Research On Baseband Filtering Of Muti-carrier Transmittion Systems

The multi-carrier system including orthogonal frequency division multiplexing(OFDM)have numerous advantages such as the stable high data rate transmission,effectively interferes with the inter symbol interference(ISI)caused by signal multipath propagation,and easy to achieve and so on.But the sidelobes of multi-carrier systems are too high.Filtering is one of the effective methods to improve the out-of-band radiation by improving the sidelobe descent rate of the waveform.At present,a variety of multi-carrier modulation based on filtering technology is being widely studied,including N-continuous orthogonal frequency division multiplexing technology,filtering orthogonal frequency division multiplexing technology,generalized frequency division multiplexing technology,filter bank multicarrier technology and so on.However,the filtering process will bring distortion to transmission signal,thus affecting the system transmission performance and the time domain signal fluctuation characteristics.The main research purpose of this thesis is achieving comprehensive performance between out-of-band radiation,time-domain fluctuation and transmission performance.In this thesis,the main research targets are N-continuous orthogonal frequency division multiplexing technique and filtering orthogonal frequency division multiplexing technique.In the N-continuous orthogonal frequency division multiplexing system,the bit error rate is mainly concerned.Including three bit error rates optimization algorithm based on power allocation and adaptive modulation.In the filtering orthogonal frequency division multiplexing system,several peak-to-average ratio suppression algorithms which can be applied to the filtering orthogonal frequency division multiplexing system are mainly studied,which can better adapt to the future development requirements of wireless communication system.The research achievements in this paper can be applied to the new multi-carrier system based on filtering,and optimize the system performance in terms of spectral efficiency,peak-to-average power ratio and bit error rate.The specific work of this thesis is summarized as follows.In the first chapter,we review the development of multi-carrier systems,especially OFDM and F-OFDM systems,and the problem of spectral leakage and peak-to-average ratio of transmission signals under multi-carrier systems.Summarized the side-lobe and PAPR suppression method,and the method of combining sidelobe and PAPR suppression,pointed out the starting point of this paper.The second chapter introduce the OFDM system,F-OFDM system and the existing N-continuous-OFDM and N-continuous-OFDM-based improved systems in detail.The spectrum leakage problem of these three systems is analyzed,the simulation and comparison of the above systems are demonstrated,and the advantages and disadvantages of the system are pointed out.In the third chapter,we study and induce the existing N-continuous-OFDM and time domain N-continuous-OFDM.The power distribution of the smoothing signal is given.Three schemes are proposed to optimize the bit error rate performance of the system and compare the performance of these schemes.In the fourth chapter,several peak-to-average-power ratio(PAPR)optimization algorithms for F-OFDM systems are studied including means of iterative clipping filtering,partial transmission sequence and discrete Fourier transform.The comparison and performance analysis of the three aspects of out-of-band leakage,peak-to-average ratio and bit error rate are given.In summary,this thesis studies the problems of out-of-band radiation and peak-to-average power ratio in baseband filtering multi-carrier system,and gives an algorithm to ensure the performance of all aspects.It is expected to improve the comprehensive performance of the physical layer waveforms of the next generation communication system based on filtering,reduce the mutual interference between the communication links,and improve the spectrum utilization of the communicaiton system.