The Research And Performance Simulation Of OFDM Communication System To Reduce PAPR

With the rapid development of wireless communication technology, various new communication services need urgently for real-time wireless networks providing high-speed data transmission. For its excellent anti-multi-path performance and efficient spectrum utilization, orthogonal frequency division multiplexing (OFDM) technology has been widely used in ADSL, HDTV, and WLAN and many other fields, and people have given more and more attention on it. It will become one of several core technologies on the next-generation mobile communication system. Also the OFDM technology will be continuous developmented and improvemented from theory to practical application of the process. OFDM technology divides the channel into multiple sub-channel with orthogonal subcarriers. In such circumstance of making sub-channel spectrum overlap with each other, you can still demodulate transmit signals. It greatly saves bandwidth. However, OFDM system has a inherent shortcoming of high peak to average power ratio, which requires A/D converter and power amplifier to have a very wide linear operating range. This will result in energy waste and increase the cost of the equipment. And it is also one of the principal problems to restrict OFDM technology to practice. Therefore, it is necessary to control the PAPR of the OFDM signal.This paper studies the issue of PAPR in OFDM systems. First it describs the basic principle and key technologies of OFDM system; second it analyses of the various methods to reduce the peak to average power ratio of OFDM signal, which mainly includes the pre-distortion techniques, coding techniques and the probability techniques. This article focuses on the probability techniques, including selective mapping method (SLM) and partial transmit sequence method (PTS). For the problem of the traditional high complexity for the traditional algorithms, this paper presents two kinds of new improved algorithm to reduce PAPR in OFDM system:the improved SLM algorithm and the improved PTS algorithm. The improved SLM algorithm scrambles code after the original data sub-group, takes use of the linear nature of Fourier transform, and gets the new scrambling code sequence with the IFFT of the data acquired sequence by a linear combination, so controls of IFFT number strictly, at the same time to get more alternative time domain data sequence.The improved PTS algorithm finds of a new phase factor search rules based on the sub-optimal iterative algorithm, and searchs stratified loop iteration of the sub-optimal phase factor.The simulation results show that both the improved algorithm can significantly reduced the computational complexity of the system and on the same time can achieve similar PAPR performance with the traditional algorithms, and verify its feasibility.