Due to the time-varying characteristics,the channel matrix in the frequency domain of OFDM ( OrthogonalFrequency Division Multiplexing) system is approximately banded.Although the receiver window can improve theband-limited characteristics of time-varying channels,the equivalent channel cannot be modeled linearly.In orderto solve this problem,a new windowed-LTV ( Linear Time-Varying) model is proposed,which separates the timevaryingcharacteristics of the receiver window from those of the channel.Moreover,a time-varying channel estimationmethod of the model is investigated,and a simplified algorithm is presented to reduce the computational complexity.Simulated results show that the receiver window reduces the inter-subcarrier interference out of the band ofthe channel,and that,as compared with the traditional OFDM methods,the proposed algorithm brings about a performanceimprovement of 2.5 dB.