There is transmitted to a user equipment UE in a first subframe of a radio frame a downlink shared channel DSCH according to a first relay-transmission mode (e.g., mode A or A′ in the examples); then switch to a second relay-transmission mode (e.g., mode C or C′ in the examples) within the radio frame based on a channel quality of the DSCH. After switching, then transmit to the UE, in a subsequent subframe of the radio frame, the DSCH according to the second relay-transmission mode. In this embodiment the HARQ process is synchronous and non-adaptive for mode C: the eNB re-transmits packets to the UE in a predetermined fashion to be concurrent with transmission of those same packets from the relay node, as scheduled by the eNB. In this embodiment the eNB receives the UE's NACK for the data that is to be retransmitted via relay through the relay node.