Social-Aware Relay Selection for Cooperative Multicast Device-to-Device Communications

The increasing use of social networks such as Facebook, Twitter, Instagram allows to share photos, video streaming, music among friends and causes a significantly increase of the amount of data over wireless networks. This social behavior can have an impact on communications networks in particular on device-to-device (D2D) communications that are considered one of the main drivers for the next fifth-generation (5G) cellular systems. Specifically, the download of popular contents which are required more frequently, can be carried out through D2D communications reducing the traffic load of a cell. Recently, the social-aware layer and its relationship and influence on the physical communications layer have been addressed. We study the problem of multicast data dissemination to a group of D2D users by selecting a D2D user which acts as relay for the formed social community, with the constraint of minimizing the end-to-end delivery delay. In a multicast group, data have to be received from all the participants and consequently the end-to-end delivery delay is defined as the time necessary to transmit the data from a source to all the destinations. Among different D2D users acting as relays, we select the best relay according to the best quality of propagation link jointly with the best social trust level. The selected relay retransmits the same content to all the D2D users, according to the dynamics of the social- multicast communications layers. Numerical results show the impact of social level on the end-to-end delivery time in the integrated social-physical network and a comparison with relay-assisted multicast communications without the social ties is underlined.