These notes outline how Fifth-Generation (5G) mobile systems were standardized, deployed, and evolved, and they summarize expected performance (key performance indicators, KPIs) across three International Mobile Telecommunications (IMT-2020) usage scenarios. They introduce 3GPP Release timelines and architectural options (NSA/SA), then highlights enabling technologies including New Radio (NR), new spectrum in FR1/FR2, massive multiple-input multiple-output (M-MIMO), a cloud-native 5G Core (5GC), network slicing, and edge computing. They then illustrate representative industrial and public-sector use cases. Finally, they sketch the path toward “5G Advanced” (Rel-18) and early 6G directions, including the EU Hexa-X / Hexa-X-II initiatives.
The evolution path distinguishes circuit-switched (CS) from packet-switched (PS) domains and introduces enhanced Mobile Broadband (eMBB), enhanced Machine Type Communication (eMTC), and ultra-Reliable and Low-Latency Communications (uRLLC) as service pillars. 5G usage goes beyond mobile broadband to three IMT-2020 scenarios: eMBB, massive Machine Type Communications (mMTC), and uRLLC.
The ITU-R M.2083 “IMT Vision” frames the KPI families (e.g., peak and user-experienced data rate, latency, connection density, spectrum/energy efficiency, area traffic capacity, and mobility) and stresses that 5G is not merely “doing better” than LTE.
For eMBB, targets include 10–20 Gbps peak rate, ~100 Mbps user-experienced data rate, and support for high mobility up to 500 km/h, alongside macro/small-cell deployments and very large traffic growth (~10 000×) with ~100× network-energy savings. mMTC emphasizes long-range coverage (MCL 164 dB), low data rates (1–100 kbps), ultra-low device cost, and ~10-year battery life, at very high device density (2×10^5–10^6 devices/km^2), enabled by NB-IoT and eMTC. uRLLC focuses on ultra-responsiveness (<1 ms air-interface, ~5 ms end-to-end latency), high availability/reliability (99.999%), low-to-medium data rates (≈50 kbps–10 Mbps), and support for high-speed mobility.
3GPP Release 15 (5G Phase 1) completed in December 2018 and primarily targeted eMBB and basic uRLLC, with a step-wise “drops” approach to cover all architecture options. The Early Drop (Dec 2017) standardized Non-Standalone (NSA) NR with EPC, where LTE eNB acts as master and NR gNB as slave for capacity “hotspots.” The Regular Drop (June 2018) added Standalone (SA) NR with 5GC, while the Late Drop (Mar 2019) completed remaining 5GC-connected options. Release 16 (by June 2020) targeted the IMT-2020 submission.
3GPP adopted OFDM with scalable numerology (subcarrier spacing, cyclic prefix) for both uplink and downlink up to at least 52.6 GHz. At the transmitter, windowing or filtering on top of CP-OFDM improves spectrum confinement (“filtered-OFDM”). An example 20 MHz channel indicates spectrum-use efficiency improvement from ~90% (4G) to ~98% (5G).
