Research On Frequency Offset Estimation Algorithm For Filtered-OFDM Systems

With the IMT-2020(5G)group putting forward the clear requirements for future communication,a variety of application scenarios and business requirements brings new challenges to the physical waveform design.In 2015,Huawei proposed the Filtered-OFDM(F-OFDM)technology based on the OFDM technology,which can decrease the spectrum leakage by the sub-band filter,and each sub-band configures flexible waveform parameters to realize the adaptive air interface technology.As a new multicarrier technology,F-OFDM is more sensitive to the inter-carrier interference caused by frequency offset.Therefore,based on the current research of F-OFDM,it is necessary to adopt frequency offset estimation algorithms to implement in F-OFDM system to reduce the impact on F-OFDM system performance of frequency offset.Firstly,the thesis systematically analyze the small-scale fading characteristics of wireless channel as well as the influence of frequency offset in OFDM system,and deeply research the performance of current frequency offset estimation algorithms in OFDM system from two aspects of theory and simulation.Secondly,due to the F-OFDM symbols in different sub-bands can coexist in time domain and be separated in frequency domain,we research the resource allocation of different sub-bands and subcarrier mapping.And we analyze the effects on sub-bands performance of different bandwidths and different subcarrier interval by simulation.According to the results of simulation we can get that the Doppler shift will bring smaller effect for sub-band under bigger subcarrier interval.Besides,we verify that the sub-band filtering operation of the F-OFDM system can effectively reduce the out-of-band leakage of the spectrum,so the extremely low guard interval of different sub-bands can suppress the interference of adjacent sub-bands.Finally,combining OFDM frequency offset estimation algorithms and F-OFDM system characteristics,we analyze the estimation precisions of CP correlation algorithm,improved CP algorithm,Moose and Classen algorithms in different sub-bands.By the simulation results,the bigger the sub-carrier interval,the smaller influence on sub-bands Doppler shift will bring,and each F-OFDM symbol will be inserted more CP sampling points.Hence,the frequency offset estimation algorithm based on CP is suitable for sub-bands with larger sub-carrier interval.When the sub-carrier interval is small,the Doppler frequency has more influence on sub-bands performance,the symbol length is longer and the number of inserted pilot sequences is larger.Therefore,the data aided frequency offset estimation algorithm with high estimation precision is good for sub-bands with smaller sub-carrier interval.Moreover,based on the same system bandwidths and sampling rate,we simulate and compare the bit error rate performance under the same frequency offset estimation algorithm in F-OFDM with two sub-bands and OFDM.Due to the flexible configuration of waveform parameters in sub-bands and frequency offset estimation algorithm cannot completely eliminate the ICI caused by frequency offset,the bit error rate in F-OFDM is lower than the bit error rate in OFDM with smaller sub-carrier interval and higher than it in OFDM with larger sub-carrier interval,which embody that the F-OFDM system can effectively decrease the performance influence caused by wireless channel through flexible configuration of waveform parameters.