Abstract: Provided is a method for retransmission in a mobile communication system; and, more particularly, to an integrated operation method of Automatic Retransmission Request (ARQ) and Hybrid Automatic Retransmission Request (HARQ) in a mobile communication system. The method includes the steps of: a) shifting to a 2nd layer waiting status upon receipt of 1st layer reception failure information in a sending status that a fragment block of 2nd layer transmission data is transmitted to the a receiver according to the predetermined retransmission number; b) shifting to a 1st layer receiving status upon receipt of 1st layer reception success information in the sending status; and c) shifting to the transmission completion status upon receipt of the 2nd layer reception success information in the sending status.

Abstract: Provided are a QR decomposition apparatus and method for a MIMO system. The QR decomposition apparatus includes: a norm calculator for calculating a vector size norm for a channel input; a Q column calculator for calculating a column value of a unitary matrix Q by multiplying a delayed channel input with ?{square root over (norm)}; an R row calculator for receiving the delayed channel input, the output of the Q column calculator, and 1/?{square root over (norm)}, and calculating a row value of an upper triangular matrix R; a Q update calculator for receiving the delayed channel input, the output of the R row calculator, and a delayed output of the Q column calculator, and calculating a Q update matrix value; and a norm update calculator for receiving a delayed output of the norm calculator and an output of the R row calculator, and outputting a norm update matrix value.