Distributing content updates over a mobile social network

We study the dissemination of content updates, such as news or traffic information, over a mobile social network. In this application, mobile users receive content updates from their service provider. To improve coverage and increase capacity, we assume that they also share such updates, opportunistically, whenever they meet. We show that the service provider can allocate its downlink bandwidth so that it maximizes the aggregate utility over all users, i.e., the social welfare. Moreover, we specify a condition under which the system is highly scalable: even if the total bandwidth dedicated by the service provider remains fixed, the expected content age at each user grows slowly (as log(n)) with the number of users n.