A method by a user equipment (UE) in a wireless communication system includes: receiving a first physical downlink shared channel (PDSCH) transmission and a second PDSCH transmission that carry a same transport block (TB) and are associated with a first transmission configuration indicator (TCI) state and a second TCI state, respectively; determining a transport block size (TBS) of the first PDSCH transmission; and determining low-density parity-check (LDPC) base graph corresponding to the transport block based on the determined TBS for each of the first PDSCH transmission and the second PDSCH transmission, wherein the determined TBS of the first PDSCH transmission is applied to the second PDSCH transmission.