Research On The Algorithms Of Peak-to-average Power Ratio Reduction In OFDM Systems

OFDM (Orthogonal Frequency Division Multiplexing) is considered as a key technology of the next generation mobile communication. It has many advantages, such as the high efficiency of the frequency spectrum utilization and the availability against the multi-path channel. However, one of the disadvantages of the OFDM is the high PAPR (Peak-to-Average Power Ratio). This paper focuses on the algorithms of PAPR reduction in OFDM Systems.This paper introduces the methods and the research status of the PAPR reduction at first. Then the paper discusses on the method of PTS (Partial Transmit Sequences) and several methods of suboptimum PTS. An improved algorithm is presented based on the deep analysis of Kwon's suboptimum PTS. The algorithm is improved by changing the search mode of the phase factors. The method can reduce the complexity of the system while getting better PAPR performance. Combining with Cimini's suboptimum PTS and the thought of dividing into groups a novel method of suboptimum PTS is presented in this paper. The phase factors are divided into several parts. Under other parts unchanged the optimal combination is found in one part, and repeated in others. The final combination of phase factors consists of the optimal combinations of each part. The PAPR performance of this method is close to the optimal PTS, but the amount of calculation is much smaller. This algorithm reduces PAPR by finding the optimal combinations of phase factors in each part. The method of dividing the phase factors is very flexible. The paper discusses this algorithm particularly, and the flow diagram of the method is presented. The performances of reducing PAPR and the amounts of calculation are analyzed and compared when the numbers of phase factors in each part are same or different. Finally,the method is compared with Kwon's suboptimum PTS and Cimini's suboptimum PTS. The emulations show that this algorithm can reduce the PAPR of the OFDM system more effectively at the same amount of calculation.