Ofdm System Synchronization And Demodulation Of The Fpga To Achieve

The OFDM technology has been used widely in the field of digital audio and video broadcast system and become part of the local area network standards since the 1980s. It causes people's great attention because of its high utility ratio of the frequency spectrum and low cost. Its application will become more and more extensive in the field of integrated wireless access, while the need of digital, broad-band, personalize and mobile communication is increasing. People are paying more and more attention on the development of the OFDM technology's application in the field of wireless communication, and the thesis also focuses on its application in this field.All the content of the thesis is based on the realization of the air to grand digital wireless communication system on FPGA. The main work of the author focuses on the realization of the receiving terminal of the down-link. This thesis investigates frame synchronization algorithm and frequency synchronization algorithm in the downlink system. Moreover, FPGA implementation of synchronization algorithms, QAM demodulation algorithms and multi-carrier demodulation algorithms are also discussed explicitly. At last realize all the down-link of the high speed digital audio transmission system.In the wireless mobile communication system, the Doppler shift and the carrier shift between transmitters and receivers will destroy the orthogonality of the subchannels, and then cause the ICI. ICI will degrade the system performance significantly. Synchronization is also a vital factor for the correct OFDM demodulation at the receiving terminal, because the IFFT/FFT modulation and demodulation technologies are adopted in the OFDM system. The time and frequency shifting estimate and compensate schemes in the synchronization can reduce their impact on the system performance. The thesis costs three parts to introduce the theory of the synchronization, the algorithms and the realization.We summed up the synchronization algorithms in three kinds: data-aided algorithms, blind estimation algorithms and half-blind estimation algorithms based on Cyclic Prefix. In the thesis, first we analyzed the advantages and disadvantages of different synchronization algorithms, and then took different algorithms in different literature cites for example. Second we introduced our synchronization algorithms and the realization details on FPGA. We used the data-aided algorithms in the time synchronization and frequency synchronization. We not only expounded the details of the algorithms we used, but also analyzed the difference of their performances between different parameters and means.The realization of FFT on FPGA is very simple. We introduced the accomplished structure of the OFDM demodulation, focusing on the computational process of the valid data extraction. Last, we introduced the way of the QAM soft demodulation.First the thesis gives the theory of the algorithms, then gives the formulas, and last analyzes the performance based on the coefficients and variables in these formulas. When introducing the ways of the realization, the thesis gives the whole structure firstly, and then introduces the details. After introducing every module the thesis gives the simulation and test results of this module, and then gives the test results of the whole system at last.