A DL control channel candidate can be decoded. A determination can be made for which DL OFDM symbol the decoded DL control channel candidate is received in. A determination can be made for a DL resource assignment from the decoded DL control channel candidate. Data can be received based on the DL resource assignment. A determination can be made for a time-frequency resource for transmitting a HARQ-ACK at least based on the determined DL OFDM symbol. The HARQ-ACK can be transmitted in the determined time-frequency resource. The transmitted HARQ-ACK can correspond to the received data.