Research On Key Technologies Of Filtered-OFDM

In order to meet the needs of fifth generation mobile communication systems for transmission efficiency,time and frequency resource utilization,and diversity of business,the filtered orthogonal frequency division multiplexing(F-OFDM)is proposed as a new multicarrier technology and becomes one of the candidates for the next generation mobile communication system.Through the division of spectrum and the subband filtering which is different from orthogonal frequency division multiplexing(OFDM),F-OFDM can not only retain the high effective data transmission and other advantages,but also overcome the disadvantages of OFDM,such as serious out-of-band leakage and strict requirement on synchronization.In addition,F-OFDM can have several subbands with different parameters to achieve the flexibility of business needs.However,due to the presence of multiple high-order subband filters in F-OFDM system,it will have higher system complexity.And there is also a higher peak to average power ratio(PAPR)in F-OFDM system.This paper focuses on these two problems to research.Firstly,this paper introduces the overall structure of F-OFDM system,and focuses on the working principle and implementation method of the key parts of the transmitter and receiver,which are different from those of the OFDM system.By simulation,it is verified that the F-OFDM system can get the similar reliability with the OFDM system.Secondly,the filter design method based on window function method is studied,and the characteristics of different window functions and their influence on the performance of the system are compared.Aiming at the problem that the complexity of the system is increased due to the subband filtering in F-OFDM,a frequency domain filtering method based on overlap-save and overlap-add is proposed instead of the time domain filtering method to achieve low complexity subband filtering.The computational complexity of time domain filtering and frequency domain filtering is compared.Comparing the computational complexity of time domain filtering and frequency domain filtering,combined with the error rate curve of the system,we can see that the F-OFDM system using frequency domain filtering can maintain the bit error rate(BER)performance of the original system while reducing the complexity of the system.Thirdly,the existing technology about PAPR suppression in OFDM system is introduced,and the C transform and clipping and filtering are studied.According to the characteristics of F-OFDM system architecture,the two algorithms are applied to the system respectively.According to the influence of algorithm on the BER and PAPR,the two algorithms are optimized to C transform filtering and iterative clipping and filtering respectively.The performance of the new algorithm is analyzed by simulation.Finally,a new PAPR suppression algorithm used in F-OFDM system is proposed,which is C transform iterative clipping and filtering algorithm,and it is optimized.Simulation results show that the optimized C transform iterative limiting filter algorithm increases the complexity of the system to a certain extent,but it is superior to the original PAPR suppression method in terms of PAPR suppression and system reliability.