3G networks are currently overloaded, due to the increasing popularity of various applications for smartphones. Offloading mobile data traffic through opportunistic communications is a promising solution to partially solve this problem, because there is almost no monetary cost for it. We propose to exploit opportunistic communications to facilitate information dissemination in the emerging Mobile Social Networks (MoSoNets) and thus reduce the amount of mobile data traffic. As a case study, we investigate the target-set selection problem for information delivery. In particular, we study how to select the target set with only k users, such that we can minimize the mobile data traffic over cellular networks. We propose three algorithms, called Greedy, Heuristic, and Random, for this problem and evaluate their performance through an extensive trace-driven simulation study. Our simulation results verify the efficiency of these algorithms for both synthetic and real-world mobility traces. For example, the Heuristic algorithm can offload mobile data traffic by up to 73.66 % for a real-world mobility trace. Moreover, to investigate the feasibility of opportunistic communications for mobile phones, we implement a proof-of-concept prototype, called Opp-Off, on Nokia N900 smartphones, which utilizes their Bluetooth interface for device/service discovery and content transfer. Index Terms Mobile data offloading, target-set selection, opportunistic communications, mobile social networks, implementation, trace-driven simulation. 2 I.

Abstract—In this paper, we propose E-Shadow, a distributed mobile phone-based local social networking system. E-Shadow has two main components: (1) Local profiles. They enable E-Shadow users to record and share their names, interests, and other information with fine-grained privacy controls. (2) Mobile phone based local social interaction tools. E-Shadow provides mobile phone software that enables rich social interactions. The software maps proximate users ’ local profiles to their human owners and enables user communication and content sharing. We have designed and implemented E-Shadow on mobile phones. In our E-Shadow system, we allow users to perform dynamic and layered information publishing, making use of interpersonal relevance. Our system also provides a mechanism to help users perform direction-driven localization of an E-Shadow and match it with its owner. Experiments on real world Windows Mobile phones and large-scale simulations show that our system disseminates information efficiently and helps receivers find the direction of a specific E-Shadow with accuracy. We believe our E-Shadow concept and system can lead to a more tightly-knit temporary community in one’s physical vicinity.