An adaptive two-stage downlink control channel structure is utilized for control channel transmission with code block group (CBG) retransmission for 5G and other next generation wireless systems. In an aspect, the first stage of the two-stage downlink control channel structure utilizes a defined format (e.g., having a fixed length) and provides information that is employable to determine the length and/or coding scheme of the second stage. In another aspect, the second stage of the two-stage downlink control channel structure utilizes a variable length/size to indicate the CBGs that are scheduled to be retransmitted (e.g., by employing a variable length bitmap). As an example, the length/size is varied based on a length/size of a transport block, from which the CBGs have been generated.