1. A parallel symbol cancellation method for canceling an influence of symbols transmitted from a single transmit antenna on signals from a received signal in a Multiple Input Multiple Output (MIMO) system that supports spatial multiplexing, the method comprising: (a) selecting one quadrant among four quadrants including all points on a constellation having normalization distribution; (b) selecting a single reference point in the selected quadrant and generating a reference value corresponding to the single reference point; (c) generating addition values for representing points other than the single reference point in the selected quadrant using distance to the reference point from three points that are closest to the reference point within the selected quadrant; and (d) summing up the reference value and the addition values; wherein summing up the reference value and the addition values are expressed below: 
 y m =( r−h·c 1 )+Δ m where, (r−h·c 1 ): reference value, Δ m : addition value, r: received signal, h: channel value, and c 1 : single reference point in the selected quadrant.