Many location-based applications such as geo-social networks rely on location services storing mobile object positions. To update positions on location servers, position update protocols are used. On the one hand, these protocols decide when an update has to be sent to ensure a certain quality of position information. On the other hand, they try to minimize the energy consumption of the mobile device by reducing communication to a minimum.

In this paper, we show how to improve the energy efficiency of different update protocols by taking the energy characteristics of the mobile network interface into account. In particular, we show that the energy consumption can be reduced on average by 70% using an opportunistic update strategy sending position updates together with messages of other applications. We present a Markov model to predict the arrival of messages and an online optimization algorithm calculating an optimized schedule to send position updates.