Research On Reducing Peak - To - Average Ratio Of OFDM System Based On Selective Mapping

Orthogonal Frequency Division Multiplexing (OFDM) is a special technology of multi-carrier modulation, which has many advantages including high spectral efficiency, flexibility in the allocation of spectrum resources, anti-multipath fading ability, bandwidth scalability and simple hardware implementation. Today has been a large number of communication standards as the core technology, especially to determine its next-generation mobile communication standard is one of the core technologies. It has been adopted by a number of communication standards, and has been used as the core technology for Long Term Evolution (LTE) and the fourth generation mobile communication systems. Using a method of parallel transmission for orthogonal carrier, the technology has two major drawbacks:high Peak to Average Power Ratio (PAPR) and sensitive to the frequency offset. This paper mainly focuses on researching a algorithm for reducing the PAPR of OFDM system. Generally, the method of reducing PAPR of OFDM system mainly includes three categories:distortion, encoding and probability. This paper puts emphasis on studying the selection mapping method from probability category. In addition, a matlab simulation platform is established for simulation.analysis of the algorithms.This paper discourse an improved algorithm based on the selection mapping method, which has shortcomings of occupying additional bandwidth for transmitting side information. Using the technology of blocking and displacing, the improved algorithm sets side information embedded in specific data block, thus reducing the PAPR effectively. Meanwhile, this algorithm needs no additional bandwidth to transmit side information, so the spectrum efficiency is improved.For the improved algorithm bring the decline on BER, based on the improved algorithm, this paper discourse an optimization algorithm. This optimization use reserved subcarriers as the mark, and verified the effect through software simulation. The optimization algorithm does not give any system BRE loss, but also has good effect on PAPR suppression.