What is the difference between 5G NR FR1 and FR2 frequency ranges and their RF requirements?

What is the difference between 5G NR FR1 and FR2 frequency ranges and their RF requirements? 5G New Radio (NR) defines two frequency ranges with fundamentally different RF design challenges: (1) FR1 (410 MHz to 7.125 GHz): also called sub-7 GHz or sub-6 GHz (originally defined up to 6 GHz, extended to 7.125 GHz in Release 17). Key bands: n77 (3.3-4.2 GHz), n78 (3.3-3.8 GHz), n79 (4.4-5.0 GHz), n41 (2.496-2.69 GHz), n71 (617-652/663-698 MHz). Channel bandwidth: 5-100 MHz. Modulation: up to 256QAM. Duplexing: TDD and FDD. RF front end: conventional architecture (discrete PA, LNA, filters, switches). Power amplifier: LDMOS or GaN for base stations (20-40W per carrier), GaAs or CMOS for handsets (23-26 dBm). Antenna: conventional or massive MIMO (64T64R arrays at base station). (2) FR2 (24.25-52.6 GHz): commonly called millimeter wave (mmWave). Key bands: n257 (26.5-29.5 GHz), n258 (24.25-27.5 GHz), n260 (37-40 GHz), n261 (27.5-28.35 GHz). Channel bandwidth: 50-400 MHz (much wider than FR1). Modulation: up to 64QAM (lower than FR1 due to higher path loss and phase noise challenges at mmWave). Duplexing: TDD only (no FDD at mmWave). RF front end: integrated antenna-in-package (AiP) modules. Beamforming: analog or hybrid beamforming is mandatory (to overcome the high free-space path loss). Antenna: phased arrays with 64-256 elements per panel. EIRP: 55-65 dBm for base station, 23-43 dBm for UE. (3) Key RF differences: path loss: FR2 has 20-30 dB more free-space path loss than FR1 at the same range (FSPL increases as 20log(f)). This is compensated by high-gain beamforming antenna arrays. Penetration loss: FR2 signals are heavily attenuated by building materials (10-40 dB through glass, 20-50 dB through concrete). FR1 penetrates much better. PA technology: FR1 uses GaN (base station) and GaAs/CMOS (handset). FR2 uses SiGe BiCMOS or GaAs for the beamforming elements (lower power per element, 10-15 dBm, but many elements).