 offering the possibility to reserve certain radio resources (time slots) for a given mobile user terminal. Overall, the licensed spectrum on average gives higher QoS in mobile networks because the mobile operator can autonomously design, deploy, and optimize the mobile network. However, the very high price of the licensed spectrum (e.g. the new spectrum for 5G) may limit the amount which mobile operators are ready to invest in the network, which can result in less capacity for the given number of users and hence lower QoS, considering that the bitrates are one of the most important parameters for ultra- broadband Internet access via the mobile network. To provide device mobility and user mobility from one network and/or country to another requires harmonization of frequency bands around the globe. That is done by the ITU-R through its almost periodical World Radiocommunication Conferences (WRCs). For example, WRC 2012 set the initial bands for 4G and WRC 2015 completed the list of IMT bands to be used for 4G (as well as for previous IMT networks, such as 3G). In fact, IMT includes IMT-2000 (3G), IMT-Advanced (4G), and IMT-2020 (5G), hence IMT spectrum bands refer to all existing generations under the IMT umbrella. WRC 2019 will set the initial bands for 5G mobile networks. Using the same bands around the globe is crucial to ensure mobility through countries without the need to change end-user equipment, which increases QoE for mobile services. 5 QoS for Mobile Ultra-Broadband 5.9 Very Small Cell Deployments and Impact on QoS The 4G and 5G mobile networks have included small cells in their standards. But let's define what these are. Small cells are deployed by using low powered radio communi- cation equipment controlled by the mobile operator and typically have coverage in the range of tens or hundreds of meters (similar to WiFi coverage). However, there are dif- ferent classifications for small cells, in which some definitions include all cells smaller than macro cells (e.g. micro cells, metro cells, pico cells,