The Research Of Synchronization Technique For OFDM Based On Wireless Channel

Because of robustness to impulse noise and fast frequency selective fading, orthogonal frequency division multiplexing(OFDM) modulation has attracted considerable attention from researchers.However, OFDM systems are very sensitive to time and frequency synchronization errors.Many experts have done a lot of research and got lots of achievements about synchronization schemes which can be realized simply and have good performance.This dissertation investigates the topic of time and frequency synchronization for OFDM systems.The content of the dissertation is shown as following. Firstly, some related technology about this task is described, such as the history and development about OFDM, the application of OFDM in WLAN, advantages and disadvantages of OFDM systems.Secondly, the basic theory of OFDM system and the system model are introduced, and the errors of timing synchronization, frequency synchronization and the sampling rate synchronization are discussed in detail.Thirdly, some typical synchronization schemes have been studied and compared their performance and practicability as well as their merits and drawbacks. Improved algorithms are also presented and simulations results illustrate the performance of algorithms.Afterwards, a new synchronization scheme for timing synchronization and carrier frequency synchronization based on the preamble configuration of IEEE 802.11a is presented; simulation results and the synchronization structure are also presented. After summerizing the work experience, the realization of synchronization using FPGA is introduced, especially the modle of carrier frequency offset estimation. Also, the simulation results are shown.At last, some conclusions and advice are given to improve synchronization of OFDM system.