Energy efficient data filtering and communication in mobile wireless computing

Battery power is a scarce resource in mobile wireless computers. We discuss energy-efficient software solutions for wireless information services and general data communication. Our approach is based on allowing the receiver to be shut off when no communication is taking place and letting the CPU be in an energy efficient doze mode as long as possible. Minimizing transmissions (which are much more energy consuming than receiving) from mobile hosts also leads to efficient use of battery power. We present two protocols based on this approach. The first protocol uses multicast addresses to filter out unwanted packets without waking up the CPU. Reusability of local addresses, similar to frequency reuse, facilitates using a limited multicast address space. The second protocol advocates a wake-up based scheme to save receiver power in a mobile host. We discuss the tradeoff between energy savings and increase in delay. Experiments with implementation of these two protocols show that a significant improvement in battery usage can be achieved, making a case for certain features to be provided in hardware.