Research On Papr Reduction Techiques In OFDM Systems

With the demand of communication gradually increasing, it has become a development tendency of communication technology to build a high-speed, high-capacity and high spectral efficiency communicated system, which is rightly resolved when Orthogonal Frequency Division Multiplexing (OFDM) system emerges. At the same time, OFDM can fight the problem of frequency-selected fading in wireless transmission environment. But OFDM has its own drawbacks, such as the high Peak-to-Average Power Ratio (PAPR), being the biggest one, which severely affect the practical application of OFDM system. Therefore, it is very significant to study how to decrease the PAPR in OFDM system.Nowadays, the technologies of decreasing the PAPR in OFDM system can be divided into three classes:signal distortion techniques, probability techniques and coding techniques. The first two classes of technologies are mainly studies in the thesis. Clipping method and compression-transform method are simulated and analyzed in the introduction of signal distortion techniques, which have very stable and simple configuration, while the poor performance of bit error rate (BER). On the other hand, three typical algorithms of probability techniques, namely selective mappings (SLM), partial transmit sequences (PTS) and tone reservation (TR), are studied. By properly simulating and contrastively analyzing, probability techniques have the features of the high computation complexity and the undistorted reduction of PAPR in OFDM system, but the problem of side information. Finally, the effectiveness of hybrid of signal distortion techniques and probability techniques are analyzed.Based on the analysis and research of these existing algorithms, two advanced algorithms of fixed-phase sequence are proposed after further deducing the PTS algorithm in the thesis. The two can largely decrease the complexity of system’s structure and computation in slight sacrifice of the performance of PAPR, and offer a good solution to the problem of side information. The effectiveness of our proposed advanced algorithms is justified by the simulations of MATLAB software. Eventually, the hybrid of advanced algorithms without side information and iteration-clipping algorithm is applied into OFDM system, compared with the original hybrid algorithm. It can be observed that the advanced hybrid algorithm could effectively guarantee the performance of BER.