Research And Implementation Of PAPR Suppressing Technology In OFDM System

Orthogonal frequency division multiplexing(OFDM)has been widely used in wireless communications,with the advantage of high spectrum efficiency,the ability of anti-multipath fading and supports multi-user access.Though,there are many drawbacks of OFDM systems,such as the high peak-to-average power ratio(PAPR)and the sensitivity to the frequency offset.When the signal passes through the power amplifier(HPA),it will produce the nonlinear distortion problem,and reduce the overall performance of the communications.Therefore,how to solve the problem of the peak value become a key of OFDM technology widely used.Nowadays,there are three main categories to suppress the peak value: signal distortion,coding and probability method.Probability method gets more attention owing to the perspective of lower probability of peak value.The paper is focused on the PAPR reduction algorithms based on Tone reservation and Tone injection.Aimed at the disadvantages of requiring many iterations to offset the multiple peaks for the traditional TR algorithm,the main idea of the proposed TR is to generate parallel peak offset signals that come from the IFFT operations of TR subcarriers,with a series of weighted values formed by the Tone reservation subcarriers.The each offset signal is used to neutralize peak point on the special location.The paper proposed a new method on the basis of existing algorithm.The improvement of the method is change the way of selecting the reserved subcarriers that select the fixed position carrier.The improved peak cancellation signal has better convergence,superimposed on the original signal,can reduce the impact on the peak of adjacent sampling point value.Simulation verified the effectiveness of the proposed method,and promoted the PAPR reduction performance about 3d B gain,without increase the complexity of the computation.On the basis of the traditional tone injection(TI)technique,owing to the traditional constellation extension methods brought about by the high computing complexity and increase the problem of transmitting energy and required a lotof iteration computation to found the best signal in the peak frequency domain in Tone Reservation methods.The paper proposes a joint TRand TI algorithm that data carrier for constellation extension,reserved data offset the peak signal.Simulation results show that proposed algorithm obtained about 1 d B than traditional TR algorithm,and about 2 d B than the traditional TI algorithm.In addition,the paper come up with a method that expand the partial the reference to join direct current bias method in optical communication,can reduce the PAPR of the system significantly when add the DC to the signal wave,but this means decrease the power utilization.Last,the paper introduced the hardware implementation using Vivado software,and the Verilog Hardware Description Language,Through the simulation software ISIM and Model SIM,and the simulation result show the validity of the each module.