Imaginary Interference Cancellation On FBMC/OQAM Signals

Filter bank multicarrier with offset quadrature amplitude modulation(FBMC/OQAM)exhibits higher spectral efficiency,lower out of band emission compared to the classic orthogonal frequency division multiplexing(OFDM)system due to the employment prototype filters with good time and frequency localization.However,the prototype filters only satisfy real-filed orthogonality conditions,which results in intrinsic interference among FBMC/OQAM symbols.The existence of imaginary not only complicates the signal Processing tasks,i.e.,channel estimation,equalization and synchronization,in the receiver,but also makes it infeasible for the direct transmission of complex-valued symbols.Furthermore,it leads to the maladjustment of FB MC/OQAM to multi-input and multi-output(MIMO)techniques,which are widely adopted in the fifth generation(5G)mobile communication systems.This thesis aims to eliminate the imaginary interference,and increase the transmission accuracy in FBMC/OQAM system,without losing spectral efficiency and increasing out-of-band emission(OOBE).In this thesis,the influential factors to imaginary interference are firstly analyzed and the symmetry property of imaginary interference is proven,which indicates that the amplitude of imaginary interference only depends on the prototype filter and the relative time-frequency positions among symbols,and the parity of symbol time indexes result in a reverse phase to imaginary interference.Then,the frame repetition techniques are proposed for self-interference cancellation on pilots,which cuts down pilot overheads and brings a promotion to channel estimation performance in FBMC/OQAM system.Furthermore,a complex-valued symbol based FBMC/OQAM system(C-FBMC/OQAM)is proposed for imaginary interference cancellation on data symbols.Theoretical analyses and simulations validate that the proposed schemes effectively eliminate imaginary interference and fights against frequency selectivity without sacrificing spectral efficie ncy or increasing out-of-band emission.Finally,to settle the maladjustment of FBMC/OQAM to multi-input and multi-output(MIMO)scenarios caused by imaginary interference,improved Alamouti encoding and singular value decomposition precoding schemes are proposed in MIMO scenario based on the C-FBMC/OQAM system,in which imaginary interference are mitigated without bringing in performance loss or computation complexity.In conclusion,in this thesis,frame repetition based techniques are proposed to eliminate the imaginary interference in FBMC/OQAM system,which effectively eliminates imaginary interference and fights against frequency selectivity without sacrificing spectral efficiency or increasing out-of-band emission.