Reduceing Papr Of OFDM System Based On SLM And Constellation Mapping

As the rapid development in wireless communication, higher data transmission was required in many services. The conventional communication system with single carrier is hard to meet the desired performance of the system. Because of its good performance on anti multi-path interference and optimum spectrum efficiency, Orthogonal Frequency Division Multiplexing (OFDM) is regarded as the key technology of the physical layer in the next generation mobile communication system. However, a major drawback of OFDM technology is its high Peak-to-Average Power Ratio (PAPR), which severely deteriorates the performance of systems. So, how to effectively reduce the higher PAPR of the OFDM signals is rather an important issue. In the thesis, the research is mainly around this problem, especially discussed the Selective Mapping and Constellation Mapping.In the dissertation, firstly, the OFDM system including some fundamental theories and its key technologies are introduced. Secondly, the definition and distribution of PAPR is presented, so as to the cause of the high PAPR. The paper summarizes the most popular three kinds of PAPR reducing techniques, including predistortion technique, coding technique and probability technique. Thirdly, the PAPR reductions including Selective Mapping (SLM) and Constellation Mapping (CLM) are reviewed in detail. Based on conventional SLM, improved SLM is discussed, which has better performance than the old one at the same threshold. Constellation Mapping, which has recovered the data effectively at the receiver, is superior to the amplitude limiting method. Finally, one PAPR reduction method which combines the probability and amplitude limiting method is proposed as the new scheme. The calculated amount of the improved SLM is inferior to the traditional SLM at the same or similar characteristics in probability and statistics. At the same limiting threshold, the effective data recovery is made at the receiver of constellation mapping method, so the BER performance is superior to the hard limiting method. The whole system's performance of combination between improved SLM and constellation mapping is better than that of traditional SLM and amplitude limiting method.