The Research Of Peak-to-average Power Ratio Reduction Based On OFDM

Daqing oil field is facing the real problems of wide geographic distribution, peripheraloilfields staff shortages, harsh working environment, high development costs, the oldliberated oilfield facing large scale capacity building and increasing pressure on new labor,safety and environmental protection due to the large oil and gas fields. In2010, creating"digital oilfield" with improving the information management platform, achieving theautomatic data acquisition, process automatic controlling, automatic fault warning and scenevideo surveillance are required by Oilfield Company leadership, digital technology andapplication research, and achieved have currently been completed aiming at the old area ofDaqing, peripheral and alpine areas, and considerable economic benefits are obtained, andit was fitted promotion applies to all oil production plant in Daqing. The information transferrate and bandwidth of the wired transmission mode are unable to meet the demand of thegeneral promotion of the digital oilfield at present, while the4G mobile communicationsystem is faster transmission speed, real-time and bandwidth known can corking meetDaqing digital oilfield construction needs, its core technology is the OFDM(OrthogonalFrequency Division Multiplexing) technology.OFDM technology is a multi-carrier modulation techniques, it has been widely used indigital audio broadcasting, digital video broadcasting and the field of wireless LAN forspectrum efficiency, resistance to multipath interference ability. However, one of the maindrawbacks of OFDM is the high peak-to-average power ratio (PAPR) of the OFDM signal,which requires the power amplifier system, the number of D/A converters and othercomponents have a large enough dynamic range (resulting in low efficiency of thesecomponents), the dynamic range of these components can not meet the requirements, and itwill cause clipping and declining in system communication quality, so a certain technologymust used to reduce PAPR and improve the performance of the OFDM system. For theseissues, the paper focuses on how to effectively reduce the OFDM signal peak to averagepower ratio problem.First, clipping filtering method, companding transform and the matrix transformationmethod of the signal pre-distortion technology are studied in the paper. The impactrelationship of CR with the lower APPR is analysised for clipping filtering method, it isshown that the PAPR performance improvement and system bit error rate performance isconflicting, and we must consider the trade-offs. The companding transform of three iterations is proposed for traditional compression expansion transformation method, thePAPR of the OFDM signal that BER is basically unchanged is significantly reduced by thesystem PAPR and BER performance simulation, and the suppression of the high PAPR ofOFDM system is realized to certain extent. The methed through the matrix transformations toreduce the non-cycle of the data sequence self-correlation is finded according to the cause ofPAPR for the inhibition of the high PAPR of OFDM system. The simulation results is showedthat the matrix transformation method that BER is basically unchanged can effectively reducethe PAPR of the signal value.Secondly, selective mapping (SLM) and partial transmit sequence (PTS) that are the twoalgorithms of signal scrambling techniques are studyed in detail. The improved SLM methedthat matrix transformations is used to replace some of the IFFT transform is proposed for thelarge amount of calculation for the conventional SLM method, and the improved SLMmethod that is verified by simulation can improve the PAPR performance of the system andreduce the computation without increasing the bit error rate. The improved PTS method thatthe weighting factor is getted by using optimization algorithm to seek, the number ofsubcarriers K=128, sub-block segmentation segmentation method divided by the number ofV=8and adjacent is proposed by studying PTS method. The improved PTS method that isverified by simulation can improve the PAPR performance of the system without increasingthe bit error rate.Finally, several joint algorithms is presented to reduce the PAPR performance of theOFDM system in the paper. First, two joint algorithm that is matrix transformation methodcombined with the improved PTS and matrix transformation method combined with theimproved SLM are proposed. The methed through the matrix transformations to reduce thenon-cycle of the data sequence self-correlation can reduce the PAPR performance of theOFDM system without increasing the bit error rate, but the computation is increased by usingthis algorithm. Secondly, two joint algorithm that is clipping method combined with theimproved PTS and clipping method combined with the improved SLM are proposedaccording to the complementary characteristics by the limiting law and the improved PTS andthe improved SLM method performance. The best cascading sequence of the joint algorithmis finded by studying, and the feasibility and effectiveness of the joint algorithm is verifyedby the PAPR performance and BER performance of the joint algorithm simulation. Then, twojoint algorithm that is PTS-CCET and SLM-CCET are proposed according to thecomplementary characteristics by the compression extension transform and the improvedPTS and the improved SLM method performance. The PAPR performance of the OFDMsystem is improved without increasing the bit error rate and the computation.