1. A maximum likelihood decoding method of separating and estimating multiple transmitted signals transmitted by multiple transmitter antennas from multiple received signals received by multiple receiver antennas, comprising: a first step of generating a channel matrix based on channel impulse responses corresponding to the received signals; a second step of dividing the generated channel matrix H, into multiple sub-matrices h ij , in which the generated channel matrix H is defined as: H = [ h 11 h 12 h 13 h 14 h 21 h 22 h 23 h 24 h 31 h 32 h 33 h 34 h 41 h 42 h 43 h 44 ] and, in which said sub-matrices h ij each have a same size and are defined as: H 11 = [ h 11 h 12 h 21 h 22 ] ⁢ ⁢ H 12 = [ h 13 h 14 h 23 h 24 ] ⁢ ⁢ H 21 = [ h 31 h 32 h 41 h 42 ] ⁢ ⁢ and ⁢ ⁢ H 22 = [ h 33 h 34 h 43 h 44 ]. in which said sub-matrices are comprised of identifying parts of the received signals corresponding to the sub-matrices obtained through the division, and of transforming the sub-matrices, obtained through the division, by using inverse matrices of the sub-matrices obtained through the division; after said second step, a third step of transforming the received signal parts using said sub-matrices; and a fourth step of selecting at least one combination candidate for parts of the transmitted signals corresponding to the transformed received signals, and determining one combination candidate for each of the parts of the transmitted signals so that the determined combination candidate has a shortest Euclidean distance, wherein the sub-matrices collectively represent all received signals as follows: [ r 1 r 2 ] = H 11 ⁡ [ t 1 t 2 ] + H 12 ⁡ [ t 3 t 4 ] ⁢ ⁢ and ⁢ [ r 3 r 4 ] = H 21 ⁡ [ t 1 t 2 ] + H 22 ⁡ [ t 3 t 4 ] ⁢ , wherein each partial transmitted signal is calculated based on all received signals, where t 1 -t 4 are transmitted signals and r 1 -r 4 are reception signals.