A method for encoding a transport block in a wireless communication system, and a wireless apparatus therefore are discussed. The method according to one embodiment includes determining, at a transmitting device, a size of the transport block based on a size of an allocated resource, a number of layers, and modulation and coding scheme (MCS) for the transport block, wherein the size of the transport block is determined from among a plurality of predetermined sizes, wherein the plurality of the predetermined sizes include 305976 bits, 324336 bits, and 391656 bits when the transport block is mapped to four-layer spatial multiplexing and when 256 Quadrature amplitude modulation (QAM) is used for the transport block; and attaching at the transmitting device, a first cyclic redundancy check (CRC) code to the transport block to configure a first CRC-attached transport block.