| Multi-carrier modulation based on filter banks is a kind of technology, which can improve spectrum utilization and reduce energy consumption. It can overcome the limitation of guard-band of the orthogonal frequency division multiplexing(OFDM). The 5th generation mobile communication systems(5G) are faced with challenges of variety of application scenarios and traffic requirements, which the new waveform should be able to adapt to. There are several major new waveforms that are considered to be candidate waveforms for 5G, including filtered-OFDM, filter bank multicarrier, universal filtered multicarrier, etc. Filtered-OFDM technology is studied in this thesis.The research focus of this thesis includes the design and implementation of subband filter, the suppression algorithm of peak to average power ratio in filtered-OFDM, the time-frequency efficiency in filtered-OFDM, and a sub-optimal reception algorithm designed for nonlinear distortion introduced by the clipping in the transmitter. The main contents of this thesis are described as follows.The first chapter summarizes the vision of the 5G systems and technical challenges faced by key technologies towards dynamic air interface technology. Then the chapter briefly introduces the state of art of several 5G candidate waveforms, and the research content of this thesis.The second chapter analyzes the structure characteristics of the f-OFDM transmitter. Based on the study of the design of subband filter, the implementation process of the subband filter is analyzed, which is the time domain filter and the frequency domain filter; A PAPR suppression algorithm is proposed to reduce the PAPR of transmission signal, which is suitable for f-OFDM system. The block error rate is used as the performance index, and the simulation results are verified by different modulation methods in the environment of the extended pedestrian A mode. Simulation results verify the f-OFDM can well support asynchronous transmission, also show the effectiveness of PAPR suppression algorithm, which is presented in this thesis.The third chapter introduces the receiver structure of f-OFDM. The subband filter in the receiver can eliminate the effect of other subband signals. The time-frequency efficiency of several candidate waveforms is analyzed and compared, which shows that the f-OFDM system can achieve a high time and frequency efficiency with the subband parameters optimum design. Besides, we use the sub-optimum receiver to improve the system performance because of the operation of clipping and filtering in the transmitter. With block error rate as the performance index, this chapter simulates the effect of different number of guard tones on the subbands signal in the environment of extended typical urban model. The result shows that the f-OFDM can easily improve the spectrum utilization because it can eliminate the interference between subbands by using few guard tones. What’s more, the sub-optimum receiver can improve the performance by using nonlinear distortion that introduced by clipping.The fourth chapter uses USRP to build up the system according to the transmitter and receiver structure that introduced in chapter 2 and chapter 3, which verifies the practical feasibility of the system, and introduces the key modules in this system. The spectral efficiency advantage of F-OFDM system is demonstrated through measurement of USRP transmitted signal by spectrum analyzer. At the same time, the simulation results show that the PAPR of the transmitted signal by clipping and filtering method can be effectively suppressed.The fifth chapter summarizes the work of this thesis and discusses the problems that need to be further studied in order to make f-OFDM better apply to the 5G system. |
PDF Full Text Request