Research And Implementation Of PAPR Reduction Technology In OFDM System

Orthogonal Frequency Division Multiplexing (OFDM) is a parallel transmission scheme of MCM (Multi-Carriers Modulation). It transmits information through orthogonal sub-carriers and has very high utilization of frequency spectrum and good capability of countering multi-path interference. This technology is very fit to the transmission of high rate and broadband data transmiting system. However, the high peak-to-average power ratio is always one of the main drawbacks of OFDM. This paper mainly focuses on the analysis of the PAPR reduction algorithms, inclding RCF, ACE, companding, SLM and TR, and then designed a PAPR scheme based on the algorithms analyzed above and meet the requirements of the datalink system, then implemented in FPGA.The paper firstly introduces the basic principle of OFDM system, analysis the causes of high PAPR in OFDM system, and its impact on system performance. We briefly introduces existing PAPR reduction algorithms, including pre-distorted algorithms, probability algorithms, coding algorithms, and make a simple comparison between them.The paper analyzes clipping algorithm, which is most commonly used. Because of the serious deterioration of the bit error ratio induced by the clipping noise introduced by the non-linearly operation of the algorithm, this paper analyzes two clipping-noise estimation algorithms, which will improve the performance significantly when combined with the clipping algorithms according to the Matlab simulation result. Secondly, this paper analyzes a reduction method called Active Constellation Extension (ACE). According to the Matlab simulation result, the method is proven to be a perfect PAPR reduction scheme which have good PAPR and BER performance when it applies the algorithms of POCS and SGP. But it is harder than RCF to implement.Thirdly, the paper analyzes the conventional companding method and a improved companding method, According to the Matlab simulation result, the companding method is proven to be a good reduction scheme but BER performance is poor. Then, The paper also analyzes the performance of SLM and TR. According to the Matlab simulation result, they have perfect PAPR performance and BER performance, but their implementation complexity is too high.After the analysis of the algorithms mentioned above, this paper introduces the datalink system. Based on the parameters of a OFDM datalink system, we designed an OFDM PAPR scheme. This scheme is easy to implement in FPGA and have good PAPR performance. The proposed scheme is based on the RCF algorithm.At last, the designed scheme based on the algorithms analyzed above, which will be implemented in FPGA later, and gives the running results in FPGA of the designed system, the results shows perfect performance.