Crowdsourcing Available Parking and Available Storage Using

ii Smartphones have emerged as the most significant large-scale mobile platform in computing history. However, the scale of smartphone ex-perimentation has lagged behind. Keeping pace requires new facilities that enable experimentation at a scale large enough to ensure that re-search discoveries translate to the ever growing network of smartphone devices. In this dissertation, we introduce PhoneLab, a smartphone testbed that is open for public experimentation. To demonstrate the efficacy of PhoneLab, we present results from three research studies con-ducted on PhoneLab with the experiments that ran on participants phones. In the first study, we present results from a usage characterization experiment that ran on 115 phones for 21 days to demonstrate th