Fast Algorithm Forreducing Peak-to-Average Power Ratio In OFDM System

With the rapid development of modern society,more and more requirements are put forward for the validity and reliability of the transmission of audio and video signals.Orthogonal Frequency Division Mutiplexing(OFDM)has been widely applied to mobile communications as it has good anti-mutipath fading ability,higher spectral and data transimission efficiency,which becomes the core technology of many communication standards.However,its application are limited by the critical practical problem of high peak-to-average power ratio(PAPR)of OFDM signal due to the use of multi-carrier modulation,which lead ing to the nonlinear distortion of the signal,and deteriorate the bit error rate performance.For this reason,PAPR is a problem that could not be ignored in OFDM.Therefore,how to effectively reduce PAPR of input OFDM signal becomes an important research topic.In this paper,we mainly study the low complexity of the PAPR joint reduction method,the specific work is as follows:(1)Firstly,this paper introduce the basic principal as well as advantages and disadvantages about OFDM system and three techniques for reducing PAPR of OFDM system: coding,amplitude limit,and probability technology.The advantages and disadvantages of the three techniques are analyzed by theory andsimulation.(2)The probability class technogy is widely used because of its merit of not increasing the BER compared with the probability class technology and lower computational complexity compared with coding technology.In this article,we make an in-depth study about SLM and PTS.PTS algorithm can greatly optimize PAPR performance,but it also cause higher computational complexity,we propose an Improved Partial Transmit Sequence algorithm(IPTS)with only two phase factor :0 and 1,while the number of iterations is equal to the number of sub-blocks.And then we propose the combination Subblocks Interleaving(SI)with IPTS algorithm,which performs a specific interleaving process for the divided sub-blocks of the input sequence to lower its relevance and then makes IPTS operation.Simulation result shows that the SI-PTS can efficiently reduce the PAPR of OFDM system and meanwhile significantly reduces the computational complexity without degrading the BER performance of the system.(3)SLM algorithm can greatly optimize PAPR performance,but it also cause higher computational complexity.So,we propose a Block Selected Mapping algorithm(BSLM),which divde original frequency domain sequence into V sub-sequence and then makes SLM operation for each sub-block.Then we propose an cascade combination Discrete Cosine Transform(DCT)with BSLM algorithm(DB-SLM)that we get two kinds of programs according to the cascade order:one is processing signal by BSLM and then conducting DCTtransformation,the other is inverse order.We can get the optimal cascade order by analyzing the performance differences between the two programs.Simulation result shows that the first program has the best optimized PAPR performance,and in any cascade order,the DB-SLM can more effectively reduce the PAPR of OFDM system and meantime it can significantly reduce computational complexity.