What is meant here is that a condition of one of the mentioned four embodiments is considered first, and when events with an identical priority exists, a condition of another embodiment may be considered. Therefore, the intention is to enable a UE to determine final priorities of corresponding D2D signals.

According to the method according to an exemplary embodiment, when a UE has a single transceiver chain, a signal having a low priority may be dropped. This may be equally applied to a single carrier environment or multi-carrier environment.

Alternatively, even in the case where the UE has an independent transceiver chain, when D2D signals are simultaneously generated on multiple carriers and the transmission power of the D2D signals exceed P_CMAX that is a maximum output power configured for the UE (a total configured maximum output power), the D2D signals may be selectively dropped or power scaling may be executed (for example, decreasing Tx power) based on a priority. Power scaling refers to reduction of a transmission power based on a predetermined scale, so as to allocate power that does not exceed a total transmission power of a UE. An example of power scaling is multiplexing an original transmission power by a scaling factor. The power scaling may be expressed variously, such as power adjustment, power-scale down, or the like. That is, according to an exemplary embodiment, D2D signals are distinguished based on a priority and power scaling may be selectively executed.

FIG. 15 is an example of a flowchart illustrating operations of a UE according to an exemplary embodiment.