shows the ping latency measurements and Figure 16.14 shows the corresponding power consumption. There is a clear trade-off between low latency and optimized power consumption. Keeping OnDuration small and using mid-range DRX cycle (320-640 ms) seems to provide the best trade-off between latency and battery savings in this case. Ping latency with cDRX DRX cycle 160 ms 320 ms 640 ms 1280 ms 2560 ms DRX OnDuration (ms) Figure 16.13 Ping latency for different DRX cycles and OnDuration Smartphone Optimization Tail current consumption with cDRX DRX cycle 160 ms 320 ms 640 ms 1280 ms 2560 ms DRX OnDuration (ms) Figure 16.14 Tail current consumption for different DRX cycles and OnDuration DRX Impact on Standby Performance Usually smartphones spend most of the day in standby mode, which means that the end user is not actively interacting with the phone, but there is still activity going on in the background between the phone and remote servers, triggered either by the OS or by the installed applications. This continuous background activity is partially responsible for the general perception that modern smartphone's battery life is poor. Standby behaviour is normally characterized by small packet transfers which are repeated periodically, either to ensure that the service is still available (keep-alive) or to update infor- mation that will be presented to the user, like weather updates and messaging status updates. Using a simple model where background activity is represented as a short data transmission (3 seconds), followed by 10 seconds of RRC Inactivity Timer, and using as reference the 'tail current consumption" measured in Figure 16.14, it is possible to estimate how different frequency of background activity events per hour could impact the battery life of the UE. In Figure 16.15, standby battery life is estimated for a 2600 mAh battery considering differ- ent frequency of keep-alive messages per hour and different DRX cycle periodicity. Using a 320 ms DRX cycle in this case could increase standby battery life betwe