A method and apparatus for indicating a temporary block flow (TBF) to which a piggybacked acknowledgement/non-acknowledgement (PAN) field is addressed. A PAN check sequence (PCS) is created, for example using a cyclic redundancy check (CRC) encoding. The PCS is masked with a temporary flow identity (TFI) assigned to a TBF or a mask generated based on the TFI. A data block including the PAN field and the masked PCS is then processed for transmission. The mask may be generated by converting the TFI using an (M, N) code, M being not greater than the number of bits of the PCS and N being the number of bits of the TFI. With this scheme, a TFI may be transmitted in a PAN field without using explicit bits to identify the TBF.