Research On Key Problems Of New Multi-carrier Transmission Technology For Wireless Communication Based On Universal Filtering

To cope with the access of massive devices in the future,the multi-carrier transmission technology,which is a key link of the wireless communication system,needs to support the needs of different services such as small packet data communication,low-latency communication,and fragmented spectrum access.Orthogonal Frequency Division Multiplexing(OFDM),one of the core technologies of the fourth-generation wireless communication system,has problems such as strict synchronization requirements,severe out-of-band power leakage,and reduced spectrum utilization due to guard intervals.Unable to adapt to the implementation of diversified businesses.As a result,carrier transmission technologies such as Universal Filtered Multicarrier(UFMC)and Filter Bank Multicarrier(FBMC)that can provide higher spectral efficiency and lower out-of-band power leakage have received widespread attention.UFMC integrates the advantages of OFDM and FBMC systems,can continuously allocate carriers without inserting guard bands;allows differentiated configuration of user bandwidth,and does not require strict synchronization and orthogonality between carriers,which has greater flexibility;its filters The time extension is much smaller than that of the FBMC system,which is conducive to the low-delay transmission and improved spectrum utilization;Quadrature Amplitude Modulation(QAM)is adopted,which is compatible with Multi Input Multi Output(MIMO)technology high.However,the introduction of filters in UFMC also brings new problems for multi-carrier transmission:the interference of the filter to the in-band carrier,the influence of carrier frequency offset(CFO)on the filtered signal,and the influence of multipath fading,Multi-user access leads to increased system complexity,etc.This paper studies and proposes solutions to the above problems.The main work and innovative results are as follows:1.Aiming at the problem of signal attenuation in the transition band of UFMC filter combined with inter-carrier interference,the ICS-UFMC scheme based on carrier weighted modulation is proposed.According to the characteristics of the filter transition band,the solution adopts a differentiated modulation strategy for the user subbands.Paired carriers weighted modulation is used to increase the received signal power of the sideband.The receiving end performs reverse analysis to compensate for the sideband attenuated signal and suppress the interference factor between received signals to realize the self-cancellation of inter-carrier interference.Simulation experiments show that under the same spectrum efficiency,compared with the standard UFMC and OFDM systems,the carrier-to-interference power ratio(CIR)performance of ICS-UFMC can be increased by 8-12dB,and the bit error performance can be increased by 1-5 times.This solution has been granted an invention patent(Patent name:An interference suppression method and device,Patent No.2016106209518).2.Aiming at the problem that the ICS-UFMC overlapping coding causes the phase error introduced by the CFO to be higher than that of the standard UFMC system,this paper proposes the PICS-UFMC algorithm to suppress phase interference.The core idea is to use a-π/2 phase difference angle rotation weighting scheme for the filter transition band carrier pair,the receiving end uses reverse angle weighting to suppress the phase interference caused by CFO.Simulation experiments have verified that under different CFO conditions,the error performance of the PICS-UFMC scheme is better than that of the ICS-UFMC and standard UFMC schemes.Especially for higher CFOs,the scheme has more significant performance advantages and its bit error performance can be improved More than 1 times.3.Since the standard UFMC system filter delay extension cannot effectively combat multipath fading,especially the severe degradation of reception performance during long-delay channel transmission,an SCR-UFMC scheme based on Decision Feedback Equalization(DFE)and symbol reconstruction algorithm is proposed.In this solution,the DFE unit eliminates the inter-symbol interference by using the decision feedback operation of the previous symbol period;the symbol reconstruction algorithm is used to complete the missing information reconstruction to avoid the generation of inter-carrier interference.Simulation experiments are performed under different typical channel models,different QAM modulation orders,and non-ideal channel state information.The scheme can effectively eliminate the influence of multipath channels on UFMC transmission signals.When the signal-to-noise ratio is large(>20dB),compared with the standard UFMC system,the performance of the short-delay channel is more than doubled,while the performance advantage of the long-delay channel is more obvious,and the bit error performance can be increased by 6-28 times.4.Because the complexity of the UFMC waveform transmission system is higher than that of the OFDM system,an optimization scheme of the UFMC calculation structure is proposed.A frequency-domain filtering structure is proposed for the UFMC transmitter and user information extraction is completed ahead of time.This can reduce the complexity of the system,but also improve the transmission efficiency of the system,and the receiver FFT operation scale is also reduced from 2N points to N points.At the same time,the proposed scheme combines the most "0" value filling feature of the user signal and the IFFT clipping mechanism to simplify the calculation structure.For the receiver DFE unit,this paper proposes a truncated sequence convolution scheme based on the characteristic that the process requires only part of the feedback information for operation,and improves the time-domain linear convolution into a frequency-domain DFE fast operation structure.The computational complexity of the system is significantly reduced under different channel delay parameters.