Recently, proximity services (ProSe) has become a promising mobile industry that is capable of creating new mobile service opportunities and offload traffic. The purpose of ProSe applications is to discover instances of the applications running on devices within proximity of each other, and ultimately exchange application-related contents. With ProSe, people’s virtual interactions become more location-centric and tied to their current physical neighborhood (typically <150 ft). This is different from the rather static friend lists in typical online social interactions [1].