In-Building Cellular Enhancement System

An in-building cellular enhancement system, commonly implemented in conjunction with a distributed antenna system (DAS), is a telecommunications solution which is used to extend and distribute the cellular signal of a given mobile network operator (hereafter abbreviated as an MNO) within a building. In the United States, operators commonly supported by such solutions include AT&T Mobility, Verizon Wireless, Sprint Corporation, T-Mobile US, in addition to smaller regional carriers as required.

Source: Wikipedia — In-Building Cellular Enhancement System (CC BY-SA 4.0)