Research On PAPR Reduction And Interference Cancellation Of GFDM Systems

For the past few years,with the improvement of wireless communication technologies,the demand of various mobile digital services is emerging quickly,which requires cellular mobile communications to achieve higher data transmission rate,lower latency,and greater reliability.Generalized Frequency Division Multiplexing is a circularly block-based non-orthogonal multi-carrier transmission scheme,which has advantages of high time-frequency localization,low sensitivity in carrier frequency offset and timing error,high flexibility in resource scheduling,and strong versatility.It meets the needs of the next generation of mobile communications technology.However,similarly to conventional multi-carrier systems,GFDM suffers from high PAPR problem.Meanwhile,as a non-orthogonal system,the inner interference might degrade the performance.Therefore,the research on PAPR reduction and interference cancellation of GFDM systems become a hot spot of research in both domestic and overseas.The main work and innovations of this paper are as follows:Firstly,exact closed-form expressions of CCDF for the PAPR of critical/over sampled GFDM signals are firstly derived,which tends to be sufficiently accurate as the number of subcarriers is large enough(e.g.K>64).It facilitates the evaluation of PAPR distribution characteristics of GFDM signals.Additionally,this expression is a generalized approximation for PAPR distributions of other multicarrier signals(e.g.OFDM,FBMC/OQAM).These expressions provide crucial guidance for PAPR properties analysis and PAPR reduction method in GFDM systems.Secondly,the optimization problem of pulse shaping filter design in terms of minimizing the CCDF of PAPR is formulated and analyzed thoroughly.With the aid of the above theoretical CCDF results,two locally optimal solutions for this optimization problem are obtained,and one of them,which is more appropriate for practical applications,is regarded as the optimization criterion.Based on this criterion,we provide a measurement,which is adapted to evaluate the ability of PAPR reduction for filter candidates efficiently.The preferred solution is proved to be the globally optimal solution for the problem of minimizing the variance of instantaneous power(VIP).Additionally,we analyze and demonstrate the compatibility of the proposed criterion with the other existing optimization criterions for pulse shaping filter design.The optimization criterion and the PAPR measurement method show great importance for the filter design in practical applications.Thirdly,based on the proposed CCDF results,we provide more comprehensive comparison results of PAPR distributions among common multicarrier systems,helping to learn PAPR distribution properties more clearly and guide practical applications.Fourthly,two new nonlinear companding algorithms are proposed to reduce PAPR in GFDM.We also propose an iterative reception method to solve the problem of limitated range of input signals during de-companding operations,and eliminate the signal distortions.Compared with existing PAPR reduction schemes,the combination of the proposed companding algorithms and the iterative reception scheme can obtain both better PAPR reduction and BER performance.Finally,based on the odd-even dual filter bank,a modified interference cancellation scheme is proposed.The odd filter and the even filter satisfy the block-interleaving condition with quadruple subsymbol number.This method eliminates the inner interference and maintaining low OOB power leakage simultaneously.The full conclusions and the prospect of the research direction are provided at the end of the article.