Study Of The Search Algorithm To Reduce PAPR Of OFDM System

Orthogonal Frequency Division Multiplexing (OFDM) which is one of the key technologies of 4G is a multi-carrier transmission technology, and it is robust to the frequency selective fading channel and has high spectral efficiency. However, because of the high peak-to-average power ratio (PAPR) of the OFDM signals, the OFDM system is limited in the application. There are three kinds of PAPR reduction techniques at present:pre-distorting algorithm, coding algorithm and scrambling algorithm belong to which a algorithm called Partial Transmit Sequences (PTS) is effective to reduce the PAPR, but it is hard to put into effect because of its huge calculation. In this paper, some search algorithms were proposed to reduce the calculation, and MATLAB was used to achieve simulation.Greedy Search Algorithm is simple and easy to implement in the common search algorithm, but it is locally optimal, and hard to search the global optimal solution. Focusing on this question, some modification was proposed. Simulated Annealing Algorithm (SAA) and Genetic Algorithm (GA) have the strong and overall searching ability.In the first part of this paper, OFDM and PAPR are introduced and analyzed, and following introduce several common search algorithm. Then applied the three search algorithms into PTS to search the phase factors, and analyzed the parameters. Simulation with MATLAB shows that using search algorithms to reduce the PAPR of OFDM is effective. At last, the performances and application were analyzed.