Key Technologies Of OFDM Baseband System And Its Design And Implementation On FPGA

Orthogonal Frequency Division Multiplexing(OFDM) is a special multi-carrier modulation technology, and because of its high spectrum efficiency and good performance in resisting to multipath interference, it has been widely adopted in many wireless communication systems, such as Digital Audio Broadcasting System(DAB), Terrestrial Digital Video Broadcasting System(DVB-T), WLAN(IEEE802.11), WMAN(IEEE802.16),3GPP LTE and so on. OFDM can be easily put into application to further improve the reliability of transmission system combined with some other new-emerging technology, such as diversity techniques, smart antenna technology, space-time coding techniques and so on. OFDM has been recognized as one of the key technologies for the next generation of wireless communication systems.The advantage of OFDM system is obvious, but it also faces some serious problems. Synchronization, high peak to average power ratio and channel estimation are the key issues which are limiting OFDM’application very badly. High peak to average power ratio reducing should be implemented in Intermediate Frequency part of OFDM system, and synchronization system and channel estimator should be implemented in digital baseband system. In this paper, the research on the key technologies of OFDM system and the FPGA design of OFDM baseband system based on System Generator is introduced.The main work of this thesis is as following:First of all, a framework of high level synthesizable OFDM system model is designed, and the model can be used for research on key technologies of OFDM and the FPGA design of OFDM baseband system.Secondly, analysis and simulation result of synchronization performance on the joint time-frequency synchronization algorithm based on cyclic prefix with the maximum likelihood method and synchronization algorithm based on training sequence are given, and the result shows that the synchronization algorithm based on training sequence is better than that based on cyclic prefix when they are applied to burst OFDM transmission system. Meanwhile, an analysis and comparison of channel estimation performance between LS(Least Squares) and MMSE(Minimum Mean Square Error) algorithm is given, and the results show that MMSE algorithm has better performance than LS algorithm, but it is more complex than LS when it is implemented on hardware.Thirdly, A high level synthesizable model of OFDM transmitter system based on System Generator is designed, and the model can support BPSK、QPSK、16QAM and64QAM working in the system which can satisfy the multi-working-modal of the next generation of wireless mobile communication system. A high level synthesizable model of OFDM transmitter system based on System Generator is designed, and the improved symbol timing synchronization based on training sequence is applied to the model, and the improved scheme can reduce the complexity of FPGA implementation in great degree without affecting the synchronization performance.Lastly, Analysis and simulation on the transmitter and the receiver of the OFDM baseband system is introduced, and research on FPGA design and implementation on Virtex2-pro-30produced by Xilinx is given, and also some place and route results, hardware resource-taken results on FPGA are given in the last part.