Research On OFDM Multi-Carrier Modulation Technology For Peak-to-Average Power Ratio Reduction

As special Multi-Carrier Modulation (MCM) technology, Orthogonal Frequency Division Multiplexing (OFDM) is quite competitive in the field of integrated wireless access. It has many strengths, such as the strong ability to resist Inter symbol Interference (ISI), the high rate of spectrum usage efficiency. Moreover, it can transmit data at a high speed in the frequency selective fading channel. However, one problem of OFDM lies in the big Peak-to-Average Power Ratio (PAPR), which leads to intermodulation distortion of OFDM signals and degradation of systematic functions. This restricts the wide application of OFDM. Therefore, it is an urgent problem to reduce PAPR in OFDM effectively, which is the focus of this paper.First, this paper introduces the fundamental principles of OFDM, the principal technology, the definition and distribution of PAPR at the beginning. Then, the domestic and foreign technology of reducing PAPR is analyzed, discussed and simulatively compared and contrasted. The strength and the weakness of each method and their applicable occasions are pointed out, which are the foundation of the application.Next, based on the thorough research of coding method and Selective Mapping (SLM), a method which combines code with SLM is put forward to reduce PAPR. This method can be regarded as an improvement on SLM method. The detailed encode and decode scheme, side information transmission scheme and principle model of SLM improvement are discussed in the paper. Compared with the conventional SLM method, the improved SLM can reduce Bit Error Rate (BER) of the Rayleigh multipath fading channel effectively without the degradation of the systematic functions. Furthermore, the systematic data rate will not reduce because the transmission of side information does not need spectrum resource. Then, this paper puts forward a level cycle iterative PTS algorithm of presetted threshold, an improvement on PTS algorithm, which is aimed at solving the problem of the high complexity of the optimal PTS algorithm. The improved PTS algorithm will enhance the systematic functions through threshold control technology and level cycle iterative algorithm. An optimal phase weighting factor is obtained in the every level cycle...