Managing wifi energy in smartphones by throttling network packets

Smartphone applications that access the network can quickly drain a phone’s energy. The WiFi radio consumes up to 25%-30% of the system’s total power, which could be twice as much as the CPU. The wireless radio supports two modes of operation, a high performance active mode and a low power mode. Determining when to transition between the two modes is particularly challenging since applications demonstrate diverse network behaviour. We show that even when actively using the network, applications provide short idle windows that can be exploited (tens of milliseconds). Current smartphones seek to exploit these windows by transitioning after a fixed timeout during an inactive period. Selecting the right timeout is challenging: If it is too long, the device may waste energy but if it is too short, it may significantly delay the incoming data (buffered at the access point). In this paper we attempt to answer the following questions: how difficult is it to configure the timeout that determines when the WiFi radio goes into the power-saving mode? Is there a time-out that works well for most applications? How significant are the effects on energy consumption and packet latency if the timeout is not configured optimally? How do we dynamically tune the PSM timeout based on the applications’ network activity? How do we modify the application traffic to maximize the WiFi radio sleep time without affecting the user experience?