1. A method for predicting precoding matrix (PM) in a MIMO System, comprising: obtaining a present PM based on a present transmission; fitting the present PM and previous PMs with a predefined model; and determining a forthcoming PM which is expected to be used in the next transmission based on the fitting, wherein determining the forthcoming PM which is expected to be used in the next transmission based on the fitting comprises: determining a step size based on the fitting; extrapolating on the fitting result with the step size, based on the predefined model; and obtaining the forthcoming PM based on the extrapolation, and wherein determining the step size based on the fitting comprises: defining a plurality of PMs by using different step sizes based on the fitting; calculating an error metric between each of the plurality of PMs and a set of the previous PMs; and determining a step size corresponding to the maximum error metric.