Prime: A Framework for Scaling Co-located Multi-Device Apps

Even though mobile devices are ubiquitous, the conceptually simple endeavor of using co-located devices for multi-user experiences is cumbersome. It may not even be possible when certain apps are not widely available. We introduce Prime, a thin-client framework for collocated multi-device apps (MDAs). It leverages well-established remote display protocols to enable spontaneous use of MDAs. One device acts as a host, executing the app on behalf of connected clients. The key challenges is dynamic scalability: providing high framerates, low latency and fairness across clients. Therefore, we have developed: an online scheduling algorithm that provides frame rate, latency and fairness guarantees; a modified 802.11 MAC protocol that provides low-latency and fairness; and an efficient video encoder pipeline that offers up to fourteen times higher framerates. We show that Prime can scale a host up to seven concurrent players for a commercially released open source action game, achieving touch-to-pixel latency below 100ms for all clients.