Sleep and Wakeup
In most mobile communication (e.g, LTE, WCDMA), Network configures UE to repeat a certain pattern of Wakeup-Sleep. This is mainly for reducing the energy consumption by mobile device. So how network sets the detailed configuration of this pattern and how efficiently UE implement those pattern become the critical factors in battery life of a mobile device.
In case of LTE, there are several cases in which these patterns happens. (Note : Measurement Gap is nothing to do with Wakeup/sleep but it also cause a 'break' in a technology, so I listed it in the same group).
Each of these cycles are relatively well investigated and defined and Idle mode DRX is being used in every network and some networks are using Connected mode DRX and SPS as well. But when all of these cycles are activated all togather, situation gets so complicated and it would take so long time to stabilize the combined operation not only on network side but also on UE side.