Search

Multipath TCP is a backwards-compatible TCP extension that enables using multiple network paths between two end systems for a single TCP connection, increasing performance and reliability. It can also be used to "shift" active connections from one network path to another without breakage. This feature is especially attractive on mobile devices with multiple radio interfaces, because it can be used to continuously shift active connections to the most energy-efficient network path. This paper describes a novel method for deriving such a multipath scheduler using MPTCP that maximises energy savings. Based on energy models for the different radio interfaces as well as a continuously accumulated communication history of the device user, we compute schedulers for different applications by solving a Markov decision process offline. We evaluate these schedulers for a large number of random application models and selected realistic applications derived from measurements. Evaluations based on energy models for a mobile device with Wifi and 3G radio interfaces show that it performs comparably in terms of energy efficiency to a theoretically optimal omniscient oracle scheduler.

Modern mobile phones have the capability to detect proximity of other users and offer means to communicate and share data ad hoc with the people in the proximity. TWIN is an ad hoc social networking system which offers applications for social presence, mobile multimedia sharing and ad hoc community-based communication. In this paper we present the results of a large-scale user study of TWIN. In this field study, 250 study participants used TWIN for nine weeks. Our aim was to investigate the user experience of social proximity-based ad hoc communication. We found that the users felt TWIN to be more fun and entertaining than a useful tool for achieving pre-defined goals. Furthermore, users appreciated the possibility to find and chat with both familiar and unfamiliar persons nearby. Privacy concerns did not rise as a significant issue in user experience. We argue that a system like TWIN has the potential of becoming a new social enabler in people's everyday lives.