ls compared to number of handovers be simply explained by the fact that smartphones create a packet call every 2 minutes (every 120 seconds) during busy hour. If the actual packet transmission is short, the typical length of the RRC connection is just slightly more than the inactivity timer, SO 10-15 seconds, which explains that 10% of subscribers are RRC connected. In general, a short inactivity timer of 10 seconds is preferred to minimize the smartphone power consumption and the number of connected users. On the other hand, a short inactivity timer leads to high number of packet calls. The share of RRC-connected users tends to be higher in USB dongle networks than in the smartphone networks. Also, if we look the mass events, the share of connected users can be higher. The USB dongle networks can have on average more than 10% of connected users and mass events even more than 20%. The share of RRC-connected users is clearly higher in HSPA networks since inactive users can stay in Cell_PCH for long periods of time, in the order of 30 minutes. In advanced HSPA networks, Cell_PCH users do not consume any base station resources and a very large number of Cell_PCH users can be supported Radio Network Controller (RNC). Cell_PCH state in HSPA is actually similar to idle state in LTE. Therefore, the number of packet calls (RABs) in Share of RRC-connected UEs Figure 16.6 Share of RRC-connected users out of all LTE subscribers LTE Small Cell Optimization Inactivity 30 min RAB setup Cell_PCH (connected) eRAB setup Cell_DCH Connected (connected) Data transmission Figure 16.7 Illustration of RRC states in HSPA and in LTE network HSPA is typically low since the setups only take place between the terminal and RNC while in LTE the setups take place between the terminal and packet core network. Cell_DCH users in HSPA can be considered similar to connected users in LTE. The number of Cell_DCH users in HSPA is normally less than 10% because the inactivity timer on Cell_DCH is usually shorter than LTE RRC inactivity timer. The RRC s