Research On PAPR Reduction Algorithm In OFDM Systems

Orthogonal Frequency Division Multiplexing (OFDM) has become one of the key transmission technology in the fourth generation multimedia mobile communication system in the future for its advantages, such as high frequency spectrum efficiency, the ability of combating multi-path fading effectively and eliminating Inter-Symbol Interference (ISI) and so on. And it has been widely used in many areas, such as antenna, navigation, aerospace and so on. However, in OFDM system, the transmission problem is high Peak-to-Average Power Ratio (PAPR), which has higher requirements for the linear range of power amplifier and A/D converter, and even affects the operating cost and efficiency in the whole communication system. Therefore, the research of PAPR reduction technology has theoretical significance and application value.In this paper, the fundamental principle of OFDM system was deeply analyzed, and the implementation process of all the parts and the selection of the OFDM system parameter were introduced. According to the characteristics of the system, the key technologies of OFDM system were expounded, at the same time, the main advantage and disadvantage of the OFDM system were summarized. Focus on the reasons of high peak-to-average power ratio, this paper analyzes its impaction on the system performance. Based on this, various types of the PAPR suppression technology and their traditional algothims were analyzed in detail, which provides theoretic foundation for the new PAPR reduction algorithm.This paper focuses on the research of Selective Mapping (SLM) algorithm. Considering that SLM algorithm needs to send Side Information (SI) additionally, an improved SLM algorithm based on the hidden side information was put forward, in which pilot symbols was inserted at transmitter and the receiver make use of the information carried by pilot symbols itself to acquire the random phase sequence. Thereby, the advantage of the impoved SLM algorithm is avoiding the additional transmission of side information, saving bandwidth resources and inhancing the frequency spectrum efficiency. Then in order to acqire better performance of peak-to-average power ratio, another improved SLM algorithm based on sub-block segmentation was put forward. The proposed algorithm separates the data stream to some sub-blocks by different divided ways, and then optimizes the phase of each sub-block and selects the comibined signals which have the minimum PAPR vale for transmmition. The proposed algorithm expanded the search space of the phase sequence by sub-block segmentation, therefore, the PAPR performance was improved evidently. All the simulation results demonstrate that the two proposed algorithms are efficient, and have the application vale.