UMTS900 is the name for the deployment of the Universal Mobile Telecommunications System (UMTS) in the 900 MHz GSM band. This band ranges from 880-915 MHz (mobile transmit) paired with 925-960 MHz (base station transmit).
The main objectives of UMTS deployment in the 900 MHz band are twofold:
Both advantages come from the fact that the frequency is considerably lower than the frequency of the core band (2 GHz). These lower frequencies can travel further and will easier penetrate in buildings.