Research On Interference Analysis And Suppression Technology Of F-OFDM System

Filtered-Orthogonal Frequency Division Multiplexing(f-OFDM)is an ideal waveform for next-generation mobile communication technology.Although it has many advantages over conventional Orthogonal Frequency Division Multiplexing(OFDM)systems,it introduces inevitable intrinsic interference due to its non-orthogonality filtering nature.Coupled with the influence of various factors such as asynchronous transmission,different subband configurations,and non-ideal synchronization factors,the interference analysis of f-OFDM system becomes more complex.Therefore,in this paper,the uplink f-OFDM systems are studied.Specially,an in-depth interference analysis is made,and several effective interference suppression methods are proposed.Firstly,a systematic and thorough interference analysis of uplink f-OFDM systems in the non-ideal synchronization case is carried out,and extended to the case where the subcarrier spacing(SCS)is a non-integer multiple relationship.In addition,the interference of phase noise is added.Then,accurate closed-form expressions of sub-interferences are derived and verified.Based on these expressions,this paper analyzes the out-of-band emission(OOBE),symbol error ratio(SER)and peak to average power ratio performance of the system with different SCS ratios,so as to provide a reference for the reasonable configuration of subband parameters of f-OFDM system.Secondly,the OOBE precoding and filter design in the f-OFDM system are studied.The derivation method of subcarrier spectrum expression is improved,and it is used for the design of cancellation carriers(CCs)and CCs Cover.Additionally,nonlinear CCs and CCs Cover are extended to linear CCs and CCs Cover using precoding matrix,and the consistency of their performance is demonstrated.After that,statistical linear cancellation carriers(CCs SL)and CCs Cover SL are further proposed to avoid real-time optimization operations,which reduce the complexity while suppressing OOBE.Afterwards,CCs SL and CCs Cover SL are optimized,which reduce the order of the precoding matrix.The results show that only a lower matrix order is required to achieve a more desirable interference suppression effect.In the end,the OOBE precoding and filter design are combined.By applying the designed filter,it is possible to reduce not only the interference of the adjacent subbands,but also the interference in this subband,thus improving the system performance.Finally,the anti-interference joint precoding in the f-OFDM system is studied.The optimization model is established by combining OOBE precoding with inter-carrier interference(ICI)precoding.The successive convex approximation algorithm is used to design the precoding matrix.Moreover,the differential decoding method is used to detect,and the results show that the joint precoding method can further reduce the SER performance and suppress OOBE effectively compared to OOBE precoding.