1G is short for 1stGeneration of systems for mobile communications. The 1st generation was analogue, datacommunication was not possible and the ability to use a mobile abroad was limited. There were a number of different systems in use which used a variety of frequency bands, channel widths and channel spacing.
In Europe, the 1st generation mobile telephony systems operated in the 450 MHz and 900 MHz frequency bands. The primary analogue standards were TACS (Total Access Control System) and NMT (Nordic Mobile Telephone). France, Germany, and Italy also used different national standards:
In the USA and Canada AMPS was the most widely available cellular system.
Japan made use of the NTT System 900 MHz and a Japanese version of TACS 900 MHz.