 have to periodically monitor the received power level of the SCell(s) causing an increase in the current consumption. Once configured, the SCells may be activated by the network, using an 'Activation/Deactivation MAC Control Element' based on proprietary activity thresholds. Once a SCell is activated, the UE should also start reporting channel state information needed for the packet scheduling. The CA feature impacts the smartphone battery life because UE has to monitor two frequen- cies, activate additional RF hardware and increase baseband activity. For large data transfers such as file download, the power consumption with CA increases during the time a file is downloaded. However, the higher throughput makes the download time shorter allowing the UE to go back to RRC Idle state sooner, thus increasing the energy efficiency and saving over- all battery life, as can be observed in Figure 16.9. The CA case provides the lowest average power consumption when calculated over the total period of 185 seconds including the active download and idle time. The instantaneous power consumption measurements for RRC-connected UE are shown in Figure 16.10. The measurements are done without any activity. The CA increases power consumption if it is configured or activated even if no data is transferred. The higher power consumption is explained by the UE monitoring two frequencies. Therefore, for short data transfers, where the RRC connection will spend most of the time waiting for the inactivity timer to expire, the power consumption may increase up to 80% when 10 MHz + 10 MHz CA is configured compared with a 10 MHz single carrier. This result indicates that CA should preferably be configured only when the transferred data volume is large but should not be configured for small background data transmissions. For more details, see Reference [2]. 16.3.2 Impact of Discontinuous Reception In principle, while a UE is in LTE RRC-connected state, it must continuously monitor the PDCCH for new downlink or uplink radio resource allocati