A communications apparatus includes a radio transceiver and a processor. The radio transceiver is configured for transmitting or receiving wireless radio frequency signals to or from a peer device. The processor determines whether re-synchronization in a communication mode with the peer device is required according to a determination rule. When the re-synchronization is required, the processor transmits a message to the peer device via the radio transceiver to trigger a re-synchronization procedure. The processor determines whether the re-synchronization is required in a connected mode.