The Studies On Prpr Of The OFDM System

Orthogonal frequency division multiplexing (OFDM) is multi-carrier modulation technology. The technology is very suitable for transmission in high-speed communication environment. It has a strong anti-multipath fading and narrowband interference capacity, high spectrum efficiency and it can effectively overcome the inter symbol interference (ISI) and inter channel interference (ICI).But it has peak average power ratio (PAPR) problem. This question easily leads to linear distortion of OFDM signals and system performance degradation. This shortcoming limits the widespread application of OFDM technology. Therefore, how to effectively reduce the PAPR in OFDM system is needed to solve. This article just studies on how to reduce the PAPR of OFDM system.First, the paper introduces the basic principles of OFDM system and its key technology, given the definition of peak to average power ratio and distribution. The paper introduces three existing PAPR reduction techniques. The paper focuses on the selective mapping (SLM) method and partial transmit sequences (PTS) method. By analyzing and comparing three types of technology, point out the advantages and disadvantages and its application respectively. Provide the basis for its practical application.Because of the disadvantages of the selective mapping (SLM) method, this thesis proposes an improved method based on the traditional SLM. The improved method uses m sequence scrambling the OFDM symbols sequence. The option of sequence before the IFFT, therefore improved method only requires only one IFFT module. Thus it reduces the amount of calculation and reduces the complexity of the equipment. The improved method inserts side information into the sequence of information for transmission. Thus it does not transmit side information separately, save bandwidth, improve bandwidth efficiency. Computer simulation and complexity analysis shows that, compared with the improved SLM method and the conventional method is almost no difference in reducing the PAPR and the BER. But the improved method can greatly reduce the complexity of system. It is a good PAPR reduction of OFDM system method.