Embodiments of the present disclosure relate to devices, methods, apparatuses and computer readable storage media of the resource selection for the transmission of a pending data unit. The method comprises in accordance with a determination that a data unit is not successfully transmitted using a resource associated with an original Hybrid Automatic Repeat Request, HARQ, process, determining a set of allowed HARQ processes for transmitting the data unit based on at least one condition; selecting a further resource associated with a target HARQ process from the set of allowed HARQ process and transmitting the data unit using the further resource to the second apparatus. In this way, a scheme for conditional HARQ switching is proposed, such that the pending MAC PDU could be retransmitted rapidly. Meanwhile, the retransmission of the pending MAC PDU may not influence other scheduled traffics.