A method and apparatus for indicating a temporary block flow (TBF) to which a piggybacked acknowledgement/non-acknowledgement (PAN) field is addressed are disclosed. A sequence may be generated from a temporary flow identity (TFI) to which the PAN field is addressed and masked with a PAN check sequence (PCS). A radio block including a PAN field and a masked PCS is transmitted. The PCS may be masked with one of TFIs which is selected in accordance with a rule pre-agreed. A secondary identifier may indicate a TBF to which the PAN field is addressed. A special value may be used to represent all TBFs assigned and a secondary identifier may indicate a TBF to which the PAN field is addressed. A special value on the PAN field may be used for control purposes for indicating an action affecting a group of receiving stations listening to the radio block.