Research On Combined Algorithm Of PAPR Reduction For OFDM System

Since the beginning of the21st century, wireless communication technology ismoving forward at an unprecedented speed. Orthogonal Frequency DivisionMultiplexing (OFMD) is a high speed parallel and multi-carrier transmissiontechnology which has received widespread attention by researchers of wirelesscommunication at home and abroad. Due to its advantages, such as, high spectrumefficiency, good anti-multipath performance and speedy data transmission, OFDM isconsidered to be one of the core technologies of communication system in thenext-generation and an indispensable key technology in the fourth generation of themobile communication system. However, the output signal is formulated byaccumulating a number of sub-carriers, so it is very easy for the output signal to get ahigh peak-to-average power ratio (PAPR), which limits the wide application of thistechnology. The high level of the PAPR puts forward rigorous demands for the linearityof the power amplifier and digital-to-analog converter, and the running cost and powerconsumption of the entire system will be increasing. If the PAPR is too high, it will leadto a non-linear distortion of signal and destroy the orthogonality among sub-carriers,and the receiving end can not correctly restore the signal from the sending end.Therefore, to research the technology of reducing PARA is very necessary.This paper focuses on the research of the technology of reducing the PAPR inOFDM systems. The main contents are listed as follows:First of all, the thesis introduces the development course of the communicationtechnology and the OFDM technology, the technical characteristics of OFDM and thecurrent research status of the methods of reducing the PAPR in OFDM system.Secondly, the paper expounds the basic working principles and key technologies ofthe OFDM technology. And then, the thesis introduces the distribution details of PARAand explains what lead to the high PAPR, in particular, analyzing the existingalgorithms of reducing the PAPR in the OFDM systems. Currently, the algorithm can bedivided into three categories: probability class techniques, coding techniques andpre-distortion techniques. And the author will focus on analyzing and simulating theclipping technology, C transformation commanding algorithm, SLM algorithm and PTSalgorithm of the pre-distortion technology, then proposes two improved methods: SLM algorithm and PTS algorithm.Finally, on the basis of the SLM and PTS algorithm, the author summarizes twojoint algorithms: one is the improved SLM algorithm based on inhibit soft clipping, andthe other is the sub-optimal iterative PTS optimize based on ameliorated Ctransformation commanding algorithm. Both of the two algorithms are confirmed thatthey can effectively reduce the PAPR in OFDM systems under the simulation ofMATLAB software. The two algorithms, on the basis of guaranteeing BER performance,can not only reduce the PAPR of the OFDM systems, but also lower the complexity ofalgorithm.