| Orthogonal Frequency Division Multiplexing (OFDM) is a technology of multi-carrier digital modulation. With the using of the mature technology such as the development of DSP chip the superiority of OFDM technology become more and more obviously. The merge of DSP and OFDM technology, Fourier transform & diverse Fourier transform, QAM technology, Spacing-Time Block Coding, Spacing-Time Trellis Coding, Soft decision technology and Auto-adaptive technology of channel become more and more successfully. OFDM technology have a good capacity to resist multi-path Impact, also have the flexibility of the integration with other access methods and technology, it has been classified as 4G wireless systems candidate program. OFDM has been widespread concern. Paper is divided into four chapters.Chapter I introduced the developments and trends of mobile communication, introduced the characteristics of the first generation of mobile communications systems, the second generation of mobile communications systems, 3G mobile communications systems and fourth-generation mobile communication system and the future of mobile communications developments. Then it introduced the development and application of OFDM technology. Finally, this chapter expounded the advantages and major disadvantages OFDM technology.Chapter II primarily expounded the basic principles and identity of OFDM technology. First of all, it introduced the basic knowledge of wireless communication channel. Secondly, it compared the characteristics of single-carrier and multi-carrier system. Thirdly, it introduced the basic models OFDM system, analyzed the orthogonal nature of OFDM spectrum. Finally, this chapter expounded the application of DFT in OFDM system.Chapter III analyzed the critical technologies of OFDM systems. Firstly, it introduced the Peak-to-Average Ratio impact to the OFDM system, and introduced the methods to control Peak-to-Average Ratio. Secondly, it analyzed the synchronous technology, coding method andsolutions.Chapter IV studied the synchronization technology of the OFDM system. Firstly, it simulated the impact of a variety of factors to the OFDM communication system's performance based on the QPSK modulation. Then it studied various frame synchronization algorithms regularly, and given the relevant simulation results.Chapter V studied differential OFDM systems, it simulated the OFDM multi-carrier communication system with the AWGN channel and multi-path characteristics by computer.Chapter VI summarized the main research aspect on the papers. It also expounded the shortcomings of this paper and the direction of future papers. |
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