Research On Reducing Papr Of The OFDM System

Orthogonal frequency division multiplexing (OFDM) with high spectral efficiency and strong anti-multipath fading capability, so we consider it as the fourth generation of mobile communications key technology, but there is so high PAPR in the transmission that reduce the power amplifier's linear region and affect the entire communication system cost and efficiency.In this paper, we give the deep research on OFDM system reducing the RAPR, and analyze the current PAPR reduction of several main algorithms, including limiting amplitude algorithms, coding algorithm and probability algorithm. Moreover,compare with the mentioned algorithm. On this basis, we choose the probability algorithm as the key research.Then, because the selected mapping method is not high spectrum efficiency and lower transmission rate, we suppose an improved algorithm code based on SLM . The detailed encode and decode scheme , side information transmission scheme are discussed in the paper. The proposed scheme can not include the loss of spectrum efficiency by embedding side information within the tranmitted data.Finally, we present the simulation research for PAPR and BER performance , the simulation results of which indicate that the improved SLM algorithm can efficiently reduce the PAPR,and presents a method using completely complementary codes to reduce the complexity of SLM calculation.At last, due to the large amount of computation time, hardware complexity and the shortcomings of low transmission rate code , a sub-optimal transmission sequence algorithm is to take a fixed value of P, then set the threshold of a PAPR,compare PAPR with its corresponding preset threshold value.of course, in the condition of in a fixed V values, the system is calculated according to the signal PAPR from small to large adapt to the values of P, and also get a satisfactory PAPR reduction performance and computational objective as possible. we demonstrate the feasibility of the method by matlab simulation.