Research On Reducing The PAPR Of Signal In MC-CDMA System

Multi-carrier code division multiple access (MC-CDMA) technology is a multi-carrier modulation technique that effectively combines the advantages of OFDM and CDMA, which can against ISI effectively and has the effect of frequency diversity. However, it also inherited many shortcomings of multi-system. The high Peak-to-Average Power Ratio (PAPR) is one of the major drawbacks of MC-CDMA system. In order to obtain a better performance, this paper studies a variety of methods to reduce the PAPR and proposes an improved algorithm.Chapter 2 introduces several multi-carrier modulation techniques. Based on the analysis of principle and signal expression,it describes the advantage and disadvantage of these different kinds of multi-carrier modulation scheme. In particular, it emphasizes on the study of MC-CDMA scheme.In Chapter 3, firstly it gives the definition of how to calculate the PAPR signal, and then makes an explanation to the harmfulness of the high PAPR. Finally, it makes a comparison between the PAPR and other different spreading codes.In chapter 4, it focuses on analyzing three typical algorithms: the selected mapping (SLM), the partial transmit sequence (PTS) and the tone reservation (TR). Also it analyzes the principles of the three algorithms specifically and does the simulation for these algorithms individually based on the MC-CDMA models. According to the result of MATLAB figures, it can be concluded that parameters have impact on system performance. Simultaneously Iteration algorithm makes a compromise between performance and complexity.Chapter 5 proposes two improved algorithm schemes: one is using the threshold to limit the calculation number of loop and then reduce the unnecessary counts; the other is PTS-TR algorithm, which effectively combines PTS and TR. At the same time the simulation shows that using the algorithm of PTS-TR can obtain a better performance of reducing the PAPR instead of reducing the performance of PAPR by solo parameters.In the end of the paper, it makes a general summary and indicates the direction of future research.