A method of transmitting uplink data is provided. The method includes establishing connections with a first serving cell and a second serving cell, determining, by a user equipment (UE), a time period for a device-to-device (D2D) discovery signal communication via the second serving cell, determining, by the UE and based on an uplink grant received via the first serving cell, a first subframe associated with an uplink signal to an evolved NodeB (eNB) associated with the first serving cell, and in response to determining that the first subframe overlaps in time with the time period, refraining from transmitting the uplink signal in the first subframe, and transmitting, based on a retransmission timing, the uplink signal.