1. A QR decomposition apparatus for a Multiple Input Multiple Output (MIMO) system, comprising: a norm calculating means for calculating a vector size norm for a channel input; a Q column calculating means for calculating a column value of a unitary matrix Q by multiplying a delayed channel input with √{square root over (norm)}; an R row calculating means for receiving the delayed channel input, the output of the Q column calculating means, and 1/√{square root over (norm)}, and calculating a row value of an upper triangular matrix R; a Q update calculating means for receiving the delayed channel input, the output of the R row calculating means, and a delayed output of the Q column calculating means, and calculating a Q update matrix value; and a norm update calculating means for receiving a delayed output of the norm calculating means and an output of the R row calculating means, and outputting a norm update matrix value.