| OFDM is the key technique for the new generation wireless communication.With its high spectrum usage,good ability in coping with frequency selective fading and robustness against multi-path delay spread,it has been widely used in many advanced digital communication systems.WLAN whose PHY adopts OFDM modulation specifies by IEEES02.11a,its research and application is paid more attention and regard to.This thesis is to make research on the key technologies of WLAN,and it includes the study and implementation schemes of OFDM channel estimation,timing synchronization as well as frequency offset estimation according to IEEE802.11a standard.Pilot-aided approaches for OFDM channel estimation are introduced,typical methods are analyzed and compared by MATLAB simulation.According to the standard,the paper puts the pilots to the least square criterion to estimate the channel frequency domain response by using linear interpolation method with comb-type pilots arrangement in FPGA implement,it makes a good balance between algorithmic capability and FPGA design complexity.Only the real part of the autocorrelation is used in symbol synchronization algorithm based on autocorrelation so that two but not four multipliers are needed in the FPGA implement,therefore it can reduce the design complicacy. CORDIC processor in pipelined architecture is adopted to implement the two main units of argument of the complex number and frequency offset emendation.Due to the similar algorithmic theory and implementation scheme between coarse and elaborate frequency offset estimation,a set of circuit can be multiplexed.The scheme has the advantages of simply implementation,fast working speed,high efficiency and reducing half of the hardware sources.This paper gives the circuit implement schemes of the key module with correct simulation results,these key techniques are the basic problems in communication system,it is helpful for the design and application of other communication systems. |
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