Algorithm Research On PAPR Reduction Of OFDM System

Along with life more and more reliance on the Internet, the requirements to the variety of high-definition video and image requirements also become more and more high, and to the demand for bandwidth is also growing, therefore, competing for the limited spectrum resources become the focus of the countries. How to transmit the various signal with high-speed has the most problems to be solved. At present, each country is trying to solve this problem and proposed a number of ways. In these methods, Orthogonal Frequency Division Multiplexing (OFDM) is seen as the key technologies of the fourth generation mobile communication. It divided OFDM signal into a plurality of sub-signals to be transmitted and the plurality of sub-signal assigned to each subcarrier superposed on each other, and request each sub-carrier must be strictly orthogonal to each other. However, when the superposed signals are transmitted in the channel, it would produce a high peak to average power ratio (PAPR) when the phase of each subcarrier signal is same at a certain moment which superposed on each other, it will make the BER performance degradation, which is the fatal flaw of the OFDM technology. In this paper the focus of the research is to inhibit the high PAPR of OFDM system.In view of the high PAPR of OFDM system, first of all, the research background and significance of the project work is discussed in this paper, and make a brief analysis of its research status, and it simply describes the development process of OFDM system and its current research situation at home and abroad, analyzed its application value in the society. Then introduces the basic principles of OFDM system and its associated technical problems, at last, this paper discussed the high PAPR of the OFDM system, and for this problem, three traditional algorithms that reduce the high PAPR of OFDM system are introduced briefly, and give the simulation diagram of the various algorithms, through the comparison of the simulation diagram, analyzes the advantages and disadvantages of all kinds of traditional algorithm.This paper made a detailed research about three kinds of improved algorithms, first, it made a deep research about the traditional companding transform method, on the basis of the traditional companding transformation methods, according to the conpanding coefficient μ, iteration compand transform of the OFDM signals, until μ is one, then calculate the PAPR values, the iterative companding transform method is put forward, the the simulation of the traditional algorithm and improved algorithm is made using MATLAB,which demonstrates the improved algorithm on system performance of PAPR with good improvement. Second, it made a deep research about the traditional clipping algorithm, on the basis of it, Set a number of iterations, then deal with the OFDM signal using clipping method when the iterations meet the conditions, the loop iteration of clipping algorithm is put forward. Third, it made a research about the clipping algorithm and the SLM algorithms, made an improvement fusion algorithm. The fusion algorithm is divided into two kinds, first, deals with the OFDM signal using clipping algorithm, and then sends the signal in the SLM system, gets the clipping-SLM fusion algorithm. Second, sends the OFDM signal in the SLM system, and then deals with the signal using clipping algorithm, gets the SLM-clipping fusion algorithm. Then simulate the two fusion algorithm respectively by using MATLAB, simulate the PAPR simulation diagram and BER simulation diagram of the two fusion algorithm.Finally, the simulation of various algorithms is done by using MATLAB. The results data of the simulation is displayed in the form of graphs, which detailed analysis and comparison of the advantages and disadvantages of the improved algorithm compared with the traditional algorithm. Through the analysis of comparative advantages and disadvantages of various methods, that presents a research program with practical application value.