| OFDM (orthogonal frequency division multiplexing) is a parallel transmission scheme of MCM (Multi-Carriers Modulation). It transmits information through orthogonal multiple sub-carriers and has high utilization of frequency spectrum, good capability of countering mutli-path interference. It is also adaptive to high-rate data transmission and multimedia data transmission. This technology has been regarded as the core technology of 4G wireless communication system in the future. However, it has high peak-to-average power ratio (PAPR), which is its inherent disadvantage. This disadvantage in OFDM systems has limited OFDM'S wide applications and has not been solved yet. This paper has mainly researched on the methods of PAPR reduction for OFDM and has obtained some results by MATLAB simulations.At present, the reduction of the OFDM signal PAPR algorithm can be summarized in three categories: clipping, coding, probability;This paper introduces the basic OFDM system model, the key technology and its implementation in the discrete Fourier transform, introduced the PAPR of OFDM system definition and discussion of limiting distribution and clipping technology in the category of limiting filtering, the peak windows and offset peak, analyses the technology of the lower value of OFDM signal PAPR capacity. In the coding technologies, the main complementary sequence analysis Gray and Reed-Muller code, through simulation of the OFDM signal coding method PAPR value of its control in the 3dB below capacity. In the probability technology, the main analysis of the selected mapping(SLM) method and partial transmit sequences(PTS), the simulation that the SLM and the PTS system to reduce the PARP have a good improvement. Finally presents a limiting filtering algorithm to reduce the SLM OFDM system PAPR. The result of simulation shows that the PAPR of the OFDM is decreased,In order to reduce the large computation complexity of PTS an improved method has been analyzed and compared with customary PTS via computer. |
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