Optimizing power consumption of always-on applications based on timer alignment

In modern smartphones there exist several applications that periodically establish data connection and/or send data to the network. For example, a mobile email application periodically checks for incoming messages from the server. Packet transmission is usually triggered by expiration of a timer. Wireless radio access resources are activated during transmission, which increases energy consumption of the terminal, particularly when connected over 3G network. Fortunately, timing requirements are usually not strict and therefore application timers can be grouped together by using a timer alignment method. In this paper, we present two timer alignment methods for reduction of energy consumption. In the first both minimum and maximum thresholds of timers are available for alignment, and in the second only the maximum timer value is available. One of the methods was tested in the real environment by using Nokia N97 mobile phone in two different cellular networks. In addition, both methods were tested with a large number of randomly generated timers to find out certain statistical properties of their behavior. The tests presented very promising results, maximal power savings were ∼50%. However, the results depend on certain parameters of the cellular network.