FIG. 3 illustrates a schematic diagram of network deployment of a cellular wireless communication system, which may use the 3GPP LTE/LTE-A technology or other cellular wireless communication technologies described above. In an access network of the cellular wireless communication system, network devices generally include a certain number of base stations and other network entities or network elements. In summary, in the 3GPP, the network devices may be collectively referred to as Evolved Versatile Terrestrial Radio Access Network (E-UTRAN) side devices, or network side devices of the cellular network for short. The base stations (BS, or Node B, or evolved Node B (eNB)) include low power nodes (LPN) in the network, such as pico base stations, relay nodes, femto cells and home eNBs (HeNB). For the sake of convenience of description, only three base stations are shown in FIG. 3. Each of the base stations provides a specific radio signal coverage area in which terminals, UEs or devices can communicate with the base station wirelessly. The radio signal coverage area of a base station may be divided into one or more cells or sectors, for example, three cells, according to some rules.

At present, application of the D2D discovery discussed in the 3GPP includes two distinct scenarios: an in-network scenario and an out-of-network scenario. The in-network means that UEs performing D2D discovery are located in the coverage area of the cellular network, for example, the scenario shown in FIG. 3; the out-of-network means that locations of the UEs performing the D2D discovery are not covered by the cellular network, for example, a coverage blind area where the network coverage does not reach or a coverage blind area caused by damage of a network device.

Embodiment 1