A mobile communication device including a wireless transceiver and a controller is provided. The wireless transceiver performs wireless transmission and reception to and from a cell. The controller determines whether an Application-specific Congestion control for Data Communication (ACDC) has been enabled in the cell in response to a Domain Name Server (DNS) query or Internet Protocol (IP) packet initiated by an application, and in response to the ACDC having been enabled, responds to the DNS query with an IP address or transmits the IP packet to the cell via the wireless transceiver only when the application is associated with a high-priority service.