4.5G

short for "fourth and a half generation", is the generation of mobile telecommunications technology between 4G and 5G (aka LTEe), succeeding 3G

4G

short for "fourth generation", is the fourth generation of mobile telecommunications technology (aka LTE), succeeding 3G

5G

short for "fifth generation", is the fifth generation of mobile telecommunications technology (aka "New Radio"), succeeding 4G

FDD

Frequency Division Duplex

FRU

Field Replaceable Unit