With the growing popularity of 3G-powered devices and their serious energy consumption problem, there are strong demands on energy-efficient designs of 3G resource usages. Different fromthe pastwork in efficient-efficient real-time task scheduling, we explore the maximization of the amount of data transmitted by a 3G module under a given battery capacity. In particular, optimal algorithms are proposed to maximize the amount of data transmissions with and without a task for data receiving. The capability of the proposed algorithms are evaluated by a series of experiments, for which we have excellent results.