In accordance with the time-domain correlation of time-varying channels and the SPA ( Sum and Product Algorithm) rules, a channel estimation algorithm based on factor graph is proposed. Firstly, the channel frequency responses between adjacent the OFDM ( Orthogonal Frequency Division Multiple-xing) symbols are modeled as first-order AR ( Auto-Regression) process, and then, information exchange between adjacent channel coefficient nodes is realized on the factor gragh, and via multiple iterations,the accuracy of least-square ( LS) channel estimation on pilot positions is improved. Simulation results show that the proposed algorithm could effectively improve the estimation performance of LS algorithm for time-varying multipath channels, and performs better than the traditional MMSE ( Minimum Mean Square Error) channel estimation algorithm.%依据时变信道的时域相关性以及和积算法( SPA)规则，提出了一种正交频分复用( OFDM)系统中基于图模型的信道估计算法。首先，将相邻OFDM符号之间的信道频率响应建模为一阶自回归( AR)过程；然后，在因子图上实现相邻信道系数节点之间的信息交换，通过多次迭代提高了导频处信道估计的精度。仿真结果表明，本算法可以有效改善最小二乘( LS )算法对于时变多径信道的估计性能，性能优于传统的最小均方( MMSE)信道估计。
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