1. A receiving-end apparatus in a Multiple Input Multiple Output (MIMO) wireless communication system, the apparatus comprising: a plurality of receivers for receiving training symbol vectors and a data signal vector from a transmitting end through a plurality of corresponding receive (Rx) antennas; and a detector for expanding the training symbol vectors into second- or higher-order polynomials, for generating a weighting parameter vector for multivariate polynomial expansion of the data signal vector by using the polynomials expanded from the training symbol vectors and for expanding the data signal vector into a second- or higher-order multivariate polynomial using the weighting parameter vector, and for detecting Transmit (Tx) values of the data signal vector from the multivariate polynomial, wherein the polynomials comprise a plurality of elements more than a number of elements of an original vector and comprise at least one of an element of the original vector, a square of an element of the original vector, and a multiplication of two elements of the original vector, and wherein the original vector comprises one of the training symbol vector and the data signal vector.