The Study On The Reduction Of The Peak-to-Average Power Ratio In OFDM System

Now, the experts and the scholars are more attentive to the next generationmobile communication system as the 3rd generation mobile communication systemis being applied in the business. Orthogonal Frequency Division Multiplexing(OFDM) technology, known to be well suited for high rate transmission over radiochannel of the next generation mobile communication system, has generated a largeamount of research interests. OFDM signals have efficient spectral bandwidth, andthe performance of the OFDM system against multipath fading is better than that ofthe single carrier modulation system. One of the major drawbacks of OFDM systemis that the OFDM signal of the transmitter can have high peak-to-average powerratio (PAPR), which limits OFDM's wide applications. According to the weaknessmentioned above, this dissertation focuses on how to reduce the PAPR effectivelyand use MATLAB software to achieve simulation.This thesis firstly introduce the basic theory of OFDM system and itsadvantages and disadvantages, and then deduces the reasons of high PAPR and sumsup all kinds of methods of reducing PAPR. The paper analyzes the disadvantages ofpeak window method and give a improved method. It has improved on thecompanding transform algorithm to reduce PAPR in this paper. It is proved that thecomputation complexing of the algorithm is far smaller than the former. Based onthe theory of simple block coding, a new simple coding scheme of PAPR reductionis proposed in the thesis. A coding scheme based on Golay complementary sequenceand Reed-Muller codes is introduced to reduce the PAPR of OFDM system.Finding the ways, which not only can effectively reduce PAPR in OFDM, butalso has moderate calculation difficulty, is the core problem of PAPR research.Thus, there is a tradeoff between the performance and difficulty.