A Research Of Technology For Reducing PAPR Of OFDM System

OFDM technology is a special multi-carrier modulation technology, it has a lot ofadvantages compared with other several existing mature technologies, namely, time divisionmultiple access, code division multiple access, frequency division multiple access and spacedivision multiple access, so it is widely considered a core technology in next generationwireless communication system. One of the most typical disadvantages of OFDM technologyis the high peak-to-average ratio, there are many methods can be used to reduce PAPR, butthese methods have the problems of either causing signals distortion or having highcomputational complexity, and so on.A novel method is proposed to reduce high PAPR of OFDM effectively after a lot ofresearches, namely, dividing area probability phase reverse method. The central idea isexpressed as follows, it carries out the operation adding the phase of digital modulationsub-carrier signals transmitted with each row of the phase matrix of quartered modulationsignal, and then normalizes the phase values of the phase sum matrix obtained. Separatelystatistics the number of each phase values of the phase sum matrix fall into the circumferencecorresponding area, these areas are four different areas that the angle of the circumference isdivided into according to the rules of dividing area, and each area is called one dividing area,and then stores all the branch serial numbers of the area in which after analyzing the signalsexceed a given threshold value. It will get phase reverse statistical matrix after dealing withall the values of the rows of phase sum matrix according to the method above, then reversesthe phase of the sub-carrier signal corresponding to the branch serial number which appearsthe most frequency in the phase reverse statistical matrix, that is to say reverses the phase ofthe sub-carrier signal according to the rules of phase reverse, so once process of dividng areaphase reverse has been completed, meanwhile it will get a new set of sub-carrier signals usedto be calculated and stored PAPR.Once dividng area phase reverse processing may not be able to achieve the ideal purposeof reducing PAPR, so it needs to be repeated the process above limited times, namely, repeatsthe process of dividng area phase reverse limited times, finally transmits the set of signalswhich makes PAPR smallest, soon afterwards a processing method which utilizes amplitudeweighting and half phase modulation is proposed to carry out no side informationtransmission. This algorithm is very simple and has low computational complexity for itsimply adds the phases and does comparative analysis, the result of computer simulationverifies the validity and effectiveness of this method.