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OFDM (Orthogonal frequency division multiplexing) is a parallel multi-carrier transmission scheme, which utilizes a plurality of subcarriers are orthogonal to each other to transmit information, and has good resistance to multipath interference. , OFDM technology has been successfully applied to digital audio broadcasting (Digital Audio Broadcasting, DAB), Digital Video Broadcasting (Digital Video Broadcasting DVB), wireless LAN (Wireless Local Area Network, WLAN), and the high rate data transmission system. However, one of the main disadvantages of OFDM is the peak-to-average power ratio (Peak-to-Average-Power Ratio, PAPR) higher, which requires a highly linear amplifier system and requires a large dynamic range in order to avoid the transmission signal of the non- linear distortion and spectral diffusion, which will increase the cost and difficulty. Therefore, the use of appropriate technology to reduce the PAPR of the OFDM system is very important. Firstly, on the basis of the introduction of the OFDM technology theory, focuses on three main types of technology to reduce the peak to average power ratio (PAPR): signal pre-distortion technology (limiting and compression and expansion technology), signal coding techniques (Golay complementary sequence Read -Muller encoding and decoding algorithms) and signal scrambler technology (selective mapping technology and part of the transmission sequence technology). There are some limitations, but these techniques at home and abroad has not yet been a technology that can reduce the PAPR, to reduce the computational complexity and the amount of computation to improve system performance achieved very good results. Secondly, for reducing PAPR this problem Expand research, we propose two new methods to reduce the PAPR: The first is a series pseudo-random segmentation factor trellis search method factor trellis search of a variable constraint length LC showing a different performance in reducing the peak to average power ratio, which helps to find a good compromise between complexity and performance, and in series with the introduction of pseudo-random segmentation method to improve the PAPR reduction performance; second is based on pseudo-random segmentation improved double-search method, this optimization method is done on the basis of the double-search method improved full search of the original double-search method first layer group to sub-optimal search, and the use of pseudo- random segmentation method, which reduces the complexity of the double-search method, and effectively reduce the PAPR of OFDM system. These two new methods to effectively reduce the PAPR of the OFDM system, and reduces the computational complexity of the PTS method. Finally, this paper summarizes the future prospect.
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