GSM from 3GPP). 2G was initially circuit-switched-based (CS), with the novelty of 5.1 Mobile Ultra-Broadband Network Architectures global roaming. The main services in 2G were mobile telephony (i.e. mobile voice) and short message service (SMS), while later 2.5G introduced the packet-switched (PS) network (e.g. GPRS from 3GPP) in parallel with the CS part (i.e. GSM). 3G. This was based on a 2.5G "hybrid" network approach, which included both the PS part (e.g. for Internet access and multimedia messaging service (MMS)) and the CS part (for voice and SMS), while the radio part in the most known 3G represen- tative (UMTS) was based on WCDMA (wideband code division multiple access) in combination with TDMA/FDMA. 4G. Appearing around the 2010s, 4G is noted as the first mobile generation which is all-IP by default in all network parts. The RAN is based on OFDMA (orthogonal frequency division multiple access), again combined with TDMA (which is required in mobile networks for QoS support). 5G. This is the mobile generation for the 2020s, which is all-IP by default (like 4G). It introduces higher data rates than its predecessor (which is standard with each new mobile generation) and additionally provides the standardized possibility for network virtualization (i.e. different network slices for different types of services). The radio part again is new, called New Radio (NR), which has been established practice (to have a novel radio access) in each of the mobile generations. The development of the mobile network architectures has direct influence on the QoS in the given mobile network. This is especially important in all-IP mobile networks such as 4G. Why? Because in CS mobile networks the end-to-end delay is typically limited with the propagation delay of signals which travel approximately at the speed of light (including radio, copper, and fiber transmission links), that is 3 X 108 ms-1, which pro- vides a delay of up to 100 ms between any two points on Earth connected with terrestrial connection (i.e. not through satel