Research On Reducing PAPR Techniques For OFDM Wireless Communication System

Orthogonal Frequency Division Multiplexing (OFDM) is an effective and high-speed parallel transmission techniques. It can be successfully used in many high-speed wireless transmission systems for its high spectrum efficiency, anti-multipath fading capability. However, the inherent high Peak-to-Average Power Ratio (PAPR) of OFDM lead to a higher requirement techniques for the non-linear components. If dynamic range of the amplifier can not satisfy the changes of signals, the signals would be distorted, thus the performance of the system would be reduced. Therefore, how to debase the higher PAPR is one of the pivotal problems which OFDM must be resolved.The PAPR reduced techniques in OFDM system is mostly researched in the paper.The mainly contents are as follows:Firstly,the pre-distortion techniques of signals is researched,which primarily includes the clipping techniques and Compressing Transform techniques. Through analysing and simulating these two techniques, the advantages and disadvantages of each algorithm performance are compared. Aiming at the declining of BER performance in C transform compand algorithm, a new ameliorated algorithm is brought forward,which can effectively improve system performance to some extent.Secondly, the Probability Class techniques is studied which includes Selected Mapping (SLM) algorithm and Partial Transmit Sequence (PTS) algorithm. For the problem of high complexity of PTS algorithm, the thought of the sub-optimal iterative searching algorithm is adopted,then two kinds of improved sub-optimal iterative PTS algorithm are put forward.Compared with the PTS algorithm,both of them can reduce the computational complexity on the basis of raising the PAPR inapparently and compared with the sub-optimal iterative algorithm,both of them can debase the PAPR on the basis of improving the complexity inapparently . These two algorithms are considered in compromising of computational complexity and system performance in PTS algorithm in different ways. The new algorithms are proved to be effective and feasible through simulation.Finally,on the basis of the analysis of the pre-distortion techniques of the signal and the Probability Class techniques ,the thought combining the pre-distortion techniques of signal with the Probability Class techniques to debase the PAPR, and two improved of united algorithms are proposed,which are separately called SLM algorithm based on inhibit soft clipping noise, and ameliorated sub-optimal iterative PTS optimize C transformation commanding algorithm. Through simulation analysis, the united algorithm can improve system capability efficiently, relative to a class of simple reduction technique.