC) channel conditions are bad. Power line channel isdue to has severe signal attenuation, strong noise, interference and other characteristics,so it is difficult to transmitting high speed data. OFDM technology with high spectrumefficiency and can effectively restrain intersymbol interference, resistance to multipathinterference and frequency selective fading and other significant advantages. It has beenas the basic transmission technology adopted by many international standards. However,OFDM system transmission of signal with high peak power ratio (PAPR), so this defecthas limited the OFDM technology is widely used. This article studied on how to restrainPAPR for OFDM system in power line, the specific content as follows:Firstly, because of the shortcoming that traditional selective mapping method forPAPR reduction in OFDM systems has high computational complexity and need transmitside information. In this paper, an improved SLM method without side information isproposed. This method map quaternary data onto the ring circle, then rotation phasefactor, the original point of a constellation map to multiple points of no coincident on thecircle. After IFFT transform, cyclic shift the one sub-block and recombination with theother one. This can produce more candidate signals, so this can further reduce theprobability of high PAPR appears.Secondly, this paper provided an improved method based on a modified widelylinear selective mapping technology. In this method is mainly to linear combination witheach other of real part and imaginary part of the time domain signals and then combinethe real-imaginary parts. This can produce more candidate signals. So it can obtain betterthe effect of reducing PAPR.Finally, this paper provided an improved PTS method. In this method, thereal-imaginary parts data was partitioned and after IFFT transform, cyclic shift the timedomain signal. Then can get more candidate signals, so it can effectively reduce PAPR.On this basis, this paper also gives improved PTS algorithm combined with compandingtechnique methods to reduce PAPR.The above three methods are simulated of OFDM system in power line, so to verifythe effectiveness of the method.