A communication apparatus is provided. The communication apparatus includes at least one radio transceiver module, a first subscriber identity card, a second subscriber identity card and a processor. The first subscriber identity card camps on a first cell belonging to a first wireless network via the same or different radio transceiver modules. The second subscriber identity card camps on a second cell belonging to a second wireless network via the same or different radio transceiver modules. The processor, coupled to the first subscriber identity card, the second subscriber identity card and the radio transceiver module(s), receives an apparatus originated communication request with a destination address, compares a signal strength of a first signal received from the first cell with a signal strength of a second signal received from the second cell and establishes a wireless communication with a peer device having the destination address through the cell with better signal strength.