Method and apparatus for performing harq in wireless communication system

PURPOSE: A method for implementing HARQ(Hybrid Automatic Repeat Request) in a wireless telecommunications system and an apparatus thereof are provided to obtain an additional diversity gain from a MIMO(Multiple Input Multiple Output) system using CRV(Constellation Rearrangement Version). CONSTITUTION: Encoded information bit is stored in a circular buffer(S100). A transmission block is selected in a circular buffer(S110). A bit set, which includes the bit of the n of the transmission block, is mapped according to a first mapping rule into a data symbol on a constellation for 2n-QAM modulation(S120). The bit set is mapped according to a second mapping rule while wrapping around the bits of the transport block in the end of the circular buffer. A CRV(Constellation Rearrangement Version), which shows the mapping rule of the bit set, is transmitted to a terminal.