FIG. 5 depicts a flow chart 500 for performing, by a user equipment (UE), inter-frequency and inter-public land mobile network (PLMN) discovery for device-to-device (D2D) discovery with one or more UEs. A UE can identify a capability to participate in inter-frequency and inter-PLMN discovery, as in block 510. The UE can receive an SIB19 of the serving cell in the serving frequency and PLMN, as in block 520. The UE can acquire inter-frequency and inter-PLMN discovery system information acquisition assistance signaling, as in block 530. Different options of acquisition assistance signaling can be used in block 530. The UE can receive the SIB19 of other cells for other frequencies and PLMNs, as in block 540. The UE can acquire inter-frequency and inter-PLMN announcing and/or monitoring control configuration, as in block 550. It should be noted that at block 550, different options of announcing and/or monitoring control of not-served users can be used in block 550. The UE can participate in D2D discovery according to the configuration, as in block 560.
