Research Of Peak-to-Average Power Ratio Reduction Technology On Multi-Carrier System With Index Modulation

Subcarrier index modulation(SIM)orthogonal frequency division multiplexing(OFDM)is a new type of modulation technique that has better peak-to-average ratio(PAPR)characteristics than the traditional OFDM signal.In addition,due to sparse structure of subcarrier allocation,it has better transmission performance in low-rate,high signal-to-noise ratio scenarios.Therefore,this scheme has a good application prospect in low-energy,low-rate communication scenarios such as narrow band internet of things(NB-IoT),LTE enhanced machine-type communication(LTE eMTC)and long range radio(LoRa).However,SIM-OFDM still has a certain amplitude fluctuation problem especially the number of activated subcarriers is large.Therefore,how to utilize the traditional algorithm to further reduce PAPR of SIM-OFDM while explore improvement of amplifier working efficiency is the main contents of thesis.In thesis,the peak-to-average ratio problem of SIM-OFDM systems and low-PAPR transmission schemes are studied,which are divided into distortion-less PAPR reduction methods and pre-distortion PAPR reduction methods.The structure of thesis is as follows:Firstly,the basic principles of OFDM and SIM-OFDM are introduced.The performance of PAPR and transmission performance in OFDM and SIM-OFDM are compared.Then,the typical distortion-less and pre-distortion PAPR reduction algorithms named clipping and partial transmission sequences are introduced.We point out the advantages of SIM-OFDM by comparing the performance of PAPR and transmission performance with traditional OFDM.Secondly,the improved partial transmission sequence algorithm of the three partial transmission sequence grouping methods in SIM-OFDM is studied.Based on grouping method,candidate signal generation and side information transmission,a series of improved algorithms are proposed.At first,the correlation between the candidate signals in the partial transmission sequence is analyzed.According to grouping inhomogeneity problem existing in traditional grouping mode,a partial transmission sequence grouping method based on subcarrier block is proposed which can achieve a better PAPR reduction performance.Then,a new candidate signal generation method based on cyclic shift is proposed.By cyclic shift in the subcarrier block,the possibility of generating a low PAPR signal is increased,and the performance of PAPR is improved without increasing the number of candidate signals.Finally,a new method of side information based on embedded pilot is proposed,which improves the transmission performance of side information.Finally,we firstly analyzes the influence of nonlinear distortion caused by amplifier in OFDM and SIM-OFDM.Then,a clipping threshold optimization algorithm and a nonlinear distortion compensation method are proposed.For the nonlinear noise caused by clipping and amplifier,the threshold is selected with the minimum mean square error of nonlinear noise,which can balance the distortion between clipping and amplifier.For the phase distortion from the amplifier,the phase of clipped signal is compensated by a given clipping threshold in order to mitigate phase distortion of the received signal on the system.