Application And Performance Research Of Carrier Scheme Fusion Mechanism Based On WFRFT

With the rapid development of information technology,demands for next-generation communication systems not only focus on the increase of peak rate,but also pursue higher reliability as well as lower latency in complex scenes and environments,lower terminal power consumption and massive access of users.Moreover,as a result of more transmitted information,spectrum resources are increasingly scarce.Therefore,more research focuses on improving spectrum efficiency and using fragmented spectrum resources effectively.However,traditional waveforms based on Orthogonal Frequency Division Multiplexing(OFDM)systems can not solve these problems absolutely.On one hand,OFDM systems are susceptible to carrier frequency offset(CFO)and Doppler shift with a high peak-toaverage power ratio(PAPR).Additionally,flexible configurations could not be achieved when requirements change due to the switch between multiple scenes.On the other hand,the out of band power(OOBP)emission is high due to slowly attenuating sidelobes,which requires large guard intervals to suppress interference between frequency bands,and thus the spectrum efficiency is reduced.Therefore,candidate waveforms for future scenes,environments and requirements are put forward,such as Generalized Frequency Division Multiplexing(GFDM)and Filtered OFDM(F-OFDM)systems,which achieve lower out of band power radiation and stronger robustness against complex scenes.In this paper,we study hybrid carrier(HC)and Weighted-type Fractional Fourier Transform(WFRFT)precoded GFDM systems.The fusion mechanism of single carrier(SC)and multicarrier(MC)schemes is elaborated,and then employed to study performances of HC and WFRFT precoded GFDM systems in time-frequency mismatch scenarios.Firstly,we investigate the fusion feature of hybrid carrier systems based on WFRFT for Single Carrier with Frequency Domain Equalization(SC-FDE)and OFDM systems.The single carrier components and multicarrier components contained in HC systems are quantitatively calculated.The weighted ways of hybrid carrier fusion mechanism is elaborated.We give the weighted objects for the ZF/MMSE equalization criterion,and derive theoretical BER expressions of HC systems with linear equalization.Furthermore,the practicability and extensiveness of hybrid carrier fusion mechanism are studied.We also derive theoretical BER expressions of HC systems with space-time block coding and power allocation,and put forward MMSE power allocation in HC systems.Secondly,the equivalence of OOBP performance in OFDM,HC and SC systems is proven.Moreover,we illustrate two kinds of OOBP suppression techniques for HC systems,i.e.time domain windowing and spectrum precoding.On one hand,a joint OOBP and PAPR suppression method is studied in HC systems through time domain windowing and frequency domain pulse shaping.On the other hand,projection precoder and singular value decomposition precoder are both introduced to reduce OOBP of HC systems.When two kinds of methods are employed in HC systems,better BER and PAPR performances are obtained in HC systems in comparison with OFDM systems.As a result of smaller mean square error of projection precoding in HC systems,a WFRFT-based projection precoder of pilot signals is presented.Thirdly,GFDM systems also have characteristics of ”hybrid carriers”.In order to combine advantages of WFRFT precoding and GFDM systems,we study performances of WFRFT precoded GFDM systems.The GFDM and Discrete Fourier Transform(DFT)precoded GFDM systems are merged in WFRFT precoded GFDM systems.We elaborate weighted way of carrier scheme fusion mechanism in WFRFT precoded GFDM systems,and derive theoretical BER expressions with ZF/MMSE receivers.In addition,the theoretical BER expressions of WFRFT precoded space-time block coded GFDM systems are also derived.Furthermore,taking noise enhancement factor as the optimization target,the minimum BER power allocation method of space-time block coded GFDM systems is proposed,which improves BER and achievable rate performances simultaneously.Finally,we study BER performances of HC and WFRFT precoded GFDM systems in time-frequency mismatch scenarios.Basically,we derive theoretical BER expressions of HC systems with CFO or TO,as well as theoretical BER expressions of WFRFT precoded GFDM systems with TO.The proposed theoretical research could effectively simplify the BER evaluation process of different carrier schemes in different scenarios,and lay the foundation for optimal order selection problems in WFRFT precoded systems.When TO and insufficient cyclic prefix appear,the BER performances of OFDM and GFDM systems could both be improved by WFRFT precoding.