Systems and methods provide solutions for PCell interruption for SCell activation and deactivation. A user equipment (UE) may select the delay of PCell interruption based on the transmission time interval (TTI) and the processing time (e.g., the hybrid automatic repeat request (HARD) processing time). A UE may be configured to process a physical downlink shared channel (PDSCH) comprising an activation command or a deactivation command in a first subframe for an SCell. In response to the activation or deactivation command, based on a TTI length corresponding to the PDSCH, the UE determines the delay for PCell interruption. The delay corresponds to a selected second subframe after the first subframe, wherein a first delay for a first TTI length is longer than a second delay for a second TTI length, and wherein the second TTI length is a shortened TTI (sTTI) compared to the first TTI length.