Research On Improving The PAPR Technology In OFDM System

OFDM technology is one of the key technologies of 4G with the advantages of high spectral efficiency, anti-multipath fading and flexible allocation of spectrum resources. But OFDM has two major shortcomings, one of which is the high Peak-to-Average Power Ratio(PAPR). High PAPR will increase the complexity of the transmitter and receiver, and reduce the effectiveness of the power amplifier. Accordingly, how to effectively improve the PAPR performance of the OFDM system has become a hot topic. The paper mainly focuses on how to improve the PAPR technology in OFDM system, proposes the IPTS method based on Hadamard transform and combines it with the traditional μ-law companding transformation method; presents the SLM method based on Hadamard transform and combines it with the novel μ-law companding transformation method.First of all, the thesis introduces the background and current status of the subject, and describes the basic principles and the key technologies of the OFDM system.Secondly, three PAPR reduction categories of the OFDM system are introduced, where the PTS method, the SLM method and the μ-law companding transformation method is mainly studied in the paper.Thirdly, the IPTS method based on Hadamard transform is proposed. The improved measure is that every subblock sequence is multiplied by a Hadamard matrix for the Hadamard transform after the input sequence was divided into several sub blocks, and then carried out IFFT. Analysis and simulation show that the improved measure can reduce the PAPR of the PTS-OFDM system. Then the method combining the improved measure with the traditional μ-law companding transformation measure is designed to further improve the PAPR performance of the OFDM system.Finally, the SLM method based on Hadamard transform is proposed. The improved measure is that each group sequence obtained by multiplying the input sequence and random phase sequence is multiplied by a Hadamard matrix for the Hadamard transform, and then carried out IFFT. Analysis and simulation show that the improved measure can reduce the PAPR of the SLM-OFDM system. Then the method combining the improved measure with the novel μ-law companding transformation measure is designed to further improve the PAPR performance of the OFDM system.