A first node receives a first signaling; receives a second signaling; and transmits a first bit block in a target radio resource block. A first sub-bit-block and a second sub-bit-block are used to generate the first bit block, the first sub-bit-block being associated with the first signaling, and the second sub-bit-block being associated with the second signaling; the second signaling is used to indicate the target radio resource block from a target radio resource block set, the target radio resource block being a radio resource block comprised in the target radio resource block set; size of the second sub-bit-block is used to determine a reference radio resource block set; the second signaling is used to indicate a first index, and the first index is used jointly with the reference radio resource block set to determine the target radio resource block set, the first index being an integer.