an the voice-related activity. Therefore, the radio network products need to be designed to support high signalling capability in addition to high throughput and high connectivity. Examples of LTE packet call setup volumes per subscriber per day are shown in Figure 16.4 from the network point of view. The frequent signalling creates also challenges for the terminal power consumption. 16.2.3 Mobility-Related Signalling The amount of mobility signalling has been a concern in the early days of LTE deployment because of flat architecture that makes mobility visible also to the core network. The practical network statistics, however, show that the number of call setups is typically 10 times higher than the handovers. There are two main reasons for this behaviour: the number of packet calls is very high and the packet calls are very short. A handover is unlikely to happen during a short packet call. The relative number of packet calls compared to handovers in three LTE networks is shown in Figure 16.5. We can conclude that the mobility signalling is not a problem in the current networks compared to the call setup signalling. If the cell size becomes considerably smaller in the future heterogeneous networks, the mobility signalling may increase. 16.2.4 User Connectivity The number of RRC-connected users is relevant for the radio network dimensioning. The share of LTE subscribers that are RRC connected can provide useful information to estimate the radio network requirements based on the amount of LTE subscribers. An example relationship between RRC-connected users and all LTE subscribers is shown in Figure 16.6. The share goes up to 10% in this example smartphone network during the busy hour in the evening, while the average value is 7-8% over 24-hour period. The share of connected users depends heavily on the RRC inactivity timer, which was 10 seconds in this particular network. The share can Smartphone Optimization Number of eRABs versus handovers Network 1 Network 2 Network 3 Figure 16.5 Relative number of packet cal