| OFDM technology is one of the key technologies of the current mainstream WLAN standard--802.11a/g,n and ac in baseband system.The mismatching of the local crystal oscillator at both ends of the transceiver can result in carrier frequency offset.The frequency offset will cause the rotation of the subcarrier phase,and the orthogonality between sub-carriers will be destroyed in severe cases.As a result,the performance of system will sharply deteriorate.Meanwhile,in wireless communication,the wireless channel will cause the distortion of the received signal.In order to recover the original bit stream,we must accurately estimate the characteristics of the wireless channel,so as to compensate the received signal.This paper mainly focuses on the FPGA implementation of carrier synchronization and channel estimation in OFDM system.The research status of carrier synchronization and channel estimation is briefly analyzed.The physical layer data frame structure of the existing mainstream WLAN standard is analyzed and introduced in detail.The frequency domain data structure of data frames is emphatically analyzed.Based on the analysis of the main characteristics of the wireless channel,a mathematical model of the wireless channel is proposed.The influence of frequency offset on the performance of the system is analyses.The existing data aided frequency offset estimation algorithm is theoretically analyzed and introduced.Based on that,the frequency offset tracking compensation algorithm based on pilot is simplified and a FPGA implementation scheme of carrier synchronization in OFDM system based on pilot is proposed.Based on the theoretical analysis of the existing mainstream data aided channel estimation algorithms,simplifying LS algorithm based on preamble,a FPGA implementation scheme of channel estimation based on preamble in OFDM system is proposed.The simulation and error analysis for the FPAG implementation scheme of carrier estimation and channel estimation are given in this paper. |
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