The time varying channel between transmitter and receiver in wireless communications necessitates the receiver to be informed about the channel between the transmitter and the receiver periodically in the detection procedure. This paper introduces a geometrical model for channel matrix in a multiple-input multiple-output (MIMO) communication system, where the channel is supposed to be fast fading.Then an auto regressive (AR) model is proposed for the channel matrix variations at each time instant, based on which an LMS-like procedure for tracking the channel is suggested to increase the time period required for channel training in order to increase the data transmission rate. The efficiency of the method for channel matrix estimation is studied through simulation.The results show satisfactory match between the true and the estimated channel.