Customized multimedia content delivery has become one of the most desirable applications to mobile device users. However its intense usage of wireless and user interfaces poses a great challenge to device usability and battery lifetime. In this paper, we describe our design and implementation of an energy-efficient multimedia messaging system to address this challenge. We construct a hierarchical system for users to access multimedia content, leveraging widely available short message service (SMS), an embedded system-based new interfacing device, and the Internet capability of mobile devices. Being the first of its type, the new system not only reduces energy overhead but also improves the usability of the service.

The demand for an all-in-one phone with integrated personal information management and data access capabilities is beginning to accelerate. While personal digital assistants (PDAs) with built-in cellular, WiFi, and Voice-Over-IP technologies have the ability to serve these needs in a single package, the rate at which energy is consumed by PDA-based phones is very high. Thus, these devices can quickly drain their own batteries and become useless to their owner.In this paper, we introduce a technique to increase the battery lifetime of a PDA-based phone by reducing its idle power, the power a device consumes in a "standby" state. To reduce the idle power, we essentially shut down the device and its wireless network card when the device is not being used---the device is powered only when an incoming call is received. Using this technique, we can increase the battery lifetime by up to 115%.In this paper, we describe the design of our "wake-on-wireless" energy-saving strategy and the prototype device we implemented. To evaluate our technique, we compare it with alternative approaches. Our results show that our technique can provide a significant lifetime improvement over other technologies.