Performance Analysis of Peak to Average Power Ratio Reduction by Clipping in OFDMA System

• Main Authors: JHANG, JYUN-JIA, 張峻嘉
• Other Authors: LIU, WEI-CHENG
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/fgvmb9

碩士 === 國立中正大學 === 通訊工程研究所 === 106 === An orthogonal frequency division multiple access (OFDMA) signal is linearly combined by many modulated subcarriers, so it may cause high value of peak-to- average power ratio (PAPR). Theoretically, PAPR is equal to the number of subcarriers when modulated subcarriers are added with the same phase. High value of PAPR is a major drawback in OFDMA system. Main problems are as follows: 1. The complexity of analog-to-digital converter (ADC) and digital-to-analog converter (DAC). 2. Radio frequency power amplifier performance degradation. There are many techniques for PAPR reduction, but the algorithm complexity is enhanced with the number of subcarriers increasing. However, the clipping technique keeps two advantages as follows: 1. No loss of data rate. 2. With the number of subcarriers increasing, the algorithm complexity is the same. In this paper, we analyze the effect of clipping on PAPR in OFDMA system downlink by oversampling the OFDMA baseband signal to increase the number of sampling points, and then use clipping to reduce the PAPR. But the signal would be distorted by clipping, resulting in spectrum leakage. Therefore, we use the low-pass filter (LPF) to remove out-of- band radiation at transmitter. We simulate the multipath fading channel plus additive white Gaussian noise (AWGN). Due to the fact that OFDMA inherits the advantage of orthogonal frequency-division multiplexing (OFDM), we can use cyclic prefix and minimum mean square error (MMSE) equalizer to compensate channel distortion and analyze the system performance.