rs. If the technology development at a given moment in time is limited by the maximum possible frequency carrier width (which increases with the time), then the tool to increase it on the radio interface level is to aggregate different carriers below the network (i.e. IP) layer and then the aggregated spectrum (consisting of different car- riers, which may be located in different spectrum bands) can appear as a single pipe in a given cell from the networking and application point of view. So, the capacity in a given cell is directly related to the available spectrum and the possibility for aggregation of fre- quency carriers, and that directly influences the speeds available to end-users. Of course, the support of higher speeds is also dependent upon the capabilities of user equipment (smartphone, lap-top computer, etc.), which is ranged into categories. For example, in LTE-Advanced mobile networks, smartphone Category 6 supports up to 300 Mbit/s, Category 9 supports up to 450 Mbit/s, Category 12 supports up to 1024 Mbit/s, i.e. 1 Gbit/s, and Category 18 supports up to 1200 Mbit/s. Each new release of the lead- ing smartphone models on the market introduces a new category regarding achievable bitrates. So, even though the network will support Gbit/s speeds, a smartphone of Cat- egory 6 cannot achieve a speed above 300 Mbit/s. Additionally, mobile operators may limit (by certain configurations of the network nodes) the maximum speed that can be achieved by a certain user, which is a subject of network design and planning as well as product offers from operators to customers (via SLAs). Also, the spectrum in use at the base stations is required to be supported by the mobile terminals. Older mobile terminals have no support for recently added new frequency bands or new modulation schemes or new MIMO supported by the mobile operator's base stations. Therefore, every new mobile generation is gradually introduced into the market, first in the hotspot 5.8 Mobile Broadband Spectrum Management and QoS urban areas and then