1. A method of processing received signals at a multiple input multiple output (MIMO) receiver including a plurality of antennas, the method comprising: selecting a reference resource element (RE) from an RE group including a plurality of REs; generating a preprocessing filter to be shared among the plurality of REs of the RE group based on channel information of the reference RE; generating covariance matrices of the REs except for the reference RE based on channel information of the REs except for the reference RE of the plurality of REs; and generating detection signals of the RE group by compensating for the received signals of the plurality of REs by selectively using the preprocessing filter and the covariance matrices.