Research On Hybrid Papr Reduction Methods In Multi-carrier Systems

In recent years,in order to meet the growing demands of people for communication services,mobile communication technology is also in constant development.Multi-carrier modulation technology uses several subcarriers to carry signals,and it can not only overcome the frequency selective fading,but also realize the high speed of data transmission.OFDM(Orthogonal frequency division multiplexing)technology is one of the multi-carrier modulation technologies,and it greatly improves the spectrum utilization and reduces the mutual interference between subcarriers.So it's widely used in 4G/LTE.However,OFDM system has many shortcomings,which can't meet the development requirements of the future 5G.Due to its advantages of low out-of-band radiation and no synchronization,FBMC-OQAM(Filter Bank Multicarrier with Offset Orthogonal Amplitude Modulation)has received widely attention of the researchers worldwide.High PAPR(Power Ratio Peak-to-Average)is an important problem restricting the development of multi-carrier technology.When the signals on the carriers have similar or the same phase,it will lead to a large peak signal and make it difficule to the signal demodulation,hardware design and realization.The traditional PAPR reduction techniques are generally use one single technique which leads to poor comprehensive performance.Hybrid technologies become the new direction for PAPR reduction technology by organically combining several single techniques.Therefore,this thesis goes into details of PAPR reduction technologies in MCM,and the main research content is as follows:For OFDM systems,the hybrid PAPR reduction technologies that have been proposed always use cascade mode,and the calculated amount is great.Besides,the component of the technologies mostly belongs to predistortion,and it will bring distortion to signals which lead to a poor system performance.According to the disadvantages of the existing hybrid technologies,this thesis proposes a hybrid PAPR reduction technique based on embedded structure,called SeP(SLM embed PTS).The proposed SeP spurns the cascade mode and embeds improved SLM into the optimization of PTS,and reduces the whole calculated amount by integrating the similar steps.Meanwhile,because both the two parts optimize the signal,it improves the performance of PAPR performance.Then,we use MATLAB to verify the SeP.The simulation results show that the proposed SeP technique can effectively reduce the PAPR of OFDM signal.At the same time,compared with the hybrid PAPR reduction technologies which have been put forward,the complexity of the proposed SeP technique is much lower by the use of embedded structure.The existing PAPR reduction techniques for FBMC-OQAM system most directly use the traditional technologies.Because signals have overlapping property,the PAPR performance is very poor.Then,for the FBMC-OQAM system this thesis puts forward a PTS method based on pretreatment,called P-PTS(Pretreated PTS).On the basis of overcoming the overlapping problem,by using a two-step optimized structure design,the method adds a pretreatment to deal with the signals.The performance of PAPR reduction is improved,and because the calculation is dispersed,the total computational complexity is reduced.In addition,different parameter combinations can be used and computational complexity and performance can be traded off flexibly.We simulate the technique with MATLAB.Finally,simulation results show that the proposed P-PTS method can effectively suppress the PAPR of FBMC-OQAM signal,and the BER performance of the system is improved,too.In the end,the thesis summarizes the full text and the future research work is prospected.