RX 301 mA (time 8:22,70) Figure 16.16 Example of current consumption for multiple services Smartphone Optimization Power consumption No DRX Long DRX Long and short Figure 16.17 Average power consumption savings with cDRX with multi-application profile 16.4 Smartphone Operating Systems Smartphone os has an impact on the amount of signalling that one device generates in the network. It not only controls how often the smartphone connects to different servers for basic services, but also may be able to control how installed applications behave towards the network. With factory default settings and just basic accounts configured most popular OSs only connect to servers sporadically, with a periodicity around 28 minutes or longer. However, when multiple applications are installed, the frequency of background activities increases with intervals as low as 10 minutes for optimized os with high control over background activities, and even lower for other OSs without strict control of background application activity. Figure 16.18 illustrates the background traffic activity with two different OSs. In the example illustrated in Figure 16.19, a smartphone creates two eRABs per hour due to the os without any applications. When some of the popular social media applications (App A, App B and App C) are running in the background, the signalling activity increases up to 16 eRABs per hour. These measurements clearly explain why we can see such a high frequency of eRABs also on the network level. 16.5 Messaging Applications There are quite a few Instant Messaging (IM) applications (APP) available for smartphones, with different levels of penetration, which include the possibility of sending and receiving text, video and audio messages. Most of these applications have in common that they include some kind of mechanism to determine the availability of the users while others rely on push mechanisms to deliver messages to users whenever they become connected. Besides users' preferences and usability, from a performance perspective there 