The LTE-Advanced defines a way of downlink mult- input multi-output (MIMO) transmission that supports non-codebook-based precoding with minimum resource allocation consisting of two temporally consecutive physical resource blocks (PRBs). The required channel estimation is facilitated by the specifically provided ''demodulation reference signal'' (DM-RS). However, such channel estimation is challenging in doubly (time and frequency) selective fading channels under minimum resource allocation due to the fewness of DM-RS subcarriers. We propose a decision-directed channel estimation method that addresses the issue. It conducts a sequence of decision-aided averaging of various tentative channel estimates in both the frequency and time domains to arrive at the resulting channel estimate. The method has relatvely low complexity. Simulation results on multipath fading channels demonstrate the performance of the proposed channel estimation method.