The Study Of The Key Technologies In The OFDM Modulator

Orthogonal frequency division multiplexing(OFDM)is a multi-carrier modulation technique,because it has a strong resistance to multipath fading and narrowband interference,so it is used more and more widely.However,OFDM has a shortage--there is a higher peak average power ratio(PAPR).However,the existing of some of the ways to reduce the PAPR will bring out-of-band interference or will increase the complexity of the calculation.In order to more effectively reduce PAPR in the OFDM system,this paper has made several improvements based on the existing algorithm,through the analysis of simulation results comparison between the advantages and disadvantages of different algorithms.At first,this paper puts forward the adaptive iterative clipping filtering algorithm,comparing with the traditional clipping algorithms can be concluded that the improved algorithm not only can better reduce the PAPR can effectively reduce out-of-band interference.Based on the two algorithm of probability class:part of the transmission sequence(SLM)and select part of the transmission sequence(PTS)mapping method,in this paper,two algorithms of phase factor weighted process to make improvements,in turn phase symmetry PTS and phase symmetry SLM algorithm is proposed.In order to further reduce the computational complexity of algorithm and introducing the genetic algorithm(GA).Due to genetic algorithm when the optimal value is likely to fall into local optimal solution,so set a threshold value between two adjacent sample to ensure the diversity of samples,so the improved GA-PTS algorithm and GA-SLM algorithm using the advantages of genetic algorithm greatly reduces the complexity of the traditional algorithm.At last,the improved algorithm using MATLAB to do a lot of experiments and analysis,and the improved algorithm is verified on the effect of reducing PAPR and computational complexity of performance ability.