A Study And Implementation Of Synchronization And Channel Estimation In OFDM Systems Based On IEEE802.16d

In the standard based on IEEE802.16d, an air interface criterion for fixed broadband wireless access systems is prescribed. The OFDM is a multi-carrier transmission technique used by IEEE802.16d, which is of high utilization efficiency of frequency spectrum and resistant for multi-path. The thesis mainly investigates and implements synchronization and channel estimation technologies in OFDM systems based on IEEE802.16d.In techniques of synchronization in OFDM systems, classical methods of symbol timing and carrier frequency synchronization are summed up by the paper, and they are improved so much that they are applicable to OFDM systems based on IEEE802.16d. The result from simulation and verification indicates that auto-correlation and cross-correlation synchronization techniques using short preamble could eliminate timing illegibility resulting from correlation flat phenomena, moreover, they can improve the timing precision. Decimal and integral frequency offset estimation using short preamble are of smaller mean square error and larger estimation extension.The implementation process on FPGA chips for symbol timing and carrier frequency synchronization based on IEEE802.16d is expatiated in the thesis, and function diagrams of every module are listed. The dissertation studies the problem of AGC adjusting, which was confronted in the testing period. With detecting in advance, the synchronization algorithm can be capable when the AGC unit is adjusting.In channel estimation techniques, the paper stresses to discuss the algorithm of pilot-aided channel estimation, including choices of pilots, capture of the channel information of pilot and non-pilot position. At the point of view of amplitude and phase, the way of linear A-θinterpolation for the non-pilot position is presented. The paper analyzes the principle of linear I-Q and A-θinterpolation in OFDM systems based on IEEE802.16d, and concludes that linear A-θinterpolation will perform better.The thesis gives us the procedure for FPGA implementation of channel estimation based on IEEE802.16d, and implements linear I-Q and A-θinterpolation separately, then analyzes and compares the complexity. As the performance is improved, the complexity of A-θinterpolation increases.