1. A method of a user equipment (UE) in a wireless communication network, the method comprising:identifying pre-configuration information for a transmission of a synchronization signal; and
transmitting the synchronization signal in a transmission resource determined based on the pre-configuration information,
wherein the pre-configuration information comprises a pool list for device to device (D2D) communication, and
wherein the UE exists outside of coverage in which a service is provided by a base station.