nd long cycle enables the usage of a shorter DRX inactivity timer and more frequent monitoring right after the last data is processed, while allowing for higher battery savings when new data takes longer to arrive. Figure 16.12 shows an example of UE current consumption monitoring for a short one packet transfer, where the power consumption during the inactivity period follows the preconfigured DRX pattern with 50 ms DRX inactivity timer, 80-ms-short DRX cycle and 320-ms-long DRX cycle. It is interesting to note how even if the 'OnDuration' is configured to 10 ms, the actual power consumption on each cycle may expand up to 50 ms due to the time the device requires to switch its radio components on and off. This is of course a factor which depends on the hardware implementation of the device and which is expected to improve with newer generation of chipsets. From a performance point of view, while having rather large long DRX cycles can be very beneficial for battery savings, it may also increment the latency experienced by users. LTE Small Cell Optimization 80 ms 320 ms On duration = 10 ms, actual power burst = 52 ms 50 ms DRX inactivity timer IrxShortCycleT = 4 7.976078 8.793 Figure 16.12 DRX impact on current consumption pattern Furthermore, in some cases it may also force the UE into uplink out of sync state, which means that the UE will have to obtain synchronization again using RACH channel before being able to transfer data in uplink direction. Choosing the optimal parameter settings for DRX is very important to minimize the current consumption while keeping delay under control and reduce the extra load generated on RACH channel. However, optimal settings also depend very much on the type of services that are used and the traffic pattern that they generate. The 'tail current' can be defined as the current consumption during the time while there is no data transmission but the RRC inactivity timer is running. We consider a simple traffic pattern consisting of small data transfers (i.e. 'ping'). Figure 16.13 