Transport protocol optimization for energy efficient wireless embedded systems

For wireless embedded systems, the power consumption in the network interface (radio) plays a dominant role in determining battery life. In this paper, we explore transport protocol optimizations for reducing the energy consumption of wireless LAN interfaces. Our work is based on the observation that, the transport protocol, which implements flow control to regulate the network traffic, plays a significant role in determining the workload of the network interface. Hence, by monitoring run-time parameters in the transport protocol, coarse-granularity idle periods, which present the best opportunities for network interface power reduction, can be accurately identified. We further show that, by tuning parameters in the protocol software implementation, we can shape the activity profile of the network interface, making it more energy efficient while remaining compliant to the TCP standard. We have performed extensive current measurements using an experimental testbed that consists of a Compaq iPAQ PDA with a Cisco Aironet wireless network adapter, to validate the proposed techniques. Our measurements indicate energy savings ranging from 28% to 69% compared to the use of state-of-the-art MAC layer power reduction techniques, with little or no impact on performance.