Device and method of handling hybrid automatic repeat request transmission

A communication device for handling a hybrid automatic repeat request (HARQ) transmission, comprising:

• a storage unit, for storing instructions of:
• performing a first downlink (DL) reception in a first subframe from a serving cell of a network;
• and
• transmitting a first HARQ feedback in a second subframe to the serving cell in response to the first DL reception, wherein the second subframe is determined according to the first subframe and a sum of a predetermined timing and a first HARQ timing, wherein the first HARQ timing is for transmitting the first HARQ feedback of a packet received according to the first DL reception, and the first HARQ timing is indicated by a DL control information (DCI) transmitted by the network;
• wherein a uplink (UL) resource for transmitting the first HARQ feedback is selected from a plurality of UL resources of the second subframe, and each of the plurality of UL resources is scheduled with a starting point, a duration and a bandwidth;
• wherein the first HARQ timing indicates whether the first HARQ feedback is postponed and/or a time period postponed with respect to the predetermined timing;
• and
• a processing circuit, coupled to the storage unit, configured to execute the instructions stored in the storage unit.