Research Of Lowing The PAPR Of OFDM System Based On Hybrid Modulation

Orthogonal Frequency Division Multiplexing (OFDM) is an effective multi-carrierparallel signal transmitting technique, the OFDM system can bring many advantages, such asit has high spectrum efficiency, it is available to counterwork with frequency-selected fadingand multi-paths fading which exsist in system,it is also easier to the modulation anddemodulation of the translating singal, and its receiver has no complex equalizer. So, to thenext generation wireless communication system，the OFDM technology has already been animportant solution.However, some drawbacks also exsist in OFDM system.One problem is ithas the high peak to average power ratio (PAPR). To the OFDM system, High papr willdecrease the spectrum efficiency of OFDM system greatly. So,the research of reducing thePAPR of OFDM system has great practical significance.The contents and main achievements of this paper can be summarized as follow:(1) Firstly, this paper analyze the origin and influence of high PAPR in OFDM systems，then the paper give out the definition of PAPR and depict the regularities of distribution forstatistic characteristics．(2) Secondly, Based on analyzing the previous works of reducing PAPR such as SLM、PTS algorithm, a new “T” way by using an IFFT conversion is proposed, the new algorithmcan predigest the complexity of system, as well as reduce the PAPR in OFDM systemsharply.by Matlab simulation, we get good result.(3) Thirdly, Golay complementary sequence is studied in this thesis.This kind of codingtechnology can lower the PAPR value3dB directly.(4)Finally, a novel scheme based on hybrid modulation is proposed. The new algorithmnot only decrease the papr but also reduce complexion in OFDM system.