In higher order quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM) system, the distribution of high-density constellation becomes more sensitive to carrier frequency offset (CFO) and sampling frequency offset (SFO). In this paper, the impact of frequency synchronization errors on high order QAM modulated OFDM signal is analyzed under both time-invariant multipath channel and multipath Rician fading channel, and an algorithm to jointly correct both CFO and SFO is proposed. A closed-form formula for the mean square error (MSE) of the estimation is given by the theoretical analysis and its reasonability is verified by simulation results.%采用高阶QAM (Quadrature Amplitude Modulation)调制的正交频分复用(OFDM,Orthogonal Frequency-Division Multiplexing)系统,相对于低阶调制来说,密集的星座点分布更容易受到载波频偏与采样频偏的影响.本文分析了高阶QAM OFDM系统对频率同步精度的要求,提出了一种载波与采样频偏联合纠正的方法,并分别针对时不变多径信道和块衰落多径Rician信道给出了频偏估计的均方误差解析表达式.均方误差的理论分析与计算机仿真结果吻合；误比特率性能仿真表明,频偏纠正后的误比特率性能与无频偏情况比较,差异小于1dB.
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